German instrument maker, born at Wremen in Hanover, and became an engineer and afterwards chief of the fire brigade in Hamburg, where he started business as an instrument maker early in the 19th century. He was killed by the fall of a wall during a fire at Hamburg on the 14th of January 1830. The business was continued by his sons Georg (1804–1884) and Adolf (1806–1871), and his grandsons Johann Adolf and Oskar Philipp.
J. G. Repsold introduced essential improvements in the meridian circles by substituting microscopes (on Jesse Ramsden’s plan) for the verniers to read the circles, and by making the various parts perfectly symmetrical. For a number of years the firm furnished meridian circles to the observatories at Hamburg, Königsberg, Pulkova, &c.; later on its activity declined, while Pistor and Martins of Berlin rose to eminence. But after the discontinuance of this firm that of Repsold again came to the front, not only in the construction of transit circles, but also of equatorial mountings and more especially of heliometers.
