indilib/indi

ZWO CCD driver alters biases and darks

FalCT60 opened this issue · 5 comments

FalCT60 commented

Describe the bug
ZWO CCD driver applies a WB correction to all darks and biases with ASI183MC non cooled.

To Reproduce
Exact steps to reproduce the behavior.

  1. Takes darks and biases with ASI183MC-nc and Kstars 3.6.6
  2. Compute statistics on the series of files
  3. Values for R, G and B ought to be the same, but in fact R & B get multiplied by a factor

Expected behavior
Darks and biases are not RGB pictures, but grey tones.
Attached is a spreadsheet showing the computing of a series of biases at gain 120 and offsets from 10 to 50 step 5, with SM, the other with NINA.
offset.ods
Here is the link to the files used for the computation, so they can be analysed.

Desktop (please complete the following information):

  • OS: Stellarmate raspbian 64
  • Version: Kstars 3.6.6, SM OS 2.6.60
FalCT60 commented

Should this help : at gain 120 / offset 10, median values are 704 for green channel, but 731 for red and 1336 for blue.
All other values are affected too : sigma, MAD, etc.
This affects preprocessing and gives awful results.
This is not the camera's fault, but the driver's, as if I use another soft the darks and biases do not suffer those problems, all values are consistent.

MattBlack85 commented

I believe this is an old "issue", INDI sets (I believe because those are default even within the SDK) the WB to these values:

  • WB_R 52
  • WB_B 95

You can set them both to 50 and calibration frames should come out good

knro commented

INDI does not change these values, they're ready from camera on startup.

FalCT60 commented

@MattBlack85 yes, as stated there, those values must be set to 52 and 95. And this is what happens if I click on Default in options tab.
I was suggested to replace them by 50, and I did some computing that led to values of resp. 50.059 and 50.079 - so, 50.
The problem is - and it will be adressed in another bug report - that the values that I type in the Controls tab fields get sometimes overriden, despites being saved.
Yes, they remain while the system runs, but as soon as I restart my rPI they may have been restored to their original values.
It has appened more than five times today during my testings for WB_R, WB_B, Offset and Bandwidth, though I did have saved the config each time. As it did happen previously with Gain.
@knro do you mean they are embedded in the camera rom, and they are read on connection ?
Because, now that I have set them to 50 and saved the config, if I click to the Default button in Options tab, they will be restored and overrride my own settings. So, they must obviouly be read from somewhere.

knro commented

No, there is a configuration file under ~/.ZWO as well that saves these settings in ZWO own format.