The best time to observe the moon with a telescope is the interval when the moon is at or just past first quarter phase, or at or just before last quarter phase. This is the time when we get the best views of the lunar landscape right along the sunrise-sunset line, or terminator. (The terminator can also be defined as that variable line between the illuminated portion and the part of the moon in shadow.) Along with the fact that a half moon offers more viewing comfort to the eye than a full moon does, using a telescope with just small optical power (magnifications of 20- to 40-power) or even good binoculars allows us to see a wealth of detail on the surface. Around those times when the moon is half-lit or in its gibbous phase, those features lying close to the terminator stand out in sharp, clear relief.  The moon next arrives at first quarter phase today at 8:21 p.m. EST. That will be the moment when its disk is exactly 50 percent illuminated. Lunar mountains will be visible as the sun lights them from the right.

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