As the Northern Hemisphere summer nights lengthen the darkening skies are lit up by one of the most anticipated meteor showers of the astro calendar - the Perseids. Earth enters a stream of debris left in the wake of comet Swift-Tuttle around mid July, with activity peaking around August 12th when stargazers can typically enjoy upwards of 50 meteors per hour. With the promise of a warm summer's night it can easily be one of the most enjoyable displays of the year, though sadly this years show will be hampered by the moon.
A three-quarter moon will rise at roughly 11pm (depending on your location) on the night of the peak, however, Perseids are known to be particularly bright so some will still be visible. It's also worth trying during the end of July, before the moon takes over the night sky as August arrives. The hourly rate of Perseids tend to pick up during the hours before dawn when the radiant point in the constellation Perseus is high in the sky, so you get one last window of opportunity in the early hours of August 19-24th.
And don't write off early evenings either! When the radiant point is low on the horizon there is a chance to catch a legendary earthgrazer - a long, bright, slow-burning, colourful meteor that drags across the sky parallel to the horizon. Though rare, if you're lucky to see one it will stick with you forever. I was fortunate to witness one from the beach of Butterfly Valley in Turkey. It briefly turned a dark evening into mid-day and took long enough to burn its way across the sky for someone to decry 'the end of the Earth!' and nearly long enough for me to find religion!
You'll need a DSLR/mirrorless/bridge camera with a wide angle lens and a tripod. As for the settings:
- Aperture - A wide open aperture will allow more light to enter your camera. f/2.8 is a sweet spot for astrophotography, but f/4 is perfectly adequate.
- Shutter Speed - Typically 20-30 secs. Go as long as you can without the stars trailing due to Earth's rotation (check out the 500 rule)
- ISO - You'll need your sensor to be sensitive to light due to the lack of it so 1600 is a good starting point. If your camera can handle low-light high-ISO situations without too much noise in the image then you may want to push up to 3200-6400
- Focal length - Use your widest lens (I'll be going 14mm on a full-frame camera). This allows you to capture as much of the night sky as possible and improve your chances of capturing the meteors. It also allows you to use a longer shutter speed as per the 500 rule (or 300 for crop sensor)
When the moon rises you have a chance to step down your aperture to f/5.6 or lower for sharper images and as it gets higher in the sky you can bring your ISO down and get cleaner images too.
To increase your chances of catching more meteors it's a good idea to shoot continuously. If your camera doesn't have any built-in timelapse functionality then pickup a cheap intervalometer from Amazon (seriously don't spend big bucks here, the cheap ones are just as good). Leave a 2-second interval between shots to allow your sensor a little time to cool down and to make sure your camera has enough time to save the previous image to the memory card (you need to turn off your in-camera noise reduction to get the interval as low as 2 seconds).
Set your focus to infinity and you're good to go!
WHERE TO SHOOT
The further you are from light pollution the more meteors you will see. To find your nearest dark skies use a website like http://www.lightpollutionmap.info.
Go somewhere where you can have some solid foreground interest too, a popular landmark in your local area or maybe an interesting composition you found previously.
It's a common misconception that you need to be looking in the direction of the radiant point to see the meteors. This simply isn't true. Meteors will burn up all over the sky but drawing a line backwards from where they came will always point back to the radiant point. So if you point your camera in the direction of Perseus all the meteors will seemingly emanate out of the same point. If you point your camera 90 degrees to the radiant they will all be pretty much parallel to each other. Through personal experience I wouldn't advise pointing away from the radiant point, as there tends to be much less meteors in that area of the sky.
HOW TO WATCH
Once you've got your camera set up and taking continuous shots you can kick back and enjoy the show. I don't advise looking up for prolonged periods so either grab yourself a deck chair or go for my preferred method of lying down on a camping mat and taking in the full 180 degrees of night sky.
Your eyes need about 20-30 minutes to adjust to the dark so that you can see more of the fainter meteors. If you need to see what you're doing try and use a red light as this won't reset your night vision.
Be aware that the Perseid's are known to come in bursts followed by lulls of no activity so as they say... good things come to those who wait.
Take plenty of snacks, good company, and make sure you're wrapped up warm. How about a drinking game? Whiskey shot for every meteor anybody?
BEWARE LENS FOG
One problem when a hazy, humid, summer's day comes to an end is condensation. When the glass of your lens cools to below the dew point temperature it will start to mist up. To counter this you need to keep your lens warm. I use a telescope dew heater hooked up crudely to a 12V power-drill battery but you could easily use a normal lithium-ion battery.
The cheap and cheerful method is to wrap some hand warmers around your lens, though they're sometimes difficult to find being summer and all. When strapping them on be careful not to knock your lens out of focus. It's a good idea to use some masking tape to lock your focus ring once you're happy with it so that you don't accidentally move it.
EDITING THE SHOTS
Edit the shots to your taste, I'm not going to do a start-to-finish guide here but one technique I like to use for meteor showers is to take all the images with meteors and stack them in Photoshop using a 'Lighten' blending mode for the layers and some layer masks to tidy everything up. I'd advise you to only use the shots collected from the same tripod position and to get the meteors to line up with the radiant point you'll need to rotate each exposure a bit to counter-act the rotation of Earth (though if you use a star tracker they will all be lined up already). Et voila!
If you have any questions please feel free to ask away in the comments section below.
Good luck and clear skies!