will be visible from soon after it rises, at 00:13, until soon before it sets at 14:33.

At this time in its monthly cycle of phases, it appears almost exactly half illuminated.

The Moon orbits the
Earth once every four weeks, causing its
phases to cycle through new moon, first quarter, full moon, last quarter, and back to new moon once
every 29.5 days.

As it progresses through this cycle, it is visible at different times of day.
At last quarter, it rises in the middle of the night and appears high in the sky by dawn.
It sets at around lunchtime. More information about the Moon’s phases is available
here.

Observing the Moon at last quarter

Over coming days, the Moon will rise later each day, so that it is visible for
less time before sunrise and rises less far above the eastern horizon before dawn.
By the time it reaches new moon, it will rise at around dawn and set at around
dusk, making it visible only during the daytime.

Its daily progress is charted below, with all times are given in
Orlando local time.

A thin crescent

The months around the autumn equinox –

September and October in the northern hemisphere

– present the best opportunity to see a very thin crescent Moon
immediately before sunrise in the days running up to new moon.

This comes about because the Moon appears higher in the dawn sky sooner
after new moon in the autumn months as compared to other times of year.

At all times, the Moon lies close to a line across the sky
called the ecliptic, which is shown in yellow in the planetarium above. This line
traces the path that the Sun takes through the zodiacal constellations every year, and
shows the plane of the Earth’s orbit around the Sun. Since all the planets circle the
Sun in almost exactly the same plane, they too move across the sky following the same line.

When the Moon is widely separated from the Sun, it is separated from it
along the line of the ecliptic. But, at different times of year, the ecliptic meets the horizon
at different angles at sunrise. This means that a
certain number of days after new moon, the Moon appears at different
altitudes above the horizon at different times of year.

At sunrise, the ecliptic makes its steepest angle to the horizon at the autumn equinox – in September
in the northern hemisphere, and in March in the southern hemisphere. Conversely, it meets the horizon at its
shallowest angle at the spring equinox. And so, very thin crescent moons are most visible in the dawn sky
in the autumn.

The inclination of the ecliptic plane to the horizon at Orlando varies between 84° (sunrise at the autumn equinox) and 38° (sunrise at the spring equinox). On October 6, the ecliptic is inclined at 84° to the eastern dawn horizon.

The exact moment of last quarter

The exact moment of last quarter is defined as the time when the Moon’s ecliptic longitude is exactly
90° away from the Sun’s ecliptic longitude, as observed from the center of the Earth. However,
the Moon does not appear in any way special at this instant in time, and a last quarter moon can be observed
at any time in the pre-dawn sky.

At the moment it reaches last quarter, the Moon’s distance from the Earth will be 398,000 km. Its celestial coordinates will be as follows:

The coordinates above are given in J2000.0.

The sky on 6 Oct 2023

Source

The circumstances of this event were computed using the DE430 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).

This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location.

Related news

Image credit

Simulated image courtesy of Tom Ruen.