M9
Globular Cluster in Ophiuchus
About
A globular cluster in southern Ophiuchus, about 25,800 light-years away and roughly 12 billion years old. It lies in front of the dark cloud Barnard 64, which dims some of its light.
Imaging tips
- Only about 9′ across, so it is small: it needs a long focal length, 2,690–4,490 mm on APS-C, and a fine pixel scale.
- Two imagers note that Barnard 64 dims the cluster by roughly a magnitude, so expect an uneven halo.
- Reported totals are modest: 2 h 10 min of LRGB (40/30/30/30 min) from a rural site, and about 2.5 h of 5-minute RGB subs on a 155 mm refractor.
- A wider field (about 2° × 1°20′) also catches part of the dark cloud Barnard 259 at lower left.
- Low: it stays below 22° altitude from 50°N. Best in May and June.
Facts
- Size
- 9′
- Magnitude
- 7.7
- Coordinates
- RA 17h 19.2m, Dec −18° 31′
- Framing, APS-C
- 2690–4490 mm
- Framing, full frame
- longer than 4000 mm
- Best months
- May, Jun
- Peak altitude
- 22° from 50°N, 37° from 35°N