CopperHead Ridge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the CopperHead Ridge Observatory clear sky chart from 2005-11-06 to 2026-01-17.

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	13% 6% 2 6% 4 4 4 4 6% 8% 43%	127445
	Night	14% 6% 2 6% 4 4 4 4 5% 7% 45%	124257
Transparency	Day	39% 4 12% 22% 18% 5%	131064
	Night	39% 4 10% 20% 21% 6%	128707
Seeing	Day	16% 8% 22% 24% 20% 10%	16936
	Night	16% 7% 23% 32% 19% 2	27056

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	16% 6% 2 5% 3 3 2 2 3 4 56%	4146
	11th to 20th	Day	11% 6% 2 4 3 3 2 2 4 4 58%	4114
	21st to end	Day	17% 6% 2 6% 4 3 4 2 3 4 48%	4466
February	1st to 10th	Day	14% 6% 2 6% 4 4 4 4 7% 7% 42%	1800
	11th to 20th	Day	21% 7% 2 4 3 3 3 3 4 5% 44%	1847
	21st to end	Day	18% 8% 3 6% 4 4 3 3 4 6% 41%	1736
March	1st to 10th	Day	19% 7% 2 5% 3 4 4 3 5% 7% 41%	4935
	11th to 20th	Day	9% 5% 2 5% 3 3 4 3 5% 7% 54%	4980
	21st to end	Day	16% 7% 2 6% 4 3 4 3 4 5% 46%	5465
April	1st to 10th	Day	11% 4 1 4 3 3 4 4 6% 7% 53%	2245
	11th to 20th	Day	13% 5% 2 5% 3 4 4 3 5% 6% 49%	2374
	21st to end	Day	12% 5% 2 6% 4 5% 4 4 6% 7% 45%	2507
May	1st to 10th	Day	10% 7% 3 7% 5% 5% 5% 5% 8% 11% 34%	5862
	11th to 20th	Day	20% 7% 3 7% 5% 5% 5% 4 6% 8% 30%	5861
	21st to end	Day	12% 5% 3 6% 4 5% 5% 4 6% 9% 41%	6433
June	1st to 10th	Day	9% 5% 2 7% 5% 5% 4 5% 7% 10% 41%	2600
	11th to 20th	Day	9% 5% 2 5% 5% 5% 4 5% 8% 12% 41%	2600
	21st to end	Day	5% 5% 2 6% 5% 6% 5% 6% 8% 12% 41%	2600
July	1st to 10th	Day	8% 6% 2 7% 5% 6% 5% 5% 7% 10% 37%	5900
	11th to 20th	Day	6% 6% 2 8% 6% 7% 7% 6% 9% 14% 29%	5900
	21st to end	Day	9% 7% 3 8% 6% 6% 6% 5% 7% 10% 31%	6424
August	1st to 10th	Day	17% 9% 3 8% 5% 5% 6% 6% 7% 10% 25%	4234
	11th to 20th	Day	8% 5% 3 8% 6% 6% 6% 5% 8% 10% 34%	4174
	21st to end	Day	5% 4 2 5% 4 4 4 4 7% 9% 51%	4323
September	1st to 10th	Day	9% 5% 2 5% 5% 5% 5% 4 6% 7% 48%	2320
	11th to 20th	Day	12% 7% 1 6% 4 4 5% 4 5% 8% 44%	2200
	21st to end	Day	19% 7% 2 7% 4 4 4 4 4 6% 39%	2200
October	1st to 10th	Day	12% 5% 2 5% 3 3 3 2 5% 6% 53%	2030
	11th to 20th	Day	12% 5% 2 4 3 4 2 2 4 5% 57%	2000
	21st to end	Day	13% 5% 2 5% 3 3 3 2 4 4 56%	2200
November	1st to 10th	Day	13% 5% 2 4 3 3 3 3 4 5% 55%	2057
	11th to 20th	Day	13% 4 2 5% 3 3 2 3 5% 7% 54%	1974
	21st to end	Day	14% 6% 2 4 4 3 4 3 4 6% 50%	1890
December	1st to 10th	Day	14% 7% 1 5% 3 3 3 3 4 5% 53%	3020
	11th to 20th	Day	16% 7% 2 6% 3 4 4 3 5% 5% 44%	3463
	21st to end	Day	19% 6% 2 5% 3 3 4 3 5% 7% 43%	4565
January	1st to 10th	Night	13% 5% 2 4 3 3 3 3 4 5% 56%	6019
	11th to 20th	Night	12% 6% 2 5% 3 3 3 2 3 4 58%	5979
	21st to end	Night	16% 7% 2 5% 3 3 3 3 5% 5% 47%	6490
February	1st to 10th	Night	15% 7% 2 6% 4 3 4 4 5% 6% 45%	2600
	11th to 20th	Night	21% 6% 3 4 3 3 4 3 4 5% 44%	2434
	21st to end	Night	15% 6% 2 5% 4 3 3 4 4 6% 46%	1892
