NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Brad Morris
Date: 2013 Feb 15, 15:29 -0800
In our first lessons in circles of equal altitude, we are shown a lamp post and a circle of equal angles construction is shown. Next, we are told that for stars, the lines are nearly parallel.
In Figure 1 we see our construction when the angle is 89.999999999999 degrees. This results in an apex height of 1.44e22 inches! That's pretty big. What's that in miles? 2.28e17 miles. What's that in light years? 38788.43 light years.
HANG ON! What is the angle to Alpha Centauri, our closest neighbor? 89.99999999035 degrees ( 89 deg 59 minutes 59.99997 seconds. In other words, nearly parallel, but not so.
Given the DISTANCE to the navigational stars, we can compute the angle of the NOT parallel light rays!
What if our baseline is the Earth's Orbit instead of the earth's radius, at 92,000,000 miles radius. The angle for Alpha Centauri is now 89 degrees 59 minutes 59.19 seconds. In otherwords, while we may not see a parallax shift with a hand held sextant, we may be able to see it with very precise instruments.
Regards
Brad
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