Messier 91 or M91 (also designated NGC 4548) is a barred spiral galaxy in the constellation Coma Berenices. It has an apparent visual magnitude of 10.2 and its angular diameter is 5.4x4.4 arc-minutes. M91 lies at an estimated distance of 60 million light years. The Equinox 2000 coordinates are RA= 12h 35.5m, Dec= +14° 30´ which makes M91 best seen during the spring. The Messier Spring Star Chart shows the position of all Messier objects visible during that season.
According to Stoyan et al. (2010), the distance of M91 is 52.9 million light years and its diameter is 83,000 light years.
Messier's Description of M91
March 18, 1781
`Nebula without star, in Virgo, above the preceding No. 90: its light is still fainter than that of the above.'
- Object: M91
- Other Names: NGC 4548
- Object Type: barred spiral galaxy
- Object Data: Apparent Magnitude = 10.2, Angular Size = 5.4x4.4 arc-minutes
- Object Position (Equinox 2000): RA= 12h 35.5m, Dec= +14° 30´, Constellation = Coma Berenices
- Date/Time: 2011 Apr 23 at 05:22 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: M88M91-01w.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.