Selecting a filter & instrument combination from the pull-down menu automatically fills in the appropriate pixel size, read noise, sky counts, and magnitude zero-point. Or, you can enter them manually if your favorite is not among the choices. For point sources you set the aperture size -- roughly 1.3 times the expected FWHM should be close to optimal. Then set two of the bottom set of parameters and click compute to get the third. MMT Megacam updated 1/09. SWIRC updated 02/07 (note: SWIRC assumes mags on the 2MASS (Vega) system; for AB mags you must add 0.6 in Y, 0.9 in J, and 1.4 in H). Magellan Megacam added 4/10. MMTCam full moon numbers added 4/13 (MMTCam assumes default 2x2 binning).