Double-image object glass micrometer by Dollond, engraved Dollond, London with mahogany case. Double-image object glass micrometer by Dollond 1754-1770
One of nineteen photographs taken at the Royal Observatory, Cape of Good Hope, South Africa, showing the dome and building for the 7-inch Heliometer by Messrs Repsold and Sons, Hamburg. Used widely by Sir David Gill to make stellar parallax measurements from 1887 onwards. One of nineteen photographs taken at the Royal Observatory 1909