Look towards the north between dusk and dawn and catch a glimpse of Comet NEOWISE.
What is Comet NEOWISE?
Comet C/2020 F3 NEOWISE was first discovered in March this year by astronomers using the NEOWISE space telescope. The telescope is used to detect Near Earth Objects (NEOs) which could impact Earth. But this comet poses no threat. Instead, it’s passing at a distance of 0.69 astronomical units (103 million km); that’s more than 400 times further away than the Moon. Throughout July, Comet NEOWISE has been providing professional and amateur astronomers with a spectacular view.
Comets are icy objects which orbit the Sun. They range from a few hundred metres to tens of kilometres across. When their orbit carries them close to the Sun, they warm up and release dust and gases, which form two distinct tails. The gas tail always points away from the Sun — a sort of solar windsock. Unlike meteors, which are pebble-sized (or smaller) objects that burn up in our atmosphere creating a bright streak that’s gone in a flash, comets appear to move much more slowly in the night sky.
When Comet NEOWISE approached and rounded the Sun, astronomers were optimistic that it would reach a brightness visible with the naked eye. But after the breakup of Comet ATLAS earlier this year, nobody could be certain. Then the news broke that Comet NEOWISE could be seen, even without binoculars or a telescope, and comet watchers across the northern hemisphere felt a huge sense of relief.
At the beginning of July, the comet was only visible in the early hours of the morning, but it is now visible from dusk until dawn. Even non-astronomers have caught a glimpse of Comet NEOWISE, simply by looking northwards and looking for a ‘star’ with a hazy tail. Throughout the month, Comet NEOWISE has been steadily climbing higher in the sky, towards the constellation Ursa Major (the Big Dipper).
How to spot the comet
Due to its impressive brightness, Comet NEOWISE can be seen from just about anywhere in the northern hemisphere with a clear view of the northwest horizon. Look in the northwest sky until you see a ‘star’ with an upwards-pointing tail. At the moment, the comet is to the bottom right of the Big Dipper. The image above shows the comet’s position at 11pm each night from July 15 (marker 2) through to July 25 (marker 12).
By about 1am, when the sky is darker, the comet’s tail will be long and bright, especially when viewed through binoculars or a telescope. Long exposure photographs show the tail even more impressively.
Taking a photo of Comet NEOWISE
The key to taking a good comet photo is a steady camera. If you’re using a DSLR or mirrorless camera, set it up on a tripod with a lens of medium to long focal length (50-200mm) set at its widest aperture (lowest f-stop). Set your shutter speed to 10 seconds, and use a high ISO (1000-2000). Use a timer or remote to minimise camera shake. Take a test shot, and adjust your exposure and ISO settings as necessary.
But you don’t need expensive camera gear to take a photo of Comet NEOWISE — you can take an impressive photo using just your phone. Mount your phone on a tripod and use Dark Mode in the camera app, or use an app such as NightCap for iOS.
The best landscape comet photographs frame the comet with an interesting foreground, such as a large tree, a building, or even famous landmarks like Stonehenge.
If you have a telescope, a long exposure photo taken with your camera attached will show the comet’s long, curved tail, made of ejected dust as the comet is warmed by the Sun. And if you’re in a dark enough location, you’ll see the comet’s faint blue gas tail, produced by interactions with solar wind.
But be quick
Comet NEOWISE will pass closest to Earth on July 23, after which it will become steadily fainter in the sky as it heads away from the Sun on its 6800-year-long orbit. Go out and enjoy the view while it lasts, because there probably won’t be a comet as good as this for a long time.
