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Tonight · Sat, 19 September 2026

Nelson tonight

41.271°S 173.284°E ·11 m ·Nelson, New Zealand

28
/100
Poor conditions
at peak

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

Site darkness · peer measure
Brightened skyNot multiplied into the conditions score
20.7–21.2 mag/arcsec²

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

See target outlook ↓Planet observing times →
Tonight in context · local sky & season

September historically: 6.3 qualifying nights/month on average (2005–2024). Regional cloud and darkness history, not tonight’s probability or a comparison with the conditions score.

A qualifying historical night has at least 3 hours of astronomical darkness and mean nighttime cloud ≤30%. This does not measure steady air or target visibility. Seasonal history →

Saturn: about 7.3h 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
None tonight
Window quality
—
Astronomical dark
20:00 – 05:00
Moon
First quarter, 57%
Transparency at peak
0.44
Seeing at peak (est.)
0.29
Visual limit (modelled)
5.0–6.5 mag
Tonight's limiting factor
Seeing

Seeing 0.29, estimated from surface wind. Expect to drop magnification. What this means →

Also limiting: Low cloud. See the guide →

The night, hour by hour

Colour = score · Luminance = everything else
Sky state
Shaded = daylight and twilight  ·  unshaded = astronomical dark
7
7
9
12
27
28
4
28
39
Score
Low cloud
100%
86%
95%
76%
81%
72%
67%
41%
41%
77%
49%
27%
48%
Mid cloud
98%
99%
100%
48%
31%
44%
37%
27%
23%
73%
15%
1%
0%
High cloud
0%
0%
0%
1%
5%
0%
0%
0%
0%
0%
0%
0%
0%
Transparency
0.48
0.46
0.47
0.31
0.23
0.17
0.24
0.25
0.31
0.10
0.40
0.44
0.49
Seeing
0.75
0.74
0.67
0.47
0.58
0.63
0.57
0.64
0.38
0.39
0.33
0.29
0.32
Moon clear
54%
54%
55%
55%
56%
56%
56%
57%
57%
down
down
down
down
18
19
20
21
22
23
00
01
02
03
04
05
06
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 Fair · 39/100
Starting from
100
Cloud
−28
Transparency
−16
Seeing
−10
Moonlight
−0
Darkness
−7
Score
39
CLOUD 28% LOW 27% MID 1% HIGH 0% SUN -16.1° MOON -16.0° / 58% WIND 9 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.

NO USABLE WINDOW FOR THIS TARGET TONIGHT

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

18202200020406
MOON UP AND BRIGHTSITE GLOW LIMITS THIS TARGET
SET UP 04:30 · OBSERVE 05:00–06:00 · 1H · MEAN 41

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

18202200020406
CLOUD BREAKS 05:00CLOUD RETURNS 06:00SEEING STAYS SOFT THROUGHOUT
NO USABLE WINDOW FOR THIS TARGET TONIGHT

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

18202200020406
MOON UP AND BRIGHT
NO USABLE WINDOW FOR THIS TARGET TONIGHT

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

18202200020406
MOON UP AND BRIGHT
NO USABLE WINDOW FOR THIS TARGET TONIGHT

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

18202200020406
MOON UP AND BRIGHT

Deep-sky visual is your current default.

A darker option

Aoraki Mackenzie (Lake Tekapo)

381 km away · Natural-dark sky · 21.8–21.9 mag/arcsec²

66conditions tonight
See the trade-off →
Latest verified night · 2026-09-17

Prediction, meet observation.

All comparisons →
6 matches3 discrepanciesSatellite saw 32.8 points less cloud.
HIMAWARI cloud mask · ~12h reference3 of 9 sampled hours diverged.Cloud only · 9 astronomically dark hours

Recent cloud comparisons · 24 recorded nights →

The next week of nights

Tonight · 19 Sept
28
Poor

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

MOON 57%
Tomorrow · 20 Sept
58
Good
MOON 65%
20:00–00:00
Monday · 21 Sept
49
Fair
MOON 73%
20:00–00:00
Tuesday · 22 Sept
63
Good
MOON 82%
00:00–01:00
Wednesday · 23 Sept
55
Good
MOON 89%
00:00–01:00
Thursday · 24 Sept
57
Good
MOON 94%
00:00–01:00
Friday · 25 Sept
46
Fair
MOON 98%
00:00–01:00

