Observing-Challenge-Dec-2008
From OttawaRasc
Ottawa Centre Monthly Observing Challenges
Beginning in 2007, Ottawa Centre introduced a new item to its monthly meetings: an observing challenge object. Each month the centre will post a description of an interesting object. Members are invited to observe, sketch, photograph, or otherwise learn about this object. At the subsequent monthly meeting, an agenda item will provide an opportunity to share your thoughts, photos, sketches, or comments.
December 2008
Lunar: Northern Gateway and Southern Line
By Brian McCullough
| The Lunar Challenge is simple, this month: Get to know two areas of the Moon as well as you know your own neighbourhood. *Rolf Meier*'s stunning image is perfect for our exercise today. |  Image by Rolf Meier |
| The first area is what I call the *Northern Gateway*, the strait allowing passage from the calm expanse of Mare Serenitatis westward into the dark (in this image) Sea of Rains — Mare Imbrium. There is much detail to study in this interesting transition area of the Moon, and I often explore these waters as if I were the captain of a vessel navigating my way from port to port. Make an adventure of it, and it won't take long before the various ports of call become familiar landmarks on your personal chart of the Moon. Change things up once in a while by studying just the mountain ranges, or decide to focus on craters of a certain size or complexity. Each new "game level" will add to your understanding of the lunar story. |  Image by Rolf Meier |
| The second area of interest takes us along the *Southern Line* of the lunar tramway. At First Quarter phase the line of craters dropping south from the middle of the Moon's clock face is framed by the mysterious darkness across the terminator to the west. It is a dramatic sight which becomes increasingly complex the farther south you travel. This "feature rich" highland region is well worth careful examination, but I first recommend you take the scenic tour from the safety and comfort of your tram car. Before heading out with binoculars or telescope, make a quick hand-drawn map of the major features I have marked on Rolf's image and use it to identify the line of "crater subdivisions" — commuter stops along the Southern Line's route. Before you know it, this particular route will become as familiar as the stops on your commute home from work. After that, getting off the tram and exploring any of the stops in detail will be all the more rewarding because you'll know exactly where where you are...the context won't be lost.
Happy Moongazing! |  Image by Rolf Meier |
Deep Sky: A Large Globular Cluster
G1 / Mayall II
by Attilla Danko
| Attilla wanted to select a large globular cluster for the December challenge. His choice, G1, is 650 light-years in diameter, larger than the familiar M13, whose diameter is only 165 light-years. |  Image courtesy Hubblesite.org | ||||||||
| What makes G1 a challenge is that its apparent size in the sky is only 10 arc-seconds. The reason it appears so small is that it is not in our galaxy; this globular cluster is in the halo of the neighbouring Andromeda Galaxy (M31). |  Image from Google Sky. | ||||||||
| To find this object, locate the bright star "32 Andromedae", easy to find because it is part of a triangle of 3 stars. |  Image from Google Sky | ||||||||
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Attilla recommends making up your own set of asterisms, with an amusing story. This makes it easy to remember them so you can star-hop from group to group without having to take your eye away from the eyepiece to consult notes. Attilla illustrated with a story, reading from counter-clockwise from the left:
|  Image from Google Sky | ||||||||
| Inspecting that gap under high power, you find G1 because the watch above was a "Micky Mouse Watch", and stars near G1 give it "Micky Mouse Ears". | 
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Use magnification of about 200X to view G1. Recommended telescopes for visual observation of this challenge object:
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Previous Challenge Objects
- 2008
- 2007
