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Dear friends: I use IRAF 2.14, and have two flat images: m920002.fits, m920003.fits.
I use "epar flatcombine" to try to make output with the name Flat. The result is Flat6.fits. So why there is "6" here ? And there is a line:Warning: FXF: EOF encountered while reading FITS file (Flat6).And I try to delete Flat6.fits but it says:
Warning: FXF: cannot delete multiple FITS extension file Does anyone know what is the problem ?Thanks !

The 6 is coming from the keyword used to discriminate different subsets (usually mapped to a keyword like FILTER). Whatever the value it is shortten to the first word. A file, usually subsets, is created that can be used to control the name mapping. So the point is that since flats are filter dependent you can do a batch of flats from different filters with the same root name and they will be created with some extension. This works more obviously if the FILTER value is something like 'B', 'V', 'ha', etc.What probably happened is that the task was run more than once with the same output being produced. Depending on some hidden variable setting you would get an error or it would append the new output as an extension to the previous version. So in your case the latter is probably what happened. So you should delete the file "delte Flat6.fits" and do the flat combine again making sure that if you have multiple sequences you use different root names.Yours,
Frank Valdes