We use https://mirametrics.com/apphot_optimizer_mvn.php for a high-accuracy SNR calculator. We use the values below for the camera, scope, and site info (on a typical “clear” night):

Once you input those values, make sure to plug in your object magnitude and exposure time for an SNR vs aperture size plot.

Note: The values of gain, readout noise, dark current, extinction, airmass, seeing, and sky mag are chosen to be on the extreme upper-error bounds, so chances are, your data’s SNR will be higher than that estimated here.