C97
Open Cluster in Centaurus
About
Open cluster NGC 3766 in Centaurus, set in the Carina star-forming cloud and about 5,700 to 6,700 light-years away depending on the measurement. Lacaille logged it in the 1750s. It holds 11 Be stars and two red supergiants, and dozens of its fast-spinning B stars flicker by tiny fractions of a magnitude.
Imaging tips
- At magnitude 5.3 and 19.8 mag/arcsec² it is bright for a cluster; an urban-backyard LRGB image through an 8-inch SCT at about f/6 shows it clearly.
- A dense star cluster suits broadband; one imager used luminance plus RGB.
- Sources give about 12′ across, so a long focal length fills the frame; check your own field against that size before choosing.
- Best February to April, but it never rises from 50°N or 35°N: a southern-hemisphere target.
Facts
- Size
- 15′
- Magnitude
- 5.3
- Coordinates
- RA 11h 36.2m, Dec −61° 37′
- Framing, APS-C
- 1620–2690 mm
- Framing, full frame
- 2480–4130 mm
- Best months
- Feb, Mar, Apr
- Peak altitude
- never rises from 50°N, never rises from 35°N