Make a Star Wheel!
The motion of the stars marks the passage of time during the night. As Earth turns on its axis, the stars appear to rise in the east and set in the west, just as the Sun and Moon do. This means that you'll see different stars overhead at different times of night. Likewise, as Earth makes its annual trek around the Sun, you'll see different stars from month to month.
So what stars will be in your sky tonight? To find out, follow these simple directions!
Making the Star Wheel
First, you'll need to display (left mouse click) or download (right mouse click) the two parts for your Star Wheel. Make sure your computer can display PDF files; if it can't, download and install the free Adobe Reader.
Each part for the Star Wheel is sized to fit on a single sheet of letter-size paper. Print out both sheets and cut out the parts. For the sky map (Part 1), trim away the gray corners so that you're left with a circle 8 inches across. For the outer sleeve (Part 2), make sure you keep the large white rectangle at the bottom; also, cut out the white oval in the middle.
To assemble your Star Wheel, fold the white rectangle at the bottom of the outer sleeve so it's underneath the front. Then staple the rectangle to the front at the locations marked by short white lines to either side of the oval. Now slip in the circular sky map so it shows through the oval. That's it!
Pick the date and hour you want to observe, and set the Star Wheel so this date (on the rim of the circular disk) matches the time indicated along the edge of the outer sleeve. Use white hours when standard time is in effect and orange hours when clocks are set for daylight-saving (summer) time.
The Star Wheel's large oval shows the whole sky, and the oval's curved edge represents the horizon you're facing. Once outside, hold the Star Wheel out in front of you and look at the yellow "Facing" labels around the oval. Turn the entire wheel so that the yellow label for the direction you're facing is on the bottom, with the lettering right-side up. If you're unsure of your directions, just remember where the Sun sets; that's west.
This Star Wheel is usable for northern latitudes between 30° and 50°, which covers virtually all of the continental U.S., southern Canada, and Europe. It includes the names of the brightest stars and the most prominent constellations. Depending on how dark the sky is in your area, there may be more stars overhead than are shown on the map. Everyone's sky looks a little different. If there are fewer stars visible to you than appear on the Star Wheel, try to find an observing site that is not flooded by house or streetlight. Also, the longer you're outside, the better the chance that your eyes will adapt to the darkness and the more stars you'll be able to see.
Begin by locating the Big Dipper. This giant spoon is actually part of a larger constellation called Ursa Major, the Great Bear. Find the two end stars in the Dipper's bowl — look opposite the handle. They're known as the "pointers." Why? Because a line drawn between them and extended away from the bottom of the bowl leads you to Polaris, the North Star. Now that you know how find Polaris, you also know how to find due north no matter where you are in the Northern Hemisphere!
No matter how well you know the sky, you'll find that a star wheel (sometimes called a planisphere, comes in handy for a quick check of "what's up" on any given night. Click here for a better version of the star wheel you see here.