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

Bi-monthly release with minor bug fixes and improvements

Lost star when dithering causes capture module to hang

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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5 years 9 months ago #26715

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Sounds like a plan! :)
5 years 9 months ago #26724

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Changes already committed yesterday.
5 years 9 months ago #26731

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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: 5 years 9 months ago by nMAC.
5 years 9 months ago #26750

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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?
Last edit: 5 years 8 months ago by Alfred.
5 years 9 months ago #26762

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I have a better question. How can a random dither always move in the same direction? That sounds like a bug to me. . .
5 years 9 months ago #26767

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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.
5 years 9 months ago #26772

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This is from my most recent session. To me the dithering direction doesn't look random at all.
Last edit: 5 years 9 months ago by Alfred.
5 years 9 months ago #26775
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Another picture (taken weeks ago) using 2,8 pixel dithering resulting in "noise rain" also shows dithering always goes in one direction.
Last edit: 5 years 9 months ago by Alfred.
5 years 9 months ago #26776
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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.
Last edit: 5 years 9 months ago by Alfred.
5 years 9 months ago #26778

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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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5 years 9 months ago #26784

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That's quite odd, since for me with 10 pixel dithering it does move in a different direction each time.
5 years 9 months ago #26796

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