2. Loading Images

An image for visual reference is always required when designing a mask with GMMPS. The image is either a reduced GMOS/F2 image (pre-image) supplied by Gemini, or a reduced image from a different telescope that has been re-formatted so that it appears as if it was taken with GMOS or F2 (a pseudo-image).

2.1. Loading

Launch GMMPS directly with the image name,

gmmps <image.fits>

or use the File -> Open command in the Skycat menu.


Fig. 2.1 FITS image displayed in Skycat.

2.2. Adjusting the dynamic range

Click on Auto Set Cut Levels or go to View -> Cut levels to adjust the dynamic range. Alternatively, enter Low and High levels. For the low value, choose a number somewhat less than the background value. Pixels exceeding the High threshold will be displayed white.