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Last Monday, the 1st of December, I am sure that many of us happened to notice two bright planets (Venus and Jupiter) next to the moon as we were heading home from work. It was a rare and beautiful phenomenon, and so I rushed home hoping to take some pictures. Unfortunately, between the cold temperature and long exposure time necessary to take a night shot, I couldn’t keep steady enough to get a good picture (I have a tripod, but I cannot remember where it is). As I was muttering to myself and walking back to the house, I looked to the north and saw an old friend winking at me: the North Star.

The North Star, Polaris, the Pole Star, Giwedin’anung (the Anishinaabeg word for it); it carries many names. It is universally important in the star lore of peoples inhabiting the northern hemisphere for one major reason: it stays in the same place. Of course, Polaris does move, but from our perspective it appears to be stationary because the north pole is currently pointing in its direction. I say currently because Earth’s axis wobbles over time. However, unless modern medicine finds a way to bestow immortality, we will all be long dead before the wobble unseats the Pole Star from its throne. When the Egyptians were aligning the Great Pyramids, the star Thuban in the constellation Draco was the North Star; In about 1000 years the binary star Gamma Cephen in the constellation Cepheus will take the title. Kappa Draconis, also in Draco, was the star that Long-Suffering Odysseus would have looked to for guidance during his quest to return to Ithaca. For now, Polaris is actually getting closer to true north, and will continue to do so until the year 2120, so that will be the star we will concern ourselves with.

For the star to be of any use, you first have to find the darned thing. Once you know what to look for, it is pretty easy to locate. Polaris itself is located at the tail end of Ursa Minor, better known around here as the Little Dipper. The Little Dipper is not the most prominent constellation in the night sky, but it has two easy to locate constellations near it: The Big Dipper and Cassiopeia.

Ursa Major is shown on the left, and Cassiopeia on the right

The circumpolar stars (the stars that surround the North Star) rotate around Polaris throughout the night. What is nice about the Big Dipper and Cassiopeia is that they are on opposite sides of Polaris, so when one of them is below the horizon, the other is still high in the sky. Tonight, for example, Cassiopeia will be at about its highest point in the night sky at around 8:00 pm local time; due north and directly above Polaris. The Big Dipper will be well below the horizon at that time, but as the night progresses, it will become visible towards morning. If you can find those two constellations and remember which way they face, you can always find Polaris.

The most obvious use of the North Star is to find north (duh!). There are many viable daytime methods of finding north without a compass, but methods like the shadow stick are time consuming, and methods like the watch method require an analog timepiece. Finding the North Star requires only a glance. Now most people in a survival situation, unless they are in the desert or at sea, most likely will not be traveling through the night. The best thing to do would be to mark the direction of the North Star with a stick or a couple of stones that can be used in the morning to reference against natural landmarks, giving you a bearing.

What if you have a compass? That should tell me exactly where north is anywhere I may be, right? Not quite. The magnetic compass probably rates with fire and toilet paper as one of the greatest discoveries of humanity. It enabled ship captains (who previously had Polaris by night, but by day had to guess direction based on the sun and wind if they left sight of land) to navigate more safely and accurately than ever before, and was a crucial factor in the Age of Exploration. There is only one problem: a compass only points due north on two lines of longitude (the vertical lines on a globe). That is because the magnetic north pole is several hundred miles away from the true north pole. But wait, there’s more! In addition, magnetic north is always moving; not fast, but fast enough that aviation maps have to be updated every six month or so. Most good navigation maps that you would buy will be factored for local magnetic declination (the difference between the two norths), and will have a magnetic north arrow that you will align your compass with, which will orient the map to true north.

