Makee: Night-Sky-Line shift Plots

The night-sky-line shift plots ( show the residuals of the wavelength scale shift to known and measurable night sky emission lines. (Here is a list of the sky lines which may be used: skylines.txt .) A single number is found (in pixels) for each exposure and this shift value is applied to the polynomial wavelength scales of each order.

Under some conditions, no skyline shift is applied, e.g. too few lines (<5), high RMS in fit (>0.4 pixels), short exposure (<420s), or a high RMS/shift ratio (>4). These conditions are noted in the makee output log.

The shift used is recorded in the FITS header as "SKYSHIFT", see also "SKYSHMEA" for the measured sky shift, "SKYSHRMS" for the RMS in the fit, and "SKYSHNPT" for the number of points (lines) used.

You can look at the plot file to see if the shift (or lack of shift) is appropriate. You can override the value (or lack of value) using on the makee command line using the "-noskyshift" or "skyshift=" options.

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