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.