Optical instrument, for measurement of astronomical photograph plates, metal / glass used at Sydney Observatory, made by H Yeates, Melbourne, Victoria, Australia, 1940-1949.
Plate measuring machine used to measure astrographic plates. The machine consists of a steel frame with a three legged base that supports a two armed bracket. The lower arm supports a plate frame which has two scales at right angles to one another, marked in centimetres. A hole in the plate frame allows light to be reflected from a concave mirror below the frame through a section of the plate and up into the microscope. The upper arm of the bracket supports a microscope with micrometer on a rotating circle, which is marked from 0-360 degrees. A rotating vernier scale is at one end of the microscope support. A black painted eye shield rotates around the microscope support. Final measurements are taken through the micrometer that can be rotated in any direction.