To Pit Suetterlin: > Anyway, it would be very nice if you could send me your routines to > compute the direction towards center and to correct for the > distortions - they will be useful in the future. Pit: They are attached to the mail. A short example of how I use it (pasted from IDL): IDL> rdfits, p, 'AR9407_01apr01_093218.fits', /sw IDL> p = p(*, *, 0) ; spot frame IDL> spotpos, 11, -21, julday(4, 1, 2001, 9, 30) Location at 11N 21E Distance from center: 0.459 Cosine mu: 0.888 Angle Center<->North: 156.1 IDL> p1 = destretch_spot(p, 156.1, 0.888)