Astronomy Picture of the Day——时长越来越长的白昼
The Longer Days
Image Credit & Copyright: GianlucaBelgrado
Explanation: This persistent six month longexposure compresses the time from solstice to solstice (December 21, 2018 toJune 16, 2019) into a single point of view. Dubbed a solargraph, theunconventional picture was recorded with a tall, tube-shaped pinhole camerausing a piece of photographic paper. Fixed to a single spot at Casarano, Italyfor the entire exposure, the simple camera continuously records the Sun's dailypath as a glowing trail burned into the photosensitive paper. Breaks and gapsin the trails are caused by cloud cover. At the end of the exposure, the paperwas scanned to create the digital image. Of course, starting in December theSun trails peak lower in the sky, near the northern hemisphere's wintersolstice. The trails climb higher as the days grow longer and the June 21stsummer solstice approaches.
时长越来越长的白昼
这幅连续拍摄了六个月的长曝光影像将冬至到夏至（2018年12月21日至2019年6月16日）的时间压缩成一幅。这幅不同寻常的照片被称为日轨图，它是由一架高大的管状针孔相机拍摄的，它使用了一个简单的技巧，就是一直使用一张相纸。这台简易的相机被固定在意大利卡萨拉诺的同一单一地点上，并连续记录太阳的日常路径，就像一道炽热的轨迹在感光纸上燃烧一样。这些轨迹上的中断和缺口是由云层造成的。在曝光结束时，我们对纸张进行扫描从而构建出这幅数字影像。当然，从12月开始，太阳轨迹会在临近北半球冬至时落在天空中的较低处。随着白昼时长的增加和6月21日夏至的来临，太阳轨迹会越升越高。
参考文献：
https://apod.nasa.gov/apod/image/1906/solargraphBelgrado.jpg
近期文章：
Astronomy Picture of the Day——夜光云、倒影与剪影