Problem Getting PEC PMX

[PRejto]

I know there have been a few posts about this here in past months but I'm not finding those posts easily.

It seems that no matter what I do I cannot improve PEC on my PMX. My results seem to always worsen PE. I have done the following:

1. Camera is within 2 degrees of position angle = 0, ie, X axis is aligned with RA.
2. Turned off protrack and I am very well aligned in PA (few arcsec)
3. collected data close to zero degrees dec, near meridian
4. calibrated autoguiding in CCDSoft, then turned off corrections in X and Y
5. collected 10 min of tracking data in .5 sec exposures
6. measured PE in TSX as 2.2 to 2.4 arcsec uncorrected (depending on which night I have collected data)
7. generate PE curve, saved to mount. I have done this for both West checked/unchecked
8. measure error with PEC enabled.
9. cry

I have tried for 3 nights with zero success. My image scale from plate solves is .54 arcsec. I could try binning 2x2 (1.08 arcsec) and longer exposures. Is my problem that I'm just chasing seeing? Would longer exposures average out seeing? Or, say if I collected 20 min of data would the software be better able to extract the true PE curve and possibly be less effected by seeing?

My uncorrected PE seems very good, but it looks to be a quick repeating cycling through of the pinion gears that waves up/down within 2.4 arcsec. In other words, two different curves, one slow and one rapid superimposed over the slow curve. I wonder if the mount is actually able to correct for the pinion error? Is the change too fast? I will attach a photo of the raw data for PE.

Any help would be much appreciated. I used the mount and my TEC140 successfully at f7 and got pretty good stars, but now at f14 I just cannot guide out these errors.

Thanks,

Peter

[CDKPhil]

Hi Peter,

Have you tried collecting the PE data using Sky X rather than CCDSoft?

I don't know if this will make a difference, but it might be worth a try.


It could be something to do with the latest builds of Sky X.
The last build for Mac has made Sky X unusable for me, it has created a whole lot of problems that weren't there three builds ago.

Cheers
Phil

[Mighty_oz]

I know that they recommend at least 4 or more turns of the worm > 16mins i think, the more the better the data ?

[PRejto]

Thanks for the replies!

I've got an ONAG on the scope so I might try collecting data into two programs at the same time - from both the guide scope to TSX, and the G2-8300 to CCDSoft and compare the results.

The manual I'm reading says min of 10 min so I assumed that was 4 turns of the worm. But I guess the number of turns is indicated on the graph by the vertical lines (?), so I might have only collected 3 turns. I will certainly try more.

So, question. Is it possible to correct 2 arcsec PE error collecting data when seeing might be 2+ arcsec? r, is one bound to wait and wait for those rare steady nights?

Peter

[CDKPhil]

According to SB their software is supposed to average out the seeing and you should be able to achieve sub arc second PE.

But if your seeing is over 2 arc seconds is there any point in having sub arc second PE?

My uncorrected PE on the MX is around 3 peak to peak so +- 1.5
I trained the PEC but it did not make a lot of difference, I put it down to the seeing conditions.
I will have another go once the current problems are sorted with Sky X. I will keep you informed.

My image scale is .6 arc seconds per pixel, I still managed to achieve 10 min unguided without PEC.( That was with a good TPoint model and Pro Track.)

Cheers

[PRejto]

Hi Phil,

I can't answer your question. I guess I actually don't know what the problem is. I used to be able to guide just fine at f7, but in spite of quite a good model, excellent PA, and Protrack have never had good unguided results. Now at F14, same scope, weight, PA, etc, I just get erratic guiding, or maybe it's something else? Guiding will sometimes look excellent on the graph (say under .3 in TSX) and then it will suddenly start spiking upwards of 1 pixel or more in RA. Maybe that is just seeing, but usually it just comes and goes. Sometimes changing stars helps but more often doesn't. I was advised to try longer exposures to try to even out the seeing and lower aggressiveness. That helped some, but the longer exposures seem to result in distorted stars (6 seconds). Sometimes the stars are not so bright through the ONAG and actually need the longer exposure....so, I figured that if I improved PEC maybe my luck would improve. I guess the bottom line is I don't really have confidence in myself to know if it's my technique that is lacking, or if there might be an actual problem with the mount. I know this is a challenging hobby, but after more than a year at this I had hoped (in vain) to be further along. Sorry for the little rant. I'm just not sure how to sort through these issues. Any ideas appreciated!!
Peter

[gregbradley]

There was a stage when the Sky X was having trouble with PEC. I remember early on I could not get PEC to work or load.

