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 2024-06-17.

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% 7% 44%	89520
	Night	14% 6% 2 6% 4 4 4 4 5% 7% 45%	89297
Transparency	Day	39% 4 11% 22% 19% 4	89293
	Night	40% 4 10% 21% 20% 5%	89128
Seeing	Day	16% 7% 22% 24% 21% 10%	14785
	Night	16% 7% 23% 32% 19% 2	24926

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	18% 4 2 4 3 3 2 2 3 5% 52%	2836
	11th to 20th	Day	14% 6% 2 6% 3 3 3 2 4 4 52%	2840
	21st to end	Day	23% 7% 2 6% 3 3 4 2 4 4 43%	3124
February	1st to 10th	Day	14% 6% 2 6% 5% 4 4 4 7% 7% 42%	1710
	11th to 20th	Day	20% 7% 2 4 3 3 3 3 4 5% 45%	1752
	21st to end	Day	19% 8% 3 6% 4 4 3 3 4 6% 40%	1651
March	1st to 10th	Day	23% 6% 2 5% 3 3 4 3 5% 7% 38%	3435
	11th to 20th	Day	10% 4 2 5% 3 3 4 4 5% 6% 55%	3480
	21st to end	Day	21% 7% 2 5% 4 3 3 3 5% 6% 42%	3815
April	1st to 10th	Day	11% 4 1 4 3 3 4 4 6% 7% 54%	2133
	11th to 20th	Day	13% 5% 2 5% 4 4 4 3 5% 7% 49%	2254
	21st to end	Day	13% 5% 2 5% 4 4 4 4 5% 7% 46%	2381
May	1st to 10th	Day	12% 8% 2 7% 6% 5% 5% 5% 7% 10% 34%	4082
	11th to 20th	Day	18% 7% 3 7% 4 4 4 4 6% 8% 36%	4081
	21st to end	Day	7% 4 2 5% 4 5% 5% 4 6% 10% 47%	4476
June	1st to 10th	Day	9% 5% 2 7% 5% 5% 4 5% 7% 10% 41%	2470
	11th to 20th	Day	9% 5% 2 5% 5% 5% 4 5% 8% 11% 41%	2420
	21st to end	Day	6% 5% 2 6% 5% 6% 5% 6% 8% 11% 39%	2340
July	1st to 10th	Day	7% 6% 2 7% 6% 6% 6% 5% 9% 10% 36%	2340
	11th to 20th	Day	6% 6% 2 7% 6% 6% 7% 6% 9% 12% 33%	2340
	21st to end	Day	7% 6% 3 7% 6% 6% 6% 5% 7% 10% 36%	2547
August	1st to 10th	Day	10% 6% 2 7% 6% 6% 6% 6% 8% 10% 33%	2327
	11th to 20th	Day	10% 6% 3 8% 7% 6% 7% 6% 9% 9% 30%	2303
	21st to end	Day	9% 6% 3 7% 5% 5% 5% 5% 7% 9% 39%	2387
September	1st to 10th	Day	10% 5% 2 5% 5% 4 5% 4 6% 7% 47%	2088
	11th to 20th	Day	12% 6% 1 6% 4 4 5% 4 5% 8% 45%	1980
	21st to end	Day	19% 7% 2 7% 4 4 4 3 4 6% 40%	1980
October	1st to 10th	Day	14% 5% 2 5% 3 3 3 2 5% 6% 53%	1828
	11th to 20th	Day	12% 5% 2 5% 3 4 2 2 4 5% 55%	1800
	21st to end	Day	13% 5% 2 5% 3 3 3 2 4 4 55%	1980
November	1st to 10th	Day	14% 5% 2 3 3 3 3 3 4 5% 56%	1857
	11th to 20th	Day	13% 4 2 5% 3 3 2 3 6% 6% 53%	1786
	21st to end	Day	14% 6% 2 4 4 3 3 4 4 6% 49%	1710
December	1st to 10th	Day	18% 8% 2 6% 4 4 4 3 5% 6% 41%	1710
	11th to 20th	Day	16% 5% 1 4 2 3 3 2 5% 6% 54%	2153
	21st to end	Day	17% 7% 2 5% 4 3 5% 4 6% 6% 41%	3124
January	1st to 10th	Night	15% 6% 2 5% 3 3 3 4 5% 5% 48%	4109
	11th to 20th	Night	14% 6% 2 6% 4 4 4 3 4 4 50%	4120
	21st to end	Night	23% 7% 2 6% 3 2 3 3 4 4 43%	4532
February	1st to 10th	Night	15% 7% 2 5% 4 3 4 4 5% 6% 45%	2470
	11th to 20th	Night	21% 6% 3 4 3 3 4 3 4 5% 45%	2309
	21st to end	Night	16% 6% 2 6% 4 3 3 4 4 6% 45%	1801
March	1st to 10th	Night	21% 9% 3 6% 5% 4 4 3 4 5% 36%	3418
	11th to 20th	Night	12% 6% 2 4 3 3 3 3 4 5% 54%	3480
