Trim To Size
The Trim To Size method is used to crop the images to a smaller size. Trimming, or "cropping" occurs after all quantitative changes (i.e., bias, dark correction, etc.) have been made to the images. This method is part of the Image Calibration pipeline.
The trimming region may be explicitly specified in the dialog or it may be obtained from the image header, as follows:
Keyword option: To let the image header declare the trimming region, check the Keyword option and enter the name of the keyword to use. The keyword can be selected from a list of previously used keywords (click the down-arrow to view previously used keywords). The name TRIMSEC (selected above) is commonly used for this quantity but there is no standard keyword for this purpose. The name DATASEC is also sometimes used.
Range Option: To specify the trim region explicitly, check the Range option and enter the column and row limits. Remember that Mira uses 1-based pixel coordinates so that pixel (1,1) is the origin of the image array. In the example above, the range is de-selected but you can see that the trim region would be [2:1024, 4:1022].
Image Calibration, Methods tab, Crop Image, Image Coordinate System