What Is This?
Dark Sky Planner helps photographers plan nighttime shoots of the Milky Way by showing when darkness, a moonless sky, and the galactic core align at any location on a chosen date.
Quick Start
- Click or tap anywhere on the map to drop a location pin
- Use the date picker to choose your target night
- Read the panels — solar times, moon status, Milky Way window
- Check the quality badge for an at-a-glance summary
- Use the Calendar (📅) button to scan across an entire month
Understanding the Results
Quality ratings:
| Excellent | Long dark & moonless window, galactic core well above horizon |
| Good | Solid window with minimal moon interference |
| Fair | Shorter window or partial moon influence |
| Poor | Very short usable window or significant moonlight |
| No Window | No viable window (full moon, or location/season has no true darkness) |
The Night Timeline: Visual bar showing twilight phases (civil → nautical → astronomical → night), moon presence, and the Milky Way shooting window in cyan. Hover or tap any segment for exact times.
The Shooting Window: The intersection of three conditions: astronomical darkness + moon below horizon + galactic center ≥15° altitude. All three must overlap.
About the Data & Confidence
High confidence:
- Solar/twilight times use Jean Meeus' Astronomical Algorithms (via SunCalc) — accurate within ~1–2 minutes of official USNO values
- Galactic center altitude/azimuth uses astronomy-engine (VSOP87-grade precision, arcsecond accuracy)
- Moon illumination and phase are reliable for planning purposes
- Timezone detection uses an embedded database — no network call needed
Useful heuristics (not physical laws):
- The 15° minimum altitude for Milky Way "visibility" is a rule of thumb. Near the horizon, atmospheric haze often obscures the core even when the math says it's up.
- Quality score thresholds (what makes a night "Good" vs "Fair") are reasonable defaults, not universal standards.
What this app does NOT model:
☁️ Weather — clear skies are assumed
⛰ Local horizon — mountains, trees, or buildings blocking your view
🌆 Light pollution variation — the overlay is VIIRS/NASA 2024 data at ~2.4 km resolution and won't reflect new developments or seasonal changes
🌫️ Atmospheric transparency or seeing conditions
Data Sources
- All astronomical calculations run locally in your browser — no data leaves your device
- Map tiles: CartoDB, OpenStreetMap, Esri (loaded on demand as you pan/zoom)
- Light pollution overlay: VIIRS/NASA Light Pollution Atlas 2024
- Location search (optional): OpenStreetMap Nominatim geocoding API