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Image 1: Al Sufi and NGC 6802


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About this observation
Len Adam
Time of observation
28/09/2018 - 21:34
AL Sufi's Cluster and NGC 6802
Observing location
Just outside Albox, Almeria , Spain
Canon 40D + 300mm lens
Paramount MyT
300 seconds

The unguided image was taken with my unmodified Canon 40D (I have one modified 40D and one unmodified 40D). It is a 5 minute exposure using my 300mm lens on the 40D. The image shows the “Coathanger” asterism otherwise known as “Al-Sufi’s Cluster” or Brocchi’s Cluster” . Another designation is “Collinder 399”. The image, which has North at the top,  shows the coathanger upside –down. The star at the eastern end of the straight line of stars in the asterism is HIP 95818, a hot, blue, magnitude 6.34 main sequence star of spectral type B5Vn, whereas the star at the western end of the straight line is  HIP 95291, a cool, orange, magnitude 7.11 subgiant star of spectral type  K3IVp.  The cluster NGC 6802  is just to the east of the coathanger’s straight line of stars. This wide angle image does not show the detail in the central vertical rectangular smudge of stars in NGC 6802.  At the top of the image I have slightly expanded the view of an interesting pair of stars with contrasting colours, reminding me of the much brighter pair in Cygnus (Albireo) although in that case it is the blue star that is 2 magnitudes fainter than its companion (Mags 3 and 5) whereas in this case the blue star is 2 magnitudes brighter. (Mags 7 and 9). The separation of the pair shown in the image is 3 minutes of arc whereas the separation in Albireo is a mere 35 seconds of arc.

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