Moonless Night Planner: Dark Hours, Cloud Forecast & Calendar
Find observation windows that fit your local hours, Sun and Moon limits. Compare two locations, add a MET Norway cloud forecast and export calendar events.
Moon & Clear-Night Planner
Astronomy runs locally. Weather is optional and uses a cached public forecast; forecasts do not cover arbitrary historical or distant future dates.
Supported scope: 1–14 nights · 2000–2100 astronomy · five-minute midpoint resolution · two locations · geometric flat horizon · no light-pollution, terrain, meteor or seeing prediction.
Your inputs
Required fields are marked with an asterisk.
Your result
Review your output, then save it to your device.
Make the next step clear.
Your findings, assumptions and next steps will appear here after you run the check.
Moon & Clear-Night Planner · https://nightplan.kitforma.com/ · KitForma
Local time zones and DST
Moon and darkness intersection
Calendar and evidence downloads
Understand the evidence.
Focused guides explain the rules, the edge cases and the checks worth doing before you act.
Find moonless hours that fit your night
Intersect availability, darkness and the Moon instead of relying only on a phase icon.
Read the guide ↗Field guide / 02Combine a cloud forecast with dark hours
Keep known cloud estimates separate from missing weather data.
Read the guide ↗Field guide / 03Compare observation locations and calendar times
Use equal preferences while preserving each location’s local clock.
Read the guide ↗Before you start
What makes a window qualify?
It must fall inside your local available hours, the Sun must be below the selected altitude, and either the Moon is below your geometric horizon limit or its illuminated fraction is within your allowance. If weather is enabled, a known forecast cloud value must also pass your cloud limit.
Does a new Moon automatically mean a good night?
No. The Sun, local hours, cloud cover, terrain and light pollution matter too. The planner calculates where the Moon is and its illuminated fraction. It does not model sky brightness or promise that a particular faint object will be visible.
How do overnight hours and daylight saving work?
An interval such as 20:00–04:00 belongs to the local date on which it starts. IANA time-zone rules handle skipped and repeated clock hours. Calendar exports use UTC instants, so an eight-hour wall-clock interval can be seven or nine elapsed hours on a DST transition.
What if the weather is missing?
Missing periods remain unknown. They never pass the cloud filter. An unavailable provider still allows the astronomical calculation and evidence export, but the tool does not claim any cloud-qualified windows for periods without data. Turn weather off explicitly if you want an astronomy-only plan.
Are window times exact rise and set events?
No. Conditions are sampled at five-minute slot midpoints. Displayed starts and ends are planning estimates with one-slot boundary uncertainty. The calculation uses a geometric flat horizon and no atmospheric refraction or local terrain model.
What leaves my browser?
Without weather, coordinates and astronomical calculations stay in the browser. With weather enabled, coordinates rounded to 0.01 degrees are sent to KitForma’s caching gateway and MET Norway. No device geolocation permission is requested. Downloaded evidence includes your selected locations, so review it before sharing.
Sources & assumptions
Formats, algorithms and supported features are documented below. Check the stated scope and inspect your output before using it.
- Astronomy Engine ↗
MIT-licensed Sun/Moon positions and illumination; pinned 2.1.19.
- MET Norway Locationforecast ↗
Optional forecast cloud fraction with source times.
- MET Norway licensing ↗
Weather data credited under CC BY 4.0; transformed fields disclosed.
Reviewed 2026-10-19. Read our methodology or report an issue.