C98
Open Cluster in Crux
About
NGC 4609, a sparse open cluster in Crux that sits behind the Coalsack dark cloud, roughly 4,500 light-years away (other pages say 5,000). It has one red giant and about 33 probable members, including the Be variable BZ Crucis. Dunlop found it in 1826.
Imaging tips
- Compact at roughly 6′ across, so the cluster covers only a small part of a typical frame.
- A wide LRGB frame from a 92 mm f/5.5 refractor held NGC 4609, the smaller cluster Hogg 15 (about 2′) and RCW 69 together.
- The Coalsack in front is only about 600 light-years away.
- Best in March and April, but it never rises from 50°N or 35°N: a southern-hemisphere target.
Facts
- Size
- 12′
- Magnitude
- 6.9
- Coordinates
- RA 12h 42.3m, Dec −63° 0′
- Framing, APS-C
- 2020–3370 mm
- Framing, full frame
- 3090–5160 mm
- Best months
- Mar, Apr
- Peak altitude
- never rises from 50°N, never rises from 35°N