But what if you have a map without that correction? Or what if you know that a good place to go is due east, but you don’t know the local correction? According to the NOAA, my home here in Minnesota is only 25 minutes of arc (a little less than 1/2 of a degree) off of true north, but if you are in Anchorage, Alaska that difference is almost 20 degrees! To put that into perspective, if you walked one mile without correcting for magnetic declination near Anchorage, you would move 1/3 of a mile to the right of your intended path. That is a good way to get hopelessly lost.

compass-declinationPolaris, as we know, lies at true north. If you do not know the exact magnetic declination correction for your location, all you need do is point your compass at Polaris, and adjust the dial so that your compass needle is pointing to north. If you were traveling long distances, by correcting your compass each night against Polaris you would keep in tune with local magnetic declination as you travel, keeping compass error to a minimum. It is important to note here that no compass is perfect and all compasses (even the best tuned) will have an error ranging from fractions of a degree in highly tuned compasses,  to perhaps a few degrees in really cheap or damaged models. If you do know your local declination conversion, Polaris is still useful for determining how accurate your compass is. As I believe that all essential gear should be tested before you are in a situation where its performance might prove critical, this would be a good test to perform in your backyard before the big trip.

There is another useful purpose that Polaris has to offer: finding latitude. Latitude is a measure (in degrees) of how far north or south you are on the globe. When you are standing on the equator, you are at 0 degrees latitude; at the north pole you are at 90 degrees north latitude; at my house you are at approximately 46.85 degrees north latitude. While for most wilderness excursions knowing your latitude is not really that important, it is still a neat thing to understand. If you are ever lost at sea, knowing your latitude could be vital in finding out your location. GPS units can do this at the touch of a button, but Murphy’s Law, the most consistent law in the universe, implies that when you really need your GPS, the batteries will be dead.

I have a nifty surveyor’s compass that belonged to my Grandpa Abe, who was a mining engineer up on da Range (if you have ever been to northern Minnesota you will know what I mean). It is a highly accurate magnetic compass that also can measure altitude by using the aiming sight in conjunction with an internal bubble level. I can determine my approximate latitude by measuring the angle of Polaris above the horizon (when adjusted so the bubble is at the level mark, in this case). If I measure the altitude of Polaris at 50 degrees, my latitude is 50 degrees north. I will admit that it is a bugger to use this compass at night (you will find it rather hard to measure Polaris by day) since you have to use a flashlight to see the bubble, which ruins your night vision.

On the left is a precision surveyor's compass that can measure alltitude, and on the right is my 81.5 cent sextant

On the left is a precision surveyor's compass that can measure alltitude, and on the right is my 81.5 cent sextant

I decided to try making my own mariner’s astrolabe (a method of determining the altitude of Polaris from the early Age of Exploration) on a tight budget of one dollar.  The final result requires:

  1. a protractor (80 cents)
  2. a straw (free at restaurant)
  3. 4 inches of duct tape ($6.00 for 60 yards = 1.1 cents)
  4. 8 inches of cotton twine (I am not sure about the math so I will allocate a cost of 0.4 cents; accounting is not as exact of a science as you might think)
  5. a barrel fishing sinker (free, found on fishing pier)

This leaves me 18.5 cents to invest in my IRA, and a rough measure of latitude. You can see how I assembled it up above; just tape the straw to the protractor and run a weighted string from the little hole made for using it as a drafter’s compass. To use, just look through the straw at Polaris, wait for the string to settle, and pinch the string against the degree scale. Cheap plastic protractors are not designed for navigation, so to get the right latitude you will have to take the smaller of the two numbers that the string is resting on (protractors usually have a two 180 degree scales running opposite directions) and do some simple math:

  • 90 – degree reading = observed latitude

I say “observed” because there are mitigating factors, like atmospheric pressure, that can refract light and alter the perceived position of Polaris. However, anyone using a protractor to measure latitude is not going to be navigating a 747, so don’t sweat the small stuff.

This device would not be a modern navigator’s first choice (or even fifth choice for that matter) for celestial navigation, but much of the world was explored and mapped using a compass, a log line to determine ship’s speed, and an astrolabe not much more sophisticated than this.

To conclude, I would recommend that anyone who spends time in the wilderness should learn to find the North Star. If nothing else, you will be a hit at bonfires. Just leave the protractor astrolabe at home; most laymen won’t appreciate its subtleties.