×

INDI Library v2.0.6 is Released (02 Feb 2024)

Bi-monthly release with minor bug fixes and improvements

Re:Any obvious reason the Ekos PA Assistant would INCREASE alignment error?

  • Posts: 222
  • Thank you received: 20
So I was out last night, trying to dial in guide performance with my new used OAG. As usual, I polar-aligned my CEM-25P with the polar scope, then ran the PA Assistant in Ekos. It yielded a 9' PA error, which I thought was enough to correct for. So I clicked my vector-star and really nailed the adjustment to bring it dead nuts centered in the reticle.

And, as one does, checked the alignment again. 19 minutes.

???? I didn't trip over the tripod, have a loose adjuster, anything like that. Just align as it told me to, and the alignment error doubled.

Any hypotheses? I should've checked it via drift alignment at that point, but I was in the slot-canyon of my driveway so access to stars on the equator was limited indeed.
3 years 10 months ago #53776

Please Log in or Create an account to join the conversation.

  • Posts: 133
  • Thank you received: 33
Similar to you, I polar align with the CEM25P polar scope then use the PAA unless I'm lucky enough to hit sub 1 minute with the polar scope. Occasionally I've had weird numbers like you mention so I end up doing it over and things seem to work fine the second time. When doing the alt/az adjustments to get the star into the cross hairs I have on occasion managed to use too much pressure on a knob and the star really jumps and I'm not always sure which star it was I was actually trying to move. Aligning with the wrong star would definitely not be good for accuracy, Could it be you might have done that?
Did you get similar numbers multiple times?
3 years 10 months ago #53780

Please Log in or Create an account to join the conversation.

  • Posts: 1957
  • Thank you received: 420
There is an unidentified bug in the PA code somewhere that causes this behavior with certain mounts or for certain locations. Have you tried checking the "invert pa arrow" option that is in the polar alignment tab? Sorry, I am typing this off the top of my head and it is possible that this option is called differently but the checkbox is in the polar alignment tab right below the image window showing the image with the grid and the pink arrow. you need to be on the latest stable version of KStars (or the nightly) to have that checkbox.


HTH, Wouter
3 years 10 months ago #53784

Please Log in or Create an account to join the conversation.

  • Posts: 222
  • Thank you received: 20
I doubtless have in the past! This time though I'm certain that I did not. The stars streaked during movement and ended up in the next exposure right at the end of their streaks, so it all made a consistent story.
3 years 10 months ago #53785

Please Log in or Create an account to join the conversation.

  • Posts: 222
  • Thank you received: 20
Huh. I had no idea that was there. I actually built one from source last week, I'll try running that. It is suspicious that the alignment error doubled, and IIRC was in the same direction the second time. Of course, as soon as I start checking the box, with my luck, it'll revert to correct behavior and I'll still be doubling my error. :-)

I very definitely remember from a previous session clicking on a star and having the vector invert when it repositiones. But IIRC after I used the wrong-looking vector, then ran the PAA again, I would up within a few seconds.

Certainly worth a try. Thanks to you both!
3 years 10 months ago #53788

Please Log in or Create an account to join the conversation.

  • Posts: 133
  • Thank you received: 33
I didn't notice that before either, but then again I just updated to a nightly yesterday, been using a stable version for quite a while before that. When I tick the flip vector box I get double the error after adjustments at the mount. Leaving it unticked seems to work fine for me.
3 years 10 months ago #53795

Please Log in or Create an account to join the conversation.

  • Posts: 77
  • Thank you received: 1
I experienced the exact same Monday night with my HEQ5 mount. I’ve never experienced it before. I ydes the ASTAP solver, but everytime I moved the star into the middle of the crosshair my error had increased by 2-10’. I tried 3 times all with the same result. Then tried switching to the internal astronomy.net solver and suddenly my error decreased (that is, without making any adjustments to my mount!). One aligment routine later and my error was 11”. One additional run of the PA routine (just to check the error - so no adjustments made) again gave me an 11” error.

It seems my problems got cured by switching from the ASTAP solver to the offline astronomy.net solver.
SkyWatcher ED80 Pro
Skywatcher HEQ5 Pro with Rowan Belt Mod with EQDIR cable
ZWO ASI294MC Pro imaging camera
QHY5L-II-C guide camera on 50mm guidescope
DeepSkyDad AF3 autofocuser
Raspberry Pi 4 4GB running Kstars/Ekos
3 years 10 months ago #53801

Please Log in or Create an account to join the conversation.

Chris Rowland, Marks Wildi, and I are currently working on resolving this, so hopefully we come up with a solution soon.
The following user(s) said Thank You: Brian, Anders Misfeldt
3 years 10 months ago #53805

Please Log in or Create an account to join the conversation.

  • Posts: 222
  • Thank you received: 20
Thanks guys. FYI I was using astrometry.net offline when I saw this.
3 years 10 months ago #53844

Please Log in or Create an account to join the conversation.

Time to create page: 0.239 seconds