Autofocus Darks

Just wondering if SGP is aware of binning in selection of darks to apply to autofocus images. I understand the dark file naming convention requires exposure time but not binning. Is the file name used to select the dark or does SGP use information in the fits header? If it uses the file name how does it know to select 1x1 or 2x2 binned dark if both are present in the folder or alternately if the binning for autofocus is changed does it know not to apply the wrong dark if the binning doesn’t match?

SGPro does not allow for AF binning changes during execution. Because of this, we also make the assumption that your dark frames match the chosen binning. If you, for some reason, find yourself changing binning for AF often (you shouldn’t), you will need to point the AF setting to a different folder containing the properly binned dark frames.

That said, SGPro will not attempt to apply a dark frame unless its dimensions match the AF frame’s exactly.


Only the file name, no FITS header data is used.

Having mixed bin frames in the same folder is not allowed. Use a File System structure like “AF Darks/2x2/”. If you change binning for AF (again something you should not need to do often…), Point darks to the right folder.

Thanks Ken, that makes sense. I normally wouldn’t mess with the binning but I’m doing some experiments with the SN10 to attempt to get a more consistent focus result. I’m finding it difficult to replicate the autofocus result and also it seems to differ from what the Bahtinov mask shows as the best focus position.

Those scopes are pretty fast and if your AF focuser movement range moves you into “donut land” you will have trouble. Make sure you turn off “smart focus” since you have a secondary obs.