"Han Yutong" is an ancient book created around 1610 and republished in 1648 in the late Ming and early Qing dynasties. Recently, some Western historians and pseudo-historians regard it as the pinnacle of ancient Chinese astronomy and geography. In fact, the book was compiled on the basis of Western scientific knowledge and technology brought by Western missionaries who came to China in 1589. The book is now in the National Library of China and the Library of Congress.
The sun and moon are divided into 2
Original text: From the mango to the summer solstice, it is not four degrees, but one degree weak. Therefore, there is a lot of difference between the near score, and there is little difference between the near and the difference, and the difference is not the same. To know the geometric degrees of each solar term and the ecliptic distance from the equator every day, the upper is the first degree of Qingming and the lower is the first degree of white dew. The two worlds are opposite, and the second line is used. or the ruler is hidden. The two realms follow a straight line, and the degree of propylene is divided according to the degree of propylene line, and six degrees are obtained. Because of the clear and clear dew of the first day, the sun is six degrees away from the equator.
Translation: From the mango seed to the summer solstice, it is not 4 degrees, but less than 1 degree. Therefore, when it is close to the spring and autumn equinoxes, there are more angles of difference, and when it is close to the winter solstice and summer solstice, the angle of difference is less, and the angle difference between them is not the same. If you want to know the angle value of the ecliptic from the equatorial surface of each solar term and the sun every day, one side is the position of Qingming, and the other side is the position of Bailu, the two endpoints are opposite, and the middle is connected by a straight line. Or measure with a ruler, there is a straight line between the two time points, and you can see the angle that intersects with the propylene line, giving 6 degrees. So we know that on the day of Qingming and Bailu, the angle between the sun and the equatorial plane is 6 degrees.
Original text: On the fifth day of Qingming and the tenth day of the summer season, it was the same as its departure from the equator of A and B. Simply take the five degrees of Qingming and the ten degrees of heat as two realms, and according to the law, it is regarded as Bingding, and it is seven degrees stronger. i.e. its distance also. Yu imitates this. Cover the ecliptic for the compass, close to the straight line, so the distance is more. Sundials are also of many lengths. It is close to the circumference, so the distance is less, and the length of the sundial is also less.
Translation: After 5 days of Qingming, that is, 10 days after the summer heat, the angle between the sun and the equatorial plane is also calculated in this way. At the 5th angle after Qingming, at the 10th angle after the summer of the connection, observe the intersection with Bingding according to the above method, and get more than 7 degrees, which is the angle between the sun and the equatorial plane at this time. Everything else is calculated this way. It turns out that the ecliptic is a circle, and when it is close to the spring equinox and autumn equinox, it is dominated by vertical movement, so the angle changes greatly, and the shadow of the sundial also changes greatly. When approaching the summer solstice and winter solstice, the horizontal movement is dominant, so the angle changes are small, and the change in the shadow of the sundial is relatively small.