iraf.net

NUMBER: 556
MODULE: splot, sarith, scombine, standard
SYSTEM: -V2.13Beta
DATE: Fri Oct 27 09:33:16 MST 2006

BUG: When matching one spectrum to another, the reference spectrum, for some operation (e.g. arithmetic, combining, standard star calibration) the first spectrum is converted to its natural WCS units. If the reference spectrum is in different units the result will be wrong. This is rare but a particular case is when SPLOT displays a spectrum in some units, possibly set by the display units in the header or by the task parameter, and then a binary arithmetic operation is performed using a second spectrum. Even if the second spectrum has the same display units it may be resampled to match the reference spectrum in the wrong units. The code solution is to always resample in the current units of the reference spectrum.

The workaround for the SPLOT example is to use the ":units" command to put the initial spectrum into the natural units of the second spectrum. After the arithmetic you can changes the units back if desired.

STATUS: Fixed for a future release.