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.
Support Much improved! Just one suggestion, there is actually one last step: 5) read the elevation from the index bar. You might have the measurement "40°" circled briefly. It would make clear the purpose of the device. --
Bridgecross02:38, 9 April 2007 (UTC)reply
Support. Perfect! I never knew how to use one of those things, and after just looking at the thumbnail image for a couple loops, it makes sense. —
BRIAN0918 • 2007-04-09 13:26Z
Question: Would you really see the sun as a full circle? Wouldn't it just be a half-circle? —
BRIAN0918 • 2007-04-09 13:28Z
Answer - Yes, a full circle whose size depends on the telescope in use. On the left part of the horizon mirror, which is in fact a transparent glass, the sun's image is dimmer because the reflectivity of the glass is lower. In practise, our eyes seem to melt both images.
Alvesgaspar13:51, 9 April 2007 (UTC)reply
Yes, it is possible but I don't have the time right now. I'll have to go back to the (Corel) drawing board and double the number of frames. -
Alvesgaspar20:54, 9 April 2007 (UTC)reply
Info - Brian0918 question made be realize the animation had a mistake: the white boundary line between the glass (left) and the mirror (right) should also rotate. It is fixed now.
Alvesgaspar18:40, 9 April 2007 (UTC)reply
Weak oppose. Much improved, indeed, but I still don't like the simple "squishing" of the instrument when it is tilted. There really should be some perspective in that part of the animation. --
Janke |
Talk06:05, 10 April 2007 (UTC)reply