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Três de Maio

-27.773° S   54.240° W  ·  351 M
42 /100
PEAK
Marginal, but there is a 2 hours gap from 21:00.
BEST WINDOW 21:00–23:00 · ASTRO DARK 20:00–06:00 · MOON 0%
Transparency
0.27
Seeing
1.00
Cloud
45%
Moon
0%

Fair tonight

Hour by hour, local to Três de Maio. 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
18
25
35
42
6
5
4
8
4
4
8
11
0
BEST WINDOW
Low cloud
7%
2%
1%
2%
2%
0%
3%
2%
0%
10%
15%
1%
11%
72%
Mid cloud
18%
32%
67%
46%
33%
97%
97%
100%
90%
97%
95%
81%
58%
58%
High cloud
4%
16%
17%
21%
20%
52%
81%
80%
66%
85%
100%
100%
94%
74%
Transparency
0.33
0.27
0.23
0.22
0.21
0.21
0.21
0.10
0.19
0.19
0.10
0.10
0.10
0.10
Seeing
0.97
1.00
1.00
1.00
0.98
0.99
1.00
1.00
1.00
1.00
1.00
1.00
1.00
0.97
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
−24
Transparency
−21
Seeing
−0
Moonlight
−0
Darkness
−55
Score
0
CLOUD 27% LOW 7% MID 18% HIGH 4% SUN 2.1° MOON 5.1° / 0% WIND 2 TEMP 20°
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 41

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

18202200020406
CLOUD RETURNS 23:00
SET UP 20:30 · OBSERVE 21:00–23:00 · 2H · MEAN 48

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

18202200020406
CLOUD RETURNS 23:00MOONLIGHT IGNORED FOR THIS TARGET
SET UP 21:30 · OBSERVE 22:00–23:00 · 1H · MEAN 37

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

18202200020406
CLOUD RETURNS 23:00
NO USABLE WINDOW FOR THIS TARGET TONIGHT

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

18202200020406
CONDITIONS STAY BELOW THE USABLE THRESHOLD
SET UP 21:30 · OBSERVE 22:00–23:00 · 1H · MEAN 40

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

18202200020406
CLOUD RETURNS 23:00
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The next week of nights

Tonight · 12 Aug
42
Fair
MOON 0%
21:00–23:00
Tomorrow · 13 Aug
63
Good
MOON 3%
20:00–01:00
Friday · 14 Aug
70
Good
MOON 7%
20:00–04:00
Saturday · 15 Aug
55
Good
MOON 15%
03:00–04:00
Sunday · 16 Aug
57
Good
MOON 23%
03:00–04:00
Monday · 17 Aug
63
Good
MOON 32%
21:00–22:00
Tuesday · 18 Aug
21
Poor
MOON 42%
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Nearby locations

About this forecast

Conditions for Três de Maio, 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 →