M 21 (NGC 6531, Lund 806) Open Cluster in Sagittarius
Located at: RA 18 hours 04 minutes 13 seconds, Dec -22 degrees 39 minutes 51 seconds
Size: 13' (16'); Magnitude: 5.9; Class: I 3 r
North is up
West to the right
| Telescope: |
8" f5 Newtonian reflector |
| Camera: |
ST-8XME, self-guided, binned 1x1, temp -10c, camera control MaxIm DL 4.56 |
| Image: |
Lumicon Deep Sky filter, 150 minutes (15 x 10 minute subs), 09/1/2007 |
| Processing: |
CCDStack 1.3, Photoshop 7.0 |
| Location: |
Rolling Roof Observatory, Thousand Oaks, CA 91360 (+34d 13m 29s -118h 52m 20s) |
| Notes: |
According to "Star Clusters", by Brent Archinal
and Steven Hynes, the size of this open cluster is 16 arc
minutes. From the NGC / IC Project: Contemporary Visual Observation(s) for NGC 6531 NGC 6531 = M21 = E521-SC19 = Cr 363 18 04 13 -22 29.4 V = 5.9; Size 13 17.5": M21 consists of roughly 50 stars in a 5' diameter. Very bright, fairly small although outliers greatly increase the diameter. Includes s wide double star S 698 = 7.9/8.8 at 30". Just N of these stars is a remarkably symmetric ring consisting of a mag 9.5 star and ten mag 12-13 stars. A close mag 14/14 double star is on the W side of the bright double star. Just W is a 10' string of mag 8/9 stars oriented NW-SE including two double stars. M20 lies 45' SW. - by Steve Gottlieb |