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Granite Bay

38.763° N   121.164° W  ·  132 M
65 /100
PEAK
Worth setting up — 7 hours of workable sky from 22:00.
BEST WINDOW 22:00–05:00 · ASTRO DARK 22:00–05:00 · MOON 1%
Transparency
0.97
Seeing
0.79
Cloud
34%
Moon
1%

Good tonight

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

Sky state
Lighter = daylight and twilight  ·  unshaded = astronomical dark
Score
20
21
22
23
00
01
02
03
04
05
06
0
17
51
47
41
65
48
39
60
37
0
BEST WINDOW
Low cloud
0%
0%
0%
0%
0%
1%
1%
1%
3%
4%
3%
Mid cloud
0%
0%
0%
0%
0%
0%
0%
1%
5%
3%
2%
High cloud
100%
98%
80%
84%
95%
40%
75%
91%
29%
41%
63%
Transparency
1.00
0.97
0.89
0.81
0.77
0.72
0.67
0.63
0.57
0.51
0.48
Seeing
0.76
0.78
0.78
0.79
0.78
0.76
0.76
0.74
0.71
0.74
0.74
Moon clear
0%
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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
20 Clouded out · 0/100
Starting from
100
Cloud
−55
Transparency
−0
Seeing
−3
Moonlight
−0
Darkness
−42
Score
0
CLOUD 100% LOW 0% MID 0% HIGH 100% SUN -0.2° MOON 4.0° / 0% WIND 4 TEMP 27°
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 21:30 · OBSERVE 22:00–05:00 · 7H · MEAN 48

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

202200020406
HIGH CLOUD CLEARS 22:00TWILIGHT BEGINS 05:00
SET UP 21:30 · OBSERVE 22:00–06:00 · 8H · MEAN 48

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

202200020406
HIGH CLOUD CLEARS 22:00CLOUD RETURNS 06:00MOONLIGHT IGNORED FOR THIS TARGET
SET UP 00:30 · OBSERVE 01:00–03:00 · 2H · MEAN 48

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

202200020406
HIGH CLOUD CLEARS 01:00CLOUD RETURNS 03:00
SET UP 00:30 · OBSERVE 01:00–02:00 · 1H · MEAN 48

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

202200020406
HIGH CLOUD CLEARS 01:00CLOUD RETURNS 02:00
SET UP 00:30 · OBSERVE 01:00–03:00 · 2H · MEAN 53

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

202200020406
HIGH CLOUD CLEARS 01:00CLOUD RETURNS 03:00
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The next week of nights

Tonight · 12 Aug
65
Good
MOON 1%
22:00–05:00
Tomorrow · 13 Aug
77
Excellent
MOON 3%
22:00–05:00
Friday · 14 Aug
88
Excellent
MOON 7%
22:00–00:00
Saturday · 15 Aug
85
Excellent
MOON 17%
23:00–00:00
Sunday · 16 Aug
42
Fair
MOON 25%
23:00–00:00
Monday · 17 Aug
37
Fair
MOON 35%
23:00–00:00
Tuesday · 18 Aug
45
Fair
MOON 44%
23:00–00:00
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Nearby locations

About this forecast

Conditions for Granite Bay, California, United States 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 →