Astrophotography without equipment

Twenty years ago, taking a photograph of a star required a telescope, a tracking mount, a cooled CCD camera, and a laptop. The cheapest setup that produced anything worth showing cost thousands of dollars and required learning some real astronomy. As of around 2020, all of that changed. A modern smartphone, propped on a fence in a moderately dark location, can capture an image of the Milky Way that would have required a small observatory in the 1990s.

This is not a hyperbole. The phone you’re carrying right now, if it’s roughly the last four or five years of either iPhone or Google Pixel, has a camera capable of genuine astrophotography. The capabilities are limited compared to professional gear, but they’re so far beyond anything an amateur could do thirty years ago that it’s worth knowing what’s possible.

What works

Stars and constellations are easy. A long exposure of even a few seconds with a phone on a tripod will capture hundreds of stars per frame, far more than you can see with your unaided eye. The Milky Way in a dark sky is achievable with a 15-second exposure on a recent phone, no problem. Star trails — those long curved streaks you see in photographs taken over an hour — are easy if you stack many short exposures.

The Moon photographs beautifully. The full moon is so bright that you can shoot it with normal daytime settings and pick up real surface detail; craters, the dark seas, the bright ray system around Tycho. A phone with a zoom lens can pull this off without any equipment beyond the phone itself.

The International Space Station shows up as a bright streak across long exposures during a pass. Aurora, when it’s strong, photographs well with a 3 to 5 second exposure.

What doesn’t work

Anything fine — planets, galaxies, faint nebulae — is hard or impossible without a telescope. You will not see the rings of Saturn or the bands of Jupiter from a phone photograph. The Andromeda Galaxy will appear in a long exposure, but as a small smudge, not the spectacular spiral you see in published photos. The planets show up as bright dots, not as little discs. Star colors mostly come out as white due to sensor characteristics.

The threshold separating “easy from a phone” and “needs a telescope” is roughly: anything that looks like a point of light to the human eye is photographable; anything that requires magnification to see structure is not.

The technique

Three things matter. Your phone needs manual control over exposure, it needs to hold absolutely still for several seconds, and it needs to focus on infinity.

Most modern phones have a manual or “pro” camera mode. Look for it. The settings to use as a starting point: ISO between 800 and 3200 (higher means more sensitivity but more noise), shutter between 10 and 30 seconds, focus manual at infinity, and white balance around 3500 to 4000 Kelvin to avoid the orange cast you get from automatic balance in low light.

Recent iPhones have a built-in Night Mode that activates automatically in low light. Hold the phone steady when the countdown appears. It’s not as good as manual control, but it’s good enough for casual stargazing photos.

Recent Pixels have something better: Astrophotography mode activates inside Night Sight when the phone detects it’s on a tripod, pointing at dark sky. The phone takes 15 separate 16-second exposures and stacks them internally, producing a 4-minute total exposure with low noise. The results, especially under dark skies, are genuinely impressive.

For Android phones with manual mode and no astro automatic, the trick is the same as the iPhone manual approach — set the ISO, set the shutter, focus at infinity, and rely on the tripod.

Stability

This part is non-negotiable. A phone that moves by even a millimetre during a 20-second exposure produces blurred stars. You absolutely need a tripod or a stable surface. A cheap phone tripod costs about fifteen dollars and is the best money you can spend if you want to take this seriously.

Without a tripod, propping the phone against a wall or on a rock works in a pinch, but you have to be careful that the camera lens has a clear view of the sky and isn’t tilted. Most phone cameras are not at the geometric center of the phone, so propping the phone flat on its back doesn’t always work the way you’d expect.

Also: use a 3-second self-timer instead of pressing the shutter directly. Just touching the screen makes the phone wobble for a moment, and the resulting shake is visible in a 15-second exposure. The self-timer eliminates this entirely.

The 500 rule

If your exposure is too long, stars start trailing — turning into short arcs instead of dots — because the Earth rotates during the exposure. The traditional rule for figuring out the maximum exposure is the 500 rule: divide 500 by your lens focal length in 35mm-equivalent terms to get the maximum exposure in seconds.

For a phone wide lens (around 25mm equivalent), the math gives roughly 20 seconds. For a phone telephoto lens (75mm equivalent), it’s about 7 seconds. Beyond those, you’ll see noticeable star trails. Within them, you get point stars.

Some people use the 300 rule for stricter results on high-resolution sensors. Phones are forgiving and 500 works fine for casual shots.

Stacking, the cheating trick

The real magic, if you want quality close to what amateurs with much more expensive gear achieve, is stacking. The principle: take many short exposures of the same patch of sky, then use software to align them and add them together. The signal (real stars) adds up linearly, while the noise (sensor randomness) adds up as a square root. The result of stacking 20 exposures of 20 seconds is closer to a single 400-second exposure than to a 20-second exposure, with much less noise.

Free software does the heavy lifting. DeepSkyStacker for Windows, Siril cross-platform, or Sequator for simpler aligning. Take 20 to 50 exposures of the same patch of sky, dump them in, and let it run. The first time you see a stacked result you’ll wonder how the same phone could produce such different images.

The Pixel astro mode does this internally, which is why the Pixel results look so good — it’s doing 4 minutes of stacking automatically, in the camera app, without you knowing.

A final tip

The camera doesn’t need your eyes dark-adapted. But you do. After 20 or 30 minutes outside without looking at any white light, you can see far more sky detail than you could at minute zero, which means you compose better photos because you actually know what’s in your frame. Worth waiting for.