Loading other images (not DSS, NED or 2MASS)

Warning: All FITS images are not created equal. Depending on the source, an image may have excellent astrometry or practically none at all.  If your image does not have a proper World Coordinate System (WCS) defined, you can follow the instructions below for creating one. For final preparation of observations using small apertures, you must be sure to do a plate solution and transfer the appropriate reference frame to your images.

[Note to HST observers: For HST the  "appropriate reference frame" is the Guide Star reference frame. This means that the reference star coordinates and plate solution should come from a DSS image of the field. This accurate a reference frame is only required for Phase 2.]

Images without a WCS

In order to properly display both coordinates and orientations, all images loaded into the VTT need to have a proper WCS defined.  For images obtained from the DSS, NED or 2MASS, the WCS system is present, but for other images (e.g. personal ground based images), this information may not be present (or may be present in a way the VTT cannot interpret).  To make such an image readable by the VTT, first rotate the image to make North up and East to the left, if appropriate.  Then add the following keywords to the header: The reference point should be some star in the field for which you have accurate coordinates.   Note that the accuracy of the astrometry depends heavily on the accuracy of the plate scale values, and on the orientation of the image (i.e. any offset between the Y-direction and true North will result in coordinate and overlay errors). To get a feel for the quality of your astrometric solution, display the GSC catalog.

HST Images

The WCS keywords are already present in HST images. However, the images are not in a format which can be ingested directly into the VTT. To read in HST data, first copy the specific image you want into a single fits image: