FITS file exposure time

[pnoah]

When using Sharpcap, my QHY183C sometimes has an exposure longer than requested. Sometimes up to twice the requested exposure time. But when I look at the FITS header for that frame, it has the requested exposure time and not the actual exposure time. Is there a way to get the actual exposure time? I would like to be able to throw out the bad exposure when stacking.

Thanks
Paul Noah

[admin]

Hi Paul,

the exposure values are correct in the fits headers - the reason that you are sometimes seeing long frames is that somewhere between the camera and SharpCap the odd frame is being lost. This means that the gap between frames will be double the usual time when a frame is dropped.

One thing that can cause this is USB issues, so if you are using hubs or extension cables, try again with just the cable that came with the camera and see if that helps. For your QHY camera you can also try increasing the 'USB Traffic' slider on the right or possibly trying the 'Force Still Mode' option which may help.

Hope this is useful,

Robin

[pnoah]

Hi Robin

Thanks for the input. I haven't had a chance to give things a try since weather has been terrible for several weeks. If we every get some clear nights again, I will definitely look into your suggestions

Paul