How to get started with DSLR astrophotography

When we think of astrophotography, usually big telescopes on robotic mounts that cost thousands of dollars come to mind. But you can capture beautiful astrophotos a different way — with only a camera and a tripod.

I created one of my first astrophotos on a work trip, on the side of the highway outside Albuquerque, New Mexico, with a lowly Nikon D3100, its kit 18-55mm lens, and a 6-inch tripod. I took nineteen 15-second images at ISO 6400 (and accidentally in JPEG!), stacked them using the beginner’s stacking tool DeepSkyStacker, and got an exciting Milky Way shot that blew me away.

Time, practice, and use of the astrophotography software PixInsight have improved the quality of such images for me, but it’s a good reminder of the incredible shots that can be captured without any tracking mount, telescope, or special camera. Be sure to capture images in the RAW format for the best quality. You can also try this with longer focal-length lenses (100mm or more, using shorter exposure times to prevent star trails), occasionally adjusting the tripod to keep the target centered, for smaller areas of the sky like the core of the Milky Way, the Orion Nebula (M42), or the field around the Andromeda Galaxy (M31).

Under a dark sky, single-exposure nightscape images are another exciting way to capture what’s overhead. A fast-focal-ratio lens (f/2.8 or lower) collects a lot of light, and some careful post-processing in Photoshop or PixInsight to increase contrast, reduce noise, and correct color can make a captivating astrophoto. Some cheaper lenses have a lot of chromatic aberration and coma when shot wide open, but one of my favorite affordable nightscape lenses with few of these issues is the Rokinon 14mm f/2.8. With some chromatic aberration correction in Photoshop, my even less-expensive Nikon NIKKOR 35mm f/1.8G has also delivered some fantastic shots.

Another type of image to create with just a DSLR and a tripod is a star-trail image. While they may appear as though the photographer just left the shutter open for a few hours, that actually would create an oversaturated image. Instead, using an intervalometer (which runs about $20 online), you capture 15- to 60-second exposures at somewhere between ISO 800 and 3200 for a few hours. These can be obtained in either JPEG or RAW. Then, using software such as the free Startrails application (startrails.de), you combine all the exposures to create a single image that shows the stars trailing across the sky. Having something interesting in the foreground can make a more compelling image, and facing the celestial pole showcases the wheel-like motion of the sky.

Focusing at night can be a challenge. One way to focus is to use a bright astronomical light, such as the Moon, Venus, or Jupiter, or even a distant streetlight. With a bright enough target, you can use the Live View camera function and digitally zoom in on the light, then adjust the focus manually (turn off autofocus!) until it’s as sharp and small as possible. When such bright sources are absent, I usually take a three-second exposure, and then adjust the focus ring until the stars look pixelated — this is how you know you’ve reached focus. For fully manual lenses, the infinity focus mark on the lens is usually accurate. Lenses that have autofocus are a bit trickier to find infinity manually, but using short exposures and guess-and-check will get you there.

You don’t need a fancy telescope or mount to get started in astrophotography! There’s a lot you can do with just a DSLR and a tripod, even with inexpensive lenses. All you need is an intervalometer, a dark sky, and a sense of adventure