I was advised to use the latest build for the Sky X. That worked for me.

I suggest you have the latest build of the Sky X. Make sure its good seeing.

You also need to remove the hand controller.

Greg.

[CDKPhil]

When I guide, I watch the graph and it is as you described. it will go from close to zero to over 1 sometimes 2 pixels. But I would expect this with the seeing I have here in Queanbeyan. Also imaging at .6 arc seconds per pixel every fluctuation in the atmosphere looks huge.

I haven't done any imaging in the past two months because I have been away.
The last image I did was a twenty minute guided exposure, and I remember watching the graph and it was fluctuating all over the place. The end result was quite acceptable.

What do your final images look like? are the stars eggy?

One thing, when you are capturing your PE data does the guide star stay well centred or does it drift away?

Also as Marcus has said the longer the better, I use at least 20min worth of data for PEC.

Cheers

[gregbradley]

You mentioned you have tried with both west or east clicked on but generally if PEC worsens it means its pushing when it should be pulling.
So the curve is upside down. Perhaps this is a build issue that got corrected or perhaps there was some other bug on PEC but at one stage for sure PEC was bugged in Sky X.

Tracking my AP140 (similar focal length) with a MMOAG and SBIG STi guider I get guide errors of around .1 to .6. Typically under .4 and sometimes under .2.

2.0 would be huge and would result in eggy stars. The occassional 1.0 isn't so bad.

I am using 5 second guide exposures and aggressiveness set to 4 and CCDsoft.

Greg.

[PRejto]

Thanks Greg....I've pretty much always run the latest daily update and the hand controller is in a drawer somewhere!

Thanks,

Peter

[PRejto]

Phil,

Here is one of the only nights that has kind of worked for me. 10 7 min subs. The next night the seeing was better and I couldn't get anything acceptable. This is just a combine in CCDStack with some deconvolution:

http://www.pbase.com/prejto/image/150070295/original

Capturing PE data I have no problem staying in the guide window. In ten minutes it has hardly moved. I should easily be able to get 20 minutes so I will try that for sure. And, thanks for telling me of your guiding experience. At least I now know I'm not seeing something too out of the ordinary!

Peter

[PRejto]

Hi again Greg,

Yes the TEC140 would be similar to your AP140 but I'm using a 2X AP barlow, so close to 2000 mm. I have mostly been guiding through TSX but I may try reverting to CCDSoft. I do like the graphs in TSX and miss that info in CCDSoft. But, with all the recent reports of buggy behaviour and crashes in TSX of late I think I will try CCDSoft again. I am only using it to collect PE because my main camera (Moravian G2-8300) runs much better in CCDSoft than TSX. I will try your settings in CCDSoft. Many thanks!

Peter

[CDKPhil]

That is a great image Peter.

It is strange that you could not reproduce this the following night.

I sent you a PM if you want to give me a call tonight or tomorrow feel free.


Cheers

Phil

[Paul Haese]

I found that I had to do images at 0.1 seconds and over 25 minutes. I don't think that graph looks right to me. Can you check to make sure the camera is pointed to 0?

[frolinmod]

Your raw PE looks odd to me. Here is what mine looked like when I measured it last year (using CCDsoft and an older version of TheSkyX).

[Joshua Bunn]

Peter,

Have you tried checking the "the data was collected when the scope was pointing west" check box? not having this correct will double your PE

Josh

[gregbradley]

Your image scale is .57 pixel per arc sec not .54. I am not 100% sure with the Sky X if it automatically takes into account binning (I think it might) but if you are using 2x2 then that may be one source of error and your image scale would be 1.14. I know SB Precision PEC did not take into account binning.

The curve seems too large. Mine on both PME and PMX is very small and only a bit above and below the centre line. This could also be a result of a wrong image scale being entered ie. not taking into account binning.

I did use a 20 minute run on a night of good seeing (most nights the seeing is good at my dark site, sometimes its exceptional, rarely poor, occassionally its just OK). The manual does not say to do 20 minutes though so that would only help not make or break it.

