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9.4 Aperture Size

SWS has three apertures (four if the virtual Fabry-Pérot aperture is counted) of different sizes and, for the grating, four detector bands each with detectors of different sizes. This causes an effect when switching between apertures/detector bands. The fluxes of extended sources may change as the apertures/detector bands change, due to the different areas of the sky observed. The fluxes of point sources may change if the entered coordinates are incorrect by a few arcseconds, as the apertures are slightly offset with respect to each other. For more information about apertures see Section 8.2.

ISO Handbook Volume V (SWS), Version 2.0.1, SAI/2000-008/Dc