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+.help skdecwcs Mar00 Skywcs 
+.ih
+NAME
+skdecwcs -- open a sky coordinate descriptor using an image or system name
+.ih
+SYNOPSIS
+stat = sk_decwcs (ccsystem, mw, coo, imcoo)
+
+.nf
+char	ccsystem	# the input celestial coordinate system name
+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  ccsystem.   
+The celestial coordinate system name. Ccsystem is a either an image system
+name, e.g.  "dev$ypix logical" or "dev$ypix world" or a system name, e.g.
+"J2000" or "galactic".
+.le
+.ls mw
+The output mwcs descriptor. A NULL value for mw is returned if the
+image world coordinate system cannot be read or ccsystem is not an image
+system name. 
+.le
+.ls coo
+The output sky coordinate descriptor.
+.le
+.ls imcoo
+The parent image 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_decwcs 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_decwcs returns the image MWCS descriptor mw if ccsystem is an image
+system, otherwise it returns NULL. 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_decwcs 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
+skdecwstr, skdecim
+.endhelp