Country View Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Country View Observatory clear sky chart from 2005-11-06 to 2025-03-12.

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 5% 4 6% 8% 43%	109240
	Night	13% 6% 2 6% 4 4 4 4 6% 8% 45%	109780
Transparency	Day	37% 6% 10% 20% 19% 7%	113060
	Night	36% 6% 10% 19% 21% 8%	114099
Seeing	Day	16% 9% 23% 24% 19% 9%	15404
	Night	15% 8% 23% 30% 21% 4	25534

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% 5% 2 4 3 3 3 2 4 5% 53%	4056
	11th to 20th	Day	13% 6% 2 4 2 2 2 2 5% 6% 55%	4060
	21st to end	Day	19% 7% 2 6% 4 3 4 3 3 6% 43%	4622
February	1st to 10th	Day	16% 6% 3 6% 4 5% 4 4 6% 6% 40%	2000
	11th to 20th	Day	21% 6% 2 6% 3 3 3 4 5% 5% 43%	1948
	21st to end	Day	17% 7% 2 6% 5% 4 4 3 5% 7% 41%	1650
March	1st to 10th	Day	22% 9% 2 6% 4 4 3 3 4 6% 36%	3403
	11th to 20th	Day	10% 5% 2 5% 3 4 4 4 5% 7% 50%	3491
	21st to end	Day	18% 6% 2 6% 4 4 4 4 5% 6% 43%	3815
April	1st to 10th	Day	12% 5% 2 6% 5% 4 4 4 5% 6% 48%	2090
	11th to 20th	Day	12% 6% 2 5% 4 3 4 3 5% 7% 49%	2221
	21st to end	Day	8% 4 2 4 4 4 4 4 5% 6% 53%	2452
May	1st to 10th	Day	9% 6% 2 6% 4 5% 4 4 6% 8% 46%	4082
	11th to 20th	Day	16% 7% 3 6% 4 5% 6% 4 5% 7% 37%	4081
	21st to end	Day	6% 4 2 5% 5% 5% 5% 4 7% 10% 48%	4476
June	1st to 10th	Day	12% 6% 2 6% 7% 6% 6% 6% 7% 10% 33%	2470
	11th to 20th	Day	5% 4 2 6% 5% 5% 6% 6% 7% 12% 42%	2470
	21st to end	Day	5% 5% 2 7% 6% 7% 7% 5% 8% 10% 38%	2470
July	1st to 10th	Day	13% 7% 3 8% 6% 7% 7% 6% 9% 11% 23%	4120
	11th to 20th	Day	6% 4 2 7% 7% 6% 8% 6% 9% 12% 32%	4120
	21st to end	Day	8% 7% 3 10% 6% 8% 9% 7% 10% 11% 20%	4466
August	1st to 10th	Day	12% 5% 2 6% 5% 6% 6% 5% 9% 13% 30%	4104
	11th to 20th	Day	6% 5% 2 5% 5% 5% 5% 4 7% 9% 48%	3830
	21st to end	Day	7% 4 2 6% 4 4 6% 4 6% 9% 48%	4098
September	1st to 10th	Day	11% 7% 3 7% 4 5% 5% 4 8% 10% 37%	2090
	11th to 20th	Day	14% 6% 2 6% 4 4 5% 4 6% 8% 40%	2090
	21st to end	Day	13% 6% 2 7% 5% 4 4 3 6% 5% 45%	2090
October	1st to 10th	Day	12% 6% 2 3 3 3 3 3 4 6% 54%	2090
	11th to 20th	Day	11% 4 1 3 2 3 3 3 5% 5% 58%	1959
	21st to end	Day	11% 4 2 4 4 3 3 3 4 5% 57%	2090
November	1st to 10th	Day	13% 6% 2 5% 3 3 4 3 3 6% 52%	1867
	11th to 20th	Day	14% 5% 2 4 3 3 3 3 4 6% 54%	1800
	21st to end	Day	14% 5% 2 6% 4 4 3 3 5% 6% 48%	1800
December	1st to 10th	Day	14% 7% 2 5% 4 3 3 3 5% 5% 49%	2930
	11th to 20th	Day	17% 7% 2 5% 3 4 3 3 4 6% 47%	3373
	21st to end	Day	22% 6% 2 6% 3 3 3 3 4 6% 43%	4466
January	1st to 10th	Night	14% 5% 2 4 3 3 3 3 5% 6% 51%	5889
	11th to 20th	Night	12% 6% 2 6% 4 4 4 4 5% 6% 48%	5900
	21st to end	Night	17% 9% 2 6% 3 3 4 3 5% 6% 42%	6329
February	1st to 10th	Night	16% 6% 3 6% 4 3 4 3 5% 6% 45%	2400
	11th to 20th	Night	20% 8% 2 5% 4 3 3 2 4 5% 44%	2338
	21st to end	Night	14% 6% 3 7% 4 4 4 4 5% 6% 44%	1980
