Losmandy GM-8 (w/Gemini) - Help save my sanity.

[rogerg]

I'm after help, stories of your troubles and triumphs, and any general information to help me use my Losmandy GM-8 (with gemini) better.

The Losmandy is my portable setup. So it's never setup in the same place twice within a 4 week period. Perhaps this is part of my problem.

Ignoring the drift method, I find it very hard to consistently get good polar alignment. I try using the Polar Align Assist and Polar Align Correction functions of the Gemini. Sometimes I think they work but then soon find they clearly haven't and I still seem to be off.

I seem to consistently have different RA tracking problems - like, tracking at the wrong speed. This weekend for example I got it setup, used Polar Align Correction, then was trying to autoguide on a star near 47 Tuc only to discover after experimenting that if I turned off the RA motor (set tracking to terrestial) the guide star was drifting at the same rate .. so like the RA motor wasn't working but it was turning.. and moving to Orion it was tracking...

Most of my problems seem to have the symptom that the RA tracking is wrong. Dec drift occurs but nothing like RA drift. I don't really understand what affects RA tracking?

Balance is generally perfect, I can move all payloads in all directions and easily counter-balance the setup (it's well under weight limit). I use the standard counterweight.

My LX200 I can easily polar align by hopping between two SAO stars and making appropriate correctsion. I duno why it's so hard on the Losmandy, I think maybe just because I'm always in a new location with that bit more uncertainty on N/S direction, correct level of the mount, etc.

Setting it up for visual use is a breeze, after doing 4 odd additional alignments it'll go straight to each object dead bang on centre no problem, and track them fine. Getting the level of tracking accuracy needed for photography seems to be a completely different story, more so than with my LX.

Any input? tips? pointers? What's your setup proceedure? help! :help:

I'm getting sick of wasting my 400km trips to the country. I feel like a $1000 mount would behave better than my $4000 mount right now. :sad:

Maybe I don't set the RA/DEC locks the right tightness? maybe my initial polar alignment guess is so far off nothing works? maybe I need to adjust the worm gears? maybe I just need to understand the manual better. I do refer to the manual continuously when trying to use the different gemini alignment functions to make sure I get it right, out of frustration more than anything.

Oh and there are occasions when it works. Really don't know what the difference is - as I said at the start, observing sessions with it are usually 2 weeks apart at least, 4 weeks for deep sky astro photography stuff so it's hard to remember between goes the finer details a paturn of what works and what doesn't.

Roger.

[JohnG]

Hi Roger

Couple of things, what Level Gemini do you have. Prior to Level 3 Version 1.13 there were problems with PAC, it was southern hemishere specific and would send your correction in the wrong direction. This was supposed to have been fixed in Level 3, Version 1.13.

I am asuming you have done this as you are experienced in using a Gemini. Have you checked your cables, no obvious faults. How is the 2032 battery, if it has been in the unit for more than 12 months it should be changed, a lot of problems can be traced back to this. Do you have the Gemini in Photo or All Speeds Mode when using the autoguider. How is your power supply, is the Gemini getting enough power.

I know these are the basics and you have probably already eliminated them but it is a start point.

Cheers

JohnG

[[1ponders]]

Jeez Roger, what a pain. And often its something simple :rolleyes: I wish I could help but I don't have gemini. You've checked the obvious I gather? Right mount selected, gemini hasn't defaulted back to its factory setting? The usual stuff?

The only thing I can offer is; we were having trouble with the G11 at the Maplton Observatory, it was doing really weird things, and not consistantly wierd. Like loosing location, wrong time, not slewing to the correct coordinates, defaulting to a different mount at start up. What it turned out to be was the internal battery was shot (in fact it was the wrong battery, and it had been installed in the factory, we had never changed it previously). Change the battery and we haven't had a problem since.

That might be a place to start. How about trying a very quick, hard and dirty, half hour say, dirft alignment and then use the build in corrections? See if that makes a difference.

[[1ponders]]

Snap John :)

[JohnG]

OK Paul, I'll bite :whistle:

JohnG

[rogerg]

I'm happy to start at the basics, believe me. I'm sure it is something really basic that I should have worked out by now.

