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Clouds obscuring lunar eclipse dismay skywatchers; rain may disrupt view of Venus transit

June 5, 2012 9:08am
No thanks to cloudy skies, many Filipino skywatchers who tried to witness Monday night's lunar eclipse went home dismayed.
 
Many skywatchers had gone to the Philippine Atmospheric Geophysical and Astronomical Services Administration in Quezon City to watch the eclipse, radio dzBB reported.
 
In some areas, however, the moon appeared to shine brightly after the eclipse ended at about 8 p.m.
 
"100 percent po kase ang illumination," PAGASA said on its Twitter account in explaining the brightness.
 
The dzBB report said 37 percent of the moon was covered by the earth's shadow during Monday night's eclipse.
 
Venus transit
 
Meanwhile, PAGASA indicated rainy weather may disrupt stargazers' view of a rare transit of Venus that will be visible in the Philippines.
 
PAGASA's five-day extended outlook for June 6 indicated rain on Monday from June 6 to 7.
 
The entire transit of Venus is visible in Greenland, North and Central America, Pacific Islands, Australasia, Asia including the Philippines, East Africa and most of Europe.
 
"The transit or passage of a planet across the face of the Sun is a relatively rare occurrence. As seen from Earth, only transits of Mercury and Venus are possible ... Since the planets Mercury and Venus orbit inside the path of the Earth around the Sun, they too can come between the Earth and the Sun. However since these planets have a tiny apparent diameter as seen from Earth, the Transit is seen as a small black disk moving across the face of the Sun," PAGASA administrator Nathaniel Servando said.
 
PAGASA added there are 13 transits of Mercury in a century.
 
Transits of Venus, on the other hand, occur in pairs with more than a century separating each pair.
 
"Only eight such events have occurred since the invention of the telescope (1631, 1639, 1761, 1769, 1874, 1882, 2004 and the upcoming 6 June 2012). The 2004 and 2012 transits form a contemporary pair separated by eight years. The next two transits of Venus will occur on 2117 and 2125," Servando said.
 
The transits are characterized by contacts, similar to that of an annular solar eclipse.
 
At contact I, the planet's disk is externally tangent with the Sun. Shortly after this, the planet can be seen as a small spot along the solar limb.
 
At contact II, the planet is first seen as it is internally tangent with the Sun. The silhouetted planet then slowly traverses the brilliant solar disk.
 
At contact III, the planet reaches the opposite limb and is internally tangent with the Sun.
 
The event ends at contact IV when the planet's limb is externally tangent to the Sun.
 
In the Philippines, Contact I is expected at 6:09 a.m.; Contact II at 6:27 a.m.; Greatest at 9:29 a.m.; Contact III at 12:31 p.m.; and Contact IV at 12:49 p.m.
 
Viewing tips
 
"The safest way to observe a transit is to project the image of the Sun through a telescope, binoculars, or pinhole onto a screen, but the event can be viewed with the naked eye using filters specifically designed for this purpose, such as an astronomical solar filter with a vacuum-deposited layer of chromium, eclipse viewing glasses, or Grade 14 welder's glass," Servando advised.
 
He said using exposed black-and-white film and processed color film as filters are no longer regarded as safe.
 
"Observing the Sun directly without filters can cause a temporary or permanent loss of visual function, as it can damage or destroy retinal cells," he said. –KG, GMA News
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