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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Average altitude of a celestial sight
From: Frank Reed
Date: 2020 Aug 17, 15:30 -0700
From: Frank Reed
Date: 2020 Aug 17, 15:30 -0700
I'll try this again. What is the average altitude of a star? Let's ignore limitations on visibility and assume that we can see all stars from 0° to 90° altitude. Everybody's first guess is 45°. But that can't be... There are many more stars below 45° altitude than above 45°.
Consider the 57 navigational stars. They're evenly-spaced around the celestial sphere. From a random location at a random time of night, half of them, 28.5 on average, will be above the horizon. Of those, on average about 20 will be below 45° and 8 will be above 45°. An average sextant altitude will necessarily be below 45°. So what's the actual average?
Frank Reed
