ASE-1 Lunar seas and ray craters
The Lunar Maria – or seas – are the large, dark, smooth areas formed by lava from ancient volcanic eruptions.
The major ray craters are also visible around full Moon time. Craters Tycho and Copernicus have the most complex and far-reaching systems of rays but there are other less-prominent ones such as Kepler.
Spot as many seas as you can and identify them using the chart. Identify the main ray craters and see if you can find any others.
OBSERVE: They are visible at most phases of the Moon but all are more clearly visible for a few days either side of full Moon.
Mare Tranquilitatis, the Sea of Tranquility, is where Neil Armstrong and Buzz Aldrin landed in the Apollo 11 mission in 1969.
ASE-2 Copernicus and Plato
These are two of the most interesting craters on the Moon. Copernicus is a large ray crater, 97 km wide, with several central peaks. It stands by itself just south of Mare Imbrium. The walls of the crater can appear bright white, casting long, dark shadows onto the crater floor at various lunar phases.
Plato is an impact crater, filled with lava, 109 km across at its widest point. It has a collapsed wall on the west side leading to interesting light and shadows at different illuminations.
Try and observe them at different phases and watch how the appearance changes with varying illumination. Although the floor of Plato looks smooth, there are actually several small craterlets in it. These are a real challenge to see.
OBSERVE: Copernicus is visible from about 2 days after first quarter phase (half Moon). At full Moon (lunar midday) the rays become more obvious. When the crater is on the terminator between light and dark (lunar dawn) the shadows become well-defined.
Plato is visible from 1 day after first quarter.