视直径即视大小，也就是肉眼看见的物体的视角。单位为度、分、秒。天文学中可通过视直径和星体的实际直径来计算星体的距离。
不管怎样，月亮的视直径总是在0.5度左右。
Either way, the angular diameter of the Moon is always about 0.5 degrees.
卧式贮罐视罐体长度决定设置鞍式支座的数量，一般鞍座的间距等于或小于罐体直径的1.5倍。
The number of saddle supports will be determined by the length of the horizontal storage tanks; in general the distance between the saddles is equal or less than 1.5times of the tanks 'diameters.
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