Harold A Campbell Public Use Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Harold A Campbell Public Use Area clear sky chart from 2005-11-06 to 2024-11-25.

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	7% 6% 3 8% 7% 7% 7% 5% 8% 10% 34%	100833
	Night	7% 5% 2 7% 5% 5% 5% 5% 7% 10% 42%	98577
Transparency	Day	44% 6% 16% 20% 11% 3	104556
	Night	37% 6% 19% 22% 12% 3	102993
Seeing	Day	7% 4 15% 26% 26% 23%	16001
	Night	8% 3 14% 33% 31% 12%	26107

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	9% 7% 3 7% 5% 5% 5% 4 6% 8% 40%	2836
	11th to 20th	Day	16% 7% 3 8% 7% 6% 6% 4 6% 9% 28%	2840
	21st to end	Day	6% 7% 3 9% 6% 6% 5% 5% 5% 8% 40%	3202
February	1st to 10th	Day	8% 7% 2 6% 6% 5% 6% 4 7% 9% 41%	1900
	11th to 20th	Day	7% 4 1 5% 4 4 5% 3 6% 9% 52%	1928
	21st to end	Day	5% 5% 2 7% 6% 5% 6% 4 5% 8% 48%	1727
March	1st to 10th	Day	6% 5% 2 9% 6% 7% 8% 5% 9% 10% 32%	3435
	11th to 20th	Day	4 3 1 5% 4 4 5% 4 7% 10% 52%	3480
	21st to end	Day	10% 4 2 5% 4 4 5% 5% 6% 8% 47%	3815
April	1st to 10th	Day	4 3 2 5% 6% 6% 6% 6% 8% 9% 45%	2090
	11th to 20th	Day	7% 4 2 6% 6% 5% 6% 5% 6% 9% 42%	2135
	21st to end	Day	6% 4 2 7% 5% 5% 5% 4 7% 9% 45%	2280
May	1st to 10th	Day	3 2 1 4 5% 5% 6% 5% 6% 8% 55%	3765
	11th to 20th	Day	7% 5% 2 6% 6% 6% 6% 6% 8% 10% 39%	3907
	21st to end	Day	6% 5% 2 6% 5% 5% 6% 5% 6% 8% 45%	4476
June	1st to 10th	Day	13% 10% 5% 12% 8% 8% 7% 5% 7% 7% 17%	2470
	11th to 20th	Day	9% 8% 4 10% 8% 8% 8% 6% 9% 10% 20%	2470
	21st to end	Day	9% 7% 4 11% 9% 9% 9% 5% 8% 8% 20%	2470
July	1st to 10th	Day	6% 8% 3 10% 8% 9% 8% 6% 8% 11% 24%	4120
	11th to 20th	Day	7% 7% 3 11% 9% 8% 8% 6% 10% 11% 20%	4120
	21st to end	Day	4 6% 3 9% 9% 8% 9% 6% 9% 12% 24%	4466
August	1st to 10th	Day	5% 6% 4 11% 9% 9% 10% 6% 10% 12% 20%	4083
	11th to 20th	Day	5% 5% 3 9% 8% 9% 9% 8% 10% 13% 23%	3714
	21st to end	Day	6% 5% 2 9% 8% 8% 9% 7% 12% 13% 19%	3828
September	1st to 10th	Day	8% 7% 4 11% 8% 9% 9% 6% 9% 10% 18%	2090
	11th to 20th	Day	8% 8% 4 11% 9% 8% 8% 6% 7% 9% 22%	2090
	21st to end	Day	11% 9% 3 11% 8% 8% 9% 6% 7% 9% 20%	2090
October	1st to 10th	Day	9% 7% 3 11% 7% 8% 6% 6% 7% 11% 25%	2019
	11th to 20th	Day	8% 6% 3 9% 7% 7% 7% 7% 8% 8% 30%	1900
	21st to end	Day	10% 5% 3 8% 5% 5% 5% 5% 7% 9% 37%	2090
November	1st to 10th	Day	6% 5% 2 7% 5% 7% 7% 5% 7% 8% 41%	1957
	11th to 20th	Day	10% 7% 2 7% 6% 6% 6% 5% 6% 9% 36%	2000
	21st to end	Day	6% 5% 3 7% 5% 5% 6% 5% 7% 9% 42%	1940
December	1st to 10th	Day	7% 6% 3 7% 6% 4 5% 4 6% 8% 43%	1823
	11th to 20th	Day	8% 6% 2 7% 6% 5% 6% 5% 6% 8% 43%	2153
	21st to end	Day	10% 6% 3 8% 6% 6% 6% 6% 8% 10% 32%	3124
January	1st to 10th	Night	8% 8% 2 7% 5% 5% 5% 5% 6% 9% 39%	4109
	11th to 20th	Night	15% 11% 4 9% 5% 5% 4 4 6% 8% 28%	4120
	21st to end	Night	7% 7% 3 9% 6% 5% 6% 5% 6% 8% 40%	4436
February	1st to 10th	Night	8% 6% 2 5% 5% 4 5% 4 7% 8% 46%	2280