Your image though looks fantastic. At 2 metres everything does get exaggerated. With my CDK17 guide errors are usually much more than AP140 on PMX gets. But I get round stars every time. As pointed out 2x focal length of autoguider (not scope). You are using an OAG right, I think you mentioned that? Another possibility is flexure. How stable is that OAG? I had a look one on the net and it had knobs and adjustments everywhere and seemed huge. Can you just put the guide cam in the eyepiece holder of the scope without all the OAG stuff?

Also worth asking, in the pictured graph you do not show the apply corrections box as ticked in the top right corner. That needs to be checked for PEC to activate on the mount otherwise it does nothing.

Greg.

[PRejto]

Thank you all for your help!

Greg, I'm not sure where you are getting the .57 arcsec figure. If you plate solved my M83 image that image was taken with the barlow at a slightly different distance from the CCD. The photo below, taken at 2x2 binning, was taken just before the PE run I posted in my first post. When I collected data I didn't bin.

The plate solve shows 1.08 arcsec at 2x2, and it shows a position angle of 2 degrees 57 min from North. The MX manual states to have the camera within 5 degrees. Am I incorrect about this?

Yes, when I measured error after saving the curve to the mount he box was checked! And I did clear the previous curve before saving.

Josh, I did save the curve with the west box checked and unchecked, and measured hoped for improvement in both situations.

Paul, I appreciate hearing that you used such short exposures over a long period of time. It does seem clear to me that I have not collected enough data and this really gives me something to work on. It shouldn't be too hard given I have very little drift while collecting.

Thanks again everyone. Your help is greatly appreciated!! )Please let me know if I've got the camera positioned incorrectly by looking at the plate solve. That would explain everything!)

Peter

[Joshua Bunn]

Your Position Angle is OK. Here (http://www.bisque.com/sc/forums/t/18394.aspx) is a link to some guidance on creating a PEC log for the Paramount from SB.

Josh

[CDKPhil]

That is a good link Josh,

Jonathan explains the east west check box very well.


Cheers

[gregbradley]

[QUOTE=PRejto;977206]Thank you all for your help!

Greg, I'm not sure where you are getting the .57 arcsec figure. If you plate solved my M83 image that image was taken with the barlow at a slightly different distance from the CCD. The photo below, taken at 2x2 binning, was taken just before the PE run I posted in my first post. When I collected data I didn't bin.

The plate solve shows 1.08 arcsec at 2x2, and it shows a position angle of 2 degrees 57 min from North. The MX manual states to have the camera within 5 degrees. Am I incorrect about this?


Hi Peter,

I just used Wodaski's CCD calc and plugged in TEC140, the size of the camera pixels, the number of camera pixels in both directions and the 2X barlow. It gave me 1.14 arc secs. But your barlow may not be exactly 2X. I wonder if that plate solve is dead accurate or if the CCDcalc is.
It doesn't sound like much of a deviance either way.

Greg.

[PRejto]

Well, I wish I had better news to report! Another frustrating night. Issues with TSX continue. It crashed running the ST-i, had trouble plate solving, and still has strange file opening issues. The St-i crash occured trying to take .1 sec exposures. It crashed after 3 min. I rebooted and was able to take 12 min of data at .5 sec exposures.

Josh, that link to Jonathan's post at SB was very good reading. Unfortunately it doesn't look like I made a mistake as best I can tell. But, tonight I decided to change camera, and use TSX rather than CCDSoft. I carefully positioned the ST-i to within 1 degrees from North, and plate solved it as .75 arcsec. I was careful to have the position angles as "zero" with the scope pointing West, the same side I collected data.

Anyway, my measure PE is 2.2 arcsec peak to peak. I saved the curve to the mount, enabled PEC and collected PE again. PE increased. Just to waste some more time I redid the curve with West checked, replaced the correction curve, re-measured PE and it was even worse (as expected!).

What I notice is that the rapid oscillation (pinion gear?) was smoothed out a lot, but that the gradual error remains and is increased. I don't get that. It seems to me that if one is fixed the other ought to be as well.

I'm not sure at all what to do next. If it's something obvious that I am doing wrong I just can't see it. Reaching for anything, could it be latency in my USB cables? I'm running active cables just a bit longer than the recommended length. Or maybe TSX is messed up?

