How to Use Sun/Moon Dark Window
Find nights when the Sun is down and the Moon is dark enough for deep sky.
What this tool answers
When are the best astronomical-night windows at my location, after twilight, with Moon below the horizon or thin enough not to dominate?
When to use it (Guyana)
Near 6°N, twilight is short compared with high latitudes. Moonrise/set still decide imaging weeks. Plan Milky Way core runs and ISS photography around darker windows; use this calendar before booking travel.
Step-by-step
- Open Sun/Moon Dark Window.
- Confirm location and date range.
- Find nights with long dark stretches (Sun down + Moon down/faint).
- Note start/end times for packing and travel.
- Cross-check Stargazing Weather for cloud on those nights.
How to read the results
- Dark window length: usable hours for DSO / MW / trails.
- Moon phase & altitude: a thin crescent low in the west can still leave a dark eastern sky.
- Twilight ends: when true night starts for your latitude.
Common mistakes
- Planning only by "new Moon weekend" without checking local Moonrise.
- Arriving at nautical twilight and leaving before the best hours.
- Ignoring that humidity + Moon glow hurts contrast even more on the coast.
Next
- Topics: Earth's Motion, Moon Phases
- Tools: Stargazing Weather, Milky Way Season Planner