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Troubleshooting lost guide stars

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I was asleep and didn't witness it. That's a good thing, right? Nevertheless, it seems I lost the guide star, or at least guiding just stopped working. Ekos aborted guiding and restarted automatically. Guiding resumed and the next image began. Also a good thing. But, I found my subs on either side looked like this:

I'm posting this both in search of ideas (below) and in hopes that others might benefit from ideas around troubleshooting guiding.

Properly centered:


Uh, what? Calculating the center of the two shows they're 0.20 degrees off from each other. Wow.


Checking the logs, I see this event directly between these two subs:
[2018-02-21T03:44:07.330 MST DEBG ][     org.kde.kstars.ekos.guide] - Received guide frame.
[2018-02-21T03:44:07.330 MST DEBG ][     org.kde.kstars.ekos.guide] - Tracking Square  QRect(22,4 32x32)
[2018-02-21T03:44:07.331 MST DEBG ][     org.kde.kstars.ekos.guide] - ################## BEGIN PROCESSING ##################
[2018-02-21T03:44:07.331 MST DEBG ][     org.kde.kstars.ekos.guide] - Star    X :  37.1411  Y  :  19.6493
[2018-02-21T03:44:07.331 MST DEBG ][     org.kde.kstars.ekos.guide] - Reticle X :  71.6676  Y  : 66.8336
[2018-02-21T03:44:07.331 MST DEBG ][     org.kde.kstars.ekos.guide] - Star    RA:  29.0457  DEC:  15.3665
[2018-02-21T03:44:07.331 MST DEBG ][     org.kde.kstars.ekos.guide] - Reticle RA:  56.0468  DEC:  52.2665
[b][2018-02-21T03:44:07.331 MST DEBG ][     org.kde.kstars.ekos.guide] - -------> BEFORE ROTATION Diff RA:  -27.001  DEC:  36.9
[2018-02-21T03:44:07.331 MST DEBG ][     org.kde.kstars.ekos.guide] - -------> AFTER ROTATION  Diff RA:  27.1894  DEC:  -36.761[/b]
[2018-02-21T03:44:07.331 MST DEBG ][     org.kde.kstars.ekos.guide] - RA channel ticks:  22  DEC channel ticks:  22
[2018-02-21T03:44:07.331 MST DEBG ][     org.kde.kstars.ekos.guide] - Processing Axes
[2018-02-21T03:44:07.331 MST DEBG ][     org.kde.kstars.ekos.guide] - At # 22 drift[ 0 ][ 22 ] =  27.1894  , t_delta:  27.1894
[2018-02-21T03:44:07.331 MST DEBG ][     org.kde.kstars.ekos.guide] - delta         [ 0 ]=  27.1894
[2018-02-21T03:44:07.331 MST DEBG ][     org.kde.kstars.ekos.guide] - drift_integral[ 0 ]=  9.75255
[2018-02-21T03:44:07.331 MST DEBG ][     org.kde.kstars.ekos.guide] - pulse_length  [ 0 ]=  3624
[2018-02-21T03:44:07.331 MST DEBG ][     org.kde.kstars.ekos.guide] - Direction     :  Decrease RA
[2018-02-21T03:44:07.331 MST DEBG ][     org.kde.kstars.ekos.guide] - At # 22 drift[ 1 ][ 22 ] =  -36.7613  , t_delta:  -36.7613
[2018-02-21T03:44:07.331 MST DEBG ][     org.kde.kstars.ekos.guide] - delta         [ 1 ]=  -36.7613
[2018-02-21T03:44:07.331 MST DEBG ][     org.kde.kstars.ekos.guide] - drift_integral[ 1 ]=  -12.5693
[2018-02-21T03:44:07.331 MST DEBG ][     org.kde.kstars.ekos.guide] - pulse_length  [ 1 ]=  4900
[2018-02-21T03:44:07.331 MST DEBG ][     org.kde.kstars.ekos.guide] - Direction     :  Decrease DEC
[2018-02-21T03:44:07.331 MST DEBG ][     org.kde.kstars.ekos.guide] - ################## FINISH PROCESSING ##################
[b][2018-02-21T03:44:07.332 MST DEBG ][     org.kde.kstars.ekos.guide] - Aborting "Guiding"[/b]

Guiding aborted, presumably because the guide star moved outside of the box (64x64). I'll be testing guiding without a box the next good night of weather. Regardless, I like to know how and why a system does the things that it does.

I happen to log RA/Dec to a different system every 10 seconds and noticed that both diverged in a very short time frame in between the two subs above. No slew commands were captured, so the input must have been from the guiding system in Ekos:



And here is the result of the diffs in the Ekos log file during the event:



And for reference, what it looked like in a normal state (RA & Dec swapped here? This is from the logs. Hmm):



So, in spite of all of this data I can still only guess:

- Maybe clouds came through? Some of the subs suggest it as a possibility but I'm not sure of it.
- Did the quality of the guide star change somehow?
- Did the guide star really move? Not sure - sometimes I find it guiding or focusing on nothing.
- Did the mount slew or otherwise get moved? External logs show the mount did not slew, but RA and Dec did adjust by way of guiding.

Is there any other data point I'm missing? If not, it might be good to have two things for the wish list:

- A way to log the quality of the guide star. Perhaps ADU count of the guide star from guide frame to guide frame would be good?
- Also nice - the RA & Dec of the guide star used!

- Greg
Last edit: 6 years 1 month ago by Greg.
6 years 1 month ago #23535

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Logfile attached.

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File Name: guiding_go...21-2.zip
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6 years 1 month ago #23536
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Maybe it identified a different star and moved it to the original lock position?
6 years 1 month ago #23537

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Maybe, but I don't think so. I had a 64x64 box set in the guide module (above I said 36x36 - edited for accuracy). I've seen other stars fit in a sub like that in the past, so that would make it possible. However, if I compare the center of the two subs from the main camera as ONE (where I wanted to be centered) and TWO (where I ended up) it's too far. In fact, that motion takes the center of ONE right off the guide chip. Yet, the log only shows it being out by ~37 pixels (assuming that is what diff refers to - can someone confirm?).
[2018-02-21T03:44:07.331 MST DEBG ][     org.kde.kstars.ekos.guide] - -------> BEFORE ROTATION Diff RA:  -27.001  DEC:  36.9

Here's an example - screencap from kstars with a FOV of the guider. My guider is on-axis (ONAG) so this is the FOV my guider sees.

This is centered on ONE:



And centered on TWO:



If you flip the images in my earlier post you can see that the stars move that amount.

Very interesting.
Last edit: 6 years 1 month ago by Greg.
6 years 1 month ago #23538
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