Thank you for your response. However, it looks different:
This is the software that I ran last night:
Windows 10 Pro
.NET Framework Version: 4.8
ASCOM Platform version: 6.5.1.3174
ZWO ASCOM camera driver 6.5.1.8
SGP v4.0.0.680
In SGP the offset value cannot be altered, neither in a sequence nor in the equipment profile. No FITS keyword OFFSET is written to the FITS header.
In the SGP logfile, I found the following passage:
[08/02/21 21:47:42.887][DEBUG][Main Thread][NONE] Failed to fetch ASCOM camera offset list, checking min / max...
[08/02/21 21:47:42.893][DEBUG][Main Thread][NONE] Failed to fetch ASCOM camera offsets from min / max. Failed to get camera offset! : Property read ASCOM.ASICamera2_2.Camera OffsetMin is not implemented in this driver. (System.Runtime.InteropServices.COMException (0x80020006): Unbekannter Name. (Ausnahme von HRESULT: 0x80020006 (DISP_E_UNKNOWNNAME))
bei System.RuntimeType.InvokeDispMethod(String name, BindingFlags invokeAttr, Object target, Object[] args, Boolean[] byrefModifiers, Int32 culture, String[] namedParameters)
bei System.RuntimeType.InvokeMember(String name, BindingFlags bindingFlags, Binder binder, Object target, Object[] providedArgs, ParameterModifier[] modifiers, CultureInfo culture, String[] namedParams)
bei ASCOM.DriverAccess.MemberFactory.CallMember(Int32 memberCode, String memberName, Type[] parameterTypes, Object[] parms) in C:\ASCOM Build\Export\ASCOM.DriverAccess\MemberFactory.cs:Zeile 242.)
bei ASCOM.DriverAccess.MemberFactory.CallMember(Int32 memberCode, String memberName, Type[] parameterTypes, Object[] parms) in C:\ASCOM Build\Export\ASCOM.DriverAccess\MemberFactory.cs:Zeile 264.
bei ASCOM.DriverAccess.Camera.get_OffsetMin() in C:\ASCOM Build\Export\ASCOM.DriverAccess\Camera.cs:Zeile 1748.
bei ub.nt()
[08/02/21 21:47:42.893][DEBUG][Main Thread][NONE] Camera does not implement ASCOM offset.
Today I reverted to the ZWO ASCOM camera driver 6.5.1.5 (this is the version that is shown in the Windows control panel. When I change settings, the software identifies itself as "ASICamera Setup V6.5.17.1" though!). Other software is unchanged. Now in SGP the offset value can be altered both in a sequence and in the eqipment profile. The FITS keyword OFFSET is written to the FITS headers.
In the SGP logfile the corresponding passage now reads:
[08/03/21 11:46:00.578][DEBUG][Main Thread][NONE] Failed to fetch ASCOM camera offset list, checking min / max...
[08/03/21 11:46:00.581][DEBUG][Main Thread][NONE] ASCOM Camera offsets list, min: 0; max: 50
So definitely a request for the ASCOM camera offset list leads to an exception in case of ZWO ASI camera driver 6.5.1.8, whereas the request is responded in case of ZWO ASI camera driver 6.5.1.5.
Other software being identical, the ZWO ASCOM camera driver behaves in a different manner.
I do not know who is right or wrong. However, if you have a clue what went wrong (either in SGP or the driver), please contact Jared from SGP in order that this incompatibility can be fixed. Thank you!
Bernd