Arp155
Galaxy in Ursa Major
About
NGC 3656, a peculiar galaxy in Ursa Major about 135 million light-years away, left by the merger of two disk galaxies. Arp listed it among disturbed galaxies with interior absorption. A dark lane crosses it, and shells and two faint tails surround it.
Imaging tips
- Only about 1.6′ across in the sources, so it is too small to frame: use a long focal length and a fine pixel scale.
- Moderately faint at 21.9 mag/arcsec², so plan broadband data; its shells and tails are faint extras that deep data may show.
- One imager first took reddish star-like dots around it for orbiting dwarfs, then concluded they are distant background galaxies reddened by distance.
- One imager's run lasted through a night with a temperature drop of nearly 20 °C, so image scale shifted and frames needed resizing before stacking.
- Best around February and March; it passes about 86° altitude from 50°N.
Facts
- Size
- 1.6′ × 1.6′
- Magnitude
- 12.3
- Coordinates
- RA 11h 23.6m, Dec +53° 51′
- Framing, APS-C
- longer than 4000 mm
- Framing, full frame
- longer than 4000 mm
- Best months
- Feb, Mar
- Peak altitude
- 86° from 50°N, 71° from 35°N