[daip] FITS header

[Eric Greisen]

I have done a whole bunch of positions comparing ds9 with aips where I
converted the axis increment to be square at the average.  The short
answer is that ds9 and aips disagree usually by 0.1 arc sec or less
although one point was 0.3 arc sec in Dec.  So I suspect that ds9 is
using the full skew but that these averaged parameters are a rather
good representation as well.

Eric Greisen