Estimate how moon phase and altitude wash out deep-sky targets so you can pick darker nights for imaging from any pin.
Frequently asked questions
When is moonlight a problem?
A high, bright Moon raises the sky background and hides faint nebulae and the Milky Way. New Moon or a Moon below the horizon is cleaner.
Does a low Moon still matter?
A low Moon lights less of the sky. This tool weights altitude so a full Moon on the horizon scores milder than one near zenith.