Gold Ridge observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gold Ridge observatory clear sky chart from 2005-11-06 to 2026-05-02.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	12% 7% 2 6% 5% 5% 5% 4 6% 8% 41%	131841
	Night	12% 7% 2 6% 4 4 4 4 5% 7% 44%	130668
Transparency	Day	39% 5% 11% 20% 18% 6%	135629
	Night	38% 5% 10% 20% 20% 7%	134949
Seeing	Day	16% 10% 24% 24% 17% 8%	16654
	Night	15% 9% 23% 29% 20% 4	26710

By Month

Percentage Cloud Cover SE (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	17% 11% 4 5% 3 3 3 2 4 4 43%	5258
	11th to 20th	Day	9% 7% 3 4 3 2 2 3 4 5% 57%	5280
	21st to end	Day	23% 10% 3 7% 4 4 3 3 4 4 36%	6353
February	1st to 10th	Day	15% 9% 2 6% 5% 4 4 3 4 6% 40%	2100
	11th to 20th	Day	19% 10% 3 6% 4 4 3 3 3 5% 41%	2048
	21st to end	Day	18% 7% 2 6% 5% 4 4 4 4 6% 39%	1730
March	1st to 10th	Day	18% 9% 3 7% 5% 4 4 4 6% 5% 35%	4580
	11th to 20th	Day	11% 6% 3 6% 4 3 3 3 4 8% 48%	5081
	21st to end	Day	15% 6% 2 7% 4 4 4 3 5% 6% 43%	5586
April	1st to 10th	Day	12% 7% 3 5% 5% 4 4 4 5% 7% 45%	2485
	11th to 20th	Day	11% 6% 2 6% 5% 3 5% 3 5% 7% 49%	2494
	21st to end	Day	8% 5% 2 5% 4 5% 5% 3 6% 7% 48%	2589
May	1st to 10th	Day	13% 7% 2 7% 5% 5% 5% 5% 7% 9% 36%	5875
	11th to 20th	Day	17% 8% 3 7% 5% 5% 6% 5% 7% 8% 31%	5861
	21st to end	Day	10% 6% 2 7% 5% 5% 5% 4 6% 9% 41%	6433
June	1st to 10th	Day	10% 8% 3 9% 6% 7% 6% 5% 7% 10% 31%	2600
	11th to 20th	Day	6% 4 2 5% 6% 6% 7% 6% 8% 11% 40%	2600
	21st to end	Day	6% 4 2 7% 7% 7% 6% 5% 10% 9% 36%	2600
July	1st to 10th	Day	6% 6% 3 9% 6% 7% 7% 6% 9% 11% 31%	5900
	11th to 20th	Day	5% 4 2 7% 5% 6% 7% 6% 9% 14% 34%	5900
	21st to end	Day	7% 7% 3 10% 8% 8% 8% 7% 9% 11% 22%	6424
August	1st to 10th	Day	5% 4 2 5% 4 6% 6% 6% 8% 13% 41%	4050
	11th to 20th	Day	8% 5% 2 5% 5% 5% 5% 4 6% 10% 46%	3849
	21st to end	Day	7% 4 2 5% 4 5% 6% 4 6% 9% 48%	4312
September	1st to 10th	Day	9% 6% 3 7% 6% 7% 5% 4 7% 7% 39%	2268
	11th to 20th	Day	15% 6% 2 5% 4 4 5% 4 6% 7% 42%	2200
	21st to end	Day	12% 6% 3 6% 4 4 4 4 4 7% 46%	2200
October	1st to 10th	Day	11% 5% 2 5% 3 4 4 4 4 6% 52%	2200
	11th to 20th	Day	11% 5% 1 4 3 3 3 2 4 6% 57%	2170
	21st to end	Day	13% 5% 1 5% 4 3 3 3 3 5% 55%	2135
November	1st to 10th	Day	10% 7% 2 5% 4 4 3 3 4 5% 52%	1852
	11th to 20th	Day	13% 5% 1 4 4 3 3 3 4 6% 53%	1890
	21st to end	Day	13% 8% 1 4 4 3 4 2 6% 7% 47%	1890
December	1st to 10th	Day	18% 7% 2 4 4 3 3 3 5% 6% 45%	3020
	11th to 20th	Day	13% 8% 3 8% 5% 4 4 3 4 4 42%	3463
	21st to end	Day	19% 8% 3 6% 4 3 4 3 4 6% 40%	4565
January	1st to 10th	Night	16% 9% 3 6% 3 4 4 3 4 6% 42%	7635
	11th to 20th	Night	13% 8% 3 6% 4 3 3 3 4 6% 47%	7680
	21st to end	Night	19% 11% 2 6% 3 3 3 3 3 4 41%	7823
February	1st to 10th	Night	14% 8% 3 6% 5% 4 3 4 5% 6% 43%	2520
	11th to 20th	Night	19% 9% 3 6% 4 3 3 3 4 4 41%	2458
	21st to end	Night	17% 7% 3 6% 4 4 4 4 5% 6% 40%	2076
