M103
Open Cluster in Cassiopeia
About
An open cluster in Cassiopeia, about 9,400 light-years away and roughly 15 light-years across, with about 170 estimated members. Its age is put at 12.6 to 25 million years. A red giant of about magnitude 10.8 sits near its centre, and it was the last deep-sky object added to Messier's catalogue.
Imaging tips
- About 6′ across, so it is too small to frame: use a long focal length and a fine pixel scale.
- The bright star Ruchbah lies close by; one imager framed too near it and got a colourful flare artifact across a corner.
- Sparse and bright: one LRGB set of 30 s subs totalling only 35 minutes was workable, and a DSLR set of about 70 minutes also worked.
- A star cluster has no nebulosity, so broadband is the right choice. Best around September to November.
Facts
- Size
- 6′
- Magnitude
- 7.4
- Coordinates
- RA 1h 33.4m, Dec +60° 39′
- Framing, APS-C
- longer than 4000 mm
- Framing, full frame
- longer than 4000 mm
- Best months
- Sep, Oct, Nov
- Peak altitude
- 79° from 50°N, 64° from 35°N