March	1st to 10th	Night	23% 8% 3 6% 4 3 3 2 4 5% 38%	3668
	11th to 20th	Night	12% 5% 1 3 4 4 4 4 6% 8% 50%	3498
	21st to end	Night	18% 6% 2 6% 4 4 4 3 6% 6% 41%	3817
April	1st to 10th	Night	11% 5% 2 5% 4 4 3 4 5% 8% 49%	2090
	11th to 20th	Night	12% 5% 2 5% 3 3 4 3 5% 8% 50%	1923
	21st to end	Night	7% 4 1 6% 5% 3 3 4 5% 8% 55%	1725
May	1st to 10th	Night	6% 5% 2 6% 5% 5% 6% 5% 8% 10% 44%	2813
	11th to 20th	Night	15% 6% 2 6% 4 4 4 4 6% 8% 41%	2812
	21st to end	Night	7% 4 2 4 4 3 3 4 7% 10% 52%	3079
June	1st to 10th	Night	8% 6% 2 6% 5% 6% 6% 6% 8% 11% 37%	1710
	11th to 20th	Night	4 4 1 6% 5% 5% 4 5% 8% 13% 45%	1710
	21st to end	Night	6% 5% 2 5% 5% 6% 6% 5% 10% 12% 38%	1710
July	1st to 10th	Night	13% 7% 4 8% 6% 6% 6% 6% 8% 10% 27%	2840
	11th to 20th	Night	5% 4 2 7% 6% 7% 9% 8% 10% 14% 27%	2840
	21st to end	Night	10% 8% 3 8% 7% 7% 8% 6% 9% 11% 23%	3087
August	1st to 10th	Night	11% 6% 2 8% 7% 6% 6% 5% 8% 11% 28%	2825
	11th to 20th	Night	7% 4 2 6% 5% 5% 5% 4 7% 10% 45%	2995
	21st to end	Night	7% 5% 2 5% 4 3 4 4 6% 10% 50%	3526
September	1st to 10th	Night	8% 7% 3 7% 5% 6% 7% 4 7% 9% 37%	2090
	11th to 20th	Night	12% 6% 2 7% 4 5% 5% 4 6% 6% 43%	2090
	21st to end	Night	12% 4 3 6% 4 4 4 5% 6% 7% 45%	2090
October	1st to 10th	Night	12% 5% 2 5% 3 4 4 3 4 7% 52%	2090
	11th to 20th	Night	11% 4 1 3 3 3 3 3 3 6% 59%	2219
	21st to end	Night	11% 4 1 4 3 3 3 3 5% 6% 56%	2508
November	1st to 10th	Night	11% 6% 1 5% 3 3 4 2 5% 6% 53%	2427
	11th to 20th	Night	15% 5% 2 3 3 3 3 2 4 6% 54%	2600
	21st to end	Night	13% 5% 2 5% 4 4 3 3 4 6% 50%	2600
December	1st to 10th	Night	14% 6% 2 4 3 3 3 2 4 6% 54%	4250
	11th to 20th	Night	17% 5% 2 4 4 3 3 3 4 6% 49%	4822
	21st to end	Night	21% 7% 2 6% 4 4 3 3 4 5% 41%	6490

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	34% 3 4 19% 30% 9%	4057
	11th to 20th	Day	31% 2 4 18% 32% 13%	4060
	21st to end	Day	44% 3 5% 16% 22% 10%	4622
February	1st to 10th	Day	44% 4 7% 18% 19% 8%	2000
	11th to 20th	Day	43% 4 4 19% 24% 6%	1958
	21st to end	Day	44% 4 6% 15% 21% 9%	1650
March	1st to 10th	Day	49% 5% 8% 14% 17% 7%	3403
	11th to 20th	Day	33% 6% 8% 17% 24% 13%	3491
	21st to end	Day	43% 5% 7% 20% 16% 9%	3815
April	1st to 10th	Day	37% 5% 9% 20% 19% 10%	2090
	11th to 20th	Day	34% 5% 7% 20% 23% 12%	2221
	21st to end	Day	30% 6% 9% 24% 27% 5%	2452
May	1st to 10th	Day	35% 7% 11% 23% 20% 3	4120
	11th to 20th	Day	44% 7% 10% 22% 14% 1	4085
	21st to end	Day	30% 8% 14% 24% 21% 3	4489
June	1st to 10th	Day	43% 9% 14% 20% 12% 2	2470
	11th to 20th	Day	32% 9% 16% 26% 16% 1	2470
	21st to end	Day	37% 10% 18% 19% 13% 3	2470
July	1st to 10th	Day	49% 12% 19% 14% 4 2	4055
	11th to 20th	Day	39% 14% 20% 22% 4 1	4051
	21st to end	Day	51% 16% 16% 13% 4	4324
August	1st to 10th	Day	41% 11% 17% 27% 4	4091
	11th to 20th	Day	30% 8% 16% 30% 14% 1	3869
	21st to end	Day	31% 8% 15% 28% 15% 2	4098
