The Pearl Cluster

Designation:  Caldwell 97, NGC 3766, in Centaurus.
Visual magnitude: +5.3
Apparent size: 9.0 arc-minutes.
Diameter: 18.9 light years.
Distance: 7,200 light years.
Date: 2020-04-17.
Exposure: 10 x 149 sec = 25 min.
Field of view: 76.1 x 51.8 arc-minutes

The Pearl Cluster is another southern celestial masterpiece. Located in the same region as the Eta Carina Nebula and the Running Chicken Nebula, its 7th to 12th magnitude stars stand out from the Milky Way backdrop.

The Night Sky Observers Guide (Vol 3) describes it:

The stars have a chaotic distribution with a mild central compression and many curved star strings and jumbled trains. A nearly detached string stands out at the Southern edge, while two more plunge into the central area”.

South is approximately at “7 o’clock” in this image, which was taken from my suburban home.

The bright star near the top is orange giant HR 4475 (distance: 234 light years); and the bright blue/white star lower left is HR 4487 (distance: 285 light years). They are both 5th magnitude foreground stars, physically unrelated to the Pearl Cluster.

See the Astrometry overlay of my image.

Thanks for reading. I hope you are all safe.

Telescope Details
SkyWatcher Esprit 120 mm apochromatic 3-element refractor.
840 mm focal length @ f/7 with field flattener.
Baader L-Booster UHC-S light pollution filter 2458276.
SkyWatcher EQ6-R Pro mount.
Camera: ZWO ASI 071 MC Pro (CMOS 28.4mm 16 Mpx).
ZWO ASI120 guide camera, using PHD2 software.
2018-03-10 Telescope & Roger
Images © Roger Powell
I’m one of the founding members of Macarthur Astronomical Society,
Australia. 🙃


  1. How beautiful and fascinating too. Safe so far. Not necessarily sane !!!!!!!
    Thanks for posting. Fran


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