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Rio Claro

-22.723° S   44.136° W  ·  464 M
71 /100
PEAK
Worth setting up — 11 hours of workable sky from 19:00.
BEST WINDOW 19:00–06:00 · ASTRO DARK 19:00–06:00 · MOON 0%
Transparency
0.34
Seeing
1.00
Cloud
5%
Moon
0%

Good tonight

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

Sky state
Lighter = daylight and twilight  ·  unshaded = astronomical dark
Score
18
19
20
21
22
23
00
01
02
03
04
05
06
07
0
46
63
71
69
63
67
48
45
39
40
62
0
0
BEST WINDOW
Low cloud
7%
9%
7%
3%
0%
0%
0%
0%
0%
0%
0%
0%
6%
3%
Mid cloud
3%
2%
0%
0%
0%
0%
0%
0%
0%
1%
2%
1%
1%
2%
High cloud
66%
55%
14%
2%
6%
19%
8%
60%
66%
81%
73%
16%
36%
75%
Transparency
0.37
0.32
0.32
0.34
0.34
0.32
0.30
0.31
0.30
0.27
0.24
0.23
0.22
0.23
Seeing
0.94
0.97
1.00
0.99
0.87
0.85
0.90
0.93
0.94
0.96
0.96
0.95
0.95
0.93
Moon clear
down
down
down
down
down
down
down
down
down
down
down
down
down
1%
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
18 Clouded out · 0/100
Starting from
100
Cloud
−43
Transparency
−15
Seeing
−1
Moonlight
−0
Darkness
−42
Score
0
CLOUD 70% LOW 7% MID 3% HIGH 66% SUN -5.3° MOON -1.6° / 0% WIND 3 TEMP 20°
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 18:30 · OBSERVE 19:00–06:00 · 11H · MEAN 55

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

18202200020406
ASTRONOMICAL DARK FROM 19:00CLOUD RETURNS 06:00
SET UP 18:30 · OBSERVE 19:00–06:00 · 11H · MEAN 65

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

18202200020406
ASTRONOMICAL DARK FROM 19:00CLOUD RETURNS 06:00MOONLIGHT IGNORED FOR THIS TARGET
SET UP 18:30 · OBSERVE 19:00–02:00 · 7H · MEAN 54

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

18202200020406
ASTRONOMICAL DARK FROM 19:00
SET UP 19:30 · OBSERVE 20:00–01:00 · 5H · MEAN 52

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

18202200020406
HIGH CLOUD CLEARS 20:00CLOUD RETURNS 01:00
SET UP 18:30 · OBSERVE 19:00–03:00 · 8H · MEAN 60

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

18202200020406
ASTRONOMICAL DARK FROM 19:00CLOUD RETURNS 03:00
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The next week of nights

Tonight · 12 Aug
71
Good
MOON 0%
19:00–06:00
Tomorrow · 13 Aug
74
Good
MOON 3%
19:00–06:00
Friday · 14 Aug
41
Fair
MOON 7%
19:00–20:00
Saturday · 15 Aug
26
Poor
MOON 15%
Sunday · 16 Aug
30
Poor
MOON 23%
Monday · 17 Aug
72
Good
MOON 32%
21:00–22:00
Tuesday · 18 Aug
69
Good
MOON 42%
21:00–22:00
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Nearby locations

About this forecast

Conditions for Rio Claro, Brazil 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 →