Astronomy from Siem Reap Cambodia in December 2025

December is one of the best months for astronomy in Siem Reap, Cambodia.December falls in the cool, dry season (November–April), with average highs of 30–32°C (86–90°F), lows around 22–24°C (72–75°F), low humidity (~65%), and very little rain (only ~10–20 mm for the month, usually 1–2 rainy days). Skies are typically clear and transparent most nights, making it prime for stargazing and telescope viewing—far better than the wet, cloudy monsoon months (May–October). Siem Reap itself has moderate light pollution (Bortle 5–6 in town), but it’s easy to escape to darker spots nearby.Key Astronomical Sights Visible in December EveningsFrom Siem Reap (latitude ~13°N), December nights showcase classic summer/winter constellations high overhead, plus excellent southern views:

• Planets: Jupiter (bright in the east, high by midnight – cloud bands and moons visible in a telescope); Saturn (low west at dusk, rings stunning until it sets ~10 PM); Mars (rising late evening, reddish and growing brighter).
• Deep-sky highlights (best after 9–10 PM on moonless nights): Orion Nebula (M42 – glowing gas cloud, a telescope “wow” object rising ~8 PM); Pleiades (M45 – sparkling star cluster); Andromeda Galaxy (M31 – visible naked-eye as a smudge in dark skies, bright core in telescope); Hyades cluster; southern gems like Omega Centauri (best globular cluster) and 47 Tucanae (both higher from Cambodia’s latitude).
• Meteor shower: Ursids peak ~Dec 22–23 (up to 10/hour max) – low rates but fun on moon-free nights.

The first half of December (especially around new moon on Dec 20) is moonless after sunset—perfect dark skies.

Main Meteor Shower: The Geminids

The standout event is the Geminids – one of the year’s strongest and most reliable showers, peaking on the night of December 13–14, 2025 (best viewing after midnight into the early morning of the 14th).

• Expected rates: Up to 50–120 meteors per hour under dark skies (realistic 30–80 from Cambodia with some light pollution).
• Characteristics: Bright, colorful (yellow, green, blue), medium-speed meteors with frequent fireballs – many visible even from moderately lit areas.
• Visibility from Siem Reap: The radiant (in Gemini) rises in the east around 8–9 PM and is high overhead by 2 AM, so you’ll get good activity from late evening onward. Cambodia’s latitude (~13°N) gives excellent views – nearly as good as northern Thailand.

Moon conditions are favorable: a waning crescent (about 30% lit on peak night) rises late, so it won’t wash out the early part of the show.

Best Vantage Points Near Siem Reap (Low Light Pollution)

Siem Reap town is Bortle 5–6 (Milky Way faint), so drive/scooter 20–60 mins or take a boat for Bortle 4–5 skies:

1. Phnom Bakheng or Pre Rup temples (inside Angkor complex) – elevated, open views; stay after sunset (Angkor Pass required, but quiet at night).
2. Hang Nak Nature Trail / Dragon Crest viewpoint – ~45 min drive north; high elevation, very dark once away from trails.
3. Remote areas around Angkor Wat / Banteay Srei – far temple edges or countryside roads; minimal lights.
4. Tonle Sap Lake shores (e.g., Kompong Phluk or northern lake edges) – boat out for zero light pollution on water.
5. Rural roads toward Kulen Mountain – 30–45 min north; open rice fields with almost no lights.

December’s dry weather makes access easy—bring insect repellent and a red flashlight. For the clearest nights, check for haze from field burning (rare in December). Enjoy—Siem Reap in December is astronomy heaven if you escape town!

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