Gemini Level: L4 (installed a couple of months ago .... which makes me wonder, as the last 2 trips have been particularly bad... hmm, I haven't checked what bugs there are in it's version)

Power: About 16.5v. I have one of these multi-voltage things made for plugging into a car cigaret lighter sockent which has settings for 12v, 15v, 17v, 19v. I have it set to 15v and with no load it registeres at 16.5v, haven't checked it when there's load on it. Battery is 40Ah so lots of juice available in general.

2032 - I will replace this, good idea. It's been something like 9 months.

When tracking I have the gemini in Visual Mode. I'm tracking using GuideDog and a webcam, interfacing to the scope through the standard RS232 connection not the autoguider port, so as I understand it (and have seen from experimentation) the mode doesn't matter for this... Yet to really get the hang of this setup (guidedog with webcam to gemini) though, still new at this.

I haven't checked voltages on pins of cables, but it will GoTo accuarately, so assume the cables are OK. I sure knew I'd plugged the RA and DEC in around the wrong way when I did that one time recnetly :rofl: , that I could diagnose!

Thanks,
Roger.

[JohnG]

I am wondering about Level 4, there have seemed to be a lot of problems with the L4 release. Someone else from IIS was on the Gemini Group recently complaining about PAC problems, just wondering if the bug was re-introduced.

Do you use ASCOM at all, there was a special release for L4.

I am still using L3, v 1.13 and have just done a battery replacement after I was getting some weird behaviour, all is right again now.

Do you still have your L3 chip, if it keeps playing up, change it back, There was some talk about dud chips!!!!

Cheers

JohnG

[rogerg]

Interesting.... I'm now feeling suspicious of L4.



No.. I just have an older ASCOM (downloaded it a while back), I don't remember having to download a new one recently. Perhaps this is a major source of my problems for auto guiding. I will take a look at this as soon as I get home.



Yeap, still have the L3 chip safe and sound - I had a feeling I might want to put it back in some time....

Thanks heaps... all progress, hopefully some of it will make life easier...

[JohnG]

Quote

"When tracking I have the gemini in Visual Mode. I'm tracking using GuideDog and a webcam, interfacing to the scope through the standard RS232 connection not the autoguider port, so as I understand it (and have seen from experimentation) the mode doesn't matter for this... Yet to really get the hang of this setup (guidedog with webcam to gemini) though, still new at this."



I have just re-read this, not having tried this at all but what about your guide speed, I know that for normal autoguiding it should be around 0.8 or 0.5, have you changed that when you are autoguiding through the RS-232 port. Maybe there is over-correcting which is causing your RA drift.

When you use the autoguider port and when set to Photo Mode, the guidespeed is automatically reduced.

Just a thought.

Cheers

JohnG

[JohnG]

There was a special Gemini Driver released on the ASCOM site specifically for L4, it is an executable file and will only work with L4.

Cheers

JohnG

[Lee]

That was me on the Yahoo Group with the PAC problem - I still think that component of Gemini L4 is buggy, and am about to email Rene Goerlich with some data from last night.

I drift aligned (my first time - thanks to your website Roger!) - then did an 8 star alignment - Gemini reported I was off by -28' in azimuth and -20' in elevation - after a 50% or so correction with PAC the figures were A = -11 E = -34 - I'm sure that it gives elevation correction backwards - and had similar problems last week at home.

I'm going to stick to drift aligning I think! seems easier...... a pain, because PAC seems so elegant and simple..... :shrug:

[JohnH]

Rodger,

Assuming you have a laptop and webcam available this tool is great as it calculates the amount of adjustment required for ALT and AZ and provided a screen to let you make the adjustments with precision. I use it to polar align my mount each use as I do not have a permanent setup - and gets me close enough for 5 mins exps without field rotation at f9 with a Canon 20d in about 20-30mins. I could never quite figure the drift method - this tool is visual so using it is quite easy - takes a couple of goes to get familiar with it....

http://wcs.ruthner.at/index-en.htm

[rogerg]

Excellent. Thankyou all. I have downloaded the new ASCOM drivers (I had version 3 something) and will download the program you have recommend John (H). I'll see how I go.

