Southern delta-Aquariids from Tokyo in 2026

Southern delta-Aquariids from Tokyo: the short answer

From Tokyo (35.7°N, 44 m) the Southern delta-Aquariids maximum of 22:23 on 31 July 2026 is not worth a broken night. The radiant culminates at 38.4° at 01:49, and on the reference rural sky that converts to 3.7 meteors an hour at best.

That ranks it 12th of twelve from Tokyo this year, behind the Geminids (149.5/h) and the Perseids (83.9/h).

The radiant track over this city

At 35.7°N a declination-−16.1° radiant traces an arc from 20:37 to 07:02, topping out at 38.4° at 01:49 bearing 180°. Inside the dark window it only manages 38.3°, and that lower figure is the one the rates are built from. The radiant currently lies in Aquarius.

When it gets dark here

Sunset over Tokyo is 18:46, civil twilight ends 19:14, and the sky reaches astronomical darkness — Sun 18° down — at 20:25. It holds until 03:09, with sunrise at 04:48: 6 h 44 min of real darkness inside 10 h 2 min of night.

Local solar midnight, the true middle of the night, falls at 23:47 here rather than at 00:00: Asia/Tokyo runs 19 minutes behind mean solar time at 139.69°E. That offset is why the best hour on this page is not the hour you would guess from the clock.

What the Moon does here

Moonlight is the limiting factor on this night from Tokyo. The Moon is 96% lit and only 0 of 9 sampled hours are moon-free. Moonrise 19:45. Moonset 07:03. At the best hour it stands 38.1° above the horizon, 8° from the radiant, pulling the limiting magnitude down to 5.32.

Why 4 an hour and not 25

Zenithal hourly rate 25, population index 3.2, entry speed 40.6 km/s — fast. Those are stream constants. What changes from city to city is the geometry: at 38.3° of radiant altitude and limiting magnitude 5.32, Tokyo converts that ZHR into about 3.7 meteors an hour.

Hour by hour the modelled rate runs from 0.0 at 20:00 (radiant -7.2°) to 0.0 at 04:00 (radiant 29.8°), peaking at 3.7. That spread across 9 hours is why a "what time" answer beats a "how many" answer.

The stream comes from Comet 96P/Machholz and is listed as active 12 July to 23 August, so 31 July 2026 is the best night from Tokyo rather than the only one.

Watching from around Tokyo

Tokyo is the 21st largest of the 300 cities covered here, with a population of 9.73 million at 44 m above sea level. The nearest other cities on the site are Nagoya (259 km WSW), Osaka (397 km WSW), Sapporo (833 km N) — close enough that the radiant altitudes barely change, far enough that sunset and moonrise do.

What this page does not know

Light-pollution data for this location is not connected yet. Rates on this page are computed against the reference rural sky the zenithal hourly rate is defined for (naked-eye limiting magnitude 6.5); they are not a claim about how bright the sky is where you are standing. Once the light-pollution layer is connected these figures will be recomputed for the local sky and will generally fall.

Cloud cover is a forecast, not a constant, so it is resolved when you load the tonight card and is deliberately absent from this prerendered page — the hourly table shows "unavailable" rather than assuming clear skies. Meteor outbursts, local terrain and building horizons are not modelled.

A single observer with an unobstructed horizon typically records 30–50% below the ideal-sky figure. Give your eyes twenty minutes to adapt, keep bright screens away, look about halfway up the sky rather than straight at the radiant, and count for a full hour before judging a shower.