Copper Mountain
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Copper Mountain clear sky chart from 2005-11-06 to 2024-11-01.

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	4 8% 4 10% 6% 5% 5% 4 5% 6% 43%	101314
	Night	1 5% 3 10% 6% 5% 4 4 6% 7% 50%	97880
Transparency	Day	38% 7% 11% 19% 18% 6%	101065
	Night	30% 8% 15% 24% 18% 5%	97719
Seeing	Day	16% 23% 29% 20% 10% 2	15519
	Night	8% 17% 30% 31% 13% 1	25547

By Month

Percentage Cloud Cover SW (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	4 4 18% 11% 10% 4 2 4 6% 38%	2538
	11th to 20th	Day	7% 6% 18% 9% 10% 4 2 4 4 37%	2764
	21st to end	Day	7% 7% 16% 6% 4 3 3 4 6% 43%	3146
February	1st to 10th	Day	5% 7% 19% 8% 6% 4 3 4 6% 38%	1710
	11th to 20th	Day	5% 5% 15% 8% 7% 4 2 4 6% 43%	1768
	21st to end	Day	4 6% 18% 10% 5% 4 3 3 6% 41%	1570
March	1st to 10th	Day	7% 7% 18% 7% 4 3 2 3 5% 43%	3221
	11th to 20th	Day	1 9% 8% 14% 6% 5% 4 3 5% 6% 39%	3490
	21st to end	Day	1 12% 9% 19% 8% 5% 4 3 4 5% 31%	3974
April	1st to 10th	Day	1 10% 5% 11% 6% 5% 5% 3 5% 5% 43%	2280
	11th to 20th	Day	1 16% 8% 14% 6% 4 4 3 4 6% 34%	2251
	21st to end	Day	2 16% 7% 11% 7% 5% 5% 3 5% 5% 33%	2280
May	1st to 10th	Day	2 15% 10% 14% 7% 5% 5% 4 6% 6% 28%	3975
	11th to 20th	Day	4 12% 3 7% 5% 5% 6% 5% 7% 9% 37%	4388
	21st to end	Day	3 9% 3 6% 4 4 5% 5% 6% 9% 46%	4825
June	1st to 10th	Day	6% 7% 2 5% 5% 5% 5% 4 7% 9% 46%	2660
	11th to 20th	Day	7% 7% 2 5% 4 4 5% 4 5% 6% 51%	2660
	21st to end	Day	5% 6% 2 6% 5% 5% 5% 5% 7% 7% 49%	2660
July	1st to 10th	Day	7% 6% 2 6% 4 3 4 3 4 5% 56%	4430
	11th to 20th	Day	6% 5% 2 7% 6% 6% 6% 6% 8% 9% 38%	4430
	21st to end	Day	9% 6% 2 7% 6% 4 5% 4 5% 6% 46%	4531
August	1st to 10th	Day	11% 8% 2 8% 6% 6% 6% 5% 7% 8% 32%	4092
	11th to 20th	Day	8% 6% 2 9% 6% 5% 6% 4 6% 7% 40%	3815
	21st to end	Day	7% 5% 2 8% 6% 6% 6% 5% 6% 7% 41%	4180
September	1st to 10th	Day	9% 7% 3 5% 5% 4 4 3 4 5% 52%	2280
	11th to 20th	Day	8% 7% 2 6% 4 4 5% 3 4 5% 52%	2280
	21st to end	Day	6% 8% 2 5% 4 4 3 3 4 5% 57%	2052
October	1st to 10th	Day	5% 8% 3 6% 5% 4 4 3 4 5% 52%	1900
	11th to 20th	Day	3 9% 3 5% 3 3 3 2 4 6% 58%	1900
	21st to end	Day	3 9% 4 10% 3 3 3 2 4 5% 55%	2090
November	1st to 10th	Day	6% 3 6% 5% 4 2 3 5% 5% 61%	1675