	21st to end	Night	19% 5% 2 5% 4 3 3 3 4 6% 46%	3817
April	1st to 10th	Night	13% 5% 2 5% 4 3 4 3 5% 7% 49%	2046
	11th to 20th	Night	12% 5% 3 6% 4 3 3 3 5% 7% 50%	1875
	21st to end	Night	14% 5% 2 5% 5% 3 4 3 5% 6% 48%	1815
May	1st to 10th	Night	14% 6% 2 7% 4 4 4 3 5% 7% 43%	2813
	11th to 20th	Night	15% 9% 3 7% 4 3 4 4 5% 7% 38%	2812
	21st to end	Night	8% 5% 2 5% 4 4 5% 4 7% 11% 45%	3079
June	1st to 10th	Night	9% 5% 2 6% 6% 5% 6% 4 7% 12% 37%	1710
	11th to 20th	Night	10% 6% 2 6% 4 5% 4 4 7% 11% 41%	1683
	21st to end	Night	8% 5% 2 6% 5% 6% 6% 5% 8% 11% 38%	1620
July	1st to 10th	Night	6% 7% 3 9% 5% 5% 6% 5% 7% 12% 35%	1620
	11th to 20th	Night	6% 5% 2 7% 5% 7% 7% 6% 9% 11% 35%	1620
	21st to end	Night	7% 5% 2 5% 6% 5% 5% 5% 10% 14% 35%	1771
August	1st to 10th	Night	11% 6% 3 8% 5% 5% 6% 5% 8% 10% 32%	1611
	11th to 20th	Night	12% 7% 3 7% 6% 5% 6% 6% 8% 8% 33%	1598
	21st to end	Night	9% 7% 3 7% 5% 4 5% 4 9% 10% 38%	1949
September	1st to 10th	Night	8% 6% 2 6% 5% 4 5% 4 7% 9% 45%	1867
	11th to 20th	Night	12% 7% 2 6% 4 4 5% 4 6% 7% 43%	1980
	21st to end	Night	15% 8% 2 7% 4 4 5% 5% 6% 6% 38%	1980
October	1st to 10th	Night	13% 6% 2 5% 4 3 4 3 4 6% 49%	2130
	11th to 20th	Night	14% 5% 1 5% 3 3 3 3 4 6% 54%	2160
	21st to end	Night	13% 6% 1 5% 3 3 3 2 4 5% 56%	2376
November	1st to 10th	Night	14% 6% 2 5% 3 3 3 2 4 4 55%	2221
	11th to 20th	Night	13% 5% 2 5% 4 3 4 3 5% 5% 52%	2391
	21st to end	Night	14% 5% 2 4 2 3 3 4 5% 7% 50%	2470
December	1st to 10th	Night	19% 7% 2 6% 4 3 4 3 3 6% 43%	2470
	11th to 20th	Night	17% 6% 2 5% 3 3 3 3 4 5% 49%	3042
	21st to end	Night	20% 5% 1 4 3 3 4 3 5% 8% 43%	4532

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	38% 1 4 29% 21% 7%	2837
	11th to 20th	Day	37% 2 4 19% 33% 5%	2840
	21st to end	Day	47% 2 4 19% 23% 5%	3124
February	1st to 10th	Day	40% 4 9% 21% 20% 5%	1710
	11th to 20th	Day	43% 3 6% 22% 20% 6%	1761
	21st to end	Day	47% 4 9% 16% 19% 6%	1651
March	1st to 10th	Day	48% 2 6% 20% 16% 8%	3435
	11th to 20th	Day	30% 3 8% 23% 24% 12%	3480
	21st to end	Day	45% 2 7% 22% 21% 3	3815
April	1st to 10th	Day	29% 4 11% 24% 26% 7%	2133
	11th to 20th	Day	36% 3 9% 22% 22% 8%	2254
	21st to end	Day	38% 4 12% 26% 18% 4	2381
May	1st to 10th	Day	45% 4 16% 20% 11% 3	4120
	11th to 20th	Day	49% 3 12% 23% 12% 2	4085
	21st to end	Day	33% 4 16% 24% 20% 4	4489
June	1st to 10th	Day	37% 5% 16% 27% 14% 1	2470
	11th to 20th	Day	34% 5% 20% 24% 15% 2	2420
	21st to end	Day	36% 7% 18% 23% 14% 1	2340
July	1st to 10th	Day	40% 8% 16% 20% 13% 3	2275
	11th to 20th	Day	38% 9% 22% 20% 10% 1	2271
	21st to end	Day	40% 7% 20% 22% 10% 1	2405
August	1st to 10th	Day	42% 7% 17% 25% 9%	2314
	11th to 20th	Day	46% 8% 16% 19% 10% 1	2303
	21st to end	Day	39% 6% 19% 22% 11% 3	2387
September	1st to 10th	Day	36% 5% 14% 21% 19% 4	2088
