Polar alignment and pointing issues with my PME

[Paul Haese]

Over the last couple of months I have been trying to sort out the pointing on my PME. With the help of Marcus I eventually decided to buy CCDsoft and augment it with The Sky6, Tpoint and Automapper II. Once I sorted a few minor settings I found that all this software works well together and actually performs the mapping quite well.

However several things have been concerning me.

First, I get quite a few errors with regard to either WSC not being used or pattern is not being recognised. Typically I am getting 48 errors for every 82 accepted on the plate solve. I am using 20 seconds per image and then auto dark subtraction. Do I need vary the gain, or is this to do with the number of stars in AutomapperII or something else completely?

Next, once I have completed a mapping run I am not able to get polar alignment really fantastic. I think it is good but not fantastic. See image below. For polar alignment I have done 5 runs with 20 map points per run. Then I did 2 at 30. Yet the previous run to this I was required to move 3 ticks in each axis. What am I doing wrong here? This polar alignment looks good but I have rejected 7 map points to get it looking like this at present. Two points were just terrible and obviously incorrectly mapped.

The of course is the final and most troubling problem. No matter what I do I just cannot get my RMS pointing accuracy below 100. I wonder if the pattern shown in the image is indicative of an orthagonality issue or something else? To be honest my pointing when I did a manual mapping run was near 100 and this is the best I can do with this data.

What I really need is some advise from guys in the know, I am really stuck (I normally can nut this sort of stuff out, but this time I just don't know what to do) and need help.

[Bassnut]

Well, im supprised you need 20secs per image to plate solve. I use 7 secs at bin 3 (lum filter) without a problem, with maybe 2 rejects per 40 images. If you get this failure rate with 20 images, thats 10 good solves, not good, look into that 1st (6 is the min for any result).

Does your map have a good spread across the sky?.

I use AAG Tpoint mapper (http://www.aagware.eu/) BTW (free), ive heard its more user friendly and it shows a picture of your scan map.

The Tpoint polar align data (and adjustment recommend) is always bang on for me.

[Paul Haese]

Thanks for the reply Fred.

to be honest I could use 7 second images, but each image looks so noisey from the 20 second that I just did not think it would help the plate solves. Next run I will give it a go. Yes the hit miss ratio is quite high. I am using the QSI as the imager and I would have thought it would be fine. Interestingly I have to use the TSA to image with as the GSO could not plate solve at all. I put this down to the notion that the scope is probably not an f8 as reported and this affects the scale all the time.

The map is spread all over the sky from 40 degrees up to 80.

I was going to use Tpoint Mapper and had it installed but I had to pay for Pin point for that system to operate (at least I think this is what is required). I don't think there is a problem with the operation of CCDsoft, The Sky6, Tpoint and AutomapperII. So given I just paid for CCDsoft I would not be keen to use Tpoint Mapper.

I am also wondering if my image scale is not 100% correct. I am using the flattener also and I think that affects the focal length by 2mm. I will need to look this up to find out for sure.

Do you think the fit model data looks odd Fred? What are your thoughts on the RMS figure? Un adjusted everything is way of to the right. I suspect it is time related. I am using internet update and that could well be a problem too. I would welcome your thoughts on that issue. The modelling I can live with, but not getting good pointing is bothering me.

edit. sorry the flattener makes it 800mm for the TSA and that means a significant difference. I will try that tomorrow night.

[Bassnut]

The fit data looks a typical shape, but over quite a large area.

Yes, image scale is important and should be correct. I didnt adjust that, AAG seemed to extract that automatically from the sky (or FITS image data)

If you update every 10 mins or so from yr internet time scource, that would be OK, it wouldnt trash the model.

Its worth paying IMO for pinpoint for several apps, DL uses it to plate solve and calibrate "point here" nudging. Apparently Sky X has its own built-in version. I understand though that the CCDsoft has a cut down version build in, so that should do (or is that DL, you can platesolve, so thats OK I guess).

I had similar problems until I increased the star mag sensitivity (in AAG) to 20 mag, more stars to measure with I guess.

You really need to get the plate sovle success rate up, that seems wrong, and may indicate a different rpoblem.

[rally]

Paul,

PA isnt bad just the scatter is a concern.
With that amount of scatter your PA result is in the noise zone anyway.
You will be going back and forth each time you do a new run !

The screen shot you provided lists that you have 11 terms in use.

I would think that is too many for that level of uncertainty and that small number of points, the extra terms will probably be doing more harm than good, but not that bad that the RMS be at 164 - ie to say its not the main cause.
Print out the Fit Information Dialog Box so we can see what they are and what they are doing.

Try removing all but the standard terms and get the polar alignment sorted out first before adding all extra terms.
You really only need just a few mapped points more than the bare minimum (6) to get PA pretty accurate - 10 should be more than enough for the first physical PA adjustment. 6-8 for a first PA should work.

RMS (164 arcsec) is high because the scatter is widely spread.
You need to think about the cause of this and fix it in order to get the RMS lower, its not going to go away by itself just because you have a Tpoint model.

The scatter diagram shows a definite North/South spread so its not across all axis - flexure in your imaging train maybe ?
Wind, vibration, backlash, (PE ? not sure) etc could all be possibilities.

Are these mapped points across both meridians ?
Try mapping just on one side and see if the scatter is more localised before doing the second side.

Are you deleting the old model after manually adjusting PA ? - Just a thought !

What is the orientation of your camera with respect to North/South and East/West ?

[Bassnut]

Paul. good that Rally chimed in, he seriously knows. Pester him till you get it right ;) :P :thumbsup:.

[Paul Haese]

Rally, I know about going back and forth, I have done this more often than not in the last couple of months.

The 11 terms actually are 5 extras, but each one makes it better. I think I started with 280 odd. I have read the instructions so give me credit here. 10% for each term or not at all. Right? Like you though I did ask the question about the RMS, I am trying to sort out what is going on there too.

Please see attached a copy of the dialogue box. Let me know if you can figure out what is going on.

I take your point about the points. I have done heaps of runs to get PA sorted but after 7 or 8 shortish runs I would have thought that PA is nailed? Don't you agree?

I agree that the Tpoint is not going to sort out things, but I was seeking an explanation as to why the RMS is so scattered. I knew it was odd but could not find any explanation over the net for this particular pattern.

I don't think it is flexure on the imaging train. You know what the Tak scopes are like, but I will check the screws holding the unit in place just in case. No wind, Clayton hardly ever has wind at night, lots during the day but not at night. Should not be vibration, you know the pier and I have fixed the connections with this adapter plate. Could be backlash, PEC not completely sorted yet. I bought Precision PEC to sort that. Tomorrow night I am going down again and I will do the PEC first, then work on PA.

Mapped points are scattered across the meridian but I reckon there was a lot more on the East side than the West. Maybe 15% on West. Not sure how to correct this as Automapper II does not seem to have an adjustment for that. I will take a look in the Sky6 and see if I can use a mapping model from that. If you have a suggestion here I would be interested.

Yes deleting old model after each adjustment.

Orientation to North is about 77 degrees according to WSC research. Good idea, I guess I need to shift that to North or near to it?

Appreciate the time you put into your reply but I have read pretty extensively on this and the instruction manuals can be a little thin. Suggestions are really appreciated. :)

Edit: sorry trying to put the fit info box up in text version

[frolinmod]

I'm under the impression that in addition to deleting the old Tpoint model after each adjustment, you also need to synchronize again (i.e., start from ground zero). I synchronize against an image link rather than a star.

Be sure to bin when auto mapping. It won't affect your accuracy. I bin 4x4 with a QSI-583 (on a C-14 @ f/11) and use 5 to 10 second exposures.

I'm using the latest TheSkyX with the Tpoint Add On. It works *much* better than TheSky6. For each 30 point run I get maybe one or two image link failures.

The Tpoint Add On supermodel feature works well, but requires lots of data to really truly shine (get down to 10 or so arc-seconds RMS) pointing. At least 150 points in my experience. But I never use more than 30 or so points per iteration when polar aligning.

If Tpoint polar alignment isn't working out for you, why don't you try using PEMPRO? PEMPRO has a drift alignment function function that many people swear by. PEMPRO also has a 60-day trial so that you can kick the tires before you buy.

[rally]

Paul,

Its pretty hard to sort out these problems with limited info and not being present to see how its occurring..
I can only suggest the obvious and the not so obvious - more info helps.

I note you have removed the CH term - Why did you remove one of the standard 6 geometric terms ?

I would add that term back in and remove TX to DNP in your list for starters and see if that improves anything.

The Fit Information indicates that TX is no good.
HCEC is possibly OK, DCES no good, DCEC no good, DAF & DNP definitely no good. Sigmas are much too high for their values.
This is all stuff you can follow through from the manual for adding new terms.
When you add the terms you also need to look at how they affect model and this needs to be done as you do it one by one - I can't tell from seeing it at the end of the run.
Best way to do this is create a spreadsheet and calculate out the values and see if they improve the result by enough to warrant inclusion - term by term.

The fact that you have two very distinct groups of clustered data points makes wonder if your camera has sagged either side of meridian, but I am not sure why that isnt reflected in TX
How does the camera attach to your OTA ?

