On Friday, June 14, 2002, at 11:10 AM, Chris Albertson wrote: > "Perfect" What a word! I appreciate your reply, and the ensuing discussion, but what I meant by "prefect" was: the same as is calculated by programs such as Starlink, IDL, IRAF, etc. Most of these programs have a way to do this correction in one or two commands and do not worry about whether I am standing on a chair or not! ;) Michael