C86
Globular Cluster in Ara
About
NGC 6397, a globular cluster in Ara about 7,800 light-years away, among the closest two to Earth together with Messier 4. It holds roughly 400,000 stars, and its core has collapsed into a very dense knot.
Imaging tips
- Sources put its width near 32′, so 760–1,260 mm on APS-C fills a third to half of the frame with the cluster; a shorter lens leaves more room.
- A frame about 57′ × 43′ at 1.03″ per pixel, shot on a 12-inch f/3.6 astrograph, fitted the whole cluster with room to spare.
- That image used only 5 × 1 min each of R, G and B, so modest integration is enough to show the cluster.
- Best in June, but it never rises from 50°N and peaks near 1° from 35°N.
Facts
- Size
- 32′
- Magnitude
- 5.7
- Coordinates
- RA 17h 40.7m, Dec −53° 40′
- Framing, APS-C
- 760–1260 mm
- Framing, full frame
- 1160–1930 mm
- Best months
- Jun
- Peak altitude
- never rises from 50°N, 1° from 35°N