[TrevorW]

Target: NGC 6231 open cluster
Camera: QHY 8 OSC uv/ir nose piece
Exposure Capture: Maxim
Scope: GSO 8” RC
Mount: EQ6 Pro
Exposure Setting: Gain 3 offset 109
Exposures: 6 x 360s total 36m taken 16-17 /04/09 best of 17 frames 11 dumped due to dewing
Seeing: good, heavy dew
Guiding: Orion Starshoot Autoguider using PHD
Focus: Maxim, and mask
Stacking: DSS 3darks, 10flats, 10 bias frames
Processing: PS CS3, Maxim DL

Right Ascension 16 : 54.0 (h:m)
Declination -41 : 48 (deg:m)
Distance 5.9 (kly)
Visual Brightness 2.6 (mag)
Apparent Dimension 15 (arc min)


Info: Situated in the Scorpius


NGC 6231 is an open cluster located near Zeta Scorpii. Zeta 1 (HR 6262) is a member of this star cluster. (Its brighter apparent partner, Zeta 2 (HR 6271), is only 150 ly from Earth and so is not a cluster member.)


This cluster is estimated about 3.2 million years old, and is approaching the Solar System at 22 km/s. Very young stars including it, belong to the Scorpius OB association. Zeta1 Scorpii (spectral type O8 and magnitude 4.71.) is the hottest star in it.
It was discovered by Giovanni Batista Hodierna before 1654. Hodierna listed it as Luminosae in his catalogue of deep sky observations. This catalogue was included in his book De Admirandis Coeli Characteribuse published in 1654 at Palermo. It was independently observed by other astronomers after Hodierna