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08 Apr 2018
INDI development team is happy to announce the release of INDI Library v1.7.0. This new exciting release builds on the maturity of INDI Library and comes with many new supported devices and fixes for existing drivers.
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TOPIC: Lost star when dithering causes capture module to hang

Lost star when dithering causes capture module to hang 3 weeks 3 days ago #26715

You're absolutely right, that's the reason it failed. I think the original reason was to reject any pulses at near maximum, since it is most likely that something is very wrong at this point. However, this is not the case with dithering, and not just any dithering, but a whopping 10 pixel dither which puts it to the limit.

Another reason for this "kill-switch" here is that you probably do not want to stray off your target while you're guiding, so it protects against wild swings that might ruin your session. So I think I'll limit the sendPulses = false to regular guiding and not while dithering.
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Jasem Mutlaq
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Lost star when dithering causes capture module to hang 3 weeks 2 days ago #26724

  • kross
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Sounds like a plan! :)

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Lost star when dithering causes capture module to hang 3 weeks 2 days ago #26731

Changes already committed yesterday.

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Lost star when dithering causes capture module to hang 3 weeks 1 day ago #26750

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I tested the last build tonight with 10 pixel dithering and it went very well. I acquired 18x600s and it lost the star only 2 times.
The star was lost when it was very close to the frame limit but even after failure the guiding continued and did not interrupt the sequence.
Sometimes the movements are always in the same direction and with a big pixel movement (10 pixels) it gets very close to the frame limit.
When it changes direction it goes fine again.
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Last Edit: by nmac.

Lost star when dithering causes capture module to hang 3 weeks 23 hours ago #26762

In fact, at least in my case (using Losmandy G-11), dithering ALWAYS moves in the same direction. You can easily check this by blinking the light frames that have been taking during a session. Usually I do use 10 pixel dithering and it doesn't take too many frames for the guide star to run into the subframe border. I could resort to using full frame guiding but that limits the frame rate quite a bit.

Would it be possible to "dither" (move) the subframe in lockstep with the guide star in order to have the guide star stay in the middle of the subframe?

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Last Edit: by Herrhausen.

Lost star when dithering causes capture module to hang 3 weeks 19 hours ago #26767

I have a better question. How can a random dither always move in the same direction? That sounds like a bug to me. . .

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Lost star when dithering causes capture module to hang 3 weeks 8 hours ago #26772

Well, randomness is not truely random in computers, but still it would be odd to _always_ move in the same direction. I guess an invisible protection zone can be arbitrarily defined to bound the star to it to ensure it doesn't stray too far off.

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Jasem Mutlaq
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Lost star when dithering causes capture module to hang 3 weeks 4 hours ago #26775

This is from my most recent session. To me the dithering direction doesn't look random at all.
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Last Edit: by Herrhausen.

Lost star when dithering causes capture module to hang 3 weeks 4 hours ago #26776

Another picture (taken weeks ago) using 2,8 pixel dithering resulting in "noise rain" also shows dithering always goes in one direction.
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Last Edit: by Herrhausen.

Lost star when dithering causes capture module to hang 3 weeks 4 hours ago #26778

What strikes me is the factt that not only goes dithering in one and the same direction during a job. It appears to remain the same during the whole night.

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Last Edit: by Herrhausen.

Lost star when dithering causes capture module to hang 2 weeks 6 days ago #26784

Thanks, I just pushed a fix for the not-so-random dither and used different algorithm and add a bounded area. Please try the nightly build or wait for next release.
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Jasem Mutlaq
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Lost star when dithering causes capture module to hang 2 weeks 6 days ago #26796

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Herrhausen wrote: What strikes me is the factt that not only goes dithering in one and the same direction during a job. It appears to remain the same during the whole night.


That's quite odd, since for me with 10 pixel dithering it does move in a different direction each time.

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