Stargazing and Dark Skies: Why Astronomers Use Red Light
How to enjoy the night sky, why light pollution matters, and why stargazers use dim red light to protect their night vision.
On a clear, dark night, thousands of stars appear. But bright lights spoil the view, and stargazers have habits to protect it.
Dark adaptation
Your eyes need about 20 to 30 minutes in darkness to become fully sensitive. A single flash of white light can undo much of that. See our article on how your eyes adjust to the dark.
Why red light
Astronomers often use dim red light to read charts and adjust equipment. Red light affects the dark-adapted eye's sensitivity much less than white light, so they keep their night vision.
A phone flashlight gives white light, so it doesn't share that benefit. If you need light while stargazing:
- Use it as briefly as possible.
- Point it at the ground, away from your eyes and others'.
- Dim the light by covering the LED with a layer of cloth.
- Let your eyes readjust for a few minutes afterwards.
Light pollution
Light pollution is artificial light that brightens the night sky and hides stars. In cities, only the brightest stars and planets are visible. In dark rural areas, the Milky Way may stretch across the sky.
To see more:
- Move away from towns and street lights.
- Choose a moonless night, as bright moonlight washes out faint stars.
- Pick a clear, dry night.
Stargazing etiquette
If you're at a shared site:
- Keep lights off or very dim.
- Never shine a light towards the sky or other people.
- Warn people before switching on any light.
- Avoid using phone screens at full brightness. Reduce brightness or use a dark mode.
What to bring
| Item | Why |
|---|---|
| Warm clothes | nights get cold |
| A blanket or reclining chair | comfort for looking up |
| A star chart or app | to identify constellations |
| A dim red light | for reading charts |
| Binoculars | many objects look better through them |
Easy targets
- The Moon: craters through binoculars.
- Bright planets such as Venus and Jupiter.
- Constellations such as Orion, visible in the northern winter.
- The Milky Way in dark places.
Enjoying the dark
The best stargazing often means less light, not more. Use your torch to move safely, then switch it off and look up.
Night Torch
A simple, reliable flashlight app for night-time use
More about Night Torch
Charging Your Phone During a Power Cut: Power Banks, Cars and More
Practical ways to keep a phone charged when the mains is off, and how to stretch the battery you have.
Read article →Dark Mode and Night Settings: Comfortable Screens After Dark
How dark mode, brightness controls and night-light settings can make your phone easier on the eyes at night, and what they can and can't do.
Read article →Looking After Your Phone Battery: Habits That Make It Last
Simple, evidence-based habits to keep a phone battery healthy for longer, without myths.
Read article →Power Bank Safety: Choosing and Storing One for Emergencies
What to look for when buying a power bank, how to use and store it safely, and how it supports your phone torch.
Read article →