Taks have focus tubes and if not adjusted tightly they can sag, the Tak CAA's always need tightening and adjustment to eliminate backlash, adapters can be loose in the threads due to faulty tolerancing in the threads or adjustment etc
The model shows something isnt right - so not much point saying it cant be this or that - try putting some finger pressure on your camera and see if you can detect any movement, I used a dial indicator on mine and was amazed at what I discovered

PA as I said isnt bad, and I am guessing it may be closer than Tpoint is reporting based on the model you have created.
But ME could be a lot better than 81.
How does it look on screen when viewed at say 400% - your monitor cross hairs should be touching each star.

But how good does it need to be ?
I guess it boils down to the question of what do you want to achieve - what limit do you set yourself ? - there are errors in the system because they are mechanical devices made by people ! so that has to be accepted.
If you are trying to get 0.0 arc secs - Its simply not possible.
So what is your acceptable value ?
If you set it too low you will be fighting the noise in your system and never be happy - Guiding and PEC will fix all of what you have got left there no problem at all !

Fred - Thanks mate - pester me till its right :(
I am no expert on this.

[Paul Haese]

Thanks Ernie,

Yes been synchonizing with a start before the model is started. Not done that with a image link every time though. Might try that.

I was binning at 3x3 but read in one of the manuals that 1x1 was most accurate. So I compromised and tried 2x2 and found accuracy went up a little from 3x3. Might just be an errant thing though.

I don't really want to buy SkyX if I can avoid it really, but will if I absolutely have to do so.

Can't use Pempro as I have already gone past the 60 days and would have to buy yet another piece of software. I had trouble getting it to talk to all my gear too on Vista.

Some things to think about and I will try 4x4 with 5-10 second images. Second person to recommend this so definitely seems the go.

[Paul Haese]

Rally, sorry was really cranky last night after spending several weeks just doing all the reading and trying to get this working well but things were defeating me a little. I am really happy all the system works under Vista but getting better results is the issue for me.

I tried changing the 6 main terms to see what effect it had. So I am with you there, this produced the best pointing effect. I agree not necessarily the best result either.

Yes looking through the fits file again last night and having read Brad Moores recommendations of sigma being less than half of the value. No matter what I do here the issue is not the model itself at present it is the way the data is gathered. Until that gets good results then the model manipulation is really a moot point.

The camera is attached using the standard Tak tension screws (yes it should have a screw in adapter but I have the flattener in place for both the tak and the RC and there is no screw thread on the flattener just an inserted end to the focusor) and could well as you point out be causing the problem. I will check this out tonight and use your suggestion of using some pressure to determine if there is some flex. I did this for eliminating flexure before when I was getting bad differential flexure so I know what you are suggesting here. It had not occurred to me that this might be an issue. Good tip this one. I will check it out.

PA results seem fairly easy to manipulate though. Removing a couple of stars can affect the model and suggest good PA. I am going to check with my own eyes tonight and see what drift I am getting. I take your point though about the ME. It ought to be a lot better than that for such PA.

How good does it need to be. Hey I would be happy with 50-70 RMS pointing. 40 would be great as far as I am concerned but 50 is realistic I think. That would put me near the center of the sensor each time. as 125 was putting me on the edge when I did this all by manual. I then simply nudged to get it center. I just want better point than I did have. Certainly have no illusions that this mount could be anything near the value you suggested.:) Yes the guiding and PEC do sort this but it is the pointing I am after.

Thanks again for your help.

[rally]

Paul,

Tpoint will help you identify physical/mechanical errors - use that info to physically fix these errors rather than try to use it to correct them in software.

Flexure and sagging with single screw or compression fittings and nose pieces is erratic - is doesnt shift at all until you get to a certain point and then it just goes (or not), as opposed to the more linear sort of bend with tube or bracket flexure.
Tpoint cant fix that sort of problem.

I am surprised you are using this sort of fitting in your rig and at the same time expecting precision results in the arc second level. Its a waste of time.

I thought all Tak flatteners had screw threads at each end ?

I am sure that you will be able to visibly see the camera moving with a light finger touch - try say 1/2kg equivalent of force - it will only be a small amount of movement but I feel sure it will be there. It may not be the same in all directions depending on where the screws are.

So you have multiple points for potential flexure
The Focusser, the CAA rotator (both should be able to be adjusted out with that lightweight camera), the 2" screw down adapter, the flattener itself maybe, and whatever method is used to attach to the camera itself

RTM
Read the Tpoint manual and follow it - its your best guide for using Tpoint - its states the same as you have mentioned ie 2x Sigma plus a lot of other stuff that needs to be followed if you want to add multiple extra terms.
TheSkyX will help you automate the extra terms much better.
Otherwise dont bother with them - if the system is stable and the PA good - its going to be well within your desired range.
You are much more likely to get yourself into deeper trouble if you dont understand what you are doing with Tpoint terms.

Rally

[Paul Haese]

Point taken and I suspected this might actually be part of the problem or it solely. I will need to get either a new focusor or a screw fixing adapter for the Tak focusor. The flattener for the TOA/TSA series is a slide in version. I do have a reducer though and might get the adapter made up for it to the Camera by Precise Parts. I had one made for the flattener to camera. However this is most likely the problem.

I will re read all the manuals again with particular emphasis on the Tpoint one.

Once I get this nutted I will report back what the problem was. It might help someone else down the track.

[frolinmod]

Paul, if you haven't already done so, then please go to the www.bisque.com (http://www.bisque.com) website, register as a user and post concerning the problem in either the Paramount ME or the Tpoint for Windows support forums. They'll want to see your Tpoint model. Patrick Wallace (Mr Tpoint god himself) frequents the site. Software Bisque has quite a good support forum.

[Paul Haese]

Thanks Ernie. I am a member there and will do as you suggest.

[gary]

Hi Paul,

Had a look at your FIT text file.

It's just all noise. There is something random going on. And not random
in a systematic way, like non-orthogonality. Random as in throw the dice random.
However, the good news is that the results are telling us that, so it is still good information.

Adding additional terms won't help at this stage.
Could you please show the results from the following fit commands? (i.e. the fits text files including as you did before).

1) ID & IH only
2) ID, IH, MA, ME only
3) ID, IH, MA, ME, NP & CH only

Could you please also supply the scatter diagram that results from each of the above fits.

Knowing the results from the above might be able to tell me more.
However it could well be a case of 'garbage in, garbage out'.
For example, few things will throw out the results more than incorrectly identified/mapped stars.

What would also be useful is if you could do a File Text Export command and post the text file.

Based on the FIT text file you have already posted, the fact that the sigmas
are nearly as large as their corresponding terms tells me that it is noise.
The MA and ME terms are also giveaways.
These two terms have very distinctive mathematical signatures and are thus
normally not strongly correlated to other terms. But they too show that
something random is likely to be occurring.

Best Regards

Gary Kopff
Mt Kuring-Gai

[Paul Haese]

Thanks Gary, I will try to get those requests sorted.

As to random looking data. I now think you are right.

Last night I did a drift polar alignment and it was out, drifting in just 2 minutes. So I drift aligned until it was 20 minutes on each axis. No more stuffing around with that. I will not be trusting Tpoint until I get the pointing issue sorted.

Then I checked for flex as Rally suggested. Non on the telescope, connection to mount or camera connection to the scope. All really rigid. I am really satisfied that this is ok too.

Next I took out the flattener and just tried mapping with the camera and scope at native focal length. Same results. North South separation and then something occurred to me.

On my mount if I stand with the RA pointed towards me and I gently grab the counter weight bar there is noticable slop in the RA axis (I am talking 10mm here; up and down perpendicular to the axis); so if you are holding the bar and the scope is say laying over in RA I can move the bar up and down by 10 mm. My camera is set up so that long axis of the sensor is perpendicular to the Dec axis. That should make the north at almost 90 to the RA. Would this slop account for the north south separation? When I took the face plate off some time ago I noted that the whole worm and gear move as one and that the assembly does not appear to be bolted to the body fo the mount, it sort of floats. Is this normal? I would have thought that this sort of slop would prevent good pointing. I think this is most likely the cause of the problem.

Gary, the odd thing is that many images are ok on the astrometric solution in CCDsoft but they get rejected in the sky or Tpoint (not sure which is rejecting, but I get the message in automapper that it has been rejected.. I get two main errors; insert WSC failure and cannot map. Last night I got 140 errors and 93 positives on one run. That means there is something really wrong physcially. Often the circled star in CCDsoft (the star being pointed toward) is all over the place. Sometimes near the cross hairs, but most often at random distances and places from the cross hairs. I think it might well be the mount work that was done before I bought it that is causing the problem.

Hope that makes sense.

[wysiwyg]

Paul,

Having read the posts, it definitely sounds like you have one or several mechanical issues to resolve. This could be slop in the mount as you mentioned, it could also be your adapters. Even the most rigid adapters have some degree of movement, its a matter of minimising it as you cannot remove it all.

In my opinion there is not much point doing 100+ tpoint runs until you have sorted the mechanical issues out first. Tpoint will not eliminate these for you alone.
When you are at the stage where you have minimised as many mechanical flaws as possible then go for it!
Adding terms is also not recommended until you have a substantial Tpoint model of about 200-300 points, remember this model is statistical, so adding or removing the wrong terms can be disastrous.

If you are using the tutorial, create yourself a spreadsheet and take the time in doing it. My first serious model with added terms took me a good 3 hours, and that was just doing the calculations and methodically checking the results. Remember that if you add a term and it has positive results it is likely that it has an adverse effect on another term and this is only apparent if you do the math in the spreadsheet.

