Three Messier Objects: M20, M21 & M8


Object Type: Emission Nebula, Reflection Nebula & Open Cluster

Scope: Orion APO 80mm
Exposure 120 minutes



Wide field view of 3 Messier Objects. M8 the Lagoon Nebula, M20 the Trifid Nebula and M21 - an open cluster. Click on the links to get more information about M20 and M8 on their respective pages.


Messier 21 or M21 (also designated NGC 6531) is an open cluster of stars in the constellation of Sagittarius. It was discovered and catalogued by Charles Messier on June 5, 1764.

M21 is a relatively young cluster of a mere 4.6 million years of age. It is tightly packed but contains about 57 stars. A few blue giant stars have been identified in the cluster, but Messier 21 is composed mainly of small dim stars. With a magnitude of 6.5, M21 is not visible to the naked eye; however, with the smallest binoculars it can be easily spotted on a dark night.