How do I locate stars and planets in the night sky?
For the casual observer, locating stars, planets, and other astronomical objects in the night sky is most easily accomplished with the help of a star map. Many good books are available containing extensive maps of star positions for the entire sky, while magazines such as StarDate, Astronomy, and Sky & Telescope provide monthly maps that show the locations of the planets.
More careful observations require an understanding of the scales astronomers use to measure positions on the "surface" of the night sky. There are two primary coordinate systems used by astronomers; the first method employs a grid of right ascension and declination on the celestial sphere in the same manner that longitude and latitude are used on Earth's spherical surface.
A more intuitive system describes positions by their altitude in degrees above the local horizon and compass heading in degrees from 0 to 360, called azimuth. The flaw of this system is that the coordinates depend entirely on the location of the observer, and furthermore each object's position changes throughout the night as Earth turns in towards the dawn. The simplicity of this system, however, underlies its appeal and common usage; most "stargazing tips" and calendars refer observers to positions on their local horizon and how high above the horizon to look -- the altitude-azimuth system hard at work.
A helpful tool for using either of these two methods of finding your way around is found conveniently at the end of your arm. By extending your hand at arm's length, you can approximate a many degree measurements: The apparent width of one finger at arm's length, for instance, is about one degree, and a fist covers about 10 degrees.
So with a star map, a working knowledge of the coordinate systems, and maybe a few waves of the hand, any observer can find almost any object visible.
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