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Longtan

28.757° N   108.964° E  ·  328 M
56 /100
PEAK
Worth setting up — 2 hours of workable sky from 02:00.
BEST WINDOW 02:00–04:00 · ASTRO DARK 01:00–05:00 · MOON 0%
Transparency
0.20
Seeing
1.00
Cloud
17%
Moon
0%

Good tonight

Hour by hour, local to Longtan. 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
06
6
40
56
16
12
0
BEST WINDOW
Low cloud
83%
28%
7%
75%
77%
99%
Mid cloud
42%
17%
12%
5%
1%
18%
High cloud
20%
2%
1%
0%
0%
0%
Transparency
0.10
0.18
0.20
0.19
0.17
0.10
Seeing
1.00
1.00
1.00
1.00
1.00
1.00
Moon clear
down
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 · 6/100
Starting from
100
Cloud
−91
Transparency
−3
Seeing
−0
Moonlight
−0
Darkness
−0
Score
6
CLOUD 85% LOW 83% MID 42% HIGH 20% SUN -46.2° MOON -45.3° / 0% WIND 1 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.

SET UP 01:30 · OBSERVE 02:00–04:00 · 2H · MEAN 48

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

010305
HIGH CLOUD CLEARS 02:00CLOUD RETURNS 04:00
SET UP 01:30 · OBSERVE 02:00–04:00 · 2H · MEAN 60

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

010305
HIGH CLOUD CLEARS 02:00CLOUD RETURNS 04:00MOONLIGHT IGNORED FOR THIS TARGET
SET UP 01:30 · OBSERVE 02:00–04:00 · 2H · MEAN 44

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

010305
HIGH CLOUD CLEARS 02:00CLOUD RETURNS 04:00
SET UP 02:30 · OBSERVE 03:00–04:00 · 1H · MEAN 41

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

010305
CLOUD BREAKS 03:00CLOUD RETURNS 04:00
SET UP 01:30 · OBSERVE 02:00–04:00 · 2H · MEAN 48

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

010305
HIGH CLOUD CLEARS 02:00CLOUD RETURNS 04:00
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The next week of nights

Tonight · 12 Aug
56
Good
MOON 0%
02:00–04:00
Tomorrow · 13 Aug
46
Fair
MOON 1%
03:00–05:00
Friday · 14 Aug
55
Good
MOON 5%
21:00–23:00
Saturday · 15 Aug
72
Good
MOON 10%
02:00–03:00
Sunday · 16 Aug
42
Fair
MOON 19%
02:00–03:00
Monday · 17 Aug
35
Fair
MOON 28%
02:00–03:00
Tuesday · 18 Aug
61
Good
MOON 37%
02:00–03:00
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Nearby locations

About this forecast

Conditions for Longtan, China 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 →