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Tonight · Sat, 10 October 2026

Cerro Tololo Observatory stargazing forecast tonight

Hourly clear-sky conditions for observing: cloud by layer, transparency, estimated seeing, moonlight and true astronomical darkness.

30.169°S 70.806°W ·2200 m ·Coquimbo, Chile

68
/100
Good conditions
at peak

Worth setting up — 2 hours of workable sky from 04:00.

Site darkness · peer measure
Threatened dark skyNot multiplied into the conditions score
21.7–21.8 mag/arcsec²

The score describes tonight’s conditions. Site darkness helps you choose what to observe.

See target outlook ↓Planet observing times →
Best months at Cerro Tololo Observatory, Coquimbo →Moonless nights →
Tonight in context · local sky & season

Saturn: about 8.3h above 20° during this observing night’s darkness. Longest sampled dark-time opportunity among our four planet targets; not a weather ranking. Planet times →

Position calculations use roughly 20-minute samples. Clouds, skyglow and local obstructions still matter. Milky Way timing →

Best window
04:00 – 06:00
Window quality
55 / 100 avg
Astronomical dark
22:00 – 06:00
Moon
New moon, 1%
Transparency at peak
0.95
Seeing at peak (est.)
0.65
Visual limit (modelled)
6.0–7.0 mag
Tonight's limiting factor
Seeing

Seeing 0.65, estimated from surface wind. Expect to drop magnification. What this means →

The night, hour by hour

Colour = score · Luminance = everything else
Sky state
Shaded = daylight and twilight  ·  unshaded = astronomical dark
31
23
28
40
39
29
18
42
68
48
Score
BEST WINDOW · 3 H
Low cloud
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
2%
Mid cloud
67%
48%
31%
37%
32%
24%
59%
58%
37%
21%
12%
29%
High cloud
77%
13%
92%
89%
66%
72%
47%
99%
59%
13%
51%
31%
Transparency
0.22
0.39
0.15
0.59
0.68
0.56
0.58
0.58
0.96
0.95
0.98
0.93
Seeing
1.00
1.00
1.00
1.00
1.00
0.98
1.00
0.94
0.75
0.65
0.74
1.00
Moon clear
0%
down
down
down
down
down
down
down
down
down
down
down
20
21
22
23
00
01
02
03
04
05
06
07
Inspect

Cloud tracks show clear sky — a longer bar is better. The figure inside each track is the raw measurement.

Score inspectorWhy this hour scored what it did Open peakClose
05 Good · 68/100
Starting from
100
Cloud
−25
Transparency
−1
Seeing
−6
Moonlight
−0
Darkness
−0
Score
68
CLOUD 31% LOW 0% MID 21% HIGH 13% SUN -27.6° MOON -28.0° / 1% WIND 6 TEMP 8°
Excellent 75+ Good 55+ Fair 35+ Poor 15+ Not worth it Seeing is estimated from surface wind — see how we score.

What can you actually do tonight?

This is GoodSeeing’s decision layer: the same forecast is weighted for your target and site darkness. Planetary work barely cares about moonlight; long exposures can fail on high cloud a visual observer would barely notice. Your choice is remembered on this device and becomes the default for new alert rules.

SET UP 03:30 · OBSERVE 04:00–07:00 · 3H · MEAN 47

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

202200020406
HIGH CLOUD CLEARS 04:00TWILIGHT BEGINS 07:00
SET UP 03:30 · OBSERVE 04:00–07:00 · 3H · MEAN 50

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

202200020406
HIGH CLOUD CLEARS 04:00TWILIGHT BEGINS 07:00MOONLIGHT IGNORED FOR THIS TARGET
SET UP 04:30 · OBSERVE 05:00–07:00 · 2H · MEAN 52

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

202200020406
HIGH CLOUD CLEARS 05:00TWILIGHT BEGINS 07:00
SET UP 04:30 · OBSERVE 05:00–06:00 · 1H · MEAN 56

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

202200020406
HIGH CLOUD CLEARS 05:00CLOUD RETURNS 06:00
SET UP 04:30 · OBSERVE 05:00–07:00 · 2H · MEAN 51

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

202200020406
HIGH CLOUD CLEARS 05:00TWILIGHT BEGINS 07:00

Deep-sky visual is your current default.

A darker option

Paranal Observatory

617 km away · Natural-dark sky · 21.9–21.9 mag/arcsec²

94conditions tonight
See the trade-off →

The next week of nights

Tonight · 10 Oct
68
Good
MOON 1%
04:00–06:00
Tomorrow · 11 Oct
72
Good
MOON 3%
22:00–02:00
Monday · 12 Oct
69
Good
MOON 6%
22:00–04:00
Tuesday · 13 Oct
15
Poor

Cloud or fog is the strongest score limit at the best sampled time.

MOON 13%
Wednesday · 14 Oct
83
Excellent
MOON 21%
03:00–04:00
Thursday · 15 Oct
83
Excellent
MOON 29%
03:00–04:00
Friday · 16 Oct
8
Not worth it

Cloud or fog is the strongest score limit at the best sampled time.

