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

Bi-monthly release with minor bug fixes and improvements

Bias frames - No data/empty?

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One thing possibly worth checking is if offset value in camera settings is too low, that might cause pixels to clip to black. At least ASI driver has that configurable. Especially Sony sensor cameras seem to be prone to that due to some overly aggressive dark current compensation.
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4 years 2 months ago #47398

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Offset is set to 8 in my case which is the default value IMO.

4 years 2 months ago #47404
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Does raising that make any difference? I don't know about your camera in particular, but on my 178MC the default value was too low and caused pixels clipping quite badly in darks especially. Though it was never fully zeros due to warm/hot pixels.
4 years 2 months ago #47417

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The histogram AFAICS does not indicate a clipping issue so I never changed the default value.

4 years 2 months ago #47423
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I don't get this!

Last night I tried turning on my RP4 with everything connected, opened KStars/Ekos and started my "calibration" profile where I only have my ZWO 294MC Pro and QHY5L-II-C cameras enabled. Then I tried a test Bias frame and that worked!? So now I have recorded 100 Bias frames (gain 120 and default gain). No errors in PixInsight anymore.

Could it have been a problem recording the Bias frames with all my gear enabled in Ekos?
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
4 years 2 months ago #47432

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Replied by Alfred on topic Bias frames - No data/empty?

LOL, I have no idea! Something worse than that could have happened though. I won't touch your rig anymore unless the issue returns which I hope will never happen! :-) Good to hear the problem disappeared! You can add a [SOLVED] to the topic line.
Last edit: 4 years 2 months ago by Alfred.
4 years 2 months ago #47433

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Hmm, when looking at my Bias frames info in KStars and comparing to yours, all the values are pretty much the same - except Median. Yours shows 0 mine shows 526 point something in the Histogram tab but 0 in the Statistics tab. Should I be worried?
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
4 years 2 months ago #47435

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Replied by Alfred on topic Bias frames - No data/empty?

I don't think so. When I look at the results that I get I'm not worried at all.
4 years 2 months ago #47538

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I don't know....

I think Andy Grove was on to something when he coined the phrase:

"Only the paranoid survive"

Maybe you should be afraid.... VERY afraid....

:-)
4 years 2 months ago #47539

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;-)
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
4 years 2 months ago #47555

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Hi,

the problem with empty bias frames can be caused by a wrong offset. The default value of 8 is too low, and the sensor's dark current compensation kicks in and clips the noise to zero. Offset should be chosen in a way that a bias frame has a mean value of about 500-1000 (on a 16bit scale). For my ASI294MC, it was offset 14 (at gain 0, might be different for other gains).
The following user(s) said Thank You: maxthebuilder
4 years 2 months ago #48654

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I just noticed this too...
My bias frames used to be not empty before mid-October last year.
Since then they are empty. Totally empty.
ASI294MC. Gain 200. -5C.
I used to use an offset higher than default (40 vs 8 ). Don't remember when I switched to the default of 8.
Just checked:
at offset 35 bias histogram is still clipped.
at 37 it looks good.
Interesting thing is that the histogram (in Ekos) looks exactly the same for exposure times 0.01-0.0001 sec.
Not sure what's going on...

-- Max S
ZWO AM5. RST-135. AZ-GTI. HEQ5. iOptron SkyTracker.
TPO RC6. FRA400. Rokinon 135 and other lenses.
ZWO ASI2600MC. D5500 modified with UVIR clip-in filter.
ZWO ASI120MM Mini x 2. ZWO 30F4 guider. Orion 50mm guider.
ZWO EAF x 2.
Last edit: 4 years 1 month ago by maxthebuilder.
4 years 1 month ago #49047

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