M27 (NGC 6853), The Dumbbell nebula.
This was the first planetary nebula to be discovered, by Charles Messier,
on the 12th July1764, and was first compared to a dumbbell by John Hershel.
Our view of it is along its equator
from the pole it is thought to
look like a ring, similar to the famous 'ring nebula', M57.
It is bright enough to be seen in binoculars, having a magnitude of 7.5
and a diameter of 8 arcminutes.
Expansion rate 31km/s, making it roughly 10,000 years old. (there are
a number of estimates ranging from 3000 years to 48000 years)
Central white dwarf ( magnitude 13.5) is believed to be larger than any
other white dwarf known, with a diameter of approximately 48000 miles.
It is very hot, with a surface temperature of about 85,000K.
It lies in the constellation of Vulpecula, and is at a distance of 1,250
light years, so we are seeing it as it was just before the Vikings invasions
started in earnest in Great Britain.
Click on image below for full size
This is a false colour image, comprising of a blend of red and Ha for
the red channel, green, Ha and OIII for green, and Blue and OIII for the
The combination of Ha and OIII with the green is something that I find
works very effectively in this object.
The extended outer halo was something that was very hard to capture from
my light polluted home site, and even with NB filters, was only barely
above the background sky glow. In order to bring it out, I ended up shooting
a whole night each of OIII, binned 2x2 to increase sensitivity, and Ha
binned 1 x 1, just for the halo.
No luminance layer was used.
TMB 152@ F8. Atik 16HR.
Red-10 x 10 minutes. Green-10 x 10 minutes. Blue-18 x 10 minutes. Ha-26
x 15 minutes. OIII-9 x 10 minutes binned 1x1, 13 x 15 minutes binned 2x2.
Total imaging time. 17hrs 35 minutes.
Imaged on the 17th, 19th & 23rd June, and 4th, 10th & 23rd August