co - combine two stacks				RWW

co		combine stacks 1 and 2.
co 25		combine stack 25 of the current directory with stack 2.
co 40 65	combine stack 40 and 65 of the foreground directory and
		put the result in stacks 1 and 2
co add: dc:	add together stacks 1 & 2 and don't check whether the
		positions are the same.
co ac:		combine stacks 1 and 2 aligning the center channels. Don't
	  	perform any shift in frequency (velocity). This is useful
		for sources whose LSR velocities change with time, like


Combine averages the data in two stacks using the weight of each
channel in the average so that the snr is maximized. The new total
weight is put in each chan.  If the weights of the chans of a stack
aren't equal, you must be careful to removing a good baseline before
combining with other data or a step will be introduced where the weight

Co works on stacks 1&2. The result is put in both 1&2 and the plot flag
is set so that a plot will be generated at the end of the command

If you specify that stacks other than 1 and 2 are to be used, co will
first retrieve them into stacks 1&2 in the order you give.

Before doing the combination the header values of the two stacks are
checked for compatibility. If any differences are found they will be
printed and you will be asked if you want to proceed.  The dc: flag
may be used to suppress the position check.

The stacks will be aligned so that differences in center chan, freq,
and velocity are properly resolved. The alignment of stacks 1&2 will be
done so that as many channels of stack 1 will be kept as can be without
losing any of stack 2. If it is not possible to fit any channels of
stack 2 into the same 512 chan stack as stack 1, an error message will
be given and the new stacks 1&2 will be left as they were.

The add: flag causes co to sum stacks 1 and 2 rather than the usual
weighted average.  This is useful for summing the flux of a source or
obtaining an average spectrum.

This document was last updated on Tue Oct 17 16:24:05 EDT 2000 by Marc W. Pound.