PARIS – Astronomers are getting themselves prepared to feast on the highlights of that one sky watcher’s year when all Earth, Mercury and Sun create an occurrence that only takes place 12 times in a hundred years. Telescopes will be used to see the Mercury that will appear to be a black dot in the sky from earth and it will not last longer than seven and a half hours. “At the start, Mercury will look as if it is nibbling at the edge of the Sun, and then it will very slowly cross its surface and leave the other side,” said Pascal Descamps of the Paris Observatory. “It's something rare, because it requires the Sun, Mercury and Earth to be in almost perfect alignment.” Mercury, one of the smallest planets of the solar system, is known to complete an orbit in around 88 days. It travels through the Sun and the Earth during every 116 days. But its orbit is tilted in relation to Earth's, which means it usually appears, from our perspective to pass above or below the Sun. T