Freeze a moment in cosmic time: taking pictures of the night sky is easier than you think.
A Foot in the Door
The easiest astrophotos to take are simple twilight scenes with bright planets or the Moon strategically included. You can do this with some of the better smartphones. Some apps enable you to take longer-than-normal exposures, and using a tabletop bracket to stand and aim your phone, you can take "nightscape" astrophotos with enough size and quality to promote on social media. You just set up the camera and let it run.
You can even take relatively good closeup photos of the Moon and bright planets with your phone, using one of the many adapters available to hold the phone to the eyepiece of your telescope.
If you'd prefer pictures with enough size and quality for printing, you may want to step up to a pocket digital camera. Most of these point-and-shoots, mounted on a tripod, can take excellent twilight and star-trail photos with low noise. Their large detectors (10 megapixels and up) are plenty for prints. Many point-and-shoot cameras can shoot for 15 seconds or longer in a single exposure--enabling you to begin to record the Milky Way from a dark-sky site, automate a meteor patrol, or capture a bright aurora in progress.
The only problem is that point-and-shoots are going the way of the dinosaurs; cell phones are making them obsolete. But this also means that new models now sell for rock-bottom prices, and you can find used cameras even cheaper.
If your thirst for more has been awakened, consider a DSLR camera. These are designed to be as versatile as possible. The latest models have relatively low noise even in dim light at ISO speeds of4800 or higher. This means you can record colorful images of the Milky Way that are far deeper than possible with a pocket camera using similar exposures. Although autofocus and image-stabilized lenses are today's standard for everyday use, they're not needed for astrophotography. Most DSLRs use the same lens mounting system as film cameras once did, so you can use high-quality old lenses from the days of film that can be purchased at low cost.
DSLR cameras also accept a wide variety of accessories that are useful for astrophotography, including a cable release, a T-adapter that couples your camera directly to your telescope in place of an eyepiece, and an external power supply so the battery doesn't die in a long shoot.
DSLR cameras may soon be superseded by another advance: the Mirrorless Reflex Camera. These have all the benefits of DSLRs but are smaller, lighter, and mechanically simpler. They make full-time use of the large LCD screen and eliminate the unnecessary bulk of a viewfinder and mirror. These cameras require an adapter if you want to attach older interchangeable lenses, but otherwise they perform nearly as well as their DSLR brethren.
Next: Add Sky Tracking
So far we've been talking about fixed cameras mounted on a table or a tripod. All such cameras are limited to exposures of around 30 seconds even with wide-angle lenses. This is because Earth turns. In longer exposures, Earth's rotation causes the stars, planets, and everything in the sky to become streaks.
But if you add a tracking head to your tripod and align it with Polaris, the North Star, your camera will now follow the sky like a tracking telescope. Long exposures of 3 to 5 minutes become possible under a dark sky, recording the faintest extensions of the Milky Way complete with colorful nebulosity and rich star fields. You can also use lower ISO speeds when shooting tracked exposures, which enables you to take smoother pictures with less noise.
Onto the Telescope
Do you have a tracking telescope? If so, take out its eyepiece, insert your DSLR or mirrorless camera using a T-mount adapter, and now you're starting to play with the big boys. A telescope without its eyepiece is just a very large, very-long-focus telephoto lens. If it's on a tracking mount, you can combine dozens of modestly long exposures (a few minutes or less) in your computer using stacking software to produce even deeper images. For deep-sky astrophotography, combining long exposures reduces noise and reveals fainter objects. Suddenly, your pictures can start to show the nebulous wisps beyond the Trapezium in the Orion Nebula, or resolve stars down into the center of M13.
The Graduate Level
The next step is to move up from a DSLR to a specialized CCD camera for imaging deep-sky objects, or to a more expensive high-speed video camera for the planets.
A CCD detector chip is more sensitive to dim light than are the CMOS detectors of consumer cameras. A CCD camera is a specialized instrument using a digital detector for astrophotography, usually with built-in cooling to increase the detector's efficiency. A CCD camera also records images in a way that enables you to precisely measure the brightnesses of objects, allowing you to start producing actual scientific-quality data from your images.
Depending on how deep you dive into astrophotography, there's always a learning curve. Fortunately, there are plenty of online tutorials that can put you on the path to producing great astrophotos. You can find lots of help at SkyandTelescope .com/astronomy-resources/astrophotography-tips, and you can Google "astrophotography tutorials" for more. I've made three video webinars at SkyandTelescope.tv (click Online Classes) that can help you get the most out of your images using popular software, including the ever-present Adobe Photoshop. And each month Sky & Telescope features an article on astrophotography that will help you master the nuances.
So however deep you want to go, it's never been easier to test the waters. And who knows, you may quickly find for yourself how fun it is--and soon be sending me images for our readers' photo gallery.
S&T imaging editor Sean Walker enjoys shooting everything from Earth's upper atmosphere out to infinity. Have you taken a beautiful astrophoto? Send it to gallery@SkyandTelescope.com.
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|Title Annotation:||Equipment: Basic Astrophotography|
|Date:||Jan 1, 2015|
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