Wednesday night and Thursday night, we'll witness the peak of the Perseid meteor shower. If you haven't already chosen a dark site from which to watch the event, try this interactive Light Pollution map. Click and drag your mouse to center your location and then scroll to zoom in. Heavily polluted areas are tinted pink, red and yellow. Aim for areas colored blue, olive-green and gray.
With the map in front of you, click anywhere and an info box pops up. In it there's a heading labeled "Bortle." This refers to the Bortle Scale, used by astronomers to characterize sky darkness. The scale ranges from "1" (ultradark skies) to "9" for the inner city. A typical rural sky rates a "3" on the Bortle scale.
Wherever you are, the best way to photograph meteors is with a digital SLR or one of the newer mirrorless cameras. You'll also need a tripod to mount the camera so it sits absolutely still during the exposures. A wide-angle lens is essential because you never know exactly where a meteor might appear. Lenses with focal lengths from 35 mm to 15 mm work great.
Frame a scene that includes mostly sky with maybe trees, hills or buildings at the bottom of the frame to add a sense of place. During the early part of the evening face the camera east, southeast or northeast. At 3 or 4 a.m., try pointing south, north or northwest. Then follow these steps:
1. Set both the lens and camera mode dial to M (manual) because you'll be manually focusing and exposing. If you're out early, another option is to use autofocus on the crescent moon in the western sky. Once focused, be sure to move the lens switch back to M.
2. If moon's not available, use the camera's "live view" feature (see your manual) and the magnifying glass button to manually focus on a bright star. Once done, you're set for the night. Just be careful not to bump the focus. Some people like to tape the lens barrel to secure it
3. Open up your camera lens to allow in the maximum amount of light. On the barrel, you'll see a series of numbers: 2.8, 3.5, 4, 4.5, 8, 11, 16. Turn the barrel to the smallest number. On my lens, that's 2.8.
4. If you can "open up" to 2.8, set the ISO to 1600, but if your largest aperture is 4 or 4.5, use ISO 3200. From heavily light-polluted areas, dial back to ISO 800.
5. Set the exposure time to 30 seconds, then gently press the shutter button and let go. Afterward, check the back viewfinder screen. Is the photo clear with lots of stars showing? Good! If not, refocus if necessary or adjust the ISO..
6. Press again to take another picture . . . and again . . . and again to your heart's content. If you have an intervalometer — a remote shutter release that automatically triggers the shutter — you can use it to do the picture-taking while you take it easy. eBay is a good source for intervalometers.
7. If you live in an area prone to dew, rubber-band a pair of chemical handwarmers around the lens barrel, otherwise the lens may fog up within an hour. If you don't have handwarmers, you can use a portable hairdryer to periodically warm the lens.
8. After you're all finished, carefully look through your images for meteors. Occasionally, you'll see pin-like, symmetrical lines. These are likely digital artefacts. Meteor trails are typically narrower at one and wider at the other and show color.
It is possible to photograph meteors with some of the better mobile phone cameras that can take up to 30-second time exposures. If you have one of these, tilt it skyward, secure it and snap away.
I wish you all dark and meteor-filled skies! And if you're lucky enough to catch one, please share it with us on Facebook.
"Astro" Bob King is a freelance writer for the Duluth News Tribune. Read more of his work at duluthnewstribune.com/astrobob.