Arp1
Galaxy in Ursa Major
About
NGC 2857, a spiral galaxy in Ursa Major about 225 million light-years away and roughly 125,000 light-years across. It opens Arp's Atlas of Peculiar Galaxies as the first of six spirals he grouped as low surface brightness galaxies. A Type II-P supernova, SN 2012fg, appeared in it in October 2012.
Imaging tips
- At about 2′ × 1′ it is too small to frame: use a long focal length and a fine pixel scale.
- Surface brightness is 22.4 mag/arcsec², faint for its size, so plan several hours of broadband data; a galaxy gains nothing from narrowband filters.
- One imager worked with a Newtonian, an SBIG ST-2000XM camera and a 1.136 arcsec/pixel scale, framing a 45.5′ field around the galaxy.
- That imager stacked 28 luminance frames of 12 minutes (5 h 36 min) with RGB at 11 frames of 8 minutes per colour, 10 hours in all.
- Best around January and February, when it climbs to nearly 89° altitude from 50°N.
Facts
- Size
- 2′ × 1′
- Magnitude
- 13.0
- Coordinates
- RA 9h 24.6m, Dec +49° 21′
- Framing, APS-C
- longer than 4000 mm
- Framing, full frame
- longer than 4000 mm
- Best months
- Jan, Feb
- Peak altitude
- 89° from 50°N, 76° from 35°N