I'll also not use the Gemini's PAC, I'll stick to other methods instead, probably using two stars and hopping betwen them making corrections, like the Polar Align Assist does but I do it manually (silly how they have such a small list of stars available).

Hopefully I'll improve the situation.

Roger.

[[1ponders]]

I know what you mean Roger. You'd think you would be able to use any star in the database, but realistically at least all common named stars down to mag 4 could be included in the alignment list.

[Lee]

I think you can use any of the objects in Geminis database for alignments - it is just that the alignment stars are more accurately positioned - what difference it would make I have absolutely no idea....

[jase]

I'm using L4 v1.01 on a Titan with no problems assocated with PAC. If you've got a CCD camera and time, a CCD drift align works best. PAC got me very close to the pole though. Probably close enought to use an 800mm FL instrument for 5-10 minute unguided exposures.

Indeed you can use any object for an alignment, just select the object from the object database, slew to it. The select align telescope and the last object chosen is selected. This seems to work well. You can also use TheSky to do a similar task. If you want to get really serious, get yourself a copy of TPoint and then perform an 180 point model. Takes some time, but if you want to precisely know how far from the pole you are, this is very very accurate. TPoint will also ensure any object you slew to is always on the CCD chip. Nice for robotic operations. :)

[rogerg]

That's pretty impressive unguided times. Seems perhapf the PAC problems depend on a few factors - hence sometimes working and sometimes not.



Yeah, TPoint has been on my list for a while, to use with my LX200 though I have to admit. It'd be extremely nice. Just a little pricey for my budget (but fairly priced for the product).

I use TheSky so just use that for picking stars to align on.

Still haven't had time to try the new ASCOM version for the Gemini, hoping to do that this week.

Roger.

[jase]

Roger,
When you do additional aligns after a cold start and one star sync, do you see the A and E numbers vary after each alignment? I've seen this and believe it is particularly common on a SCT due to very slight changes in the primary mirror movement. It doesn't have to move much especially if your using a 9mm guide eyepeice. This is utimately what the Gemini pointing model is trying to determine i.e, mirror flop and flexure in the set up. This is generally a good thing as it will improve goto slew accuracy, however when it comes to PAC the accuracy isn't the same. If you have a refractor (such as your Megrez 80) or a decent finder scope, then I'd highly recommend using this compared to the SCT. Also when centering the star, I usually go to photo mode and ensure the alignment is dead centre with the eyepeice cross-hairs. I'd be interested to hear how you get on with the refractor and if the accuracy changes.:)

Indeed PAC can get you close. I'm impressed with the capabilities of the Titan mount. Big payload capacity and superb tracking. I will admit that the mount does take some tweaking though. Fine adjustments of the worm block with an automotive feeler gauge was need to minimise backlash in both Dec and RA. A few other tweaks also. Works a GEM now (no pun intended).:thumbsup:

[rogerg]

Jase,

Thanks very much for your input. I can see what you mean with the SCT and how movements such as mirror flop could adversley affect the PAC. I'm keen to try it out again and see how I go, to be honest I haven't had the opportunity to use the setup since my last encounter which prompted this thread, so I haven't tried any of the suggestions here yet. I'm hoping to this week, Saturday at the latest.

It was only the last time that I used the scope which I started to think "hmm, i wonder what those numbers actually mean, perhaps I should be looking at them". They were huge some times (I remember seeing numbers like 300!) but can't remember what measurement they were in. It also sounds like I need to be more careful with the PAC - I typically have just put my 22mm Panoptic in the Megrez 80 (480mm focal length) and centered the star using that. I've done this because it's easy to find the star and center it. I am usually too lazy to put the illuminated crosshair eyepiece in. I think that's just not good enough and I should now definitely use the 9mm illuminated eyepiece, perhaps even with the doubler. Using the 22mm is just too lazy on my part. Your reply has made me realise that.

One thing that I still find a little confusing is that I can more often than not achieve a pointing model which results in every GoTo being dead on accurate. I'm very very impressed with it's modelling capabilities in that respect. Yet at the same time, the tracking will be way off - completely un-usable for guiding.

