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Porto Ferreira

-21.854° S   47.479° W  ·  564 M
80 /100
PEAK
A genuinely good night — 8 hours of clear, dark sky from 20:00.
BEST WINDOW 20:00–04:00 · ASTRO DARK 20:00–06:00 · MOON 0%
Transparency
0.70
Seeing
1.00
Cloud
9%
Moon
0%

Excellent tonight

Hour by hour, local to Porto Ferreira. 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
63
80
78
69
73
41
48
53
50
30
10
1
0
BEST WINDOW
Low cloud
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
Mid cloud
11%
9%
8%
6%
6%
9%
1%
2%
7%
20%
30%
83%
98%
81%
High cloud
59%
6%
1%
5%
23%
3%
85%
66%
49%
41%
87%
88%
84%
74%
Transparency
0.77
0.70
0.65
0.62
0.60
0.53
0.45
0.45
0.46
0.48
0.48
0.49
0.46
0.46
Seeing
1.00
1.00
1.00
1.00
1.00
0.96
0.94
0.94
0.93
0.96
1.00
1.00
1.00
1.00
Moon clear
0%
down
down
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
18 Clouded out · 0/100
Starting from
100
Cloud
−39
Transparency
−6
Seeing
−0
Moonlight
−0
Darkness
−55
Score
0
CLOUD 63% LOW 0% MID 11% HIGH 59% SUN -2.1° MOON 1.3° / 0% WIND 2 TEMP 26°
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 19:00–04:00 · 9H · MEAN 60

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

18202200020406
HIGH CLOUD CLEARS 19:00CLOUD RETURNS 04:00
SET UP 18:30 · OBSERVE 19:00–04:00 · 9H · MEAN 69

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

18202200020406
HIGH CLOUD CLEARS 19:00CLOUD RETURNS 04:00MOONLIGHT IGNORED FOR THIS TARGET
SET UP 18:30 · OBSERVE 19:00–00:00 · 5H · MEAN 68

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

18202200020406
HIGH CLOUD CLEARS 19:00CLOUD RETURNS 00:00
SET UP 18:30 · OBSERVE 19:00–00:00 · 5H · MEAN 61

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

18202200020406
HIGH CLOUD CLEARS 19:00CLOUD RETURNS 00:00
SET UP 18:30 · OBSERVE 19:00–00:00 · 5H · MEAN 72

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

18202200020406
HIGH CLOUD CLEARS 19:00CLOUD RETURNS 00:00
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The next week of nights

Tonight · 12 Aug
80
Excellent
MOON 0%
20:00–04:00
Tomorrow · 13 Aug
89
Excellent
MOON 3%
20:00–06:00
Friday · 14 Aug
77
Excellent
MOON 7%
21:00–04:00
Saturday · 15 Aug
79
Excellent
MOON 15%
21:00–22:00
Sunday · 16 Aug
89
Excellent
MOON 23%
21:00–22:00
Monday · 17 Aug
87
Excellent
MOON 32%
03:00–04:00
Tuesday · 18 Aug
90
Excellent
MOON 42%
03:00–04:00
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Nearby locations

About this forecast

Conditions for Porto Ferreira, 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 →