APOD:2015.9.28

Sweet丿Kim (金) 天王星
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发表于:2015-09-29 13:03 [只看楼主] [划词开启]

瓦特顿湖国家公园上空的月食 

影像提供与版权:

 Yuichi Takasaka / TWAN / www.blue-moon.ca

说明:

这幅摄于2014年4月的月全食影像系列,南眺地球.加拿大.亚伯达省.瓦特顿湖国家公园内冰封的瓦特顿湖。地平线最后方的山峦,则是位在美国冰河国家公园之内的雪峰。这幅每十分钟曝光一次的影像,由左至右,捕捉了滑过崎岖天际线和瓦特顿镇上空的月亮之位置和月食进程。因此,从这张时序影像,可以推算出全食阶段的长度约为80分钟。


远在公元前270年,希腊天文学家阿里斯塔克斯也测量过月食的长度;然而,当时他可能并无法借助于数位时钟和相机。不论如何,应用几何学,他找出了一个简单但极为精确的方法,用地球半径为计量单位与月食长度来推算月亮的距离。这幅现代的时序月食影像,也追踪了位在月亮右上方的火星、泛红月盘右上方的明亮角宿一与左下方的土星之位置变化。

(Waterton Lake 瓦特顿湖;

Glacier National Park 冰河国家公园;

Aristarchus 阿里斯塔克斯;

Spica 角宿一)




———————————————————————————————————————————


Total Lunar Eclipse over Waterton Lake 

Image Credit & Copyright: Yuichi Takasaka / TWAN / www.blue-moon.ca

Explanation: Recorded in 2014 April, this total lunar eclipse sequence looks south down icy Waterton Lake from the Waterton Lakes National Park in Alberta, Canada, planet Earth. The most distant horizon includes peaks in Glacier National Park, USA. An exposure every 10 minutes captured the Moon's position and eclipse phase, as it arced, left to right, above the rugged skyline and Waterton town lights. In fact, the sequence effectively measures the roughly 80 minute duration of the total phase of the eclipse. Around 270 BC, the Greek astronomer Aristarchus also measured the duration of lunar eclipses - though probably without the benefit of digital clocks and cameras. Still, using geometry, he devised a simple and impressively accurate way to calculate the Moon's distance, in terms of the radius of planet Earth, from the eclipse duration. This modern eclipse sequence also tracks the successive positions of Mars, above and right of the Moon, bright star Spica next to the reddened lunar disk, and Saturn to the left and below.


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