About NightSeam
Built around your observing site.
A browser planner for finding deep-sky targets that suit your night and skyline.
Planning on your device.
Astronomy calculations run in your browser. Saved sites, equipment and horizons stay in browser storage.
A project with a clear focus.
NightSeam plans observing nights in your browser. There is nothing to install and no account to create.
Data sources and credits
NightSeam ships 12,176 catalog objects, with a fixed Standard list of 200 well-known targets.
- Catalog: OpenNGC by Mattia Verga (CC BY-SA 4.0), plus a small supplement of objects OpenNGC cannot carry.
- Images: online object photos are sourced through Wikipedia and Wikimedia Commons. Credit belongs to the original image creators. Individual author, source and license details are available with each photo. Photos load when you open an object and are cached in your browser. The software’s MIT license does not cover third-party photos.
- Weather: Open-Meteo, forecast and air-quality services, loaded on demand or with the optional automatic-weather setting; weather data © Open-Meteo.com.
- Saved planning data: sites, rigs, custom targets and horizons stay in browser storage. Weather requests send your active site’s coordinates and timezone to Open-Meteo. See Privacy.
- License: the planner is free to use and its software is MIT licensed; OpenNGC catalog data is CC BY-SA 4.0.
Connection requirements
Astronomy calculations run on your device: object positions, Sun and Moon positions, twilight times and usable observing windows. The planner combines them with your site, date, equipment and skyline. Weather forecasts and new external photos use separate online services.
Load the planner and its catalog online first. You can continue planning in the loaded tab while disconnected, but offline reopening or reloading is not guaranteed. Saved planning data is specific to your browser and site address; export a JSON backup before clearing browser storage or moving to another device.
Questions or feedback?
For a problem report, include the planner version (shown under About in the planner’s ☰ menu), browser and steps to reproduce. Share only the site or backup data you want the recipient to see.