London: The Royal Society, 1780. 1st Edition. BOUND FULL VOLUME (Parts I & II): 1ST EDITIONS OF WILLIAM HERSCHEL’S SCIENTIFIC DEBUT, HIS 1ST TWO PUBLISHED PAPERS -- BOTH ASTRONOMICAL – WITH HIS FIRST PUBLISHED DESCRIPTION OF HIS NEWLY HANDBUILT TELESCOPE.
“The first paper dealt with a periodical star [Collo Ceti], the second with the height of the mountains of the moon; in both papers, Herschel called attention to the remarkable capabilities of his telescope” (McCormmach, Weighing the World, 334). In the second paper, he wrote: “I believe that for distinctness of vision this instrument is perhaps equal to any that was ever made” (Herschel, PT 70, 1780). The second paper is accompanied by a large fold-out copperplate illustrating the mathematical calculations behind his lunar measurements.
“In 1773 Herschel began grinding mirrors for telescopes and in 1774 he began keeping a journal of his observations. Bennett [primary historian of Herschel’s telescopes] states: ‘It was the beginning of a unique career in astronomy; original speculations on the nature of stellar objects and the construction of the heavens would be paralleled by equally bold designs for improving telescopes” (Cunningham, The Scientific Legacy of William Herschel, 249).
IN THE FIRST PAPER, Herschel wrote that Collo Ceti, the “remarkable star” he observed “was first observed by David Fabricus, the 13th of August, 1596, who called it the ‘stella mire,’ or ‘wonderful star’ (ibid). In this paper, Herschel wrote that “he magnified the star as much as 449 times, finding it ‘very full and round in the telescope,’” (Herschel, PT 70, 1780). From this time on, Herschel’s telescopes and the claims he made for their magnification and their distinct images greatly interested British astronomers” (McCormmach).
THE SECOND PAPER, “Astronomical Observations Relating to the Mountains of the Moon,” also includes the 5 page addition of “The Following Additional Memoranda of the Manner in Which Mr. Herschel Made his Observations are Taken From a Letter of His to the Rev. Dr. Maskelyne, Astronomer Royal”.
Both papers, as said, illuminate the power of Herschel’s telescope. As he sought to describe the means by which he made his lunar mountain calculations, Herschel detailed some of his telescope’s specifications: “The telescope I used was a Newtonian reflector of six feet eight inches focal length, to which a micrometer was adapted consisting of two parallel hairs, one of which was moveable by means of a fine screw. The value of the parts shewn by the index was determined by a trigonometrical observation of a known object at a known distance, and was verified by several trials. The power I always used, except when another is mentioned, was 222 times, also determined by experiment, which I have often found to differ somewhat from theory, on account of some little errors in the data, hardly to be avoided. The moon having sufficient light, I used no more aperture of the object speculum than four inches; and, I believe, that for distinctness of vision this instrument is perhaps equal to any that was ever made” (Herschel, PT 70, 1780).
With this instrument and “In the winter of 1779-1780 [prior to publication] Herschel calculated the height of several lunar mountains by adapting the method of Galileo and others. This involved measuring the angular distances between the mountain and the boundary of the illuminated part of the moon, at the time when the sun’s rays first reached the peak of the mountain. To make the delicate measurements Herschel used a bifilar micrometer, which he calibrated by applying it to known terrestrial objects. He concluded that the height of lunar mountains had been exaggerated and that ‘the generality do not exceed half a mile in their perpendicular elevation’” (DSB VI, 333-334). Item #1257
CONDITION & DETAILS: 4to. 15 copperplates. 583pp. No library markings at all. Handsomely rebound in calf; 5 raised spine bands; red & black spine labels. Original wide margins. Bright & clean throughout. Near fine.