Saturday, September 8, 2007

Binoculars and the Moon

Next Saturday, September 15, the Moon will be approximately of the shape shown in this picture. Assuming that you happen to have a clear sky that evening, you should be able to view the Moon as described:

If you have access to a pair of binoculars, and, preferably, can support them by some means to hold them steady (a phototripod, perhaps), you can see the craters and the dark areas similar to what's shown here. It's surprising what a pair of binoculars can do. Galileo Galilei (15 February 1564 – 8 January 1642) would have given his eye teeth for optical performance like this when he was alive.

The most prominent of the dark areas is the round area near the upper right of the centre of this picture. It's called "Mare Criseum" - the Sea of Crises - and can be seen with the naked eye. It's an old impact area, of about 400km diameter. The dark material is thought to be ancient lava which erupted from the Moon when a fair-sized asteroid hit it a few billion years ago. From Earth, it looks slightly oval, but this a "perspective" effect. It is actually quite circular.

This picture was taken at the prime focus of a Celestron C-8 telescope (equal to a 2000mm lens at f10) at 1/200sec exposure with a Canon Rebel XT digital SLR camera.

Here's a closer view of Mare Criseum.