March	1st to 10th	Night	17% 7% 3 6% 4 3 4 3 4 6% 45%	4918
	11th to 20th	Night	10% 5% 2 4 3 3 3 3 4 6% 56%	4980
	21st to end	Night	14% 5% 2 6% 4 4 3 3 5% 7% 48%	5467
April	1st to 10th	Night	13% 5% 2 5% 4 3 4 3 5% 7% 48%	2153
	11th to 20th	Night	12% 5% 3 6% 4 3 3 3 5% 7% 50%	1975
	21st to end	Night	14% 5% 2 5% 5% 4 4 3 5% 7% 47%	1910
May	1st to 10th	Night	13% 7% 3 8% 4 5% 5% 3 6% 8% 38%	4033
	11th to 20th	Night	17% 9% 3 7% 4 4 4 4 6% 9% 34%	4032
	21st to end	Night	14% 6% 2 5% 4 4 4 4 6% 9% 43%	4421
June	1st to 10th	Night	9% 5% 2 6% 6% 5% 7% 4 7% 11% 38%	1800
	11th to 20th	Night	10% 6% 2 6% 4 5% 5% 4 6% 12% 40%	1800
	21st to end	Night	7% 5% 3 6% 5% 5% 6% 5% 8% 11% 39%	1800
July	1st to 10th	Night	10% 8% 3 9% 6% 5% 7% 6% 7% 10% 31%	4058
	11th to 20th	Night	9% 7% 3 9% 7% 7% 7% 6% 9% 10% 26%	4057
	21st to end	Night	11% 7% 3 9% 6% 5% 6% 5% 8% 12% 28%	4427
August	1st to 10th	Night	19% 9% 3 8% 5% 5% 6% 4 7% 9% 24%	2915
	11th to 20th	Night	9% 6% 3 7% 6% 5% 6% 5% 8% 10% 34%	2875
	21st to end	Night	6% 5% 2 6% 4 4 5% 4 6% 8% 51%	3540
September	1st to 10th	Night	8% 6% 2 6% 4 4 5% 4 7% 9% 46%	2075
	11th to 20th	Night	13% 7% 2 7% 4 4 5% 4 6% 7% 42%	2200
	21st to end	Night	16% 8% 2 8% 5% 4 5% 4 5% 6% 37%	2200
October	1st to 10th	Night	12% 6% 2 6% 4 4 4 3 4 6% 50%	2368
	11th to 20th	Night	14% 5% 1 4 3 3 3 3 4 6% 56%	2400
	21st to end	Night	13% 6% 1 5% 3 3 3 2 3 5% 56%	2640
November	1st to 10th	Night	13% 6% 2 5% 3 3 3 2 4 5% 54%	2461
	11th to 20th	Night	12% 5% 2 5% 4 3 4 3 5% 5% 52%	2643
	21st to end	Night	14% 5% 2 4 3 3 3 4 5% 7% 51%	2730
December	1st to 10th	Night	15% 6% 2 5% 3 3 3 2 3 6% 52%	4380
	11th to 20th	Night	19% 8% 3 7% 4 4 4 3 4 4 41%	4952
	21st to end	Night	20% 5% 1 4 3 3 3 3 5% 7% 47%	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	36% 1 4 22% 31% 7%	4147
	11th to 20th	Day	32% 2 3 17% 37% 8%	4114
	21st to end	Day	42% 2 4 23% 23% 6%	4466
February	1st to 10th	Day	40% 4 10% 21% 20% 5%	1800
	11th to 20th	Day	43% 3 6% 22% 20% 6%	1856
	21st to end	Day	45% 3 8% 16% 20% 6%	1736
March	1st to 10th	Day	45% 2 6% 17% 19% 12%	4935
	11th to 20th	Day	31% 3 6% 19% 23% 18%	4980
	21st to end	Day	42% 2 6% 23% 20% 6%	5465
April	1st to 10th	Day	30% 4 11% 24% 25% 7%	2245
	11th to 20th	Day	35% 3 9% 23% 21% 8%	2374
	21st to end	Day	38% 4 12% 26% 17% 3	2507
May	1st to 10th	Day	43% 5% 18% 21% 11% 2	5897
	11th to 20th	Day	53% 5% 12% 20% 10% 1	5865
	21st to end	Day	40% 4 14% 21% 18% 3	6447
June	1st to 10th	Day	37% 5% 16% 26% 15% 1	2600
	11th to 20th	Day	34% 5% 20% 23% 15% 2	2600
	21st to end	Day	34% 7% 18% 25% 15% 1	2600
July	1st to 10th	Day	40% 8% 16% 21% 12% 2	5835
	11th to 20th	Day	41% 12% 27% 16% 4 1	5831
	21st to end	Day	45% 8% 16% 21% 8%	6240
August	1st to 10th	Day	52% 7% 17% 19% 5%	4221
	11th to 20th	Day	41% 8% 19% 21% 9% 2	4213
	21st to end	Day	28% 5% 16% 34% 15% 2	4323
