The Grating form of the Micrometer for the Low-Latitude Meridian Circle and the Principle of the Measurement

According to the demand of the absolute measurement by the Low-latitude meridian circle, for problems of the measurement of the zenith distance in the direction of the prime vertical using the slant silts, the previous grating form is improved based on the former micrometer scheme. The new grating form and the measurement principle are introduced in the paper. The influence of the degree of the slant of slits for the measurements and the method of determination of the tilt of slits are also discussed.