Philosophical Transactions (Volume 95)

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. 1805. Excerpt: ... VI../irt Investigation of all the Changes of the variable Star in Sobieski's Shield, from five Tear's Observations, exhibiting its proportional illuminated Parts, and its Irregularities of Rotation; with Conjectures respecting unenlightened heavenly Bodies. By Edward Pigott, Esq. In a Letter to the Right Hon. Sir Joseph Banks, K. B. P.R.S. Read February 7, 1805. Bath, 180. The object of the first part of this Paper is a further investigation of the periodical and other changes of brightness of one of the variable stars I discovered in 1795, that in Sobieski's shield an account of which the Royal Society did me the honour of publishing in their Transactions. Those determinations being deduced from a few periods made near the time of discovery, must of course remain unsatisfactory, however exact the observations themselves may be, until confirmed by an additional-set, or by others made at a greater interval of time.; for which purpose I occasionally continued keeping a journal of its changes for near five years, and am happy to find that they have answered my expectation, particularly by giving us an insight into its irregularities, as will be shewn hereafter. Variable Star in Sobieski's SJiield. R. A.--270 oi-'i-S. declination 50 5& ifor the end of June, 1796. Its rotation on its axis was, in 1796, estimated at 62 days, from a mean of six observations of its greatest and least brightness. Here follow about 26 similar determinations, most of them the results of very accurate observations; and as they probably will in future be compared with others, I have examined them repeatedly with the utmost care, attending particularly to the progression of their changes. Table I. The-j-and--annexed to the magnitudes denote them to be more or less bright; the doubtful...