*.imh and *.qp Extensions - when to use them

The general rule in IRAF is that extensions to image names are not needed. However, with the introduction of QPOE files, both *.qp and *.imh have become defaults to most tasks. A few things to bear in mind for correct results when the extensions are not explicitly given:

• often it is clear from the prompt which extension is expected, e.g.

       sp> qpspec
  

  source qpoe file: xdata$rp110590
  needs a QPOE file.

  However, when in doubt, give the full name with extension.

• when *.imh and *.qp files are both present, most IRAF tasks assume the *.imh file as default. e.g.
  cl> imhead rp90
  reads rp90.imh header, if *.imh and *.qp are both present, rp90.qp otherwise.
• when mixing *.qp and *.imh files, extensions must be explicitly given: e.g.
  im> imcopy xdata$rp110590.qp rp90.imh
• when the name of the image contains a `.', then give the extension explicitly: e.g.
  xdata$rp110590.err.imh
• tasks like imcalc require full extensions to the file names
• when the extension is different from the default one, full names and extensions must be given