[TrevorW]

Target: M4755 Kappa Crucis, Jewel Box
Camera: Canon 350d modified, Baader 2” Skyglow filter
Exposure Capture: DLSR Focus
Scope: GSO CF RC200
EFR: f/8
Mount: EQ6 Pro
Exposure Setting: Prime focus, ISO800 ICNR off Daylight WB
Exposures: 11x180s, 3/8/09 between 7:00 and 8:30pm
Seeing: waxing gibbous 95% moon
Guiding: Orion Starshoot Autoguider using PHD with ED80
Focus: DSLR Focus
Stacking: DSS 10 darks plus flats, no bias applied
Processing: CS3

Right Ascension 12 : 53.6 (h:m)
Declination -60 : 20 (deg:m)
Distance 7.6 (kly)
Visual Brightness 4.2 (mag)
Apparent Dimension 10 (arc min)


Discovered by Lacaille in 1751-52.
This cluster was one of the finest open clusters discovered by Abbe Lacaille when he was in South Africa during 1751-1752.
This cluster is one of the youngest known, with an estimated age of only 7.1 million years (Sky Catalog 2000). Its hottest star is of spectral type B0. According to Burnham, the 3 brightest stars are blue giants of mag 5.75 and spectral type B9, mag 5.94 and type B3, and mag 6.80/B2, while the fourth brightest star is a mag 7.58 M2 red supergiant. Another mag 5.7/spectral type A1 star is probably also a member, another white supergiant: This star would be the brioghtest of the cluster at about absolute magnitude -7.7 (83,000 solar luminosities).
Situated close to the cluster is a huge dark area of the sky, right within the band of the Milky Way: the Coal Sack. This is a huge dark nebula, probably the nearest at 500 to 600 light years distance, and 60 to 70 light years diameter.