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Partial lunar eclipse and rare transit of Venus in Hong Kong in June

     A partial lunar eclipse will occur on June 4 (Monday) and a rare transit of Venus will occur on June 6 (Wednesday). These astronomical phenomena will be visible in Hong Kong if the weather permits.

Transit of Venus on June 6

     The transit of Venus across the sun will occur on June 6. During the transit, Venus will come between the sun and the Earth. The silhouette of Venus, appearing as a dark dot, will move across the sun's disc.

     The Scientific Officer of the Hong Kong Observatory, Mr Woo Wang-chun, said, "Transit of Venus is a rare astronomical phenomenon. It comes in pairs eight years apart, with successive pairs separated by over 100 years. This transit of Venus will be the second one in a pair, with the first one having occurred on June 8, 2004. After this one, there will be no transit of Venus in the next 100 years. This transit will occur between 6.12am and 12.49pm, lasting six hours and 37 minutes. The entire process can be observed in Hong Kong, as the sun will rise at 5.39am on the day." Please refer to Diagram 1 for the path of the transit of Venus.

     Details of the transit of Venus are as follows:

                Hong Kong   Direction       Elevation
                time        (Azimuth)
                ---------   ---------       ---------
Begins to enter   6.12am    East-northeast  6 degrees
the sun's disc              (68 degrees)

Just entirely     6.30am    East-northeast 10 degrees
inside the sun's            (70 degrees)

Begins to leave  12.31pm    West           88 degrees
the sun's disc              (281 degrees)

Just entirely    12.49pm    West           84 degrees
outside the                 (275 degrees)
sun's disc   

     "As the elevation of the sun will be rather low at the beginning of the transit, the initial contact of Venus with the sun can only be observed at places with an unobstructed view of the horizon in the direction of east-northeast, such as Plover Cove Reservoir, Tai Au Mun in Sai Kung and the middle part of the Avenue of Stars in Tsim Sha Tsui. Most of the event, on the other hand, can be viewed from exposed areas in any district," Mr Woo said.

     As is the case when observing a solar eclipse, members of the public should never look directly at the sun with naked eyes or through a telescope in order to avoid severe damage to their eyes. A safer method is to project the sun's image through a pinhole or a telescope onto a piece of white paper or cardboard and view the projected image. An illustration is given on the Observatory's website: .

     A webcast of the event will be jointly provided by the Hong Kong Observatory and the Hong Kong Space Museum on the following webpage: .

     The Curator of the Hong Kong Space Museum, Mr Chan Ki-hung, said, "The Space Museum will jointly organise an event called 'Transit of Venus Observation' with the Science Faculty of the University of Hong Kong, the Hong Kong Astronomical Society and the Ho Koon Nature Education cum Astronomical Centre in the middle part of the Avenue of Stars in Tsim Sha Tsui from 6am to 1pm. Participants will have the opportunity to observe the transit with telescopes and other kinds of astronomical instruments under expert guidance. The activity is provided free of charge and no registration is required."

     A simulation of the transit of Venus is also available at the YouTube channel of the Space Museum (

     The next pair of the two events of transit of Venus across the sun will occur in 2117 and 2125.

     Please refer to the Observatory's website for detailed information on the transit of Venus: .

Partial lunar eclipse on June 4

     A partial lunar eclipse will occur on June 4. Mr Woo said, "By the time the moon rises that evening, the eclipse will have started. The middle of eclipse will occur soon after the moonrise, and will be visible in Hong Kong along with the remaining parts of the lunar eclipse. The eclipse will have an umbral magnitude of 0.376, meaning that 37.6 per cent of the moon's diameter will enter the umbra (total shadow) of the Earth at the middle of eclipse." Please refer to Diagram 2 for the path of the moon during the eclipse.

     Details of the partial lunar eclipse are as follows:

             Hong Kong    Azimuth          Elevation
             ---------    -------          ---------             
Moon enters  (invisible in Hong Kong)

Moon enters  (invisible in Hong Kong)

Moonrise      7pm         East-southeast   -1 degrees

Middle of     7.03pm      East-southeast    0 degree

Moon leaves   8.07pm      East-southeast   12 degrees

Moon leaves   9.20pm      Southeast        26 degrees

     "As the elevation of the moon will be rather low during the eclipse, the event can only be observed at places with an unobstructed view of the horizon in the direction of east-southeast, such as beaches at Shek O, Stanley and Clear Water Bay, the northern coast of Hung Hom, and the east dam of High Island Reservoir," Mr Woo said.

     The next lunar eclipse potentially observable in Hong Kong will occur on November 28, 2012. It will be a penumbral eclipse.
     Please refer to the Observatory's website for a detailed explanation of lunar eclipses:

Ends/Wednesday, May 23, 2012
Issued at HKT 17:51


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