	11th to 20th	Day	8% 3 8% 5% 3 3 3 3 8% 57%	1710
	21st to end	Day	1 6% 4 10% 7% 3 2 2 4 5% 56%	1549
December	1st to 10th	Day	5% 5% 14% 9% 7% 4 3 4 7% 42%	1520
	11th to 20th	Day	6% 5% 11% 8% 4 3 3 6% 9% 45%	1926
	21st to end	Day	5% 5% 16% 9% 5% 4 3 5% 7% 40%	2794
January	1st to 10th	Night	2 3 18% 11% 7% 4 3 5% 7% 41%	4417
	11th to 20th	Night	3 6% 17% 11% 8% 6% 3 4 5% 38%	4236
	21st to end	Night	5% 6% 17% 8% 5% 5% 4 4 6% 39%	4521
February	1st to 10th	Night	3 4 15% 10% 9% 4 4 5% 7% 41%	2470
	11th to 20th	Night	4 4 13% 8% 6% 5% 5% 6% 7% 43%	2297
	21st to end	Night	4 4 15% 9% 6% 5% 3 5% 6% 43%	1884
March	1st to 10th	Night	4 7% 15% 6% 5% 4 3 5% 7% 44%	3641
	11th to 20th	Night	7% 7% 13% 4 3 3 3 4 7% 48%	3490
	21st to end	Night	1 10% 6% 14% 6% 5% 4 4 6% 6% 38%	3674
April	1st to 10th	Night	6% 3 9% 6% 4 5% 4 5% 8% 49%	1900
	11th to 20th	Night	1 10% 5% 10% 5% 4 5% 4 6% 6% 44%	1877
	21st to end	Night	2 12% 4 9% 4 3 4 3 5% 7% 48%	1900
May	1st to 10th	Night	2 10% 6% 9% 4 4 4 3 7% 7% 43%	2989
	11th to 20th	Night	3 9% 3 8% 4 6% 5% 5% 9% 8% 40%	2517
	21st to end	Night	2 8% 2 5% 4 4 4 3 5% 7% 55%	2762
June	1st to 10th	Night	3 3 1 3 3 3 4 3 7% 9% 60%	1520
	11th to 20th	Night	3 4 1 3 3 3 4 3 5% 6% 65%	1520
	21st to end	Night	2 4 1 4 3 2 3 4 7% 9% 62%	1520
July	1st to 10th	Night	4 3 1 4 4 4 4 3 5% 7% 60%	2540
	11th to 20th	Night	2 3 1 3 3 4 6% 5% 8% 11% 54%	2540
	21st to end	Night	3 3 1 4 3 4 5% 5% 7% 8% 58%	3028
August	1st to 10th	Night	4 4 1 6% 5% 4 6% 5% 9% 11% 44%	2847
	11th to 20th	Night	3 3 1 4 3 4 4 5% 8% 10% 55%	3022
	21st to end	Night	3 3 1 4 4 5% 7% 6% 7% 11% 50%	3487
September	1st to 10th	Night	4 4 2 4 3 4 4 3 7% 8% 58%	1900
	11th to 20th	Night	3 4 1 4 4 3 3 3 5% 7% 62%	1900
	21st to end	Night	3 5% 1 5% 3 3 3 3 6% 7% 62%	2125
October	1st to 10th	Night	2 5% 2 6% 4 3 3 3 5% 7% 59%	2280
	11th to 20th	Night	1 5% 3 4 3 3 3 2 4 5% 66%	2280
	21st to end	Night	2 8% 3 9% 3 3 2 2 4 6% 58%	2508
November	1st to 10th	Night	4 3 5% 4 3 4 2 4 6% 65%	2388
	11th to 20th	Night	4 4 9% 4 3 3 3 4 7% 58%	2470
	21st to end	Night	4 4 9% 5% 4 4 3 6% 7% 54%	2626
December	1st to 10th	Night	4 4 10% 7% 6% 4 3 4 7% 51%	2660
	11th to 20th	Night	4 4 11% 7% 6% 5% 4 6% 8% 45%	3271
	21st to end	Night	5% 3 14% 8% 6% 5% 4 5% 8% 43%	4873

