I read in your last post that you use the PEC from PemPro and not from SkyX.
My uncorrected PE is only about +/- 0.8 arc secs so smaller than the seeing noise. Although the recorded error curve looks good, when it is applied the PE sometimes stays about the same or more often gets worse, it never improves. I had put this down to seeing noise and some inventive interpolation by the SkyX and as I usually guide I just left PEC off.
However, I have recently tried some unguided runs and have found that ProTrack definitely makes things worse, presumably because no PEC is being applied, so I now question my previous assumption and looking at the PEC curves I am again questioning the phase of the correction.
So has anyone actually made a good PEC using SkyX for an MX mount in the Southern Hemisphere. The software fix earlier this year corrected the rotation error for the SH but I am wondering if it fixed the phase issues?
Kim, as they say, are you measuring PE with the latest build? A few months back I tried to measure it in Windows, after the apparent 'southern fix', but couldn't get it working (n.b. don't rule out user error, I often get this stuff wrong) so I resorted to Mac, which did work for me. MX corrected under 1 arcsec p to p.
Also, there is talk of a new 'Automated PEC Routine', expected in the next build. It may already be here? I sure like the sound of that. I do love TheSkyX, but there is no denying that the PEC calibration routine in Pempro is (was?) far simpler. Let's see how Auto PEC fares
After the alignment with Pempro, I ran the 180 ish image TPoint and the RMS was 4.3. The Model said 'excellent' for both axis and therefore I didn't touch anything. I'm currently re-doing the exercise as I recently removed the mount from the pier for maintenance and would have lost the fine adjustment.
Charles
Thanks Charles! It's good to know that both methods did agree in your case. My horizon is so odd that I suspect they will not agree. I just need a clear night.
Peter
Quote:
Originally Posted by kimrichards
Hi Peter et al,
I read in your last post that you use the PEC from PemPro and not from SkyX.
So has anyone actually made a good PEC using SkyX for an MX mount in the Southern Hemisphere. The software fix earlier this year corrected the rotation error for the SH but I am wondering if it fixed the phase issues?
Regards
Kim
Hi Kim,
Well, I have not actually tried TSX for PEC since I have such a good result from Pempro. I assume it works now but someone else will need to chime in. It is interesting that seeing seems to influence the amount of correction that either program reports from night to night. If seeing is average both will say my PEC is under 1 arcsec. But on an exceptional night a 15 minute test said my PEC was .2 arcsec. Perhaps that is unbelievable...but, from night to night the reports do vary.
I've always understood that to get good unguided tracking with Protrack one needed PEC, but I'm sure that is only because without it there would be too much error. On the other hand if your uncorrected error is so low it doesn't logically follow that Protrack would require PEC to be turned on. It just shouldn't need it. Of course I am speculating on this without proof. But say you had some sort of mount without any PE. It wouldn't stand to reason that Protrack would require PEC. Perhaps your T-Point model isn't as good as you think? Also, you might try waiting for 2-3 min before starting imaging after a slew. Some have reported that it improves things. Not at all sure why that should be so but might be worth trying.
Briefly, I ran a new super model where I restricted points to be eqidistant from the meridian E and West to minimize any potential bias due to my inability to see very far East. The super model differed from the the all sky super model substantially in altitude indicating that I should raise the mount 1.2 tics. This is 1 arc min different from the all sky super model of some 200 points. There was essentially no diffeence in the MA recommendation comparing the reports.
Before doing anything to the mount I ran Pempro. Pempro showed perfect alignment over 15 min of tracking in MA. ME, however, was off by .7 arc min also ndicating that I should raise the mount. I did in several moves and now have substantially better unguided correction than I've ever had since owning my MX.
Unfortnately I have very strange excursons in RA that may or may not be PE. Analysis of one guiding log says my PE = .7 arcsec (corrected). Then after I adjusted ME, the next log said my PE error was 1.8 arcsec. Maybe it's seeing or that I collected data at 1.56 arcsec, or that PEC isn't working as well as I thought. I attach the two guiding graphs for comparison. Obviously drift in both axis has improved quite a lot (Protrack was off!), but the huge excursions in RA don't make sense to me with PEC on (and previously verified numerous times to be working). Any ideas?
I ran out of time and enery at 2 am so this must wait. But, I'm happy to finally understand where T-Point has led me astray.
Sounds like PEC is making things worse. Is it the same result with PEC turned off? If PEC curve is upside down it worsens tracking.
There was a long thread recently about PEC in PMX and it was not working properly and it seemed to boil down to it was out of sync with the mount somehow. Perhaps that is what you are colliding with.
I got Pempro myself last week with the intent of replacing my SB PEC curves with a Pempro generated one. As I recall someone else did this several months ago and got improved results.
