Weymouth Astronomy

The Moon

The Moon For a beginner the moon is certainly a good place to start. As it is bright, easily identifiable and our closest celestial neighbour. The full moon may be a wonderful sight to the naked eye but it is the least rewarding when viewing through a telescope as the sun is shining straight down on the surface and casts very little shadow as well as being uncomfortable on the eye (although filters can be used to reduce the glare).

The TerminatorIn general the best time to observe the moon is when it is less than 'half lit'. The line which separates the brightly sunlit portion from the rest of the disk is called the 'Terminator'. Craters and other features along the terminator cast shadows thus increasing contrast.

Moon Facts:

  • The Moon is the second brightest object in the sky after the Sun.
  • The gravitational forces between the Earth and the Moon cause some interesting effects. The most obvious being the tides.
  • The Moon is about 390,000 km (240,000 miles) away from Earth.
  • The same side of the Moon always faces the Earth. (The Moon's rotation period is synchronous with its revolution period around the Earth).
  • Like the rest of the Solar System, the Moon is about 4 1/2 billion years old. Most of the cratering occurred in the first billion years of its life, when leftover debris from planet formation was abundant.
  • The Moon is only one-fourth the diameter of the Earth.