Tuesday, March 25, 2014
Solutions: Tracking The Sky
How to use a tracking mount to get phenomenal starry night photos with your DSLR
Capturing star streaks is actually pretty easy. The most important things to have are a sturdy tripod and good technique. Star trails that rotate around a single point are aimed at polar north. This is the point around which the sky rotates. Note, when your goal is a big circle of star trails, you have to be pointed north if you're in the Northern hemisphere. Choose a wide-angle lens to capture a good amount of sky, as well as some of the Earth. You should be doing this on a night with little, if any, moon and no artificial light. You'll be shooting one very long exposure (or combining several long exposures), and your foreground will get blown out if the moon is up or artificial lights are on.
With the composition set, open your lens to its maximum aperture. If you need to stop down for depth of field, do so, but shoot at the maximum aperture you can. With a wide-angle lens, you really should be able to shoot wide open unless you're trying to include something quite close to the camera in the frame. Set the ISO at 100 and the shutter speed at B (Bulb). You need more than an hour to get the full effect of polar star trails. If your camera can't do a single exposure that long or if it creates excessive noise, you need to shoot a series of shorter exposures and combine them with software (DeepSkyStacker is a popular freeware option). You'll find that you probably need to experiment with ISO and aperture settings to get the stars to the brightness you want.
If you want to try to "see deeper" into the night sky, try working with a racking mount. Motorized mounts for large telescopes are expensive, but you can use a much smaller and less costly model for a DSLR. With this kind of setup, you can get a beautiful wide-field image. You won't be shooting with any terrestrial foreground when you're working this way. It's true astrophotography. What you will be able to do is shoot for longer than 30-second exposures while maintaining pinpoint stars. This allows you to use longer exposures that will, in turn, reveal fainter stars and other celestial objects.
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