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South Polar Halo.jpgSouth Polar Halo57 visiteWhen Sunlight reflects and refracts off of tiny ice crystals in the atmosphere, the result can be ice crystal halos, which are related to rainbows (the latter being produced when Sunlight reflects and refracts from water droplets).
In Antarctica the temperatures are cold and the air is dry, so snow crystals grow very slowly. This slow growth tends to produce very clean hexagonal prisms, which are well suited for producing beautiful atmospheric displays. The example here is a South Pole halo, showing a rich variety of arcs and halos.
Halos arise from the way minute ice crystals in the atmosphere scatter Sunlight (or Moonlight!) into different angles.
The quality of a halo depends on the type and quality of the ice crystals that produce it.
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Sun Pillars.jpgLight Pillars' Parade77 visiteDa "NASA - Picture of the Day" del 5 Marzo 2006:"How can an aurora appear so near the ground? Pictured above are not aurora but nearby light pillars, a local phenomenon that can appear as a distant one. In most places on Earth, a lucky viewer can see a Sun-pillar, a column of light appearing to extend up from the Sun caused by flat fluttering ice-crystals reflecting sunlight from the upper atmosphere. Usually these ice ice crystals evaporate before reaching the ground. During freezing temperatures, however, flat fluttering ice crystals may form near the ground in a form of light snow, sometimes known as a crystal fog. These ice crystals may then reflect ground lights in columns not unlike a Sun-pillar. In the above picture, the colorful lights causing the light pillars surround a ice-skating ring in Fairbanks, Alaska".
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ZZ-ZZ-ZZ-FM-TLP-Proclus-Lunar Flash.jpgLunar "Flash" near the Terminator123 visite"Among the most enigmatic astronomical occurences are Lunar Transient Phenomena, instances of areas on the Moon appearing to brighten, darken, or change color on a time-scale of minutes. The very existence of LTP's is controversial, though they have been reported for 2 centuries (S&T: November, 1988, page 478).
Now a most remarkable one seems to have been photographed. On May 23, 1985, G. Kolovos (University of Thessaloniki) was testing a 4 1/4-inch refractor by taking pictures of the four-day-old Moon from a small village in Northern Greece. One of his seven photographs revealed a bright dot near the Moon's Terminator.
Kovolos and colleagues from the university closely analyzed the image of the dot, near the crater Proclus "C".
They write in the December, 1988 "Icarus", that the oval spot is 22 Km across and seems to conform to the local topography. What could causee such a bright flash on the Moon? The authors consider and dismiss several possibilities. Kodak Laboratories in Athens examined the film and concluded that the spot was not a film defect. It was not a surface reflection, because the illumination pattern implies that the flash occurred ABOVE the lunar surface. A volcanic eruption would have left an obscuring cloud on subsequent photos. So would a meteor impact.
Kovolos and co-workers hazard a guess that the intense heating of the lunar surface after sunrise might force cracks open, allowing trapped gas to escape. As the gas rises and expands, an electrical discharge could conceivably make it glow brightly. Many LTP sightings do occur near the lunar terminator within a day of sunrise. The researchers warn that their theory is far from being an explanation for all LTP's. "We present our results with caution," they write, "and we hope that additional data may lead to their indisputable explanation."
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ZZ-ZZ-ZZ-FM-TLP.gifTLP or illuminated "peaks" (again)?134 visiteObserver Joshua Try located in Whangarei, New Zealand reported that on 25-09-2001 at 8:30 U.T. he observed two possible L.T.Ps. on the edge of the terminator near the crater Archimedes. They appeared to be 2 bright points of light about the size of Mount Piton. They seem to form a triangle with Mount Piton. He observed them for 2 hours and they were still visible when he ended his observing session.
I had the opportunity to conduct some video tapping of the Moon on 22 January 2002 at 00 hr 18 min U.T. and was able to capture the Moon under similar lighting conditions. The image was taken with SCT C8 using 25mm eyepiece in projections. This image was taken when the Moon was 8.4 days old and the colongitude was 8.92. It may be that since the locations are very close that what Joshua saw was the tops of the mountain peaks just catching the sunlight. My image which is one lunar day later shows the mountains fully illuminated. I have had several reports in the past years that have reported these features as possible L.T.P. It can be very impressive and striking when one first sees these feature just catching the sunlight. It is my opinion that what the observer witness was peaks of these two mountains deep past the sunrise terminator.
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