atmospheric refraction
The shift in apparent direction of a celestial object caused by the refraction (bending of light rays) as they pass through Earth's atmosphere.
atmospheric refraction: The change in direction of a ray of light as it passes from space into the atmosphere. This causes celestial objects to appear to be in a location different from their actual ones.
atmospheric refraction: see refraction.
autumnal {fall} equinox: see equinoxes.
axis (of the Earth's rotation) or polar axis: the line running through the true North and South poles about which the Earth rotates.
atmospheric refraction - The bending or refraction of light rays from celestial objects by the earth's atmosphere.
The phenomenon of atmospheric refraction makes it possible to observe the Sun (and hence a solar eclipse) even when it is slightly below the horizon.
angels (radar) (NASA Thesaurus) Echos of false radar targets caused by atmospheric inhomogeneity, atmospheric refraction, insects, birds, or unknown phenomena.
This path is curved slightly by atmospheric refraction. tangent ogive An ogive whose circular-arc contours have their centers on a line normal to the axis at the base of the ogive, ...
That will be subject to the whim of our old friend atmospheric refraction. Recall that atmospheric refraction bends the image of the Sun an average of 34' of arc.
*Due to the atmospheric refraction the Sun, when near the horizon, appears a little more than its own diameter above the position than where it is in reality. This makes sunrise more than another two minutes earlier and sunset the equal amount later.
Atmospheric refraction is greatest for signals near the horizon where they come in at the lowest angle. The apparent altitude of the signal source can be on the order of half a degree higher than its true height.
*** Does atmospheric refraction give polar winters extra daylight time?
*** Does any location on Earth get the same number
of sunshine hours each year? .
*** Unequal Seasons
*** The Sun and Seasons ...
To explain this oval shape, we must examine how rapidly atmospheric refraction increases as we near the horizon. At altitudes of 20, 10 and 00 the respective angles of refraction, r, are 18.4', 24.75', and 35.35'.
Related issues of atmospheric refraction applied to all astronomical observations.
Corrections have to be made for atmospheric refraction and the effects of "seeing". Also stars actually do appear to move across the sky relative to other stars in a definite direction over time.
Atmospheric refraction, however, brings the Sun into view a few minutes before this theoretical sunrise and keeps it up for a few minutes past theoretical sunset.
The center of the sun is geometrically above and below the horizon for equal lengths of time on the two days of the year when the sun passes the equinoxes; if the sun were a point and atmospheric refraction were absent, ...
But, before he could use the raw observations, Kepler felt that he had to solve the problem of atmospheric refraction: how is a ray of light, coming from a distant heavenly body located in the less dense regions of outer space, ...
observer may be unable to see all the stars that lie above his celestial horizon because of obstructions such as buildings, trees, or mountains; he may be able to see some stars that lie below his celestial horizon because of atmospheric refraction.
 See also: Refraction, Earth, Horizon, Sun, Time
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