It takes an UFTI observation comprising nine object frames and a dark frame to make a calibrated, untrimmed mosaic automatically. This recipe works well for faint sources and sparse fields. The flat field is created by combining normalised object frames using the clipped median at each pixel.
Registration is performed using common point sources in the overlap regions.
If the recipe cannot identify sufficient common objects, the script resorts to using the telescope offsets transformed to pixels. The resampling applies non-integer shifts of origin using bilinear interpolation. There is no rotation to align the Cartesian axes with the cardinal directions. The recipe makes the mosaics by applying offsets in intensity to give the most consistent result amongst the overlapping regions. The mosaic is not trimmed to the dimensions of a single frame, thus the noise will be greater in the peripheral areas having received less exposure time.