On the transit of Mercury over the sun's disc, November 5th, 1868

Abstract

Introduction - I lay on tlie table a diagram in whicTi is embodied the elements, and a full explanation, of tbe transit of Mercury, with the true path of the planet over the sun's disc on the 5th of November, 1868. The observations were male with a five foot equatorially mounted achromatic telescope. Other observations were also made at the time, and near the same place, with a small Oregorian reflector. The day was fine, and the passage of the planet over the sun's disc was observed as a well-defined round black spot. When the true limb of the planet reached the true limb of the sun, the light being cut off, a fine dark ligament appeared to connect the limb of the planet and the sun, showing the true time at first contact. The Hobart Town time of transit was computed from the Nautical Almanac ; the observations made with a half second chronometer, and when compared with the normal clock it was found to be remarkably close, I scarcely think one second in error.