Stargazing With Binoculars: What 7x50 and 10x50 Mean and What You Can See
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How we wrote this: A guide based on basic optics, NASA skywatching resources and the U.S. National Park Service night-skies program (sources below). We have not personally tested these products. Professor Ploof is an AI-generated character and doesn't use or endorse any product.
Before buying a telescope, try binoculars. They're quick to use, show a wide patch of sky, and stay useful for birds and travel if astronomy doesn't stick.
Reading binocular numbers
A pair labelled 7x50 has 7x magnification and front lenses 50 mm across.
- Magnification makes things look closer, but it also magnifies hand shake.
- Objective size (the second number) sets how much light is collected. Bigger gathers more light but adds weight.
- Exit pupil is the objective size divided by the magnification: 50 ÷ 7 ≈ 7 mm, and 50 ÷ 10 = 5 mm. It's the width of the beam of light that reaches your eye. In the dark your pupils widen, and a larger exit pupil gives a brighter-looking view, although how wide pupils open varies from person to person and with age.
Common astronomy choices
- 7x50: bright, wide, steady views. Easy for beginners and kids.
- 10x50: more magnification and still a manageable weight. Shake is more noticeable.
- Larger "giant" binoculars (such as 15x70) need a tripod.
(Look for: 10x50 binoculars for astronomy) (Look for: 7x50 binoculars)
Keep them steady
- Lean on a car roof, a fence or a wall.
- Lie back in a reclining chair and brace your elbows.
- Use a tripod adapter if your binoculars have a threaded socket.
(Look for: binocular tripod adapter)
Let your eyes adjust
Your eyes become much more sensitive after time in the dark. Many observers allow 20 to 30 minutes. Use a red light to read charts, because white light resets your night vision. Dark skies make a big difference too. The National Park Service has a night-skies program that protects natural darkness in parks, and many parks hold astronomy events (NPS Night Skies).
(Look for: red light headlamp)
Beginner target list
- The Moon: craters and the dark "seas." It's easiest to see detail away from full Moon.
- The Pleiades: a bright, compact star cluster that looks better in binoculars than by eye.
- The Milky Way: under dark skies, sweep along it and watch it break into countless stars.
- Jupiter's moons: when Jupiter is up, steady binoculars can show up to four small points of light beside it.
- The Andromeda Galaxy: a faint, oval smudge from a dark site in autumn.
NASA's skywatching pages describe what's visible each month (NASA Skywatching).
The safety rule
Never look at the Sun through binoculars without a proper solar filter covering the front lenses. NASA warns that doing so instantly causes severe eye injury (NASA, Eclipse Viewing Safety).
When to move up to a telescope
If you're finding targets easily and want more detail on planets or fainter galaxies, read our first-telescope guide. Your binoculars will still be handy as a wide-field finder.
Sources
- NASA, "Skywatching": https://science.nasa.gov/skywatching/
- NASA, "Eclipse Viewing Safety": https://science.nasa.gov/eclipses/safety/
- National Park Service, "Night Skies": https://www.nps.gov/subjects/nightskies/index.htm