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Interactive · Dark Sky

Light Pollution Simulator

Dim the valley. Bring back the stars.

Slide, switch and shield the lights of a little mountain valley, and watch the glow over town fade, the Milky Way rise and the fireflies return, live as you play.

Start Playing What the Controls Do

The Valley at Night

Every light in the valley follows your settings. Try one slider at a time, then try a preset.

A stargazer with a telescope under a starry sky, with domes of light pollution glowing on the horizon

Five choices, one sky.

The valley starts with typical outdoor lighting: bare bulbs, full brightness, blue-white light and every light on all night.

An illustration based on a simplified model, not a lighting measurement.

What the Controls Do

Each control matches one of the five principles for responsible outdoor lighting

Shielding

A fully shielded fixture hides the bulb and sends light only downward. It removes uplight and glare and keeps light out of the neighbor's window. Principle: targeted.

Brightness

Use only as much light as the task needs. Less light on the ground means less light reflecting into the sky. Principle: low level.

Light Color

Blue-white light scatters more in the atmosphere and affects more wildlife. Warm white around 2700 K, or amber, brightens the sky less. Principle: warm-colored.

Light Switches

Some lights do nothing useful at night, like floodlights aimed up a steeple or a sign lit for no one. Switching them off is free. Principle: useful.

Timers & Sensors

Light when it is needed, dim or off when it is not. In the simulator, timers switch off the ballfield and porch light late at night. Principle: controlled.

Stars & the Bortle Scale

The readout estimates how many stars you could see and the sky's Bortle class, from 1 (pristine) to 9 (inner city). The numbers come from a simplified teaching model.

Bring It Home

From the simulator to your own back porch

Dark-Sky-Friendly Lighting

The five principles explained, with fixture and bulb tips and a checklist you can try tonight.

Read the lighting guide →

Lighting Self-Check

A quick, playful quiz about your own outdoor lights, with a score and your top fixes.

Take the self-check →

Dark Sky Consulting

Light pollution education and consulting with astronomer Stephan Martin.

About consulting →