M12, in the constellation of Ophiuchus, was discovered by Charles Messier on 30 May 1764. It is 15,700 light-years away and is about 75 light-years in diameter. It has an integrated magnitude of 6.6 which is too dim to be visible to most people's naked eyes, but it may be glimpsed in binoculars in a dark sky.
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M12 captured with my LX200 fitted with a 0.33 focal reducer (focal length 800 mm). The diameter of the cluster is about 14 minutes of arc. The brightest stars are about magnitude 12 although the cluster as a whole has a magnitude of 6.6 putting it on the verge of naked-eye visibility in a totally dark sky. Where I live (latitude 52° N) there is no true darkness at this time of the year, but M12 is bright enough to show through and I took the pictures soon after midnight. As always I used a CLS filter to remove the worst of the artificial-light pollution. Date and Time: 28th May 2012 00:10 to 00:22 UT Camera: Starlight Xpress MX716 Telescope: LX200 with 0.33 focal reducer and Astronomik CLS filter Capture: star_mx7. 10 frames 60 seconds exposure Processing: star_mx7. Dark frame subtracted, enhanced factor 25, black level. Registax 5. All frames stacked, Gaussian wavelets Scheme 2. Focus Magic motion 5,2, blur 1,100. |
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