March	1st to 10th	Night	20% 10% 3 7% 5% 4 4 3 5% 6% 33%	5493
	11th to 20th	Night	10% 7% 2 4 3 4 4 4 5% 7% 50%	5095
	21st to end	Night	13% 6% 2 7% 5% 4 4 3 5% 6% 45%	5588
April	1st to 10th	Night	11% 6% 2 5% 5% 5% 4 4 6% 7% 45%	2151
	11th to 20th	Night	12% 5% 2 4 4 3 2 3 5% 7% 51%	2075
	21st to end	Night	8% 5% 2 5% 4 4 4 3 5% 6% 52%	2028
May	1st to 10th	Night	10% 6% 3 7% 5% 5% 5% 5% 7% 9% 38%	4042
	11th to 20th	Night	17% 8% 3 7% 5% 5% 5% 4 6% 8% 32%	4032
	21st to end	Night	9% 5% 2 5% 4 4 5% 5% 8% 11% 43%	4421
June	1st to 10th	Night	5% 6% 2 6% 5% 6% 7% 5% 9% 11% 38%	1800
	11th to 20th	Night	3 4 2 5% 4 5% 5% 6% 8% 13% 46%	1800
	21st to end	Night	5% 5% 2 6% 5% 5% 5% 4 8% 11% 45%	1800
July	1st to 10th	Night	6% 6% 3 9% 6% 6% 6% 6% 8% 11% 33%	4058
	11th to 20th	Night	4 4 2 7% 6% 5% 7% 5% 10% 13% 37%	4057
	21st to end	Night	6% 8% 3 9% 6% 6% 7% 6% 9% 12% 28%	4427
August	1st to 10th	Night	5% 4 2 5% 4 5% 6% 5% 8% 12% 45%	3094
	11th to 20th	Night	5% 4 2 6% 5% 4 5% 4 6% 9% 50%	3200
	21st to end	Night	8% 5% 2 5% 4 4 4 4 6% 8% 50%	3586
September	1st to 10th	Night	7% 5% 2 6% 4 5% 5% 5% 7% 10% 44%	2110
	11th to 20th	Night	11% 6% 2 6% 4 4 4 3 6% 7% 46%	2200
	21st to end	Night	10% 5% 2 6% 3 4 4 3 5% 8% 51%	2200
October	1st to 10th	Night	9% 5% 2 5% 3 3 3 3 4 6% 58%	2200
	11th to 20th	Night	9% 5% 2 5% 3 3 3 3 4 5% 58%	2227
	21st to end	Night	12% 6% 2 5% 3 3 3 3 4 4 57%	2701
November	1st to 10th	Night	11% 6% 2 5% 4 3 3 3 4 5% 56%	2666
	11th to 20th	Night	12% 7% 2 4 3 3 3 2 3 6% 55%	2730
	21st to end	Night	12% 7% 2 6% 4 4 4 3 4 6% 48%	2730
December	1st to 10th	Night	15% 8% 3 6% 3 3 3 2 4 5% 49%	4380
	11th to 20th	Night	15% 7% 3 6% 4 3 4 3 4 6% 46%	4952
	21st to end	Night	18% 9% 3 6% 3 4 3 3 4 6% 40%	6633

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	45% 3 5% 23% 19% 4	5259
	11th to 20th	Day	30% 3 4 21% 32% 11%	5280
	21st to end	Day	54% 2 4 12% 19% 9%	6353
February	1st to 10th	Day	45% 4 7% 17% 22% 5%	2100
	11th to 20th	Day	47% 3 4 19% 21% 7%	2058
	21st to end	Day	46% 4 6% 14% 21% 9%	1730
March	1st to 10th	Day	49% 4 8% 13% 20% 7%	4580
	11th to 20th	Day	36% 4 6% 15% 22% 17%	5081
	21st to end	Day	42% 3 9% 18% 21% 6%	5586
April	1st to 10th	Day	39% 4 10% 21% 19% 7%	2485
	11th to 20th	Day	36% 3 6% 19% 27% 8%	2494
	21st to end	Day	33% 6% 11% 23% 24% 4	2589
May	1st to 10th	Day	43% 5% 15% 21% 15% 2	5910
	11th to 20th	Day	48% 5% 17% 21% 8% 1	5865
	21st to end	Day	39% 5% 13% 25% 17% 1	6447
June	1st to 10th	Day	46% 9% 14% 19% 12% 1	2600
	11th to 20th	Day	33% 9% 20% 23% 14% 2	2600
	21st to end	Day	38% 11% 17% 21% 11% 2	2600
July	1st to 10th	Day	41% 9% 22% 21% 6%	5835
	11th to 20th	Day	36% 11% 31% 18% 4	5831
	21st to end	Day	50% 11% 19% 17% 3	6240
August	1st to 10th	Day	31% 9% 14% 33% 13%	4037
	11th to 20th	Day	33% 7% 17% 28% 14% 2	3885
	21st to end	Day	32% 7% 16% 22% 21% 3	4311
