Hi All,
Yep the NGC/IC project is one of the most valuable resources on the whole interweb thingy. One of its best features for advanced observers is that it resolves so many (almost all) of the errors in the original catalogues -- all the double entries, the missing objects, the unknown objects, the mis-identified, the wrong positions etc etc that are still published in an unresolved form in most of the modern observing literature including virtually all planetarium software.
Harold Corwin's notes correcting the NGC are invaluable. Steve Gottlieb's notes on the visual appearance of things through various apertures are also very helpful to the observer. I'm lucky in that I've observed with Steve before and we've compared notes on a lot of things over the years. He is undoubtedly one of the great observers of our time. He happens to follow a similar system to my notes, so when I read his, I've got a very good idea of what he has seen.
Another valuable resource that has just come back up (after being hacked on another web-host) is the Planetary Nebulae Observers Home Page.
It is now at:
http://www.blackskies.org/
and is an equally valuable resource for the PNe observer -- no matter how obscure you are almost certain to find an image or some notes on things. Best of all, the Neat Southern Planetaries essays by Andrew James are back and there too.
Well worth a look ...
Best,
Les D