Messier 92 or M92 (also designated NGC 6341) is a globular cluster in the constellation Hercules. It has an apparent visual magnitude of 6.4 and its angular diameter is 11.2 arc-minutes. M92 lies at an estimated distance of 26,700 light years. The Equinox 2000 coordinates are RA= 17h 17.1m, Dec= +43° 08´ which makes M92 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 M92 through the Takahashi E-180 Astrograph (North is up). 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 J. E. Bode in 1777. According to Recio-Blanco et al.(2005), the distance of M92 is 27,140 light years and its diameter is 110 light years. Its mass is estimated to be 400,000 solar masses and it contains 20 variable stars. The age of M92 is 12 to 14 billion years.
Messier's Description of M92
March 18, 1781
`Nebula, fine, distinct, and very bright, between the knee and the left leg of Hercules, it can be seen very well in a telescope of one foot. It contains no star; the center is clear and brilliant, surrounded by nebulosity and [it] resembles the nucleus of a large Comet: its brightness, its size, approach much that of the nebula which is in the girdle of Hercules. See No. 13 of this Catalog: its position has been determined, by direct comparison with the star Sigma Herculis, fourth magnitude: the nebula and the star are on the same parallel.' (diam. 5')
- Object: M92
- Other Names: NGC 6341
- Object Type: globular cluster
- Object Data: Apparent Magnitude = 6.4, Angular Size = 11.2 arc-minutes
- Object Position (Equinox 2000): RA= 17h 17.1m, Dec= +43° 08´, Constellation = Hercules
- Date/Time: 2011 Apr 12 at 09:46 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: 2 x 300s, f/2.8, ISO 800
- File Name: M92-01w.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.