Event Date: May 20th
Time: 10:00 PM
Brief
Rising in the east-northeast during mid-spring weeks is a dim constellation, with a very attractive telescope target within its boundaries. Hercules, the 'strong man' is made up of stars that require a dark sky to see easily. It contains an asterism which makes up his torso, called the Keystone. It is a quadrilateral with a lopsided-trapezoid appearance, containing three 3rd magnitude stars and one in the high-2 range. Here is a zoom-out of the cluster with the keystone emphasized slightly and labeled. What's that brighter star just east (bottom left) of Hercules? I have mentioned it for several morning and late night entries, and will come back to it tomorrow. If you have followed the sky closely over the last two months of my doing this blog, perhaps you already know however.
Time: 10:00 PM
Brief
Rising in the east-northeast during mid-spring weeks is a dim constellation, with a very attractive telescope target within its boundaries. Hercules, the 'strong man' is made up of stars that require a dark sky to see easily. It contains an asterism which makes up his torso, called the Keystone. It is a quadrilateral with a lopsided-trapezoid appearance, containing three 3rd magnitude stars and one in the high-2 range. Here is a zoom-out of the cluster with the keystone emphasized slightly and labeled. What's that brighter star just east (bottom left) of Hercules? I have mentioned it for several morning and late night entries, and will come back to it tomorrow. If you have followed the sky closely over the last two months of my doing this blog, perhaps you already know however.
Detailed
More importantly, between two of the stars in the keystone is a globular cluster. Even in small telescopes of 4 or 5 inches, a dark sky and the right magnification helps gives this cluster a good appearance. An 8 or 10" scope is recommended, although larger apertures are strongly recommended to see stars near the core more clearly. The field of view used for this second image is a 38 arc-minutes, translating to a magnification of about 80x. Normally I view the cluster with less magnification when this low in the sky, to help contrast, although with my 8" telescope, this works well when it gets high at transit time; that happens during the wee hours of the morning this month.
The final image (yep, 3 today!) have us zoom out again, to show where the cluster is seen within the keystone. That zoom is only about 5 or 6x, which is more binocular-ish. That final showing includes the entire keystone in the field, and the cluster looking more smudge-like. Even that small, which is the way it may also appear in some telescope's finder-scopes, it can be interesting to look at. After all, when Messier (M13 for those keeping track of where this one falls in his catalog), was noticing these non-comet celestial wonders, he may have used telescopes that only magnified it that much!
More importantly, between two of the stars in the keystone is a globular cluster. Even in small telescopes of 4 or 5 inches, a dark sky and the right magnification helps gives this cluster a good appearance. An 8 or 10" scope is recommended, although larger apertures are strongly recommended to see stars near the core more clearly. The field of view used for this second image is a 38 arc-minutes, translating to a magnification of about 80x. Normally I view the cluster with less magnification when this low in the sky, to help contrast, although with my 8" telescope, this works well when it gets high at transit time; that happens during the wee hours of the morning this month.
The final image (yep, 3 today!) have us zoom out again, to show where the cluster is seen within the keystone. That zoom is only about 5 or 6x, which is more binocular-ish. That final showing includes the entire keystone in the field, and the cluster looking more smudge-like. Even that small, which is the way it may also appear in some telescope's finder-scopes, it can be interesting to look at. After all, when Messier (M13 for those keeping track of where this one falls in his catalog), was noticing these non-comet celestial wonders, he may have used telescopes that only magnified it that much!
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| click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp. |
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