OCCULTATIONS. Elements for facilitating the Calculation of Occultations which may be visible in the United States in 1851. A Table showing the Illuminated Portions of the Disks of Venus and Mars. THE numbers in this table are the versed sines of that portion of the disks which, to an observer on the Earth, will appear to be illuminated, the apparent diameters of the planets at the time being considered as unity. To a spectator on the Earth, Venus appears most brilliant when her elongation is about 40°, and she is approaching her inferior conjunction, or receding from it; in the latter of which positions she will be on the 21st of January. Mars is most brilliant about the time of his opposition to the Sun, being then also nearest the Earth; in which position he will not be this a denotes the outer semi-transverse axis of the outer ring. "outer semi-conjugate axis of the outer ring, positive when the The inner semi-transverse axis of the inner ring is two thirds of a, diminished by 0′′.07. The inner semi-conjugate axis of the inner ring is two thirds of b. The Opposition will take place on the 24th of October. |