September	1st to 10th	Day	41% 8% 15% 16% 16% 4	2090
	11th to 20th	Day	41% 7% 10% 19% 19% 4	2090
	21st to end	Day	40% 5% 8% 21% 20% 6%	2090
October	1st to 10th	Day	29% 3 6% 14% 34% 13%	3480
	11th to 20th	Day	17% 2 5% 17% 28% 31%	3238
	21st to end	Day	23% 3 4 19% 36% 15%	3428
November	1st to 10th	Day	35% 4 7% 14% 27% 13%	1867
	11th to 20th	Day	32% 3 6% 20% 27% 13%	1800
	21st to end	Day	37% 4 8% 17% 26% 9%	1800
December	1st to 10th	Day	37% 4 5% 17% 26% 10%	2930
	11th to 20th	Day	40% 2 8% 21% 22% 7%	3370
	21st to end	Day	43% 3 7% 21% 23% 3	4466
January	1st to 10th	Night	33% 4 4 20% 30% 9%	5889
	11th to 20th	Night	37% 3 5% 20% 26% 9%	5900
	21st to end	Night	44% 3 4 15% 27% 7%	6329
February	1st to 10th	Night	41% 3 6% 18% 22% 10%	2400
	11th to 20th	Night	44% 3 5% 16% 22% 10%	2339
	21st to end	Night	41% 4 6% 16% 18% 14%	1980
March	1st to 10th	Night	49% 5% 9% 15% 14% 9%	3668
	11th to 20th	Night	32% 5% 10% 13% 26% 13%	3498
	21st to end	Night	42% 4 6% 19% 18% 11%	3817
April	1st to 10th	Night	34% 4 9% 21% 20% 12%	2090
	11th to 20th	Night	33% 3 6% 23% 24% 11%	1923
	21st to end	Night	28% 5% 12% 24% 24% 8%	1725
May	1st to 10th	Night	30% 11% 14% 24% 17% 4	2840
	11th to 20th	Night	40% 7% 13% 24% 14% 2	2813
	21st to end	Night	26% 8% 13% 28% 22% 4	3087
June	1st to 10th	Night	37% 11% 17% 20% 14% 1	1710
	11th to 20th	Night	28% 9% 19% 28% 13% 2	1710
	21st to end	Night	34% 10% 23% 18% 12% 4	1710
July	1st to 10th	Night	50% 13% 19% 13% 4 2	2795
	11th to 20th	Night	39% 16% 24% 15% 6% 1	2786
	21st to end	Night	50% 16% 17% 12% 4 1	2988
August	1st to 10th	Night	45% 10% 20% 21% 4	2814
	11th to 20th	Night	32% 10% 18% 26% 13% 2	3022
	21st to end	Night	29% 7% 17% 29% 16% 2	3526
September	1st to 10th	Night	41% 10% 15% 15% 15% 4	2090
	11th to 20th	Night	40% 9% 10% 17% 18% 5%	2090
	21st to end	Night	38% 6% 9% 17% 22% 8%	2090
October	1st to 10th	Night	33% 6% 6% 12% 30% 13%	3480
	11th to 20th	Night	17% 2 4 14% 30% 32%	3679
	21st to end	Night	20% 4 4 20% 33% 20%	4120
November	1st to 10th	Night	33% 4 8% 14% 27% 14%	2427
	11th to 20th	Night	33% 2 5% 17% 28% 14%	2600
	21st to end	Night	37% 4 7% 18% 25% 10%	2600
December	1st to 10th	Night	34% 4 5% 20% 30% 8%	4250
	11th to 20th	Night	37% 4 10% 18% 23% 7%	4824
	21st to end	Night	45% 3 4 22% 22% 3	6490

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	25% 18% 43% 13% 1	300
	11th to 20th	Day	22% 24% 32% 14% 6% 1	300
	21st to end	Day	26% 26% 34% 10% 3	330
February	1st to 10th	Day	25% 17% 38% 17% 4	300
	11th to 20th	Day	36% 17% 32% 14% 2	300
	21st to end	Day	26% 18% 40% 13% 3	249
March	1st to 10th	Day	25% 19% 27% 22% 5% 1	405
	11th to 20th	Day	20% 15% 35% 20% 9% 1	464
	21st to end	Day	19% 16% 36% 19% 9%	506
April	1st to 10th	Day	21% 16% 27% 24% 11%	460
	11th to 20th	Day	15% 14% 29% 24% 15% 3	452
	21st to end	Day	13% 10% 26% 30% 18% 2	460
