8.5 CMAP Files

• CMAPs are constructed using the reference celestial coordinates from the IRPH files with no correction for the IIPH pointing jitter which, though small, causes image blur of about 1 .
• As indicated in Chapter 4, straylight generated ghosts can lead to spurious extended features in images. Ghosts seem mainly to affect CVF data with pixels larger than 1.5 (Biviano et al. 1998b, [6]; Okumura et al. 1998, [45]).
• Lens and filter-wheel jitter can lead to imperfect flat-fielding at the edges of CMAPs, where errors up to a factor of 5 may occur.
• In SW observations of a strong source the dark current may be overestimated, which leads to an apparently negative background.