Roger.

[jase]

Hi Roger,
Wow, A and E numbers up into the 300's is rather far off alignment. I started around -60, 30 and worked from there. I did cheat a little though. On the initial set up, I used a GPS compass to tell me the direction of true north/south, not magnetic. Once I had a visual, I used a tree in the general direction to get close alignment. I refined using PAC. I'm assuming you've got a permanent set up (considering you sig. also mentions an observatory), so it would be wise to spend a while perfecting the alignment of stars. When I ran PAC now and then I usually get A: 1 E: -2 so I'm pretty close to being polar aligned. Don't forget the hidden enemy - flexure. Make sure everything is secure. In some cases there is not much you can do about this and something the pointing model will assist you with.

The pointing model will continue to work even if you're not dead on the south celestrial pole. In fact, you simply have to be facing the axis south - nothing else. This is great for visual work, but as you've found out tracking isn't very good. The point model will continue to place objects in the field of view despite the misalignment.

On Page 39 of the Gemini L4 manual you'll find some interesting figures on your pointing model. A snipet of the info is below. There is some really nice information to check out on how well you set up is working. Keeping an eye on these values will assist you.

3.5.3 Modeling Parameters
Gemini models the following mount and telescope parameters:
• Azimuth misalignment from the pole
• Elevation misalignment from the pole
• Axis non-perpendicularity at the pole
• Axis non-perpendicularity at the equator
• Gear play
• Mirror flop
• Index error in hour angle
• Index error in declination
• Counterweight flexure
You can examine each of these parameters immediately after an additional alignment. The azimuth and elevation misalignment (A and E) are displayed right after the “Additional Align” is executed. You can also use the “Show Information” menu item to display the other parameters: NP = non-perpendicularity at the pole, NE = nonperpendicularity
at the equator, FR = gear play (in RA), FD = mirror flop (in Dec.), IH =
Hour Angle index error, ID = declination index error, and CF = counterweight flexure.
All values are given in minutes of arc. These values give you valuable information about your alignment, your mount and your telescope.

Hope this helps.:thumbsup:

[JohnG]

A and E numbers that are high on the first couple of aligns are not unusual, because this Gemini is on portable mount, I would, and do myself on my portable mount, a quick Drift Align, that gets you close to the mark.

As you guide with the RS 232 port and not the Autoguder Port, out of curiosity, what is your Guide Speed. I have a gut feeling that you might find that is where your guide errors are coming from.

Cheers

JohnG

[rogerg]

Jase, as John has picked up on my Losmandy is my portable setup, the LX is permenantly mounted (works like a dream). So considering I don't use a compas (the only one I have is a dodgy no good thing) and I simply rely on knowing roughly where sigma Oct is, it would not surprise me if my initial alignment is considerably off - perhaps 10 degrees in azmith, who knows.

I will be interested to take more note of the A & E numbers now, and look that info, I've never explored the "Show Information" menu option.

John, having to do any drift alignment is exactly one of the things I'm trying to avoid, simply because I figure "there has to be a quicker way", I always used to do drift alignment with my previous portable mount. To be honest I think I'd instead (assuming PAC doesn't work for me straight off) use 2 stars and hop between them using TheSky adjusting just the alt and the az as appropriate, I have had some success with this in the past ... but need more trialing and experience with it.

The guide rate for autoguiding - I am still not sure what's best here, considering I'm working through the RS232. Last time I was trying it out with the Gemini set to 2x sidereal, but to be honest I'm unclear as to exactly how this affects autoguiding. My current understanding is that using it how I am, GuideDog won't actually change the rate of movement but will change the amount of movement, it will do that depending on what figure I put in it's setup and in it's N/S/E/W text area that defaults to "500". My understanding is that because GuideDog doesn't alter the speed of the slews, only the time of them, if I set the Gemini to 8x instead of 2x it'd move a lot more for each correction. Which means if I'm not seeing much change resulting from autoguiding I'm guessing I should increase the rate up from 2x ... but 2x is pretty big for autoguiding I figure.

Roger.

