HK Stars

An almanac for Hong Kong stargazers — when the sky is dark, the moon is kind, and the clouds are thin.

Tonight

Sai Wan Stargazing Site

34/100
PoorHeavy cloud (99%) — stay in.

ECMWF··refreshes every 30 min

Models agreeECMWF 34 · 99% cloudvsICON 36 · 97% cloud
Best night this week: Monday 11 May · 87/100 · 21:00–00:00
Astro darkAstronomical darkness — the sun is more than 18° below the horizon, so the sky is fully dark. The best time to see faint stars.
20:13 – 04:26
Best windowThe longest stretch of forecast cloud cover ≤ 40% during astronomical darkness. The most reliable time to head out.
No clear window
MoonThe moon's phase changes how bright the sky is. New moon = darkest skies; full moon = washes out faint stars.
Waning gibbous
70% lit
Night-strip · sunset → sunrise
☼ 18:5205:47 ☼
20:0022:0000:0002:0004:00
cloud coverbest windowmoon altitude
What's pulling the score
  • Sky clarityPercentage of the sky covered by cloud, averaged over the night.1
  • DarknessHow dark the sky is once you account for moon brightness and how long it's above the horizon.61
  • SpotPenalty based on light pollution at the chosen location (Bortle scale).75
  • HazeHigh humidity scatters city light and dims faint stars. Hong Kong summers are typically very hazy.32

What's visible tonight

At 00:20 HKT

In season

  • Milky Way galactic core· south · around midnight
  • Scorpius· south · around midnight

Positions are at the mid-point of the best dark-sky window. Magnitudes assume clear conditions — light pollution will reduce what you can actually see.

How this score works

Each night gets a 0–100 score based on four things, weighted by how much they matter:

  • Sky clarity (45%) — average cloud cover during astronomical darkness.
  • Darkness (25%) — moon brightness, weighted by how long it's above the horizon.
  • Spot (20%) — light pollution at the chosen location (Bortle scale).
  • Haze (10%) — humidity penalty above 70% (Hong Kong summers are hazy).

The longest stretch of forecast cloud cover ≤ 40% during astronomical darkness. The most reliable time to head out.

Rest of the week

  1. Tomorrow
    Fair
    Best window
    None forecast
    37
    /100
  2. Sat 9 May
    Fair
    Best window
    None forecast
    47
    /100
  3. Sun 10 May
    Good
    Best window
    22:00–01:00
    59
    /100
  4. Mon 11 May
    Excellent
    Best window
    21:00–00:00
    87
    /100

Add the next 5 nights to your calendar →

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