How do you start stargazing with just your eyes?
Naked-eye stargazing needs a dark place and some patience more than any equipment. Give your eyes half an hour or more away from bright light, and pick a site and a night with little artificial light and little moonlight; the same sky will then show many times more stars.
How long your eyes need to adjust to the dark
Step outside from a lit room and the sky at first shows only a handful of stars. The retina has two kinds of light sensors: cones, which see colour, and rods, which handle dim light. Cones adapt to darkness in about 9 to 10 minutes; rods take much longer, and they do not reach their full sensitivity for a long time after that. NASA notes that it can take half an hour or more for your vision to become fully sensitive.
Rods depend on a pigment called rhodopsin. Bright light bleaches it almost instantly, and rebuilding it is slow. One glance at a phone screen or a passing car's headlights resets much of the progress, and the wait starts again. A fully dark-adapted eye is somewhere between ten thousand and a million times more sensitive than it is in daylight, so the waiting is worth protecting.
A simple routine helps: set up first, then spend the first twenty or thirty minutes looking at the sky without checking a bright screen. Dark adaptation is also faster and deeper in younger people, so older observers may simply need to give it a little more time before judging how dark the sky really is.
Why a red light protects your night vision
You still need some light in the dark: to read a star chart, find a thermos, or avoid tripping. The reason observers use red light rather than white is that rods are almost insensitive to long wavelengths. Under dim red light, rhodopsin is bleached far less, so the night vision you waited for survives.
A dedicated astronomy torch is not required. A head torch with a red LED mode works well, and an ordinary torch can be covered with a few layers of red cellophane or red tape. Keep it just bright enough to see the page or the ground. Even red light, if it is too bright, causes glare that hides the faintest stars again.
The same principle applies to phones. Turn the screen brightness to its minimum and switch on any red or night display mode the device offers. In a group, avoid pointing any light, red or not, at other people's faces.
Choosing a site: light pollution and the Bortle scale
City lighting scatters off dust and molecules in the air and brightens the whole night sky. About 83 percent of the world's people live under light-polluted skies, and roughly a third of humanity can no longer see the Milky Way from home. When the background sky brightens, faint stars simply drown in it.
Astronomers describe sky darkness with the Bortle scale, which runs from class 1, the darkest, to class 9, an inner-city sky. Under a class 1 sky the faintest stars visible to the naked eye are around magnitude 7.6 to 8.0; under a typical city sky of class 8 the limit falls to about 4.1 to 4.5. By around class 7 the Milky Way is nearly or completely invisible. Each magnitude step means a star about 2.5 times fainter, so a few magnitudes add up to a very large difference in visible stars.
Distance from town matters most. NASA suggests travelling roughly 20 to 30 miles, or about 30 to 50 kilometres, beyond city limits and aiming for a site around Bortle class 3 or 4. The horizon in the direction of a city glows, so choose a spot where the part of the sky you want lies away from it. Look for open views, no streetlights in direct sight, and a place you can safely stay after dark.
How moonlight changes what you can see
The Moon is by far the brightest object in the night sky; at full phase its apparent magnitude is about −12.7. Its light spreads across the whole sky, and on a full-moon night a dark rural site can look much like a light-polluted suburb, with the Milky Way and faint stars washed out. You can drive away from city lights, but not from moonlight, so choosing the date matters as much as choosing the place.
The Moon runs through its phases in about 29.5 days. The darkest skies come in the days around new Moon, when it is close to the Sun and out of the night sky. A full Moon rises around sunset and stays up all night, and each following day the Moon rises roughly 50 minutes later. That means that in the week after full Moon, the early evening is dark again before the Moon comes up.
A bright Moon does not rule out observing. Bright stars, the planets and the Moon itself all show well in moonlight. For a beginner, a night when only the brighter stars show can even make the main patterns easier to pick out.
Weather, timing and staying warm
Cloud is the biggest variable. Besides cloud cover, check humidity, wind, haze and, in some regions, wildfire smoke, all of which NASA lists as worth watching. Particles in the air scatter light, brighten the background sky and dim stars near the horizon in particular. Nights after rain are often unusually sharp.
The sky is not dark right after sunset. Full darkness arrives only when astronomical twilight ends, once the Sun is well below the horizon; how long that takes depends on your latitude and the season. Stars low on the horizon shine through a much thicker layer of air, so they twinkle more and look dimmer. The same star is best seen when it is high.
Temperatures drop after dark, and standing still makes you feel the cold quickly. Bring a layer more than the season seems to need, plus a hat and gloves. A reclining chair or a mat on the ground makes a long session far more comfortable than standing with your head tipped back.
A plan for the first night: bright stars first, then patterns
On the first night it helps to have an order rather than a long target list. Start by working out north, south, east and west. Then pick out the few brightest points in the sky. Finally, look for the large patterns those bright stars belong to, such as the Big Dipper in the northern sky for mid-northern observers, or the Southern Cross for observers in the Southern Hemisphere.
For faint things, use averted vision: look slightly to one side of the object rather than straight at it. The centre of your vision is packed with cones, while rods are most densely concentrated around 20 degrees away from it. A faint star cluster or the texture of the Milky Way often appears more clearly when your gaze is held just off it.
Before you go out, set the date, time and your location in the Sky view to see which objects will be up and in which direction. Tapping an object there brings up a card with its name and a short description, which makes it easy to match a bright point you saw outdoors with what it actually is. Binoculars and telescopes can wait; they are far more rewarding once the large shapes of the sky are familiar.
Try it in the simulator
- Preview tonight's sky →Shows the stars, planets and Moon above your location tonight, and in which direction.
- Tonight's Moon →Shows tonight's lunar phase and where the Moon sits in the sky.
- Find the Big Dipper →Highlights Ursa Major and the Big Dipper and how high they stand tonight.
FAQ
- Should a beginner start with binoculars?
- Learning the large patterns by eye first tells you where to point binoculars, which makes them far easier to use. Once you know your way around, even ordinary binoculars show Jupiter's large moons, star clusters and double stars that the naked eye cannot.
- Why do photos show more stars than my eyes do?
- A camera can gather light for several seconds or longer and add it up in one frame, while the eye cannot accumulate light that way. The same sky therefore shows fainter stars and more colour in the Milky Way in a photograph than it does to the eye.
- Is stargazing pointless in a city?
- No. Bright stars, the planets and the Moon show well from a city. Choosing a park or a spot shielded from direct streetlights by buildings or trees noticeably increases the number of stars you can pick out.
Related reading
- Object Moon
- Object Milky Way
- Object Ursa Major
- Guide How do you find Polaris and true north in the night sky?