Edmund Halley, SOME REMARKS ON A LATE ESSAY OF MR. CASSINI, WHEREIN HE PROPOSES TO FIND, BY OBSERVATION, THE PARALLAX AND MAGNITUDE OF SIRIUS

.Published in: 1) Phil. Trans. Vol. 31, 1720-1 pp. 1-4 A Very Good+ extract bound in marbled boards and new endpapers with minimal soil and foxing pages, scuffs and edge wear covers.Not sure about the age of the hard boards; but they are not real new , but are unscuffed and un dinged

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2) Memoirs of the British Astronomical Association,Vol.37,No. 3, November 1956. Paperback .At this time there was great interest in trying to determine stellar parallax which, if the Copernican view were correct (and it was the generally accepted picture) should be observable for the nearer stars as the Earth traveled in its orbit round the Sun. Cassini in Paris claimed to have successfully observed such a parallax for Sirius and Halley examined hisresults, finding that no parallax had in fact been observed; in doing so he made a thorough examination of the accuracy attainable by transit observations.(Edmond Halley 1656-1742: Papers to Commemorate the Tercentenary of His Birth [1956]). The limitation of precise measurement in Halley's time also prevented the successful determination of even one stellar distance. Claims to have achieved this were made nonetheless, notably in 1714 by Jacques Cassini, who believed he had obtained an annual parallax for Sirius. In 1720 Halley analyzed this claim, showed that it could not be upheld, and made suggestions for observations which he thought might be successful. (DSB Vol. 6 p. 71

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