The Observatory Volume 24, Nos. 300-312 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1901 Excerpt: ... with this question. It is pointed out that there are four factors which will have to be allowed for in determining the brightness at any moment, viz.: --(1) velocity of light, (2) distance of Sun and Earth, (3) phase, (4) direction of axis of rotation. The last can only be determined by a long series of observations extending over a large angle. As a first rough approximation the equator of Eros is assumed to be parallel to ours, and the consequences of this assumption are deduced. The photographs taken in 1893, 1894, 1896 have been examined for light-variation. Some of the plates had a long exposure (ih or more), and Eros had trailed considerably; this would enable any variation in light during the exposure to be detected (such variation might, however, arise from atmospheric causes). The range seems to have been very small in 1893 and January 1894. A maximum is indicated cn Julian day 2412865-622 (February 5, 1894). In 1896 plates show larger variations of light. In June of that year the variation seems to have been at least 1 mag. Maxima are given at Julian dates 2413656-890, 2413715-702, 2413740-803, Vol. xxiv. y 2413741561. The photometric observations made in 1898 give the means of investigating the variation at that date. A discussion of these is promised in a future Circular. A. C. D. G. The Sun-spot Group Of Mat Io-jcne I.--Since November 27, 1900, the solar surface has been almost entirely clear of spots and faculae, the only noticeable group of spots being one composed of small members which was observed from March 3 to March 11. But after a period of almost exactly six months quiescence, the solar faces displayed a renewal of at least partial activity in the shape of a fine group of spots, visible to the unaided eye, which crossed the visible di..