It takes an observation comprising nine object frames and a dark frame to make a calibrated, untrimmed mosaic automatically. This recipe aims to keep pace with the pipeline's incoming data. It works well for faint moving sources and in moderately crowded fields. It should not be used for frames where the telescope guided on the moving object. The flat field is created by combining normalised object frames using the median at each pixel.
Registration is performed using the telescope offsets transformed to pixels.
Once the offsets are determined, they are adjusted for the motion of the target, so that the final mosaic registers the target, not the background stars. There is no resampling, merely integer shifts of origin. 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. For each cycle of nine, the recipe creates a mosaic, which is then added into a master mosaic of improving signal to noise.