The Moon – 29 December 2025
Key Scientific Data
Object type: Earth's natural satellite
Date of observation: 29 December 2025
Local time: 21:23
Phase: Waxing Gibbous Moon
Moon age: 9.6 days
Illuminated fraction: 72.1%
Distance from Earth: 361,863 km
Apparent diameter: 33′ 00.65″
Physical diameter: 3,474.8 km
Magnitude: –11.39
Phase angle: 63° 45′
Albedo: 0.12
Orbital velocity: 1.067 km/s
Sidereal orbital period: 27.32 days
Synodic period: 29.53 days
Light-travel time: approximately 1.2 seconds
Description
This image shows the waxing gibbous Moon on 29 December 2025 at 21:23 local time, when it was 9.6 days old and 72.1% illuminated.
At the exact time of the photograph, the Moon was approximately 361,863 kilometres from Earth, giving it an apparent diameter of 33′ 00.65″ — slightly more than half a degree across the sky.
The Moon was waxing, meaning that its illuminated portion was increasing night after night as it progressed towards Full Moon.
Most of the visible lunar hemisphere was already in sunlight, but the terminator still crossed a substantial part of the surface. This combination makes the waxing gibbous phase particularly rewarding for lunar observation: the broad illuminated region reveals the great maria and highlands, while the low-angle sunlight along the terminator dramatically emphasises craters, mountains and other surface relief.
The Terminator – Where the Landscape Comes Alive
The irregular boundary separating lunar day from lunar night is known as the terminator.
Near this line, the Sun lies very low above the lunar horizon. Crater rims and mountain peaks can catch the first rays of sunlight while nearby valleys and crater floors remain in darkness.
The resulting long shadows create the strong impression of depth visible in the photograph, transforming what might otherwise appear to be a flat disc into a genuine landscape.
This also explains why Full Moon is not necessarily the best phase for studying lunar topography. When the Sun illuminates the surface more directly, shadows become much shorter and many relief features are less pronounced.
At 72.1% illumination, the Moon offers an excellent combination of a large illuminated surface and strongly defined terrain along the terminator.
The Lunar Maria
The large, relatively smooth dark regions visible across the Moon are known as the lunar maria, from the Latin word for “seas”.
Early telescopic observers believed that these enormous dark areas might actually contain water. We now know that they are vast plains of ancient basaltic lava.
Billions of years ago, enormous impacts excavated large basins and fractured the young lunar crust. Molten material subsequently rose from the Moon's interior and flooded many of these depressions before cooling and solidifying.
The brighter regions surrounding them are predominantly the ancient lunar highlands. These are generally older and much more heavily cratered than the maria, preserving some of the earliest geological history of the Moon.
A Surface Shaped by Impacts
The countless craters visible across the lunar surface are the scars of billions of years of impacts by asteroids, meteoroids and other Solar System debris.
On Earth, geological activity constantly modifies the surface. Weather, erosion, oceans and plate tectonics gradually erase or transform ancient impact structures.
The Moon is very different.
With virtually no atmosphere, no rain, no rivers and no active plate tectonics, its landscape evolves extremely slowly. Many impact structures can therefore remain visible for billions of years.
The lunar surface is consequently a remarkably well-preserved geological archive of the early Solar System.
Why Does the Moon Change Shape?
The phases of the Moon are not caused by Earth's shadow.
At any moment, approximately half of the Moon is illuminated by the Sun. What changes during the lunar month is how much of that illuminated hemisphere is visible from Earth.
At 21:23 on 29 December 2025, the visible lunar disc was 72.1% illuminated.
Because the illuminated fraction was greater than 50% but less than 100%, the Moon was gibbous. And because that illuminated fraction was increasing towards Full Moon, it was waxing.
Hence the astronomical description of the phase seen in this photograph:
Waxing Gibbous Moon.
Why Do We Always See the Same Side?
The Moon does rotate on its axis.
Its rotation period is essentially equal to its orbital period around Earth — approximately 27.32 days. This condition is known as synchronous rotation, or tidal locking.
As a result, essentially the same lunar hemisphere always faces Earth.
However, the Moon appears to oscillate slightly over the course of its orbit through an effect known as libration. This allows us to see a little beyond different parts of the lunar limb at different times.
At the moment of this photograph, the libration geometry favoured the south-eastern region of the lunar globe.
Over time, libration allows observers on Earth to see approximately 59% of the Moon's total surface, although never all at once.
Closer Than Average
At the exact time of the observation, the Moon was 361,863 km from Earth, significantly closer than its mean distance of approximately 384,400 km.
The reason is that the Moon does not follow a perfectly circular orbit. Its distance from Earth continually changes as it travels around us.
This changing distance also alters its apparent size.
At 21:23, the lunar disc measured approximately 33′ 00.65″ across the sky.
The variation is subtle when viewed with the naked eye but readily measurable photographically and explains why the apparent diameter of the Moon is not identical from one observation to another.
The Moon Is Darker Than It Looks
Despite its dazzling appearance in the night sky, the lunar surface is actually surprisingly dark.
Its average albedo is approximately 0.12, meaning that it reflects only about 12% of the sunlight that reaches it.
Its brilliance is largely the result of contrast: the Moon is directly illuminated by the Sun while surrounded by a much darker night sky.
At the moment of this photograph its apparent magnitude was approximately –11.39, making it overwhelmingly brighter than any star or planet visible in the night sky.
A Moving World
Although the Moon may appear almost stationary when observed casually, it is travelling rapidly through space.
At the time of this photograph, its orbital velocity was approximately 1.067 km/s — more than 3,800 km/h.
It completes one orbit relative to the distant stars in approximately 27.32 days, known as its sidereal period.
However, the interval between one identical lunar phase and the next is longer: approximately 29.53 days. This is the synodic period.
The difference occurs because Earth itself is travelling around the Sun. After completing one orbit around Earth, the Moon must move slightly farther before the same Sun–Earth–Moon geometry is restored.
The Only World Beyond Earth We Have Walked On
The Moon occupies a unique place among all the astronomical objects in this collection.
It remains the only celestial body beyond Earth on which human beings have walked.
Between 1969 and 1972, six Apollo missions successfully landed astronauts on its surface. Twelve people walked on the Moon, collected rocks, deployed scientific instruments and directly explored another world.
The terrain visible in this photograph is therefore more than an astronomical landscape.
It belongs to a world that humans have actually visited.
Looking Back in Time
For most deep-sky objects, looking through a telescope means looking far into the past. Light from distant galaxies may have travelled for millions of years before reaching the camera.
The Moon is radically different.
At its distance of 361,863 km at 21:23 on 29 December 2025, reflected light required only about 1.2 seconds to travel from the lunar surface to the telescope.
In astronomical terms, this photograph therefore shows the Moon almost in real time.
Yet the landscape reflecting that light is extraordinarily ancient. Much of the heavily cratered lunar highlands formed more than four billion years ago, while the great impact basins and basaltic maria preserve events dating back to the early history of the Solar System.
The photograph therefore combines two dramatically different timescales:
light only 1.2 seconds old, reflected from a landscape billions of years old.
Image Data
Target: Moon
Date: 29 December 2025
Local time: 21:23
Phase: Waxing Gibbous
Moon age: 9.6 days
Illuminated fraction: 72.1%
Distance from Earth: 361,863 km
Apparent diameter: 33′ 00.65″
Altitude at observation: 55° 54′
Filter: Luminance
Binning: 1×1
Gain: 100
SQM: 18.35
Telescope: Artesky ARTEC 250 Pro
Mount: 10Micron GM2000 HPS II