September	1st to 10th	Day	35% 5% 14% 21% 20% 4	2320
	11th to 20th	Day	39% 5% 12% 20% 21% 3	2200
	21st to end	Day	46% 4 9% 20% 17% 4	2200
October	1st to 10th	Day	32% 3 7% 20% 28% 11%	3303
	11th to 20th	Day	22% 1 5% 22% 25% 25%	3240
	21st to end	Day	26% 2 7% 25% 23% 16%	3538
November	1st to 10th	Day	33% 2 7% 23% 27% 8%	2057
	11th to 20th	Day	32% 2 7% 25% 27% 6%	1974
	21st to end	Day	37% 3 7% 23% 25% 5%	1890
December	1st to 10th	Day	35% 3 6% 20% 28% 7%	3020
	11th to 20th	Day	43% 3 9% 16% 23% 6%	3460
	21st to end	Day	42% 2 9% 28% 17% 2	4565
January	1st to 10th	Night	33% 1 5% 19% 32% 10%	6019
	11th to 20th	Night	34% 1 4 18% 35% 8%	5979
	21st to end	Night	41% 2 5% 20% 27% 6%	6490
February	1st to 10th	Night	41% 3 9% 22% 21% 5%	2600
	11th to 20th	Night	44% 3 8% 17% 21% 7%	2436
	21st to end	Night	40% 2 9% 20% 22% 7%	1892
March	1st to 10th	Night	43% 1 5% 15% 26% 9%	4918
	11th to 20th	Night	31% 2 6% 17% 26% 18%	4980
	21st to end	Night	39% 2 6% 26% 22% 5%	5467
April	1st to 10th	Night	37% 3 9% 21% 25% 6%	2153
	11th to 20th	Night	35% 2 9% 22% 23% 9%	1975
	21st to end	Night	38% 4 12% 24% 18% 4	1910
May	1st to 10th	Night	44% 5% 16% 20% 15% 1	4060
	11th to 20th	Night	47% 6% 13% 19% 13% 1	4033
	21st to end	Night	39% 5% 11% 28% 15% 3	4429
June	1st to 10th	Night	39% 6% 15% 24% 14% 2	1800
	11th to 20th	Night	37% 6% 18% 22% 15% 2	1800
	21st to end	Night	36% 8% 16% 23% 13% 3	1800
July	1st to 10th	Night	45% 9% 16% 16% 12% 1	4015
	11th to 20th	Night	49% 13% 21% 12% 4 1	4006
	21st to end	Night	46% 8% 18% 21% 7%	4297
August	1st to 10th	Night	55% 7% 16% 15% 6%	2904
	11th to 20th	Night	40% 8% 21% 21% 9% 1	2902
	21st to end	Night	30% 6% 13% 31% 18% 2	3540
September	1st to 10th	Night	34% 6% 14% 22% 18% 6%	2075
	11th to 20th	Night	41% 7% 10% 19% 22% 2	2200
	21st to end	Night	47% 4 11% 18% 16% 4	2200
October	1st to 10th	Night	38% 4 7% 18% 26% 7%	3875
	11th to 20th	Night	24% 2 5% 23% 28% 19%	3899
	21st to end	Night	27% 2 5% 25% 25% 16%	4252
November	1st to 10th	Night	35% 3 6% 22% 24% 10%	2461
	11th to 20th	Night	34% 3 7% 20% 27% 10%	2643
	21st to end	Night	34% 3 6% 24% 27% 6%	2730
December	1st to 10th	Night	36% 2 6% 21% 29% 5%	4380
	11th to 20th	Night	48% 3 7% 16% 17% 9%	4954
	21st to end	Night	39% 2 12% 23% 22% 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	22% 17% 34% 20% 6%	330
	11th to 20th	Day	20% 19% 36% 20% 6%	318
	21st to end	Day	20% 14% 42% 19% 6%	330
February	1st to 10th	Day	17% 16% 38% 19% 10%	300
	11th to 20th	Day	35% 12% 37% 11% 5%	300
	21st to end	Day	24% 16% 33% 21% 7%	335
March	1st to 10th	Day	21% 10% 34% 25% 9% 1	500
	11th to 20th	Day	18% 13% 40% 22% 7%	500
	21st to end	Day	21% 13% 34% 25% 7%	550
April	1st to 10th	Day	20% 13% 30% 23% 12% 1	500
	11th to 20th	Day	13% 11% 32% 24% 16% 3	492
	21st to end	Day	16% 9% 27% 24% 22% 3	500