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	37% 11% 13% 17% 18% 3	2539
	11th to 20th	Day	46% 10% 17% 15% 9% 2	2764
	21st to end	Day	38% 8% 14% 22% 13% 5%	3146
February	1st to 10th	Day	47% 7% 15% 15% 12% 4	1710
	11th to 20th	Day	41% 6% 11% 20% 16% 6%	1777
	21st to end	Day	44% 4 12% 18% 16% 6%	1570
March	1st to 10th	Day	41% 5% 10% 20% 18% 5%	3221
	11th to 20th	Day	40% 10% 14% 26% 8% 2	3490
	21st to end	Day	51% 6% 14% 19% 9% 1	3974
April	1st to 10th	Day	41% 6% 13% 19% 15% 6%	2280
	11th to 20th	Day	50% 5% 12% 16% 14% 2	2254
	21st to end	Day	50% 6% 10% 23% 11% 1	2280
May	1st to 10th	Day	50% 8% 11% 15% 13% 1	3975
	11th to 20th	Day	36% 10% 15% 24% 14% 1	4392
	21st to end	Day	30% 8% 12% 23% 23% 4	4825
June	1st to 10th	Day	32% 8% 13% 24% 18% 5%	2660
	11th to 20th	Day	32% 5% 10% 19% 23% 12%	2660
	21st to end	Day	32% 6% 9% 19% 24% 10%	2660
July	1st to 10th	Day	30% 5% 7% 10% 23% 25%	4361
	11th to 20th	Day	38% 7% 11% 20% 17% 9%	4355
	21st to end	Day	38% 6% 9% 14% 16% 17%	4388
August	1st to 10th	Day	48% 6% 14% 13% 15% 4	4078
	11th to 20th	Day	43% 6% 11% 13% 19% 7%	3853
	21st to end	Day	40% 6% 10% 17% 21% 7%	4179
September	1st to 10th	Day	35% 5% 8% 15% 26% 11%	2280
	11th to 20th	Day	35% 5% 10% 18% 24% 8%	2280
	21st to end	Day	30% 4 8% 25% 28% 5%	2052
October	1st to 10th	Day	34% 5% 8% 21% 24% 7%	1900
	11th to 20th	Day	27% 4 9% 30% 24% 7%	1900
	21st to end	Day	33% 4 9% 28% 20% 6%	2090
November	1st to 10th	Day	24% 7% 13% 22% 30% 4	1675
	11th to 20th	Day	25% 6% 16% 27% 20% 6%	1710
	21st to end	Day	31% 4 11% 28% 17% 9%	1549
December	1st to 10th	Day	40% 8% 14% 21% 14% 4	1520
	11th to 20th	Day	34% 7% 13% 27% 18% 1	1924
	21st to end	Day	37% 11% 9% 16% 21% 7%	2794
January	1st to 10th	Night	37% 10% 14% 22% 14% 3	4417
	11th to 20th	Night	42% 9% 17% 19% 10% 3	4236
	21st to end	Night	36% 12% 14% 21% 13% 4	4521
February	1st to 10th	Night	39% 8% 15% 20% 14% 3	2470
	11th to 20th	Night	36% 7% 14% 22% 18% 3	2298
	21st to end	Night	38% 6% 14% 20% 17% 6%	1884
March	1st to 10th	Night	33% 8% 12% 23% 20% 4	3641
	11th to 20th	Night	30% 12% 14% 29% 13% 3	3490
	21st to end	Night	39% 10% 19% 23% 8% 1	3674
April	1st to 10th	Night	31% 9% 15% 23% 18% 4	1900
	11th to 20th	Night	37% 7% 15% 25% 15% 2	1877
	21st to end	Night	34% 8% 16% 28% 14%	1900
May	1st to 10th	Night	33% 9% 15% 26% 14% 2	2989
	11th to 20th	Night	31% 11% 18% 26% 14%	2518
	21st to end	Night	22% 8% 15% 28% 23% 3	2762
June	1st to 10th	Night	18% 8% 19% 29% 20% 5%	1520
	11th to 20th	Night	20% 6% 13% 21% 26% 14%	1520
	21st to end	Night	18% 7% 14% 23% 26% 12%	1520
July	1st to 10th	Night	24% 6% 10% 18% 20% 21%	2500
	11th to 20th	Night	22% 6% 16% 33% 16% 8%	2492
	21st to end	Night	21% 8% 17% 28% 11% 15%	2933
August	1st to 10th	Night	31% 7% 24% 20% 12% 4	2838
	11th to 20th	Night	24% 7% 26% 16% 18% 9%	3050
	21st to end	Night	28% 7% 19% 19% 23% 4	3487
September	1st to 10th	Night	23% 6% 14% 21% 27% 8%	1900
	11th to 20th	Night	22% 6% 14% 24% 24% 10%	1900
	21st to end	Night	21% 6% 11% 32% 25% 4	2125
October	1st to 10th	Night	23% 7% 14% 26% 23% 8%	2280
	11th to 20th	Night	19% 5% 11% 33% 25% 7%	2280
	21st to end	Night	27% 5% 13% 29% 22% 6%	2508
November	1st to 10th	Night	21% 6% 14% 27% 26% 6%	2388
	11th to 20th	Night	25% 6% 15% 29% 20% 5%	2470
	21st to end	Night	28% 5% 12% 27% 20% 7%	2626
December	1st to 10th	Night	31% 9% 17% 23% 15% 5%	2660
	11th to 20th	Night	33% 8% 15% 22% 21% 2	3272
	21st to end	Night	34% 10% 11% 18% 19% 8%	4873

