[Issues] astrometry failing near the RA=0 line (repeated send)

Dave Wilman dwilman at mpe.mpg.de
Tue Sep 5 12:25:22 CEST 2006

Dear issues,

We have discovered a disconcerting effect with astrometry:

When we have a focal plane which overlaps the RA=0 line (e.g. the polar
field), ldac records an error (No Reference Stars found) for the chips
which lie entirely on the other side of the RA=0 line to the telescope
pointing. I expect there is an issue with the criteria used to define the
range of RA expected for these chips (i.e. not subtracting 360). Otherwise
it may also be a problem with the non-cartesian space close to the pole. I
am not sure: I expect someone in the Netherlands has come across this
problem before when performing astrometry on polar fields. Is this a bug,
or is there a simple solution?


Note: I sent this a second time since it did not appear to generate a mail
to the list the first time (yesterday)

David Wilman
Max Planck Institute for Extraterrestrial Physics
Garching bei Muenchen
Tel: +49 (0)893 0000 +3117
Fax: +49 (0)893 0000 +3495

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