Things You'll Need
Instructions
Examine the planisphere and note that the large round dial--often sandwiched between two sheets of plastic on the star chart--can be moved clockwise or counter-clockwise. The dial contains the months of the year, as well as the days for each month. Indicated on the front of the round section of plastic covering the dial, are times of the evening when star-viewing is possible (often presented in "military time" using a 24-hour clock). A large oval window in the center shows the constellations that are viewable on the time and date dialed.
Find true north by locating Polaris, which can be found using the easily recognizable &̶0;Big Dipper&̶1; constellation pattern. Find the &̶0;handle&̶1; of the dipper, shift your gaze to the &̶0;cup&̶1; or &̶0;dipper&̶1; part of the constellation, and then locate the two bright stars at its farthest edge. Form an imaginary line from those two stars straight up until you see the tip of the handle of the &̶0;Little Dipper&̶1; and the bright star waiting there, Polaris. Unlike the other stars and constellations that move across the night sky, Polaris remains fixed, and will always indicate true north by sighting it and then drawing an imaginary line from it straight down to the horizon.
Dial the date and the corresponding time on the planisphere. At this point, you'll probably need to use a flashlight with a red lens to see what you're doing. A red light will not interfere with your ability to see the stars. The inner dial usually displays the months and days of the month, while the times are listed around the viewing window of the date dial. (Figure 1) Bear in mind you'll need to make adjustments for Daylight Savings Time (subtract an hour).
Stand facing the north horizon. Hold the planisphere over your head and match the north heading on the planisphere to the northern horizon. South will be behind you. Make sure west, as represented on the planisphere, is to your left, and east is to your right. You may have to turn the planisphere so that all four directional points match up. The area marked "zenith" on the star map should be directly overhead.
Remember that the actual viewable night sky and the one represented on the planisphere will differ, in that the star map inside the small window is a much smaller, condensed version of the night sky. Locate a recognizable pattern of stars and check it against its location on the planisphere (Figure 2).