Our Astronomical Column

Abstract

THE TOTAL SOLAR ECLIPSE OF MAY 6.—The Compta Rendus of the sitting of the Paris Academy of Sciences on the 3rd inst. contain the reports from the observers sent by the French Government to Caroline Island in the Pacific for the observation of the recent total eclipse of the sun. The pirty was composed of M. Janssen, M. Trouvelot of the Observatory of Meudon, M. Pasteur, photographer, and an assistant, who were accompanied by Prof. Tacchini, director of the Observatory of the Collegio Romano, and Herr Palisa of the Obsservatory of Vienna, the discoverer of a large number of minor planets. One of the main objects of the expedition was a search for so-called intra-Mercurial planets, and it is to the observations made in this direction that we shall refer here. Herr Palisa and M. Trouvelot were especially occupied with this work. The former had a telescope of 6 inches aperture, with short focus and large field, equatorially mounted. M. Trouvelot had two telescopes, one of 3 inches aperture, with large field, reticule, and interior circle of position, and one of 6 inches aperture giving a high magnifying power. The 3-inch telescope formed a sweeping instrument with a field of about 4½ degrees diameter, for the exploration of the circumsolar region. Both telescopes were on a parallactic mounting, and in order to secure rapid record of positions and dispense with the readings, which cause the loss of valuible time, M. Janssen had caused what he terms “tracelets de microscope ” to be applied to the circles of right ascension and declination. Each of these, placed in the hands of an assistant, allowed of there being made, on the direction of the observer, a fine stroke across the divided circle and its vernier, so that subsequently, with the aid of this very precise indication, the instrument could be replaced in the position of the observation and the necessary readings made at leisure. It was arranged that MM. Palisa and Trouvelot should divide the work, each attending specially to one side of the sun. The Vienna astronomer's instrument, properly, as it seems, a comet-seeker, by Merz, had a magnifying power of 13, giving a field of 3°. With this, on totality taking place, he commenced his search, starting from the sun towards Saturn, at first on the south, and when he did not thus find stars he returned to the sun, and swept more to the north. In this way he recognised nine stars, all which are identified in the Bonn Durchmusterung. We give the list of stars, correcting two misprints in the Comptes Rendus (14°,355 should be 16°,355, and for 20°,542 we should read 20°,543), and appending the positions of the stars for the Bonn epoch 1855.0: thus, with the sun's place reduced to the same epoch, the relative positions of the stars with respect to his centre will be readily seen:—