M28
Globular Cluster in Sagittarius
About
A globular cluster in Sagittarius, about 18,300 light-years away, less than a degree from the star Kaus Borealis. It holds the first pulsar found in a globular cluster, PSR B1821−24.
Imaging tips
- About 11′ across: roughly 2,200–3,670 mm on APS-C or 3,380–5,630 mm on full frame.
- One imaging team used a long focal length (about 4,500 mm) and 2 minute subs for 2 h 24 min of LRGB; another got a result from 15 two-minute frames through a light-pollution filter.
- Both sources describe it as smaller and more compact than its neighbour M22, so the core is a tight target even at long focal lengths.
- Low from northern sites: about 15° at most from 50°N. Best around June and July.
Facts
- Size
- 11′
- Magnitude
- 6.8
- Coordinates
- RA 18h 24.5m, Dec −24° 52′
- Framing, APS-C
- 2200–3670 mm
- Framing, full frame
- 3380–5630 mm
- Best months
- Jun, Jul
- Peak altitude
- 15° from 50°N, 30° from 35°N