Hi Robby and Itchy,
yeah I didn't want to say previously..... but since you have said it for me.
I certainly do and always have believed we have been "conditioned" over the past several decades (the film era) to expect to see nebula as red (or a hue thereof).
I don't really agree that all emission nebulae are just glowing in
H-alpha (red) I think some glow in
H-beta as well. H-beta is in the
green part of the spectrum ! Don't get me wrong I'm sure lots of nebulae are just emitting
Ha.
After Robbys posts on this thread I rechecked my images of the Tarantula to see if I could make it all red - but that would have meant removing all the photons collected in the green channel - which didnt make sense to me. I mean to say - if the camera collected strong photons in the green region of the spectrum then according to the data this nebula (2070) is glowing in
green as well as
red.
I guess this could be checked by seeing if the Tarantula is known to glow in
Hb as well as
Ha.
On this issue - you may note the amount of green I managed to get in a previous image of the Helix nebula at this location
http://www.skylab.com.au/pmsa/Helix%20Nebula.html
I can say with certainty that the same camera on my 8-inch f/6 reflector basically did not reveal any green in the Helix (I'm using the 12-inch f/5 now) even with longer exposures.
Great talking to you guys
Paul Mayo