When it comes to picturing double stars with prime focus of DSLR connected to the same telescope, is it reasonable to believe that the LESS arcseconds per pixel the camera, the BETTER the "gap" between the double is seen, now that for some challenging double stars, the gap seems very narrow. Or is it totally the other way reverse in understanding the mechanism here?
Yep, that's true. The computation is simple, others will probably chime in with that... so I won't steal their thunder. If you want decent visibility separation, or (especially) doing metrology of the Position Angle and separation... you would want ~over-resolution~ beyond the more common Q values recommended for general imagery. That mitigates spatial phase and non-isotropic sampling that otherwise badly degrade such measurements. Other than that... your system needs to reasonably resolve the pair... things like residual system aberrations, seeing, etc.; otherwise all bets are off.
[Daniel Malacara and I did a white paper on this sorta stuff a few decades ago. Couple of excerpts attached. >>>] Tom
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