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ExampleConsider the example of an ASCA SIS spectrum extracted from a circular region of radius 80 detector pixels centered on the detector coordinate position (430.32,410.60). The rebinning factor used to make the WMAP is 8 (ie WMREBIN is set to 8). The event file specifies the ASCA SIS detector pixel has a size of 0.027 mm so the CDELT1 and CDELT2 are set to . The original detector coordinates have a reference pixel of the center of the array (640.5, 640.5) and assign this a physical position of (0mm, 0mm). The CRPIX1/2 keywords give the WMAP pixel positions of the physical position (0mm, 0mm). The keywords ending in P document the relation between the original detector pixels and the WMAP pixels. Thus CDELT1/2P is 8 for the rebinning factor while CRVAL1/2P give the original detector coordinate position of the WMAP pixel (1,1) (as specified by CRPIX1/2P).
WMREBIN = 8 / Weighted Map rebinning CRPIX1 = 3.687500000000000E+01 / X axis reference pixel DRPIX1 = 6.405000000000000E+02 / original X axis reference pixel CRVAL1 = 0.000000000000000E+00 / coord of X ref pixel CDELT1 = 2.160000000000000E-01 / X axis increment DDELT1 = 2.700000000000000E-02 / original X axis increment CRPIX2 = 3.937500000000000E+01 / Y axis reference pixel DRPIX2 = 6.405000000000000E+02 / original Y axis reference pixel CRVAL2 = 0.000000000000000E+00 / coord of Y ref pixel CDELT2 = 2.160000000000000E-01 / Y axis increment DDELT2 = 2.700000000000000E-02 / original Y axis increment WCSTY1P = 'PHYSICAL' CTYPE1P = 'DETX ' / Source of X-axis CRPIX1P = 1.000000000000000E+00 / X axis reference pixel CRVAL1P = 3.535000000000000E+02 / coord of X ref pixel in original image CDELT1P = 8.000000000000000E+00 / X axis increment WCSTY2P = 'PHYSICAL' CTYPE2P = 'DETY ' / Source of Y-axis CRPIX2P = 1.000000000000000E+00 / Y axis reference pixel CRVAL2P = 3.335000000000000E+02 / coord of Y ref pixel in original image CDELT2P = 8.000000000000000E+00 / Y axis increment OPTIC1 = 6.627222290000000E+02 / X Optical axis in detector pixels OPTIC2 = 5.590184936500000E+02 / Y Optical axis in detector pixels HDUVERS = '2.0.0 ' / Version of format (OGIP memo OGIP-96-001) HDUCLASS= 'ogip ' / Format conforms to OGIP/GSFC conventions HDUCLAS1= 'IMAGE ' / Extension contains an image HDUNAME = 'WMAP ' HDUCLAS2= 'WMAP ' / Extension contains a weighted map HDUDOC = 'OGIP/96-001' / OGIP memo describing format BLANK = -1 / Null value
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