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Draper

40.525° N   111.864° W  ·  1377 M
43 /100
PEAK
Marginal, but there is a 1 hour gap from 05:00.
BEST WINDOW 05:00–06:00 · ASTRO DARK 23:00–05:00 · MOON 1%
Transparency
0.88
Seeing
1.00
Cloud
50%
Moon
1%

Fair tonight

Hour by hour, local to Draper. 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
0
35
39
31
29
34
24
14
43
3
0
BEST WINDOW
Low cloud
0%
0%
0%
0%
0%
0%
0%
1%
0%
0%
0%
1%
Mid cloud
9%
65%
1%
13%
31%
31%
16%
41%
75%
43%
32%
45%
High cloud
90%
88%
99%
97%
98%
98%
97%
98%
90%
14%
81%
63%
Transparency
0.83
0.88
0.84
0.84
0.82
0.77
0.79
0.73
0.69
0.69
0.67
0.62
Seeing
1.00
1.00
1.00
1.00
0.96
0.79
0.73
0.75
0.80
0.89
0.92
0.86
Moon clear
0%
down
down
down
down
down
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
20 Clouded out · 0/100
Starting from
100
Cloud
−54
Transparency
−3
Seeing
−0
Moonlight
−0
Darkness
−43
Score
0
CLOUD 91% LOW 0% MID 9% HIGH 90% SUN 4.6° MOON 8.3° / 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.
Tonight's limiting factor
When a clear gap is worth driving for

Ask how long the gap is relative to your setup time and your exposure length. A two-hour gap is a real session for a visual observer and close to worthless for someone doing four-minute subs on a target that needs three hours.

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 04:30 · OBSERVE 05:00–06:00 · 1H · MEAN 41

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

202200020406
HIGH CLOUD CLEARS 05:00CLOUD RETURNS 06:00
SET UP 21:30 · OBSERVE 22:00–00:00 · 2H · MEAN 39

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

202200020406
MOONLIGHT IGNORED FOR THIS TARGET
SET UP 04:30 · OBSERVE 05:00–06:00 · 1H · MEAN 41

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

202200020406
HIGH CLOUD CLEARS 05:00CLOUD RETURNS 06:00
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 NEVER DROPS BELOW 50%
SET UP 04:30 · OBSERVE 05:00–06:00 · 1H · MEAN 39

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

202200020406
HIGH CLOUD CLEARS 05:00CLOUD RETURNS 06:00
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The next week of nights

Tonight · 12 Aug
43
Fair
MOON 0%
05:00–06:00
Tomorrow · 13 Aug
29
Poor
MOON 3%
Friday · 14 Aug
48
Fair
MOON 7%
23:00–00:00
Saturday · 15 Aug
89
Excellent
MOON 15%
00:00–01:00
Sunday · 16 Aug
61
Good
MOON 23%
00:00–01:00
Monday · 17 Aug
49
Fair
MOON 32%
00:00–01:00
Tuesday · 18 Aug
83
Excellent
MOON 42%
00:00–01:00
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Nearby locations

About this forecast

Conditions for Draper, 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 →