Globular Star Cluster M-69 (NGC 6637)

The image was taken with an ST-6 CCD camera thru Kopernik's 20-inch telescope working at a focal ratio of F/4.9. This was an 8 minute exposure and the image scale is about 9 x 12.5 arc minutes, or 2.3 arc seconds per pixel.
North is at the top.

Description of M-69 in The Deep Sky Field Guide to Uranometria 2000:

Brightest stars = magnitude 13.2
horizontal branch stars magnitude = 16.2
Concentration: 5 (scale 1{dense} to 12{loose})

Quote from Burnham’s Celestial Handbook:

In moderate telescopes it is a mere hazy spot, however, becoming truly impressive only in large instruments. The apparent diameter is given by various observers as 2' or 3'; it increases to about 4' on long exposure photographs.

M69 was..... found to be one of the most metal-rich globular clusters known. .....the probable distance (is) about 36,000 light years. The absolute magnitude is about -8.1 and the actual diameter about 70 light years.

Quote from Messier's Nebulae & Star Clusters by K.G. Jones:

M69 is a fairly bright but small globular cluster: it appears quite round although the outer margin is a little irregular. It is not, however, very open and it requires a fairly high power to resolve. With a power of 250x the whole cluster breaks up into a large number of faint, evenly spaced stars.

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• M-69, NGC 6637
• Magnitude: 7.7
• Constellation: Sagittarius
• RA: 18h 31m 24.0s
• Dec: -32d 21' 00" Epoch 2000
• Size (mins): 7.1
• Classification: Globular Cluster
  

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George Normandin, KAS

November 12th, 1997