December is a magical month to step outside and enjoy the night sky. The nights are long, the air is crisp, and the winter constellations take center stage above Cork. This month brings bright planets, two exciting meteor showers, and some classic deep-sky objects that are perfect for observing. Whether you’ve got a telescope, binoculars, or just your eyes, there’s plenty to see.
Moon Phases
- Full Moon 4/12/2025 23:15UT
- Last Quarter 11/12/2025 20:52UT
- New Moon 20/12/2025 01:44UT
- First Quarter 27/12/2025 19:11UT
Planets on Show
- Mercury – Low in the morning twilight mid-month.
- Venus – Brilliant in the morning sky, rising before sunrise.
- Mars – In Gemini, rising early morning, visible before dawn.
- Jupiter – Evening visibility decreases as it sets earlier; still bright.
- Saturn – High in the south during early evening; gradually sets earlier in December.
- Uranus – Binocular target, rising late evening near Aries.
- Neptune – In Aquarius, best viewed mid-evening with a telescope.
Meteor Showers
- Geminids – Active Dec 4–17, peak Dec 13–14, one of the year’s best showers (bright, colourful meteors). The Moon will be only a thin crescent/low illumination during peak nights (about ~30% illuminated), so conditions are good.
- Ursids – Active Dec 17–26, peak around Dec 22 (around the winter solstice), smaller shower but can produce bright meteors.
Key Events
- Dec 4 – Full Moon (Cold Moon) — a notable supermoon in 2025 (higher and slightly larger/bright).
- Dec 5–8 – Moon near Jupiter / Moon–Jupiter close passes — easy evening targets; look for Moon and very bright Jupiter together.
- Dec 13–14 – Geminid Meteor Shower peak — excellent late-night show; moonlight will be low to moderate (good conditions).
- Dec 19 – Comet 3I/ATLAS closest approach to Earth (early pre-dawn; faint, requires binoculars/telescope — look toward Leo/Regulus area).
- Dec 20 – New Moon (dark skies) — excellent for deep-sky observing after this date.
- Dec 22 – Ursid peak (around the solstice) — late-night viewing can produce occasional bright meteors.
Deep Sky Favorites
(Best viewed around the New Moon, Dec 20 and especially after Dec 28 when skies are darkest)
Orion Nebula (M42) – Bright and stunning in winter’s Orion.
Pleiades (M45) – High in the northwest, brilliant cluster for binoculars or the naked eye.
Andromeda Galaxy (M31) – Still prominent in the east.
Double Cluster in Perseus – A classic winter treat through binoculars.
Local Sunset, Twilight & Darkness Windows in Cork (December 2025)
- Early December: sunset ≈ 16:25, sunrise ≈ 08:22.
- By late December: sunset ≈ 16:20, sunrise ≈ 08:40 (latest sunrise around Dec 30).
- Astronomical darkness typically begins ~17:30–18:00, giving long stretches for observing after work/dusk.
Sky Events & Highlights for Cork – December 2025
| Date / Period | Event | Best Time & Notes from Cork |
|---|---|---|
| Dec 4 | Full Moon / Cold Supermoon | Moonrise and moonlight make this a dramatic night for lunar photography; it will be bright. |
| Dec 4–17 | Geminid Meteor Shower active | Peak nights Dec 13–14. Best after midnight; with only ~30% moon illumination at peak, conditions are favourable for many meteors. |
| Dec 5–8 | Moon near Jupiter | Evening pairing, great for binoculars/telescope — look western/evening sky. |
| Dec 13–14 | Geminids peak | Late-night to pre-dawn is best; expect bright, frequent meteors if skies are clear. |
| Dec 17–26 | Ursid Meteor Shower active | Peak around Dec 22; best late night into early morning. |
| Dec 19 | Comet 3I/ATLAS closest approach | Early pre-dawn in Leo/Regulus area; small scope/binoculars recommended (object is faint). |
| Dec 20 | New Moon | Dark skies; prime for winter deep-sky targets like Orion Nebula and Pleiades. |
Sample Observing Nights & Tips (for Cork)
- Dec 13–14: Geminid peak — late-night viewing under clear skies; bring a reclining chair, warm layers, and binoculars.
- Dec 19 (pre-dawn): try catching Comet 3I/ATLAS near Regulus in Leo — small scope helps; it will be faint (follow nightly ephemerides).
- Dec 22: Ursid peak — smaller shower but worth an hour or two late at night for any bright fireballs.
- Dec 20–28: Excellent block for deep-sky imaging/observing thanks to the New Moon on Dec 20 (dark skies).
Wrapping Up
December 2025 is packed with winter celestial highlights for Cork. From the spectacular Geminid meteors and Ursid fireballs to close Moon–Jupiter pairings and the faint interstellar visitor 3I/ATLAS, it’s an excellent month for stargazers. Dress warmly, find a clear dark spot, and enjoy the winter skies, it’s a month full of cosmic wonder.
Clear Skies.