How is the Tonight score calculated?

It scores forecast cloud, dew risk, aerosol transparency, astronomical-dark hours, nearby clear windows, and rain risk. It is weather-first — distinct from moon/Bortle scores on Sky Events.

Does this work outside Guyana?

Yes. Set any latitude and longitude. Guyana is the default demo because humid tropical nights need dew-aware scoring that still works worldwide.

Tools

Is Tonight Good for Stargazing? Free Score

One 0–100 score for tonight — Go, Maybe, or Skip — from cloud layers, dew risk, transparency, and astronomical dark.

Georgetown

6.8000°N, 58.1700°W

Tonight

Maybe

Maybe tonight — 38% cloud

38% cloud
high dew
transparency good
3.0h astro dark
moon 22% lit
clear window soon

Best clear window: tonight · 19:00–06:00 · excellent

Best night this week: Tomorrow · score 73 (Go)

Active: Perseids — simulate radiant

Full stargazing weather Check your Bortle What's in the sky Tonight by city How the score is weighted

Score bands

70–100 Go — Clear enough to drive for.
45–69 Maybe — Watch dew and gaps.
0–44 Skip — Cloud, dew, moon, or no dark window.

Frequently asked questions

Is tonight good for stargazing?: Use the Tonight score: 70+ is Go, 45–69 Maybe, under 45 Skip. It weighs cloud cover, dew risk, transparency, and whether you have astronomical dark. Open Stargazing Weather for hourly detail.
How is the Tonight score calculated?: It scores forecast cloud, dew risk, aerosol transparency, astronomical-dark hours, nearby clear windows, and rain risk. It is weather-first — distinct from moon/Bortle scores on Sky Events.
Does this work outside Guyana?: Yes. Set any latitude and longitude. Guyana is the default demo because humid tropical nights need dew-aware scoring that still works worldwide.

After the score, check your Bortle on the dark-sky map, see what’s in the sky tonight, or open a city hub under Locations.