Lastly, I personally had an 80% plate solve failure rate with CCDSoft and TheSky6 and it did not take me long to realise PinPoint was the only way to go. Now I have a 99% success rate in plate solving.

Good luck Paul!

Cheers
Mark

[Paul Haese]

Good news.

Brad Moore has come to the rescue and like me thinks there is a hardware problem. I have to do some investigation inside the mount. A PDF is on its way to me (incidently this is how software bisque fixes mount hardware problems - you get a comprehensive instruction on how to fix the problem and you fix it yourself. I like this because I will sort the problem) to check and tension bearings and fixings. I will have to take some video of the problem and send it off to Brad.

So I will get back to you all very soon and let you know how it works out.

[Bassnut]

Gaud, thats shocking. How hard do you do up the locking screw?.
I left it loose once, what a mess, now everything you describe makes sense.






Its not loose........................ right? :scared3:

[Paul Haese]

:rofl:

No Fred not loose and not too tight, just as the instruction manual states. Now you see what I am going through. Wysi just confirmed his mount has zero play in it too. So now to fix this problem.

[Bassnut]

OK, well Brad Moore is paid to know and your last chance, he knows PME better than SB. Other than that just kill yourself, itll be less painfull, cheaper and faster.

Or.........strip it down and learn yourself (that slop must be the problem).

[gregbradley]

Hi Paul,

I just started following this thread. I went out to my observatory just then to test my counterweight shaft to see how much slop it has. It has none. It flexes slightly under a push but it is firm right from the start with no noticeable slop. So if yours has 10mm slop then something is wrong and your T-point model is detecting that.

As far as the mapping process itself. I used an ML8300 camera with 1 second download times at 2x2 binning, no subframe, and 10 second exposures. I got about 99% success rate and one map took 20 seconds to do from slew to finish. 200 points took about 45 minutes.

I could not get it to work until I added the USNO A2.0 database of stars that Marcus gave me a copy of. Once I added that to the database and let the Sky 6 know the location of the file it worked like a charm.

Use new astronomy press CCD calculator (its free) to calculate your
arcsec/pixel. As an example my ML8300 on the CDK17 at 2959mm focal length gives .38 arcsecs/pixel. It has 5.4um sized pixels. As you realised flatteners aren't all neutral to focal length. You'd have to get a factor for your flattener or as you did not use it. Also north angle has to be very accurate for it to work. Mine was around 2.33.

If the point of the exercise is accurate polar alignment then Pempro does have a wonderful polar aligment wizard. I used it once (I missed the last step) and later did the 200 point model and I was only a little bit off.

I check the autoguiding errors to make sure the theoretical produces practical observable gains otherwise what is the point. In my case the very adjustments did make a gain. Although I was surprised to see go-tos were not spot on. Anyway, accurate polar alignment and adequate go-tos was what I was after not necessarily object dead centre every slew. I frame anyway so I just don't want to spend time searching for the object.

So my conclusion is Pempro polar alignment wizard will get you to within a hair of precise PA and a proper T-point model will get you that last tiny bit.

By the way with a 200 point model started from scratch and synched to the first star manually got me 28.5RMS on the CDK17. Most of the points are grouped within a 50 arc sec circle. I deleted perhaps 4 or 5 outliers out of 205 points that left me with 200 accurate points.

As I say the USNO database made the difference for me. Thanks Marcus!

I just did the calculations:

TSA102 816mm focal length 102mm aperture F8.01 KAF8300 chip 5.4um pixels 3326 x 2504 1.36 arcseconds/pixel
with flattener focal length is 800mm F7.84 = 1.39 arcseconds/pixel.

Link to Kodak Sensor solutions website for KAF8300 specifications: http://www.kodak.com/global/en/business/ISS/Products/Fullframe/index.jhtml?pq-path=14425

Link to TSA102 Specifications:
http://www.buytelescopes.com/Products/10529-Takahashi-tsa-102s-102mm-apo-refractor.aspx

Link to CCDcalc free download:
http://new-astronomy-ccdcalc.software.informer.com/

I hope the above helps.

Greg.

[rally]

Paul,

Glad to hear you have found a major source of your pointing problems.

I certainly didn't expect you to find such a big backlash problem in your PME's RA axis !

Hopefully its something simple that can be adjusted out.

Rally

[gary]

Hi Paul,

Good find and it may turn out to be the culprit.



It certainly would be a good question to put forward to Bisque.
However I see in the thread another owner is kindly coming to the rescue with a PDF of the mechanicals.



Sounds as if the pointing is sufficiently out that the automapper is failing.

It would be instructive to even manually slew to 6 bright stars you know on
either side of the meridian and sample them and see what the RMS is for just
ID, IH, ME & MA. With the amount of slop you mention in RA, I think we
can anticipate that the RMS will be high and the value/sigma ratios still
very low.

So the next port of call will be to confirm with Bisque or another ME owner (Brad?)
as to how it really should be inside the mount physically with regards the RA
axis. Or as Fred mentioned, you might be able to figure it out for yourself with the aid of the drawings.

Once you nail that, I'd say you will be a long way along the path to dramatically improving your pointing performance.
Certainly TPOINT is all you will ever need to clean-up anything systematic remaining, including the polar alignment.
The plate solve will then find a lots of its work done for it already. :)

Good luck!

Best Regards

Gary

[marc4darkskies]

I missed this thread somehow!

Certainly 10mm of slop in RA would explain the poor model!!! And it's a very poor model for a PME! Hopefully this is just a spring plunger adjustment on RA. BTW, sigma values in a good model should all be under 10. Sigma for the MA and ME terms should be less than 5 or so to use them reliably to set polar alignment. Usually the only way of doing this is to add harmonic terms until your RMS and PSD stops improving (or improves less than 10%).

Cheers, Marcus

[Paul Haese]

Thanks guys much appreciated.

Greg, I got the same figure for calculation. Although I have read in one of the manuals that anywhere around 0.25 of the correct scale will be find for astrometic calculations.

I also got the USNO A2.0 database from Marcus too :thumbsup:. I did read on another forum though that greater success rates for plate solving are gained when only one data base is selected. Incidently did you select it by Data/file locations/data applications/core data bases and then in stellar options? Then saving the settings?

I honestly cannot see how I could get my PA any better now though after doing it myself with drift alignment. 20 minutes per star and nill movement is pretty good but I stand to be corrected if you think I can get better than that.:)

Gary, I will probably do the six star model once I get this adjustment sorted out. Thanks for the suggestions.

Marcus, I think it might be either the spring plunger or the locking bolt located up in the top of the mount. I need to remove the side plates (fortunately I removed the 6 little allen screws on those plates for future access so my PA will not be affected) and take a good look around. Brad is going to organise what adjustments will be need via PDF once I figure out where the problem really lies. There is a PDF on my way for checking of the RA slop to ensure the bearings are in correct tension. I have access via a mate here to any type of tension wrenches or vernier gauges that I should need. Spent plenty of time rebuilding motors in my petrol head days so I know all about tight tolerances. Having already taken a good look around inside one of these mounts they look pretty simplistic and yet have such good performance.

One this is for sure I will report back what is up with the mount and how it got fixed. It might be instructive to others to know how to fix similar problems.

[Paul Haese]

UPDATE

I have definitely found the source of the problem and I hope I have fixed it too. On the advice of Brad I went and investigated the mount today. I have opened this mount before and am very familiar with most of it. I began my making a video of the slap (see below) It shows the slap in the mount and RA. This does not happen on other mounts.

Click here (http://www.youtube.com/watch?v=cZXNp1D3S50)for Video of RA slap.

I then removed the side panels to see if I could find the source. I had thought I could avoid disturbing the PA I got the other night but this was not to be. The side covers I had previously removed the bottom screws on the panels which means you don't normally disturb your polar alignment. Unfortunately to get the grub screws which hold the RA worm assembly in place you need to remove the very bottom narrow plates. This means I had to jack up the altitude all the way. I got the grub screws to discover that each one on each side was quite loose with the locking screws being loose too. I used an allen key to tighten up the grub screws on each side at an equal depth on each side until it was just snug or just finger tight (I figure that finger tight is the correct tension; too tight and the thrust bearings inside the assembly could be damaged). Making it dead center too prevents the worm from being one end or the other when it meshes with the drive gear. Contrary to some opinion the entire worm assembly was shipped to Brad and so any angle adjustment of the worm to the gear is not necessary as the unit bolts staight on and swivels up and down. It cannot be placed at an angle at all. So here is the video of the grub screws in question.

Click here (http://www.youtube.com/watch?v=9pcod-Lb8aU)to view the video of the mount stripped.


Once I got it all back together I connected the mount to the computer and just tested to see if the mount was sound and all the motors and gears ran correctly. The video speaks for itself.

Click here (http://www.youtube.com/watch?v=rQRf3NBsQ1A)for PME after adjustment.

So finally here is a video of the mount now showing no slap when in the park position. Just so you can see how the adjustment affected the slap.

Click here (http://www.youtube.com/watch?v=oQnWTrXku5g)for PME in park position with no slap.

I will be talking directly to Daniel from Software Bisque and seeking advice about tension required. I suspect my finger tight will be just fine and I will not be required to do further adjustments. Hopefully the pointing will be out of sight now. It is going to be cloudy and raining now for a week so I will post my next mapping run when I can see the sky again. Failing any need to do further adjustment to the grub screws.

I am a firm believer in sorting things out yourself. I now have a greater understanding of the mount and it reminds me of my first RA drive in the way the worm was engaged.

