It’s August and the Perseids are right around the corner. The most famous meteor shower of the year should reach peak activity in the morning of August 12, between 00 and 04 UTC (Coordinated Universal Time). According to Jérémie Vaubaillon, one of the foremost meteor scientists, we should have better than average rates this year. Of course, take this with a grain of salt; nobody guarantees it’s going to happen. But even if we have normal activity from the Perseids, the show will be pretty spectacular. Expect to see around 50-60 meteors per hour; maybe more.
But what are the Perseids? The Perseids, like most meteor showers, originate from comets. While travelling through the Solar System, comets leave behind a stream of debris, called meteoroids. These are very small bodies, ranging in size from a grain of sand to one meter. When comets intersect the orbit of a planet (in our case, Earth), gravity makes the meteoroids gather into clouds along the orbit of the planet. When Earth goes through one of this clouds of particles, the meteoroids fall towards the planet. Because of friction with the atmosphere, the gases surrounding the small meteoroid get ionised and emit light. This phenomenon is called meteor and is seen from the surface of Earth as a streak of light crossing the night skies. They happen very fast, usually in just a blink of an eye. Brighter meteors, called fireballs or bolides, will be visible for a few seconds and can get very bright and even fragment. When our planet intersects one of the meteoroid clumps I talked about, we see meteor showers. Some of the showers are more active than the others. The two most active showers throughout the year are the Perseids and the Geminids (you can observe the Geminids around December 13-14). The Perseids are active from late July until mid August, usually peaking between August 11 and 13. Their parent body is comet 109P/Swift-Tuttle.
I bet many of you, besides enjoying a great light show, also want to photograph the Perseids. Photographing meteors is quite easy and straight forward. You need a camera, a wide angle lens, a tripod and clear and dark skies. During this year’s maximum, the Moon will set around midnight, which is great as meteor showers are always more active in the second part of the night.
First, you need to find a dark site to observe and photograph the Perseids from. It can’t be done from the middle of the city as light pollution will make most meteors invisible. So, go outside populated areas and, if possible, find a scenic place, as photos are going to look a lot better with a beautiful foreground.
Then you need a tripod. The sturdier, the better. If it’s not rigid enough, attach a heavy thing below the central column of your tripod; some water bottles in a bag should do it. If you don’t have a tripod you can improvise some sort of support for your camera using rocks or a bag of beans.
Any camera with manual controls should do the job, but a DSLR is the best choice. In terms of lenses, go for a fast wide angle one. But remember that the wider the lens, the less impressive the meteors, unless they are exceptionally bright. I would not recommend lenses wider than 15mm on a full frame camera. If you have a second camera, a fisheye lens might be a nice choice for it. But, if you are to choose between a wide angle and a fisheye, go for the wide angle. You will need a fast lens, in order to maximise the number of photographed meteors. Lenses that open to 2.8 or faster are the best choice. Remember that meteors move very fast and even if they might seem bright to the eye they might look pretty dull on camera.
Focus is critical. In order to achieve focus at night, turn your camera to LiveView, turn the lens to manual focus and rotate the focus ring until you are close to the infinity mark on your lens. Boost the ISO, open the aperture to the max and frame a bright star in the display on the back of your camera. Zoom in 10x on the image on the display and adjust focus until stars are sharp. From now on, be careful not to touch the focus ring and the zoom ring (if you’re using a zoom lens) for the rest of the night. It might be a good idea to tape down the rings using some gaffer tape. If you want to change the focal length of the lens you will have to refocus.
We will be shooting in Manual mode as the camera will not be able to meter at night. Of course, we will use RAW format. Choose an ISO in the range of 800 to 3200, open the aperture as wide as the lens allows and choose the exposure time according to the amount of light pollution you have around you. Be careful not to go too long with the exposure as you’ll get trails and not pinpoint stars. As a rule of thumb, don’t use an exposure time longer than 500/focal length of your lens. So, if you use a 16mm lens, the maximum exposure time for pinpoint stars is 500/16 = 30 seconds. The formula is true for full frame cameras. If you don’t have a full frame camera, multiply the focal length of your lens by the crop factor. Let’s say you have a Canon camera with a 1.6 crop factor and the same 16mm lens. Now, the maximum exposure time will be 500/(1.6×16) = 19 seconds. A remote release will be very helpful; an intervalometer even more helpful. If you don’t have any of those, use the time release on your camera. Disable Long Exposure Noise Reduction (LENR) so that you don’t waste any time between frames.
Where to frame? Basically anywhere. Unless you have a lens wider than 24mm, don’t frame towards the radiant of the meteor shower, in our case the constellation of Perseus. The radiant is the point in the sky, from which meteors appear to originate, for an observer on Earth. Meteors actually enter the atmosphere in parallel tracks; the radiant is just a perspective effect. Consider framing the horizon too, as photos will look a lot better with ground showing in the image. Don’t forget about the rule of thirds, if you have some nice elements in the foreground. Another idea might be to frame towards Polaris and then merge all individual shots in a startrails composite image.
You might have a problem when shooting for a long time: dew. In order to avoid dew, you can either get a dew heater or stick some chemical hand/feet warmers to the lens hood. As a general rule, never shoot at night without a lens hood. Besides minimising stray light, you also prevent dew.
Remember to wear warm clothes. Summer nights are pretty cold, especially if you’re in the middle of nowhere.
If you have a star tracker, like the Fornax LighTrack II let’s say, you can do tracked shots of the summer Milky Way and maybe you’re lucky to get some nice meteors in the frame, too.
Another nice project is to photograph meteor smoke trails. For that, have a telephoto (135-200mm) lens prefocused to infinity and ready on a tripod. When a bright meteor appears you will see a smoke trail left behind it. Quickly move your camera body from the wide angle lens to the telephoto one waiting on the tripod. Frame the smoke trail as fast as you can and start shooting, using a high ISO (6400, let’s say) for several minutes. Don’t forget to keep your exposure time short so that you don’t get star trails. You can get something like this: