This large globular cluster was discovered Halley in 1714, who already noted that it was visible with the naked eye, “in serene and Moonless nights”. This is a relatively nearby globular cluster, 22,200 light years, and quite old (about 11.5 billion years). As most globulars, it contains very old stars as well as 15 blue stragglers, old stars that appear bluer and younger than their neighbors. One unusual feature is the presence of Barnard 29, a B2-type star, that was most probably “captured” by the cluster as it was passing by. This star, physically has totally different properties compared with its “cluster-mates”. It is calculated that about 300,000 stars populate this cluster.
Name(s): M 13. NGC 6205. Great Hercules Cluster.
Type: Globular Cluster
RA: 16h 41m 41s
Dec: +36º 27’ 43”
Size (arcmin): 20×20
Distance: 22,200 ly
Location: Corbera de Llobregat, Barcelona, Catalonia
Size (arcmin): 24×18
Telescope: Celestron 11” HD f/10
Camera: FLI ML6303 (3072x2048pix)
Guiding: Orion SSAG/Nikkor 500mm f/8
Total exposure: 25.5 min (L: 6 min; RGB 19.5 min)
Processing: CCDStack, Photoshop CC 2016 and PixInsight