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IDProjectCategoryView StatusLast Update
0002141CCdciel[All Projects] Generalpublic19-06-15 08:45
ReporterhanAssigned ToPatrick Chevalley 
PrioritylowSeveritytweakReproducibilityhave not tried
Status resolvedResolutionfixed 
Product Version 
Target Version1.0Fixed in Version 
Summary0002141: Fits header comments for GAIN and default camera settings.
Description1) The camera gain is recorded in the FITS header as follows:
      GAIN = 139 / Video gain

is it not better to change the comments in something like:
      GAIN = 139 / Camera gain

I noted that Diffraction limited is using EGAIN and at the INDI forum found that "Nebulosity uses GAIN whereas Ekos is using EPERADU". So no standard again.

2) I like the new camera option "Gain from camera driver" since I always use unity gain. Is it not better to have this option default checked?. Simplifies the menu for new users and prevents wrong inconsistent gain setting.
TagsNo tags attached.


Patrick Chevalley

19-06-14 21:45

administrator   ~0005691

Hello Han.

1) I voluntarily use "video gain" to avoid confusion with the gain of the camera in photoelectrons per ADU.
Sure the video gain setting is related to the "electrons per ADU" but is given in arbitrary unit unique to every camera model.
For the ASI1660 "video gain"=139 is equivalent to "electrons per ADU"=1 but this is different for other camera.

But I can add a header for EGAIN if available from the driver, this is the ASCOM property ElectronsPerADU. I not see an INDI equivalent in the documentation but I will look at the different driver source code.
EGAIN is the standard keyword defined in the SBIG Fits Extension everyone is using now.

2) It is set by default for a new installation of the program or if you create a new device profile (not copy).
But for existing profile I prefer to not change the old behavior, to not break some user setting that rely on changing the gain.

Patrick Chevalley

19-06-14 21:58

administrator   ~0005692

After a quick look in the INDI code the keyword EPERADU is only implemented for QSI camera.
The ASI driver define a variable ElecPerADU but it is not used anywhere.

So I will probably implement that only for ASCOM.


19-06-14 22:14

reporter   ~0005693

I would not add any new keyword. GAIN is fine for me

SBIG is now owned by Diffraction Limited (Maxim DL) and they publish their keywords at:
and they specify:
EGAIN – electronic gain in photoelectrons per ADU.

That doesn't match with the ZWO 0.1 db specification so my 139=unity gain.

I personally would stick with "GAIN" like Nebulosity. I assume it is only read by Humans. Maybe you should write at the comments something like

GAIN = 139 / Camera gain setting in units as specified by manufacturer.

Patrick Chevalley

19-06-15 08:45

administrator   ~0005695

OK I keep only this Gain keyword and updated the comment with your text that give a better description. I only have to shorten the text to "Camera gain setting in manufacturer units" to fit the 80 column header.

Issue History

Date Modified Username Field Change
19-06-12 14:11 han New Issue
19-06-14 21:44 Patrick Chevalley Assigned To => Patrick Chevalley
19-06-14 21:44 Patrick Chevalley Status new => assigned
19-06-14 21:44 Patrick Chevalley Description Updated View Revisions
19-06-14 21:44 Patrick Chevalley Steps to Reproduce Updated View Revisions
19-06-14 21:45 Patrick Chevalley Steps to Reproduce Updated View Revisions
19-06-14 21:45 Patrick Chevalley Note Added: 0005691
19-06-14 21:58 Patrick Chevalley Note Added: 0005692
19-06-14 22:14 han Note Added: 0005693
19-06-15 08:45 Patrick Chevalley Status assigned => resolved
19-06-15 08:45 Patrick Chevalley Resolution open => fixed
19-06-15 08:45 Patrick Chevalley Target Version => 1.0
19-06-15 08:45 Patrick Chevalley Note Added: 0005695