May the sun shine on rare eclipse
If the stormy weather blocks the sighting of the very rare annular solar eclipse tomorrow morning, we will not get to see the golden ring again.
That explains why astronomy buffs are hoping the cloud and thunderstorms forecast to loom over Hong Kong will abate.
'The weather certainly isn't ideal for viewing a rare eclipse like this,' said the Observatory's scientific officer Woo Wang-chun, who will record the phenomenon with Space Museum staff for a live public webcast, weather permitting.
'Every year there are two to three eclipses visible in different parts of the world,' Woo said. 'What's so special about this one is it's an annular solar eclipse, meaning the sun will appear as a very bright ring surrounding the moon.'
Annular solar eclipses are extremely rare in Hong Kong - the last one occurred in 1958 and the next will be more than 300 years away - in 2320.
When the sun rises at 5.41am tomorrow, the eclipse will already have begun and it will run until 7.16am.
The period when the moon completely blocks the sun - known as totality - will last about 31/2 minutes from 6.06am. This is more than twice as long as the last one.
The phenomenon will be seen in only a few places in Hong Kong because the sun will be hanging low.
'At places like Plover Cover Reservoir, Tai Au Mun in Sai Kung and the middle part of the Avenue of Stars in Tsim Sha Tsui, a major part of the eclipse will be visible,' Woo said.
Staff of the Observatory and the Space Museum will go to a spot at the southeast end of Hong Kong Island - with a view of the horizon but not open to the public - to record the event, so those who opt to stay indoors enjoy a free live webcast.
Woo warned people not to look directly at the sun with naked eyes or through a telescope. 'A better way 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,' he said.
The museum and Hong Kong Astronomical Society will have telescopes set up on the Avenue of Stars. Staff will be on site from this afternoon to answer questions.
Besides Hong Kong, the event can be viewed in some places on the mainland, in Japan and in the Pacific Ocean and some US states.
Unlike lunar eclipses that are visible over half the earth at a time, solar eclipses are seen only in specific places.
If the earth lies between the sun and moon it will block sunlight from reaching the moon, which leads to a lunar eclipse. But if the moon is between the earth and sun, sunlight is blocked from a very small patch of the earth, causing a solar eclipse.
The next solar eclipse observable in Hong Kong will be on March 9, 2016, but it will be a partial eclipse, meaning there will not be a ring.
Patience is a virtue when it comes to such phenomenon. While the next annular solar eclipse observable in parts of Hong Kong will occur in 2320, the next one that will be viewable throughout the city won't roll around until 2685.