Peter

PS Yes, I see that the plate solve I've posted says .74 arcsec. 5 previous solves rotating the camera all said .75 so maybe the focus shifted a tad? I can't see that as the issue.

[Joshua Bunn]

Peter, Do you have the latest builds and drivers?

If you havent already, i would also put this issue to the SB support group.

edit, i see you have.

Josh

[PRejto]

Thanks Josh...Yes I am running the build released just yesterday. I had high hopes for that build given that the past few builds have been "difficult" but alas it seems to have the same issues.

Peter

[gregbradley]

You're using the STi for the PEC???

You should be using your imaging camera or if you are using STi your image scale would be way off. Its a function of focal length, pixel size,
aperture and sensor size. That image scale was for your 8300 chipped camera not an STi.

Greg.

[PRejto]

Well, why not? I plate solved the ST-i and got .75 arcsec which is what I used to compute the new curve posted above. My G2-8300 won't run reliably in TSX through ASCOM, but the ST-i does without issue (except for a possible problem with the current TSX build). In fact, I feel it is rather independant verification that I got an almost identitcal result to a curve I posted at SB (not the one here) that I did with my G2-8300. Both show error of 2.2 arcsec. One curve is inverted because that time the camera was at 180 instead of 0 degrees PA, but he cycle looks pretty much the same. Anyway, I wanted to collect guiding data in TSX to rule out any possibility that CCDSoft might be at fault.

Peter

[gregbradley]

Fair enough. My comment was directed at the original post that showed a different image scale. I thought you've been using the STi for all these PEC runs in which case the obvious thing would be the image scale was incorrect.

Greg.

[PRejto]

No worries!! Certainly with all these posts it is hard to keep in mind all that is going on or changing. I always value your comments! So, many thanks!
Peter

[PRejto]

More info gathered last night. Possibly something is emerging here, but not sure. I received some feedback from another MX user in the USA that advised me to not shoot such short exposures. In fact he said that such short exposures may introduce some issues of latency in evaluating just when the picture was taken vs the actual worm position. I know this goes against some advice and actual result also presented in this thread, but I though there would be no harm lost in trying out more delay between exposures.

Last night I collected data with .5 sec exposures and a 2 second delay. The curves are compared in the attached photo. Whilst there are certainly similarities between the two curves, there are also obvious differences. The differences that concern me are the differences in the start and end points of the "cycle." Is this significant? A cycle is a cycle but not if it is misidentifying the position of the worm vs corrections. To me that might explain why the error corrections are not working. Also, comparing the actual PEC curves from the 2 nights is really odd. The camera orientation was unchanged between the two nights and in both cases the west option was not selected. It's really clear the the start point of a "cycle" has shifted dramatically.

What do you think? I've posted the same query at SB but no reply yet.

Peter

[gregbradley]

I can see if you were too fast you may be exceeding the speed of the system to save the results perhaps. I never have used such short exposures. You must have been using a bright star. I think I used something like 2 or 3 second exposures.

I reread the PMX manual on PEC. It does state for PMX to record at least 4 worm turns which is 15 minutes and 30 seconds (Page 98 of the manual).

The manual tends to contradict itself a bit saying that PE errors below the local seeing are lost in the noise and PEC makes no difference below that seeing level. Later it says a powerful algorithim can work out PE through the noise. I take it then that longer the better for this algorithim to see through the seeing noise and that would be a minimum of 15 minutes 30 seconds. Last I did mine I did 20 minutes and around 1-2 second guide exposures (I may've used 2x2 binning as well).

Autoguider log has to be deleted before you start a fresh PEC curve.
All guide cables removed and no autoguiding is done during the PEC run. I take it this all being done.

It sounds like your best bet is to do a 20 minute run or longer with longer exposures, no delay and wait for a night of good seeing to do it.

The alternative is to use PemPro.

Greg.

[Joshua Bunn]

Peter,

Here is my take on this.

The two cycles in the photos look like they have the same sine wave curve but out of phase with each other. Personally i don't think this is an issue, its just a result of where the worm was at when the PEC log was started.

Josh

[PRejto]

Hi Greg,

May I ask why you say "no delay?" Are you saying that a short exposure plus delay on a brighter star is somehow different than a longer exposure on a dimmer star? I supose the longer actual exposure might average out the seeing some compared to the short exposure plus delay.

