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+.help skdecim Mar00 Skywcs
+.ih
+NAME
+skdecim -- open a sky coordinate descriptor using an image descriptor
+.ih
+SYNOPSIS
+stat = sk_decim (im, mw, coo, imcoo)
+
+.nf
+pointer	im		# the input image descriptor
+pointer	mw		# the output mwcs descriptor
+pointer	coo		# the output sky coordinate descriptor
+pointer	imcoo		# the input image sky coordinate descriptor 
+.fi
+.ih
+ARGUMENTS
+.ls  im
+The input image descriptor.
+.le
+.ls mw
+The output mwcs descriptor.  A NULL value for mw is returned if the image
+world coordinate system cannot be read.
+.le
+.ls coo
+The output sky coordinate descriptor.
+.le
+.ls imcoo
+The parent image sky coordinate descriptor. Imcoo is set to NULL
+except in cases where the sky coordinate descriptor for an image is
+transformed and written back to the same image.
+.le
+.ih
+DESCRIPTION
+Sk_decim is an integer function which returns OK or ERR as its function
+value. ERR is returned if a valid sky coordinate system cannot be opened,
+OK otherwise.
+
+Sk_decim returns the image MWCS descriptor mw. The MWCS descriptor is used
+to convert from pixel coordinates to world coordinates and vice versa.
+The MWCS descriptor must be freed with a call to the MWCS routine
+mw_close before task termination.
+
+Sk_decim returns the sky descriptor coo. The sky coordinate descriptor 
+is defined even if an error is detected in reading the image celestial 
+coordinate system, and must be freed with a call to sk_close before
+task termination.
+
+.ih
+NOTES
+Type "help ccsystems" to see the list of the supported sky coordinate systems.
+
+Type "help mwcs$MWCS.hlp fi+" to find out more about the IRAF image world
+coordinate system library MWCS.
+SEE ALSO
+skdecwcs, skdecwstr, skcopy, skclose
+.endhelp