NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Roger W. Sinnott
Date: 2017 Dec 12, 19:57 -0500
List:
Here's yet another variation on the Kamal idea: a sky crossbow. The illustration is from an article I wrote for Sky & Telescope (May 1981, page 417) and is self-explanatory. No auxiliary table, slide rule, or trig is needed.
The stick length, 57 inches, assumes you put the lower end against your cheekbone, so the distance between the yardstick and your eyeball is an extra fraction of an inch beyond 57 inches -- a close approximation to the 57.3-inch length of one radian.
If there is any doubt about the crossbow's accuracy, measure Spica to Arcturus. Their distance should be 32.8 inches on the yardstick, which is also 32.8º on the sky.
The idea is in no sense original -- going back to at least Edmund Gunter in the 1620s.
Roger