In any case what I find confusing is that I have generated two curves that are certainly similar. One from the short exposures and one from the short exposure + delay...so it seems they roughly agree. Except, when I generate the PEC curve and especially when I save the two curves to the mount they look remarkably different! I took these pictures by connecting to the mount but the mount was not homed or tracking. The vertical line seems to indicate where the curve is being read and determined by the RA. I would have expected to see similar parts of the curve being read, but they are not. So, naturally I wonder iof something is going wrong (assuming I have not made some glaring error!)

Peter

PS Using CCDSoft it is necessary to delete the autoguider log, but it seems in TSX that a new log is started every time guiding is started so there seems no reason to delete or rename. I'm using direct guide so there is no cable to remove, and naturally I have deselected actual guiding!

Thanks for helping me think this through!!!

[Joshua Bunn]

Peter, sorry if this is insulting, but are you checking the "apply PEC Corrections" checkbox. its just not checked in your last images?

Josh

[gregbradley]

The reason I would say no delay as you are weakening the sampling of the PE data by introducing a delay. Look on the taking of the PEC data as a sampling of a system so if you put a delay between samplings then it becomes lower resolution right? Likewise, you wouldn't want a 5 second exposure to record the PE as the data would be 5 seconds apart at a minimum (plus download time, plus the time to save it so more like 6 seconds plus). That's a pretty big gap in the data. Perhaps this is a jig or a jag in that time that gets missed in the recording process and so never gets corrected in the PEC file. If exposures are too short perhaps the software has difficulty in spotting the centre of the guide star if it is too dim. Too long and there would be holes in your data. I know its smoothed later so perhaps not such a big deal but looking at it from basics it seems there would be an optimum exposure and sampling rate for the data to be collected. What that rate is would be the exposure time where the data is clear, matches the download/save/computing rate of the system. So 1 second you would think should be close to that. Perhaps 2.

Pempro goes into PEC curves a bit more indepth tha SB so I suggest you look at their site and do a trial on their PEMPRO. It is quite specific in its requirements.

Greg.

[PRejto]

Yes, of course!! No insult taken!!!

[PRejto]

Hi Greg,

I kind of get what you are saying, but still I can't see how an image every 2.5 sec is different from an image lasting 2.5 sec given that both only produce 1 sample in a given amount of time. But, I agree that a 2.5 sec exposure would sort of average the star location over the 2.5 sec interval....but still only give a single averaged point in time.

Anyway, enough. I am currently going to do this yet again on a dimmer star with 1 sec exposures!

Thanks,
Peter

[CDKPhil]

Hi Peter,

The worm has an index scale 0 to 999. If you open a guiding log with a text program you will see the RA index. This will have a number from 0 - 999 depending on where the reading was taken in the worm cycle. See screen shot 1.

This information when loaded back into Sky X generates a PEC Table which is then loaded into the mount. The PEC table is a list of numbers from 0 to 999 with a + or - number next to it. The +- numbers are the amount of correction that is applied. Screen shot 2.


What concerns me is that you PEC tables are different. It should not matter where in the cycle the readings begin because they have to correspond with an index number. So if you have an error of -2 arc seconds at index point 50, next time you take a reading index point 50 will still have the same error.
If you look at the two pictures that you posted of the PEC Tables, the index reading is 101. The values at index 101 are different in each table. They should not be different. Seeing conditions will alter this a small amount but your PEC tables should be similar.

Did you by any chance get a copy of each of the PEC tables?

You can easily compare them side by side in a text edit program.

To me the problem looks like the software is not recognising the index points and is loading a PEC table that does not correspond with the index error in the worm.

Hope this makes sense, I am out in my dome and it is just on zero my fingers and brain are not working to well. :lol:

Cheers

[PRejto]

Hello Phil,

Thank you for that explanation. You have confirmed my suspicions exactly! I just didn't know how to describe what I was seeing in comparing the various curves I posted, and - if something is wrong with the way the worm position is reported vis a vis correction curve - it explains why I cannot ever succeed in getting a PEC that actually works.

