FORECAST GUIDE

How to read a stargazing forecast

A clear icon in a weather app is only the beginning. Good observing depends on clouds, atmospheric clarity, steadiness, moonlight and true darkness.

Cloud cover

Cloud cover is the most immediate constraint. Below 20% is promising; 20–50% can offer useful clear gaps; above 70% usually makes planning difficult. Thin high cloud may be more damaging than its percentage suggests because it spreads nearby light.

Transparency versus seeing

Transparency describes how well light passes through the atmosphere. It matters most for galaxies, nebulae and the Milky Way. Seeing describes atmospheric steadiness and matters most when observing fine detail on planets or using high magnification.

Moonlight and darkness

Astronomical darkness begins when the Sun is 18 degrees below the horizon. In high-latitude summers, that may never happen. Moonlight raises the sky background, so pair weather conditions with the Moon's phase and position.

Use the score as a starting point

No single score can describe every target. View From Sky emphasizes clouds, then adjusts for lunar illumination and visibility. Always consider local fog, smoke, streetlights and terrain before travelling.