Royal Astronomical Society. 135 



and with no loss of distinctness ; and that he has succeeded in bring- 

 ing the foci of his exterior and inner surface to agree within a hun- 

 dredth of an inch. The telescope shows seven stars in and two near 

 the trapezium of Orion, and so far approaches to resolving the ne- 

 bula, that it shows " stars, the centres of nebulous clouds, scattered 

 all over the nebula." 



In confirmation of Mr. Lassell's idea that there is a ring about the 

 new planet, Mr. Hind stated that the South Villa telescope shows it 

 oblong, and that the major axis makes an angle of about 30° with 

 the meridian. 



Reduction of Tycho Brahe's Observations of the Comet of 1590, 

 with Elements deduced therefrom. By Mr. Hind. 



" The comet of 1590 was first perceived by Tycho Brahe on the 

 evening of March 5, while he was employed in observing the planet 

 Venus. It was situated near the Northern Fish, between Aries and 

 Andromeda. The diameter of the head was three minutes, and a 

 faint tail was visible, extending from 7° to 10°, and directed towards 

 the zenith at about 1^ 30"" p.m. 



" M. Pingre, in his Comctographie, tome i. p. 554, has given a series 

 of observations on this comet made by Tycho, and extracted from a 

 manuscript preserved at the Depot de la Marine in Paris. The 

 observations are detailed at considerable length in this manuscript; 

 but the table in M. Pingre's work is an abstract made by Tycho 

 himself, and I have used it as the basis of my calculations. For 

 deducing the places of the comet, we have the apparent times of 

 observation at Uraniburg, the distances from known stars, and the 

 declinations for the same times as these distances : also in most 

 cases, the comet's altitude, and frequently its azimuth from the south 

 towards the west. I have calculated the positions from the observed 

 declinations and distances, duly corrected for parallax and refraction, 

 making use of the altitudes in the preliminary computations only. 

 On two occasions the comet was observed on the meridian sub polo ; 

 in these cases I have performed the reductions in the usual manner, 

 applying refraction and parallax." 



Mr. Hind then presents tabular results of his reductions at the 

 following stages : — 



An ephemeris of the sun. 



A catalogue of the stars of comparison. 



An approximate ephemeris of the comet, for computing the effects 

 of aberration and parallax. 



The observed distances of the comet from the stars corrected for 

 refraction, aberration and parallax, with the Uraniburg mean time, 

 and the resulting right ascension and declination of comet. 



" The following longitudes and latitudes are computed from a mean 

 of each day's observations of right ascension and declination, omit- 

 ting, however, the third result for March G, and the first for March 7. 

 They arc referred to the apparent equinox of the date : 



