HK Stars

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

Tonight

Tai Mo Shan

30/100
PoorHeavy cloud (100%) — stay in.

ECMWF··refreshes every 30 min

Models agreeECMWF 30 · 100% cloudvsICON 31 · 97% cloud
Best night this week: Monday 11 May · 81/100 · 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.
20:14 – 04:27
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
☼ 18:5305:48 ☼
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.0
  • 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).50
  • HazeHigh humidity scatters city light and dims faint stars. Hong Kong summers are typically very hazy.43
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
    Poor
    Best window
    None forecast
    32
    /100
  2. Sat 9 May
    Fair
    Best window
    None forecast
    38
    /100
  3. Sun 10 May
    Great
    Best window
    23:00–05:00
    71
    /100
  4. Mon 11 May
    Excellent
    Best window
    21:00–00:00
    81
    /100

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