The fourth edition of this best-selling field guide was revised and updated, and each printing brings further updates with the latest information. As of the 16th printing (December 2018), most of the time-sensitive material has been updated for the next decade. Twenty-four color Monthly Sky Maps show exactly what you’ll see when facing north or south in the night sky. Fifty-two color Atlas Charts cover the entire sky, including close-ups of areas of special interest, such as the Pleiades and the Orion Nebula. Two dozen pages cover the August 21, 2017, total solar eclipse whose path crossed the continental United States, and other aspects of recent and future solar eclipses.
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"Brimming with dazzling celestial photographs and timely astronomical information, the newly revised Peterson Field Guide to the Stars and Planets is a must-have resource for any amateur stargazer." Country Living Gardener
"An excellent introduction to astronomy for beginners and a field guide for experts." St. Louis Post-Dispatch
The moon is often the most prominent object in the nighttime sky. The moon is somewhat more than one-quarter the diameter of the earth. This makes it the largest substantial satellite (moon) in the solar system in comparison to its parent planet. (Three moons of Jupiter and one each of Neptune and Saturn are physically larger than our moon; Pluto’s small moon Charon is nearly half Pluto’s size.) The moon orbits the earth every 27 1/3 days with respect to the stars. But during that time, the earth and moon have moved as a system about 1/12 of the way in their yearly orbit around the sun. So if the moon at a certain point in its orbit is directly between the earth and the sun, 27 1/3 days later it has not quite returned to that point directly between the earth and the sun. The moon must orbit the earth a bit farther to get back to the same place with respect to the line between the earth and the sun. The moon reaches this point in a couple of days, making the synodic period of the moon equal to 29 1/2 days. (The synodic period is the interval between two successive conjunctions — coming to the same celestial longitude — of two celestial bodies, in this case conjunctions of the moon and sun as observed from the earth.) It is the synodic months that are taken into account in lunar calendars.
