About StargazingTime

Is tonight a good night for stargazing? In five seconds you have the answer for your zip code.

Why this exists

The existing tools astronomers use — Clear Sky Chart, Astrospheric, Clear Outside — are extraordinary, but they were built for hobbyists who know what a Bortle 4 sky or 70% transparency means. For everyone else (campers, photographers, parents who want to show kids the Milky Way), those interfaces are a wall of dense charts.

We compress the same signals into one number. The score is honest: it names which factor is dragging it down, and it tells you when the sky is actually dark tonight.

How the score works

Score = 10 minus weighted penalties for five components:

• Clouds (35%) — forecast cloud cover from NOAA HRRR (3 km grid in the United States, updated hourly).
• Moon (25%) — illumination at your latitude, computed on the fly with SunCalc. A full moon kills faint nebulae.
• Light pollution (25%) — Bortle 1–9 estimate based on distance from major population centers. Drive 1–2 hours to escape.
• Humidity (10%) — high humidity = haze and condensation on lenses.
• Visibility (5%) — atmospheric clarity in km.

Only the astronomical-dark hours are scored (between astronomical dusk and dawn). Daytime gets nothing — there's nothing to score.

Data sources

• Open-Meteo (NOAA HRRR for US, ECMWF/ICON globally) — refreshed every 30 minutes for 120 US cities, served from our database.
• SunCalc — moon and twilight calculations, no external request needed.
• LightPollutionMap.info — basis for our heuristic Bortle estimate.

Privacy first

We do not store your GPS coordinates. Location is read in your browser and used only to look up the nearest pre-fetched city. See our privacy policy for the full breakdown.

Roadmap

• Email alerts when your location scores 8+
• City-level SEO pages for the top 100 US dark-sky destinations
• Meteor shower countdown and photography tips
• Photographer mode with twilight timeline + exposure suggestions
• Spline 3D Hero scene

Get in touch

Found a bug, want to suggest a feature, or want to contribute data? Email hello@stargazingtime.com or visit our contact page.