	11th to 20th	Night	7% 3 2 3 4 3 4 5% 6% 8% 56%	2136
	21st to end	Night	4 3 1 4 4 4 4 4 6% 8% 59%	1727
March	1st to 10th	Night	7% 7% 3 9% 5% 6% 5% 5% 6% 8% 40%	3418
	11th to 20th	Night	5% 3 1 4 3 4 4 3 7% 11% 55%	3480
	21st to end	Night	7% 4 2 5% 4 4 5% 4 6% 7% 54%	3817
April	1st to 10th	Night	5% 3 1 4 3 3 3 4 7% 10% 57%	2090
	11th to 20th	Night	6% 3 2 5% 4 5% 4 5% 7% 9% 52%	1992
	21st to end	Night	6% 3 2 4 4 4 4 5% 6% 9% 55%	1900
May	1st to 10th	Night	3 3 1 4 3 3 4 4 6% 9% 61%	3130
	11th to 20th	Night	5% 4 2 5% 4 4 5% 4 7% 10% 50%	3013
	21st to end	Night	5% 5% 2 6% 5% 4 5% 4 7% 11% 48%	3079
June	1st to 10th	Night	12% 7% 2 7% 7% 6% 7% 7% 9% 9% 25%	1710
	11th to 20th	Night	7% 8% 2 6% 7% 6% 6% 6% 9% 11% 32%	1710
	21st to end	Night	7% 6% 3 8% 5% 7% 7% 5% 10% 11% 32%	1710
July	1st to 10th	Night	5% 6% 2 8% 6% 6% 6% 5% 9% 12% 36%	2840
	11th to 20th	Night	4 6% 3 7% 5% 6% 7% 7% 10% 12% 34%	2840
	21st to end	Night	3 4 3 7% 6% 6% 6% 6% 9% 12% 37%	3087
August	1st to 10th	Night	4 4 3 8% 6% 6% 6% 6% 8% 13% 37%	2825
	11th to 20th	Night	4 5% 3 7% 6% 6% 7% 6% 10% 15% 31%	3084
	21st to end	Night	4 5% 2 7% 6% 7% 8% 7% 12% 16% 26%	3824
September	1st to 10th	Night	7% 4 2 7% 7% 7% 8% 6% 11% 13% 28%	2090
	11th to 20th	Night	7% 7% 3 9% 6% 6% 7% 6% 9% 10% 29%	2090
	21st to end	Night	9% 6% 2 10% 7% 7% 7% 6% 8% 11% 26%	2090
October	1st to 10th	Night	9% 6% 3 9% 5% 7% 6% 4 7% 9% 34%	2160
	11th to 20th	Night	8% 5% 2 6% 4 4 5% 4 7% 10% 43%	2280
	21st to end	Night	9% 5% 2 7% 6% 4 4 4 6% 9% 44%	2508
November	1st to 10th	Night	8% 4 2 5% 5% 4 4 4 5% 9% 50%	2341
	11th to 20th	Night	8% 6% 2 6% 5% 5% 6% 5% 6% 9% 42%	2400
	21st to end	Night	8% 6% 2 6% 4 5% 4 4 6% 8% 48%	2335
December	1st to 10th	Night	5% 5% 2 5% 5% 5% 5% 4 6% 8% 51%	2352
	11th to 20th	Night	11% 5% 1 5% 4 4 4 3 6% 8% 49%	3042
	21st to end	Night	9% 8% 3 8% 6% 5% 5% 5% 7% 8% 36%	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	43% 2 9% 23% 19% 5%	2837
	11th to 20th	Day	53% 3 12% 17% 11% 3	2840
	21st to end	Day	45% 2 7% 22% 17% 6%	3202
February	1st to 10th	Day	39% 4 8% 26% 18% 6%	1900
	11th to 20th	Day	29% 3 8% 28% 23% 9%	1938
	21st to end	Day	34% 4 8% 18% 25% 10%	1727
March	1st to 10th	Day	45% 3 14% 21% 14% 3	3435
	11th to 20th	Day	28% 2 16% 38% 13% 3	3480
	21st to end	Day	36% 2 7% 29% 19% 8%	3815
April	1st to 10th	Day	32% 4 14% 29% 17% 4	2090
	11th to 20th	Day	37% 4 14% 23% 18% 3	2135
	21st to end	Day	36% 4 9% 25% 22% 5%	2280
May	1st to 10th	Day	27% 2 8% 34% 25% 5%	3800
	11th to 20th	Day	40% 2 18% 32% 8%	3911
	21st to end	Day	37% 3 12% 32% 16%	4489
June	1st to 10th	Day	65% 5% 15% 12% 4	2470
	11th to 20th	Day	57% 8% 19% 14% 2	2470
	21st to end	Day	59% 9% 22% 10% 1	2470
July	1st to 10th	Day	50% 11% 24% 14% 1	4055
	11th to 20th	Day	52% 12% 27% 9%	4051
	21st to end	Day	44% 15% 29% 12% 1	4324
