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Marion

42.034° N   91.598° W  ·  262 M
67 /100
PEAK
Worth setting up — 1 hour of workable sky from 22:00.
BEST WINDOW 22:00–23:00 · ASTRO DARK 22:00–05:00 · MOON 1%
Transparency
0.23
Seeing
1.00
Cloud
1%
Moon
1%

Good tonight

Hour by hour, local to Marion. 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
0
17
67
32
30
30
31
31
30
17
0
BEST WINDOW
Low cloud
0%
0%
1%
0%
0%
2%
0%
0%
0%
0%
20%
Mid cloud
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
18%
High cloud
13%
1%
2%
95%
99%
99%
98%
98%
100%
99%
100%
Transparency
0.28
0.23
0.21
0.19
0.17
0.19
0.18
0.18
0.18
0.19
0.18
Seeing
1.00
1.00
1.00
0.97
0.99
0.99
0.99
1.00
0.98
1.00
1.00
Moon clear
0%
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
−7
Transparency
−27
Seeing
−0
Moonlight
−0
Darkness
−66
Score
0
CLOUD 14% LOW 0% MID 0% HIGH 13% SUN 1.2° MOON 4.7° / 0% WIND 2 TEMP 25°
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 21:30 · OBSERVE 22:00–23:00 · 1H · MEAN 67

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

202200020406
ASTRONOMICAL DARK FROM 22:00CLOUD RETURNS 23:00
SET UP 20:30 · OBSERVE 21:00–05:00 · 8H · MEAN 45

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

202200020406
TWILIGHT BEGINS 05:00MOONLIGHT IGNORED FOR THIS TARGET
SET UP 21:30 · OBSERVE 22:00–23:00 · 1H · MEAN 62

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

202200020406
ASTRONOMICAL DARK FROM 22:00CLOUD RETURNS 23:00
SET UP 21:30 · OBSERVE 22:00–23:00 · 1H · MEAN 52

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

202200020406
ASTRONOMICAL DARK FROM 22:00CLOUD RETURNS 23:00
SET UP 21:30 · OBSERVE 22:00–23:00 · 1H · MEAN 72

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

202200020406
ASTRONOMICAL DARK FROM 22:00CLOUD RETURNS 23:00
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The next week of nights

Tonight · 12 Aug
67
Good
MOON 0%
22:00–23:00
Tomorrow · 13 Aug
26
Poor
MOON 3%
Friday · 14 Aug
40
Fair
MOON 7%
22:00–00:00
Saturday · 15 Aug
30
Poor
MOON 15%
Sunday · 16 Aug
43
Fair
MOON 23%
01:00–02:00
Monday · 17 Aug
70
Good
MOON 32%
01:00–02:00
Tuesday · 18 Aug
33
Poor
MOON 42%
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Nearby locations

About this forecast

Conditions for Marion, Iowa, 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 →