	11th to 20th	Day	38% 5% 12% 20% 22% 3	1980
	21st to end	Day	46% 4 6% 22% 18% 3	1980
October	1st to 10th	Day	35% 3 8% 24% 26% 4	1828
	11th to 20th	Day	33% 2 7% 28% 22% 8%	1800
	21st to end	Day	33% 3 6% 24% 25% 9%	1980
November	1st to 10th	Day	32% 2 7% 22% 28% 8%	1857
	11th to 20th	Day	33% 2 7% 24% 27% 7%	1786
	21st to end	Day	36% 3 8% 23% 25% 5%	1710
December	1st to 10th	Day	44% 3 9% 22% 19% 4	1710
	11th to 20th	Day	33% 2 8% 22% 27% 9%	2150
	21st to end	Day	43% 2 7% 25% 20% 2	3124
January	1st to 10th	Night	39% 2 6% 21% 26% 6%	4109
	11th to 20th	Night	40% 2 5% 19% 28% 6%	4120
	21st to end	Night	46% 2 4 18% 23% 7%	4532
February	1st to 10th	Night	40% 3 9% 22% 21% 5%	2470
	11th to 20th	Night	44% 3 7% 17% 22% 8%	2311
	21st to end	Night	41% 2 10% 20% 21% 6%	1801
March	1st to 10th	Night	51% 2 6% 17% 18% 6%	3418
	11th to 20th	Night	34% 2 6% 18% 24% 15%	3480
	21st to end	Night	41% 3 6% 24% 21% 6%	3817
April	1st to 10th	Night	36% 3 9% 20% 25% 6%	2046
	11th to 20th	Night	35% 2 9% 22% 23% 9%	1875
	21st to end	Night	38% 3 11% 24% 19% 5%	1815
May	1st to 10th	Night	42% 4 16% 23% 14% 1	2840
	11th to 20th	Night	46% 4 11% 21% 16% 1	2813
	21st to end	Night	33% 5% 13% 31% 16% 2	3087
June	1st to 10th	Night	39% 6% 15% 24% 14% 2	1710
	11th to 20th	Night	37% 6% 18% 23% 15% 2	1683
	21st to end	Night	38% 8% 16% 22% 12% 4	1620
July	1st to 10th	Night	38% 9% 18% 19% 13% 3	1575
	11th to 20th	Night	38% 9% 21% 20% 9% 3	1566
	21st to end	Night	36% 8% 22% 22% 11% 1	1672
August	1st to 10th	Night	46% 8% 17% 19% 10% 1	1600
	11th to 20th	Night	44% 9% 16% 19% 10% 2	1598
	21st to end	Night	38% 7% 19% 24% 9% 3	1949
September	1st to 10th	Night	35% 7% 14% 21% 17% 6%	1867
	11th to 20th	Night	40% 7% 10% 19% 22% 2	1980
	21st to end	Night	46% 5% 11% 18% 18% 4	1980
October	1st to 10th	Night	38% 3 8% 23% 24% 4	2130
	11th to 20th	Night	33% 3 6% 27% 24% 7%	2160
	21st to end	Night	33% 2 6% 22% 26% 11%	2376
November	1st to 10th	Night	35% 3 6% 21% 25% 11%	2221
	11th to 20th	Night	34% 3 7% 20% 26% 11%	2391
	21st to end	Night	34% 3 6% 24% 27% 6%	2470
December	1st to 10th	Night	45% 3 8% 20% 20% 5%	2470
	11th to 20th	Night	39% 3 7% 18% 24% 10%	3044
	21st to end	Night	42% 2 8% 23% 23% 2	4532

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	23% 15% 34% 22% 7%	270
	11th to 20th	Day	21% 16% 37% 20% 6%	270
	21st to end	Day	21% 14% 40% 19% 6%	297
February	1st to 10th	Day	19% 15% 36% 20% 11%	270
	11th to 20th	Day	32% 12% 39% 11% 6%	270
	21st to end	Day	26% 16% 33% 20% 5%	306
March	1st to 10th	Day	20% 10% 34% 25% 9% 1	460
	11th to 20th	Day	18% 13% 42% 21% 7%	460
	21st to end	Day	22% 12% 33% 25% 8%	506
April	1st to 10th	Day	20% 13% 30% 23% 13% 1	460
	11th to 20th	Day	13% 12% 30% 24% 17% 4	452
	21st to end	Day	17% 9% 27% 23% 21% 3	460
May	1st to 10th	Day	12% 12% 26% 28% 15% 6%	463
