Astrolabe, Prism, Fixed (Historical)
Wednesday, August 30, 2006
An Astrolabe has been designed and developed consists of a Prism, a contained mercury pool (to form an artificial horizon), a low power visual telescope, leveling capabilities, a magnetic compass with an azimuth circle and an adjustable light source (battery operated). The Astrolabe has a Fixed Prism for measuring a fixed altitude of approximately 45 degree.
A light beam from a star enters the Fixed Prism (refracted) and then is reflected from the contained mercury pool. The star light beam is reflected back into the same Fixed Prism and is then refracted again by the Fixed Prism. Both rays in the Fixed Prism are refracted again in order to have the star light beams travel down a telescope barrel toward the eyepiece.
The fixed altitude is used to minimize errors due to atmospheric refraction variations. Various observations are measured to provide individual position to create a single line of points. A number of observations are taken in order to decrease the random error of the individual position readings. A number of individual positions of the single line establish the center of the positions of each single line. An error can be caused by the slight variations in the earth’s gravity, affecting the vertical reference (zenith). Any vertical reference variation affects the contained mercury pool reflection angle (the artificial horizon).
Source: Various Publications Reference: None Available
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posted by JD52 @ 7:57 PM,