September	1st to 10th	Day	42% 7% 12% 18% 16% 5%	2268
	11th to 20th	Day	39% 7% 11% 20% 21% 2	2200
	21st to end	Day	38% 5% 10% 19% 22% 6%	2200
October	1st to 10th	Day	26% 4 5% 13% 34% 18%	3590
	11th to 20th	Day	19% 2 4 17% 30% 28%	3514
	21st to end	Day	24% 3 5% 20% 37% 10%	3424
November	1st to 10th	Day	34% 3 7% 17% 27% 11%	1852
	11th to 20th	Day	32% 3 7% 18% 28% 12%	1890
	21st to end	Day	37% 4 8% 18% 25% 8%	1890
December	1st to 10th	Day	42% 3 6% 18% 25% 7%	3020
	11th to 20th	Day	45% 3 6% 18% 20% 7%	3460
	21st to end	Day	45% 4 6% 23% 20% 2	4565
January	1st to 10th	Night	44% 3 6% 24% 19% 3	7636
	11th to 20th	Night	40% 3 5% 18% 25% 9%	7680
	21st to end	Night	48% 3 3 15% 24% 7%	7823
February	1st to 10th	Night	43% 3 6% 19% 20% 8%	2520
	11th to 20th	Night	47% 3 4 18% 20% 8%	2459
	21st to end	Night	44% 3 9% 15% 19% 10%	2076
March	1st to 10th	Night	51% 3 6% 15% 16% 8%	5493
	11th to 20th	Night	34% 4 8% 15% 22% 17%	5095
	21st to end	Night	40% 4 6% 22% 21% 9%	5588
April	1st to 10th	Night	38% 5% 10% 18% 20% 9%	2151
	11th to 20th	Night	33% 4 6% 23% 24% 10%	2075
	21st to end	Night	32% 4 12% 25% 21% 5%	2028
May	1st to 10th	Night	40% 7% 15% 21% 15% 2	4069
	11th to 20th	Night	49% 6% 14% 22% 8% 1	4033
	21st to end	Night	33% 6% 17% 27% 16% 2	4429
June	1st to 10th	Night	35% 11% 17% 20% 15% 1	1800
	11th to 20th	Night	26% 10% 24% 24% 14% 2	1800
	21st to end	Night	32% 8% 21% 21% 15% 4	1800
July	1st to 10th	Night	41% 9% 21% 21% 7%	4015
	11th to 20th	Night	35% 12% 31% 16% 5% 1	4006
	21st to end	Night	44% 11% 25% 16% 4	4297
August	1st to 10th	Night	29% 8% 14% 36% 12% 1	3083
	11th to 20th	Night	29% 7% 17% 31% 14% 2	3230
	21st to end	Night	30% 7% 16% 20% 25% 3	3586
September	1st to 10th	Night	34% 9% 17% 19% 15% 7%	2110
	11th to 20th	Night	36% 8% 10% 23% 19% 3	2200
	21st to end	Night	32% 6% 10% 22% 22% 8%	2200
October	1st to 10th	Night	25% 3 7% 16% 33% 16%	3590
	11th to 20th	Night	17% 3 3 17% 30% 30%	3622
	21st to end	Night	23% 2 3 22% 33% 16%	4362
November	1st to 10th	Night	31% 3 10% 17% 26% 14%	2666
	11th to 20th	Night	32% 3 5% 19% 27% 13%	2730
	21st to end	Night	37% 3 7% 18% 25% 9%	2730
December	1st to 10th	Night	40% 2 5% 20% 27% 6%	4380
	11th to 20th	Night	40% 3 11% 15% 25% 6%	4954
	21st to end	Night	44% 3 6% 24% 20% 2	6633

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	29% 23% 35% 11% 2	330
	11th to 20th	Day	25% 27% 29% 13% 5% 1	330
	21st to end	Day	27% 26% 32% 12% 2 1	363
February	1st to 10th	Day	22% 24% 37% 14% 3	330
	11th to 20th	Day	35% 22% 32% 10% 2	330
	21st to end	Day	29% 19% 39% 11% 2	273
March	1st to 10th	Day	27% 19% 33% 17% 2 2	330
	11th to 20th	Day	23% 18% 34% 17% 7% 1	531
	21st to end	Day	22% 18% 31% 23% 6% 1	594
April	1st to 10th	Day	20% 17% 31% 20% 10% 2	540
	11th to 20th	Day	16% 15% 32% 24% 11% 2	532
	21st to end	Day	15% 10% 31% 31% 11% 3	540
