The command CALIBRATE/LONG determines the dispersion relation
for each row of the spectrum. In addition, a bivariate dispersion
relation is computed if the keyword
is set to
YES, as in:
Midas...> SET/LONG TWODOPT=YES
Midas...> CALIBRATE/LONG
The command CALIBRATE/LONG determines row-by-row
polynomial solutions of degree
stored in the
table coerbr.tbl and fits a 2-D
polynomial of degree
to the lines
with entries in columns :X, :Y, and :WAVE of table line.tbl.
The coefficients of the 2D polynomial are stored in
the keyword
.
The program performs a final oulier rejection which eliminates all
lines with residuals larger than
pixels (if TOL is
positive). However the minimum number of lines in any given row will be
+2. If this number cannot be obtained, a polynomial
of lower order will be fitted. Three more columns are added to
the table line.tbl:
| :WAVE | identified wavelength |
| :WAVEC | wavelength computed from polynomial fit |
| :RESIDUAL | (= :WAVEC - :WAVE) Residual of polynomial fit from |
| the tabulated wavelength) |
NoteFor a proper calibration, images should preferably have positive step descriptors and the wavelength should increase from left to right.