Messier 71 or M71 (also designated NGC 6838) is a globular cluster in the constellation Sagitta. It has an apparent visual magnitude of 8.2 and its angular diameter is 7.2 arc-minutes. M71 lies at an estimated distance of 12,700 light years. The Equinox 2000 coordinates are RA= 19h 53.8m, Dec= +18° 47´ which makes M71 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 M71 through the Takahashi E-180 Astrograph (North is to right). A 3x enlargement of this image appears to the right.
This very loose globular cluster was discovered by J-P. de Chéseaux in 1746. According to Recio-Blanco et al.(2005), the distance of M71 is 18,330 light years and its diameter is 40 light years. Its estimated mass is 40,000 solar masses and it contains 23 variable stars.
Messier's Description of M71
October 4, 1780
`Nebula discovered by M. Méchain on June 28, 1780, between the stars Gamma and Delta Sagittae. On October 4 following, M. Messier looked for it: its light is very faint and it contains no star; the least light makes it disappear. It is situated about 4 degrees below [south of] that which M. Messier discovered in Vulpecula. See No. 27. He reported it on the Chart of the Comet of 1779.' (diam 3.5')
- Object: M71
- Other Names: NGC 6838
- Object Type: globular cluster
- Object Data: Apparent Magnitude = 8.2, Angular Size = 7.2 arc-minutes
- Object Position (Equinox 2000): RA= 19h 53.8m, Dec= +18° 47´, Constellation = Sagitta
- Date/Time: 2011 Aug 02 at 07:59 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: M71-01w.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.