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The Bushwalker's Guide to the Galaxy Home Page
An Introduction to the Bushwalker's Guide to the Galaxy
Improvised Angle Measuring Techniques
Finding Reference Directions from your Surroundings
by Alan Sheehan B.E.
Finding Direction from the Constellations
Finding directions from the constellations involves a number of steps.
Firstly we need to identify a constellation we can use, so the observer needs to “learn” that constellation or "asterism". An asterism is a pattern in the stars.
When the constellation is on the celestial equator, such as Orion, we can use this fact to find east or west when the constellation is low in the sky i.e. either rising or setting.
Most of these methods, however, involve finding either the North Celestial Pole (NCP), or the South Celestial Pole (SCP). This is done by knowing the geometry of the constellation and using the handspan method for measuring angles to navigate across the sky to either the North or South Celestial Pole.
In the Northern hemisphere, the NCP is above the horizon, and the SCP is below the southern horizon, and vice versa for the Southern hemisphere. True North and True South are on the horizon directly above or below the NCP and SCP respectively.
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