How do I choose a dark site near me?

Step 1. Find a darker area on a light-pollution map

Light-pollution maps estimate how much artificial light brightens the night sky across a region. Two sources:

Look for the darkest shading you can reach in a sensible drive, then check what lies around it. A dark patch next to a large city can still have a bright horizon on that side.

• The World Atlas of Artificial Night Sky Brightness (Falchi and others, *Science Advances*, 2016). This is a modelled map of sky brightness, built from satellite data and checked against ground measurements.
• NASA's Black Marble. These are satellite images of lights on the ground at night. They show where the light comes from, not how bright the sky is above a given spot, but they make towns, highways and industrial sites easy to spot.

References[1][2]

Step 2. Put the glow behind you

Every town makes a dome of light on its horizon. Pick a spot where the brightest domes are on the side you won't be looking at.

If your target is low in the south, the southern horizon is the one that has to be dark and open. That can make a closer spot on the far side of a town better than a farther spot facing it.

Hills and ridges between you and a town can block part of its glow.

References[3][7]

Step 3. Choose a spot you can legally and safely use

The darkest point on a map may be private land, behind a locked gate, or on a road shoulder with no safe parking. Before you go:

The public stargazing spot guide covers this in detail.

Examples are International Dark Sky Places listed by DarkSky International, and National Park Service sites with stargazing programs.

• confirm night access with the managing agency;
• find legal parking;
• plan your way out.

References[4][5]

Step 4. Check the horizon for your target

Darkness doesn't help if trees, hills or buildings block the part of the sky you came for. Decide what you want to see and which direction it will be in. Then check that the view that way is open. Scout unfamiliar ground in daylight when you can.

References[7]

Step 5. Check tonight's cloud and Moon for that spot

Choose the forecast area that covers the site, not your home. A dark site under cloud, or under a bright Moon, gives a bright or blocked sky.

The Star Window's verdict for the site's area compares the forecast cloud, Moon interference and how dark the sky gets as the Sun sets for the window. Local light pollution is not in the score, so a Go at a city location and a Go at a remote site are not the same sky.

Step 6. Test the sky when you arrive

Give your eyes time to adapt, away from white light. Then judge the sky directly:

Keep notes. Your own comparisons of two or three spots on similar nights are the most useful guide to where to go next time.

• Look for the Milky Way when it is in season and the Moon is down. Seeing its dark lanes and structure is a good sign.

References[6][8]

What The Star Window does and doesn't tell you

The Star Window forecasts the conditions in your window: cloud, Moon interference and how dark the sky gets as the Sun sets. It does not yet have a sourced value for how dark each site's sky is, so it doesn't rank places by light pollution or call any place dark. Its destinations list gives access research for specific places. Use a light-pollution map for the darkness itself.