MOON 37%

Open a night for its forecast times. Later forecasts may have wider time steps; missing hours are not interpolated.

Tonight · 10 Oct · forecast times
Sky state
Shaded = daylight and twilight  ·  unshaded = astronomical dark
31
23
28
40
39
29
18
42
68
48
Score
Low cloud
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
2%
Mid cloud
67%
48%
31%
37%
32%
24%
59%
58%
37%
21%
12%
29%
High cloud
77%
13%
92%
89%
66%
72%
47%
99%
59%
13%
51%
31%
Transparency
0.22
0.39
0.15
0.59
0.68
0.56
0.58
0.58
0.96
0.95
0.98
0.93
Seeing
1.00
1.00
1.00
1.00
1.00
0.98
1.00
0.94
0.75
0.65
0.74
1.00
Moon clear
0%
down
down
down
down
down
down
down
down
down
down
down
20
21
22
23
00
01
02
03
04
05
06
07

Cloud tracks show clear sky — a longer bar is better. The figure inside each track is the raw measurement.

Tomorrow · 11 Oct · forecast times
Sky state
Shaded = daylight and twilight  ·  unshaded = astronomical dark
41
72
67
58
37
26
9
5
3
3
Score
Low cloud
16%
15%
2%
5%
15%
24%
38%
74%
77%
80%
77%
59%
Mid cloud
31%
23%
3%
5%
1%
17%
13%
28%
35%
52%
63%
73%
High cloud
3%
6%
6%
8%
6%
23%
33%
19%
2%
5%
0%
0%
Transparency
0.56
0.50
0.45
0.44
0.43
0.45
0.40
0.34
0.28
0.27
0.30
0.37
Seeing
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
Moon clear
2%
2%
down
down
down
down
down
down
down
down
down
down
20
21
22
23
00
01
02
03
04
05
06
07

Cloud tracks show clear sky — a longer bar is better. The figure inside each track is the raw measurement.

Monday · 12 Oct · forecast times
Sky state
Shaded = daylight and twilight  ·  unshaded = astronomical dark
15
40
45
56
66
67
69
Score
Low cloud
70%
54%
23%
15%
8%
8%
11%
11%
1%
Mid cloud
63%
45%
36%
31%
18%
6%
2%
2%
0%
High cloud
11%
0%
0%
0%
0%
0%
0%
0%
87%
Transparency
0.10
0.33
0.41
0.33
0.33
0.37
0.43
0.45
0.71
Seeing
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
Moon clear
6%
6%
7%
down
down
down
down
down
9%
20
21
22
23
00
01
02
03
09

Cloud tracks show clear sky — a longer bar is better. The figure inside each track is the raw measurement.

Tuesday · 13 Oct · forecast times
Sky state
Shaded = daylight and twilight  ·  unshaded = astronomical dark
32
15
Score
Low cloud
18%
39%
78%
15%
Mid cloud
45%
2%
10%
1%
High cloud
60%
0%
0%
0%
Transparency
0.65
0.36
0.35
0.73
Seeing
0.89
1.00
1.00
1.00
Moon clear
10%
12%
down
down
15
21
03
09

Cloud tracks show clear sky — a longer bar is better. The figure inside each track is the raw measurement.

Wednesday · 14 Oct · forecast times
Sky state
Shaded = daylight and twilight  ·  unshaded = astronomical dark
49
83
Score
Low cloud
34%
3%
0%
0%
Mid cloud
28%
2%
0%
0%
High cloud
3%
0%
0%
0%
Transparency
0.69
0.35
0.57
0.83
Seeing
0.92
1.00
1.00
1.00
Moon clear
17%
19%
down
down
15
21
03
09

Cloud tracks show clear sky — a longer bar is better. The figure inside each track is the raw measurement.

Thursday · 15 Oct · forecast times
Sky state
Shaded = daylight and twilight  ·  unshaded = astronomical dark
45
83
Score
Low cloud
9%
0%
0%
0%
Mid cloud
16%
0%
0%
0%
High cloud
3%
0%
0%
91%
Transparency
0.80
0.28
0.58
0.99
Seeing
0.92
1.00
1.00
1.00
Moon clear
24%
27%
down
down
15
21
03
09

Cloud tracks show clear sky — a longer bar is better. The figure inside each track is the raw measurement.

Friday · 16 Oct · forecast times
Sky state
Shaded = daylight and twilight  ·  unshaded = astronomical dark
3
8
Score
Low cloud
12%
29%
16%
2%
Mid cloud
98%
89%
95%
14%
High cloud
28%
91%
25%
0%
Transparency
0.71
0.21
0.37
0.82
Seeing
0.85
1.00
1.00
1.00
Moon clear
33%
35%
down
down
15
21
03
09

Cloud tracks show clear sky — a longer bar is better. The figure inside each track is the raw measurement.

About this forecast

Exact-coordinate weather, sky geometry and site context.

Full method →
Sources and scoring details openclose

Conditions for Cerro Tololo Observatory, Coquimbo, Chile 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 astronomical twilight. Site darkness is shown separately, then used only where artificial skyglow physically changes moon contrast, haze scattering, visual limits and target suitability.