Early risers in the British Isles on Thursday, March 12th have an observing treat in the form of a close conjunction between the 20-day-old waning gibbous Moon and ringed planet Saturn in the constellation of Scorpius low to the south at 5 am GMT. The pair will be separated by just 2°, so they can be seen in the same field of view of virtually any binocular — or, indeed, telescopes magnifying 20x or less.
Despite its low altitude as seen from the British Isles, Saturn is particularly attractive in a telescope at the present time since its rings are widely tilted in our direction with the planet’s northern hemisphere on show.
Gas giant Saturn is the Solar System’s second largest planet after Jupiter and its globe is nine times the diameter of Earth. The rings are composed of countless millions of icy moonlets ranging in size from specks of dust to around 10 metres in diameter, all orbiting Saturn in a 20-metre-thick plane, extending from 4,100 miles (6,600 kilometres) to 75,000 miles (120,700 km) above the planet’s equator.
If you notice some starlike points of light close to Saturn in your telescope, these will be the planet’s moons. The brightest is 9th magnitude Titan closely followed by 10th magnitude Rhea. On the morning of March 12th, Titan will lie slightly more than four ring diameters to the west of Saturn, which is to the left of the planet in Newtonian telescopes and refractor/Schmidt-Cassegrain/Maksutov-Cassegrain telescopes with a star diagonal. Clear skies!