Re: (IAAC) Colour in M27
Below is a compendium of all my observations of M 27, I never
saw a brown edge to it, but lots of reports of green color.
(I would have responded more quickly if color had been spelled
NGC 6853 is also M 27, the Dumbbell Nebula. It is the most easily
seen planetary nebula in the sky. The Helix and the Owl have low
surface brightness and the Ring is much smaller. This object is easy
in the 10X50 binoculars as a small cloud afloat in the Milky Way. I
have always been fascinated by the Dumbbell and have looked at it
every Summer since I first learned the skies. The central, bright
"Dumbbell" section is obvious in my 13". On a night I rated 9/10 the
dimmer nebulosity stands out unmistakably and makes the total
circumference of the nebulosity appear round. This effect is more
pronounced in the UHC filter at 135X. Lord Rosse drew the Dumbbell in
the 72" Leviathan and he included 18 stars involved in the nebula. I
have tried with several large scopes to match that number and have
never quite caught up with the Third Earl of Rosse. Using my old 17.5"
Dobsonian at 7000 ft. in the mountains near Flagstaff, I could pick
out 10 stars within the Dumbbell. On an excellent night in Mayer, Az.
at Richard and Helen Lines' Observatory their 20" f/6 Newtonian could
reveal 13 stars, one of the easiest being the very hot (85,000 degrees
Kelvin) 13.5 mag central star. Both of those large scopes at about
250X would show some light and dark areas within the nebula. This
strikingly beautiful planetary is lime green in all the telescopes
Camp 613 13" 9/10--easy in 11X80, 60X--lovely light green neb.
afloat in the Milky Way, rectangular shape elongated 1.5X1 PA 165.
150X--favorite view, bright, large, elongated, stellar nucleus,
sixteen stars involved, several of the faintest with averted vision
only, nebula is brightest on south side. Loops of nebula extent out
from rectangular central section, using the UHC filter fills them in.
330X--"horns" are not nearly as prominent but stars involved are
easier--still 16 counted. Very center around central star is
subtly darker than rest of the nebula-not much, but noticeable.
Ultimate Star Party, McDonald Obs. S=6, T=8, 36" f/5--
M 27 20mm; 17 stars counted involved; horns and football shape
obvious. A light lime green at all times.