How Do You Read a Moonrise and Moonset Table?

A moonrise and moonset table is a list of local clock times, computed for one specific set of coordinates, telling you when the Moon crosses the horizon on each date. The U.S. Naval Observatory's Astronomical Applications service publishes this kind of data for Sun and Moon rise, set, and transit along with phase dates. Once you know what the columns mean, the table answers the planning question most observing guides only hint at: is the Moon in my sky tonight, and for how long.

The columns you will actually see

• Rise — the time the Moon's upper edge reaches the horizon.
• Transit (sometimes "upper transit" or "meridian passage") — the moment it is highest, due south from mid-northern latitudes. This is the best-placed moment of the night for looking at the Moon itself, because you are looking through the least atmosphere.
• Set — the time it drops back below the horizon.
• Phase or illuminated fraction — how much of the disk is lit, often given as a percentage or a named phase.

A table with no location on it is useless. Rise and set times depend on latitude and longitude, so a generic figure copied from a news article can be wrong by hours for your city. Always generate the table for your own coordinates, which USNO's forms let you do directly.

Why the times slide later each day

The Moon moves eastward against the background stars as it orbits Earth, completing its cycle of phases in about 29.5 days according to NASA's Moon Phases explainer. Earth's rotation then has to "catch up" to that shifted position, so each successive moonrise happens later than the one before — typically by something in the neighborhood of three quarters of an hour, varying with your latitude and the time of year.

That daily slide produces the one table feature that confuses almost everyone: a blank entry. If moonrise on one date lands close to midnight, the next calendar day can go by without a moonrise inside it. Nothing is wrong with the table. The event simply fell outside that 24-hour box.

Horizon, elevation, and why your Moon is late

Astronomical rise and set times are conventionally computed for an ideal, level, unobstructed horizon at the observer's position. Real horizons have ridges, tree lines, and buildings. If your eastern view is blocked by a hill, the Moon will appear noticeably later than the printed time, and the difference grows the shallower its rising angle is that night. Treat the table as the earliest possible time rather than the moment to walk outside.

The same caution applies to the printed illuminated fraction. A table gives the percentage lit, but not how the terminator will look, which is what determines whether craters show relief. NASA's Scientific Visualization Studio publishes an hour-by-hour Moon phase and libration visualization for 2026 that shows the actual appearance, including the slow nodding of libration that tips the limb regions in and out of view.

Turning the table into a plan

A workable routine for one night:

1. Pull rise, transit, and set for your coordinates and date.

2. Note the illuminated fraction, then decide what you are observing — bright Moon for lunar detail, or dark hours for faint objects.

3. Find the window when the Moon is down, if deep-sky viewing is the goal. That window is the gap between set and the next rise.

4. Check the transit time if the Moon itself is the target.

For which phase suits which target, see which Moon phase is best for observing and what time of night the Moon is actually up. For fitting all of it around weather and twilight, our observing-night planning guide covers the rest of the sequence.