An Order Of Magnitude

Astronomy is a rewarding study in its own right, covering everything from planets, to stars, to galaxies, and the universe itself. It can be as easy to understand as you prefer, or as hard a challenge as you want. There are probably very few people who don't—at some point—think “That's interesting.”

It's a module of study in Chongdo. Because we lack the time and resources to procure telescopes, and we're based in an area with poor long-range visibility anyway, we unfortunately cannot spend significant time getting into the details of astrophysics at a level which does this science justice. However, we are acutely interested in ground-based studies that provide value.

For example, the motions of the Sun and Moon provide valuable tools to measure time, while the Sun is easy to employ for rapid navigation or geo-positioning as well. At night, the stars provide a wealth of information on navigation.

In dealing with navigation, the student should ideally know five constellations (two of which are actually asterisms, but that's not relevant for purposes of this essay). No matter where you are on the Earth at night, you will be able to determine your direction by finding one of these constellations...if conditions are clear.

The problem is when conditions aren't quite clear. Fortunately, the five constellations we teach are among the brightest in the sky to observe, so even when the skies are gray and murky, or you are in a brightly lit city, you stand a chance of spotting one of the five if you can identify its stars.

But not all stars are equally bright. One star, compared to another, may be brighter or dimmer. Brighter stars show up sooner in the evening sky, while dimmer stars predictably show up later. Many people can identify the Big Dipper (or think they can—most people we've quizzed actually point to the Little Dipper), because its seven-star pattern is so distinct. But what about when only three of the stars are there?

The difference between one star's brightness and another's is termed magnitude. The lower the magnitude, the brighter the star. That isn't particularly intuitive, and the situation gets worse: there are very bright stars with negative magnitude, and there's no easy way to identify a star's magnitude without a lot of work or a reference. A star with a magnitude of 1 is not twice as bright as a star with a magnitude of 2. The entire system is woefully confusing.

Below, we list each of the five constellations we study in detail. For the brightest stars shown, we provide the magnitudes as a quick reference. At the end, we'll cover why this is useful to know to someone finding his way.

This constellation is part of Ursa Major, and is readily known as The Big Dipper. The two right-most stars in this picture always point to the North Star. Of course, during the night, the Dipper rotates around the North Star, so this picture may need to be spun. As the night sky darkens, α, ε, and η will appear first, followed by β, γ, and ζ. Last will be δ. If you can find α and β, you can find your way.	α +2 β +2.4 γ +2.4 δ +3 ε +2 ζ +2.4 η +2
This constellation is part of Ursa Minor, and is more familiar as The Little Dipper. The last star in its tail is α, the North Star. The North Star always rests over a point in the horizon that is due North. Its height in the sky will vary by your latitude: the farther North you are, the higher the star is in the sky. At the Equator, it dips below the horizon. So anywhere on the Northern Hemisphere, if you see the North Star in the sky, the point on the horizon just below it is Due North. Its stars appear from the North Star first, in order down the Dipper's handle, and end at the cup. The star η sometimes will not appear if the skies are cloudy or bright.	α +2 β +2 γ +3 δ +4.4 ε +4 ζ +4 η +5
This constellation is Cassiopeia. Its distinctive W-shape is easy to recognize in the Northern Fall skies. It's essential to note that the three middle stars of the W form a triangle that point toward the North Star. If you can find Cassiopeia, you can find North. The end two stars appear first, followed by the middle star. The left two stars (remembering that left is true for the picture only, as the constellation rotates!), appaer last. Note that in your position, you might see Cassiopeia as an M-shape.	α +2 β +2 γ +2.5 δ +3 ε +3.4 ζ +4
This constellation is Crux, and is more familiar as The Southern Cross. There is no South Star to complement the North Star, so people in the Southen Hemisphere easily recognize the Cross. Two dangerous myths exist (among Northerners) about the Cross: first, its tail does not always point South. Instead, it points to an imaginary point in the sky that is over the Southern horizon. There are a few easy tricks to determining South. Basically find a spot on the horizon that the tail points to. Then find a place where the crosspiece points to. Half the distance between them is pretty close to South. The four main stars are fairly close in magnitude, so they should all appear at about the same time.	α +2 β +1 γ +2 δ +3
This constellation is Orion, and is easy for most people to spot. The second myth about the Southern Cross is that it is always visible from the Southern skies. In fact, there are times during the year that the Southern Cross is not visible in many key locations. Fortunately, if these tend to be toward the Equator...where Orion is visible overhead. Orion's belt moves like an arrow from West to East. In fact, its star δ sits on the Celestial Equator. The further you travel South, the less true this becomes: fortunately, you descend South enough to where the Southern Cross becomes visible. Similarly, if you move North of the Equator, Orion's motion becomes more circular—but then, the first three constellations above come into view. Consider Orion that perfect overlap of when you're neither North or South. His right shoulder and left knee appear first, and all other stars basically appear together. Because all these stars are so bright, and Orion so large, it should be easy for a novice to find.	α +0.5 β +0 γ +2 δ +2 ε +2 ζ +2 κ +2

Note: Chongdo acknowledges to astronomy buffs that our magnitude numbers are rounded for easy reference, and that many of these stars are variable stars whose brightness fluctuates over time. But these will be close enough for navigation purposes.