[marc4darkskies]

That's great news Paul - you must be relieved! That's one of the selling points of the PME isn't it - nothing is hidden from view. You have the peace of mind knowing you can can get inside to see what's going on and, more often than not, fix stuff yourself (with guidance from SB of course)!

Cheers, Marcus

[gary]

Hi Paul,

Good stuff.

The "before" and "after" videos say it all. Hopefully your next pointing
run will deliver the goods.

Best Regards

Gary

[gregbradley]

Nicely discovered and resolved. That should be the end of your troubles.

20 minute no drift polar alignment is something that is practically impossible to achieve with any other mount so that was pretty spectacular.

I am sure you will get super results now.

Greg.

[Ken Crawford]

Paul,

I am very happy and releaved that you have done such good work finding out the problem and the solution. I am so sorry you went through so much on this problem and I want to publicly apologize to you as it was my mount that was sold to you. I believed it was in like-new condition when you recieved it and paid good money so it would be that way. I am saddened to find out that this happened and it is one of the real issues of being thousands of miles away from your eqipment.

The good news is once the problem was found you were able to fix it and you know more about your mount than most people do. I believe you will be able to get a fine T-point model and great pointing and guiding.


On Another note - I spent allot of time cleaning my equipment I just recieved back from Moorook. There is lots of brown fine dust in everything including my rack-pinion gearing on my AP130. So, I would yearly re-grease the worms just to make sure they are free of the fine grit. This stuff was everywhere . . .

Kindest Regards,


Kindest Regards,

Ken Crawford

[Paul Haese]

Thanks Ken, yes I did a big clean when I got the mount. Don't get me wrong it had already had a good clean but I am a little more keen to have a really clean mount. Inside the mount was fine, no bull dust there, just only on the surface. The dust was the result of a couple of large dust storms a couple of years ago, one of which was recorded here is you are interested in doing a search. It covered a lot of NSW and Eastern South Australia.

Anyway, I have to wait to find out the results now. Cloud and rain predicted for next week.

[Paul Haese]

Update

Just thought I was give an update to the issues with the mount. Using automapper II and using the map current function I got my six stars for PA to a pointing average of 5.9 arc seconds and PA close enough to what I wanted.

Next I ran let automapper II make a list of stars of the entire sky and then let it go. I found that my error rate had gone down from 150% rate to 50%. I was still getting quite a few outliners (nearly 40 of them) but finally got my pointing down to with 150 odd points out of 195. See the scatter diagram below.

I think the software has some problems or I am still doing something wrong to get such high error rates, but for now I just want to get on with imaging again. If the sky ever clears.

I do think though that the dec worm block needs some adjustment too. There is a little slop in that too, and that was not changed but probably considering it had such a large scope sitting on it, maybe it needs some service work. I will be sorting a few things out to get this mount working really well but it seems for now I have sorted the main problems.

If you think there is something I am missing or have any final tips please let me know. I am all ears when it comes to this. I have read every manual inside and out and think that I have got it sorted.

One thing that bothers me is that when I do research in CCD and it does not insert the camera angle I cannot get the image to link and that makes for problems trying to sink that first star. Is it easier to just find a bright star and take that image at the center and sinc that rather than just pointing it at a constellation?

[gregbradley]

I have been running Tpoint and Automapper II the last 2 nights on the CDK.

Your final result there is similar to what I got tonight. Mine went as low as RMS 17 with 102 points mapped. I did several runs each time I adjusted the Polar Alignment after fitting the data and getting rid of outliers. It took 9 terms to get there. I simply used the suggest terms button and accepted it and watched the RMS number. I ran about 50 to 100 points in a run and then adjusted the PA then slewed to a bright known star, centred it, deleted the T-point model, then started a new one, then synched the star then started the new mapping run after mappung the current position (I don't think that is required for a run though).

As far as 6 points for PA I would think that is highly inadequate. Even just fitting the data and getting rid of outliers you see the suggestions for the PA adjustment change.

I have used 2 cameras now. The FLI ML8300 which is similar to your camera and the PL16803. The ML8300 I used 10 second exposures at 2x2. I added the USNO catalague from Marcus to my database in the Sky.

With the PL16803 I use 3x3 and 10 second exposures and it works well and usually gets more stars. Both are fast as the FLI's have super fast downloads of 1 sec or less. So total time is about 19 seconds per mapping including slewing time. So a 100 point model only take 40 minutes or less.

I found I had to take an image in CCDsoft then insert WCS research and it plate solves and gives the north angle. I then added that into the automapper default settings. Then it plate solved. It would fail without that north angle. Its done that twice now where it would not get the north angle when you press the get button next to north angle. So if you are not doing that try getting it through CCDSoft. I take it you have CCDsoft server settings turned on per the manual.

The only failures I got were because of cloud. Its probably a bit harder to do with a full moon. Perhaps that was all it was.

I have done 3 iterations in 2 nights and tweaked the polar alignment each time. Make sure you are turning the dec knob the right way.

I also check how its going by doing a bit of autoguiding and watching the errors and seeing if they are in fact lower than before. They have been so far.

Greg.

[Paul Haese]

The manual seems to indicate that 6 points is enough for getting PA. Several other people have indicated that too. With just the basic terms I have got it quite close. And; the final PA results are very similar to the 6 points results. Still 89 seconds away from the poll though in the alt and 7 seconds in azimuth.

I hardly ever get a plate solve in CCDsoft under insert WSC. Sometimes I might jag it and it gets the north angle, but most times it just will not play. I suspect this is part of the problem really. I set all the parameters correct, although on my version of the sky and CCDsoft some of the things that need checking are not present. It all seems to talk to each other though, which is weird. Everything is running in administrator mode. I will try this for now and see what happens. Maybe it is worth getting skyX and the new Tpoint version. I have heard this plate solves better anyway.

[gregbradley]

I checked the manuals and the 6 point mentioned in the manual is just to get the scope pointing closer to the object so you can find things.

If your PA is accurate with 6 then that is good. But per the manual and the T-Point workflow pdf it recommends a few hundred points for permanent installations.

Only once you have added terms and gotten the sigmas and the RMS down is the PA recommendation considered valid. This is all from the T-point workflow PDF.

That has been my experience with it. Recommendations on few points were inconsistent and did not always improve the PA I already had from drift alignment.

I have just done several iterations of models and after model fitting I got 0.0 recommendation on the elevation and .7 tick adjustment on the dec.

But thats 3 models, 1st one about 100 points, second one about 38 third one 102 points.

None of this of course is the problem here.

When you try to plate solve what error message is showing? When mine failed it was initially because of incorrect north angle.

When you zoom in on a starfield in Sky 6 do you see all those USNO stars showing up? Do you have the check box ticked in the display explorer for the USNO database? I take it your CCDsoft has the server settings set properly and you have both a CCDsoft box saying listening to port as well as one in the Sky 6? You need both going. Did you set the file location of this database in the Sky so the Sky can find the USNO database?

What operating system are you using and do you have enough RAM?

I doubt getting the later software will change anything as it should be working already. Something is off. Odd it works half the time. What exposure setting are you using? Are you binning? I take it you entered the correct arc/second/pixel for your camera/scope unbinned?

I used 10 seconds and 2x2 binning for my FLI ML8300. It worked well.
What scope are you using? If a TSA102 you may need to do 30 second exposures and use subframes. I say that because it needs to see lots of stars. I am using the CDK17 and of course 17 inches gets a bright image in no time.

It sounds like your mount is now working nicely and it is a software problem or something not checked that needs it in the various settings.

Greg.

[Paul Haese]

Thanks Greg. Error messages in CCDsoft are north angle failed or image link failed check co-ordinates and image scale. I just checked on two images of stars one worked and the other did not.


Zooming in I cannot determine which stars are in the USNO catelogue. How do you do that?


If you are referring to having it ticked in stellar options under astromety, then yes. In the data/file locations it is not in bold like the other catelogues but when I use verify it comes up with a tick (is it supposed to be bold like the other catelogues?).


Both CCDsoft and the sky have ports listening and I think I have all the settings correct. Both have checked allow remote connections, both have remote clients use orchestrate or RASCOM, then the other settings needed for each.


Not sure, I verified under file locations but like I said it is not in bold now like the other catelogues but it does verify with a tick.


I am using Vista with 4 gig of RAM


I am exposing for 7 seconds at 3x3 bin. I used Rod Wodaskis CCD calculator and got 1.39" with the TSA/flattener and KAF8300. The TSA native has 816mm but with flattener it is 800mm that combined with KAF8300 should have 1.39" per pixel.



TSA with flattener. I seem to be getting plenty of star but I will try say 20 seconds to see if that works.

Just out of interest, once I do get a plate solve in CCDsoft, do I then go directly to the sky and sync and then map it. Even if it is not in the center of the field (the star I am aiming at)? This seems to be my reading of the instructions. Does it matter if the star is not dead center of the cross hairs in CCDsoft?

Just testing I found that if the image does not plate solve in CCDsoft. I have to then completely close down both the sky and CCDsoft to get it to plate solve on a known star. Odd really. Could be a Vista problem.

Thanks guys for your help, much appreciated.

[gregbradley]

I think we are narrowing it down here.

I installed the USNOA2.0 database that Marcus gave me.

You have to tell the Sky 6 where that file is.

You do that by:

Data
File Location
Core Databases
USNO A2.0

Then you put in the location of where you saved the USNO A2.0 database.

