Messier 69 or M69 (also designated NGC 6637) is a globular cluster in the constellation Sagittarius. It has an apparent visual magnitude of 7.6 and its angular diameter is 7.1 arc-minutes. M69 lies at an estimated distance of 28,000 light years. The Equinox 2000 coordinates are RA= 18h 31.4m, Dec= -32° 21´ which makes M69 best seen during the summer. The Messier Summer Star Chart shows the position of all Messier objects visible during that season.
The image above shows the uncropped view of M69 through the Takahashi E-180 Astrograph (North is to right). A 3x enlargement of this image appears to the right.
In spite of its inclusion in the Messier Catalog, this globular cluster was actually discovered by N. L. Lacaille in 1752. According to Recio-Blanco et al.(2005), the distance of M69 is 36,920 light years and its diameter is 110 light years. Its estimated mass is 300,000 solar masses and it contains 13 variable stars.
Messier's Description of M69
August 31, 1780
`Nebula without star, in Sagittarius, below his left arm and near the arc; near it is a star of 9th magnitude; its light is very faint, one can only see it under good weather, and the least light employed to illuminate the micrometer wires makes it disappear: its position has been determined from Epsilon Sagittarii: this nebula has been observed by M. de La Caille, and reported in his Catalog; it resembles the nucleus of a small Comet.' (diam 2')
- Object: M69
- Other Names: NGC 6637
- Object Type: globular cluster
- Object Data: Apparent Magnitude = 7.6, Angular Size = 7.1 arc-minutes
- Object Position (Equinox 2000): RA= 18h 31.4m, Dec= -32° 21´, Constellation = Sagittarius
- Date/Time: 2011 Oct 20 at 02:00 UTC
- Location: Bifrost Astronomical Observatory, Portal, AZ
- Mount: Astro-Physics 1200GTO
- Telescope: Takahashi Epsilon 180 Hyperbolic Astrograph
- Camera: Canon EOS 550D (Rebel T2i) (modified with a Baader UV/IR filter)
- Field of View: 1.70° x 2.56° at 1.7 arc-sec/pixel (web version: 10.0 arc-sec/pixel)
- Exposure: 4 x 300s, f/2.8, ISO 800
- File Name: M69-01w.jpg
- Processing (Adobe Camera Raw): Graduated Filter, Vignetting Correction, Noise Reduction, White Balance, Curves
- Processing (Photoshop CS5): Average Images, Curves, Noise Reduction
- Original Image Size: 3454 × 5179 pixels (17.9 MP); 11.5" x 17.3" @ 300 dpi
- Rights: Copyright 2011 by Fred Espenak. All Rights Reserved. See: Image Licensing.