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Partial lunar eclipse visible in PHL on Monday, June 4


Barring cloudy skies or inclement weather, Filipinos can get to see a partial lunar eclipse on Monday, June 4, state astronomers said.
 
The Philippine Atmospheric Geophysical and Astronomical Services Administration (PAGASA) said the umbral eclipse will start at 4:46 p.m. and will end at 9:19 p.m.
 
"(Its) magnitude will be 37.6 percent and will also be visible primarily in west parts of America, Pacific Ocean, Antarctica, eastern Asia, Japan and Australasia(Australia, New Zealand, the island of New Guinea, and neighboring islands in the Pacific Ocean)," PAGASA administrator Nathaniel Servando said.
 
In Manila, Servando said the moon will rise at 6:17 p.m. Monday, and will set at 4:55 a.m. of Tuesday.
 
PAGASA said the penumbral eclipse begins at 4:46 p.m., while the partial eclipse begins at 6:59 p.m.
 
The greatest eclipse will occur at 7:03 p.m., while the artial eclipse ends at 8:07 p.m., while the penumbral eclipse ends at 9:19 p.m.
 
"Lunar eclipses are safe to watch, hence, observers need not use any kind of protective filters for the eyes. A pair of binocular will help magnify the view and will make the red coloration of the Moon brighter," Servando said.
 
Transit of Venus
 
On June 6, a rare transit of Venus will be visible in the Philippines.
 
The entire transit 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," Servando said.
 
On the average, there are 13 transits of Mercury in a century.
 
In contrast, transits of Venus 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 principal events occurring during a transit are characterized by contacts, similar to the contacts of an annular solar eclipse.
 
A transit begins with contact I, the instant when the planet's disk is externally tangent with the Sun. Shortly after contact I, the planet can be seen as a small spot along the solar limb.
 
The entire disk of the planet is first seen at contact II when the planet is internally tangent with the Sun. During the next several hours, the silhouetted planet slowly traverses the brilliant solar disk.
 
At contact III, the planet reaches the opposite limb and once again is internally tangent with the Sun.
 
The transit ends at contact IV when the planet's limb is externally tangent to the Sun.
 
Contacts I and II define the phase called ingress, while contacts III and IV are known as egress.
 
Position angles for Venus at each contact are measured counterclockwise from the north point on the Sun's disk.
 
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. Safe viewing
 
"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 an earlier method of using exposed black-and-white film as a filter is no longer regarded as safe, as small imperfections or gaps in the film may permit damaging UV rays to pass through.
 
Also, processed color film (unlike black-and-white film) does not contain silver, and is transparent to infra-red. This may result in burns to the retina, he warned.
 
"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.
 
Summer solstice, June 21
 
Philippine nights will be shortest and daytimes longest around the Summer solstice, which falls on June 21 at 7:09 a.m.
 
This is the time when the Sun attains its greatest declination of +23.5 degrees and passes directly overhead at noon for all observers at latitude 23.5 degrees North, which is known as the Tropic of Cancer.
 
"This event marks the start of the apparent southward movement of the Sun in the ecliptic," Servando said.
 
Stars
 
Stargazers can expect the famous Summer Triangle of the stars Vega, Deneb and Altair of the constellations Lyra, Aquila and Cygnus, respectively, being well placed in the eastern horizon before midnight.
 
The bowls of the Big and Small Dipper in Ursa Major and Minor, respectively, stands high above the northern horizon with the body of the constellation Draco, the Dragon winding between them.
 
The grouping of a horseshoe shape stars of the constellation Corona Borealis, the Northern Crown, lies on the north-south meridian with the head of Draco below it.
 
Scorpio is positioned above the east-south eastern horizon, while the constellations of Centaurus, the Centaur and Acrux, the Southern Cross is just above the south direction.
 
Planets 
 
Mercury will be visible from the first week of the month above the west northwestern horizon and will continue to move up the horizon throughout the month.
 
It will stand at about 25 degrees above the horizon during the last week making it a fine target for viewing.
 
Mars will be found overhead after sunset. It will lie among the background stars of the constellation Leo, the Lion and will be visible throughout the evening sky during the month.
 
Saturn will be glowing at magnitude +0.7 and will be high above the sky after sunset.
 
It will make a fine view as it will pair with the brightest star, Spica, of the constellation Virgo the Virgin.
 
The pairing will be visible throughout the month of June.
 
Uranus and Neptune will be visible before sunrise throughout the month. Both planets will be found at the east southeastern horizon and will lie among the background stars of the constellations Pisces, the Fish and Aquarius, the Water-Bearer, respectively. — TJD, GMA News