Moon phases
1 December and 31 December: New Moon
A new moon is the first lunar phase, when the Moon and Sun have the same ecliptic longitude. The Moon is aligned with the Sun and the Earth, and the side of the Moon that faces Earth is in darkness. The new Moon is not visible to the naked eye, as it is too close to the Sun’s glare or below the horizon during the day.
9 December: First quarter moon
At first quarter, one-half of the Waxing Moon appears to be illuminated by the Sun's light, while the other half is in shadow. This is because the Moon is at a 90-degree angle to the Earth and Sun.
15 December: Full Moon
During a Full Moon, the Moon's surface is fully illuminated by the Sun. This happens because the Earth is between the Sun and the Moon, and they are aligned in a straight line
23 December: Last quarter Moon
At last quarter, one-half of the Waning Moon appears to be illuminated by the Sun's light, while the other half is in shadow. This phase is ideal for spotting lunar features along the terminator line.
Notable Night Sky Events for December
5 December: Venus and the Moon Conjunction
Time: Evening, shortly after sunset.
Details: Venus and the crescent Moon will appear close together in the western sky. This striking pairing will be visible to the naked eye, providing a perfect opportunity for astrophotography.
8 December: Jupiter at Opposition
Time: 21:00 UTC (7:00 AM AEST)
Details: Jupiter will be directly opposite the Sun from Earth’s perspective. This alignment makes Jupiter fully illuminated by the Sun, making it the brightest and largest it appears in the night sky this year. At opposition, Jupiter shines with a magnitude of -2.8, outshining nearly everything except the Moon and Venus.
8 December: Conjunction of the Moon and Saturn
Time: From sunset to midnight AEST
Details: Saturn and the Moon will be separated by less than a degree. The Moon will be about 51.1% illuminated. In certain regions, the Moon will pass in front of Saturn, resulting in a lunar occultation. The lunar occultation will be visible from specific regions, including eastern Indonesia, Japan, eastern Philippines, and north-western Papua New Guinea.
13–14 December: Geminid Meteor Shower Peak
Peak: Morning of 14 December (AEST/UTC)
Details: The most reliable meteor shower of the year peaks, producing up to 120 meteors per hour under ideal conditions. The radiant is near Castor in Gemini, visible from around 10 PM local time. Unfortunately, the nearly full Moon (waxing gibbous at 80% illumination) will brighten the sky, reducing the number of visible meteors. Best viewing will be after moonset around 4 AM AEST.
14-15 December: Moon close approach to Jupiter
Time: From 7:00 PM AEST onwards
Details: The Moon passes near Jupiter on both nights.
15 December: Full Moon (“Cold Moon”)
Time: 14:02 AEST (04:02 UTC)
Details: The full Moon rises in Gemini, brightening the night sky. Its presence will impact observations of faint celestial objects and meteor activity. It is still a beautiful sight to enjoy with the naked eye or through binoculars.
18-19 December: Close encounter of Mars and the Moon
Time: From 11:00 PM to dawn the following morning
Details: This is an excellent opportunity to observe Mars, as it will be easily identifiable next to the bright Moon. Using a telescope or binoculars will enhance the experience, allowing you to see more details of Mars and the Moon. The pair will appear to be separated by less than 3 degrees.
21 December: Summer Solstice (Southern Hemisphere)
Time: 14:20 AEST (04:20 UTC)
Details: This marks the longest day of the year for the Southern Hemisphere. Enjoy extra daylight before settling in for warm summer nights under the stars.
22 December: Ursid Meteor Shower Peak
Peak: 22 December (night to early morning, AEST/UTC)
Details: A minor meteor shower with a peak rate of 10–20 meteors per hour. The radiant lies near Ursa Minor, making it more favourable for observers in the northern hemisphere. The waning crescent Moon provides darker skies, giving better visibility to meteors.
24 December: Santa is visible
Time: 9:00 PM til Midnight
Details: Santa’s sleigh, powered by a team of reindeer (Rudolph leading with that unmistakable red nose), will streak across the night sky at record speed. Travelling at approximately the speed of Christmas cheer, he’ll be delivering presents to good kids and probably eating his weight in cookies. Keep an eye on the horizon! Use a wide-angle lens to capture those sleigh trails. Bonus points if you catch him “mooning” the gibbous Moon that night!
25 December: Mercury at Greatest Western Elongation
Time: Morning, before sunrise
Details: Mercury reaches its greatest angular separation from the Sun at 22 degrees, making it the best time to view this elusive planet. It will appear as a bright “star” low in the eastern sky during dawn. Ensure you have an unobstructed horizon to spot it, as Mercury’s altitude will still be relatively low. This event is perfect for early risers or anyone seeking a festive celestial gift!
Planetary Highlights
Mercury: Visible in the evening sky in Sagittarius early in the month. After mid-month, it moves closer to the Sun and becomes harder to see.
Venus: Shines as a bright evening star early in the month before transitioning to the morning sky mid-month.
Mars: Low in the evening sky in Scorpius, becoming difficult to spot by month-end.
Jupiter: Dominates the evening sky in Taurus and offers excellent viewing opportunities for its moons and cloud bands.
Saturn: Sets early in the evening in Aquarius, making it visible only during early December nights.
Uranus and Neptune: Both are observable with a high-powered telescope in Aries and Pisces, respectively, during early evening hours.
Best Astrophotography Targets this Month
Rosette Nebula (NGC 2237): A large emission nebula in Monoceros, perfect for capturing rich red hues with a narrowband filter.
Hyades Cluster: In Taurus, an excellent target for wide-field shots, often paired with Aldebaran.
Double Cluster (NGC 869 and NGC 884): In Perseus, these neighbouring open clusters are visually stunning and rich with stars.