to 90°; at Last Quarter it is 180°, and at the New Moon the colongitude reaches 270°. Note that the Moon is nearly invisible from the Earth at New Moon phase except during a solar eclipse. The low angle of incidence of arriving sunlight tends to pick out features by the sharp shadows they cast, thus the area near the terminator is usually the most favorable for viewing or photographing lunar features through a telescope. The observer will need to know the location of the terminator to plan observations of selected features. The selenographic colongitude is useful for this purpose. The selenographic longitude of the evening terminator is equal to the colongitude plus 180°. See also Planetary coordinate system Selenoid References "A Unified Lunar Control Network — The Near Side", Merton E. Davies, Tim R. Colvin, & Donald L. Mayer, RAND Corporation, Santa Monica, 1987. Lunar science Angle Coordinate systems