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Dither messes up guide exposure

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Dither messes up guide exposure was created by Peter Sütterlin

Hi,

after almost a month, I finally had time again to do some observations tonight.  So I compiled the latest INDI and kstars from git.

Seeing and guiding was outstanding, but after the first dither guiding went completely berzerk.  It took a while until I realized that the guide camera, instead of doing 4.5s exposures, was reading out in second cadence.  I could see the counter (in the INDI tab) start at 4.5, but before it reached 3 the frame was read out!  And of course guide pulses were sent out at that rate, too, f*****g up the mount (the CEM60EC doesn't like that fast guide pulses and reacts with erratic behavior).
It's absolutely repeatable.  I stop the guiding, do one capture, then restart it.  It will guide with 4.5s exposures until after the next dither.  As soon as that is done/settled, it switches to the 'fast mode'

Anyone seen that before?  Ideas?

Now I'm musing whether I should switch back to the old kstars, or disable dither :-(
 
2 years 10 months ago #71850

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Replied by Sonny Cavazos on topic Dither messes up guide exposure

I have only seen that happen once on my setup. It's when I was looping the capture in the focus module (I thought I had the imaging camera selected, but it was in fact doing the guide camera instead)

Make sure the guide camera is only being used in the guide module.

Another time I had issues is when I was capturing dark frames for my guide camera, the system would allow the guide camera to capture guide stars, or focus even though it was doing a dark capture (it messed up my dark capture session).

This was on one of the nightly windows builds.
2 years 10 months ago #71905

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Replied by Peter Sütterlin on topic Dither messes up guide exposure

Hmm, no, that didn't apply for me. Focus was set to use the main cam (but not active, of course), so was align (but also not used). The main camera was properly taking images all the time.
But every time a dither finished, the guide cam would start reading out as soon as the readout/processing of the guide image was finished.
Stopping and restarting the guiding cured the issue, until the next dither. After three such failures I disabled dither, and the rest of the images were taken without problems, for both cameras.

I had a look at the log file, but logging was only standard, so not much info in there. And on first look no difference in the messages when comparing to the last successful session May 11.

I'm in clouds today, so I can't test for now.....
2 years 10 months ago #71933

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Replied by Ron Clanton on topic Dither messes up guide exposure

I'm curious as to your settings for dithering. Would you mind sharing your "Guide" settings? Particularly on the "settle" setting.

Also, are you using the internal guider? If so, have you tried using PHD2? I've had terrible luck with the internal guider, but PHD2 seems to work flawless for guiding and dithering.

Ron
2 years 10 months ago #71937

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Replied by Peter Sütterlin on topic Dither messes up guide exposure

Nothing weird. Settle is set to 2s, dither 5 pixels, threshold 1.25. I switched from PHD2 to internal last year, and get (very!) good guiding with it. Until 3 days ago. And no clue what is suddenly wrong :(
2 years 10 months ago #71990

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Replied by Peter Sütterlin on topic Dither messes up guide exposure

So I just ran some tests.  First same setup as three days ago (git and INDI from June 1).  I just set up a fake sequence with 20s exposures and dither every frame.  Guiding as usual, internal with multistar and 4.5s exposures.
Like last time, as soon as the dither was finished it started the fast readouts.
I had (of course) debug on this time.  What I see is
[2021-06-04T21:54:09.317 WEST DEBG ][     org.kde.kstars.ekos.guide] - Capturing frame...
[2021-06-04T21:54:09.362 WEST DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI1600MM Pro : "[DEBUG] Aborting exposure... "
[2021-06-04T21:54:09.709 WEST INFO ][           org.kde.kstars.indi] - ZWO CCD ASI1600MM Pro :  "[INFO] Exposure done, downloading image... "
[2021-06-04T21:54:09.709 WEST INFO ][           org.kde.kstars.indi] - ZWO CCD ASI1600MM Pro :  "[INFO] Download complete. "
WTF!?  Why is it aborting the exposure?
Before the dither this looked like this:
[2021-06-04T21:52:36.414 WEST DEBG ][     org.kde.kstars.ekos.guide] - Capturing frame...
[2021-06-04T21:52:36.422 WEST DEBG ][           org.kde.kstars.indi] - ZWO CCD ASI1600MM Pro : "[DEBUG] StartExposure->setexp : 4.500s "
[2021-06-04T21:52:36.426 WEST INFO ][           org.kde.kstars.indi] - ZWO CCD ASI1600MM Pro :  "[INFO] Taking a 4.5 seconds frame... "
[2021-06-04T21:52:41.629 WEST INFO ][           org.kde.kstars.indi] - ZWO CCD ASI1600MM Pro :  "[INFO] Exposure done, downloading image... "
[2021-06-04T21:52:41.661 WEST INFO ][           org.kde.kstars.indi] - ZWO CCD ASI1600MM Pro :  "[INFO] Download complete. "
Next, I downgraded libasi to an older version.  Same error.  Then also INDI.  First to version 1.9.1-55_g44ceb95c (May 18).  Still faulty.  I then realized last good observations I did May 11, so I went back to INDI 1.9.1-6_g538ab217 (May 3).
With that one it works again.

