Gain Maps #2
Description
Discussed with Angus: Add option to read in a gain map. Mathematically this is strictly required to get the correct poisson statistics for photon error (i.e. shot noise). The sigma map only tells you about the error in the sky, and this can be reconstructed from the sky RMS, whereas the gain cannot. Longer term surveys should be providing image, sigma and gain maps to ESO, so it would be useful to deal with these consistently.
Aaron R