How can I set the coordinate system to be used in the analysis of my image data?

By default, image data sets are read into Sherpa in image ('logical') coordinates. The coordinate system for the analysis may be changed to physical or world using the set_coord command:

sherpa> load_image(2, "image_bin50.fits")
sherpa> get_coord(2)
'logical'
sherpa> set_coord(2, "wcs")

Note: the physical coordinates of non-Chandra data sets may not be recognized in the current version of Sherpa; see the load_image bug page for details.