May	1st to 10th	Day	15% 14% 28% 25% 14% 5%	507
	11th to 20th	Day	13% 6% 25% 31% 15% 9%	527
	21st to end	Day	13% 6% 19% 31% 18% 13%	573
June	1st to 10th	Day	13% 4 18% 32% 22% 12%	530
	11th to 20th	Day	7% 4 16% 28% 25% 20%	530
	21st to end	Day	8% 3 15% 25% 31% 18%	530
July	1st to 10th	Day	7% 2 9% 29% 32% 22%	525
	11th to 20th	Day	6% 2 8% 24% 33% 27%	524
	21st to end	Day	7% 2 9% 24% 37% 21%	576
August	1st to 10th	Day	11% 2 12% 25% 30% 19%	526
	11th to 20th	Day	10% 2 10% 30% 31% 18%	519
	21st to end	Day	12% 3 10% 28% 30% 17%	583
September	1st to 10th	Day	9% 4 12% 30% 31% 14%	530
	11th to 20th	Day	15% 3 12% 29% 30% 9%	530
	21st to end	Day	13% 4 20% 26% 28% 9%	530
October	1st to 10th	Day	14% 3 28% 33% 17% 6%	530
	11th to 20th	Day	13% 7% 24% 32% 20% 4	530
	21st to end	Day	17% 10% 26% 26% 18% 3	518
November	1st to 10th	Day	20% 9% 29% 31% 9% 2	330
	11th to 20th	Day	15% 17% 39% 22% 7% 1	330
	21st to end	Day	15% 18% 42% 17% 7% 1	330
December	1st to 10th	Day	28% 20% 33% 16% 2 1	330
	11th to 20th	Day	21% 20% 33% 18% 6% 2	330
	21st to end	Day	28% 14% 34% 19% 4	363
January	1st to 10th	Night	24% 18% 31% 23% 4	840
	11th to 20th	Night	23% 16% 31% 24% 6%	840
	21st to end	Night	22% 17% 35% 22% 4	924
February	1st to 10th	Night	21% 13% 33% 28% 5%	840
	11th to 20th	Night	26% 17% 31% 24% 2	823
	21st to end	Night	22% 18% 35% 21% 3	692
March	1st to 10th	Night	18% 16% 33% 28% 6%	840
	11th to 20th	Night	18% 13% 35% 24% 9%	840
	21st to end	Night	16% 14% 31% 30% 8%	924
April	1st to 10th	Night	15% 12% 34% 27% 10% 1	681
	11th to 20th	Night	16% 10% 30% 30% 13% 1	623
	21st to end	Night	9% 9% 24% 40% 17% 1	630
May	1st to 10th	Night	10% 7% 27% 32% 22% 2	603
	11th to 20th	Night	12% 6% 20% 34% 24% 5%	591
	21st to end	Night	12% 1 13% 36% 34% 5%	650
June	1st to 10th	Night	9% 2 12% 38% 34% 6%	600
	11th to 20th	Night	4 1 12% 28% 38% 17%	600
	21st to end	Night	6% 1 8% 32% 43% 9%	600
July	1st to 10th	Night	8% 2 8% 22% 46% 14%	585
	11th to 20th	Night	4 1 4 20% 50% 20%	582
	21st to end	Night	8% 1 7% 24% 45% 15%	657
August	1st to 10th	Night	7% 1 6% 26% 43% 17%	597
	11th to 20th	Night	10% 2 6% 27% 47% 9%	594
	21st to end	Night	13% 3 7% 29% 37% 12%	660
September	1st to 10th	Night	9% 2 13% 29% 39% 9%	710
	11th to 20th	Night	14% 3 12% 29% 37% 6%	800
	21st to end	Night	13% 3 14% 32% 34% 5%	800
October	1st to 10th	Night	11% 4 21% 36% 23% 6%	800
	11th to 20th	Night	11% 8% 23% 33% 21% 4	800
	21st to end	Night	15% 9% 23% 33% 18% 3	880
November	1st to 10th	Night	15% 7% 22% 33% 21% 2	820
	11th to 20th	Night	16% 10% 31% 28% 13% 1	840
	21st to end	Night	17% 14% 28% 30% 12%	840
December	1st to 10th	Night	23% 13% 28% 27% 8%	840
	11th to 20th	Night	23% 9% 31% 27% 9% 1	840
	21st to end	Night	26% 13% 26% 28% 7%	924

Page generated at 2026-04-29 01:21:42. Version ac07

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