astronebulee I'm undersampling with my images if they are this value or higher?
HFD of 2 is pretty good sampling wise, Lee; if it were 6, then you would be oversampling (i.e, more than two pixels per star diameter) and not getting anything in return (i.e., resolution already limited by Dawes limit and telescope aperture).
Don't worry too much about under/oversampling with DSO. When you oversample, the star's photons is spread over more pixels; however, notice that the sky noise is also spead over (the same) more pixels.
I.e., the signal to noise ratio of your nebula, when compared to the sky background is pretty much unchanged.
What changes is the nebula versus the camera's dark current, read noise and quantization noise of the ADC. With typical suburban skies, those are small compared to the noise from the sky background (i.e., if your average ADU is over even just 5K).
As long as you are within a factor of 1.5 either way, I wouldn't lose sleep over it. The difference between a low end filter and a high end filter will make a bigger difference than minor under/oversampling for us suburban dwellers.
Chen