May	1st to 10th	Day	11% 12% 28% 28% 15% 6%	503
	11th to 20th	Day	17% 6% 19% 27% 20% 11%	527
	21st to end	Day	16% 5% 15% 24% 27% 14%	573
June	1st to 10th	Day	11% 4 15% 30% 28% 12%	530
	11th to 20th	Day	11% 3 14% 25% 27% 20%	530
	21st to end	Day	8% 2 10% 31% 32% 18%	530
July	1st to 10th	Day	12% 1 8% 20% 34% 25%	525
	11th to 20th	Day	6% 2 6% 25% 30% 30%	524
	21st to end	Day	8% 2 8% 24% 34% 24%	576
August	1st to 10th	Day	17% 2 12% 23% 28% 19%	526
	11th to 20th	Day	11% 2 8% 24% 32% 23%	519
	21st to end	Day	10% 2 9% 23% 33% 23%	583
September	1st to 10th	Day	12% 3 10% 22% 32% 21%	530
	11th to 20th	Day	14% 4 13% 21% 29% 19%	530
	21st to end	Day	22% 4 18% 27% 23% 6%	530
October	1st to 10th	Day	16% 5% 15% 29% 22% 13%	530
	11th to 20th	Day	13% 6% 22% 28% 24% 7%	530
	21st to end	Day	16% 8% 23% 28% 19% 6%	583
November	1st to 10th	Day	18% 7% 27% 28% 15% 6%	535
	11th to 20th	Day	13% 11% 35% 25% 14% 2	414
	21st to end	Day	14% 12% 30% 27% 14% 4	330
December	1st to 10th	Day	24% 11% 31% 28% 6% 1	330
	11th to 20th	Day	18% 11% 32% 27% 12% 1	330
	21st to end	Day	23% 14% 29% 23% 9% 2	363
January	1st to 10th	Night	19% 12% 35% 27% 7%	840
	11th to 20th	Night	19% 10% 37% 29% 4	825
	21st to end	Night	18% 10% 40% 29% 3	880
February	1st to 10th	Night	19% 11% 35% 32% 4	800
	11th to 20th	Night	25% 13% 37% 23% 1	783
	21st to end	Night	18% 15% 36% 28% 3	660
March	1st to 10th	Night	17% 11% 34% 32% 5%	800
	11th to 20th	Night	19% 11% 35% 27% 8%	800
	21st to end	Night	17% 10% 36% 31% 5%	880
April	1st to 10th	Night	16% 13% 33% 30% 9%	800
	11th to 20th	Night	15% 10% 32% 29% 14%	791
	21st to end	Night	15% 5% 29% 37% 13%	710
May	1st to 10th	Night	11% 7% 30% 37% 15% 1	600
	11th to 20th	Night	14% 7% 19% 35% 23% 1	591
	21st to end	Night	15% 3 13% 36% 30% 3	650
June	1st to 10th	Night	11% 3 12% 39% 31% 4	600
	11th to 20th	Night	11% 2 12% 35% 35% 6%	600
	21st to end	Night	9% 2 9% 36% 41% 4	600
July	1st to 10th	Night	8% 3 8% 30% 45% 7%	585
	11th to 20th	Night	7% 2 4 31% 46% 10%	582
	21st to end	Night	7% 2 7% 34% 40% 9%	657
August	1st to 10th	Night	16% 2 6% 30% 38% 8%	597
	11th to 20th	Night	12% 3 6% 31% 41% 7%	594
	21st to end	Night	9% 2 7% 31% 42% 8%	847
September	1st to 10th	Night	11% 2 7% 34% 38% 7%	800
	11th to 20th	Night	15% 4 10% 30% 36% 5%	800
	21st to end	Night	20% 5% 13% 34% 26% 2	800
October	1st to 10th	Night	14% 5% 16% 31% 29% 6%	800
	11th to 20th	Night	15% 6% 23% 35% 19% 2	800
	21st to end	Night	16% 6% 24% 33% 19% 2	880
November	1st to 10th	Night	17% 7% 22% 37% 16% 2	820
	11th to 20th	Night	15% 8% 29% 36% 12%	840
	21st to end	Night	15% 7% 30% 35% 13% 1	840
December	1st to 10th	Night	21% 8% 30% 34% 6%	840
	11th to 20th	Night	19% 7% 32% 34% 9%	840
	21st to end	Night	24% 9% 25% 35% 7%	924

Page generated at 2026-01-14 01:14:28. Version ac07

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