Weather forecast for astrophotographers

This project comes from my long-time struggle to find a clean, no-nonsense weather forecast for astrophotography.

I wanted something that answers one simple question: "Is the weather good for astrophotography tonight, in the next 3 hours, or tomorrow?"

So, here it is – an ultra-minimalist weather forecast built specifically for astrophotographers.

No humidity, no precipitation, no pressure, or dew point to fuss over.

Just cloud cover, wind speed, and a simple "Ok" when conditions are good.

All information comes from Open-Meteo.com API.

• Detailed Weather Forecast: Provides temperature, cloud cover (low/mid/high), wind speed and gusts, moon illumination, and seeing index.
• Sun & Moon Calculations: Calculates sunrise, sunset, moonrise, and moonset times.
• Minimalist Interface: Focuses on relevant metrics for astrophotography, avoiding unnecessary weather details.
• Caching: API responses are cached to improve performance and reduce API calls.
• Location Suggestions: Offers geolocation suggestions for easier city selection.

• Frontend: HTML, JavaScript, Tailwind CSS (via CDN)
• Backend: Golang (net/http for web server, Open‑Meteo API integration)
• Caching: bigcache for in‑memory caching
• Geolocation: Open‑Meteo Geocoding API

• Go 1.23+

cd src
go run .

Open http://localhost:8080.

cd src
go test ./...

• GET / – HTML UI (served with embedded templates and static assets)
• GET /weather?lat=<lat>&lon=<lon> – returns a plain‑text table forecast
• GET /suggestions?q=<query> – JSON location suggestions (Open‑Meteo Geocoding)
• GET /robots.txt, GET /favicon.ico, GET /static/*

Build a Docker image from the repo root (the Dockerfile expects sources under src/).

docker build -t aweather:latest .

• The -t flag allows you to tag the image with a name and version.

Run the container and map port 8080.

docker run -d -p 8080:8080 --name aweather aweather:latest

• The -d flag runs the container in detached mode (in the background).
• The -p 8080:8080 maps the container's 8080 port to your host's 8080 port.
• The --name aweather assigns a name to the container for easier management.

• Thresholds: ok status means cloud cover ≤ 25% at all levels and wind speed/gusts < 15 km/h (see MaxCloudCover, MaxWindSpeed).
• Cache: in‑memory cache TTL is 10 minutes.
• Port: the server listens on port 8080.

The application derives a heuristic “seeing index” from available meteorological fields to help rank time slots for astrophotography. It is not a physically calibrated arcsecond value and should be interpreted as: lower is better.

• Temperature: temperature_2m, temperature_500hPa
• Wind: wind_speed_10m, wind_speed_850hPa, wind_speed_200hPa
• Heights: geopotential_height_500hPa (and site elevation)

• Compute an elevation‑aware temperature lapse across the total depth from site elevation to 500 hPa: (T2m − T500) / depth_km.
• Form a vertical wind shear proxy: |V200 − V850| + |V850 − V10| (all in m/s).
• Seeing index ∝ shear^0.6 * |lapse|^0.4. A small jet‑stream penalty applies above ~22 m/s at 200 hPa, capped to avoid runaway values.
• The result is clamped to a reasonable range for readability (≈0.5–5.0).

This index is intended for relative comparison between hours/nights rather than absolute image resolution.