Friday, August 5, 2011

Learning the Constellations

Learning your way around the sky at night is a matter of learning to see some of the patterns in the stars so that you can pick out particular stars, and have an idea of where other stars are with respect to them. It's a piecemeal process that takes a bit of time, but is very rewarding.

One Step At a Time

Don't expect to learn a lot of constellations all at once, or, if you do, don't expect it all to stick. Part of the challenge is that the constellations change their place in the sky all the time, and that the ones that are visible will vary by the season.

Because of this, if you learn some constellations tonight, then come back out under the sky in a few weeks, the constellations will have moved. As the Earth goes around the Sun in its orbit, the constellations up at a particular time of night will change a bit and those that stay up will appear to have moved in the sky. They will also change their orientation, so the stars that were on the bottom are now on the side.

Don't be discouraged. Learn the stars by relative positions. Turn yourself and your body around to see the patterns you've memorized. Where possible, get out often to see them before they've changed beyond recognition.

Season's Greetings
Since different stars are up in the early evening at different times of the year, it's also useful to divide the constellations you know by the season you see them. For myself, The Archer, The Scorpion, The Snake-Handler, and The Virgin are summer constellations. Orion, the Big Dog, Small Dog, and Gemini are winter constellations. Perseus the Hero, Andromeda, and Pegasus are spring constellations.

When I see one of these, I think of the others and locate them in the sky by the one I see first. In fact, these constellations are not just visible in the season I think of them belonging to, but that's when I learned them, and that's when I know I can see them on a clear night with a good view of the sky around me. It breaks up the job of learning what's where.

High and Low
It's often easiest to locate new constellations when they are either near the horizon in some direction, or at the highest point in the sky. The ones that are in-between often seem to be harder to get a handle on, unless they have some special feature that makes them easier to see as a constellation, like the Big Bear's seven stars of the Big Dipper that are all about the same brightness in the same part of the sky.

With a star chart for the time of year you're out, and the time of night, you can see what should be near the horizon in any given direction as well as what should be directly overhead. Pick out particularly bright stars on the chart to use as guides. Then find other bright stars on the chart, and locate them with respect to the first one you found. Then look at the less bright stars, and get them placed with the constellation they belong to. After a while, you should be able to see the "picture" of the constellation in the sky.