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Jiayuguan

39.811° N   98.286° E  ·  1635 M
82 /100
PEAK
A genuinely good night — 4 hours of clear, dark sky from 02:00.
BEST WINDOW 02:00–06:00 · ASTRO DARK 02:00–05:00 · MOON 0%
Transparency
1.00
Seeing
1.00
Cloud
9%
Moon
0%

Excellent tonight

Hour by hour, local to Jiayuguan. 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
06
07
73
51
76
82
10
0
BEST WINDOW
Low cloud
0%
0%
0%
0%
0%
0%
Mid cloud
0%
0%
0%
0%
0%
0%
High cloud
49%
89%
44%
19%
9%
99%
Transparency
1.00
1.00
1.00
1.00
1.00
0.98
Seeing
1.00
1.00
1.00
1.00
1.00
1.00
Moon clear
down
down
down
down
down
0%
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 Good · 73/100
Starting from
100
Cloud
−27
Transparency
−0
Seeing
−0
Moonlight
−0
Darkness
−0
Score
73
CLOUD 49% LOW 0% MID 0% HIGH 49% SUN -34.9° MOON -34.3° / 0% WIND 1 TEMP 20°
Excellent 75+ Good 55+ Fair 35+ Poor 15+ Not worth it Seeing is estimated from surface wind — see how we score.
Tonight's limiting factor
Why thin high cloud ruins long exposures

Cirrus you can barely see will halo your bright stars, lift your background and vary between frames. Visual observers shrug it off. Long exposures integrate it, so it accumulates.

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 02:00–06:00 · 4H · MEAN 67

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

020406
TWILIGHT BEGINS 06:00
SET UP 01:30 · OBSERVE 02:00–07:00 · 5H · MEAN 67

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

020406
CLOUD RETURNS 07:00MOONLIGHT IGNORED FOR THIS TARGET
SET UP 01:30 · OBSERVE 02:00–06:00 · 4H · MEAN 61

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

020406
TWILIGHT BEGINS 06:00
SET UP 03:30 · OBSERVE 04:00–06:00 · 2H · MEAN 65

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

020406
HIGH CLOUD CLEARS 04:00TWILIGHT BEGINS 06:00
SET UP 01:30 · OBSERVE 02:00–06:00 · 4H · MEAN 62

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

020406
TWILIGHT BEGINS 06:00
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The next week of nights

Tonight · 12 Aug
82
Excellent
MOON 0%
02:00–06:00
Tomorrow · 13 Aug
93
Excellent
MOON 1%
22:00–06:00
Friday · 14 Aug
89
Excellent
MOON 5%
22:00–06:00
Saturday · 15 Aug
47
Fair
MOON 10%
02:00–03:00
Sunday · 16 Aug
9
Clouded out
MOON 19%
Monday · 17 Aug
97
Excellent
MOON 28%
02:00–03:00
Tuesday · 18 Aug
100
Excellent
MOON 37%
02:00–03:00
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Nearby locations

About this forecast

Conditions for Jiayuguan, 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 →