Astronomy diagrams, 19th century. These relate to observing and describing the position of stars and other objects in the night sky. Across top are right, oblique and parallel spheres. Below this are diagrams showing the altitude of the 90th (nonagesimal) degree, the determination of parallax, and of declination. Below that are diagrams showing star rises relative to the Sun: cosmical, achronical, and heliacal. Across bottom are diagrams on optical phenomena affecting star observation: the apparent place, the parallax, refraction, and aberration. This page is from 'Universal Technological Dictionary' (1823) by British author George Crabb (1778-1851).