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10.5 Inhomogeneous FCS Illumination of PHT-P Apertures

Caveat: In case the FCS calibration of an observation is performed in a non-standard aperture (see Section 5.4) strong deviations up to a factor $\simeq$ 2 of the correct responsivity and thus the derived fluxes can occur. The strongest deviations are expected for the largest apertures of the P1 filters.

ISO Handbook Volume IV (PHT), Version 2.0.1, SAI/1999-069/Dc