本帖最后由 gohomeman1 于 2010-3-25 22:16 编辑
15 March 2010：Solargraphy at Sunny Paranal
2010.3.15：阳光充足的帕拉纳尔山上的太阳移动影像
Solargraphy, the art of using a single long-term exposure with a pinhole camera to photograph the movement of the Sun over the course of many weeks, helps show just why Cerro Paranal in northern Chile makes the perfect home for ESO’s Very Large Telescope (VLT). The pinhole camera, made from a small film canister and a piece of photographic paper, was placed on the roof of the VLT control building by Gerd Hüdepohl from 15 October to 26 December 2009, covering spring in the southern hemisphere. The white streaks across the top of the image are the Sun’s progress across the sky over the whole period. When clouds come between the Sun and the camera, breaks in the streak form but, as can be seen here, no clouds obscured the sky during the entire exposure. Perfect astronomy weather in other words! The VLT’s Unit Telescope 1 is visible as a ghostly outline at the bottom of the picture.
太阳移动影像是采用针孔照相机、长时间曝光方式拍摄的每天太阳移动的轨迹，本图累积曝光了数周，显示了帕拉纳尔山极好的空气宁静度，说明ESO选择智利北部的此山作为甚大望远镜（VLT）之家是非常正确的。拍摄本图的针孔照相机就是一个有小孔的胶卷盒，里面放着照相纸，由Gerd Hüdepohl安放在VLT控制室屋顶，曝光时间从2009.10.15~12.26，覆盖了南半球的春天时段。换句话说，整个春天都是天文观测的好时光！图中下方模糊的建筑就是1#VLT。
The idea for creating the solargraphs at ESO’s telescopes came from Bob Fosbury, an astronomer based at ESO headquarters in Germany, after learning about the technique from Finnish artist Tarja Trygg. Trygg provided cameras — basically cylinders with a hole and a piece of unexposed photographic paper mounted along the inner wall — and Fosbury had Observatory director Andreas Kaufer deliver the cameras, known as “cans”, to ESO’s observatory sites in Chile and then collect them four months later for final processing by Trygg. “It’s an absolutely unique image,” Fosbury says. “I’ve never seen unbroken solar trails like this before in images exposed from all around the world.”
德国ESO总部的天文学家Bob Fosbury 在学习了芬兰艺术大师Tarja Trygg 的手法后，提出在ESO的望远镜所在地拍摄太阳移动影像的创意。Trygg提供相机——本质上就是个“可乐罐”，有个洞，内壁则是整张未曝光的相纸；而Fosbury则把相机（“可乐罐”）交给ESO的天文台主管Andreas Kaufer，在Trygg完成相机4个月后，它最终安放在智利的天文台上。Fosbury说：“这绝对是独一无二的图像！在此之前，我还从没见过完整拍下太阳在天空中完整路径的照片呢。”
The colours appearing in this pinhole camera picture are not related to the actual colours of the scene. The colour comes from the appearance of finely divided metallic silver growing on silver halide grains. With solargraphic images, the photographic paper is not developed but simply scanned with a normal colour scanner after exposure and then “inverted” — switched from negative to positive — in the computer. This reveals the latent image, which in a normal photograph consists of around ten silver atoms per billion atoms of silver halide grain and is usually invisible. On continued exposure however, the latent image clumps grow so that the first visible signs of an image are yellowish, which then darkens to sepia and finally to a maroonish-brown hue as the particle size increases. Eventually the maximum exposure produces a slate grey shade.
针孔照相机中的图像颜色貌似与现实相左，其实颜色来自从溴化银微粒中析出的金属银。太阳移动影像在曝光后，并没有进行复杂的彩色成像程序，它只是简单的进行了一次“逆转”扫描——由计算机把底片转为正像。通常当10亿个溴化银分子中有10个银原子析出就能形成潜像；随着曝光继续，潜像中银原子逐渐增长，并最终形成可见的痕迹：从微黄到棕黑到maroonish（？）褐色。银原子沉积最多的区域呈现鼠灰色。
In this solargraph you can see curved reflections of the solar image forming a “caustic” about one third of the way across the image. Such effects are common in solargraphs when the Sun is near the edge of the field and are created by reflections from the white paper where the photographic paper departs from a circle and flattens near its ends.
在这张太阳移动影像图中，我们可以看到图像的1/3是太阳光反射形成的“焦散曲线”。这种效应在此类图像中很常见，当太阳移动到相机视场的边缘时，来自白纸的反光就会产生这种效应；当相纸快用尽的平直段，也会有此类效应。 |
显身卡
