CAS AS 101 Lecture Notes - Lecture 5: Angular Diameter, Angular Distance, Celestial Sphere
30 Jan 2018
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Document Summary
No, because of obscuration by dust and gas in mw. Celestial sphere useful for thinking about appearance of universe from earth. But that"s not what we actually see when we go outside and look at the sky. The earth itself blocks the rest of the sphere. Local sky- as seen from wherever you are standing. An object"s altitude (above horizon) and direction (along horizon) specify its location in local sky. Horizon boundary between earth and sky. Meridian: imaginary half circle stretching from horizon due s to n. No, because our depth perception breaks down at such distances. Angular size: angle it appears to span in our field of view. Angular distance: angle that appears to separate a pair of objects. Angular size = physical size x 360 degrees / 2pi distance. Angular size / 360 degrees = physical size / circumference. Physical size(diameter) = angular size / 360 degrees * 2pi * distance.
