M91
Galaxy in Coma Berenices
About
A barred spiral galaxy in Coma Berenices, about 63 million light-years away, in the Virgo Cluster. At magnitude 10.2 it is the faintest object in the Messier catalogue, and it went unmatched for nearly two centuries after Messier logged its position against the wrong neighbour; an amateur tied it to NGC 4548 in 1969.
Imaging tips
- Only about 5′ by 4′, too small to frame: use a long focal length and a fine pixel scale.
- Faint for its size at 22.1 mag/arcsec²: one LRGB image used 7 hours (180 min luminance, 80 min each of R, G, B).
- The core and bar are far brighter than the arms, and the imager of the 7 hour image calls getting both to show a processing challenge.
- Best in March and April.
Facts
- Size
- 5′ × 4′
- Magnitude
- 10.2
- Coordinates
- RA 12h 35.5m, Dec +14° 30′
- Framing, APS-C
- longer than 4000 mm
- Framing, full frame
- longer than 4000 mm
- Best months
- Mar, Apr
- Peak altitude
- 55° from 50°N, 70° from 35°N