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WFPC2_READ

WFPC2_READ

Name


    WFPC2_READ

Purpose


  Read WFPC2 images in either FITS or STSDAS format into IDL variables.

Explanation


  This a versatile procedure for reading Wide Field Planetary Camera 2
  (WFPC2) images. One can read either multi-extension FITS or STSDAS or
  STSDAS converted to FITS format, and specific
  chip or chips. One can also read all four chips into a "batwing" mosaic--
  so-called because the PC chip (chip 1) has a plate scale of 0.045", while
  the other three WF chips have a plate scale of 0.1"
 

Calling Sequence


    WFPC2_READ,filename,chip1,hdr1,chip2,hdr2,chip3,hdr3,chip4,hdr4
                  or
    WFPC2_READ,filename,chip,hdr, NUM_CHIP = [1,2,3,4], [/TRIM, PATH = ]
                  or
    WFPC2_READ,filename,image,hdr,/BATWING

Inputs


    filename - Name of FITS or STSDAS file with a stack of images from
            the four WF/PC-2 chips, followed by a FITS ASCII
            table with header parameters for each chip. If the file
            name extension ends in 'h' then it is assumed to be an
            STSDAS file. If no extension is supplied, and the file is
            is not found, then WFPC2_READ first tries appending a '.fits'
            extension, and then tries appending a '.c0h' extension.
            The file may als be gzip compressed (with a .gz extension)

Input Keyword Parameters


    NUM_CHIP - Integer scalar or vector, subset of 1, 2, 3, 4, specifying
              particular chip numbers to read. Outputs will be in same
              order as specification of subset. (See Example 2.)
    /TRIM - If set, trim off areas with no image and re-orient so that
              all the chips have a common orientation suitable for insertion
              into "bat-wing" mosaic (no image distortion removal, however).
    PATH - scalar string specifying a !PATH-like list of directories
              in which to search for the file. Default is to look only
              in the current directory.
    /BATWING - Return a 1600 x 1600 array containing all four chips in a
              "bat wing" mosaic formation. This image is mainly for
              display purposes, since the PC chip is compressed to match the plate
              scale of the WF chips. In addition, a small astrometry error
              is introduced since chips do not have the same rotation, nor
              are they aligned at the integer pixel level.

Outputs


    chipN - 800 X 800 image from chip N. If /TRIM is set then the output
              size is somewhat smaller (e.g. 756 x 757)
    headerN - Individual FITS header for chip N with correct astrometry.

Procedures Used


    For FITS I/O: FITS_CLOSE, FITS_OPEN, FITS_READ
    For STSDAS I/O: EXTGRP, FTGET(), SXOPEN, SXREAD()
    Other procedures: CHECK_FITS, FDECOMP, FIND_WITH_DEF(), FREBIN, HEXTRACT,
          HROTATE, SXADDHIST, SXADDPAR, SXPAR()

Example


    (1) Read all four chips of the FITS file u2ou0201t_c0f.fits
 
    IDL> wfpc2_read,'u2ou0201t_c0f',c1,h1,c2,h2,c3,h3,c4,h4
    (2) Note that supplying the .fits extension is optional. Now read only
    chips 1 (the PC chip) and 3. Trim off portions of the arrays where
    there is no image.
    IDL> wfpc2_read,'u2ou0201t_c0f',c1,h1,c3,h3,num=[1,3],/trim
      (3) Note that with the /TRIM option the output chip sizes are no longer
          800 x 800 but odd sizes such as 770 by 753. Now read all 4 chips
          into a 1600 x 1600 "batwing" mosaic
    IDL> wfpc2_read,'u2ou0201t_c0f',im,h,/batwing

Modification History


    Written by W. Landsman, Raytheon STX, for IDL V5.0 June 1998
    Based on code by Robert Hill, Raytheon STX
    Better astrometry of PC image in "batwing" configuration, W. Landsman
                August 1999
    Use vector call to SXADDHIST W. Landsman March 2003
    Don't use EXECUTE() for V6.1 or later W. Landsman Dec 2006
    Assume since V6.1 W. Landsman June 2009
    Ability to read multi-extension format FITS W. Landsman May 2010
    Correct header in MEF form when only reading PC chip. W.L. July 2010



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