The Omega Nebula, also known as the Swan Nebula (catalogued as Messier 17 or M17) is an H II region in the constellation Sagittarius. It was discovered by Philippe Loys de Chéseaux in 1745. Charles Messier catalogued it in 1764. It is located in the rich starfields of the Sagittarius area of the Milky Way.

The Omega Nebula is between 5,000 and 6,000 light-years from Earth and it spans some 15 light-years in diameter. The cloud of interstellar matter of which this nebula is a part is roughly 40 light-years in diameter and has a mass of 30,000 solar masses. The total mass of the Omega Nebula is an estimated 800 solar masses.

It is considered one of the brightest and most massive star-forming regions of our galaxy. Its local geometry is similar to the Orion Nebula except that it is viewed edge-on rather than face-on.

The open cluster NGC 6618 lies embedded in the nebulosity and causes the gases of the nebula to shine due to radiation from these hot, young stars; however, the actual number of stars in the nebula is much higher - up to 800, plus over a thousand stars in formation on its outer regions. It is also one of the youngest clusters known, with an age of just 1 million years. The Swan portion of M17, is said to resemble a barber’s pole.

The first attempt to accurately draw the nebula (as part of a series of sketches of nebulae) was made by John Herschel in 1833, and published in 1836. He described the nebula as such:

“The figure of this nebula is nearly that of a Greek capital omega, Ω, somewhat distorted, and very unequally bright. ... Messier perceived only the bright eastern branch of the nebula now in question, without any of the attached convolutions which were first noticed by my father. The chief peculiarities which I have observed in it are — 1. The resolvable knot in the eastern portion of the bright branch, which is, in a considerable degree, insulated from the surrounding nebula; strongly suggesting the idea of an absorption of the nebulous matter; and, 2. The much feebler and smaller knot at the northwestern end of the same branch, where the nebula makes a sudden bend at an acute angle.”

A second, more detailed sketch was made during his visit to South Africa in 1837.

Sketches were also made by William Lassell in 1862 using his four-foot telescope at Malta, and by M. Trouvelot from Cambridge, Massachusetts and Edward Singleton Holden in 1875 using the twenty-six inch Clark refractor at the United States Naval Observatory. [Source: Wikipedia]

The image was captured with the venerable Meade 12"LX200, using the Atik 383L+ mono at F7.16 (i.e. 2182mm FL). Astronomik's Luminance, Red, Green and Blue filters were used. Imaging subs were taken at 1x1 bin, -10C, and 7 1/2 minutes each for Luminance and 10 minutes each for R, G and B. Shorter subs of 60 seconds were each taken for L, R, G and B, and combined with the longer versions. This was done to broaden the dynamic range and minimize star center "blow-out".

Image --

Lum 450s: 24 subs (4.00 hr) on Aug 8th and Aug 9th.

Lum 60s: 18 subs (0.30 hr) on Aug 9th.

Red 600s: 13 subs (2.17 hr) on Aug 6th and Aug 7th.

Red 60s: 17 subs (0.28 hr) on Aug 9th.

Green 600s: 13 subs (2.17 hr) on Aug 6th and Aug 7th.

Green 60s: 16 subs (0.27 hr) on Aug 9th.

Blue 600s: 11 subs (1.83 hr) on Aug 6th and Aug 7th.

Blue 60s: 16 subs (0.27 hr) on Aug 10th.

Processing was done with PixInsight, following (for the most part) kayronjm's tutorial of Feb. 24th. Only L was used to develop the Luminance image. R, G and B were collected for the color mix. Narrow band filters were not used on this project, although they may be added later.

North is up, and this is a very slight to medium crop due to the misalignment accumulation from so many different filters and times.

I am fairly pleased with the outcome. This was a good use of PI's HDR Composition tool for combining long and short exposures. Without the shorts, there were definite star center blow-outs.

My images had been suffering from optical ghosts/reflections that could not be fully processed out. This was commented on in my M16 Eagle Nebula image. The good folks at Starizona had me send them the SCT Corrector and found that one of the lenses did not have proper coating. This was replaced by them and the above image shows no signs of this problem.

Now, if I could just keep the stars round......