1. Data reduction
  2. Data reduction

Data reduction

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Data Reduction Files

The script " wprep.cl" is an IRAF script for preparing raw WHIRC data for reduction: renormalizing by the number of Fowler samples; linearity correction; recalculation of the WCS coefficients to include any offsets in the instrument rotator angle; trimming off the unused reference pixels.NOTE: The rotator offset changed by about 0.8 degrees somewhere between June and November 2009. During the summer shutdown in 2012, the header units for the rotator angle (ROTANGLE) and rotator offset (ROTOFF) were changed from radians to degrees! The script " wprep.cl" has been updated to reflect the new WCS values from 2009 and the change in header units in 2012. Data taken previous to June 2009 should use the " oldwprep1.cl" script for a reasonable fit to the coordinates. Data taken between November 2009 and June 2012 should use the " oldwprep2.cl" script. Note that " oldwprep2.cl" and " wprep.cl" are the same for ROTOFF=0. No other changes have been made to the script.

The script " decfix.cl" is an IRAF script for correcting an XTCS error which affected WHIRC data taken prior to June 2009, resulting in an incorrect conversion of negative declination values from sexigecimal to decimal. The header value CRVAL2 was incorrectly calculated in that the minutes and seconds components were assigned positive values. Thus a declination of -03:45:00 would appear as CRVAL2 = -2.25000 rather than -3.75000. This script calculates the correct decimal value and edits the CRVAL2 value. There is no problem in executing the script on data with positive declinations or data taken after June 2009, since it will not change the value of CRVAL2.

The FITS file "whircpupil.fits" (in gzipped format) is a generic pupil ghost template used with the IRAF task mscred.rmpupil which seems to effectively remove the pupil ghost from WHIRC flats. The bad pixel file "pupmask.pl" restricts the task to the central 600 × 600 pixel region of the array.

The FITS file "bpix.whirc.fits" (in gzipped format) is a bad pixel map generated from high and low intensity flatfields. While observers may desire to utilize their own data for generating a bad pixel map, this file may be sufficient for most data reduction.

Field Distortion Data

The Zemax distortion files were generated from the optics model of WHIRC and WTTM. These were edited to yield the text files used in the IRAF task geomap to generate the database files, both of which are used in the task geotran to remove the distortion.

richard.joyce@noirlab.edu
01 October 2013

Updated on June 24, 2022, 11:49 am