The imcopy tool in iraf does an excellent job cropping images. It retains the wcs information and even keeps the original pixel indices. I have not been able to reproduce this in IDL. I can do a crop and resave it with the header but then I have to change the crpix, cdelt and naxis values. I am not even sure that this gives and accurate wcs and it assumes you have matched up a pixel location with its coordinates. I tried using modfits but this doesn't change the size of the image. I know there has to be a widget program that makes cropping more straighforward. Does anyone know any? thanks