All of the HRC filters are available for coronagraphic observations. However, there are only a few that have been used in the past in this mode, and can be considered well-characterized. These are F435W, F475W, F606W, and F814W. The first three have produced good results and can be considered "safe" choices.
Filter F814W has been problematic, however. Because the PSF is larger at red wavelengths than blue, less of the light from the central star is blocked by the occulting spot. This makes the residual PSF more sensitive to spot shifts and misalignments of the star behind the spot. Mismatches between target and reference PSF star-to-spot alignments may cause significant subtraction residuals. Also, F814W images suffer from the red halo, which still affects coronagraphic observations because the central spot is filled with light that will be scattered to large radii. Color differences between the target and reference PSF stars will thus cause differences in the halo pattern, altering the local background level in unpredictable ways. If multicolor images are needed, it may be safer to choose F435W and F606W rather than F606W and F814W, for instance. Of course, for red objects it may not be feasible to choose a blue filter due to low flux levels, in which case F814W must be used.
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