March sky at night — click on the image below to see a larger version

Saturn is now a week past opposition, but remains the best-placed target for planet hunters, visible all night long among the stars of Leo, writes Chris Lintott. It forms an attractive pair with the constellation's brightest star, Regulus, which lies just a few degrees to the west (as a guide, the full Moon is half a degree across). These two neighbours are the brightest objects in the southern quadrant of the sky and are unmistakable once the skies are dark.

While a telescope will show bands of cloud on the planet's disc, and the presence of occasional large white spots enlivens the view (the most famous of these was discovered by the music hall comedian and amateur astronomer Will Hay in 1933), Saturn's undoubted glory is its system of rings.

The rings are composed of many hundreds of thousands of small icy particles, possibly the remnants of a broken-up moon, all of which orbit in a band just a few kilometres thick. Most astronomers believe that they are a transient feature, lasting for only a few million years, but for the amateur there is a more urgent reason to take a look at the rings during this apparition.

Saturn is accompanied by Mars, which is currently moving through the upper part of the zodiacal constellation of Gemini. Although it is high in the sky for most of the evening, setting at 3.30am in the middle of the month, viewing prospects for Mars are determined by its distance. As it is now more than 100 million miles away, and hence has an apparent diameter of less than 10 arcsec, the telescopic view is poor, but it is still of interest to photographers.

A particular target will be its close approach on the 11th to one of my favourite open star clusters, M35, which lurks near the end of the leg of the senior of Gemini's twins, Castor. In a dark sky this cluster is visible to the naked eye as what William Herschel described as “a very small cloudiness”, but otherwise the best way to find it is to use binoculars, and scan along the bright stars that make up Castor's body.

To see the three other planets available this month, you will have to be up just before - or even after - dawn. Mercury and Venus lie within the same binocular field of view, close to the southeastern horizon in the first hour or so after sunrise. Jupiter is low, but bright and obvious to the naked eye in the south-southeast, rising just before the sun at 4.50am at the start of the month and 3.07am at the end.

If such early rising puts you off, try viewing Jupiter during daylight, using the Moon as a guide. The first of two good opportunities this month comes on March 3, when you should look south at 8.30 in the morning. Find the crescent Moon (20 per cent of full) and use binoculars to locate Jupiter 5.5 degrees to the northwest. If you do not have binoculars, the planet might be visible with the naked eye. As a guide remember that the full Moon is half a degree across. The other opportunity is at 7.20am on March 31, with Jupiter a few degrees away from the waning crescent Moon.

Leaving the solar system behind, the familiar outline of the Plough is well placed this month. It is shown as red on our chart, in among the stars of its much larger (and much more obscure) parent constellation, Ursa Major.

Look carefully at the middle star of the three that make up the handle of the Plough; do you see anything unusual about it?

This is actually a double star, and if you have moderately good eyesight and can split Mizar from its fainter companion Alcor then you have just passed the test given to Ancient Egyptian candidates for priesthood. What the Egyptians could not have known without divine inspiration was that there are actually five stars in the Mizar system.

A second companion to Mizar was the first binary to be discovered with a telescope, and one on which Galileo wrote extensively. He hoped to use stars which were close by in the sky, but actually at different distances from the Earth to detect the Earth's motion through space, proving once and for all the reality of a heliocentric model of the solar system. Unfortunately, he failed to realise that Mizar and its companions (two more have been discovered since, bringing the total to five) were true companions in orbit about one another, and thus useless for his purposes.

Galileo's work was nevertheless truly impressive, and you will be hearing a lot more about him in the lead- up to next year's International Year of Astronomy which celebrates the first use of his telescope.

Whether you follow the Egyptians and test your eyesight, or Galileo in telescopic study, make the most of the dark nights of March. With the Sun crossing the celestial equator at the equinox in the morning of March 20, the long days - and short nights - of summer are on their way.