天文精密日時計の製作 Manufacture of Astronomical Precise Sundial
Until now, the sundial has hardly been made especially in pursuit of accuracy and function. The typical sundial indicating the time at the angle of the shadow of edge lines has no structure to correct the atmospheric refraction. On the other hand, the sundial using a two-dimensional dial for reading at the center position of the shadow of a sphere provides a precise design so that not only the time difference by equation of time and longitude but also atmospheric refraction can be corrected. This"astronomical precise sundial"uses a two-dimensional dial, and it is a precise and highly functional sundial designed and manufactured in pursuit of the possiblity of the sundial from the viewpoint of astronomers. As the functions of this sundial, the local sidereal time can be directly read for the first time in the world, and the various information such as the sunrise and sunset times and the azimuth and altitude of the sun can be obtained.
日本時計学会誌 151(0), 1-10, 1994