Astronomical chronograph. Astronomer and his assistant working with chronographic equipment. This was the name for the equipment used to record measurements over time, using mechanical or electrical methods to trigger the recordings. The apparatus would involve a clock, as well as a recording mechanism. A famous example was the Great Galvanic Chronographic Apparatus of the Royal Observatory, Greenwich, constructed by Edward Dent and used to measure and record astronomical observations. Artwork published in the 1891 edition of The Midnight Sky, by the British astronomer Edwin Dunkin.