Wikipedia:Featured picture candidates/Marine sextant

 
The animation illustrates the use of a marine sextant at sea, for measuring the altitude of the Sun above the horizon. This information, coupled with the knowledge of the exact time and the position of the Sun in the celestial sphere at the moment of the observation, allows the determination of a line of position, with an accuracy of about 1-2 nautical miles
Reason
This is a revised version of an animation already nominated in WP:FPC. I believe it helps to better understand the basic principle of the instrument and illustrates cleary its use in celestial navigation. The picture file contains a detailed explanation of the numbered frames.
Articles this image appears in
Sextant, celestial navigation
Creator
Joaquim Alves Gaspar

Promoted Image:Using sextant swing.gif --trialsanderrors 04:57, 15 April 2007 (UTC)[reply]