Optimum S/N Photometry Calculator
This page will calculate the optimum exposure time and telescope focus to obtain optimum signal-to-noise for photomtery. It takes into account both photon noise and scintillation noise, with detailed calculations involving the camera read noise, sky brightness, etc. Just input the values below and hit submit! If you get an answer that's a better seeing than you can achieve, then the optimum solution is to focus as best as possible.
Please send any suggestions for improvements or any other comments to firstname.lastname@example.org