August	1st to 10th	Day	52% 12% 26% 10% 1	4070
	11th to 20th	Day	44% 14% 28% 13% 1	3750
	21st to end	Day	48% 15% 30% 7% 1	3828
September	1st to 10th	Day	56% 11% 21% 12%	2090
	11th to 20th	Day	57% 9% 20% 11% 3	2090
	21st to end	Day	59% 8% 16% 12% 5% 1	2090
October	1st to 10th	Day	53% 9% 15% 14% 7% 2	3357
	11th to 20th	Day	45% 7% 15% 19% 13% 2	3140
	21st to end	Day	38% 6% 10% 24% 19% 4	3428
November	1st to 10th	Day	39% 5% 10% 17% 20% 8%	1957
	11th to 20th	Day	44% 5% 7% 21% 17% 7%	2000
	21st to end	Day	38% 5% 11% 19% 22% 5%	1940
December	1st to 10th	Day	39% 3 11% 24% 20% 3	1823
	11th to 20th	Day	40% 3 9% 19% 21% 8%	2150
	21st to end	Day	46% 3 13% 19% 16% 3	3124
January	1st to 10th	Night	42% 2 12% 24% 16% 3	4109
	11th to 20th	Night	55% 3 13% 18% 9% 2	4120
	21st to end	Night	43% 3 9% 23% 16% 6%	4436
February	1st to 10th	Night	34% 4 12% 26% 19% 5%	2280
	11th to 20th	Night	26% 2 9% 30% 24% 8%	2137
	21st to end	Night	24% 3 11% 24% 30% 8%	1727
March	1st to 10th	Night	43% 3 12% 23% 14% 4	3418
	11th to 20th	Night	24% 3 24% 33% 13% 3	3480
	21st to end	Night	30% 2 11% 26% 26% 5%	3817
April	1st to 10th	Night	22% 3 18% 36% 16% 4	2090
	11th to 20th	Night	28% 5% 17% 25% 22% 4	1992
	21st to end	Night	27% 3 14% 29% 22% 4	1900
May	1st to 10th	Night	20% 3 17% 42% 15% 3	3160
	11th to 20th	Night	29% 3 22% 34% 11%	3014
	21st to end	Night	32% 3 16% 38% 11%	3087
June	1st to 10th	Night	50% 8% 23% 16% 3	1710
	11th to 20th	Night	42% 10% 27% 19% 2	1710
	21st to end	Night	43% 13% 30% 13% 2	1710
July	1st to 10th	Night	36% 13% 32% 18%	2795
	11th to 20th	Night	38% 13% 39% 10% 1	2786
	21st to end	Night	34% 13% 36% 16% 1	2988
August	1st to 10th	Night	36% 12% 32% 17% 2	2814
	11th to 20th	Night	36% 14% 34% 16%	3114
	21st to end	Night	39% 16% 37% 8% 1	3824
September	1st to 10th	Night	42% 15% 28% 13% 1	2090
	11th to 20th	Night	47% 12% 26% 13% 2	2090
	21st to end	Night	50% 11% 19% 14% 6%	2090
October	1st to 10th	Night	52% 10% 17% 14% 6% 1	3602
	11th to 20th	Night	39% 7% 18% 19% 16% 1	3779
	21st to end	Night	36% 5% 10% 28% 17% 4	4120
November	1st to 10th	Night	33% 4 13% 21% 21% 8%	2341
	11th to 20th	Night	38% 5% 9% 25% 17% 6%	2400
	21st to end	Night	35% 4 12% 21% 23% 6%	2335
December	1st to 10th	Night	31% 5% 12% 29% 19% 4	2352
	11th to 20th	Night	34% 3 10% 22% 22% 9%	3044
	21st to end	Night	46% 3 14% 19% 16% 3	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	10% 7% 32% 35% 14% 3	270
	11th to 20th	Day	14% 8% 27% 33% 14% 4	270
	21st to end	Day	10% 11% 38% 31% 8% 2	297
February	1st to 10th	Day	7% 8% 27% 37% 16% 5%	270
	11th to 20th	Day	7% 4 26% 33% 22% 7%	350
	21st to end	Day	4 7% 19% 36% 29% 4	382
March	1st to 10th	Day	5% 6% 26% 39% 22% 2	460
	11th to 20th	Day	7% 6% 24% 35% 25% 4	460
	21st to end	Day	4 4 24% 33% 28% 7%	506
April	1st to 10th	Day	3 5% 27% 35% 23% 7%	460
