QHY268M keeps counting frame after it should end

[IDM]

Hi,
I have recently bought a QHY268M and I can get it up and running, but as soon as I change the exposure length say from 30 seconds to 60 seconds, I then watch the frame count down and when it reaches 0, it then goes negative and the frame just keeps counting in negative time adding to the exposure. The additional counting stops immediately if I reduce the USB traffic slider, but the frame that is now complete when inspected is blank, only the next frame which will have normal countdown works.
I
I have tried different USB rate from 5 to 30 but always get the problem. Is there a setting I am getting wrong?

Thanks,
Ian

[admin]

Hi Ian,

the best bet with this camera is to set the option for 'Force Still Mode' to on for long exposure work, even if leaving SharpCap in live view mode.
That runs the camera behind the scenes as a still camera with every frame requested by SharpCap and tends to make things run more reliably. Unfortunately the camera resolution changes slightly between still mode and live video mode (if it wasn't for that, I could make the switch happen automatically as the exposure is changed as it does for several other brands of camera, meaning the user never needs to worry about it).

cheers,

Robin

[IDM]

Hi Robin,
Thanks for the response, that change has fixed the problem.

Unfortunately the camera resolution changes slightly between still mode and live video mode

When you say this does that mean that the long exposure FITS files I am saving are of a lower resolution and therefore likely to be a problem?

Thanks,
Ian

[admin]

Hi Ian,

the difference in size is not very large - up to maybe 30 or 40 pixels in each direction, for instance my QHY294 is 4164x2822 in live mode and 4164x2794 in still mode. Not enough to make any real significant difference to how much image you get in view, but it is enough of a change to cause chaos if it happened as you altered exposure

cheers,

Robin

[dridge3770]

I have the QHY5III178C. Changing to Force Still Mode does not prevent the timer from "going negative".

[admin]

Hi,

the only other suggestion I can make is to treat it as a possible issue with USB data transfer and follow the 'USB Troubleshooting' steps, which you can find here : viewtopic.php?f=18&t=349&p=1556#p1556

In particular, try with a simple USB setup (no extensions/hubs between camera and PC) and try various values of 'USB Traffic' to see if you can get a stably working setup. If you do, then you can gradually work back towards your normal configuration and see what causes things to break.

cheers,

Robin