the distance from one celestial body to another, measured in astronomical units, light-years, or p-rs-cs.
- 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.
- Astronomical refraction
- 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.