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To make these images I used the command:
% SimIm4 N +190.0 Y 1.10 * No, do not print debug messages * Rotate 190 degrees * Flip about the Y axis * Change to a scale of 1.10 arcsec/pixel Here is the header I obtained with hcards_wcs.sh: CTYPE1 = 'RA---TAN' / Gnomonic Projection CTYPE2 = 'DEC--TAN' / Gnomonic Projection CRPIX1 = 100.000 / Axis 1 Reference CRPIX2 = 100.000 / Axis 2 Reference CRVAL1 = 180.000000000 / Ra at Frame, J2000 (deg) CRVAL2 = 32.500000000 / Dec at Frame, J2000 (deg) CROTA2 = 190.000000000000 / Image Twist +AXIS2 W of N, (deg) CDELT1 = 0.0003055555571 / Axis 1 Pixel Size (degs) CDELT2 = 0.0003055555571 / Axis 2 Pixel Size (degs) CRVALE = 50.000 / Combined CRVAL error (arcsec)Our WCS in the final image (right) has been handled correctly: we recover the correct Ra,Dec and our sky compass is pointed correctly. I have applied all three transformations in one pass: the field was rotated 190 degrees, a flip about the Y axis was made, and the scale was changed to 1.10 arcsec/pixel. |