Astrophotography basics

Start with what you have

Astrophotography means taking pictures of the night sky, from simple starry landscapes to detailed views of galaxies. You do not need special gear to begin.

Many modern phones have a night or astro mode that takes several exposures and combines them automatically. Place the phone on something steady, turn off the flash and let it work for several seconds or more.

A camera with manual controls, such as an interchangeable-lens camera or an advanced compact, gives you more freedom. Shoot in raw format if you can, since it keeps much more information for later editing.

Tripod, focus and basic settings

Night photos need exposures of many seconds, so the camera must stay perfectly still. A sturdy tripod, or a phone clamp, is the single most useful purchase; a two-second self-timer or remote prevents shake when you press the button.

Autofocus usually fails in the dark. Switch to manual focus, magnify the screen on a bright star or planet, and turn the focus ring until it becomes the smallest possible point.

Turn off image stabilisation when on a tripod, and set white balance to a fixed value of about 3500–4500 K so colours stay consistent. Then take a test shot, check it zoomed in, and adjust.

Wide-field Milky Way shots

The bright core of the Milky Way lies toward Sagittarius and Scorpius. From mid-northern latitudes it is best seen roughly from March to October, rising in the early morning in spring and standing in the south in the evening in summer.

You need a truly dark site and a moonless sky. Use the widest lens you have, roughly 14–24 mm on a full-frame camera, at its widest aperture, such as f/2.8 or lower.

Start with ISO 3200 and an exposure of about 15–20 seconds, then adjust. A tree, rock or building in the foreground turns a sky photo into a scene with a sense of place.

The 500 rule and the NPF rule

Because Earth turns, stars drift across the frame. Expose too long and they become short streaks instead of points. Two rules of thumb tell you the longest safe exposure.

The 500 rule says: divide 500 by your lens's focal length. With a 20 mm lens on a full-frame camera, that is about 25 seconds; on a smaller crop sensor, first multiply the focal length by the crop factor, about 1.5 or 1.6.

Today's high-resolution sensors show trailing sooner, so many photographers prefer the NPF rule. It also takes the aperture and the size of the sensor's pixels into account, and usually gives a shorter time, often about half of the 500 rule. Free calculators and apps work it out for you; in practice, take a test shot and zoom in.

Photographing the Moon

The Moon is lit by full sunlight, so treat it like a daytime subject. Use a low ISO of about 100–400, an aperture of about f/8, and a fast shutter speed of about 1/125 to 1/500 second.

A telephoto lens of 200 mm or more makes the Moon fill a useful part of the frame. Phones can do well when held to a telescope or binocular eyepiece with an adapter.

The most detail appears along the terminator, the line between day and night on the Moon. Craters there cast long shadows, so a half Moon often looks better than a full one.

Stacking and tracking mounts

Every photo contains noise, a grainy speckle that hides faint detail. Stacking means taking many identical frames and letting software line them up and average them; the real signal adds up while random noise smooths out.

A star tracker is a small motorised mount that turns the camera at the same speed as the sky, cancelling Earth's rotation. It allows exposures of minutes instead of seconds, revealing nebulae and galaxies, but it must be aligned with the celestial pole.

Bigger telescopes on computerised mounts open up even more, but they take time to learn. Most experienced astrophotographers recommend mastering a camera, a lens and a tracker first.

Processing basics

Processing brings out what the camera captured. In any photo editor, start by setting the white balance, then gently raise contrast and lower the black point so the sky looks dark but not crushed.

Use noise reduction carefully, since too much makes stars look like smudges. Small adjustments to clarity and colour saturation can bring out the dust lanes of the Milky Way.

Aim for a natural result. Keep your original raw files, so you can return to them as your skills improve, and compare with photos from trusted sources such as NASA or ESO for realistic colour.