A pass of a satellite occurs whenever it rises above the observer's horizon; a "visible pass" occurs when all three of the above conditions are satisfied, so the sunlit satellite is seen against a dark sky - this will generally occur either shortly after sunset, or shortly before sunrise. In most cases, the satellite will rise in the west, cross the observer's meridian, and set in the east, although satellites in a polar orbit can rise or set in any part of the sky! Very often the satellite won't be visible for the whole of its passage across the sky, but will either emerge from or enter into the Earth's shadow while above the horizon.
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Web sites now exist that can help you identify unknown "drifters" and even predict the time of the next pass of the ISS visible from your location.
这个网站可以帮助你识别不明的漂移物,以及预测你所在的地方下一次可以看到国际空间站掠过的准确时间。
Remember that the AST classes aren't visible outside of this package at all and that clients will (eventually) simply pass in a String representation of the expression they want evaluated.
要记住 AST 类在包外是不可见的, 还有就是客户机(最终)只会传入它们想求值的表达式的一个字符串表示。
When rendered, the image looks like this. You can notice that those four lights make the scene look flat. Later I'll use an ambient occlusion pass to make small details more visible.
当渲染后,你发现四盏平行光使场景看上去很平,等一会我使用一个环境光阻塞效果来加一点细节。
So as a first pass, the Evening Star is the first star that's visible and the Morning Star is the last star that's visible at the right times of the year.
在最初,昏星是能看到的,第一颗星,而晨星,是最后一颗,当然是在每年的特定时段
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