I am not sure if this next step is totally necessary or if it just simply shows it is all available for the Sky 6 to compute with.

Display Explorer
Core Databases
Stellar
USNO A2.0 check that box.

Now when you zoom in on a starfield after several zooms in you will see lots and lots of labels for the stars in that USNO A2.0 database.

Now you know they can be used by the Sky 6 when doing a plate solve.

Marcus told me it would not work well without that database.

It sounds like your may not be setup properly and hence the failures.

I find just doing a map current position fails on that same error message.

So I take an image in CCDSoft, I save it then I do insert WCS research. It plate solves it every time and comes up with the North Angle.

I then put that north angle in automapper 11 along with the other details and it all works every time unless some cloud interferes with the image.

As I say I use 10 seconds 2x2 with the ML8300 and 10 seconds 3x3 with the PL16803.

Greg.

[Paul Haese]

Well I give up.

Just to let you know. I used one image several times in a row today and tried to get a plate solve. It would do it if:

The view in the sky was near to the stated image scale. It will not plate solve if the view is not near the employed image scale. That is just weird.

By way of example, if I used the USNO catalogue the calculated scale each time would reduce and plate solve more stars. See images. If I used the UCAC2 catalogue the reverse would happen. That is; the scale would continue to increase and the view would take in more skies and plate solve less stars.

I really don't know what to do now. I cannot get this software to work for me and I don't want to buy more software so I can run AAGautomapper. I would need to buy maxim and pinpoint. I have read and read the manuals and I cannot seem to get this right. This is no doubt why I get so many errors in the plate solves. I am tempted to ask Software Bisque for my money back and forget the whole thing. So fed up with this software.

What do I do now???

I know the USNO stars are there as I did not have the fainter star option bright enough. Got that sorted.

[Paul Haese]

Thanks Greg, I tried zooming in but did not get the labels. I have no idea, what is wrong here.

[gregbradley]

The display explorer needs to have the stellar database checked on for the labels to display.

Could it be an issue with Vista? I found it sabotaged most of my astro software and I do not use it. Windows 7 seems more sorted and user friendly.

I'd have to check what happens with my setup but why would the image scale be different from image to image when you are using the same scope/camera combo?

The main 2 inputs were the arc/secpixel for the camera/scope and the north angle which your first post shows as 273 degrees. After that it all worked for me. I just checked with ccdcalc and your arc/sec is as you say - 1.39 arc secs/pixel.

It may seem arbitrary but why don't you try it using your RC rather than the TSA?

Perhaps ask Marcus he seemed to know a lot about it.

Greg.

[Paul Haese]

Thanks once again Greg.

It could well be vista but I have heard from a few others that say using this combination just never plate solves well. Meaning the software has its limitation. In an effort to find a way past all this I bought pinpoint tonight and installed AAG Tpoint mapper with Pinpoint. I can also use it in CCDsoft too. From what I have read so far I don't think I need to do a plate solve straight up. Once you open everything up I think you only need to hit the run button and it does the rest. Please correct me if I am wrong guys.

The odd thing there Greg is those figures are from the same image and each time I got a different results. That means something is wrong there.

I tried the little RC before and I could not get it to plate solve at all. I might have some luck now with pin point. The good thing is I can still use CCDsoft.

I have received a lot of great advice from both you and Marcus. I am just sorry this does not seem to work this way. It really seems odd that three programs which talk to each other really well can seem to fail to do the real task at hand. I will let you know how this goes with Pinpoint.

I once again thank everyone for their support.

[gregbradley]

You're welcome Paul. Marcus helped me a lot with this too.

Hi Tech equipment has a certain frailty about it. I have been amazed to have used my gear one night. Turn it off. Turn it on the next night and something isn't working and I have to find out why. I guess its part of this game being tolerant of the fact that your gear isn't always going to work everytime and be prepared to hunt down the cause. Some may even enjoy that aspect of it.

What is odd is that it was working some of the time. When mine wasn't working it failed 100% of the time and when it worked it worked virtually everytime. Could that mean a further looseness in the mechanics?

Greg.

[bert]

You keep having problems with plate solving and the answer is automapper. You do not need maxim for tpoint automapper. Just pinpoint. It will fix your problem. Spend the $120. Once you use it you will realize why everybody has been banging on about it.

Brett

[Paul Haese]

Brett I did that last night. I bought it and I can use CCDsoft with the program. Any tips on pinpoint use? After I have done all the setting in tpointmapper do I just simply hit the run buttom? What do I do about syn with the sky?

Greg, not sure, gliches are just hard work. Nights ought to be spent collecting data. I would just open up the mount and just check. It is all pretty easy to check all the nuts and bolts. When you get inside these things the units are pretty simple and elogantly designed.

[bert]

Make sure you have the right scaling in the settings tab, check that pinpoint is installed and the path to the guide catalog is set properly in am.

On one of the settings in automapper tabs, you must set that you are using the program for 'tpoint mapper mode'.

Make sure that the sky six is open and a new tpoint model is opened from the edit/ insert new object dropdown.

Other than that it is pretty much set and forget. It will blow your mind.

Having a PME and not using automapper/tpoint is like having a ferrari and not paying for fuel IMHO.

Brett

[Bassnut]

Hang on, I think your both mixing up different software (at times). Theres Automapper and AAG Tpoint mapper.

Ive only used AAG Tpointmapper and it works a treat, others have used Automapper and it works, so maybe software isnt the problem?.

[Doomsayer]

I think Brett meant AAG TpointMapper.
guy

[bert]

What Guy said. My bad.

[marc4darkskies]

Don't forget to adjust image scale if you're binning. 2x2 = 2.78 arcsec/pixel! Try it in CCDSoft with Insert WCS first.

[Bassnut]

Couple of little things. You dont have to sync. I set the mag to 20, if less then there might not be enough stars to plate solve on (seem to remember 10 didnt work). I assume you made the circular dot pointing map to suit the view the scope can see. Be sure to delete the old Tpoint model before you start a new one (in Sky). I tried some star catalogs (can remember which ones) the GSC works.

[Paul Haese]

I used pinpoint in maximDL last night and today and the same image plate solves to the same angle and with the same stars each time.

Fred, Brett confirmed the same thing that sync is not necessary. Sounds great to me. Whatever works is going to make me happy. I don't care which at present. I am using GSC1.1. I picked that up last year. Pretty comprehensive by the look. Interestingly USNOA2 had trouble plate solving; it kept going back and finding more stars, but GSC seems to work well with pinpoint. I have no idea why??

Marcus I tried that but still got inconsistent plate solves.

Next step go and give this a shot. Clear skies though would be good too.

Many thanks to all who have contribute so far and helped both here and privately. With any luck I will have this licked and onto some more imaging of those faint fuzzies. And; testing the new GSO RC12.

:thanx::thanx:

[Bassnut]

What?.

oh, and dont forget to "connect telescope" in DL

[Paul Haese]

I meant I have to go down to the observatory next week and give the whole system a run and see how it all works. I was plate solving with some images I did last week.

Thanks for the tip Fred. I probably would have forgotten that.

[gregbradley]

As I recall Marcus it you only have to enter the unbinned image scale and it calculates it itself if you use a different binning in the latest version of Automapper 11.

Greg.

[Paul Haese]

That was my thinking too Greg, but I tried what Marcus suggested and that still had nill effect. I think it is just a case where some get the CCDsoft, automapper II and the sky to work.

[gregbradley]

Yes its all very odd. Can't help but think Vista is in the background here messing with you.

I found Vista to be a real wreck of a platform and nothing worked well with it. Everything was a fight.

Best platform is still XP. Wins 7 seems OK.

Greg.

[Paul Haese]

You could be right Greg. However I would need to adapt a lot of my planetary stuff to win 7 if I updated. Not sure how that would go. I have heard differing reports. For the time being though I think I am onto so a winner. Time will tell though.

[marc4darkskies]

My experience has been if I don't set it in CCDSoft (ie during an initial Insert WCS) it won't work properly. I still set it in Automapper anyway - a better to be safe than sorry mindset.

Like you Greg I'm suspicious of Vista (and wouldn't touch it with a barge pole) but the symptoms don't really sound like an OS incompatibility. FYI, I'm in the process of migrating to a new Win7 64 bit lappy with TheSkyX. Everything seems to be integrating and working as it should. TSX has it's own built in mapping functionality but I haven't tested it yet.

[gregbradley]

Isn't that the other way round?

The Earth rotates around the actual pole not the refracted pole. So aligning to a refracted pole would be less accurate not more accurate.

Greg.

[frolinmod]

I'll amend my statement about which is better. For instance, he following website says that it's better to align on the refracted pole at mid to high latitudes and better to align on the true pole at low latitudes:

http://canburytech.net/DriftAlign/DriftAlign_3.html

And wouldn't you know it, I myself am right on the borderline between the two where one can just about flip a coin as to which is better.

[Bassnut]

Oh upgrade god :P;). Once you have a PME singing to spec, what possible advantage would there be in the pain, expense and time involved in upgrading anything (incl to MKS-5000 electronics in another post). Unlike other gear, once the obs PC just works on win XP and sky 6 and everything else, its time to quit mucking around and just get on with imaging ;).

A stable OBs PC is a valuable thing, its job is well defined and measurable so unless it actually improves image quality, fiddling can only make things worse.........or the same.

