Thanks Trevor and Greg. I still have an awful lot to learn but we are getting there.
Is there some way to reconstruct a 3D image from 2D data? I have seen it done somewhere.
Here is a full res version with stars. 6MB
http://d1355990.i49.quadrahosting.co...SNR_2P_NII.jpg
As you can see the stars get in the way to see the dim stuff clearly.
With this detail the Vela Supernova Remnant looks eerily like the Crab Nebula.
Crab Nebula. Distance 6500 light-years and about 6 light-years across. 1000 years old. Hubble image is 6 arc seconds wide.
VSNR. Distance about 800 light-years and about 100 light-years across. 11000 years old. My image is 6.1 x 3.4 degrees and there is more of the SNR outside even this FoV.
Large image from Hubble here
http://hubblesite.org/newscenter/arc.../image/a/warn/
Bert