NGC 6618, Messier 17, M17, Omega Nebula, Swan Nebula in the constellation Sagittarius

RC 12" Astrograph (LRGB)

35' x 35' FOV

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Bigger size: 2000 px
© Velimir Popov & Emil Ivanov 2020

LBN 60, Sh 2-45, Horseshoe Nebula, Swan Nebula, Omega Nebula, Checkmark Nebula, Messier 17, Bennett 108


RA (2000): 18h 20m 47s
Dec (2000): -16° 10' 18″

NGC 6618 is an open galactic cluster surrounded by nebula known as Omega Nebula, Swan Nebula, Checkmark Nebula, Messier 17 or M17. The nebula is an H II region. The M17 complex is a molecular cloud surrounding M17 nebula and is located in the Sagittarius spiral arm (Elmegreen et al. 1979; Reid et al. 2019). The distance to the nebula is about 1.8 – 2 kpc (5870 – 6523 ly).

The M17 nebula is excited by a young (1 Myr-old) loose open cluster NGC 6618 which contains hundreds of stars with spectral types earlier than B9 (Lada et al. 1991). These young stars and causes the gases of the nebula to shine due to radiation from these hot, young stars.

Investigations with the Chandra X-Ray Observatory counted a total of 16000 stars in NGC 6618 (M17) cluster. It is the second most populated cluster after the Carina cluster (Kuhn et al. 2015).

Charts and image details obtained from



Image and FOV details

Details for the image
Center of field RA 18:20:56.29 (h:m:s)
Center of field DE -16:11: 39.8 (deg:m:s)
FOV 35 x 35 (arcmin)
Pixel scale: 1.04 (arcsec/pixel)

RC 12" Astrograph (IRIDA South dome)

Imaging details

Optic(s): RC 12" with Astro-Physics corrector @ f/5 (RC)
Mount: ASA DDM85 Premium
Camera: ATIK 4000 M
Filters: Astronomik II: Lumиnance
Dates/Times: 3.09.2013
Location: IRIDA Observatory, BG, longitude: E 24 44' 18", latitude: N 41 41' 42"
Exp. Details: HaRGB: Ha 4x10 min, R 3x10 min, G 3x10 min, B 3x10 min
  Bin 1, Total Exposure Time - 130 min (2h)
More details: Bias, dark and flat frames reduction
Processing: PixInsight / PS
Copyright: Velimir Popov and Emil Ivanov 2013-2020. All Rights Reserved
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