...
If you have DS9 and the XPA messaging system installed, you can set point source locations interactively on a display of a WCS-compliant FITS image using DS9's Regions capability. In order to get ModelEditor.py to communicate with DS9 via XPA, you must first install Russell Owen's RO.DS9 python package. If everything is installed correctly, a "ds9" pull-down menu will be available:
"Display sources" will plot the locations of the current set of point sources on the current DS9 frame, and "Import sources" will add the point sources displayed in the current frame to the list of sources. NB: DS9 must be running for these menu items to have any effect.