Dr Paul Leyland

Thanks Nick, this sounds very much like what I’m looking for.  As for using the CLI, that’s what I generally do anyway.

This morning I kludged up a Perl script to modify the CRVAL[12] cards in the FITS headers in attempt to persuade SWarp to  stack the images with an offset.  Not very successful though.  Ether I screwed up the code or the total exposure just wasn’t long enough because I can’t see anything circular on the stacked image — just lots of trailed stars.