OK, ease of setup/calibration improves with upgrades, but if you have learnt an efficient proceedure already, and need to do it very occassionally, why bother with changes?.

[gregbradley]

Good point Fred.

A stable system that works every time is actually an achievement and a goal in itself. Its easy to take it for granted and think the grass is greener on the other side of the upgrade!

Greg.

[Paul Haese]

Update

Well finally got some clear sky and I wanted to report back a few things.

First the use of pinpoint and Tpoint mapper is superb. Of the 846 points I mapped last night only two failed. That was because it was trying to look through the pitch of the roll off roof. My polar alignment is now pretty good. Using 50 points on the east in one sector I got the PA to 11 seconds in altitude and 15 seconds in azimuth.

However, that is where the fun stopped. I found slap in the dec drive too. Not a lot but enough to be a problem. It seems that if I tighten up the balance knob and then turn it back one tick as per the manual the entire drive has about a millimeter or two of movement. I think the spring in the spring plunger assembly has lost some of its tension. I checked the screws on the spring plunger, and then set these back to factory defaults. So now to hunt down a new spring. The drive still works and I will now need another clear night to test to see if this is the last issue. As sort of confirmation I noted that movement on the scatter plot is in the same direction as this apparent slap. That being; points plotted in north and south hemispheres have similar separation angles but each hemisphere has a large separation angle. Is my thinking correct here?

Its been fun so far.:) Once I get this nutted I will have a huge sense of satisfaction that some just don't get with a PME. :lol:

[frolinmod]

Paul, 846 points shows quite some dedication. Are you still using TS6 or have you upgraded to TSX? If you're still using TS6, then could you please go into Tpoint and export your data to a text file and PM that to me. I'd like to run it through the TSX supermodel, look at the resulting model, look at the graphs, etc.

[gregbradley]

With that sort of accuracy in the model how did you determine there was slop in dec?

Isn't it usual to have a certain amount of play in a mount?

Greg.

[Paul Haese]

Ernie, I think you have mis-understood me. I did not do 846 in one go, it was several runs of successive models. The longest of which is a 192 point run, which you could take a look at it you like. I am still using TS6 though with the GSC1.1 catalogue.


Greg, I once again just grabbed the mount and found the slop. I am sure it is not supposed to be there. Like I said though, I need to test my theory and see if that has made any difference. I have got to contact software bisque to get another plunger spring too.

[gregbradley]

I thought it was best to do the model in one go rather than over successive nights.

Not sure why - I suppose the object is not at the same angle each night and you no longer have apples with apples.

Greg.

[Bassnut]

Your right, I just grabbed mine to check, no slop, at all.

[Paul Haese]

Greg, I just wanted to demonstrate that of the 846 points I mapped on about 6 runs each one solved except two points and that was because it could not see stars. A much larger model could be done but that will not help until I have solved the slop issues in the mount. Once this is done and it points better on the entire sky then I will do a larger model and perhaps a super model in one night. The main issue of course is getting the mount to point around 60 seconds without new terms first instead of on an all sky model of pointing at 159 seconds, despite a model of 50 points on the east side (narrow section of sky) showing pointing of 15 seconds. Then when I started on a whole sky model the pointing went to pieces.



Thanks Fred for the confirmation. I take it you are referring to both axis having no slop? That would be my understanding of what you are saying here. :)

[Bassnut]

Yes :scared3:

[Paul Haese]

No need to hide Fred. I will fix it. By the time I am done I will be one of the resident experts with PME's ;). Well at least I reckon there are not too many people who have pulled these things apart in Oz. Besides I have to look at the positive side here. There is always something good to take out of a situation.:)

[gary]

Hi Ernie,

Unfortunately there is no magical point in the sky to which one can align the polar
axis of an equatorial scope and then achieve zero field rotation for all possible observing
positions in the sky.

At best, there is a different optimal point at which to align the polar axis for each
possible declination and hour angle the scope can be pointed at and for each possible
value of the local temperature, local air pressure and wavelength of light at
which one is observing. The latitude and elevation of the observatory are also
factors.

The details are complex.

However ...

The version of TPOINT Paul has is fine and has been used to successfully align the
world's largest and most expensive telescopes for over 30 years. A table appears
on page 29 of the user manual that has estimates for the difference between the
true and refracted pole for various latitudes and different observatory altitudes.
The values in the table are in arc seconds and one should, in the southern
hemisphere, simply add the appropriate value to the value for ME. This then
gives the position of the refracted pole. In any case, the refracted pole is always
lifted above the true pole.

As a compromise, at Paul's mid latitude location he should be aiming for the
refracted pole especially for observations within a few hours either side of the
meridian. At your equatorial station, go for the true pole.

Best Regards

Gary Kopff
Mt Kuring-Gai

[Paul Haese]

Gary does Tpoint put you at the refracted pole via the corrections it gives you?

[gregbradley]

So should we be allowing a bit extra above to adjust our mounts to get to the true pole as opposed to refracted pole? Or is it not worth it as the differences are so fine that it is lost in PE anyway?

Greg.

[gary]

Hi Paul,

The actual numerical value for the ME term that TPOINT provides is for the true pole.

However, adjusting ME for the refracted pole is made trivial by use of a lookup table.
The following box is a table straight out of the TPOINT manual.


lat 0m 250m 500m 1000m 1500m 2000m 2500m 3000m

85 5 5 5 4 4 4 4 4
80 10 10 9 9 8 8 8 7
75 15 15 14 14 13 12 12 11
70 20 20 19 18 17 17 16 15
65 26 25 25 24 22 21 20 19
60 32 31 31 29 28 26 25 24
55 39 38 37 35 34 32 30 29
50 47 46 45 42 40 38 36 35
45 56 54 53 50 48 46 43 41
40 66 65 63 60 57 54 52 49
35 80 78 76 72 68 65 62 59
30 96 94 92 87 83 79 75 71
25 119 116 113 108 102 98 93 88
20 152 148 145 138 131 125 118 113
15 205 200 195 185 176 168 160 152
10 305 298 290 276 263 250 238 227

deg 0ft 820ft 1640ft 3280ft 4920ft 6560ft 8200ft 9840ft



Look up your nearest latitude in the left-hand column. For example, Melbourne
is approximately -37 S so the row for 35 will be the closest. One can always
interpolate a little. Then go across the columns to one that best matches the
elevation above sea level of your observatory. For example, for an observer
at -35 S and 250m above sea level, the table gives a value of 78.
That value is in arc seconds.

For observers in the southern hemisphere, if you want to set the polar axis of
the mount to the refracted pole, then aim for ME (in arc seconds) plus the
appropriate value from the table.

(Observers in the northern hemisphere will subtract the value in the table from ME).

The actual optimal point to which one aligns the polar axis depends on what
declination and hour angle you plan on observing.

Best Regards

Gary

[rally]

Guys this is all in the manual.

Tpoint's Polar Alignment Report corrections relate to the True Pole.

Use that to get it down to a level where any further adjustments on your system simply make it seesaw back and forth and then turn on Protrack and you will be good to go.

To get a good PA you really don't need many points at all, 10-20 is plenty, the extra mapped points are needed for Tpoint to correct for other terms of mechanical error and for Protrack.

PE has nothing to do with the polar alignment and pointing corrections - PE is usually much less of an error than the refracted pole to true pole error ie an arc second or two for PE verses an arc minute or two for atmospheric refraction shifting the optical polar alignment.

Good Guiding will take care of all of this in any event without Protrack

[gary]

Hi Greg,

The effect or refraction is to make things appear slightly higher in the sky than
they actually are.

Therefore the refracted pole is just above the true pole.

In Sydney, the refracted pole is approximately 90 arc seconds above the true
pole.

A simple thought experiment can help one visualize this.

Imagine for one moment that there actually was a star right at the South
Celestial Pole (wouldn't that be convenient :)).

Now that star, because of refraction, will appear slightly higher than it actually is.
if you were to set the polar axis to the true pole, that is just below the star, and then
take a long time exposure, the star trail would be an arc. However, if, you were
to align the polar axis to the refracted pole, then when you took the exposure the star
would essentially be a point.

Unfortunately there is a range of optimal points to adjust the elevation axis of the
scope for the infinite number of HA/Dec positions in the sky.

For practical purposes at these latitudes, a compromise of somewhere between
the true and refracted pole would be typical.

At the end of the day, one is trying to minimize the amount of field rotation
and if the mount does not provide a variable tracking rate facility but only
a fixed sidereal tracking rate, one is also trying to keep any residual between
the optimal instantaneous tracking rate and the fixed sidereal rate of the mount
to a minimum.

For example, for a star at the zenith, its true and refracted positions are the same.
However, it turns out that if the mount's axis is set to the refracted rather than the
true pole, the instantaneous tracking rate at the zenith becomes the classical
sidereal rate of 15 arc seconds per second.

So one can also make compromises between field rotation and tracking.

With regards these two specific problems, if software controlled variable
tracking rates are available, for most enthusiasts, trying to minimize field
rotation for the exposure time they use will be their primary concern.

Whether making an adjustment to your elevation axis to point above the
true pole will help you will depend upon your specific particulars, demands
and expectations. But not taking it into consideration can certainly impact
upon the quality of the results from some amateur rigs.

At the end of the day, it is important to remember that equatorial mounts can't
provide a perfect solution to the reality of us observing from the bottom of the
atmosphere. At best they are an engineering compromise. There is no magic
place in the sky to which their polar axis can be aligned to provide zero
field rotation and a uniform tracking rate.

