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Arches National Park

38.733° N   109.593° W  ·  1500 M
62 /100
PEAK
Worth setting up — 5 hours of workable sky from 22:00.
BEST WINDOW 22:00–03:00 · ASTRO DARK 22:00–05:00 · MOON 1%
Transparency
0.82
Seeing
1.00
Cloud
7%
Moon
1%

Good tonight

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

Sky state
Lighter = daylight and twilight  ·  unshaded = astronomical dark
Score
20
21
22
23
00
01
02
03
04
05
06
07
0
9
35
40
37
62
44
25
60
60
2
0
BEST WINDOW
Low cloud
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
Mid cloud
53%
20%
37%
14%
25%
2%
37%
56%
17%
10%
7%
9%
High cloud
82%
70%
63%
92%
84%
50%
43%
58%
26%
0%
0%
0%
Transparency
0.70
0.63
0.74
0.82
0.78
0.72
0.66
0.29
0.57
0.41
0.33
0.33
Seeing
0.69
0.94
0.58
0.96
0.93
0.90
1.00
1.00
1.00
0.98
0.97
1.00
Moon clear
0%
down
down
down
down
down
down
down
down
down
down
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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
20 Clouded out · 0/100
Starting from
100
Cloud
−71
Transparency
−3
Seeing
−2
Moonlight
−0
Darkness
−23
Score
0
CLOUD 91% LOW 0% MID 53% HIGH 82% SUN 2.4° MOON 6.3° / 0% WIND 5 TEMP 27°
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 00:30 · OBSERVE 01:00–02:00 · 1H · MEAN 40

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

202200020406
HIGH CLOUD CLEARS 01:00
SET UP 03:30 · OBSERVE 04:00–06:00 · 2H · MEAN 57

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

202200020406
HIGH CLOUD CLEARS 04:00TWILIGHT BEGINS 06:00MOONLIGHT IGNORED FOR THIS TARGET
NO USABLE WINDOW FOR THIS TARGET TONIGHT

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

202200020406
CLOUD HOLDS ABOVE 94%
NO USABLE WINDOW FOR THIS TARGET TONIGHT

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

202200020406
CLOUD HOLDS ABOVE 94%
SET UP 03:30 · OBSERVE 04:00–06:00 · 2H · MEAN 37

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

202200020406
HIGH CLOUD CLEARS 04:00TWILIGHT BEGINS 06:00
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The next week of nights

Tonight · 12 Aug
62
Good
MOON 0%
22:00–03:00
Tomorrow · 13 Aug
78
Excellent
MOON 3%
22:00–06:00
Friday · 14 Aug
82
Excellent
MOON 7%
22:00–01:00
Saturday · 15 Aug
56
Good
MOON 15%
00:00–01:00
Sunday · 16 Aug
74
Good
MOON 23%
00:00–01:00
Monday · 17 Aug
89
Excellent
MOON 32%
00:00–01:00
Tuesday · 18 Aug
62
Good
MOON 42%
00:00–01:00
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Nearby locations

About this forecast

Conditions for Arches National Park, Utah, United States 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 →