iraf.net

Zheng,
I just accidently nuked your last message after quickly scanning it.
Let me see if I understand what you want to do: You want to be able to plot
two surface plot simultaneously so that you can see which stars/features
overlap? Is this right?
The SURFACE task contains an 'append' parameter that allows you to
first draw the first plot, and assuming the second plot is on the same scale
you can append the second surface. These plots are not separated 'vertically'
so the overlap may get confusing. Similarly, you could draw a CONTOUR plot
of the first surface and use the append parameter to overlay a second contour
plot. The advantage to contour is that you'll be able to read the cursor
to get the position of a feature, whereas SURFACE wouldn't readback properly.
I don't think the VOL package would help you. It's meant to render
volumentric data (e.g. a density at an (x,y,z) coordinate), but you seem to
have to surfaces (an intensity at an (x,y) coord).
If the append parameter doesn't help then there's nothing else in
IRAF that will stack two surface plots. I believe IDL has this capability,
that may8 be easier than transferring to the mac if you have it around.Cheers,
Mike