I must confess one other thing I "discovered" last night that is a bit embarrassing. I suddenly realised that I had been turning off Protrack, but not disabling T-Point corrections. (However, Jonathan posted at SB that this was possible "overkill" and unnecessary.) In any case, as my last (and also failed) run last night I did turn it off and got a very different curve with only 1.6 arcsec peak to peak that looks to be nearly all pinion error. This curve also fails to give any correction....in both ways to save the curve the PE increases about double. So, perhaps it wasn't my problem, but I'm quite surprised to see such a large change in the curve. I was under the impression that T-Point improved pointing ability, but I didn't know it also (seems to) influence tracking. I though just ProTrack did that. Perhaps you can enlighten me about this???

Anyway, this curve was generated with my ST-i at .75 arcsec for 21 minutes.

PEC tables posted for May 16 & 17. They are totally different!

Thanks for your help. And, yes it sure was cold last night!!

Peter

[kimrichards]

Peter,

I had the same issue and have placed a suggestion on the SB forum today.

I think as we are trying to correct an error that is almost certainly smaller than the seeing the computation of the PEC is struggling. I believe although the magnitude may be about correct the phase is out which is why you get the varied residual PE.
In my reply I attached a test I ran that shows how far the computed phase can be out even if the raw data is in sync.

What I have found is you can dramatically improve the result by running the PE measurement for considerably longer. I suggest for at least 30 minutes. This seems to enable the software to better tie down the phase of the correction.

Hope this helps

Kim

[PRejto]

Kim!

Thanks so much for your report. I tried to attach it here but unfortunately IIS has restricted the size of attachments...

Your experiment and results do seem to be very similar to what I am experiencing.

I'm curious as to the length of guiding runs you would do to verify if PEC is working? I've felt it might not be necessary to go as long as when measuring PE. Do you think that is a correct assumption since one would only be looking at peak to peak and the phase wouldn't matter?

I just tried this again. I did a PE measurement of 30 min and another of 44 min. I couldn't keep the star in the guide box past 44 minutes. Unfortunately neither curve works. But the phase difference between the two curves is remarkable! I wouldn't have expected such a big change from two rather long PE runs.

What was your end result chasing this down? Did you finally succeed in reducing your PE and by how much? Did you do something special or just get lucky one night and it worked?

One would think that some clever software could solve the phase problem following the 2nd measurement to see if the correction worked. It would just be a question of seeing where the correction had been applied vs where it should have been applied.

I'm really starting to wonder if I should just try Pempro. Maybe it doesn't have this phase issue to the degree I'm seeing.

Many thanks again!

Peter

[kimrichards]

Richard,

I ran another test last night and it looks as though you were right it was just luck that the phase was correct!

So the problem definitely seems to be that the TCS software is not picking up the index correctly.

Just to confirm this can you open the text files of the two long PE runs you made and read what is the index for the maximum positive error. Is it the same for both runs, does it match either of your "Periodic error curves for Bisque TCS"?

One thing for sure the two curves you made are incredibly similar in shape so if applied correctly the residual PE should be amazingly small!

Regards

Kim

[cfranks]

I'll second the recomendation for PemPro. With it, I set my MX system up in 1 night including a more accurate polar alignment than with the SB/TSX procedure. I haven't run an accurate test but have since managed unguided images of more than 5 min exposure with a WO FLT132.
Charles

[PRejto]

Hello Kim,

I greatly appreciate your further investigation. It really confirms that something is happening that ougtht not to be happening.

I'm not able to tell from the guiding logs where the high or low points are (at least not the log generated by TSX. The CCDSoft log is easier to figure out) but the raw data certainly shows the phase difference between the two curves (which I have posted below).

I'm thinking about an experiment where I have the TCS window open and watch the index number. When it gets to the very end of the cycle I would start guiding, and then stop guiding on a specific number. An examination of the guiding log would show if the same numbers were being logged as those shown in the TCS. I'm pretty sure they would be.

That leads to the question of whether the numbers seen in the TCS really corespond to the worm position? Could a long cable run lead to some sort of latency where the worm is actually more advanced than what is logged?

Charles, I am ready to try Pempro and I'm glad to hear of your positive experience. Would you share what your uncorrected/corrected numbers are? Unfortunately my trial version has expired. I never got to test it months ago due to a camera incompatibility. It would be an expensive experiment particularly as I've had good luck with T-Point and most likely wouldn't use the alignment method either. Still, if it works I could move on from this endless frustration.

Thanks,
peter

[gregbradley]

Peter,

Clearly the PEC is bugged and is not working. I would try Pempro. I know Chris Venter did this when he hit a wall with SB PEC and it worked fine.

