Arcseconds per pixel from your camera's pixel size and telescope focal length, with sensor field of view and a seeing-based sampling verdict.
Pixel scale = 206.265 × pixel size (µm) ÷ focal length (mm), in arcseconds per pixel. For deep-sky work aim to sample the seeing at about a third to a half (Nyquist): with 2″ seeing, a scale of 0.67-1″/px is ideal. Much finer is oversampled (wasted resolution, dimmer pixels); much coarser is undersampled (blocky stars).
206.265 × pixel size in microns ÷ focal length in mm gives arcseconds per pixel. A 3.76 µm camera on a 530 mm scope works at 1.46″/px.
For deep sky, about a third to a half of your seeing: with typical 2″ seeing that is 0.67-1″/px. Planetary imaging with lucky-imaging techniques goes far finer (0.1-0.25″/px) because video stacking beats the seeing.
Oversampled means many pixels per star: no extra detail (the atmosphere is the blur), just dimmer pixels and bigger files. Undersampled means stars land on too few pixels and look square. Well sampled keeps detail and sensitivity in balance.