	11th to 20th	Day	9% 5% 25% 31% 22% 9%	452
	21st to end	Day	5% 5% 18% 33% 28% 10%	460
May	1st to 10th	Day	3 1 16% 29% 34% 16%	463
	11th to 20th	Day	10% 4 15% 28% 27% 17%	487
	21st to end	Day	9% 4 7% 22% 29% 31%	529
June	1st to 10th	Day	13% 5% 8% 20% 28% 27%	490
	11th to 20th	Day	9% 3 6% 21% 25% 36%	490
	21st to end	Day	6% 2 3 12% 27% 51%	490
July	1st to 10th	Day	4 3 2 9% 24% 58%	485
	11th to 20th	Day	6% 2 3 12% 29% 49%	484
	21st to end	Day	6% 1 3 13% 25% 53%	532
August	1st to 10th	Day	6% 2 4 13% 26% 50%	486
	11th to 20th	Day	5% 2 3 9% 30% 51%	479
	21st to end	Day	8% 2 4 21% 26% 39%	539
September	1st to 10th	Day	9% 2 3 12% 28% 46%	490
	11th to 20th	Day	6% 4 6% 14% 26% 44%	490
	21st to end	Day	10% 2 6% 19% 28% 35%	490
October	1st to 10th	Day	9% 3 11% 29% 33% 14%	490
	11th to 20th	Day	9% 4 13% 32% 28% 13%	490
	21st to end	Day	8% 5% 19% 30% 28% 10%	539
November	1st to 10th	Day	9% 4 17% 34% 27% 9%	495
	11th to 20th	Day	10% 4 19% 36% 23% 7%	500
	21st to end	Day	4 3 23% 35% 28% 7%	476
December	1st to 10th	Day	7% 6% 19% 37% 25% 6%	383
	11th to 20th	Day	7% 6% 24% 36% 21% 6%	270
	21st to end	Day	6% 9% 24% 34% 19% 8%	297
January	1st to 10th	Night	9% 6% 20% 40% 23% 1	760
	11th to 20th	Night	9% 4 25% 41% 19% 1	760
	21st to end	Night	7% 6% 29% 43% 15%	836
February	1st to 10th	Night	10% 5% 23% 44% 18% 1	760
	11th to 20th	Night	8% 3 25% 43% 20% 1	743
	21st to end	Night	5% 2 23% 49% 20% 1	628
March	1st to 10th	Night	4 3 29% 45% 17% 1	760
	11th to 20th	Night	6% 4 23% 46% 19% 2	760
	21st to end	Night	6% 4 22% 46% 21% 1	836
April	1st to 10th	Night	5% 4 19% 49% 22% 1	760
	11th to 20th	Night	5% 4 19% 48% 22% 1	751
	21st to end	Night	7% 3 19% 49% 21% 2	760
May	1st to 10th	Night	3 1 14% 45% 33% 3	760
	11th to 20th	Night	9% 2 13% 42% 30% 4	684
	21st to end	Night	7% 2 4 29% 47% 11%	617
June	1st to 10th	Night	12% 2 4 23% 46% 14%	570
	11th to 20th	Night	7% 3 2 13% 48% 28%	570
	21st to end	Night	6% 1 1 8% 44% 39%	570
July	1st to 10th	Night	7% 1 2 7% 45% 39%	555
	11th to 20th	Night	5% 1 1 8% 42% 43%	552
	21st to end	Night	4 1 1 7% 43% 44%	624
August	1st to 10th	Night	6% 1 1 9% 46% 37%	567
	11th to 20th	Night	6% 2 1 10% 42% 39%	737
	21st to end	Night	8% 2 4 18% 39% 28%	836
September	1st to 10th	Night	9% 1 4 13% 43% 31%	760
	11th to 20th	Night	9% 4 4 15% 40% 29%	760
	21st to end	Night	11% 2 6% 18% 42% 21%	760
October	1st to 10th	Night	11% 4 5% 33% 38% 9%	760
	11th to 20th	Night	10% 3 8% 34% 38% 8%	760
	21st to end	Night	11% 2 14% 39% 29% 6%	836
November	1st to 10th	Night	8% 3 17% 38% 30% 3	780
	11th to 20th	Night	9% 3 16% 40% 28% 4	800
	21st to end	Night	9% 3 16% 45% 25% 1	779
December	1st to 10th	Night	7% 2 15% 43% 31% 3	760
	11th to 20th	Night	10% 3 16% 41% 27% 4	760
	21st to end	Night	7% 5% 18% 41% 27% 3	836

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