梦溪笔谈

我在编校昭文馆书籍时，曾参与详细审定浑天仪的工作。

When I edited and proofread the books in the institute for the glorification of Literature, I took part in scrutinizing the armillary sphere.

官长问我：“二十八宿之间的距离，多的有三十三度，少的只有一度。如此不均匀，为什么呢？”

The ruler asked me, “why the distances between the 28 stellar lodges are so uneven, as large as thirty-three degrees and as small as only one degree?”

我回答说：天体运行本无所谓“度”，是推算历法者无从运用他们的推算数据，才按太阳每年所行经的轨道，划分周天为三百六十五度多一点。

I answered, “There is no degree for the celestial movements. But people who calculate the callendar have no way to apply their calculated data, so the sidereal revolution is divided into a little more than 365 degrees according to the orbits the sun travels every year.

（太阳运行平均三百六十五天多一点为一个周期，所以周天也以太阳每天所行的距离为一度。）

The average cycle of the movement of the sun is a little more than 365 days, so in term of the sidereal revolution, the distance the sun moves every day is one degree.

既要划分周天，必然要有参照物作标记，然后才可以测量和运算，于是便以正好在黄道附近可以作为分度界点的星体为标志。

For the division of the sidereal revolution,there must be reference object to mark,and then it can be measured and calculated.So the star near the ecliptic,which can be regarded as the dividing point,becomes the mark.

太阳沿着黄道运行一周，可以当做分度界点的星体也不过二十八宿的代表星官而已，

The sun orbits the ecliptic,and the star which can be regarded as the dividing point is only the representative asterism of the 28 stellar lodges.

（分度的界线就像撑伞的弓形架条，“当度”指正好处在伞弓上。所以车盖有二十八条弓架，用以象征二十八宿。这也就是我在《浑仪奏议》中所说的“度是不可见的，可见的是星”。日、月、五星所经之处都有许多可见的星，而正好可以作为分度界点的大概有二十八宿的星官，且称之为“舍”，“舍”就是用来提领分度和产生度数的。）现在所称的距度星就是这种代表星。并非是天文学家不想均匀划分，而是在太阳所行经的黄道上，可以作为分度标志的星体只有这些罢了。

予编校昭文书时，预详定浑天仪。官长问余：“二十八宿，多者三十三度，少者止一度，如此不均，何也？”予对曰：“天事本无度，推历者无以寓其数，乃以日所分天为三百六十五度有奇。日平行三百六十五日有馀而一期天，故以一日为一度。既分之，必有物记之，然后可窥而数，于是以当度之星记之。循黄道，日之所行一期，当者止二十八宿星而已。

（沈括：梦溪笔谈）

梦溪笔谈 翻译