	11th to 20th	Day	16% 6% 18% 27% 21% 12%	487
	21st to end	Day	15% 3 14% 24% 29% 16%	529
June	1st to 10th	Day	10% 3 14% 30% 29% 13%	490
	11th to 20th	Day	11% 3 13% 25% 27% 21%	475
	21st to end	Day	9% 2 12% 32% 29% 16%	450
July	1st to 10th	Day	12% 1 8% 20% 32% 26%	445
	11th to 20th	Day	6% 1 6% 25% 31% 30%	444
	21st to end	Day	7% 3 8% 24% 35% 24%	488
August	1st to 10th	Day	14% 2 11% 22% 29% 22%	446
	11th to 20th	Day	12% 1 7% 23% 31% 25%	439
	21st to end	Day	11% 2 8% 24% 33% 24%	495
September	1st to 10th	Day	13% 2 9% 18% 34% 24%	450
	11th to 20th	Day	13% 3 12% 20% 32% 20%	450
	21st to end	Day	22% 4 16% 26% 25% 6%	450
October	1st to 10th	Day	18% 5% 14% 28% 23% 11%	450
	11th to 20th	Day	13% 6% 21% 28% 24% 8%	450
	21st to end	Day	15% 8% 23% 30% 19% 5%	495
November	1st to 10th	Day	20% 5% 25% 26% 17% 7%	455
	11th to 20th	Day	14% 10% 34% 25% 14% 3	346
	21st to end	Day	14% 8% 31% 27% 15% 4	270
December	1st to 10th	Day	23% 9% 30% 29% 7% 1	270
	11th to 20th	Day	17% 11% 30% 27% 14% 1	270
	21st to end	Day	24% 13% 29% 23% 10% 2	297
January	1st to 10th	Night	20% 10% 36% 27% 7%	760
	11th to 20th	Night	20% 9% 37% 30% 5%	760
	21st to end	Night	19% 10% 39% 29% 3	836
February	1st to 10th	Night	18% 11% 35% 32% 4	760
	11th to 20th	Night	24% 13% 38% 23% 1	743
	21st to end	Night	18% 15% 35% 28% 3	628
March	1st to 10th	Night	17% 11% 34% 33% 5%	760
	11th to 20th	Night	19% 11% 34% 27% 8%	760
	21st to end	Night	18% 10% 35% 32% 6%	836
April	1st to 10th	Night	15% 13% 33% 29% 9%	760
	11th to 20th	Night	15% 10% 31% 30% 14%	751
	21st to end	Night	16% 6% 30% 36% 12%	675
May	1st to 10th	Night	11% 7% 29% 36% 15% 1	570
	11th to 20th	Night	14% 7% 19% 35% 24% 1	561
	21st to end	Night	14% 2 12% 37% 32% 3	617
June	1st to 10th	Night	11% 3 12% 39% 31% 4	570
	11th to 20th	Night	10% 2 12% 33% 36% 6%	561
	21st to end	Night	10% 1 10% 36% 39% 4	540
July	1st to 10th	Night	8% 3 7% 30% 45% 7%	525
	11th to 20th	Night	7% 2 4 32% 47% 10%	522
	21st to end	Night	7% 2 6% 35% 41% 8%	591
August	1st to 10th	Night	14% 2 6% 30% 40% 8%	537
	11th to 20th	Night	13% 3 5% 29% 42% 7%	534
	21st to end	Night	10% 2 7% 30% 43% 8%	761
September	1st to 10th	Night	11% 2 6% 33% 40% 8%	720
	11th to 20th	Night	15% 3 10% 29% 38% 5%	720
	21st to end	Night	19% 5% 13% 34% 27% 2	720
October	1st to 10th	Night	15% 5% 16% 30% 28% 6%	720
	11th to 20th	Night	15% 5% 24% 33% 20% 3	720
	21st to end	Night	16% 6% 23% 35% 18% 2	792
November	1st to 10th	Night	17% 7% 22% 36% 17% 2	740
	11th to 20th	Night	15% 8% 28% 37% 12%	760
	21st to end	Night	15% 6% 29% 35% 14% 1	760
December	1st to 10th	Night	21% 8% 29% 35% 7%	760
	11th to 20th	Night	19% 6% 32% 34% 9%	760
	21st to end	Night	25% 8% 24% 35% 8%	836

Page generated at 2024-06-14 13:06:12. Version ac07

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