Finding your way in the sky

Finding north with Polaris

Polaris, the North Star, sits almost directly above Earth's north pole. As the sky turns through the night, it barely moves, so it shows you where north is.

To find it, locate the Big Dipper. Take the two stars at the outer end of the bowl, called the pointers, and follow the line they make away from the bowl. Go about five times the gap between them and you reach a moderately bright, fairly lonely star. That is Polaris.

Polaris is not the brightest star in the sky; it is about magnitude 2. Its height above your horizon roughly equals your latitude, about 40 degrees from most of Türkiye or the central United States. From the southern hemisphere it cannot be seen.

The celestial sphere

Astronomers picture the sky as a giant sphere around Earth, with the stars painted on its inside. This celestial sphere is not real, but it makes positions easy to describe.

Your horizon is where the ground meets the sky. The zenith is the point straight overhead, and the whole sky seems to turn around the celestial poles, near Polaris in the north. Because Earth rotates once a day, stars rise in the east and set in the west, except those near the pole, which circle it without setting.

Altitude and azimuth

Two numbers tell anyone where to look from their own spot. Altitude is the angle above the horizon, from 0 degrees at the horizon to 90 degrees at the zenith.

Azimuth is the direction along the horizon, measured in degrees clockwise from north: east is 90, south is 180 and west is 270. A star at altitude 30 and azimuth 135 is a third of the way up the sky in the southeast.

These numbers change through the night and with your location, which is why star chart apps ask for your position.

Measuring the sky with your hand

Your hand, held out at full arm's length, is a handy ruler. Because longer arms usually go with bigger hands, it works surprisingly well for most adults.

Your pinky finger covers about 1 degree, roughly twice the width of the full Moon. Three middle fingers together cover about 5 degrees, a closed fist about 10, and an outstretched hand from thumb tip to pinky tip about 20 to 25.

Try it on the Big Dipper: the pointer stars are about 5 degrees apart, and the whole Dipper spans about 25 degrees. Once you can measure, directions like 'about 15 degrees above Venus' become easy to follow.

Star hopping

Star hopping is the classic way to find things you cannot see at first. You start at a bright star you know, then move in short, measured jumps along recognizable patterns until you reach your target.

For example, follow the curve of the Big Dipper's handle away from the bowl to arrive at the bright orange star Arcturus. From the Summer Triangle you can hop along Cygnus to find fainter stars and clusters. Write each hop down or sketch it, and the route will be easy to repeat next time.

How to prepare for a night out

Your eyes need time to adjust to darkness. The pupils widen within seconds, but the full chemical change in your retina takes about 20 to 30 minutes, and one glance at a white screen or headlight can undo much of it.

Use a dim red flashlight to read charts, because red light disturbs night vision much less than white. A strip of red cellophane over an ordinary torch works fine.

Star chart apps can show what is overhead when you point your phone at the sky. Turn on their red night mode and lower the screen brightness. Never point binoculars or a telescope near the Sun; only a certified solar filter meeting ISO 12312-2 makes solar viewing safe.