Meteor showers are associated with comets. When the Earth passes through the dust and debris left behind by the comet as it orbits the Sun, these particles fall through the atmosphere at high speed and burn up due to friction as they rub against the air molecules. This is what we see as meteors, or shooting stars, as they flash across the sky in streaks of light.
Because we know roughly when we pass through the dust and debris left behind by various comets, we can predict when we are likely to see meteors. It can take several days or weeks to pass through this dust, but when we go through the thickest part, we experience a peak of meteor activity over one or two nights.
This month we pass through the dust left behind by comet Swift-Tuttle, and we travel through the most concentrated part of this on the night of 12-13 August each year. Because of the way we pass through these meteor streams, the meteors themselves appear to radiate from a single point in the sky, known as the radiant. The radiant for the Perseids is, not surprisingly, located in the constellation of Perseus. This means that the meteors seem to streak across the sky from this point. They can travel in any direction and vary in brightness depending on size, but most of them are only the size of a grain of sand. The Perseids are, on the whole, fast-moving and bright.
The term meteor ‘shower’ can be a little misleading though. Don’t expect it to be raining meteors! This can occur, but very rarely, in which case the shower is called a storm. However, at the peak of the Perseids you can expect to see several streaks, known as events, per hour. You can record the meteors with a smartphone, but to do this you’ll need to download an app to extend the exposure time. For iPhones you can use ‘Slow Shutter Cam’ and for Androids you can download ‘FV-5’. These apps allow you to set the exposure time and ISO manually. Up to 30 seconds exposure is ideal for meteors. Point the smartphone at any part of the sky once it is attached to your tripod and start taking pictures. You never know, you might be lucky and snap a bright meteor.
Capturing the Perseids
Imaging meteors involves a little knowledge and a lot of luck. You can improve your chances of success by following the steps below. Be persistent: you’re likely to see a few meteors if you stay out for at least 20 minutes. The longer you’re outside, the more your chances increase. Being comfortable and warm will make the experience more enjoyable. Again, if you take more images, you are more likely to capture a meteor. Try not to be disappointed if you don’t catch any though, as there’s always next year!
Step 1: Wear plenty of layers
It can get very cold at night, even during the summer months, so dress appropriately. A garden chair is good for comfort, too.
Step 2: Get to know your app
Try out your long-exposure app before the meteor shower, to increase your chances of getting a good image of the Perseids on the night.
Step 3: Set up your tripod
Even a small tabletop tripod – compatible with your smartphone – will help to keep your device steady and your images sharp.
Step 4: Aim your camera
Point your camera almost anywhere in the sky. You never know when the next meteor will whizz past or in what direction it will come from.
Step 5: Take lots of shots
Take as many pictures as your smartphone’s memory can handle. This will increase your chances of catching a meteor.
Step 6: Process your images
You can download your pictures the next day and start to sort and process them to see if you’ve bagged a few meteors.