So something happened between May 3 and May 18 that kills my guiding after a dither :(
I'm attaching the logs of the various tries, in case someone can extract more info from them....
 
2 years 10 months ago #71995
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Replied by Ron Clanton on topic Dither messes up guide exposure

Yes, that is weird.

In the log, the exposure aborts first... then guiding.

Also, are you using the ASI1600MM for guiding? The log shows it taking the 4.5 seconds frame.... is that right?

Hopefully, Jasem will chime in here.

Ron
2 years 10 months ago #71996

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Replied by Peter Sütterlin on topic Dither messes up guide exposure

Yes, I have a dual setup, a 2600 on a 140mm refractor, and the 1600 on a 92mm one, for wide field. I use it for guiding when the 140 is the main scope :) Thanks to USB3 download times are not an issue...

I was checking the git log between the two dates, but nothing caught my attention as an obvious thing to look at. Some hint from the gurus might indeed be needed
2 years 10 months ago #71997

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Replied by Hy Murveit on topic Dither messes up guide exposure

Pit, can you explain further about:
    "So something happened between May 3 and May 18 that kills my guiding after a dither"
Are you saying something in the Indi nightly release between those dates, or the KStars nightly release between those dates, or either one?
That is, are you running from source with both Indi & KStars, or running from compiled nightlies grabbed on those days?
When you say, you checked the logs, did you also check the Indi logs? 
Is it possible to reproduce with the simulator?


 
2 years 10 months ago #71998

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Replied by Peter Sütterlin on topic Dither messes up guide exposure

Hej, I thought you enjoy your well-deserved vacation :D

So to be clear, yes, it is an INDI issue. At least not a KStars one, as I'm currently running the version I compiled June 1 (3.5.4-2083_g95fdd1b37). It was only after I downgraded INDI to the May 3 version that the problems stopped.

This is always self-compiled versions from git. So if there is a suspicious commit I can always check out versions before and after, and cross-check. But if I have no idea where to start....

I just realize that I might also have to re-check libasi. That one was updated to SDK 1.18 on May 18. I had not tried only downgrading that one to the May 3 version. Will do in an hour or so, when the current sequence is finished ;^>

I had thought about the simulator, too. But I'm not very fluent with it. If I find the time, I'll try it, too.
2 years 10 months ago #72000

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Replied by Alfred on topic Dither messes up guide exposure

During my Losmandy tests I encountered a similar problem with my 294MC Pro/294MC combo. The guide cam stopped working after taking a video sequence. Since I have not been observing at night I cannot comment on the guiding problem but it sounds very similar to me and the setup (2x ASI) is the same. I also ran the latest GIT versions of Indi and KStars. The issue was 100% reproducible:
Start a video sequence using the guide cam. Stop the video sequence. Then try taking a single photograph. It will result in error. Both cams are "lost" and don't show up in lsusb anymore. After reboot everything is back to normal till the next video sequence.
Last edit: 2 years 10 months ago by Alfred.
2 years 10 months ago #72003

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Replied by Peter Sütterlin on topic Dither messes up guide exposure

Gee that sounds bad! But no, no video involved here AFAIR(*). And guiding/taking images works flawlessly for hours - if I don't dither :P
Yes, I'd like to test some other camera, but ZWO is all I have (4 of them....)

(*) I regularly do use video for the main cam, for initial focus.
2 years 10 months ago #72004

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