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).
Launch GMMPS directly with the image name,
or use the File -> Open command in the Skycat menu.
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.