OPEN CLUSTER IN SAGITTARIUS
(Image Centred at ra 18h:19.9m / dec -17:08)
June 2014 - Home Backyard in Martinez, Buenos Aires, Argentina
TYPE: Open Cluster
Apparent magnitude: 6.9
Apparent diameter: 9 arc minutes
Distance: 4900 light years
SCOPE: 8" Orion Optics UK with Televue Paracorr
CAMERA: QSI 583 WS
FILTERS: Baader LRGB, 2" IDAS LPS for all channels
SKY CONDITIONS: urban skies
EXPOSURES: LRGB (40,30,30,30)
OBJECT DESCRIPTION AND IMAGE SESSION
Located in the northern area of Sagittarius near the limit with Serpens, Messier 18 is a poor open cluster showing over a dozen of fairly bright stars in a linear diameter of 17 light years. This object does not get too much attention because it is situated in an area of impressive objects.
From the earth perspective it is situated in an imaginary line between Messier 24 and 17. With 7x binoculars it can be seen in magnitude 5 skies as a faint glow; with an 80 mm refractor and the cluster looks small and round.
The age of the cluster is calculated in 32 million years, so it is considered a young cluster. Charles Messier catalogued M18 in June 1764