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 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.
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.

Imaged with the 16" f3.75 Dream Astrograph.
Apogee Alta U-16M camera.
R-HA-O3 image (mapped as RGB)
RGB for the stars
Ha - 30 min ,O3 - 30 min
RGB 10 minutes each

(Total of 1:30 HRS)

Imaged from Tivoli farm in Namibia June 2012.