Moon Simulator
The Moon as your camera will see it — phase, libration, size and the features along the terminator — for any moment from anywhere.
Moon over
How to read it
The Moon keeps one face toward us, but it rocks: libration in longitude and latitude tips up to about 8° of the limb regions into view and out again over the month, which is why Mare Orientale or Mare Humboldtianum are there one week and gone the next. The simulator computes the physical ephemeris (Meeus, ch. 53) for the moment you pick, projects the maria, craters and landing sites onto the disc, shades the night side from the sub-solar point, and then turns the whole thing so that up means what it means in your viewfinder — the zenith — or celestial north for a telescope view. The lens line tells you how many pixels the disc will fill; the sharpness limit is the exposure at which the sky's drift smears it by a pixel on a fixed tripod.
FAQ
- Why does the Moon look tilted compared with a photo I took last month?
- Two reasons: the parallactic angle (the Moon rotates in the frame as it crosses the sky — rising, culminating and setting all show a different "up") and libration. Set the same date and time and the simulator will show the same tilt your photo has.
- What is the best phase for craters?
- Anything but full. Along the terminator the Sun is low and every crater throws a long shadow; at full moon the light is flat and only the ray systems (Tycho, Copernicus) stand out. Step a day at a time and watch the terminator sweep across the list of features.
- How do I get a big Moon in the frame?
- A long lens: at 400 mm on full frame the disc is about 600 px wide on a 24 MP sensor; at 50 mm it is 75 px. The size also changes with distance — a perigee full moon is 14% wider than an apogee one.