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. 

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 ofinterstellar 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.

Imaging telescopes or lenses: William Optics FLT98
Imaging cameras: Atik 383L+
Mounts: Skywatcher EQ8
Guiding telescopes or lenses: William Optics FLT98
Guiding cameras: Starlight Xpress Loadstar
Focal reducers: Riccardi Reducer 0,75x
Software: Fitswork 4.44, Adobe Photoshop CS3 CS3
Filters: Baader S2, Baader Planetarium Ha 7nm 2″, Baader O III 8.5nm O3
Accessories: Starlight Xpress 5×2″ Filter Wheel
Dates: June 8, 2014
Frames: 25×900″
Integration: 6.2 hours

Author: Alexander Sielski
AstroPhotography of the day by SPONLI 4 Aug 2014