PEC did not work on my PEC on the first few goes. I updated with a later build and it worked. I did a 20 minute PEC run done in good seeing at my dark site.

Sometimes later builds cause things that were fixed to unfix. Not sure if this is one of those cases.

The PMX is a great mount but it really is a bit of pain in the a...

When it works its great, but its fussy, a little temperamental and a little fragile. I lightly bumped into the counterweight shaft the trip before last. It had been guiding beautifully on the 2 nights preceding. I started getting backlash and oscillating corrections (large positive to negative swings). I knew from having this happen before the tensioning screw must have been loose.

I found the cam pin had popped up and was loose again. Once reset it all worked again (3rd or 4th time I have had to adjust it). So PMX is weakly engineered in some regards - lovely when it works but too fragile. Should have gotten an AP1200.

Greg.

[kimrichards]

Hi Peter,

I put your two PE curve quickly into Excel and both curves suggest a maximum positive error around a value of 300 for the RA index. So the data you collected is definitely consistent. So this is not an issue of acquisition just the interpretation of the data by Bisque TCS.

On the mount this max error should correspond to the maximum negative correction at an index of 300.

I loaded both your curves to my mount and as you can see they are completely out of phase and either side of the target of 300.

I think this proves beyond doubt that the problem is the index is not being picked up correctly by the Bisque PE calculation, probably when the "FIT" is made.

I put this on the SB forum so lets see what they come back with.
On the positive side the uncorrected PE is incredible for both our mounts and the consistency of shape between your two PEC curves suggests if the phase was correct the correction would be very good indeed.

Regards

Kim

[PRejto]

Hi Kim,

Many thanks for your analysis, and for posting at SB. I hope this gets some attention!

Would you please explain how you are able to "know" when loading these curves into Excel where the worm is in the cycle? If the data of the worm position is incorrect in the guiding log how would you know what the correct index is?

Many thanks,

Peter

[PRejto]

Hi Greg,

Thanks for your comments. I certainly will go to Pempro if SB doesn't offer up a solution soon!

My experience with the MX has been difficult but I put that mostly down to my beginner status with an overwhelming amount to learn from the start. I suppose the journey might have been easier with brand AP, but I'm not yet at the point of wishing I'd made a different choice. Hopefully the bugs will be rectified. Hope springs eternal!

Peter

[kimrichards]

Peter,

I am not sure I understand exactly your question but this may cover it.

The recorded text file includes the RA index for each point. So if you plot the RA index against the PE error you can see at which index values the error is a maximum.
I previously used the maximum positive error but the maximum negative error might be clearer to see on the excel sheet.
In both cases the maximum negative error is very close to 600 but when loaded to the mount the maximum positive correction is applied at about 800 for A and about 100 for B, not at 600. (The horizontal scale on the mount plot being 0 to 1000.)
Based on this my assumption is the error in the phase is made in the making of the correction curve not during the acquisition.

Regards

Kim

[PRejto]

Thanks Kim, I get it now. I misread your earlier post and made up something you actually didn't say!

Peter

[kimrichards]

Peter,

This may be a coincidence but have you noticed all our PEC curves when loaded to the mount start with RA index zero and zero PE correction?

It is as if the curve is being shifted to start at this point instead of at the error corresponding to RA index 0.

Hopefully we will hear from SB soon.

Kim

[PRejto]

Nothing much from SB yet so I tried Pempro last night during a lucky break in the clouds. Remarkably I got my first positive result. My measured PE in Pempro (same camera, resolution, same everthing except using Pempro instead of Bisque TCS) measure my PE as 2.6 arcsec peak to peak (vs 2.2 in TSX) after 9 worm cycles in not great seeing. After applying the correction it is now .7 arcsec peak to peak.

Reasoning that there can only be one correction curve that "works" it seemed possibly interesting to compare results from TSX to Pempro and see what the differences might be. I used data collected a few nights ago, a run of 44 min and compared it to the Pempro results from last night. The 44 min data was collected with a position angle of close to zero with the telescope pointing west, as it was for the data collection. Therefore the "west" selection would normally not be necessary to check (which flips the data vertically).

#1 just places the two curves on top of each other
#2 Better fit with large phase shift.
#3 Bisque curve flipped vertically. Shows phase error, possible match but there are obvious differences in curves.

