Distortion

[ALAIN MAURY <maury@ocar01.obs-azur.fr>]

If I understand correctly Mark IV wil use stare images with fast
readout ( no scan ).
If one goes with 400mm focal length, 8 arc second per pixel, and
almost 5 degrees of field of view, I do believe there will be plenty
of reference stars near each interesting object to be measured,
plus the astrometric reduction package takes the distortion into
account. Maybe necessary to use higher order terms than 1st or
2nd which are usually used with CCDs, but should be no problem overall.
Alain