How good are the stars tonight?
Humans have gazed at stars for millennia — from ancient Stonehenge to modern telescopes. The best viewing comes during new moons and in dark-sky preserves away from city lights.
Matching is flexible with typos and alternate spellings — if your exact town isn't found, try the nearest larger city.
If both fields are filled in, they're used instead of the city lookup above — otherwise leave them blank.
Under a truly dark sky, the human eye can see roughly 2,500 stars at once — but from a typical city, light pollution can cut that number down to just a few dozen.
As an Amazon Associate we earn from qualifying purchases.
We do our best to link products that we genuinely believe are organic, no disposable junk, sustainable, and built to last.
Enter your city and a date, and we pull two of the three factors from real data automatically: the moon's actual illumination percentage for that night, and the forecast cloud cover for your location. You still tell us your light pollution level yourself, since there's no reliable free data source for that yet. These three combine into an overall rating from Poor to Perfect.
The lunar cycle significantly affects what you can see in the night sky. During a new moon, the sky is darkest, making fainter objects like distant galaxies, nebulae, and meteor showers more visible. A full moon washes out everything but the brightest stars and planets. This calculator pulls the real moon illumination percentage for your chosen date and location rather than asking you to guess the phase.
The Bortle Scale is commonly used to measure light pollution, from Class 1 (pure natural darkness) to Class 9 (inner-city sky). There isn't yet a reliable free public data source that maps light pollution to a specific location, so this calculator asks you to select your general light pollution level yourself — city, suburban, rural, or dark sky preserve. Cloud cover, on the other hand, comes from a real weather forecast for your chosen date and location: even thin cirrus clouds can significantly reduce what you can see through a telescope, so the forecast is factored directly into your score. Forecasts are typically only available roughly two weeks out — for dates beyond that range, cloud cover can't be scored yet.
The hours between midnight and dawn typically offer the darkest skies and best viewing. Also check for special celestial events like meteor showers (Perseids in August, Geminids in December), lunar eclipses, and planetary alignments. Dark sky preserves, national parks, and rural areas away from cities offer the best conditions — some well-known areas include Cherry Springs State Park in Pennsylvania, Big Bend in Texas, and Mauna Kea in Hawaii. For the best experience, use a red flashlight to preserve night vision, bring warm clothing even in summer nights, and consider binoculars or a telescope for enhanced viewing.
Example: Say you enter "Seattle" for tonight, and select Suburban light pollution (60). If the moon is showing about 10% illumination tonight (a near-new moon, scoring 90) and the forecast shows 20% cloud cover (scoring 80), the overall score is (90 + 60 + 80) ÷ 3 = 76.7, rounded down to 76/100 — landing in the "Great" range where most celestial objects should be visible.
A bright moon washes out faint light from distant objects the same way streetlights wash out stars in a city. A new moon gives you the darkest sky, making galaxies, nebulae, and meteor showers far more visible than during a full moon. This calculator pulls the real moon illumination for your date automatically, so you don't need to know the phase yourself.
The Bortle Scale measures sky darkness from Class 1 (pure natural darkness) to Class 9 (inner-city sky). This calculator's Light Pollution options are a simplified version of that same idea — city, suburban, rural, and dark sky preserve. Unlike moon phase and cloud cover, there's no reliable free data source that maps light pollution to your specific location yet, so this one field stays manual — you select the option that best matches where you'll be.
Even thin, high clouds can block the faint light from distant objects. For serious stargazing, aim for nights with less than 50% cloud cover — anything heavier will noticeably limit what you can see, even with a telescope. This calculator pulls a real forecast for your date and location automatically.
Weather forecasts are only reliable roughly two weeks into the future. If you pick a date further out than that, cloud cover can't be scored yet — the calculator will still show you the real moon phase and factor in your light pollution selection, but will flag that the cloud portion of the score isn't available until the date is closer.