[fitsbits] Plate Center on POSS2 Plates

[Mark Calabretta]

On Wed 2004/07/28 12:49:49 MST, "K. L. Tah" wrote
in a message to: fitsbits at nrao.edu

>part, these seem not to correspond to the center of the actual fits image
>since they are ~ few minutes different from
>the epoch 2000 coordinates and the star of interest lies fairly close to
>the center (~ tens of pixels from center). Can someone explain this to me?

Sect. 5.2 of FITS WCS Paper IV (draft) discusses this anomaly in some
detail.  http://www.atnf.csiro.au/~mcalabre/WCS, text after Eq. (30) and
again after Eq. (42).

Mark Calabretta
ATNF