Mars will (not) appear as big as the full Moon!
This evening I was on the roof of the Physics
Department School in Manchester teaching a new pair of fourth year students how to use the telescope in the observatory. Unfortunately, the CCD camera decided it didn't want to work properly so we spent most of the evening looking at various objects through the eyepiece. We looked at Alberio, the double cluster, the Pleiades, M15, M31 and we looked for several other objects but the general orange haze of Manchester stopped us seeing them.
The most impressive sight, though, was Mars. The red planet is nearing close approach again and is getting quite large in the sky. Through the 10-inch Schmidt-Cassegrain telescope we have in the observatory the planet was a large disk with variations in surface detail clearly visible. It's the best view of the planet I've had since August 2003 when Mars had it's last close approach. Back then I helped out at a big star party at Macquarie University. Every Friday they open their observatory to the public and on the night of closest approach they had a big star party. Along with a huge number of members of the public, several astronomers from the AAO came along with their families. This year's approach is not quite as close as that one, but it is not far off. From this part of the world, Mars is rising in the East at about 8pm BST and is reasonably high by 10pm.
You may have come across stories that Mars is going to appear as large as the full Moon, but (as you might imagine) this is complete rubbish. Mars is approximately 6700 kilometres in diameter and the closest it will come to the Earth is 69 million kilometres. From simple high school maths you can work out for yourself just how big Mars will get. At closest, it will appear 20 arcseconds in diameter. Pretty big, but a lot smaller than the Moon which has an angular diameter of about half a degree.