Problems with misframing when reading camera

[old_eyes]

Hi - I wonder if anyone can help me with a problem. It is probably something simple, but I am unable to pinpoint it.

I have a QHY 168C OSC CMOS camera. I'm very happy with it.

The only issue is that some frames have been rotated a little way to the left. With a vertical bar on the right hand side, and what appears to be the data chopped off the left reappearing to the right of the bar.

Two images attached showing a normal frame capture and one with the error.

It happens at random, sometimes one in a run of 50 captured frames, sometimes a cluster of three or four closely spaced.

The camera is running over USB 3 to a mini-PC that is only running APT and PHD2. I typically run the camera at -20C

Is it the computer, the cable, the software, a camera problem? Anyone seen anything like this before? It is not a showstopper, more of an irritation, but I wish it didn't happen.

old_eyes

 

[old_eyes]

Should have also said this is the raw data, not debayered and just linearly stretched

[FaDG]

That's clear enough,  it's the PacMan effect !! ?

Seriously, I can see the same artefact in my ZWO ASI 120MM too, sometimes. So i'd also be interested in a solution. 

[old_eyes]

If I was really clever I could reassemble the frame. I think all the data is there. Or I could just crop it and still use it. I don't usually have anything interesting at the edges of the frame. Problem is the darks, bias and flats won't line up. Probably just too much work!

[FaDG]

You're right, this issue with flats and darks is really annoying. 

It comes to my mind that i never experienced it, because the issue only happens in PHD, never in Firecapture (i used the ASI120 only for guiding or planetari stuff). 

[vlaiv]

This is of course software problem, but I'm not sure whether it is drivers or capture app.

I had something similar once with ASI1600 and SIPS (ascom compliant free capture app from moravian instruments). Image was not shifted but it was distorted. I mean all the data was there but application refused to provide clean sub and instead it offered something like half width full height scrambled version of it.

At the time I figured it must be due to size of single sub as with my other cameras with less pixels it worked fine. Then I switched to SGP and that worked without any issues on same drivers.

This leads me to believe that it could be capture application problem - it can't properly handle subs of that size for some reason. Could you try another capture app just to see if frames would be ok? SGP has lite version which is free - you won't be able to do things like plate solve and there are other restrictions - but I've used it for a while before getting pro version - and it was ok for most imaging purposes. If same happens with it - then I would recommend looking into drivers (ascom ones - see if there is update, or contact QHY with problem description).

[old_eyes]

Thanks vlaiv. I will try that. Also will try the capture progrmme supplied with QHY cameras.

[old_eyes]

Turns out it was a problem with the USB3 port on the Minix computer I was using to run rig. It was fine on other USB3's and when I switched to a USB 2 port on the Minix it worked fine.