Specifies the threshold level for the treatment of sky-line candidates in the wavelength-dependent sky model produced when TUNE_SKYXPLY is greater than zero.
In this case, any pixel whose intensity differs from the fit by more than TUNE_SKYLTHR * fit-sigma will be treated as a sky-line candidate, and its actual intensity entered into the model in place of the prediction. The same procedure is also applied to the pixels TUNE_SKYLINW nearest neighbours to ensure that the entire sky line is entered into the model even when its wings are within the sigma constraint described above.
INITIAL SUGGESTED VALUE: 3.0.
Martin Clayton