flats.html

Creating Spectroscopic Flat Fields

First, we edit the Sflats parameter file to make sure that we use the proper values for the wavelength range, noise, and gain.

editpar Sflats
./Sflats.par

type q to end

minlambda           4800.000000       min wavelength of extraction
maxlambda           7800.000000       max wavelength of extraction
telscale              2.899000       telescope scale sec per mm
bias_file                 none       bias level file
siglimit              4.000000       CR rejection threshold in sigmas
noise                 4.100000       CCD read noise
gain                  0.470000       CCD gain
order                        5       order of flat intensity fit
fit_mode                median       method of spectrum fitting
med_box                    100       size of sky fit median box
shuffled                     0       number of pixels to shuffle data

Then we can run the Sflats command below to generate a normalized flat-field frame, called ift0011_flat_cX.fits, where X goes from 1 through 8. Figure 7 shows a section of the resulting processed flat-field frame.

Sflats -m ift0012 -f ift0011

**Figure 7:** Section of spectroscopic flat-field frame generated by Sflats.

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Edward Villanueva 2014-08-27