Astronomical frame of reference
a frame of reference in which the sun or center of m-ss of the universe is fixed and which does not rotate with respect to the fixed stars.
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- Astronomical refraction
(def 3).
- Astronomical telescope
a telescope having an objective with a long focal length and an eyepiece with a short focal length, usually used for observing celestial bodies. historical examples kepler, in 1611, made the first astronomical telescope with two concave gl-sses. astronomical myths john f. blake one word about the inversion of objects by the astronomical telescope. half-hours […]
- Astronomical triangle
the spherical triangle formed by the great circles connecting a celestial object, the zenith, and the celestial pole.
- Astronomical twilight
either of two periods of partial darkness, after sunset or before sunrise, when the center of the sun is more than 6° but less than 18° below the horizon.
- Astronomical unit
a unit of length, equal to the mean distance of the earth from the sun: approximately 93 million miles (150 million km). abbreviation: au. historical examples that was one astronomical unit, equal to about ninety-three million miles, the distance from earth to the sun. rip foster in ride the gray planet harold leland goodwin in […]