After long-term astronomical observation, Gander and Shi Shen each wrote an astronomical work. Later generations called these two works "Shi Gan Xing Jing", which is the earliest astronomical work in the world.
The book records the names of 800 stars, among which the position of 12 1 star has been determined, which is the earliest catalog in the world. The book also records the operation of the five planets, such as wood, fire, earth, gold and water, and points out their infestation laws.
He and Shi Shenfu and others established different naming systems for all-star stars. The method is to give the name and number of a star in turn, and then point out the relative position of the star and another star, thus giving a qualitative description of the distribution and position of stars throughout the day.
During the Three Kingdoms period, Chen Zhuo summed up Gander, Shishenfu and Wuxing, and got the classic 283-star official system of ancient China 1464, in which Gander chose 146 (including 28 nights). It can be seen that Gander's division and naming of all the stars have a great influence on future generations. There are signs that Gander also quantitatively measured the positions of several stars, but unfortunately, most of the results were lost.
Gander has made long-term observation and quantitative research on planetary motion. He discovered the retrograde phenomena of Mars and Venus. He pointed out that "going back or hooking" and "hooking again is one third" and described the trajectory of the planet from anterograde to retrograde to anterograde as a "one third" shape.
Gander also established the concept of planetary rendezvous period (the interval between two consecutive mornings to see the East), and measured the rendezvous periods of Jupiter, Venus and Mercury as 400 days (398.9 days), 587.25 days (583.9 days) and 136 days (1 15.9 days) respectively. He also gave the number of days that Jupiter and Mercury saw and set in a rendezvous period, and the number of days that Venus went forward, backward and set in a rendezvous period, and pointed out that the number of days that Venus went forward, backward and set in different rendezvous periods may change within a certain range. Although these quantitative descriptions of Gander are still very rough, they laid the foundation for the traditional calculation method of planetary position in later generations.
According to "If there is a little red star attached to its side" quoted by Gander when talking about Jupiter in the Kaiyuan Classic of Tang Dynasty, some people think that Gander had observed Jupiter's brightest satellite Europa with naked eyes nearly two thousand years before Galileo. Gander wrote a monograph on Jupiter, Chronicle of Stars, which was a famous person who carefully observed and studied Jupiter at that time.
Gander's activity time should be in the middle of 4th century BC, in the era of Qi Weiwang and Wang Xuan. At that time, hundred schools of thought and Qi Xin joined forces and gathered under Qi State to launch a hundred schools of thought, and Gander was the representative of a hundred schools of thought.
Shi Gan Xing Jing is one of the earliest astronomical works in the world, written by Gander and Shi Shen. Shi Shen, wei ren, later than Gander, wrote "The Map of Fainting Heaven", which is the representative work of the thought of fainting heaven in the pre-Qin period. Gander is the author of eight volumes of Tian Wen Star Wars and one volume of Gansi Qifa. Both of them were outstanding astronomers in the pre-Qin period, so people called them both.
Ganzi method is Ganzi 47 method. Why is it called "four-seven method"? The "47 method" is a chronological method in astronomy. The so-called "four-seven method" is a method of measuring the motion orientation of the sun, the moon and other celestial bodies with 28 stars. The twenty-eight huts listed in Shi Gan's Four and Seven Laws can only be understood from other historical records because the original book is lost. According to the records in Kaiyuan's Accompanying Stack, Historical Records, Tian Guan Shu and Law Book, the orientation and star name of the 28 pavilions are the Seven Pavilions of the East: Jiao, Kang, Di, Fang, Xin, Wei and Ji; Seven nights in the north: fighting, cows, women, emptiness, danger, rooms, walls; Western Seven Stars: Kui, Lou, Stomach, Chang, Bi, Gou and Shen; Seven southern stars: well, ghost, willow, star, Zhang, wing and bird.