A Popular History of Astronomy During the Nineteenth Century / Fourth Edition

by Agnes M. Clerke

[71] Astronomische Nachrichten, Nos. 365-366. It should be explained that what is called the "annual parallax" of a star is only half its apparent displacement. In other words, it is the angle subtended at the distance of that particular star by the radius of the earth's orbit.

[72] Astr. Nach., Nos. 401-402.

[73] Sir R. Ball's measurements at Dunsink gave to 61 Cygni a parallax of 0·47′; Professor Pritchard obtained, by photographic determinations, one of 0·43′.

[74] Additamentum in Mensuras Micrometricas, p. 28.

[75] Elkin's corrected result (in 1897) for the parallax of Vega is 0·082′.

[76] Mem. Roy. Astr. Soc., vol. xi., p. 61.

[77] That numbered 21,185 in Lalande's Hist. Cél., found by Argelander to have a proper motion of 4·734′, and by Winnecke a parallax of O·511′. Month. Not., vol. xviii., p. 289.

[78] Fund. Astr., p. 309.

[79] Mém. Prés. à l'Ac. de St. Pétersb., t. iii.

[80] Phil. Trans., vol. cxxxvii., p. 79.