About NightSkyCast
NightSkyCast (nightskycast.com) is a free website that tells stargazers and astrophotographers whether tonight will be clear, at what hours, and where to go for a dark sky. It works in English, Russian and Lithuanian, on phones and computers, without an app or an account.
What it shows
- Hour-by-hour cloud cover split into low, mid and high clouds, on a map and for any point.
- A 0–10 night score and the best clear window for each of the next nights.
- Light pollution on the Bortle scale (classes 1–9) with an estimated SQM value.
- Moon phase, moonrise and moonset, astronomical darkness, dew risk, wind gusts and seeing.
- ISS passes, meteor showers, eclipses and other sky events; places and night-sky photos shared by users.
Where the data comes from
- Weather forecast: Open-Meteo (CC BY 4.0), which combines national weather models such as ECMWF, ICON and GFS. When zoomed in, several models are blended.
- Light pollution: estimated from NASA VIIRS night-light satellite imagery (2016), including the glow of cities within about 100 km.
- Sun and Moon: calculated on your device with the open SunCalc algorithm.
How the night score works
The score starts at 10 and goes down for clouds (low clouds count most, thin high clouds least), a bright Moon above the horizon, rain risk, strong wind and twilight. 7 or more means a great night, 5–7 a decent one with clear windows, below 3 is usually not worth going out. It is a forecast, so it is most reliable for the next 24–48 hours.
Price
The map, night reports, city pages and guides are free. Optional Plus and Ultra plans (via Patreon) add an AI assistant that answers questions about a specific night and a daily email “Is tonight worth going out?” for your saved place.
Who makes it
NightSkyCast is an independent project made in Lithuania by amateur astronomers. Questions, ideas and bug reports: [email protected] or the “Write to us” button on the site.