HALLEY, Edmund. EXTRACT: 1) SOME REMARKS ON A LATE ESSAY

PARALLAX AND MAGNITUDE OF SIRIUS. ...Phil. Trans. Vol. 31, 1720-1 pp. 1-4.

Good+ extract bound in modern marbled boards and new endpapers with minimal soil and foxing

AND MEMOIR:

 2) EDMUND HALLEY 1656-1742. 

 One Memoir  ( 39 pp) in original printed wrappers

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 Sir ins and Halley examined

his results, 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. 6p. 71)