.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
