AstroPlanner Web

A horizon-aware deep sky object planner for visual observers and astrophotographers — now in the browser.

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A browser-based port of AstroPlanner, the cross-platform desktop app. Runs entirely client-side with no server required — install it as a PWA and it works offline.

→ Open the app

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What it does

AstroPlanner Web tells you what's worth observing tonight and exactly how long you have to observe it. It loads the full NGC/IC catalog, computes each object's altitude throughout the night against your custom horizon profile, and scores every object based on how long it clears your horizon. Pick a night, set your location, and get a ranked list you can actually trust — no account, no server, no install required.

Features

Planning

• Horizon-aware visibility — define a custom horizon profile (azimuth/altitude pairs) to account for your tree line, rooftop, or observatory walls
• Visibility scoring — each object is scored by how long it clears your horizon at a useful altitude, weighted for object size and sky conditions
• Yearly best-time heatmap — month-by-month strip showing the best observing windows across the full year
• Observation date picker — plan ahead for any night

Catalog

• NGC and IC objects from the embedded OpenNGC catalog
• Filters — narrow by object type (galaxies, nebulae, clusters, double stars), favorites, or visible-only
• Search — find any object by name or catalog ID

Telescope & FOV

• Imaging setup manager — define telescope + camera combinations with focal length and sensor dimensions
• FOV overlay — interactive sky view powered by Aladin Lite with your field of view overlaid on real DSS imagery
• Best setup suggestion — highlights the setup whose FOV best fits the target object
• Fill percentage — shows how much of the frame the object fills for each setup

Object detail

• Sky survey image — DSS2 color thumbnail via CDS HiPS2FITS
• Altitude plot — full-night arc showing rise, transit, and set against your horizon
• Moon interference — phase and angular separation at peak visibility
• Favorites & imaging log — mark objects as favorites or record when you imaged them
• Simbad / AstroBin links — one-click access to reference data and community images

Offline / PWA

• Progressive Web App — install to your home screen on mobile or desktop
• Full offline support — the catalog, app code, and assets are cached at install time; planning works without a network connection
• Sky survey images require an internet connection (fetched live from CDS)

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Built with

Language	C# / .NET 10
UI framework	Blazor WebAssembly — runs entirely in the browser via WASM
Astronomy math	AASharp — port of Jean Meeus' Astronomical Algorithms
Sky viewer	Aladin Lite v3 embedded via iframe
Survey images	CDS HiPS2FITS — DSS2 Color
Catalog	OpenNGC by Mattia Verga (bundled, CC BY-SA 4.0)
Local storage	Blazored.LocalStorage
CSV parsing	CsvHelper by Josh Close
Hosting	Cloudflare Pages

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Running locally

Requires the .NET 10 SDK.

git clone https://github.com/tankhardrive/AstroPlannerWeb.git
cd AstroPlannerWeb
dotnet run --project AstroPlannerWeb/AstroPlannerWeb.csproj

Then open https://localhost:5001 in your browser.

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Deployment

Every push to main triggers a GitHub Actions workflow that builds the app with dotnet publish and deploys the output to Cloudflare Pages automatically. See .github/workflows/deploy.yml.

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Desktop version

Looking for the full desktop app with weather forecasting, comet tracking, Stellarium integration, and more?

→ AstroPlanner (desktop) — Windows, macOS, and Linux

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Credits

Built by tankhardrive with the help of Claude Code by Anthropic.

Third-party data

The bundled NGC/IC catalog (AstroPlannerWeb/wwwroot/data/NGC.csv) is OpenNGC, created by Mattia Verga and contributors, and licensed under CC BY-SA 4.0. This data is not covered by the MIT license that applies to the AstroPlanner Web source code.

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License

MIT — see LICENSE for details.