About this page
Tonight’s moon, drawn in your browser: the current lunar phase and its name, the share of the disc that is lit, the moon’s age in days, and the dates of the next full moon and next new moon. The drawing follows the real terminator, so the crescent thins and the gibbous swells exactly as the sky does.
Questions
How is the moon phase computed?
From the mean synodic cycle: the moon returns to new every 29.53 days, so the page measures the time since a reference new moon and reads the phase off that cycle, entirely in your browser. The real orbit is slightly elliptical, so the result can differ from precise astronomical tables by a few hours — never enough to mistake the phase itself.
What does the illumination percentage mean?
The share of the moon’s visible disc that is currently lit by the sun — 0% at new moon, about 50% at the quarters, 100% at full moon.
What is the moon’s age?
The number of days since the last new moon. A full cycle takes about 29.5 days: first quarter arrives near day 7, full moon near day 15, last quarter near day 22.
Why does the moon look flipped from the southern hemisphere?
The page draws the moon as seen from the northern hemisphere, where a waxing moon lights up from the right. South of the equator the same moon stands the other way up, so the lit side appears mirrored.
More instruments: İstanbul’s twilight and sun times, a fullscreen clock, a blank page to write on, a word counter, a breathing exercise and noise & nature sounds — or see all the tools.