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Everytime when I restart my computer, I cannot open all imh files that were processed in a previous application. It says "cannot open pixel file xxx.imh"
How can I fix the problem?

What is the value of your 'imdir' directory (i.e. do a "cl> show imdir")?? This is the directory where the pixel files are put when an image is created, and if it is /tmp or /usr/tmp then these directories are normally purged at reboot time. You can reset the value by editing your login.cl file or on the command-line.Using FITS files will avoid this problem (i.e. reset the 'imtype' variable in your login.cl to be 'fits'), an imdir value such as "HDR$pix/" will put the file in the 'pix' subdirectory of the .imh file (it will be created automatically). Write back if this doesn't explain it.-Mike

Thank you very much, Mike. It works fine for my computer now after chaning the imtype to fit. But it seems that when I copy all those imh files to another computer, the same problem appears(cannot open pixel file xxx.imh).Is there anyway to solve the problem or I need to use the same computer all the time?

The IMH format stores the image in a .imh file containing the header information, and a .pix file for the pixels which is stored in the 'imdir' directory. The .imh file contains the path to the .pix file, if you move the files to a new directory/computer you may invalidate this path and so you see the error.Using an imdir such as HDR$pix/ stores the .pix files in a relative directory so as long as you move entire directories of images you don't need to change anything, otherwise on the new machine you'll need to edit the path to the pixfile. This is covered in part in the FAQ at https://iraf.net/faqman/index.php?op=view&t=3 In general, moving images is best done using FITS images.-Mike