Solar eclipse on August 1

Kathmandu:

A total solar eclipse will take place on August 1. The sun will be completely obscured for just less than two-and-a-half minutes when it starts.

This year’s full eclipse will be visible from a narrow arc spanning the Northern Hemisphere. It will be visible from northern Canada, northern part of Russia, western Mongolia and China.

A partial eclipse will be seen from the much broader path of the moon’s penumbra including Nepal, eastern North America and most of Europe and Asia.

In Nepal, the partial solar eclipse starts at 16:22 and continue till 18:13 (4:22 to 6:13 pm).

A total solar eclipse occurs when the moon completely covers the sun as seen from the earth. Total solar eclipses happen because the sun is near one of the nodes of the lunar orbit, and the moon is at perigee (the point in the orbit of the moon or a satellite at which it is nearest to earth) at this node at the same time.

Totality of a solar eclipse can last from about seven minutes anf 31 seconds, but these eclipses are rare. It is predicted that totality during the solar eclipse will last for seven minutes and 14 seconds in the year 2150, which is longer than any total solar eclipse since the ninth century AD. A period of totality is normally shorter than five minutes.

About 25 per cent of eclipses are total eclipses, and there are about seven of these a decade. But at any given geographic location, a total eclipse will be visible at an average of once in 375 years.

The solar eclipse has been linked to many ancient customs and traditions. Many eclipse enthusiasts across the world wait eager for a solar eclipse to occur so they can experience and remember the moment.

Permanent eye damage can result from looking at the disk of the sun directly or through a camera viewfinder, or with binoculars or a telescope even when only a thin crescent of the Sun remain. One per cent of the sun’s surface still visible is about 10,000 times brighter that the full moon. Never look at the sun outside of the total phase of an eclipse unless you have adequate eye protection.

Make your own filter

You can make your own solar filter. Open up a roll of black-and-white film and expose it to the sun for a minute. Have it developed to provide you with negatives. Use the negatives as filter. It is best to use two layers. With this filter, you can look directly at the sun safely.

Remember, however, that if you are planning to use a black-and whitefilm as a solar filter, you need to prepare it at least several days in advance.

Solar eclipses ahead

• Annular solar eclipse: January 26, 2009

• Total solar eclipse: July 22, 2009

(Acharya is a member of the American Astronomical Society)

Specialist says

KATHMANDU: Dr Jeevan Shrestha, who is the Executive Director and Professor at Opthalmology Department, BP Koirala Eye Centre, Teaching Hospital, strictly warns against looking at the solar eclipse as it can cause solar burn, due to which the most sensitive part of the retina — the macula — may be damaged. This may blur one’s vision permanently and is unrepairable.

For those who are thinking of making their own protective filters or using special sunglasses, Shrestha warns that there is no guarantee that such filters will provide any protection as such.

So looking at the eclipse is best avoided. However, looking through telescopes is okay on condition that you confirm that the necessary filters have been used to protect the eyes.

From young children to old people, especially those who’ve had cataract operation should not watch the eclipse as it will affect them even more. — HNS