M24 - Sagittarius Star Cloud
Messier 24 or M24 (also designated IC 4715) is a Milky Way star cloud in the constellation Sagittarius. It has an apparent visual magnitude of 4.6 and its angular diameter is 90 arc-minutes. M24 lies at an estimated distance of 10,000 light years. The Equinox 2000 coordinates are RA= 18h 16.9m, Dec= -18° 30´ which makes M24 best seen during the summer. The Messier Summer Star Chart shows the position of all Messier objects visible during that season. As one of the more famous objects in the Messier Catalog, it is commonly known as the Sagittarius Star Cloud.
The image above shows the uncropped view of M24 through the Takahashi E-180 Astrograph (North is up). A 2x enlargement of this image appears to the right.
This Milky Way star cloud was discovered by Messier in 1764. It is unusual in that it does not consist of a single physical object. Rather, it is the juxtaposition of several bright clumps of interstellar dust and gas in the Milky Way along the line of sight. According to Stoyan et al. (2010), the distance of M24 ranges from 12,000 to 16,000 light years.
Messier's Description of M24
June 20, 1764
`Cluster on the parallel of the preceding [M23] and near the end of the bow of Sagittarius, in the Milky Way: a large nebulosity in which there are many stars of different magnitudes: the light which is spread throughout this cluster is divided into several parts; it is the center of this cluster which has been determined [position].' (diam. 1d 30')
- Object: M24
- Other Names: IC 4715, Sagittarius Star Cloud
- Object Type: Milky Way star cloud
- Object Data: Apparent Magnitude = 4.6, Angular Size = 90 arc-minutes
- Object Position (Equinox 2000): RA= 18h 16.9m, Dec= -18° 30´, Constellation = Sagittarius
- Date/Time: 2011 May 06 at 09:54 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: M24-01w.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.