Parallax

:This article is about parallax, the perspective shift. For the DC comic book character see Parallax (comics).

Use in distance measurement

By observing parallax, measuring angles, and using geometry; one can determine the distance to various objects. When this is in reference to stars, the effect is known as stellar parallax. The first measurements of a stellar parallax were made by Friedrich Bessel in 1838, for the star 61 Cygni.

Related Topics:
Observing - Measuring - Angle - Geometry - Distance - Star - Friedrich Bessel - 1838 - 61 Cygni

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Distance measurement by parallax is a special case of the principle of triangulation, where one can solve for all the sides and angles in a network of triangles if, in addition to all the angles in the network, the length of only one side has been measured. Thus, the careful measurement of the length of one baseline can fix the scale of a triangulation network covering the whole nation. In parallax, the triangle is extremely long and narrow, and by measuring both its shortest side and the small top angle (the other two being close to 90 degrees), the long sides (in practice equal) can be determined.

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