Dark-sky parks worth staying up late for

Most people in North America and Europe can no longer see the Milky Way from home. Light pollution from cities spreads for tens of kilometres, washing out all but the brightest stars. A road trip is often the easiest way to see a truly dark sky again, and some parks are dark enough that all you need to do is stay up past midnight and walk away from the campsite lights.

What makes a sky dark

Three things matter: distance from cities, dry and clear air, and the Moon. Astronomers rate sky darkness on the Bortle scale from 1, an excellent dark site, to 9, an inner-city sky. Most suburbs sit around 6 to 8. Places certified by DarkSky International as dark-sky parks or reserves have both dark skies and lighting rules that keep them that way, and many run night programmes for visitors.

Where to go in the US

Big Bend in Texas, Great Basin in Nevada and Death Valley in California are among the darkest places in the lower 48 states. Capitol Reef, Bryce Canyon, Natural Bridges and the Badlands are excellent too, and several hold astronomy festivals or ranger-led star talks in summer. In the East, where dark places are rare, Cherry Springs State Park in Pennsylvania is famous among stargazers.

And in Europe

Europe's dark skies are mostly in thinly populated uplands and islands: parts of the Scottish Highlands and Galloway, the Alqueva region in Portugal, the high Pyrenees, the Westhavelland reserve near Berlin, the Austrian and Swiss Alps away from the valleys, and the Canary Islands, where some of the world's major observatories stand. In Scandinavia the summer nights are too bright for stargazing, but autumn and winter add the chance of northern lights.

When to go

Aim for the week around a new moon; a full moon washes out the Milky Way almost as much as a small town. In the Northern Hemisphere the bright core of the Milky Way is visible from about late spring to early autumn, highest around midnight in mid-summer and earlier in the evening by September. Check cloud and smoke forecasts the afternoon before, and keep a flexible night in your plan in case the first one is cloudy.

Protect your night vision

Your eyes need 20 to 30 minutes in darkness to adapt fully, and one glance at a bright screen resets the clock. Switch your headlamp to red, turn your phone to its dimmest setting or night mode, and park so that headlights and campervan lights don't shine across other people's view. Dress warmly, because deserts and mountains cool quickly after sunset, and bring a reclining chair or a mat: lying back is the most comfortable way to watch the sky.