Exposure duration error with QHYCCD camera


I’ve filed the ticket to QHYCCD forum, but it may be of interest to this forum as well.

I’m using QHYCCD367c camera connected both to MainSequence SGP Pro and MaximDL - since it has ASCOM driver allowing multiple clients connected in parallel. I select QHYCCD-Cameras-Capture as camera device in both applications. When I use these programs exactly as described below, the MaximDL (used as camera control software for FocusMax V4) uses wrong exposure duration, which apparently equals to the duration of last light frame exposure used by SGP, instead of exposure duration set by MaximDL:

  1. Connect SGP Pro to QHYCCD367c camera
  2. Connect MaximDL to QHYCCD367c camera
  3. Perform Frame and Focus exposure of 1 second in SGP
  4. Run sequence in SGP capturing at least one light frame of duration (f.e. 30 seconds) and wait for SGP to become idle
  5. Capture single frame in MaximDL with short duration of, say, 1 second.

If I skip running step (3), then step (5) completes within short time of 1 second added time required to download the frame. If I run step (3), then step (5) takes more than 30 seconds to complete (and generally its time is related to duration of light frame of step (4). Please note, than SGP and MaximDL never do exposures at the same time. Only after SGP finished exposure(s) and download last frame, I take exposure inside MaximDL.

It could be helpful to understand what is difference in programmatic sequence inside SGP between taking light frame and taking F&F exposure (and if I’m correct, also Plate Solve exposure affects timing of taking subs in MaximDL). The only workaround I found to avoid these errors is either avoid completely using F&F and/or P&S frames or disconnecting camera from both SGP and MaximDL and reconnecting back.

It looks to me as if use of QHYCCD API by F&F frames (and/or P&S) triggers some issue within QHYCCD driver, and while QHYCCD support is trying to resolve it, I’d like to find a temporary workaround for this issue inside vbscript but without disconnecting camera from either application (as it poses big trouble with camera cooling).

Any suggestions and explanations would be welcome!

With regards,



F & F is using the same ASCOM call to do an exposure as doing a light exposure.
I’m not sure why you have two programs both connected to the camera but you need to be very careful because the two programs do not know about each other and inference is a real possibility.


I’m fairly sure that the camera driver is not designed to have two applications controlling the same camera at the same time. I’m not surprised that it does not work correctly. If there is a problem with the driver, it is that it allows this to happen.

The multi-client capability of the QHY driver is intended to be used for multiple cameras. Why are you trying to control the camera with two clients connected simultaneously?