May	1st to 10th	Day	12% 11% 25% 28% 16% 7%	463
	11th to 20th	Day	14% 5% 23% 28% 20% 10%	487
	21st to end	Day	11% 5% 19% 29% 21% 15%	529
June	1st to 10th	Day	12% 3 17% 27% 29% 12%	490
	11th to 20th	Day	7% 3 19% 24% 27% 20%	490
	21st to end	Day	7% 3 16% 31% 27% 18%	490
July	1st to 10th	Day	8% 2 10% 23% 34% 23%	485
	11th to 20th	Day	7% 1 7% 21% 37% 27%	484
	21st to end	Day	5% 2 8% 28% 37% 21%	532
August	1st to 10th	Day	12% 3 14% 23% 29% 18%	486
	11th to 20th	Day	9% 2 9% 25% 35% 19%	479
	21st to end	Day	14% 1 8% 28% 33% 15%	539
September	1st to 10th	Day	11% 3 15% 26% 32% 14%	490
	11th to 20th	Day	16% 3 14% 26% 30% 11%	490
	21st to end	Day	13% 4 18% 28% 26% 11%	490
October	1st to 10th	Day	16% 7% 24% 24% 20% 8%	490
	11th to 20th	Day	12% 8% 23% 33% 18% 6%	490
	21st to end	Day	13% 8% 24% 30% 19% 5%	539
November	1st to 10th	Day	20% 8% 27% 26% 16% 3	405
	11th to 20th	Day	19% 14% 39% 20% 6% 2	300
	21st to end	Day	18% 12% 34% 25% 11% 1	300
December	1st to 10th	Day	27% 17% 31% 18% 6% 1	300
	11th to 20th	Day	26% 13% 34% 17% 8% 1	300
	21st to end	Day	32% 13% 33% 15% 5% 1	330
January	1st to 10th	Night	23% 18% 33% 21% 6%	800
	11th to 20th	Night	21% 15% 30% 26% 9%	800
	21st to end	Night	22% 16% 34% 25% 3	880
February	1st to 10th	Night	20% 11% 32% 31% 7%	800
	11th to 20th	Night	24% 17% 30% 26% 3	783
	21st to end	Night	20% 15% 34% 28% 3	660
March	1st to 10th	Night	17% 13% 34% 30% 6%	800
	11th to 20th	Night	18% 14% 31% 28% 10% 1	767
	21st to end	Night	18% 13% 31% 28% 10% 1	836
April	1st to 10th	Night	14% 14% 30% 28% 13%	760
	11th to 20th	Night	15% 12% 26% 31% 16% 1	611
	21st to end	Night	8% 7% 25% 39% 19% 1	570
May	1st to 10th	Night	8% 7% 25% 36% 22% 2	570
	11th to 20th	Night	11% 3 21% 36% 24% 5%	561
	21st to end	Night	12% 1 16% 34% 32% 5%	617
June	1st to 10th	Night	10% 1 13% 39% 32% 5%	570
	11th to 20th	Night	4 2 14% 32% 36% 12%	570
	21st to end	Night	7% 1 8% 35% 39% 10%	570
July	1st to 10th	Night	8% 1 8% 27% 39% 16%	555
	11th to 20th	Night	8% 7% 21% 47% 16%	552
	21st to end	Night	6% 1 9% 28% 45% 11%	624
August	1st to 10th	Night	9% 1 9% 29% 41% 12%	567
	11th to 20th	Night	10% 1 9% 30% 42% 9%	564
	21st to end	Night	15% 1 9% 25% 39% 10%	651
September	1st to 10th	Night	9% 2 15% 26% 38% 10%	760
	11th to 20th	Night	14% 2 12% 28% 38% 6%	760
	21st to end	Night	14% 3 17% 29% 34% 4	760
October	1st to 10th	Night	13% 4 20% 33% 25% 5%	760
	11th to 20th	Night	12% 6% 21% 33% 23% 3	760
	21st to end	Night	13% 8% 23% 31% 23% 2	836
November	1st to 10th	Night	15% 6% 22% 34% 21% 1	780
	11th to 20th	Night	16% 11% 26% 31% 15% 2	800
	21st to end	Night	15% 11% 27% 33% 14% 1	800
December	1st to 10th	Night	18% 13% 30% 27% 11% 1	800
	11th to 20th	Night	21% 10% 29% 30% 10%	800
	21st to end	Night	27% 12% 24% 29% 8%	880

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