Comet 21P photographed from Kendal, Cumbria on the evening of Aug 31st. The bright star at bottom is Capella.
If you’ve never seen a comet before – or if you haven’t seen one for a while – then you have a great opportunity to see one this evening, if your sky is clear of course! Comet 21P Giacobinni-Zinner is visible in the sky after dark at the moment, and although it isn’t bright enough to see with the naked eye it IS bright enough to be seen through just a pair of binoculars, and will be a very pretty sight through a small telescope.
But the best thing is how easy it will be to find it tonight: it will be right next to one of the brightest stars in the sky, so if you can find that star you can find the comet, it really is as simple as that!
The star in question is Capella, the brightest star in the constellation of Auriga, the Charioteer. After dark tonight Capella will be low in the north-east, to the lower left of the W-shaped constellation of Cassiopeia and the upside down Y-shaped constellation of Perseus.
If you don’t know how to find those, don’t worry, you can use the stars of the Big Dipper (or “The Plough” or whatever you know that star pattern as) to find Capella, and the chart below shows you how.
Once you’ve found Capella in the sky – it’s a yellow-white colour – then you need to centre it in your binoculars or small telescope. The comet will be to the right of the star, just a little bit below it.
A word of warning: you will NOT see a bright starry object with a beautiful misty tail stretching away behind it, like you will have seen in photos, sorry! Through your binoculars 21P will look like a small, misty, out-of-focus star, perhaps with a slight greenish tinge. Through a small telescope it will be more obvious and will appear elongated too. If you don’t see it straight away don’t worry, comets don’t jump out at you at the best of times, and you might need a few minutes before 21P shows itself, especially if there’s any light pollution around you. We’d definitely recommend getting away from as many lights as possible if you want to see this comet – the darker your sky, the easier it will be to find and the brighter it will look.
And that’s it, that’s all you have to do! 1) find the Big Dipper, 2) use it to find Capella, then 3) look for the comet right next to it with your binoculars or telescope. If you don’t manage to see it tonight, the comet will be close to Capella over the next few nights too – comets move slowly across the sky, they don’t whoosh across it like shooting stars do – moving away from it towards the horizon. Any night between now and, say, Wednesday if you find Capella and then look to its right and down a bit you’ll find 21P.