A treatise of astronomy, [electronic resource] : Wherein the diurnal motions of the heavenly bodies, and the annual motion of the sun, and the sun's various distances from the Earth, together with the inequabilities of the sun's motions throughout the year, are accounted for according to the ptolemaick, semi-tychonick and Copernican systems; and particularly the third motion of the earth, and the application of it in accounting for the sun's apparent motions in the Copernican system, is set forth by a machine described in its proper place: Wherein also rules, founded upon known optical principles, are deliver'd, for determining the angles of refraction of the sun, moon, and stars at all altitudes above the sensible horizon; and wherein the sun's diurnal parallax is determined by demonstrations, founded upon most authentick observations. By John Shuttleworth, A.M. prebendary of Sarum.