The maximum dispersion to be searched by the automatic line identifier. Specified in unit-per-pixel.
Care should be taken to ensure that the specified dispersion range is sufficiently wide. If in doubt use a wider range than is probably needed. For example, if the actual dispersion is expected to be about 0.5, then a range specified by MIN_DISPERSION=0.2, MAX_DISPERSION=0.8 would be appropriate, whereas a range of 0.4 to 0.6 could possibly be too restrictive.
The normal wavelength units will be Angstroms, but alternative units may be used by providing an appropriate .ARC line list.
Martin Clayton