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Arai

34.683° N   137.567° E  ·  2 M
28 /100
PEAK
Nothing usable opens up tonight.
NO USABLE WINDOW · ASTRO DARK 01:00–04:00 · MOON 0%
Transparency
0.45
Seeing
0.48
Cloud
23%
Moon
0%

Poor tonight

Hour by hour, local to Arai. Colour encodes the score and nothing else; every other measurement is luminance.

Sky state
Lighter = daylight and twilight  ·  unshaded = astronomical dark
Score
01
02
03
04
05
11
23
28
35
0
Low cloud
41%
6%
12%
9%
1%
Mid cloud
43%
29%
14%
8%
6%
High cloud
93%
88%
84%
9%
8%
Transparency
0.41
0.42
0.44
0.45
0.46
Seeing
0.21
0.34
0.44
0.48
0.53
Moon clear
down
down
down
down
down
Inspect

Cloud tracks show clear sky — a longer bar is better. The figure inside each track is the raw measurement.

Why this hour scored what it did
01 Clouded out · 11/100
Starting from
100
Cloud
−82
Transparency
−4
Seeing
−3
Moonlight
−0
Darkness
−0
Score
11
CLOUD 98% LOW 41% MID 43% HIGH 93% SUN -38.0° MOON -37.1° / 0% WIND 10 TEMP 24°
Excellent 75+ Good 55+ Fair 35+ Poor 15+ Not worth it Seeing is estimated from surface wind — see how we score.

What are you doing tonight?

The same forecast, weighted for the target. Planetary work barely cares about moonlight; long exposures die on high cloud a visual observer would never notice.

NO USABLE WINDOW FOR THIS TARGET TONIGHT

Darkness and moonlight dominate. Faint fuzzies need a genuinely dark sky more than they need steady air.

010305
CONDITIONS STAY BELOW THE USABLE THRESHOLD
SET UP 03:30 · OBSERVE 04:00–05:00 · 1H · MEAN 48

Seeing is everything and moonlight is irrelevant. Bright targets punch through twilight, so darkness barely counts.

010305
HIGH CLOUD CLEARS 04:00TWILIGHT BEGINS 05:00SEEING STAYS SOFT THROUGHOUT
NO USABLE WINDOW FOR THIS TARGET TONIGHT

Tolerates soft seeing, but high cloud wrecks a wide frame and moonlight raises the background everywhere.

010305
CONDITIONS STAY BELOW THE USABLE THRESHOLD
NO USABLE WINDOW FOR THIS TARGET TONIGHT

Needs conditions to hold still for hours. Sustained transparency matters more than any single good hour.

010305
CONDITIONS STAY BELOW THE USABLE THRESHOLD
NO USABLE WINDOW FOR THIS TARGET TONIGHT

Naked eye, whole sky. Total cloud and moonlight are the only things that count.

010305
CONDITIONS STAY BELOW THE USABLE THRESHOLD
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The next week of nights

Tonight · 12 Aug
28
Poor
MOON 0%
Tomorrow · 13 Aug
48
Fair
MOON 1%
00:00–01:00
Friday · 14 Aug
51
Fair
MOON 5%
23:00–02:00
Saturday · 15 Aug
54
Fair
MOON 8%
21:00–22:00
Sunday · 16 Aug
41
Fair
MOON 19%
03:00–04:00
Monday · 17 Aug
26
Poor
MOON 28%
Tuesday · 18 Aug
68
Good
MOON 37%
03:00–04:00
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Nearby locations

About this forecast

Conditions for Arai, Japan are computed from the MET Norway forecast model for these exact coordinates, combined with sun and moon positions we calculate directly. The score weighs cloud cover by layer, atmospheric transparency, estimated seeing, moonlight and how dark the sky actually gets. Read the full method →