[jase]

For suggestions and tips on using the RS232 port on a Gemini for autoguiding, I have found the Barkosoftware support pages valuable. These guy produce Guidedog software that does the autoguiding.

http://www.barkosoftware.com/GuideDog/
Select the Discussion button, then Choose Losmandy (or the desired mount)


:thumbsup:

[JohnG]

Hi Roger

I appreciate what you are trying to do but, in my opinion, nothing beats a reasonable Drift Align, at the most it takes me about 15 minutes and is done during twilight, that will get you well under a degree from the pole and, in which case, improve your tracking.

I feel you are way to high with your Guide Speed, in my opinion, what is happening is that you are getting an ocillation. Guide Speed with the Autoguider Port is 0.8 as default. I personally would drop your guidespeed vide the Hand Controller to 0.5 - 0.8 and see what happens.

My understanding of GuideDog is that those numbers you mentioned are for the amount of time the guide mode is operated, not the actual speed. On my non-gemini GM-8, I still have to set the guide speed to 0.5 using GuideDog.

Hope that helps a little.

Cheers

JohnG

[rogerg]

Thanks guys, all very helpful. I just need to actually be able to test it out again now. :) Hopefully I'll report back with success in a couple of days.

Roger.

[JohnG]

Roger

There was one other thing I found during extensive testing some 12 months ago, even though the Gemini Manual say's it can be done, I found that I had to uncheck the simultaneous guide signals. I know that if you have the DIN motor plugs you can do simultaneous corrections to both axis, I found that using an LPI you had to uncheck this option and only have sequential corrections.

Just a thought.

Cheers

JohnG

[Garyh]

Hi Roger,
Been following the thread to see how it goes as I will set up autoguiding in the future.
With the polar aligning I usually just drift align for a hour to get real close.
But what I found with my last mount was that when I had the mount very well aligned I would have a finderscope that sat on a little dovetail plate and I had alignment marks on both sides the dec axis, then I adjusted the finder to put the crosshairs on the closest star in Octans Sigma (I think). So next time I set up I just line up the marks on the dec and put the little finder on the mount and adjust the mount till the crosshair was on sigma oct again. Worked very well.
Might sound lame but might be good if you are travelling a bit.
Cheers Gary

[rogerg]

As much as getting a polar alignment I'm now trying to understand what the Gemini is telling me.

I am out here for the first night since all this info was posted in this thread and I've done an alignment via a particular method. After that my pointing accuracy was close in DEC but far off in RA. I then did several additional alignments to build a pointing model and have these numbers shown when doing "Show Information" which don't match the acrynms in the manual:

dH: 22'
dD: -17'
A: -119'
E: 210'
NE: 47'
NP: 17'
IH: -120'
ID: -231'

Meanings:
dH=?
dD=?
A=Azimuth misalignment
E=Elevation misalignment
NE=non-perpendicularity at the equator
NP=non-perpendicularity at the pole
IH=Hour Angle index error
ID=Declination index error

I see no values for CF, FR, FD mentioned in the manual, presumably 2 of them are dH and dD.

Can anyone explain these numbers in simple terms to help me understand from these numbers how my alignment is off, or, if I'm seeing huge numbers because of an L4 bug?

I'm about to commence a drift alignment to see how that changes things.

Thankyou for all the help provided, I'm learning lots from this.

Roger.

[rogerg]

Another question (I hope you guy's don't mind me being such a pain asking so many questions, but there are so many...)

More a Losmandy question than a Gemini question probably: It seems when I make small corrections (at say 2x siderial) in RA and DEC, there's some drift that occurs after the movement. That is, the movement isn't precise, it moves as I tell it to, then keeps moving somewhat. It's not a "short sharp burst" like I get on my LX200.

Any ideas what that could be?

(and yes, the system is balanced in all directions)

:help:

Roger.

[[1ponders]]

I've had that happen at higher sidereal rates but not at less than 4X.

