Astronomy 29 



ditions suitable for obtaining the most accurate results for a given amount of work 

 expended are next discussed, and, later, the astrophysical conclusions derivable 

 from the data for the principal stars. Detailed tables of the numerical results of 

 observation conclude the volume. 



No. 43. PETERS, C. H. F. Heliographic Positions of Sun-Spots, Observed at Ham- 

 ilton College from 1860 to 1870. Edited for publication by Edwin B. 

 Frost. Quarto, xm+189 pages. Published 1907. Price $2.50. 

 The book contains the series of visual observations of the sun made by Pro- 

 fessor Peters in the decade beginning 1860. They in effect continue the routine 

 observations of the sun begun by Carrington in 1853 and ending in March 1861. 

 The tables give the position of each spot referred to the center of the disk, the 

 deduced heliographic latitude, the longitude from the node, and the heliographic 

 longitude. For each day on which Peters observed, the angular distance between 

 the prime meridians of the systems of Carrington and Peters is given. 



No. 86. PETERS, C. H. F., and E. B. KNOBEL. Ptolemy's Catalogue of Stars. 

 A Revision of the Almagest, Quarto, m+307 pages. Published 1915. 

 Price $3.50. 



The Catalogue of Stars, made by Hipparchus, transmitted by Ptolemy, and 

 commonly called Ptolemy's Almagest, is the first and most ancient known manu- 

 script which gives a description of the heavens of sufficient exactness to admit of 

 comparison with modern observations. For many centuries it was practically the 

 only record of positions of the stars which the world possessed, and it has accord- 

 ingly been a subject of many researches and investigations. 



About 1876-77, Dr. C. H. F. Peters, of Hamilton College, realizing the impor- 

 tance of verifying the exactitude of the Catalogue, begun the studies which led up 

 to the present volume, calculating, from modern observations, the longitudes and 

 latitudes of all of Ptolemy's stars, embracing every probable star near Ptolemy's 

 positions, corrected as far as possible for proper-motion. 



At almost the same time when Dr. Peters began his labors, Mr. Edward Ball 

 Knobel, of the Royal Astronomical Society of London, took up this work on nearly 

 the same lines, and for a considerable time the two continued their labors quite 

 unknown to each other; but being fortunately brought into communication, a plan 

 of cooperation in the enterprise was agreed upon. Before any progress was ef- 

 fected, however, Dr. Peters died, in 1890. But his executors placed his manu- 

 scripts and notes at the disposal of Mr. Knobel, who completed the work embodied 

 in the present publication. 



No. 250. KNOBEL, EDWARD B. Ulugh Beg's Catalogue of Stars, revised from all 

 Persian Manuscripts existing in Great Britain, with a Vocabulary of 

 Persian and Arabic Words. Quarto, 109 pages, 1 plate. Published 

 1917. Price $2.00. 



From the second century, when Ptolemy published his Almagest, to the middle 

 of the fifteenth century, there exists no catalogue of stars from original observa- 

 tions. In the year 1437 Ulugh Beg published his astronomical tables entitled "Zij 

 Ulugh Beg," which contain a catalogue of Ptolemy's stars, the positions of which 

 were re-determined from original observations made at Samercand. Ulugh Beg 

 was the last and perhaps the most distinguished representative of Arabian as- 

 tronomy, and his catalogue is of unique interest, not only on account of its 

 originality, but as it is the only record of the heavens we possess between the 

 second century and the end of the sixteenth century when Tycho Brahe made 

 his observations. 



In 1879 E. B. Knobel published a translation of the catalogue from a Persian 

 manuscript of Ulugh Beg. Some time after this the late Dr. C. H. F. Peters, of 

 Hamilton College, devoted much attention to the subject, but he confined his 

 researches mainly to the printed editions of Hyde, Tharpe, and Baily. He com- 

 puted from modern catalogues the positions of the identified stars for the epoch, 

 thus affording sound means for determining the errors of the catalogue. 



