exposure time calculator

The pt5m exposure time calculator (ETC) allows you to calculator object counts, sky counts and signal-to-noise ratios, based on the predicted throughput of the telescope and instrument. The peak signal per pixel is calculated by assuming the seeing disc has a two-dimensional Gaussian profile, with the number of pixels contained within it calculated by assuming it is a circle of radius 1.5 times the seeing. The extinction and sky brightness values have been taken from the ING ETC: signal.