2016 Oct. 4 ~ M22 & M13, two bright globular star clusters
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Photographed at Algonquin Provincial Park, Ontario, Canada
(285 km by road north of Toronto)
* Altitude of M22 at time of exposures: 15°, decreasing to 14°
* Altitude of M13 at time of exposures: 37°, decreasing to 34°
Temperature 13° C.
* Total exposure time: 6 minutes for M22
* Total exposure time: 7 minutes for M13
* 1200 mm focal length telescope
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Description:
These are two of the largest and brightest globular star clusters visible from the northern hemisphere. M22 in the constellation Sagittarius is brighter and larger than M13 in Hercules, at least as seen from our solar system (it is actually smaller than M13, but M13 is almost 2.5 times as far away from us and has four times as many stars as M22). But because M22 is so far south in the sky, and is in an area that is strewn with other magnificent clusters and bright nebulae, it does not receive nearly the attention that the more northerly, but smaller and fainter, M13 does.
Globular star clusters are dense mainly spherical agglomerations of stars that are gravitationally bound together. They are found in the halos of the galaxies in which they are located, and are among the most ancient structures in the 13.8-billion-year-old universe.
In this view these two star clusters are shown to exactly the same scale. The subframes comprising each of the final images were made on the same evening, within an hour of each other.
Because M22 was extremely low in the sky when I captured the exposures that make up this image, atmospheric turbulence made the stars images move around a lot and turned the stars into small blobs rather than the more pinpoint star images in M13, which was much higher is the sky.
About M22, from Wikipedia:
"Messier 22 ... is an elliptical globular cluster in the constellation Sagittarius, near the Galactic bulge region. It is one of the brightest globulars that is visible in the night sky.
M22 was one of the first globulars to be discovered, on August 26, 1665 by Abraham Ihle and it was included in Charles Messier's catalog of comet-like objects on June 5, 1764. It was one of the first globular clusters to be carefully studied first by Harlow Shapley in 1930. He discovered roughly 70,000 stars and found it had a dense core.
M22 is one of the nearer globular clusters to Earth at a distance of about 10,600 light-years away. It spans ... 99 ± 9 light-years [in diameter]. 32 variable stars have been recorded in M22.
Despite its relative proximity to us, this metal-poor cluster's light is limited by dust extinction, giving it an apparent magnitude of 5.5 making it the brightest globular cluster visible from mid-northern latitudes ... However, due to its southerly declination, M22 never rises high in the sky and so appears less impressive to northern hemisphere observers than other summer sky globulars such as M13 and M5.."
About M13, from Wikipedia:
Messier 13 ..., sometimes called the Great Globular Cluster in Hercules ..., is a globular cluster of about 300,000 stars in the constellation of Hercules. ... M13 was discovered by Edmond Halley in 1714, and catalogued by Charles Messier on June 1, 1764.
M13 is about 145 light-years in diameter, and ... is 25,100 light-years away from Earth.
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Nikon D810a camera body on Explore Scientific 152 mm (6") apochromatic refracting telescope, mounted on Astrophysics 1100GTO equatorial mount with a Kirk Enterprises ball head
Multiple stacked subframes; each frame:
ISO 3200 for M22, and ISO 2500 for M13; 1 minute exposure at f/8
(with LENR - long exposure noise reduction)
Subframes stacked in RegiStar;
Processed in Photoshop CS6 (brightness, contrast, levels, colour balance, sharpening)
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2016 Oct. 4 ~ M22 & M13, two bright globular star clusters
******************************************************************************
Photographed at Algonquin Provincial Park, Ontario, Canada
(285 km by road north of Toronto)
* Altitude of M22 at time of exposures: 15°, decreasing to 14°
* Altitude of M13 at time of exposures: 37°, decreasing to 34°
Temperature 13° C.
* Total exposure time: 6 minutes for M22
* Total exposure time: 7 minutes for M13
* 1200 mm focal length telescope
___________________________________________
Description:
These are two of the largest and brightest globular star clusters visible from the northern hemisphere. M22 in the constellation Sagittarius is brighter and larger than M13 in Hercules, at least as seen from our solar system (it is actually smaller than M13, but M13 is almost 2.5 times as far away from us and has four times as many stars as M22). But because M22 is so far south in the sky, and is in an area that is strewn with other magnificent clusters and bright nebulae, it does not receive nearly the attention that the more northerly, but smaller and fainter, M13 does.
Globular star clusters are dense mainly spherical agglomerations of stars that are gravitationally bound together. They are found in the halos of the galaxies in which they are located, and are among the most ancient structures in the 13.8-billion-year-old universe.
In this view these two star clusters are shown to exactly the same scale. The subframes comprising each of the final images were made on the same evening, within an hour of each other.
Because M22 was extremely low in the sky when I captured the exposures that make up this image, atmospheric turbulence made the stars images move around a lot and turned the stars into small blobs rather than the more pinpoint star images in M13, which was much higher is the sky.
About M22, from Wikipedia:
"Messier 22 ... is an elliptical globular cluster in the constellation Sagittarius, near the Galactic bulge region. It is one of the brightest globulars that is visible in the night sky.
M22 was one of the first globulars to be discovered, on August 26, 1665 by Abraham Ihle and it was included in Charles Messier's catalog of comet-like objects on June 5, 1764. It was one of the first globular clusters to be carefully studied first by Harlow Shapley in 1930. He discovered roughly 70,000 stars and found it had a dense core.
M22 is one of the nearer globular clusters to Earth at a distance of about 10,600 light-years away. It spans ... 99 ± 9 light-years [in diameter]. 32 variable stars have been recorded in M22.
Despite its relative proximity to us, this metal-poor cluster's light is limited by dust extinction, giving it an apparent magnitude of 5.5 making it the brightest globular cluster visible from mid-northern latitudes ... However, due to its southerly declination, M22 never rises high in the sky and so appears less impressive to northern hemisphere observers than other summer sky globulars such as M13 and M5.."
About M13, from Wikipedia:
Messier 13 ..., sometimes called the Great Globular Cluster in Hercules ..., is a globular cluster of about 300,000 stars in the constellation of Hercules. ... M13 was discovered by Edmond Halley in 1714, and catalogued by Charles Messier on June 1, 1764.
M13 is about 145 light-years in diameter, and ... is 25,100 light-years away from Earth.
__________________________________________
Nikon D810a camera body on Explore Scientific 152 mm (6") apochromatic refracting telescope, mounted on Astrophysics 1100GTO equatorial mount with a Kirk Enterprises ball head
Multiple stacked subframes; each frame:
ISO 3200 for M22, and ISO 2500 for M13; 1 minute exposure at f/8
(with LENR - long exposure noise reduction)
Subframes stacked in RegiStar;
Processed in Photoshop CS6 (brightness, contrast, levels, colour balance, sharpening)
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