New to QHY128C - dumb questions

Hi Folks,
I have acquired a QHY128C and am relatively new to the world of astro dedicated CMOS cameras (for deep sky imaging anyway). Have some dumb questions …

  1. I have seen reference to gain/offset being specified/recorded differently via ASCOM driver vs. dedicated driver. However I think this might only apply to ASI cameras and not QHY? Or more specifically, I am assuming there is no direct driver for the QHY128C?
  2. After installing the QHY downloaded drivers, I see “QHYCCD-Camera-Capture” which I assume is the appropriate ASCOM driver?
  3. Where should I be setting the gain and offset for the camera? I notice that in the QHY driver settings (wrench icon) there is an opportunity to set Gain/Offset as well as set up presets (ie. DSO, Planetary etc.). But there are also the Gain settings by BIN level (Control Panel - Camera Tab - Gain section). Which takes precedent?
  4. Any recommendations on gain settings to use? I notice that the QHY driver defaults to Gain 1208 and Offset 60 for the “DSO” preset.
  5. For the Control Panel - Camera - Settings and Specs - “Readout Noise”, should I be using the manufacturer spec for readout noise at lowest gain? @ Unity Gain? Other?

Sorry if this has been answered elsewhere - I could not seem to find it via search.


There are no dumb questions, only dumb answers… here are some now:

Correct. SGPro supports “native” ASI drivers and ASCOM ASI drivers. They are a little different in that the native drivers allow for gain and offset modification and ASCOM only allows for gain (and I think some will allow for offset in the drivers settings).

There is, but SGPro does not support it (this is for the best)

It is.

The values set here will be for all images of all types unless you use SGPro to override the gain dynamically. You will need to set your offset here.

This takes precedent. Not setting for a particular binning will NOT use the value set in the ASCOM settings dialog. SGPro does not have access to this.

We have always recommended the manufacturers spec, but this value only influences the notion of “ideal exposure time” so if you dont use that, then dont worry about this.

Also, note that individual events can have their own gain. See Event Settings:

The order of precedence is Event, Binning, ASCOM

Thanks Ken! Had not noticed the Event Settings gain options before.

Event Settings: Just checking this out - I can set gain but offset is greyed out (set to NA). This is this expected behaviour (perhaps this is for future implementation)? So it gets the offset from the ASCOM driver in this case?

And if Gain not set in Event Settings or by Bin (Control Panel - Camera Tab - Gain section), it will use whatever the ASCOM driver is set to?

And in all cases, the offset used will be the value set in the ASCOM driver, regardless of the gain set in Event Settings or Camera Tab - Gain section? Sorry - being a bit repetitive here :=)

How do I confirm what gain/offset was actually used after capturing an image - perhaps by looking at the FITs header?

I presume the %cg and %co will only be populated if those values are set in Event Settings or Camera Tab - Gain section (ie. never for offset in my case)?


This is normal for ASCOM cameras.

Unlikely. ASCOM does not support offset (not an oversight)

The order of precedence is Event, Binning, ASCOM

Yes. SGPro cannot alter offset.

Kind of… SGPro has no insight to offset, but you can view your gain in the headers (or as part of the filename)

Yes. SGPro does not have access to data managed by the camera’s driver…

Thanks for the info @Ken (and your patience :grinning:).