Gain imaged at and Gain recorded in FITS Header differ

Just starting to test out my new Altair Astro Hypercam 183C ProTec and while imaging a couple of night ago I noticed that the gain the camera was set to (398) was not what was being recorded in the FITS header (298).

Which is right? and do I have some setting messed up?


I can’t really say which is wrong or right. I’d double check he gain settings in SGP and make sure they’re as expected and test again. If things don’t match please post the SGP log and we can see if things are getting mismatched somewhere along the lines.


Thanks Jared for the quick response, I know you’re busy programing and beta testing! I double checked, everything seemed to be setup correctly. Above is the full log, I went through it but couldn’t really seem to decipher much. This is what I found. There seems to be some type of error messages when SGP initially connects with the camera. Since there’s no native support for my camera, I use ASCOM.

[09/30/19 22:20:56.695][DEBUG] [Main Thread] Connecting camera in main thread…
[09/30/19 22:20:56.699][DEBUG] [Main Thread] Connecting ASCOM camera: ASCOM.Altair.Camera…
[09/30/19 22:20:58.597][DEBUG] [Main Thread] Camera implements ASCOM gain. Current gain is 406
[09/30/19 22:20:58.604][DEBUG] [Main Thread] Failed to fetch ASCOM camera gains list, checking min / max… : Property write Gains is not implemented in this driver. (ASCOM.PropertyNotImplementedException: Property write Gains is not implemented in this driver.
at ASCOM.Altair.MonitoringInterceptor.Intercept(IInvocation invocation) in C:\Documents\Source Code\altair-ascom-driver\Altair.Camera.ASCOM\MonitoringInterceptor.cs:line 40
at Interceptor.InterceptorProxy.InvokeMethodCall(IMethodCallMessage message) in C:\Documents\Source Code\altair-ascom-driver\Altair.Camera.ASCOM\Interception.cs:line 268
at Interceptor.InterceptorProxy.Invoke(IMessage msg) in C:\Documents\Source Code\altair-ascom-driver\Altair.Camera.ASCOM\Interception.cs:line 250
at System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type)
at ASCOM.DeviceInterface.ICameraV2.get_Gains()
at ASCOM.Altair.CameraBase.get_Gains() in C:\Documents\Source Code\altair-ascom-driver\Altair.Camera.ASCOM\Driver.cs:line 620)
at ASCOM.DriverAccess.MemberFactory.GetTargetInvocationExceptionHandler(String memberName, Exception e) in C:\ASCOM Build\Export\ASCOM.DriverAccess\MemberFactory.cs:line 661
at ASCOM.DriverAccess.MemberFactory.CallMember(Int32 memberCode, String memberName, Type[] parameterTypes, Object[] parms) in C:\ASCOM Build\Export\ASCOM.DriverAccess\MemberFactory.cs:line 231
at ASCOM.DriverAccess.Camera.get_Gains() in C:\ASCOM Build\Export\ASCOM.DriverAccess\Camera.cs:line 862

In the ASCOM settings window for the camera there is a gain slider which is set to 4.06. I think I set it there because that was close to unity gain for my camera (398).

Later in the log whenever SGP starts an image whether its during autofocus or capturing a sequence I get lots of this:

[09/30/19 22:27:16.597][DEBUG] [Camera Thread] SetAscomGain to 398
[09/30/19 22:27:16.597][DEBUG] [Camera Thread] Camera gain set to 298

Not sure what it really all means. Maybe you could translate it all into normal people language for me!



I am not 100% certain, but it looks like the Altair camera is rejecting the gain we are attempting to set. Maybe the Altair log will have more information as to why. In the snippet above you see SGPro indicate it is attempting to set gain to 398. The Altair driver seems to accept the value (meaning there is no error), but when we ask it what it’s set to, it reports 298.

Thanks Ken, Just found this thread from a couple of years ago.

Could this be what’s still happening to me?



Yes! Good find… The response Chris had at the bottom was (mostly) correct. This has been corrected in 3.1

Thank you Ken, is this corrected in the current betas too?


Yes, this issue has seemingly been around for quite some time. It will be addressed in any version of SGPro greater than