Another common misconception is that a drift test is a gold standard way to
provide a mythical perfect alignment. At best, a drift test will give one solution
specifically derived from those two particular points used in the test, which may
be, for practical purposes sufficient, but a different drift test will give a slightly
different result, which is not surprising, as there is no one correct result that
is applicable across the whole sky.

For some, just the knowledge that there is no perfect solution will free them up
from the impossible task of trying to find one, which will then allow them
to focus more attention on aspects of their setup where there really is room for
improvement :thumbsup:

[rally]

I think Gary meant to say polar refraction is around 90 arc secs not arc minutes !

[gary]

Thanks Rally! In Sydney the refracted pole is approximately 90 arc seconds above
the true pole.

[Paul Haese]

Yes but it seemed to imply that Tpoint points you at the refracted pole. It does not say it will get you close and then you just turn on Protrack. The manual is not all that concise in this matter. :) I personally have read the manual on Tpoint at least 10 times now and never got the impression that it points you at the true pole and you just need to add for the refracted pole.



I did several runs at 30 and the runs at 50 and 100 gave me better results. I startted doing runs of 100 once I got the PA right with the smaller runs, however the slop in the Dec axis meant that Tpoint reported the PA was way off. Yes the extra points are for pointing only and not for PA. That is the main aim here. I can drift align to get good PA but I want good pointing Rally. There is no confusion here in my mind.



Yes PE is worm gear related and not a pointing related problem. PE affects guiding and tracking and nothing more. What makes you think we were meaning this? :shrug:


Thanks Gary for your explanation.

[rally]

Paul,

Protrack will not improve your polar alignment any further - that is not what it is intended to do.

If the mount is setup fairly accurately and level (use an inclinometer on the PME base and on the OTA) then with Tpoint you should be able to get a very reliable polar alignment in 2 rounds of 6-20 points

The first run is the rough run - just do 6, 7 or 8 points depending on how close to the SCP you are and how good the sigma is
Make an adjustment and repeat maybe going to between 10 and 20 points.
This usually provides sub 10 to sub 20 arc secs accuracy and this is in the field on a portable pier.
With just 20 points your pointing accuracy should be within a few arc secs across the sky.

This will be good enough for almost any level of work.

If you have been getting large Sigmas ? then maybe that was an indication of the additional mechanical problems that your particular mount has and maybe that is why you needed 100 points to get some averaging within the mechanical errors - because there is no normal reason to need 100 points purely for polar alignment.


Read this
http://www.bisque.com/tom/Paramount/LiveMapping_Files/makingadjustments.asp

The Tpoint manual tells how to set your mount to the refracted pole (instead of True pole), there is a few pages covering this topic in two sections.
So you must have skipped over those 2 sections 10 times :) - try searching for "refract"

To get better results and start removing any extra mechanical errors then you do of course need more points for Tpoints statistical analysis engine and Protrack wants lots of extra points too.

My comment re PE was in relation to Greg's question where he asked . . "Or is it not worth it as the differences are so fine that it is lost in PE anyway?"

Why on earth would you even attempt to drift align a P-ME ?
Surely that defeats the whole purpose.

Rally

[Paul Haese]

When did I say it would. Please re read my post on this. I said,"It does not say it will get you close and then you just turn on Protrack." I did not say it would improve my polar alignment???



Once again read posts further back when I explained I had found I was getting good pointing on the east side of the meridian and not moving the dec axis too much, but when I started doing bigger runs I found the pointing error was far too large. That prompted me to look for more mechanical errors.

I accept what your saying is ok and Tpoint manual suggests this, but some people have suggested I use a 20-50 point models to get better Tpoint suggestions for PA adjustment.



Yes that is right, I was not doing 100 points for PA but once PA was within a few seconds doing short runs I was looking to do the pointing model. Check on the PA after the 100 point run as a matter of course disclosed not only large PA error but large pointing errors and hence it led me to look for the mechanical error I found in the Dec axis.



No it does not. I have just done the refract search and it does not categorically state how to set for the refracted pole. Neither the PDF version nor the hard copy version I have here states exactly how to do this!

No need to be rude either by suggesting I skipped over something. I have very strong English literacy skills (Law degree and post graduate)and I can well argue that this manual does not tell you how to set for the refracted pole. I have read it all the way through that amount of times and I can attest what your saying is not true. You must have another copy that says otherwise. Even doing the search of refract. It does state that Tpoint makes refraction calculations (ergo one would think it has this in mind for the suggested adjustments to correct PA on the mount), It also states it is best to shoot for the refracted pole, it does state that southern hemisphere mounts will have a positive ME when aligned on the refracted pole, it also shows the figure that Gary has put up. However, it does not state how one goes about aiming for the refracted pole as you suggest. One can infer that you need to do the calculations and move the altitude axis until it reaches 72 for my location. At any rate, inference is not telling one how to do something. Not being argumentative here Rally but you were incorrect in what you said.:)



Ah yes and had you read further back you would be seeing that is what I have been doing. The larger models have been showing me that I have had large mechanical errors. The smaller models were not showing any large errors and that is what was confusing. Not only with the RA issue but also with the Dec having slop in it too. The north south pointing on larger models as you pointed out early on meant there was something amiss. Finding all this out whilst trying to sort out software (I now have that sorted by using Maxim, Tpoint mapper and pinpoint) which was giving me incorrect plate solves has been part of the examination process to sort this out.



When I was trying to determine what the problem was initially with the software (CCDsoft5 and automapper II) I did a polar alignment and it took me 2 hours to get it to 20 minutes each side. Quite frankly that was quicker than all the stuffing around I have had to go through to get software that actually works (not to mention the expense of doing that) and find all the problems and correct them. The mount was imaging fine in that I have done 5 completed images with it since I installed it, but I wanted better pointing and this led me down this track to finding out that there were problems in the mount that could have been avoided by installing parts better despite being told everything would be ok. So while I agree that doing a PA by drift defeats the purpose, I had to do it to confirm was something amiss. Simply sending the mount back to Ken or SB did not seem appropriate and I would not have learnt as much about this mount as I have. However, you can do a drift alignment on these mounts and it can be done very quickly to get it to 20 minutes each side (ie meridian and east stars).

Thanks for taking the time to put what you said down. Still appreciated but try not to treat me like a child; I don't really appreciate that. I have invested a lot of time in sorting these issues out and probably I would hazard to say more time than anyone has ever done with one of these mounts. Hence reading documentation several times to ensure I have not missed something. So when I say I have read something you can be assured I have studied the text, and understood what was being said. I did not simply skip things!! Reading is not skimming something. That is all I have to say about that.

[rally]

Paul,

Then why do you bother asking for help if you already know everything and have read everything and comprehend what you have read and then get upset when someone tries to take the time and effort to help you and become defensive, aggresive and call them a liar.

I referred you to the manual because that is THE best place for the explanations and the guides that will help you.
I would not normally bother going to try and cut and past the text without all the tables and diagrams in here when its already in the manual but since you deny they even exist - here they are.

The current Tpoint manual is located on the Software Bisque site
The old manuals are almost identical.
http://www.bisque.com/sc/media/p/28002/download.aspx
You need to be logged in to get it - I assume the link will work since its an aspx engine
That page is located here Filed under: TPoint (http://www.bisque.com/sc/media/g/classicdocs/tags/TPoint/default.aspx), Documentation (http://www.bisque.com/sc/media/g/classicdocs/tags/Documentation/default.aspx), Classic Docs (http://www.bisque.com/sc/media/g/classicdocs/tags/Classic+Docs/default.aspx), User Guides (http://www.bisque.com/sc/media/g/classicdocs/tags/User+Guides/default.aspx), Telescope Pointing Analysis System (http://www.bisque.com/sc/media/g/classicdocs/tags/Telescope+Pointing+Analysis+System/default.aspx)
Use those steps if the link doesnt work.

The Manual is entitled
TPoint for Windows
A Telescope Pointing Analysis System
User Guide
Revision 1.32

Pages 29 and 30 refers to the section on Polar alignment, the table Gary posted is there.

It states

"Optimum Location of the Polar Axis
The optimum polar-axis setting depends on what declination and hour angle you're observing. For observations on the meridian, somewhere between the true and refracted pole is best. Ideally, one should shoot for the refracted pole. For typical users in the continental US the refracted pole is 1-1.5 arcminutes above the true pole. For observers in the northern hemisphere, this corresponds to ME = -60 to -90. For southern hemisphere observers it's plus not minus, so for Sydney Australia aim for ME = +90.
The following table shows the angular distance (in arcseconds) between the refracted and unrefracted poles for different latitudes and elevations.

----------
Note - Table is inserted here but I havent included it
----------

If you want to set your polar axis to the refracted pole, and you're in the northern hemisphere, aim for ME = minus the tabulated value. In the south aim for ME = plus the value."

I think the last sentence is pretty clear - "If you want to set your polar axis to the refracted pole" (as opposed to the True Pole) . . .


On Page 40 in the section entitled
Using TPoint to Suggest Telescope Modeling Terms

It states
"Remember, it is best to shoot for the refracted pole, which is about 90 arcseconds above the true pole. This has the same effect as the “Kings Rate” in that it will somewhat average out the effects of atmospheric refraction. See the “Optimum Location of the Polar Axis” on page 29 for more information."

