WSCALE: Compute Wavelength Scale from Indentified Lines

   
Form: WSCALE dest [ORD=n] [TTY] [INT] [redirection]
dest
selects the spectrum for which the wavelength scale is to apply,
ORD=
determines the order of the polynomial expressing the relation between channel number and wavelength,
TTY
sends more extensive output to the terminal,
INT
allows interactive selection of lines. INT implies TTY.
WSCALE calculates the wavelength calibration polynomial using the wavelengths and line centers of the calibration spectrum lines identified by the LINEID command. The resulting calibration is associated with the spectrum specified by 'dest'. The line centers determined with the LINEID command are fit to a polynomial of order specified by 'ORD=n'. If the keyword 'INT' is specified, interactive line weighting can be done. The program will ask for all unspecified parameters.

The resulting wavelength scale becomes associated with the 'dest' spectrum. You can then use the COPW command to associate the wavelength scale with any other spectrum you wish.

Also, note that it is the REVERSE fit which is actually used by the command ALIGN to linearize a spectrum (see below).

Examples:

WSCALE 4 ORD=2
Computes the wavelength scale for spectrum 4, doing a second-order fit to wavelength versus channel number. The resulting wavelength scale is printed on the terminal.

WSCALE 4 ORD=2 >fit.txt:
Does the same as example 1, but this time sending the output to the file fit.txt in the current working directory.

WSCALE 4 ORD=1 INT
Does a first order fit to wavelength versus channel number for spectrum 4. The user can interactively give weights to the identified lines being fit (0 weight discards a line).