An open cluster in Carina
|Magnitude: +3.8||Diameter: 11.6 light years.|
|Apparent size: 30 arc min||Distance: 1,300 light years.|
The stars of Caldwell 96 form a beautiful open cluster, which I imaged a few weeks ago in the Southern constellation of Carina. Burnham’s Celestial Handbook describes it as: “a large and brilliant group, easily visible to the naked eye, with more than a hundred stars scattered over a field 1° in diameter”.
It has a combined magnitude of 3.8, making it readily visible as a smudge in a dark sky – and a fine binocular object.
The brightest star (HD 66342) is a magnitude 5.2 class M red giant with a diameter of over 100 times that of the Sun. Two other similar (orange coloured) stars complete a neat triangle with a background sprinkling of 8th and 9th magnitude stars.
Open clusters are formed by the birth of new stars in collapsing molecular clouds found in the plane of the galaxy and thus all the stars are approximately the same age, which in this cluster is estimated at around 140 million years.
|Feature image date:||2021-03-25|
|Exposure:||21 minutes (6 x 216 sec)|
|Field of View:||1.59° x 1.06° (up is 51.3° E of N)|
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Telescope & Imaging Details
|SkyWatcher Esprit 120 mm apochromatic 3-element refractor; 840 mm f/l @ f/7.|
|Field flattener; ZWO Duo-band Hα (656nm) and [OIII] (500nm) filter.|
|SkyWatcher EQ6-R Pro mount; ZWO ASI120 guide camera.|
|Imaging camera: ZWO ASI 071 MC Pro (CMOS 28.4mm 16 Mpx).|
|Software: Telescope control: Cartes du Ciel, EQMOD, PHD2, Imaging: SharpCap, Gimp.|
|Observatory location: 34° South.|
Thanks for reading!
Images © Roger Powell
I’m one of the founder members of Macarthur Astronomical Society and current webmaster.