🌋 Mauna Kea — Tonight's Sky Report (Sep 24, 2026)

Verdict: A world-class site, but tonight the summit is wearing a thick blanket. Bortle 2 skies, 4,200 m altitude, and one of the driest atmospheres on Earth — and yet the weather data shows a total washout. Viewing quality is 0/100. Let's break down exactly what's happening hour by hour.

🌧️ Hourly Weather Evolution (HST)

The pattern: The summit is parked inside a cloud deck all night. There's no "clearing early" or "opening later" — every single hour fails the good-observing thresholds on five counts: 100% cloud cover, ~90% precipitation probability with 2+ mm intensity, visibility crushed to ~0.1 km, and fog hovering at 99%. The only trends are subtle: temperatures slide gently downward from 13.2°C to 12.4°C, while the wind steadily builds from 3.7 to 5.3 m/s — a classic sign of an inbound disturbance, not a departing one. In short: no hour is salvageable.

🌕 The Moon — A Second Problem

Even if the clouds parted, tonight is a Waxing Gibbous at 92–98% illumination (age ~12.9 days, just one day shy of Full Moon). The Moon transits at 23:05 and would flood the sky with -12.2 magnitude glare, drowning out everything fainter than mag ~3-4. The "dark sky" window is effectively closed tonight regardless of weather.

🪐 What's Up There (Behind the Clouds)

• Saturn (mag 0.34) — transits 00:51, highest in the south. Rings at near-max tilt; a spectacular sight in any scope... if you could see it.
• Uranus (mag 5.65) — transits 04:17. Technically a naked-eye object from Bortle 2, but it needs a dark, transparent sky and good optics.
• No ISS passes, no meteor showers — the night is astronomically quiet on the transient front.

🔭 Recommended Targets (for a Better Night)

The system's top picks for this site and season are gorgeous: M13 and M22 (globular clusters), M31 (Andromeda Galaxy), M6/M7 (open clusters in Scorpius), and M24 (the Sagittarius Star Cloud). All are well-placed — but they'll have to wait.

✅ My Recommendation

Stay off the summit tonight. With 100% overcast, near-zero visibility, and fog at 99%, this is a night for gear maintenance, planning your next session, or catching up on sleep. The silver lining: the Moon reaches Full on Sep 25 and then fades, so the next new-moon window will deliver the dark, transparent skies Mauna Kea is famous for. When that front clears, Saturn and the summer globulars will be waiting.

Clear skies (next time)! 🔭