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yfit -- Compute Y-deflection calibration coefficients.
yfit cctabin ypostab cctabout
Using a table of Y-deflections as a function of carrousel position
order, this task will determine the coefficients giving the Y-deflection
by using a least squares fit, described as follows:
ydef = a + (b * w) + (c * w * w) + (d * m * w)
w - is the wavelength computed with the carrousel
calibration stored in 'cctabin',
m - is the spectral order,
a, b, c and d - are fitted coefficients. (d is not
used for first order gratings (i.e., it is set
to 0.0) and c is not used for Echelle modes.
- cctabin [file name]
- Name of the input carrousel calibration table that is to be updated.
The carrousel coefficients CAP_A, CAP_B, and CAP_C are copied
directly from the input table
to the output table. The Y-deflection coefficients LIT_A, LIT_B,
LIT_C, and LIT_D are updated by this task.
If cctabin has multiple rows, the first row in which the grating
mode matches that of ypostab will be used.
- ypostab [file name]
- Name of the input Y-deflection table to be processed.
For first order grating
modes, table rows must be supplied for at least four carrousel positions.
For the Echelle mode, at least two carrousel positions, each having two spectral
orders, must be present in the table. This input table is the one generated by
the yfind task.
- cctabout = "cctabout" [file name]
- Name for the output file that will contain the updated carrousel
calibration table produced by this task.
The cctabout table will have one row containing the updated
calibration of the selected row of cctabin.
1. Compute the Y-deflection calibration for the input Y-position
table ypostab.tab. The table oldcctab.tab contains
the previous calibration and newcctab.tab will contain the updated
hr> yfit oldcctab ypostab newcctab
For assistance using this or any other tasks, please contact email@example.com
or call the help desk at 410-338-1082.
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This file last updated on 15 Sep 2011