[Lee]

Roger - I set up the other night, did a 6 star model, and was told I was A=-180 E=-60..... so I drift aligned using your website instructions, then cold started and built another similar model ---- A=-1 E=-2..... your name was gold around here then.... :D

Sheesh though - drift aligning at the western horizon..... the only star I found was only really visible with averted vision, trying to watch it whilst standing on a ladder looking into the EP..... we need a bunch of Dec=0 supernovae I think! hehe

[JohnG]

Hi Roger

To be quite honest, I personally don't take any notice of all those numbers, the only one's that I do take notice of is the A and E numbers, mine are 0 and -1. My honest opinion is that after a lot of years of using a Gemini, they are the only numbers that mean anything. All these numbers are taken into account when Gemini builds it's Pointing Model, that is why I don't bother with them.

I, like Lee, am a firm believer of doing a proper Drift Align first off, I still believe this is the most accurate way of getting the scope and mount close to the poles.

Not sure what those abbreviations mean, will have to look them up but, I would say one has to do with counterweight flexure.

The overshoot sounds a bit like a backlash problem, your worm MAY be a little too loose. Before mucking around with the worm, I would try to unbalance the mount slightly, have the weight pushing against the worm, you may have it balanced too well.

Cheers

JohnG

[rogerg]

G'morning all,

Well after my last post last night I then did a drift alignment, the good 'ol way. That worked a treat. Interestingly my elevation was out by about 4 degrees! The rotation was pretty much correct, only small change there.

Lee - good to hear the page is useful :) I always used to do a drift alignment before I got my Losmandy, since then I've been trying other methods to try and speed up the process (even though a drift alignment only takes 30 odd minutes..) .. I will now regress back to drift alignment and save myself the hassles. Seems to save time in the long run.

I am still interested in understanding what's going wrong with my other attempts "the gemini way", but not sure I'll get that understanding until I discuss it in person with someone who's been through it all before.

I didn't get to trying autoguiding last night, so that one is still up in the air - not sure the results of the new ASCOM version yet, have only been using TheSky last night.

Tonight I'm going to have another crack at it, at a semi-dark location so will see how that goes. I'll be doing the drift alignment.

Roger.

[rogerg]

Well I'm starting to have some success. Some may have seen the thread http://www.iceinspace.com.au/forum/showthread.php?t=14160 showing my orion shot, short exposure but at least it was guiding OK for that time.

Progress:

I'm doing drift alignment only now, back to my old trusty drifty alignment instructions. Last night I spent about 45min doing that but was talking to people etc during that time. Reached reasonable alignment but still could have been improved. When doing a few additiona alignments I found the Gemini reported A: 12 and E: 26, which are far smaller numbers than I was getting using other methods.

While doing the drift alignment I was careful to tighten the mount before slewing, as I've noticed that in particular the azmith of the GM-8 has quite a bit of wobble/flex in it if you do'nt have both the knobs tensioned. Remembering to tighten it all up once aligned helped too (easily forget that sometimes).

With the polar alignment working OK, it seems GuideDog instantly became more happy. Last time I simply couldn't get it workiing yet last night I couldn't seem to break it. It does appear that changing the slew speed on the Gemini hand controller does affect the behaviour of GuideDog (as expected). I sended up setting it to Photo Mode and it worked well there. It took a little while to centre the star each time because of the slow movements, but it got there in a minute or 2. I think I still need to adjust the speed a little, it was hopping around a reasonable amount sometimes, I think because the guide speed needed to go down a little. Haven't tested that theory yet. Viewing conditions were horrific.

Guiding at 1400mm instead of 700mm made a nice difference to the resulting DSLR shots, quite a dramatic decrease in trails. The DSLR was shooting through the Megrez @ 480mm (abouts).

The 6 point scope rings for the guide scope are a must, as is the extension bar I had my back neighbour machine up for me to extend the distance between the rings. I'm not entirely happy with the solution here, as the guide scope can slide down the rings, but haven't pursued the solution for that yet.

The Orion Accufocus meant I easily achieved focus with the 350D when I otherwise would have taken a while longer, and was able to tweek it later very easily. Without it, I was having to walk back and forth from computer to scope, make manual adjustments I hoped was right, lock the focuser between each adjustment (heavy camera) which introduced some semi-random movements every adjustment, etc. Again my back neighbour and his wonderful workshop came into use with him constructing an alluminium bracket and brass bush to attach the Accufocus to the Megrez.

