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Paul
Sampling in general terms is how well your image train can resolve levels of detail in objects at various atmospheric conditions using a specific pixel matrix on the camera sensor via your focal length / focal ratio
To see if your over sampled or under sampled you need to work out your image scale or pixel scale of your image train ( telescope and camera )
Formula for image scale or pixel scale (P) expressed in arc sec per pixel is -
P= pixel size of your imaging camera ( in microns uM ) x 206.3 divided by your telescopes focal length in mm
Over sampling is < 1.0 arc sec / pixel
Under sampling is > 2.0 arc sec / pixel
In good seeing conditions 0.80 to 1.0 arc sec/ pixel is OK stars will be round and sharp
In average to poor seeing conditions 0.80 to 1.0 arc sec/ pixel will produce slightly fuzzy or bloated stars
It’s most cases and conditions is probably better to be slightly over sampled or around the 0.80 to 1.20 arc sec per pixel mark ( but not critical as atmospheric conditions vary so much )
NB: DSLR’s are generally only useful in telescopes with focal lengths less than 1200mm or > 0.80 arc sec per pixel
Hope the above answers your question about sampling
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