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Uploaded 10-Jun-11
Taken 8-Jun-11
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7 of 74 photos
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Categories & Keywords

Category:Scenic
Subcategory:Night Sky
Subcategory Detail:
Keywords:M7
Photo Info

Dimensions3600 x 2400
Original file size11 MB
Image typeJPEG
Color spaceUncalibrated
Date taken8-Jun-11 18:29
Date modified10-Jun-11 18:30
Shooting Conditions

Camera makeCanon
Camera model40D Modified
ISO speedISO 1600
Messier 7 The Ptolemy Cluster

Messier 7 The Ptolemy Cluster

About this Object:
Messier 7 or M7, also designated NGC 6475 and sometimes known as the Ptolemy Cluster, is an open cluster of stars in the constellation of Scorpius.

The cluster is easily detectable with the naked eye, close to the "stinger" of Scorpius. It has been known since antiquity; it was first recorded by the 1st-century astronomer Ptolemy, who described it as a nebula in 130 AD. Giovanni Batista Hodierna observed it before 1654 and counted 30 stars in it. Charles Messier catalogued the cluster in 1764 and subsequently included it in his list of comet-like objects as 'M7'.

Telescopic observations of the cluster reveal about 80 stars within a field of view of 1.3° across. At the cluster's estimated distance of 800–1000 light years this corresponds to an actual diameter of 18–25 light years. The age of the cluster is around 220 million years while the brightest star is of magnitude 5.6.


About this Photo:
Date(s): June 8, 2011
Location: From my driveway in Georgetown, Texas
Telescope: Celestron C9.25 @ F6.5
Mount: CGEM
Guiding: Orion StarShoot AutoGuider / Taurus Tracker III
Camera: Canon 40D Modified
Filter: Astronomik CLS
Exposure: 5x120s @ ISO1600 (10 Minutes total)
Acquisition: ImagesPlus 3.75 Camera Control
Processing: ImagesPlus 3.75 – Darks,Flats,Bias
Post-processing: Adobe Photoshop CS3; Noel Carboni's Tools;
Temperature(s): 75º F