A fellow amateur astronomer was kind enough to give me his broken Telrad. I've mounted that on my Megrez using cable ties (not quite sure what to do there in the long term).. and I fixed it by replacing the broken glass with a piece of a CD cover.

On the software front, I installed the new ASCOM 4.1 release that includes the new communication for the Gemini Level 4. I'm not sure how much difference that is made, it did successfully connect and move the telescope with the old (2.something) version. I'm yet to work out this new version, it seems to reset the Gemini's settings when it connects, destroying the pointing model and other parameters like screen brightness, slew speed, etc.

So, to summarise I have:
- Reverted to drift alignment
- Bought scope rings for the guide scope
- Bought an Orion Accufocus for the Megrez
- Using a doubler on the guide scope for longer focal length guiding.
- Installed new ASCOM runtime so it's compatible with the Gemini L4 software.

A few pic's attached.

The saga continues....

A few things from last night that I need to work on:

My DEC worm gear is "sticky" again, after several attempts at being told to move it will suddenly jump/skip a significant amount, infact outside the search area for the guide star which messes everything up. I've adjusted the worm before, not sure if adjusting it again will solve the issue or if balance was slightly out, or if I need to re-grease it or something.

I still have some drag/delay in RA and DEC movements, in that after telling it to move it will take a while to stop moving. Doesn't seem to happen when GuideDog is moving it in Photo Mode but does happy at 2x Sidereal.

It'd be nice to fit the Telrad somewhere else where I can view through it at a closer distance. But the whole setup is quite crammed as it is.

I still have limited understanding of why the Gemini Polar Alignment Correction and Polar Alignment Assist are resulting in an incorrect alignment, and what all the Gemini parameters (in Show Information) mean.

I'll continue plugging away at it.

Roger.

[jase]

Hi Roger,
What you are doing is the "Gemini Way" by using the drift method. The Gemini Polar Align Assist is simply an automated drift method process. Once you get close, you can optionally use the Polar Axis Correction (PAC) feature to get you a little closer. Don't expect to be able to use PAC straight away when you've just set up.

Predominately you should focus on the A and E figures. The other measurements can be used to optimise your set up further. However considering you are setting up and tearing down every night, there are a lot of changing variables. It's different for a permanent set up. I've spent some time manipulating these figures like "CF" by moving the counterweights further up the shaft while still maintaining good balance. Moving the worm block for FR and FD. There are many resources available on the net to optimise losmandy mounts.

I assume that every time you run PAC and make an elevation or azimuth adjustment you know that you must redo the pointing model. Straight after you made the changes, just do a cold start and start a new pointing model. Once you have a new pointing model, you can run PAC again to get closer if desired. I've ran PAC three times to average out seeing, rebuilding an accurate pointing model each time. PAC is only as accurate as your pointing model, which brings me to an early post you made. You mentioned that when you slew and center a start for alignment, the mount appears to over shoot the mark when pushing the controller button. It kind of drifts and looks like there is a lot of play in the system. I experienced this too, but only when in visual mode. I would highly recommend you change to photo mode when building the point model. This should resolve what you are experiencing. Alternatively use "all speeds mode". Though I've only used this mode in v3.x, not 4.x.

I had a look at the photo you posted. Is this raw, i.e. no post processing other the dark frame substracted? The stars look reasonably round to me, even when magnified.

I think you're on the right track.:)

[[1ponders]]

Roger are you aware that if you are using the hand controller to move the scope if you push the opposite button after pressing the first Gemini will jump up to the next slew rate. ie Photo>center or centering >slew. This might help to make your centering quicker.

[Lee]

Great hint that - I wasn't aware of that - I thought that hitting the opposite button always made it slew..... thanks.... :D

[rogerg]

Ahhh. Now that you mention it, I remember reading that a long time ago. I had the same understanding as Lee, that it just sets it to slew. I will be experimenting with this!

I guess this is how I could set it to Photo Mode, and do my alignment using that .... I was wondering how I could use Photo Mode for alignments when it moves at 0.8 siderial!

Thanks guy's,
Roger.