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	20% 26% 22% 23% 9% 1	270
	11th to 20th	Day	23% 26% 29% 19% 3 1	270
	21st to end	Day	13% 33% 32% 15% 5% 1	297
February	1st to 10th	Day	24% 37% 27% 9% 1 1	270
	11th to 20th	Day	29% 32% 25% 12% 2	270
	21st to end	Day	32% 32% 23% 12%	225
March	1st to 10th	Day	23% 31% 26% 16% 3	322
	11th to 20th	Day	19% 29% 33% 15% 3 1	460
	21st to end	Day	17% 41% 31% 9% 2	506
April	1st to 10th	Day	20% 38% 29% 10% 3 1	460
	11th to 20th	Day	27% 35% 27% 10% 2	452
	21st to end	Day	18% 37% 33% 9% 3 1	460
May	1st to 10th	Day	19% 34% 29% 13% 4 1	498
	11th to 20th	Day	15% 20% 32% 22% 9% 2	675
	21st to end	Day	16% 21% 28% 23% 10% 2	734
June	1st to 10th	Day	10% 17% 28% 24% 18% 2	680
	11th to 20th	Day	12% 19% 34% 22% 11% 2	680
	21st to end	Day	8% 18% 31% 24% 17% 2	680
July	1st to 10th	Day	10% 10% 26% 28% 22% 4	671
	11th to 20th	Day	9% 9% 25% 30% 21% 6%	668
	21st to end	Day	12% 11% 28% 27% 17% 5%	582
August	1st to 10th	Day	17% 14% 30% 25% 11% 3	487
	11th to 20th	Day	11% 10% 35% 26% 14% 5%	477
	21st to end	Day	11% 12% 32% 29% 12% 4	539
September	1st to 10th	Day	14% 14% 29% 25% 12% 6%	490
	11th to 20th	Day	12% 18% 34% 23% 10% 2	490
	21st to end	Day	13% 19% 28% 22% 14% 4	329
October	1st to 10th	Day	15% 19% 26% 21% 16% 3	300
	11th to 20th	Day	16% 29% 26% 17% 10% 2	300
	21st to end	Day	21% 28% 26% 17% 7% 1	330
November	1st to 10th	Day	21% 32% 23% 16% 6% 1	270
	11th to 20th	Day	20% 29% 29% 15% 6% 2	270
	21st to end	Day	10% 30% 36% 19% 4	270
December	1st to 10th	Day	22% 29% 28% 13% 7% 1	270
	11th to 20th	Day	18% 31% 33% 14% 5%	270
	21st to end	Day	23% 31% 28% 12% 6%	297
January	1st to 10th	Night	12% 24% 29% 24% 9% 2	950
	11th to 20th	Night	15% 22% 33% 22% 7% 1	834
	21st to end	Night	7% 21% 42% 22% 7% 1	836
February	1st to 10th	Night	10% 25% 40% 19% 6%	760
	11th to 20th	Night	9% 29% 36% 23% 4	744
	21st to end	Night	11% 27% 39% 20% 2	628
March	1st to 10th	Night	9% 21% 36% 27% 6%	760
	11th to 20th	Night	5% 18% 37% 31% 8%	760
	21st to end	Night	7% 23% 42% 24% 4	746
April	1st to 10th	Night	7% 24% 39% 26% 4	570
	11th to 20th	Night	10% 23% 32% 29% 6%	563
	21st to end	Night	10% 20% 34% 28% 7% 1	570
May	1st to 10th	Night	8% 13% 41% 28% 9% 1	570
	11th to 20th	Night	8% 7% 31% 37% 15% 1	561
	21st to end	Night	7% 13% 29% 34% 16% 1	617
June	1st to 10th	Night	4 6% 27% 40% 21% 1	570
	11th to 20th	Night	5% 10% 30% 43% 11% 1	570
	21st to end	Night	3 5% 22% 42% 28% 1	570
July	1st to 10th	Night	6% 3 14% 41% 34% 2	555
	11th to 20th	Night	3 1 10% 44% 38% 4	552
	21st to end	Night	6% 2 11% 38% 41% 3	624
August	1st to 10th	Night	8% 1 12% 44% 33% 2	567
	11th to 20th	Night	5% 2 15% 45% 29% 4	564
	21st to end	Night	7% 2 14% 42% 33% 3	627
September	1st to 10th	Night	4 3 15% 49% 25% 4	570
	11th to 20th	Night	5% 4 21% 44% 23% 3	570
	21st to end	Night	6% 9% 23% 38% 21% 4	634
October	1st to 10th	Night	4 13% 31% 34% 14% 4	760
	11th to 20th	Night	8% 19% 29% 29% 13% 2	760
	21st to end	Night	9% 17% 33% 29% 10% 2	836
November	1st to 10th	Night	6% 21% 33% 30% 9% 1	904
	11th to 20th	Night	10% 25% 33% 25% 5% 2	950
	21st to end	Night	7% 19% 35% 31% 7%	950
December	1st to 10th	Night	9% 26% 38% 21% 5%	950
	11th to 20th	Night	10% 27% 33% 22% 7%	950
	21st to end	Night	14% 24% 35% 22% 4 1	1045

Page generated at 2024-10-29 09:20:50. Version ac07

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