GET-SPECTRUM-FROM-MAP

Fetch a given spectrum from the map file. The spectrum to be fetched can be specified in one of three ways:

1. By its position in the map file (use LIST-MAP to determine which one you want)
2. By its position on the sky, specified in RA and Dec. offsets.
3. By its position on the sky, specified in X and Y offsets in the map frame.

Examples:

    >> get-spectrum-from-map<CR>
    Position in file? (<CR> to select by sky position) 1<CR>
    ..

    >> get-spectrum-from-map<CR>
    Position in file? (<CR> to select by sky position) <CR>
    R.A. and Dec. offset? (arcsec) 0 0<CR>
    Offsets in map coordinates:   0.0000000E+00  0.0000000E+00
    ..

    >> get-spectrum-from-map<CR>
    Position in file? (<CR> to select by sky position) <CR>
    R.A. and Dec. offset? (arcsec) <CR>
    X and Y offsets? (arcsec) -10 -10<CR>
    ..