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M13 globular cluster in Hercules


 2011 Oct 18

I had previously only photographed this from a light-polluted suburban site.

Canon EOS 5D MkII ISO6400 45x30s 254mm Newtonian (2x Barlow, f=2400mm) f/9.6 2011 Oct 18 20:13:27-20:41:30 UT
From Rookhope 54.8N 2.1W 330m asl. Rural, almost no light pollution (3 Bortles)

 2009 Aug 15

M13 in Hercules

Canon EOS5DMkII 254mm Newtonian @ 2380mm 39 x 10s f/9.4 ISO25600 2009:8:15 22:28:29-22:36:45
From Whitley Bay 55.1N 1.5W 10m asl. Suburban, significant light pollution (6.5 Bortles)

Item 13 in Charles Messier's 18th century catalogue of faint fuzzy objects in the sky turned out, in the light of later observations with better instruments, to be a gravitationally bound cluster of around 1 million stars. I had seen many photographs of it in books but my first look at it by eye through the new telescope was a revelation. Due to our atmosphere it twinkles in a most fascinating way. No photograph can possibly show this because photography has to integrate the faint light over an appreciable time (minutes). The eye can catch rapid subtle changes, so the real thing is far more beautiful than the photographs suggest.

Distance: 26,000 light years.

Globular clusters are outside our galaxy (the Milky Way) but bound by gravity to orbit around it. Their distances from us are not very accurately known because they contain few if any of the kinds of stars that are usually used for determining extra-galactic distances. They are generally billions of years old.

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