fitoffsety -- Correct dispersion coefficients for wavelength offsets.
fitoffsety offtab dcin dcout
This routine corrects dispersion coefficients for spectral offsets found by the waveoffset task. If grating mode data is used, then a least squares polynomial of the wavelength offset as a function of the sample (or diode) position is computed. The coefficients of the fit are subtracted from the corresponding dispersion coefficients (i.e., coefficients for same power of sample or diode position). For the prism mode, only an average diode or sample shift is computed and is then added to the XZERO header keyword value in the dispersion coefficient file (produced by the dispfity task).
1. Correct the dispersion coefficients in the file dc1.tab using offsets in off.tab. Use a quadratic fit to the offsets and place the updated dispersion coefficients in a file called dc2.tab. Reject rows in off.tab that have total counts less than 1000.0.
fo> fitoffsety dc1 off dc2 order=2 mincount=1000.0
Howard Bushouse, STSDAS
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