下午8字曲线
(原标题: Afternoon Analemma)
2023-09-23
浏览次数: 15
八字曲线是你在一年中每天同一时间标记太阳位置时得到的8字形曲线。为了拍摄这张照片，我们在新西兰南部的天空中设置了一个4x5的针孔相机。在每个晴朗的日子里，当地时间下午4点，快门都会被短暂打开，曝光相同的光敏玻璃板，时间跨度为2022年9月23日至2023年9月19日。在冬至和夏至这两天，快门在主曝光15分钟后再次打开，并一直打开直到日落，在曲线的底部和顶部形成太阳轨迹。春分日期对应于曲线中间的位置，而不是交点。当然，与从北半球绘制的八字曲线相比，这条曲线本身是倒置的。虽然今天北半球的秋天是从秋分开始的，但南半球的秋天是春分。
查看原文解释
An analemma is that figure-8 curve you get when you mark the position of the Sun at the same time each day for one year. To make this one, a 4x5 pinhole camera was set up looking north in southern New Zealand skies. The shutter was briefly opened each clear day in the afternoon at 4pm local time exposing the same photosensitized glass plate for the year spanning September 23, 2022 to September 19, 2023. On two days, the winter and summer solstices, the shutter was opened again 15 minutes after the main exposure and remained open until sunset to create the sun trails at the bottom and top of the curve. The equinox dates correspond to positions in the middle of the curve, not the crossover point. Of course, the curve itself is inverted compared to an analemma traced from the northern hemisphere. And while fall begins today at the Autumnal Equinox for the northern hemisphere, it's the Spring Equinox in the south.
© Ian Griffin