If this analysis is correct there are two possible problems with the TSX PE calculation. Something is causing the data not to align properly with the worm index, and there might be something not correct about the use of the "west" selection. (though I think the fit is better with the curve not flipped vertically which would mean the major problem is that the curve is just out of phase with the true worm position).

I will be adding this to the discussion at SB.
Thoughts?

Peter

[kimrichards]

Hi Peter,

Excellent I think it again shows clearly the problem of phase shift.

I would put it up on SB for two reasons, one it supports our analysis and also shows a competitor software working.

Kim

[CDKPhil]

Good to see you have something positive for a change.:lol:

I would post that data on the SB forum, it is more proof that there is something wrong the the way SkyX calculates and imputes the PEC table.

I was up till two last night and played around with the North and Southern config. But I still have not found any way to get Sky X to correct the PE.
I posted this info in your SB thread.

I did a test with ProTrack on and no PEC, this gave me a better result than when the PEC is activated. (image below)

It must be a Southern hemisphere thing, I don't see any Northerners posting anything about PEC problems.


Phil

[cfranks]

Hi Peter,
I'll have to set up my system again to get those figures. Hopefully, the weather will clear soon. I do remember that the RMS error after a TPoint run got to less than 4.
Charles

[CDKPhil]

Peter,
Did you load the PEC table from PEMPRO into Sky X ?

If so, did you do a tracking log with the PEMPRO's PEC table activated so you could compare the PEMPRO graph to the Bisque TCS graph.?

This would show the difference using SKy X, SB tends to respond better when the evidence is shown in their own software.

Cheers

[kimrichards]

Phil,

I can't get my head around why North or South hemisphere should make a difference but it looks that way.

I can't get to my mount for quite a while but what happens if you fit and produce the Bisque TCS PEC curve from one of your uncorrected PE runs then clear it change to Northern hemisphere then reload the same file not changing anything else?

How do the PEC correction curves compare?

I may be wrong but should they not be identical? After all the PEC is just moving the RA faster or slower at a given index, as RA moves clockwise for us and for the North ant-clockwise, but we still want the same correction (with or against RA) at the same index.

Kim

[CDKPhil]

I will give that a try.

[CDKPhil]

The PEC tables are identical.

I don't know why the results of my test last night showed a difference.

Maybe, when in Northern Hemisphere config the index is being saved correctly?

I will have to do some more testing with this to see if I can reproduce the same results.

cheers

[PRejto]

Phil,

Unfortunately even though log guiding was selected in CCDSoft I think Pempro turns that function off when using CCDSoft's camera to gather data. I will just remeasure the corrected PE using TSX or CCDSoft when the weather improves.
Peter

[PRejto]

No worries Charles. I've got a fairly good result now using Pempro so knowing your numbers isn't too important.

Thanks,
Peter

[gregbradley]

.7 arc secs. Fabulous result. You got it going. SB PEC obviously is bugged. I'd give it the flick. Go PemPro! Perhaps I should get PemPro myself. I am only assuming PEC is improving my guiding on my PMX. Maybe it isn't. I think I'll do a test with and without it running after following this post.

Precision PEC generated curve is working with my PME, I know that.

Greg.

[PRejto]

Hi Greg,

Yes, I am happy to finally have a positive result. SB has all this information, now from 4 of us in the Southern Hemisphere but have not responded. I know they are probably flat out with some other major TSX bugs, but even to say "we get what you are saying and will be working on this" would be appreciated. Also, I have to say that TSX ought to work and it ought not to be necessary to use a competitor's software to get a result. But, I know they are not a huge company, and I think all of us South of the equator are their unpaid beta testers!

Peter

[gregbradley]

I agree, cut em a bit of slack as they do try and they are quite professional. A bit of this not working and that is somewhat acceptable a long as they back you up which they seem to do.

Pempro being a stand alone program was probably always the superior program anyway. Pempro has a fabulous drift alignment tool as well - not that you need it.

Greg.

[CDKPhil]

Yes I think they try their best.

Last night was a prime example. Software Bisque had remote access to my mount and my Mac, and spent quite a few hours diagnosing a problem with the latest build.

You don't get many companies that go out of their way to do that.

Unfortunatly I didn't get time to ask them about the PEC issues that we Southerners are having.

Cheers

Phil