NGC 6781 is a nice representative of a cosmic bubble. The planetary nebula lies a few thousand light-years away towards the constellation of Aquila (the Eagle) and is approximately two light-years across. Within NGC 6781, shells of gas blown off from the faint, but very hot, central star’s surface expand out into space. These shells shine under the harsh ultraviolet radiation from the progenitor star in intricate and beautiful patterns. The central star will steadily cool down and darken, eventually disappearing from view into cosmic oblivion. (Source, ESO)

This nebula marks the end of the long life of a sun-like star. Despite the longevity of their parent stars and the very brief lifetime of the nebula (typically less than 100,000 years) such sights are common because sun-like stars are common. The nebula has nothing to do with planet formation, rather the name refers to the telescopic appearance of the nebula. Some planetaries are very bright and their discs look like solar system planets.

A close look at this picture shows some structure in the expanding shell of gas around the star, reminiscent of the much more complex Helix nebula. The nebula we see is the ejected surface of the star expanding into material left from an earlier stage in its decline, when it briefly expanded as a 'red giant'. Irregularities in the earlier ejecta, asymmetrical outburst of the central star and motion of the new nebula through the interstellar medium as well as the star's orientation in space all affect the physical form of planetary nebulae. (Source, AAO)



The image was captured with the Meade 12"LX200, using the Atik 383L+ mono at F6.56. I used Astronomik's 12nm Halpha, OIII and SII narrow band filters. All subs were taken at 1x1 bin, -10C, and 10 minutes each with the exception of the Aug 12th Ha, which were at 30 minutes each.

Ha : 32 subs (5.33hr) on Aug 5th and 6th; and 5 subs (2.50hr) on Aug 12th.

O3 : 16 subs (2.67 hr) on Aug 7th.

S2 : 17 subs (2.83 hr) on Aug 8th.

Processing was done with PixInsight, following (for the most part) kayronjm's tutorial of Feb. 24th. Only Ha was used to develop the Luminance image. Color mix is per Juan's (PixInsight) preference. See below formula.

R = .5S2 + .5Ha

G = .15Ha + .85O3

B = O3

North is up. This is a medium crop, partly to increase subject size and also to minimize vignetting problems. I could not quite eliminate the gradient from left to right in the image.

The improvement in image from the additional 30 minute Ha subs was subtle. However, I was very pleased to see that the 12"LX200 was capable of imaging for that length of time.