Observing the Full Moon
Answer: the nights around the time of full Moon. After all, bright moonlight washes out faint galaxies and nebulae, and the Moon itself is too glaring to be observed . . . right?
If you heard yourself say this, it’s time to take your telescope outside during the next full Moon and begin exploring a world largely overlooked by amateur astronomers. There are numerous fascinating features to observe during this or any phase when you aim your telescope far from the terminator (the dividing line between lunar day and night). The Moon is very bright when it’s full. If your magnified view of the lunar surface is a bit too dazzling for comfortable observing, use a Moon filter to cut the brilliance without eliminating detail.
Because there are no shadows at full Moon, the dark and light areas you see are variations in the albedo (reflectivity) of different parts of the Moon. The biggest albedo difference is between the dark maria (the lunar “seas”) and the light highlands. This is due to the compositions of the two surfaces. The maria are made of basaltic lava flows, much like those in Hawaii and Iceland. They contain iron, titanium and other dark metals. The highlands of the Moon are dominated by a bright, aluminum-rich rock called anorthosite. When you observe these light and dark regions, you’re seeing rocks that resulted from fundamentally different processes of formation.