Observing and photographing meteors
One of my favourite episodes of Dr Who is 'Blink'. It's the one that introduced us to the scary Weeping Angels, creatures of stone who are frozen into statues any time you look at them, but who can move if you close your eyes - even for the split second it takes you to blink. 'Whatever you do,' warns the Doctor to his companions, 'don't even blink.' That, to me, is the essence of a good scare. Taking the everyday, and making it something of dread...
Tonight should be one of those 'don't blink' evenings. Not this time to do with sci-fi fictional monsters, but to do with something else that can come and go in the time it takes you to blink: meteors.
Tonight should be an astronomical highlight for all and any of us who like to crane our necks and gaze into the night sky, as the annual Perseids meteor shower hits its peak. Although we have been seeing an increasing number of meteors from this shower over the past week or so, tonight marks the time when the greatest concentration will be visible. Or at least would be visible, if it weren't for the blanket of cloud forecast for Northern Ireland tonight!
But, if you have clear skies, you should definitely look out for them. The meteors will appear to emanate from a point in the sky - known as the radiant point - which is located between the 'Big Dipper' and the North Star.
When you witness one of these amazing displays, as the burning meteor streaks across the sky, it's amazing to think these celestial light shows are caused by something as small as a grain or sand. But when you're travelling at 134,000 mph, your impact with the atmosphere is enough to make you burn bright for a few seconds, in one last celestial hurrah. These tiny pieces of dust and ice are the debris trail left behind by the Swift-Tuttle comet the last time it past close to the earth way back in 1992. At this time every year, the Earth's orbit takes it through the dust cloud and we get a couple of weeks of Perseids meteors, peaking on the 11/12 August.
If you are lucky enough to have clear skies, here are some tips on how to photograph the display.
- Use a tripod to allow you to take longer exposures.
- Focus your camera manually, using a far off point of light to get focus and then keep it in focus! Or use the infinity setting on your lens if you have one.
- Use a reasonably wide angle lens - at least 18mm (the widest your kit lens will go) or even wider - as the meteors can cover quite a wide area of the sky.
- Point your camera towards the radiant point.
- Set your camera on full manual mode.
- Open your aperture as wide as it will go.
- Go for a shutter speed of around 30 seconds.
- Then set your ISO to the level you need to get a decent exposure. Higher ISOs produce more noise. But you need to let enough light in, so go as high as you need to ensure that. Check your exposure using the histogram, however, not just the image on your screen. Your eyes will have adjusted to the dark, so the screen will appear brighter than it might otherwise do once you get back home and turn the light on.
- Shoot continuously, either using an intervelometer or just clicking away. The appearance of the meteors will be quite random, so the best way to ensure you catch them is to keep shooting!
Please note that photographing meteors is very hard. You need to have your camera pointed in the right direction. You need to have the shutter open when the meteor makes its ever so brief appearance (it's unlikely that your reaction speeds will be fast enough to fire off your camera when you glimpse a meteor!). The meteor will last for such a short period of time that it would need to be very bright to register on your camera's sensor. You may well capture a satellite and think it's a meteor (see below). But don't let that put you off. Keep going, and if you're lucky enough for a fireball to streak across the sky when you've got the shutter open, you'll be lucky enough probably to capture it!
When a 'meteor' is not a meteor
Just so you know, there are a couple of night sky features that are often mistaken for meteors. So here's a heads up about them, just in case you think you've got a meteor only to end up disappointed.
- Satellites - these appear as lines of light in your pictures. But they are uniform in thickness and will appear in more than one shot if you are doing multiple shots one after the other.
Click through these images and track how the satellites move across the sky between these consecutive shots.
- Iridium flares - these also appear as lines of light, plus they seem to have a burning head similar to meteors. But they are satellite flares caused when the communication antennas of an iridium communication satellite reflect sunlight towards the earth. To the naked eye, they appear to burn and flash as they cross the night sky and can easily be mistaken for meteors. To the eye, though, they will flash suddenly and brightly in the middle of their transition. And unlike a meteor, the brightest head will appear not at the end of the line of light in your photo, but somewhere along it. If this is the case, it's an iridium flare you've captured.
So good luck to those of your fortunate enough to have some clear skies tonight. Bring a blanket, find some soft grass, and lie back and enjoy the show. And remember the advice of the Doctor: whatever you do, don't blink!