Its quite possible SB PEC is bugged or bugged for southern hemisphere.
Try a straight no PEC, Protrack off, 10 minute exposure and post the image. Then another with PEC on of the same scene.
I suspect unless you are very calculating and anal about how each of these is handled/created, you cant use guiding/protrack/PEC all at the same time.
Are you referring to Peter's mount or generally speaking? Im sure there are lots of users who use these 3 in combo without issues, me included.
Peter, I would strip back to the essentials here and just measure the PE without protrack and with the best polar alignment you can get with your choice of software or try the ccd drift method with the continuous exposure and getting the lines to run back on themselves. We can precede from there with confidence that there is no software influences.
That's right Josh. There was a thread posted here a little while ago with Thomas Bisque talking about this point.
PEC corrects for high frequency gear/worm errors and Protrack corrects for slower errors like flexure and refraction.
It seems to me its like the SBIG differential autoguiding where you have rapid corrections for the gear errors and then a slower one for flexure - same thing.
I definitely see a gain using a 330 point Protrack model in tightening up images with PEC on. Martin Pugh though mentioned in his talk to test the combos and for him he found Protrack on worsened. YMMV.
Are you referring to Peter's mount or generally speaking? Im sure there are lots of users who use these 3 in combo without issues, me included.
Peter, I would strip back to the essentials here and just measure the PE without protrack and with the best polar alignment you can get with your choice of software or try the ccd drift method with the continuous exposure and getting the lines to run back on themselves. We can precede from there with confidence that there is no software influences.
Josh
I put that wrong. Anyway, I suspect I'm wrong altogether so that post is gone.
I thought I'd best update the post earlier where I compared the two T-Point models and came to the conclusion that one of the models was incorrect, then used Pempro to drift align and finally got better polar adjustment, etc. Anyway, that post at SB generated several large responses from Patrick Wallace and he comes to a very different conclusion than I did. I certainly bow to the master here and feel well in over my head. Patrick has said that using Pempro to drift align just hides the flexure that is there. Yes, I might have a better result but the problem does remain.
Edit: I have deleted most of what I wrote because (again) Patrick has corrected my interpretation of what he wrote. He concludes that I do not have abnormal flexure and there is nothing to fix. The question seems to be about why Protrack doesn't give me the results I want, and why I have trouble guiding. These probably have little to do with polar alignment so I might have been looking in the wrong place for answers.
To be continued...
Peter
PS. Last night I redid my PEC with Pempro. From 2.4 PTP to .9PTP. Hopefully I can refine this even more. Seeing wasn't too great to be collecting data at .63 arcsec. The night before I tried using TSX to correct PEC. I couldn't get it to give a correction but I may have been too hasty and seeing wasn't as good as last night and my data was at 1.5 arcsec. Too many variables to draw any conclusion about TSX.
Haha, yeah, the original reason for this thread. thats a good point that Patrick makes - one that i overlooked. In that case, do you know if its the scope or mount? do you have another smaller scope you can mount and do some tests with that?
Never ending is it? All I wanted to ever do is take some nice phots and in reality all I seem to do 99% of the time is trouble shoot. It really is enough to make start thnking I made a bad choice 2 years ago. I'll just try to stop thinking like that.
Peter
hang in there mate - its character building . You will reap the rewards after this. Ive been trying to sort out some issues to, hopefully the fix i have in plan will fix it.
Patrick added more clarification worth reading. Seems I don't have a declination problem to fix. The question seems to be about my inability to guide properly and why Protrack doesn't give me the results I want and others seem to get.
I think I will leave my Polar Axis where it is, run one more large model (and ignore the PA report) and try more experiments with Protrack on.
Peter, to eliminate a few variables, have you considered going portable for a night? Rip your gear off your home/permanent setup, head out to a dark site with good seeing and appropriate footing and do a large all sky calibration run with a few hundred points from there. It would certainly rule out any issues with your home setup.
Not sure if you have a solid MX tripod, I know that Phil sold his recently. You're welcome to borrow my modified AP portable pier to test. It's built like a tank.
Peter, to eliminate a few variables, have you considered going portable for a night? Rip your gear off your home/permanent setup, head out to a dark site with good seeing and appropriate footing and do a large all sky calibration run with a few hundred points from there. It would certainly rule out any issues with your home setup.
Not sure if you have a solid MX tripod, I know that Phil sold his recently. You're welcome to borrow my modified AP portable pier to test. It's built like a tank.
Hi Logan,
Thanks for the offer. I've got a good tripod for the MX and just might do that. I'd need to figure out a power source first, then where and when. Lots of work but probably worth the effort!
. You will reap the rewards after this. Ive been trying to sort out some issues to, hopefully the fix i have in plan will fix it.
