Messier 17 - Swan swimming on the sky

Messier 17 - Omega Nebula / Swan Nebula

The Omega Nebula, also known as the Swan Nebula, Checkmark Nebula, Lobster Nebula, and the Horseshoe Nebula (catalogued as Messier 17 or M17 and as NGC 6618) 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.[1]

The Omega Nebula is 5.500 light-years aways from Earth and it spans some 100 light-years in diameter.[2] The cloud of interstellar matter of which this nebula is a part has a mass of 30,000 solar masses. The total mass of the Omega Nebula is an estimated 800 solar masses.[1]

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.[1]

An open cluster of 35 stars 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, 100 of spectral type earlier than B9, and 9 of spectral type O, plus >1000 stars in formation on its outer regions. It's also one of the youngest clusters known, with an age of just 1 million years.[1]

The luminous blue variable HD 168607, located in the south-east part of the Omega nebula, is generally assumed to be associated with it; its close neighbor, the blue hypergiant HD 168625, may be too.[1]

[1] wikipedia, SIMBAD and SEDS
[2] Nasa APOD

This picture was taken in 7th Meeting Brazilian of Astrophotography in July, 2014 - Alto Paraíso de Goiás - Chapada dos Veadeiros - Goiás - Brazil.

Technical data
ISO 800, total exposure of 01h40m (20 subs), darks, flats and biases applied.

Equipment
- Equatorial Mount Orion Atlas EQ-G
- Auto guided with Orion Starshoot and Refractor Orion 80mm
- Refractor Triplet Meade 80mm APO F6
- Canon DSLR 500D modded with Astrodon Filter
- Astro-Tech Field Flattener 2"

Software
Capture: BackyardEOS
Processing: PixInsight 1.8 and Adobe Photoshop CS5

Ps: Stars's spikes were created by crossed wire in front of refractor!