LUCKNOW, June 9 -- Skywatchers in Lucknow are set for a rare celestial spectacle on Tuesday as Venus and Jupiter appear exceptionally close to each other in the western-northwestern sky shortly after sunset in an event known as a planetary conjunction. At their closest approach, the two planets will be separated by just 1 degree 36 arcminutes-about the width of three full moons placed side by side. The conjunction will be best visible between 7.12 pm and 9.20 pm. Through telescopes, viewers may also spot Jupiter's four Galilean moons - Io, Europa, Ganymede and Callisto. Mercury could also be visible near the western horizon, creating a 'mini planet parade', said Sumit Srivastava, scientific officer at the Indira Gandhi Planetarium. To mark the occasion, Indira Gandhi Planetarium will host a free telescope observation session from 7 pm to 9 pm. htc...