The moon is a rock in sunlight. It looks soft in the sky, and on a camera it is a bright disk, so Umbra gives you a starting aperture, shutter speed, and ISO for the camera and lens you picked.
A full moon starts at f/11, with a shutter speed of 1 over your ISO. If ISO is 100, that is 1/100 of a second. People who shoot the moon a lot call this Looney 11.
Umbra starts one stop darker than that so the bright rim on a digital file keeps more of its shape. If you want the classic exposure, tap Brighter.
Your kit, and the spin
The rest comes from what you brought: the size of the sensor, how long the lens is, and how you hold it. On a tripod, turn shake reduction off so the head does the holding. In your hands, leave it on so the camera can take out your shake. A star tracker can take a longer shutter because it follows the sky.
Earth turns, so the moon creeps across the frame. A shorter shutter keeps the disk sharp, and that is what the motion line under the numbers is telling you.
This week, and eclipses
This week is the real moon, read from today’s date the way an almanac does, close enough for a first frame. The bright sliver of a crescent uses the same exposure as a full moon. The dark side is earthshine, and that is its own shot.
When Earth’s shadow is on the moon, switch to Eclipse and drag the moon, or tap a tick, until it matches the sky. Each tick is a real stage, and totality can be eight to fourteen stops dimmer than a full moon. Those steps come from Fred Espenak’s NASA tables. You get aperture, shutter, and ISO for every stage, so copy the list before you go.
You also see how large the moon sits in the frame with that lens.
Tonight
Take the first frame, then look at the graph on the back of the camera. After that, shoot one darker frame and one brighter frame. A deep eclipse changes the light, so trust the exposure you just made.
If you point at the sun, put a real solar filter on the front of the lens first.
This is an estimate. Check NASA's eclipse safety guide (opens in a new tab) before you go.
Where this comes from
The numbers come from Looney 11, today’s date, NASA eclipse tables, and how copper or deep red a total eclipse looks, plus the specs from the camera and lens makers. The cratered moon is a Galileo photograph from NASA/JPL. The red moon is a NASA Glenn photograph from 14 March 2025.