The wide FoV of SPI allows the detection of off-axis sources. However it also means that off-axis sources will create a shadowgram on the detector that increases the background photons for the prime target. To remove this background a proper mapping of the source and the surroundings is necessary. This is the main reason why hexagonal dithering should only be used for isolated point sources, where no significant contribution is expected from other sources within about 20 .