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Apart from the presence of ice-containing clouds in the right position in the sky, the halo requires that the light source (Sun or Moon) be very high in the sky, at an elevation of 58° or greater. This means that the solar variety of the halo is impossible to see at locations north of 55°N or south of 55°S.
Draw an imaginary line from γ Crucis to α Crucis—the two stars at the extreme ends of the long axis of the cross—and follow this line through the sky. Either go four-and-a-half times the distance of the long axis in the direction the narrow end of the cross points, or join the two pointer stars with a line, divide this line in half, then ...
A circumzenithal arc in Salem, Massachusetts, Oct 27, 2012. Also visible are a supralateral arc, Parry arc (upper suncave), and upper tangent arc. From top to bottom: a circumzenithal arc on top of a 46° halo, on top of a Parry arc, on top of a tangent arc, on top of a 22° halo, on top of the actual sun.
The celestial equator is defined to be infinitely distant (since it is on the celestial sphere); thus, the ends of the semicircle always intersect the horizon due east and due west, regardless of the observer's position on Earth. At the poles, the celestial equator coincides with the astronomical horizon.
Sky-gazers can look forward to catching glimpses of four bright planets at the same time in the night sky. Venus and Saturn will appear in the southwest, Jupiter will gleam overhead, and Mars will ...
Using a single crystal, one needs to realize all possible 3D orientations of the crystal. This has recently been achieved by two approaches. The first one using pneumatics and a sophisticated rigging, [29] and a second one using an Arduino-based random walk machine which stochastically reorients a crystal embedded in a transparent thin-walled ...
Once the sun rises in the East the angle acts in a similar fashion until the sun begins to move across the sky. As the sun moves across the sky the angle is both zero and high along the line defined by the sun, the zenith, and the anti-sun. It is lower South of this line and higher North of this line.
Relationship of Earth's axial tilt (ε) to the tropical and polar circles. The Arctic Circle is the southernmost latitude in the Northern Hemisphere at which the centre of the Sun can remain continuously above or below the horizon for twenty-four hours; as a result, at least once each year at any location within the Arctic Circle the centre of the Sun is visible at local midnight, and at least ...