Messier 25 or M25 (also designated IC 4725) is a open cluster in the constellation Sagittarius. It has an apparent visual magnitude of 4.6 and its angular diameter is 32 arc-minutes. M25 lies at an estimated distance of 2000 light years. The Equinox 2000 coordinates are RA= 18h 31.6m, Dec= -19° 15&acu which makes M25 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 M25 through the Takahashi E-180 Astrograph (North is up). A 2x enlargement of this image appears to the right.
Messier's Description of M25
June 20, 1764
`A cluster of small stars in the neighborhood of the two previous clusters [M23 and M24], between the head and the end of the bow of Sagittarius: the nearest known star to this cluster is 21 Sagittarii, 6th magnitude, according to Flamsteed. The stars of this cluster are seen with difficulty with an simple refractor of 3.5 feet; no nebulosity can be seen. Its position has been determined from Mu Sagittarii.' (diam. 10')
- Object: M25
- Other Names: IC 4725
- Object Type: open cluster
- Object Data: Apparent Magnitude = 4.6, Angular Size = 32 arc-minutes
- Object Position (Equinox 2000): RA= 18h 31.6m, Dec= -19° 15&acu, Constellation = Sagittarius
- Date/Time: 2011 May 06 at 09:29 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: M25-01w.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.