To allow more accurate astronomical observations and recordings, Shen Kuo improved the technical designs of the rotating armillary sphere, the gnomon, the clepsydra clock, and the sighting tube. Shen Kuo calibrated the standard diameter of the sighting tube's width, hence allowing the observation of the pole star indefinitely (which had shifted since the time of Zu Geng in the 5th century). With these, Shen and Wei attempted to predict the mean speeds of the planets as well as the accurate positions of the planets in their orbits.
Shen Kuo made significant enhancements to astronomical instruments, including the armillary sphere, gnomon, clepsydra clock, and sighting tube. By setting a standard width for the sighting tube, Shen Kuo allowed for continuous observation of the North Star, which had moved since Zu Geng's era in the 5th century. This led to efforts by Shen and Wei to predict planetary motion and determine their orbital positions.