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The Butterfly Cluster contains about 80 stars distributed unevenly across a 50 arcmin area. Its brightest stars occupy, however, a smaller 20-25 arcmin area. It is seen against a rich starry background in Scorpius (angularly close to the galactic center). Its brightest star, BM Sco, mag +6.0 is a variable red star (5.5-7.0). Most stars are blue (type B4-B5).
Additional Information
Object
Name(s): M6, NGC 6405, The Butterfly Cluster
Type: Open Cluster
RA: 17h 40m 19s
Dec: -32º 14’ 54”
Constellation: Scorpius
Size (arcmin): 25×25
Magnitude: +4.2
Distance: 1,600
Image
Date: 2013-07-29
Location: Corbera de Llobregat, Barcelona, Catalonia
Size (arcmin): 37×27
Telescope: Celestron 11″ HD f/10
Camera: FLI ML6303 (3072x2048pix)
Guiding: Orion SSAG/Nikkor 500mm f/8
Total exposure: 13 min (L: 3 min; RGB: 10min)
Processing: PixInsight