It has been already two years since I imaged M3 last time. I made this image now just to check how new telescope behaves on such target type. Picture was made with Meade ACF 10″ telescope with AP CCDT67 telecompressor and QHY163M camera. All set on EQ6 mount. Subframes exposure time was 1 minute each, and there is about one hundred of subframes here made with LRGB filters.
M3 itself is one of the largest and brightest star clusters – it is made up of around half million stars. Cluster is estimated to be 8 billion years old, it was already half its current age, when our Sun was born. M3 was discovered by Charles Messier, and he recorded it in his notes:
“On May 3, 1764, when working on a catalog of the nebulae, I have discovered one between Bootes and one of the Hunting Dogs [Canes Venatici] of Hevelius, the southernmore of the two, exactly between the tail and the paws of this Dog, according to the charts of Flamsteed. I have observed that nebula on the meridian, and I compared with Mu Bootis; its right ascension has been found as 202d 51′ 19″, and its declination as 29d 32′ 57″ north. That nebula which I have examined with a Gregorian telescope of 30 pouces focal length, which magnifies 104 times, doesn’t contain any star; the center is brilliant, and the light gets lost fading [outward]; it is round, and could have 3 minutes of arc in diameter. One can see it in a good sky with an ordinary [nonachromatic] refractor of one foot [FL] , it doesn’t contain any star, its center is brilliant, and its light is gradually fading away, it is round; in a beautiful [dark] sky.”