The Dumbbell Nebula (also known as Apple Core Nebula, Messier 27, or NGC 6853) is a planetary nebula in the constellation Vulpecula, at a distance of about 1,360 light years.

This object was the first planetary nebula to be discovered; by Charles Messier in 1764. At its brightness of visual magnitude 7.5 and its diameter of about 8 arcminutes, it is easily visible in binoculars, and a popular observing target in amateur telescopes.

The Dumbbell Nebula appears to be shaped like an prolate spheroid and is viewed from our perspective along the plane of its equator. In 1992, Moreno-Corral computed that its rate of expansion in the plane of the sky was no more than 2.3" per century. From this, an upper limit to the age of 14,600 yr may be determined. In 1970, Bohuski, Smith, and Weedman found an expansion velocity of 31 km/s. Given its semi-minor axis radius of 1.01 ly, this implies that the kinematic age of the nebula is some 9,800 years.

Like many nearby planetary nebulae, the Dumbbell contains knots. Its central region is marked by a pattern of dark and bright cusped knots and their associated dark tails. The knots vary in appearance from symmetric objects with tails to rather irregular tail-less objects. Similarly to the Helix Nebula and the Eskimo Nebula, the heads of the knots have bright cusps which are local photo-ionization fronts.

The central star, a white dwarf, is estimated to have a radius of 0.055 ± 0.02 R☉ which gives it a size larger than any other known white dwarf. The central star mass was estimated in 1999 by Napiwotzki to be 0.56 ± 0.01 M☉. [Source Wikipedia].

CAPTURE Information:

The image was captured with the iOptron CEM120 mount , the venerable Meade 12"LX200 SCT, and my Atik 383L+ mono CCD at F7.16 (2182mm FL).

Image subs were taken through Astronomik's filters R, G and B, and narrowband Ha and OIII.



Note that the R, G and B images were done in August and September of 2018. The Ha and OIII filters were used for subs taken July 2020 (this year).

IMAGE information -- 2018

Red : 19 subs (1.58 hr) on Aug 23rd, and 30th.

Green : 20 subs (1.67 hr) on Aug 30th.

Blue : 20 subs (1.67 hr) on Aug 30th and Sep 1st.

All 2018 exposures were at 5 minutes (300s) each, 1x1 bin and -10C.

IMAGE information -- 2020

Ha : 42 subs (14.00 hr) on Jul 19th, Jul 22nd and Jul 23rd.

OIII : 43 subs (14.33 hr) on Jul 18th, Jul 20th and Jul 23rd.

All 2020 exposures were at 20 minutes (1200s) each, 1x1 bin and -10C.



Processing was done with PixInsight, following (for the most part) kayronjm's tutorial of Feb. 24th from several years back.

Both Ha and OIII were combined after integration, crop and DBE using PixelMath and the formula “mean(Ha,O3)”.

The goal was to develop a luminance that captured all of the unique qualities of both the Ha and OIII images. Not sure this worked all that well. Then the older (2018) R, G and B were used for the color mix.

North is up (pretty sure), and this is a very slight crop due to the various movement of different subs.

COMMENTS:

I’ve returned to this target a few times. Although bright and colorful, it has really proved difficult for me to highlight the faint nebulosity surrounding the nebula proper.

I see that I had generated a pretty good image in 2018 (from which I borrowed the color), but did not display it in my galary on the Astrobin site. No idea why.