Referring the reader back to page 29

On Page 48 in the section about Polar Alignment errors section
It states

"Polar Alignment Error in Elevation
In the Northern Hemisphere, a positive ME means that the pole of the mounting is below the true (unrefracted) pole. A mounting aligned on the refracted pole will have a negative ME. In the Southern Hemisphere, a positive ME means that the pole of the mounting is above the true (unrefracted) pole. A mounting aligned on the refracted pole will have a positive ME."

This again clearly differentiates between the True Pole and the Refracted pole and explains what readings you will get and why you will get them.

On page 74 in the "ME Term" description section

It states :
"Term: ME
Vertical misalignment of the polar axis of an equatorial mount: a rotation about an east-west axis equal to coefficient ME.
Notes: In the Northern Hemisphere, positive ME means that the pole of the mounting is below the true (unrefracted) pole. A mounting aligned the refracted pole (for most telescopes probably the simplest and best thing to aim for in order to avoid unwanted field rotation effects) will have negative ME.
In the southern hemisphere, positive ME means that the pole of the mounting is above the true (unrefracted) pole, and a mounting aligned the refracted pole will have positive ME."

I would repeat my suggestion that either you didnt read this or you didnt comprehend these clear specific and well explained references to the Refracted and Unrefracted (True) poles and how to set up your mount.

Good luck with it.

[bert]

I have used tpoint for the sky6. And I felt like I was stabbing in the dark. Since I have upgraded to skyx, I have found the tpoint side of things to be more intuitive. Skyx clearly states the elevation value to the true pole, and to the refracted pole.

Brett

[Bassnut]

What a great thread, what a mine of really usefull information :D :thumbsup:

[bert]

Not trying to hijack the thread.... I'm doing a polar alignment on a pme atm.

I seem to get pa elevation with a consistant result of under an arcminute out, I think from memory around 50 seconds from the true pole. But azimuth seems to fluctuate, there is no pattern in the tpoint model that tells me that there is a mechanical problem. I ended up doing a drift align and adjusted till I was getting no pixel drift in 10 minutes (.86 arc sec per pixel). Tpoint still tells me that I am 2 minutes out.

I guess my questions are;

How many arc seconds out do consider a good polar alignment?

How consistant are your result from a 30 point models? (eg within 20 arc seconds etc)

Thanks
Brett

[gregbradley]

The pdf that has the Tpoint tutorial and example goes over the number of points you need before you can introduce extra terms.

From memory I think that was about 50. There is a maximum number of terms suggested you can add with the lower number of map points.

You also need to fit the data and remove outlier to make the model more accurate.

Only then it says is the PA model accurate.

So the idea you can do 6-20 may work but it isn't what is in this tutorial.

In my experience with my setup (limited experience) I manually did models of up to 30 points. I found the PA suggestions sometimes made the guiding worse so I therefore assume further away from accurate PA.

I did 200 point model (it only took about an hour) and used those suggestions. They improved things. Mind you it is easy to adjust the elevation the wrong way so if there is any doubt about which way to turn that check the manual before you do it.

I have also done a few 50 - 100 point models and after fitting the data, getting rid of outliers, adding terms the PA adjustments seemed to improve things. I do an autoguiding straight after an adjustment as final proof I did improve things and not worsen them.

If you aren't doing large enough models, and removing outliers then adding terms then the PA adjustments may not be correct as they will change when you do this.

I use 3x3 binning when using my Proline 16803 or 2x2 binning with the ML8300, 10 second exposures, slew time seems to be about 5-6 seconds, download time is 1 second so the whole thing from slewing to the point, taking the exposure, plate solving it takes 19 seconds on my setup. I could probably reduce that to 15 seconds by using 6 second exposures if it were a moonless clear night.

So try the above and see how it goes.

It does seem a bit elusive to get it exactly perfect. My setup is very close (the PA adjustments said zero in one axes) yet I sometimes get slightly eggy stars still. I am wondering if I am getting flexure in my guide camera in the MMOAG.

Greg.

[Paul Haese]

Final update - Problem solved

Firstly, I want to thank everyone who contributed to the thread. I would like it to be instructive of how to sort problems on an expensive mount if it is second hand and how to get things sorted on the software side.

My recommendations-

Don't use any other programs other than MaximDL, Pinpoint, Tpoint, Tpoint mapper and TS. This combination gives me 100% pointing plates solves except when an obstruction is in the way (ie cloud or roof or trees). Its plate solving has resulted in the model below.

Check your mount thoroughly. In my case I had an incorrectly installed worm gear (grub screws were lose) and the dec axis has a worn spring in the spring plunger assembly (soon to be fixed too but still operates at present).

Read the manuals several times and call mates to help in understanding and nutting out a fairly vague set of instructions (Rally I will have agree to disagree about how things are read). Use this thread as an instructive base for where to start. Each persons gear is different but some common aspects are present.

Check all the connections to camera and gear regularly, sometimes things slip or just work lose (this did not happen in my case but I just checked anyway).

Now for the piece de resitance, the model below is 181 points. Pointing without terms was 62 arc seconds across the sky. I got clouded out and could not finish a 250 point run but the model was reducing in arc seconds on each hit after 150.

The PA information on the first part of the model at 50 points showed no need to move the mount and so i continued on to do a larger run. It now shows that ME is nearing the refracted pole for my observatory and and the MA is just a touch out. Some mild refining could be done later but for now it is not necessary.

The fit information shows that the terms used were as per recommendations (that sigma should be around or less than half of the value applied). I used 6 extra terms to result in a 10.3 arc second pointing of the mount.

The scatter plot confirms that the run does not have the North South divide it had in previous runs, and this would indicate that the mechanical errors have been eradicated from the system. The remaining errors are mostly going to be lost in the noise.

Now onto imaging again. I did a test pointing at the lagoon through high cloud and the mount put the center of the image in the exact center of the lagoons cluster. Very happy with this results and relieved this matter is finally sorted.

Thanks once again for the help.

PS Brett I am thinking 15 seconds in MA is fine and something around your refracted pole is fine. In reality anything under a minute on each is pretty good. Just my opinion though.

[frolinmod]

Tpoint for Windows as used with TheSky6 aligns you to the true pole.

Tpoint Add On for TheSkyX Professional aligns you to the refracted pole.

[gary]

Hi Ernie,

Just to qualify.

Whenever you see the ME term in either version of TPOINT, it is always referring to the true pole.

Both versions provide a verbose alignment recommendation report in English text
which is an interpretation of the numerical MA and ME values.

The TPOINT version that works with TheSky6 gives a verbose report in terms of
aligning to the true pole.

The TPOINT version that works with the SkyX gives a verbose report in terms of
aligning with the refracted pole and the report has an explicit note that alerts to this.
The report in this instance gives both ME and what the report refers to as 'Ideal ME'.
'Ideal ME' is simply ME plus or minus the correction interpolated from the lookup table
in the manual.

The 'Ideal ME' is somewhat of a misnomer as it is not necessarily always the ideal
point to which to align the polar axis anymore than the ME point, as discussed
earlier. Depending on where one is imaging in the sky, the optimal point will
be somewhere in the range true pole to refracted pole.

Since circumstances therefore change as to where one might want to align the
polar axis, the ME value for the true pole is what is important to know as then
one can simply make the necessary offset to it.

The bottom line -
Whenever someone reports ME, it will always refer to the true pole, irrespective
of the version. :thumbsup:

[gregbradley]

So if you are using Tpoint for windows you would look up the offset to true pole and go for being a bit above what tpoint for windows says is perfect?

For Sydney is that about 90 arc secs?

Also with X Y errors when autoguiding do the X errors relate to alt?

I redid my PEC tonight and got quite a similar curve to what I got a few months ago. I then double checked (using the auto button to check it) to check the east west button. It turned out my PEC curve was upside down. Now corrected the PEC is helping not fighting the autoguider and I am getting rounder stars which is a relief.

This mount is so accurate this little fine points make a huge difference. My mount has about 2.3 arc seconds of PE peak to valley. That's pretty phenomenal.

Also do what is the consensus about usong Protrack?
If I had say a 250-300 point model of the whole sky would I expect to see an improvement in tracking if I activated Protrack whilst using PEC and autoguiding?

I have turned it on when I had a 200 point model and it seemed to worsen slightly the guiding.
Greg.

[frolinmod]

I guess I'm lucky. I get an improvement here with ProTrack and only 190 or so points. Fewer points does indeed appear to make it worse rather than better, at least for me. I'm using TheSkyX and having Tpoint compute a supermodel. I suspect that how many points are needed before tracking gets better rather than worse with ProTrack is probably unique to the particular equipment load and it's characteristics (i.e., the model that gets computed vs. reality and the residuals between them).

[Paul Haese]

Just a small epilogue here people. Last night I went down to the obs and managed to get my PEC sorted (0.5" peak) and then before the cloud came in I got a 12 minute sub. Part of the sub was guided and then I lost the guide star, so 6 minutes or so were unguided. Pointing was just about as close as I could expect. The image attached is of Corona Australus. The two stars with the small amount of nebulosity at center (in between the two stars) is where the sky pointed the mount; and the image center is just a thousanth or so out (most likely the 10" or error). In other words, great pointing. Spica was also pointed at for the PE data and that was so close to center. So proof of concept and pointing has worked. And; as you can see nice tight stars. Pretty happy with that too.

[frolinmod]

You should absolutely be able to image unguided at a focal length of four meters for at least five minutes with nice round stars.