The annual Perseid meteor shower, which is caused by debris from Comet Swift-Tuttle and observed for about 2000 years, will be hampered this year by the full moon, which happens when Earth comes between the Sun and the Moon.

The full moon falls on August 13 and is also called 'Grain Moon' or 'Green Corn Moon'. At the full moon, the moon rises about the same time the sun sets and it sets at about the same time the sun rises.

This will create difficulty in viewing the Perseid meteor shower, which peaks on the night of Friday and into the early morning of Aug. 13.

Normally, Perseid peaks at 100 or more meteors per hour in the absence of moonlight on new moon (when the moon is between the Sun and the Earth), which is not visible from Earth as the side of the moon that is facing us is not being lit by the sun.

It is considered by many that the Perseids is the best meteor shower of the year, but with the full moon washing out all but the brightest meteors, rates will probably only be 20-30 per hour at most -- weather permitting.

Despite the moon brightness, astronomers are suggesting sky-watchers to look for meteors in the early morning mostly after 3 a.m. on Aug. 8, 9 and 10. This is because the moon will set about 2.5 hours early on Tuesday before the sun rises but this will shrink to 1.5 hours on Wednesday and less than half hour by Thursday.

The Perseids rate in the southern hemisphere is quite a bit lower, since the Perseid radiant doesn't climb above the horizon, NASA said in a statement. The name derives in part from the word Perseides, a term found in Greek mythology referring to the sons of Perseus.

The stream of debris is called the Perseid cloud and stretches along the orbit of the comet Swift-Tuttle, which orbits the sun once every 133 years. The Earth passes through a cloud of the comet's debris each year in August.

The huge comet swings through the inner solar system and leaves behind a trail of dust and gravel. These bits of ice and dust -- most over 1,000 years old -- burn up in the Earth's atmosphere.

The Perseids are so-called because the point they appear to come from, called the radiant, lies in the constellation Perseus. The Perseids can be seen all over the sky, but the best viewing opportunities will be across the northern hemisphere.

Some Catholics refer to the Perseids as the "tears of St. Lawrence", since August 10 is the date of the saint's martyrdom.

A meteor shower is a celestial event in which a number of meteors are seen radiating the night sky. Meteor showers are the result of a passing comet.

As the comet approaches and rounds the Sun, it sublimates (turns from a solid directly into a gas, like dry ice), creating a cloudy sphere, called the coma, around the nucleus. The solar wind pushes on the coma forming the long comet’s tail, which always points away from the Sun.

The Perseid meteor shower will be followed by the Geminids during mid-December and Quadrantids during January, which are the only major meteor showers not originating from a comet, according to NASA.