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The author took this image of star trails above observatory domes from near San Pedro de Atacama, Chile, looking toward the South Celestial Pole. Credit: Molly Wakeling
I got started in astrophotography in July 2015, when I received my first telescope as a gift: an 8-inch Schmidt-Cassegrain on an altitude-azimuth mount. After nearly falling over, seeing Saturn for the first time, I decided I must attach a camera to the telescope somehow so I could share that beauty with the world.
Astrophotography is often associated with expensive telescopes, robotic mounts, and highly technical challenges. But getting started can be easier than you think: All you need is a basic DSLR and a tripod.
Star trails
Images of star trails are stunning and easy to make. Start with your DSLR and a short-focal-length lens (a stock 18–55mm zoom lens at 18mm is perfect) on a tripod, and pick an area of sky. Capturing the motion of stars as they wheel around the celestial poles is particularly mesmerizing, so facing north (or south, in the Southern Hemisphere) is a good place to start. A nice foreground, such as a barn or a tent or even a distant tree line or mountain, will make for a captivating image.
In Manual mode, set the exposure time to 30 seconds and choose a relatively high ISO, such as 1600 or 3200. Use the widest f/stop, or stop down one or two if you are using a very fast lens, such as f/1.8. If your camera has a built-in multiple-exposure mode, use that to trigger it. If not, an intervalometer is an indispensable tool for all kinds of astronomy purposes. Intervalometers can be programmed to activate the shutter for you (rather than you manually depressing the shutter button), including in Bulb mode, where you can set an arbitrary exposure time. You can get an intervalometer for around $20.
Take long exposures — 15 to 60 seconds to avoid saturation — for at least one hour, although you can go all night. I recommend taking images in JPEG format for ease of processing, or you can convert raw shots to JPEGs later.
Processing star trail images is simple through free software called Startrails (www.startrails.de). Simply load all the photos, press the Startrails button, choose the mode, and watch the magic. You can import the final image into Photoshop or another image processor to tweak colors, contrast, and other details.
Time-lapse videos
This same technique can be used to take time-lapse videos of objects rising or setting, such as the Milky Way, the constellation Orion, or a crescent Moon. In this case, choose a short enough exposure that the stars don’t trail as much. (Fifteen seconds is good for an 18mm lens.) Otherwise, use the same the settings and technique as for star trails.
There are many free and paid programs to turn individual frames into a video. A favorite of mine is TimeLapse DeFlicker ($35 at www.timelapsedeflicker.com), which smooths variation in light between exposures. Add some space-themed music for a fun video of the night!
Nightscapes
Nightscape (or skyscape) images are wide-field shots of the night sky with a fascinating foreground, such as mountains, buildings, or anything else you might think of. Nightscape photos are best taken in raw format and from dark locations, far from cities.
A fast camera lens, such as a 14mm f/2, can capture the Milky Way rising using a single 20-second exposure. For an even more stunning image, photographers might take a single long exposure of the foreground — say 30 or 60 seconds, while lighting the landscape in some way — and then take several 15-second exposures of the sky to keep the stars from trailing. Stacking software can align and combine the sky exposures into one bright, high-contrast image; the photographer then replaces the sky in the foreground frame with the stacked sky frame.
Eight years after my first astroimaging experience, I now run four automated imaging rigs in my yard, with even bigger plans for the future. And I am thrilled to start sharing my knowledge and love of astronomy here!
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