The simplest explanation is exposure time.

最简单解释是曝光时间。

The longer the exposure, the longer the streaks as the stars rise and set, making their circular arcs in the sky.

曝光时间越长，星星在天空中形成起落轨迹也就越长。

On film, even with long exposures, they can appear to be little more than disks.

即使是经过了长时间曝光，在胶片上它们看起来也不过是磁盘。

You will need a tripod for this type of long exposure photography!

此类长时间曝光影需要三脚架！

Often he included himself in the scenes, eyes closed because of the long exposure time his process required.

他经常把自己包括在场景中，闭着眼睛，因为需要长时间曝光。

But by using a telescope as a camera, long time exposures can be made.

但是通过使用望远镜作为相，可以进行长时间曝光。

So in order to study distant places in the universe, astronomers take long exposure images of the night sky.

因此，为了研究宇宙中遥远地方，天文学家了夜空长时间曝光图像。

We didn't try it, but somebody recommended this app as a way to take long exposure pictures with your phone.

我们没有尝试， 但有人推荐这个应用程序作为用手长时间曝光照片一种方式。

Being able to hook a camera up to a telescope and take long exposures meant being able to see fainter objects, revealing previously hidden details.

它能够将相与望远镜连接起来，且进行长时间曝光意味着能够看到更模糊物体，揭示之前隐藏细节。

It looks like a star by eye, but even binoculars reveal it to be fuzzy, and through a telescope, or with long exposure images, you get unmitigated majesty.

肉眼看它就像一颗恒星，但即使是双筒望远镜也显示出它很模糊，而通过望远镜，或长时间曝光照片，你会得到无与伦比庄严景象。

But exposure times were much quicker by the 1880s, and the introduction of the Box Brownie and other portable cameras meant that, though slow by today's digital standards, the exposure was almost instantaneous.

但到了 19 世纪 80 年代，曝光时间已经快得多了，盒子布朗尼和其他便携式相问世意味着，尽管以今天数字标准来看很慢，但曝光几乎是瞬时完成。

Instead of looking at previously-known galaxies observed from ground-based telescopes, they pointed Hubble at a relatively empty part of the sky and took hundreds of long exposures over a 10-day period, then combined them.

他们没有观察从地面望远镜观察到先前已知星系，而是将哈勃望远镜指向天空中相对空旷部分，并在 10 天内进行了数百次长时间曝光，然后将它们组合在一起。

Now, many of the beautiful shots of the night sky you've seen in this video are time lapses, made with long-exposure photos that show you a bit more than you can see with your own eyes.

现在，您在本视频中看到许多美丽夜空照片都是延时，这些照片是用长时间曝光照片， 向您展示比您亲眼看到要多一些。