Your First Steps in Sky Photography (Continued)

Start Shooting

One of the first types of sky photos that I recommend you shoot — and one of the easiest — is a long ex-posure showing star trails. These portraits use a fixed camera to capture streaks of stars as Earth rotates during the night. And while digital technology has made many aspects of photography much easier, early digital cameras tended to create very “noisy” images if exposures were more than a few seconds long. Modern versions allow exposures of 30 minutes or so (if the battery lasts), but hours-long star trails remain the forte of film cameras.

To get started, load your camera with color daylight film (ISO 200 or 400), aim it skyward, open your lens aperture nearly all the way, focus on infinity, set your timer, and trip the shutter. If you’ve pointed the camera northward, toward Polaris, the stars near the celestial pole will produce a concentric pattern of streaks. Point the camera toward the east or west, near the celestial equator, and you’ll get streaks straight across your frame.

The longer your exposure, the longer the trails — and the brighter your sky — will appear. Illuminations from a city, the Moon, or the waning dusk will brighten the sky enough to make the landscape appear in silhouette. In fact, even a seemingly dark rural sky will appear brighter in a long-exposure photo — the result of a natural atmospheric phenomenon called airglow. And you can add your own light by firing the camera’s flash to illuminate the foreground, using a flashlight to “paint” nearby objects, or shining your car headlights on the scene during your exposure.

This extra light can be a good thing; seeing star trails over a silhouetted or illuminated landscape is far more interesting than just the trails themselves. If you expose for more than just a few minutes, however, even in complete darkness, you’ll want to keep the sky from becoming overexposed by reducing the light entering the lens. Stop down the lens from fully open (usually a setting of f/2.8) to perhaps f/5.6 or f/8, de-pending on your sky brightness. Since it’s impossible to predict how your scene and film will work to-gether, this requires a bit of experimentation, so take good notes.

Shooting Shooting Stars

After you become proficient at producing star trails you can use this technique to photograph countless other subjects in the sky. One of the most fun -- and challenging -- targets is a major annual meteor shower. Two of the most prolific are the Perseids in mid-August and the Geminids in mid-December.

Keep in mind that meteor photography is a crapshoot; no one can foretell exactly when and where to take a successful photo. And even if you see a meteor zip through the region you’re aimed at, there’s no guaran-tee that your camera will actually record it.

To improve your odds of capturing something, aim your camera about 45 degrees from the shower’s radiant (the constellation for which the shower is named) and about 45 degrees up from the horizon. With a high ISO — 800 or 1,600, for example — take exposures of 4 or 5 minutes with your lens wide open.

This is a great situation to use a digital camera. Its “instant replay” lets you make sure the exposure is good before shooting as many frames as you like. Later you can examine each frame for meteor streaks among the star trails and discard all the “empty” ones.

A Sky Photographer’s Best Friends

Just as astronomers recoil from nighttime light of any kind, sky photographers embrace it with passion. In fact, some of the most beautiful and naturally appearing sky photos are produced with the help of moonlight or twilight.

Once again, digital cameras have the edge, because moonlight or twilight exposures are difficult to pre-dict in advance and a camera’s light meter may not work effectively in such situations. Try various expo-sures, check the results on the viewing screen, and keep shooting until you get just what you want.

Perhaps the most exciting time for sky photography is during the hour after sunset (or before sunrise), when the celestial palette can take on a multitude of hues and textures. But during twilight the sky changes quickly so you’ve got to be ready for action.

For example, around the end (or beginning) of civil twilight — usually a half hour or so after sunset (or before sunrise) — the sky takes on a look that’s perfect for shooting the crescent Moon over an unusual foreground — especially when the Moon’s paired with the brilliant planet Venus (good evening opportuni-ties for this will pick up next year).

But don’t put your camera away just yet. About an hour after sunset (or before sunrise), you’ll experi-ence the end (or beginning) of nautical twilight. This is when the heavens take on a beautiful, deep blue color and the stars just begin to turn on their lights. This is a perfect time to photograph constellations, planets among the stars, and Earth-orbiting satellites. After twilight, the Moon can illuminate distant mountains, canyon walls, or just your backyard while the stars or clouds shine above. Keep in mind that moonlight can overpower the image, so you should usually shoot away from the Moon and carefully monitor the exposures.

The Sky Awaits

Few things are as wondrous as watching the glorious sky, and capturing it to share with others. And since the sky is constantly changing, every photo you take will be unique. But it also means that there may never be a perfect exposure in sky photography. So take several exposures at different shutter speeds — called bracketing — longer and shorter than what you think will be the right one and choose your favorite later. In fact, now that you’ve completed this entire article, I can share with you the well-guarded secret to taking that one “perfect” sky photo: shoot 100 and discard 99!

Remember: if you can see it, you can photograph it. So get out there and start shooting. With the right gear, preparation, and effort, you’ll soon be creating spectacular celestial portraits of your own.

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Dennis Mammana (mammana@skyscapes.com) is a nationally syndicated newspaper columnist and author of six books on popular astronomy. Visit his Web site at www.skyscapes.com for more examples of spectacular scenes you can capture with basic equipment.

© 2006 Reprinted with permission from Sky Publishing Corp.