Tonight’s Moon: What You’ll See on December 15
If you step outside on December 15, you’ll notice that the Moon’s appearance is evolving as it heads toward a New Moon. For skywatchers, this is a brief window where the face is thinner, and subtle features on the lunar limb can become easier to spot with a modest telescope or even a good set of binoculars.
Understanding the Phase
The Moon’s phase on December 15 is part of a short-lived trend toward the New Moon. As the illuminated portion of the Moon shrinks, the night sky becomes darker, making faint lunar features more challenging to see without optical aid. If you’ve been following the Moon for the past week, you’ll notice the crescent becoming thinner, with Earth’s shadows playing a more visible role on the terminator—the line separating day from night on the Moon’s surface.
What You Might Observe
Even with a thin crescent or a more subtle shape, you can still enjoy several interesting details. Look for the following:
- <strongCraters and Rilles: The Moon’s rugged terrain near the limb often reveals large craters and winding rilles along the terminator as sunlight angles cast long shadows.
- Libration: The Moon’s slight wobble, known as libration, can reveal slightly different edges from night to night. You might catch a glimpse of features just beyond the edge on December 15.
- Geological Highlights: If conditions permit, you can try to spot seas (maria) in the dark basalt plains that contrast with brighter highlands—the interplay is most noticeable around the terminator.
Best Time and Tools for Observation
To maximize your chances, observe a few hours after sunset or in the pre-dawn hours when the Moon is higher in the sky but still near the horizon. A stable setup helps:
- Binoculars or a small telescope can dramatically improve contrast and reveal fine details on the Moon’s edge.
- Use low magnification to start, then increase slightly to study specific craters like the larger ones near the maria as they emerge from the shadow.
- Allow your eyes to adapt to the darkness for about 15 minutes to boost contrast.
How the Phase Affects Darkness and Observing Conditions
As the Moon approaches New Moon, its nights become darker, which benefits deep-sky observers but makes the Moon itself more subtle to amateur eyes. However, the reduced glare can help you focus on faint rim details and subtle topography that are washed out when the Moon is fully illuminated.
Tips for a Great December 15 Moon Watch
- Check local weather and light pollution maps to pick a truly dark, clear site.
- Record quick sketches or photos at different times to notice how features shift with libration.
- Pair your Moon observation with a quick glance at a planet or bright star to place the Moon in context for the evening sky.
Bottom Line
December 15 offers a quiet but rich opportunity to study the Moon’s edge as it slides toward the New Moon. With a little patience and the right gear, you’ll catch a glimpse of the Moon’s rugged beauty and its subtle changes from night to night.
