Tuesday, May 22, 2012

Exploring the Night Sky - Polaris, Inclinometers, and a Really Big Dipper!



An important part of being a naturalist is observing the night sky. While you don’t have to be an astronomer, it is good to know a few basics. But there’s more to knowing constellations than just impressing girls at the next back yard barbeque. Knowing the sky can assist you in navigation down here on the ground, and just might end up saving your life.

The first and most basic skill any North American naturalist should have is the ability to find the North Star, otherwise known as Polaris. In an age of electronically mediated navigation, knowing where to find the North Star is the most basic (and easiest) direction finding technique that requires ZERO technology. The concept is very simple. First you want to find the Big Dipper in the northern sky. (It’s pretty easy- it looks like a big dipper.) Find the two stars that form the right side of the dipper – or what would be the “front” of the dipper were you looking at it three dimensionally. If you draw a line through those two stars pointing up, that line will pass right through Polaris, which is the brightest star in the immediate area.  I found a great picture that illustrates this. (I would credit the graphic design appropriately but I have no idea who did it!)



This image might seem familiar to those of you from Alaska. If you're not from Alaska, this will be a very useful bit of trivia somewhere down the road. This Big Dipper/Polaris image is also the exact design of the Alaskan flag seen here: 





This the tough part. That big bright star in the corner of both of these images is the North Star..which is NORTH. So... if you're facing Polaris, SOUTH is behind you, EAST is to your right and WEST is to your left. 


What most people may not realize - and why the North Star is such a trustworthy guide - is that it is a fixed point in the sky. The entire night sky rotates around the North Star. If you've ever seen a time lapse photo of the night sky, you will clearly see that all the other stars are "moving" but good ol' Polaris is stuck right in the middle. That being said, depending on where you are on the continent, sometimes the Big Dipper will dip below the horizon. If you can't find it, don't panic! It will come back around eventually and you will be able to pinpoint North. 


Now here’s another interesting part. If you happen to own an inclinometer or sextant, you can very accurately measure the distance between Polaris and the horizon. That measurement is your latitude – or distance in degrees above the equator. For example, here in Shreveport, Louisiana, the latitude is 32.4681° N. That means that the city of Shreveport is a little over 32 degrees above the equator on the map. And, were you to stand in my back yard and measure the distance between Polaris and the assumed horizon, it will be 32.4681°. Since most people don’t own an inclinometer or sextant, just for fun you can eyeball it and see if the numbers are close. 


As a very nerdy addendum, next time you take a long trip north or south, pay attention to the location of the North Star. In 2001, I went on a very long road trip to Eastport, Maine, with my friend Janet Owen. On a random highway in the thick woods north of Perry, Maine, we stumbled across this unbelievable marker on the side of the highway. (Please note that the early summer season in Maine was MUCH cooler than we expected and we had to borrow these ridiculous jackets from a dusty chifforobe owned by my friend D.J. Sutherland in Eastport.)






We were halfway between the Equator and the North Pole! Now applying what we've learned here today, had I observed the night sky on this journey and made a measurement with an inclinometer, the North Star would have been 45°above the horizon. Conversely, two weeks before this trip, Janet and I had both been on a cruise with a jazz band from our college, Angelo State University. On the cruise, we traveled all the way to Playa del Carmen, Mexico, which has a latitude of 20.6167° N. While were on the cruise ship, I actually did observe Polaris because the stars on the open ocean were so incredibly bright. Predictably, Polaris had sunk toward the horizon. The farther south you travel, the more the North Star moves closer and closer to the horizon. Had we gone all the way to the Equator, the North star would have been level with the horizon. Furthermore, I've never been to the North Pole, but if I ever get there I'm gonna look straight up because Polaris will be directly above my head - or 90° - which means the latitude of the North Pole is 90.0000° N. The longitude? 0.0000° W. 


Why does all this matter? In our modern world to average people standing in their back yard it doesn’t matter much. However, were you ever stranded at sea or lost in an incredibly remote area after a plane crash, being able to pinpoint your latitude might assist rescuers in finding you, or even assist you in saving yourself. (If you think this sounds like an outrageous possibility please take a second to read this article. It took these plane crash survivors two months to figure out where exactly they were when they crashed.) 

http://en.wikipedia.org/wiki/Uruguayan_Air_Force_Flight_571

However, what I would argue is more important than determining latitude is simply knowing how to find the North Star. This is very basic, but if you were lost somewhere and you knew there was a town or river north of your location, being able to site the North Star would show you the way. This seems elementary, but sometimes when you’re under duress even the simplest things can become complicated.

I heard a poem once about how cowboys driving cattle on the open plains would point the tongue of their chuck wagon toward the North Star at night. That way in the morning when they awoke and the whole Great Plains landscape looked exactly the same, all they had to do was look at the wagon tongue and know which way to drive the cattle.

It sounds silly, but under any circumstance where you were lost, step #1 is to find which way is North – then by default you gain your bearings with every other direction. In modern society, we are so far separated from the stars and their importance that people tend to take them for granted. For thousands of years, sailors used only the stars to navigate across open oceans, and once the chronometer and sextant were invented, sailors could pinpoint their exact location on the face of the earth to within a mind boggling two or three miles – with no computers, no satellites, and no GPS!

Once people understand that ALL navigational principles are derived from the stars above us, they will see why it’s important to know at least the most basic astral navigational aids. Once you’ve learned about the Big Dipper, Polaris, and how they relate to latitude you can graduate onto bigger things - like next week’s blog about determining your longitude with a chronometer!

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