Map, Compass & GPS

Map, Compass & GPS
Wild flowers along Fall Creek on the way to the Green Lakes - Oregon

Tuesday, December 2, 2014

The North Star - A Star to Guide Us

The North Star is a beacon that we can use to guide us in the backcountry.  Few hikers use the celestial bodies in the night sky to navigate by.  But on a clear night, the night sky provides a feature that is an excellent source of direction.  It doesn’t matter if it is June or November, if you are in Wyoming or Oregon.

For the backcountry hiker consider that Polaris is fixed in position over the northern pole.  Unique from other celestial stars and planets, Polaris is very closely aligned to the earth’s axis.  Stars and planets rotate around Polaris.  And like the sun, this rotation is from east to west through the sky.  Polaris will be found approximately half way between the northern horizon and straight overhead.  In the northern hemisphere, Polaris can found in our northern sky and is never more 1° from true north – the North Pole. 

Constellations help locate Polaris.  Cassiopeia and the Big Dipper point to Polaris.  Uniquely, Cassiopeia, the Big Dipper and Little Dipper can be seen in relation to Polaris year round.  In winter, the constellation of Orion will also help locate Polaris.

Figure 1.  The Pointing Stars point to Polaris

In the case of the Big Dipper (above), an imaginary line is drawn from the two pointer stars to Polaris.

 Polaris will be found about at a distance of five times the space between the two pointing stars.

Another view of Polaris and adjacent constellations is seen below.

So what does this do for the hiker?

The essence is that Polaris is another visual handrail at night.  In an earlier post, I discussed the process of orienting a topographic map.  Large terrain features were identified as “backcountry handrails.” (Handrails can include roads, railroad beds, ridgelines, power transmission lines and streams.) Handrails help align the map and give the traveler a sense of relationship to the topography both on the map and what is nearby.  For example, if the hiker determines that Butler Butte will always be to the left and west of the trail then that butte becomes a visual aid for navigation. At night geographic features may not be quite so visible and distinct.  So on a clear dark night Polaris can aid the wilderness navigator by providing direction to true north.

This visual reference compliments a magnetic compass.  (Ideally the hiker uses a declination adjustable magnetic compass.)

It's always right there in the same place (even if you can't see it at the moment) and doesn't require batteries.

Cloud cover and forest canopy will limit the ability to navigate and use Polaris.  If Polaris is completely obscured but some sky is visible, attempt to find east.  Like the sun, stars and planets rotate through the sky from east to west.  Find a star and monitor its movement over a period of a few minutes.  Once you’ve determined where east is, north is to the left.

Like all navigation skills, using the night sky takes practice.  Before heading out on your next adventure, practice at home, look for Polaris at varying times. Observe the star’s relationship to the other celestial bodies.

Here is another post on the North Star from my local newspaper.

Here are a couple of good references:

  • June Fleming’s book Staying Found is a fine reference about backcountry navigation. 

  • Google’s Sky Map

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