|M21: Open Star Cluster (Sagittarius) RA: 18h 04.6m / DEC: -22° 29'.0|
Instrument: 10-inch Starfinder
Sagittarius is home to so many wonderful emission nebulae and bright globular clusters. It is easy to overlook the open star clusters in the area which, by comparison, might seem mundane. M21 suffers by its proximity to the Lagoon and Trifid nebulae. It shares the same low power field with the Trifid nebula. That in itself is almost a guarantee that this cluster will be ignored. That's unfortunate. My drawing of M21 is based on a 129X view (Meade 8.8-mm UWA) in the 10-inch Starfinder equatorial. 58 stars are visible within the 35' field. The two brightest are 8th magnitude with the fainter stars depicted falling at about 13th magnitude. You'll find M21 about two degrees due north of M8. M20, the Trifid nebula, resides 41' to the southwest.
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Revised: February 10, 2002 [WDF]