2019 October 14
Andromeda before Photoshop
Image Credit: Kees Scherer
Explanation: What does the Andromeda galaxy really look like? The featured image shows how our Milky Way Galaxy’s closest major galactic neighbor really appears in a long exposure through Earth’s busy skies and with a digital camera that introduces normal imperfections. The picture is a stack of 223 images, each a 300 second exposure, taken from a garden observatory in Portugal over the past year. Obvious image deficiencies include bright parallel airplane trails, long and continuous satellite trails, short cosmic ray streaks, and bad pixels. These imperfections were actually not removed with Photoshop specifically, but rather greatly reduced with a series of computer software packages that included Astro Pixel Processor, DeepSkyStacker, and PixInsight. All of this work was done not to deceive you with a digital fantasy that has little to do with the real likeness of the Andromeda galaxy (M31), but to minimize Earthly artifacts that have nothing to do with the distant galaxy and so better recreate what M31 really does look like.
影像来源: Kees Scherer
说明：仙女星系长什么样子？仙女星系是距银河系最近的大型星系。这幅长曝光影像是由数码相机拍摄的223张照片（每张曝光300秒）叠加而成的。拍摄地点位于葡萄牙的一座天文台。它展现了仙女星系在过去一年中在忙碌地球天空的样子。明显的影像缺陷包括明亮的（飞机）飞行轨迹、连续的卫星轨迹、短小的宇宙射线条纹、以及坏点。这些缺陷并没有使用photoshop来消除，但可以通过一系列诸如Astro Pixel Processor、DeepSkyStacker、PixInsight的计算机软件来大幅弱化其影响。这些后期工作并不是利用数字手段给你看一张假的、跟真实星系毫无关联的“人造图”，而是为了消除一些会影响到仙女星系的人造物，使得这张影像可以更好的展示（M31）仙女星系的真实面貌。