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

Tonight · 19 Sept · forecast times
Sky state
Shaded = daylight and twilight  ·  unshaded = astronomical dark
7
7
9
12
27
28
4
28
39
Score
Low cloud
100%
86%
95%
76%
81%
72%
67%
41%
41%
77%
49%
27%
48%
Mid cloud
98%
99%
100%
48%
31%
44%
37%
27%
23%
73%
15%
1%
0%
High cloud
0%
0%
0%
1%
5%
0%
0%
0%
0%
0%
0%
0%
0%
Transparency
0.48
0.46
0.47
0.31
0.23
0.17
0.24
0.25
0.31
0.10
0.40
0.44
0.49
Seeing
0.75
0.74
0.67
0.47
0.58
0.63
0.57
0.64
0.38
0.39
0.33
0.29
0.32
Moon clear
54%
54%
55%
55%
56%
56%
56%
57%
57%
down
down
down
down
18
19
20
21
22
23
00
01
02
03
04
05
06

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

Tomorrow · 20 Sept · forecast times
Sky state
Shaded = daylight and twilight  ·  unshaded = astronomical dark
10
58
58
44
45
27
26
43
55
55
43
Score
Low cloud
0%
0%
0%
3%
31%
28%
41%
36%
18%
9%
16%
9%
9%
Mid cloud
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
High cloud
0%
0%
0%
0%
0%
6%
53%
69%
38%
24%
15%
31%
15%
Transparency
0.53
0.41
0.45
0.44
0.45
0.46
0.39
0.34
0.35
0.37
0.39
0.34
0.34
Seeing
0.89
0.75
0.75
0.83
0.95
0.97
0.86
0.85
0.79
0.77
0.78
0.81
0.75
Moon clear
63%
64%
64%
64%
65%
65%
65%
66%
66%
67%
down
down
down
18
19
20
21
22
23
00
01
02
03
04
05
06

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

Monday · 21 Sept · forecast times
Sky state
Shaded = daylight and twilight  ·  unshaded = astronomical dark
8
48
49
45
44
31
31
14
13
18
Score
Low cloud
7%
8%
12%
10%
14%
20%
46%
39%
69%
46%
59%
96%
22%
Mid cloud
0%
0%
0%
0%
3%
1%
2%
19%
36%
71%
38%
99%
95%
High cloud
0%
0%
0%
0%
0%
0%
0%
0%
0%
2%
0%
0%
34%
Transparency
0.57
0.56
0.53
0.52
0.51
0.48
0.47
0.42
0.33
0.29
0.26
0.10
0.20
Seeing
0.38
0.42
0.48
0.50
0.44
0.47
0.58
0.70
0.83
0.97
0.89
0.91
0.87
Moon clear
72%
72%
73%
73%
73%
74%
74%
75%
75%
75%
76%
down
down
18
19
20
21
22
23
00
01
02
03
04
05
06

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

Tuesday · 22 Sept · forecast times
Sky state
Shaded = daylight and twilight  ·  unshaded = astronomical dark
63
Score
Low cloud
1%
1%
0%
Mid cloud
1%
0%
1%
High cloud
0%
0%
0%
Transparency
0.73
0.62
0.57
Seeing
0.71
0.79
1.00
Moon clear
80%
82%
down
18
00
06

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

Wednesday · 23 Sept · forecast times
Sky state
Shaded = daylight and twilight  ·  unshaded = astronomical dark
55
Score
Low cloud
2%
0%
0%
Mid cloud
11%
0%
0%
High cloud
0%
0%
0%
Transparency
0.39
0.31
0.58
Seeing
0.96
1.00
1.00
Moon clear
87%
89%
down
18
00
06

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

Thursday · 24 Sept · forecast times
Sky state
Shaded = daylight and twilight  ·  unshaded = astronomical dark
57
Score
Low cloud
2%
0%
5%
Mid cloud
8%
0%
48%
High cloud
0%
0%
46%
Transparency
0.21
0.41
0.28
Seeing
1.00
0.99
0.93
Moon clear
93%
94%
down
18
00
06

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

Friday · 25 Sept · forecast times
Sky state
Shaded = daylight and twilight  ·  unshaded = astronomical dark
46
Score
Low cloud
22%
10%
1%
Mid cloud
13%
6%
21%
High cloud
0%
0%
16%
Transparency
0.17
0.32
0.33
Seeing
1.00
1.00
1.00
Moon clear
97%
98%
down
18
00
06

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

Planning a trip?

Compare the next eight weekends → · Best months to visit → · Moonless nights →

About this forecast

Exact-coordinate weather, sky geometry and site context.

Full method →20-year baseline →
Sources and scoring details openclose

Conditions for Nelson, Nelson, New Zealand 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.