半天球被黄道，天赤道或地平圈分成两半的天球的一半…
Either half of the celestial sphere as divided by the ecliptic, the celestial equator, or the horizon.
这对查看一个精确的天体是否超出当前的地平圈是很有用的，而且可以知道要看到这个天体应朝哪一方向看。
This is very useful for seeing whether or not a particular object is currently above the horizon, and for knowing which direction to look in order to see the object.
当然一个低成本但不是相当直接的方法是，夏至时去北极圈旅行，花一晚上的时间(能在热水缸里最好)看地平线以上的太阳圈。
For a cheaper, although not quite as direct, method, journey north of the Arctic circle around the summer solstice and spend a night (ideally in a hot tub) watching the sun circle above the horizon.
全帧鱼眼镜头拍到了地平线上所有东西，包括边缘一圈被灯光照亮的地景，正在脑袋上方的天顶。
The full fisheye frame shows everything above the horizon, including a lamp-illuminated landscape around the edges, and the zenith of the sky directly overhead.
地平经圈是指当地天球上的方向的天球大圆。
The veritical circle means the big circle of a heaven sphere over the local direction of a heaven sphere.
地平经圈是指当地天球上的方向的天球大圆。
The veritical circle means the big circle of a heaven sphere over the local direction of a heaven sphere.
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