GoodSeeing
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Iida

35.520° N   137.821° E  ·  517 M
44 /100
PEAK
Marginal, but there is a 1 hour gap from 02:00.
BEST WINDOW 02:00–03:00 · ASTRO DARK 02:00–04:00 · MOON 0%
Transparency
0.33
Seeing
0.99
Cloud
57%
Moon
0%

Fair tonight

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

Sky state
Lighter = daylight and twilight  ·  unshaded = astronomical dark
Score
02
03
04
05
44
30
16
0
BEST WINDOW
Low cloud
11%
13%
9%
2%
Mid cloud
4%
15%
16%
2%
High cloud
48%
81%
94%
98%
Transparency
0.31
0.33
0.33
0.34
Seeing
0.99
0.99
0.97
0.97
Moon clear
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
02 Fair · 44/100
Starting from
100
Cloud
−39
Transparency
−17
Seeing
−0
Moonlight
−0
Darkness
−0
Score
44
CLOUD 57% LOW 11% MID 4% HIGH 48% SUN -31.4° MOON -31.2° / 0% WIND 2 TEMP 19°
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.

SET UP 01:30 · OBSERVE 02:00–03:00 · 1H · MEAN 42

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

0204
CLOUD RETURNS 03:00
SET UP 01:30 · OBSERVE 02:00–03:00 · 1H · MEAN 52

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

0204
CLOUD RETURNS 03:00MOONLIGHT IGNORED FOR THIS TARGET
SET UP 01:30 · OBSERVE 02:00–03:00 · 1H · MEAN 36

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

0204
CLOUD RETURNS 03:00
NO USABLE WINDOW FOR THIS TARGET TONIGHT

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

0204
CLOUD NEVER DROPS BELOW 57%
SET UP 01:30 · OBSERVE 02:00–03:00 · 1H · MEAN 40

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

0204
CLOUD RETURNS 03:00
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The next week of nights

Tonight · 12 Aug
44
Fair
MOON 0%
02:00–03:00
Tomorrow · 13 Aug
61
Good
MOON 1%
21:00–04:00
Friday · 14 Aug
57
Good
MOON 5%
21:00–03:00
Saturday · 15 Aug
21
Poor
MOON 8%
Sunday · 16 Aug
27
Poor
MOON 19%
Monday · 17 Aug
6
Clouded out
MOON 28%
Tuesday · 18 Aug
42
Fair
MOON 37%
03:00–04:00
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Nearby locations

About this forecast

Conditions for Iida, 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 →