NGC/IC Project Restoration Effort
(This is a very very beta version)
NGC6531
Basic Information
Location and Magnitude
Right Ascension: 18:4:13.3
Declination: -22:30:0
Constellation: SGR
Visual Magnitude: 5.9
Historic Information
Discoverer: Messier
Year of discovery: 1764
Discovery aperture: 3.5
Observational
Summary description: Cl, pRi, lC, st 9…12
Sub-type: I3m
Steve's Notes
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NGC 6531
18" (8/12/10): In the center of the cluster is the brightest member; mag 7.2 HD 164863. This star forms a 30" pair (South 698) with mag 8.7 HD 313693. A third bright star, mag 8.8 HD 164883 lies 1.2' NE of the brightest star and extending in a short line NE are two additional mag 10 and 11 stars. Just north of this central clump is a beautiful ring of a dozen stars mag 9.5-12 stars. ARA 1841, a pair of 12.4/12.7 stars at 8" lies 1.5' WNW of South 698. An incomplete larger ring of stars surrounds the entire group and includes ARA 1841. A total of roughly 50 stars are within 7'.
17.5" (8/10/91): M21 consists of roughly 50 stars in a 5' diameter. Very bright, fairly small although outliers greatly increase the diameter. Includes a wide double star south 698 = 7.9/8.8 at 30". Just north 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 west side of the bright double star. Just west is a 10' string of mag 8/9 stars oriented NW-SE including two double stars. M20 lies 45' SW. Easily visible in 15x50 IS binoculars as a small knot.