====Dome Flats====
[[File:dome_flats.jpg|thumbnail]]
Dome flats give a measure of the pixel-to-pixel sensitivity variations over the CCD. The dome's white flat-field screen is not perfectly evenly illuminated by the lamps on the top end of the telescope, but the light goes through the slit, gets collimated, diffracted and re-focussed, so that is not a problem. We do not use the sky for this as you would get spectra of the Sun!