IMWCS Using HST GSC

This shows the alignment of HST Guide Stars with a test image before the world coordinate system has been fit. The coordinates plotted are based on the telescope pointing direction (RA and DEC in the image header), the image plate scale (SECPIX in the image header), and the image size (NAXIS1 and in the image header.

[Image] [Image with Nominal WCS] [ID] [Image with Fit WCS] [ID]

Open circles with 5 arcsecond radii represent the positions of stellar objects and X's with 5 arcsecond arms represent the positions of nonstellar objects in that catalog. They are also identified with their region and number. The dots are sources in the image.