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 2026-07-16.

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	12% 6% 2 6% 4 5% 5% 4 6% 8% 42%	137889
	Night	13% 6% 2 6% 4 4 4 4 6% 8% 44%	134776
Transparency	Day	38% 7% 11% 19% 18% 7%	141665
	Night	37% 6% 10% 19% 20% 8%	139072
Seeing	Day	16% 9% 23% 24% 19% 8%	17248
	Night	15% 8% 23% 30% 21% 4	27262

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	15% 6% 2 6% 4 4 4 3 4 6% 47%	5258
	11th to 20th	Day	12% 6% 2 4 2 2 2 2 4 6% 58%	5280
	21st to end	Day	19% 8% 3 7% 5% 3 4 3 4 5% 39%	5978
February	1st to 10th	Day	16% 6% 3 6% 4 4 4 4 6% 6% 41%	2100
	11th to 20th	Day	20% 6% 2 6% 3 3 3 3 5% 5% 43%	2048
	21st to end	Day	17% 7% 2 5% 5% 4 4 3 5% 7% 41%	1730
March	1st to 10th	Day	20% 8% 2 7% 4 4 4 3 5% 6% 38%	4833
	11th to 20th	Day	8% 4 2 5% 3 4 4 4 5% 6% 54%	5090
	21st to end	Day	16% 6% 3 6% 4 4 3 3 4 5% 46%	5586
April	1st to 10th	Day	12% 5% 2 6% 5% 4 4 4 5% 6% 48%	2310
	11th to 20th	Day	11% 6% 2 5% 4 3 4 3 5% 7% 51%	2457
	21st to end	Day	8% 5% 2 5% 4 4 5% 4 5% 6% 51%	2710
May	1st to 10th	Day	14% 7% 2 7% 5% 5% 4 4 6% 8% 38%	7616
	11th to 20th	Day	14% 6% 2 6% 4 5% 6% 4 6% 9% 36%	7626
	21st to end	Day	12% 7% 3 7% 6% 5% 5% 4 7% 8% 35%	8391
June	1st to 10th	Day	11% 6% 2 6% 6% 6% 6% 6% 7% 10% 34%	2730
	11th to 20th	Day	6% 4 2 6% 5% 5% 6% 5% 8% 12% 40%	2730
	21st to end	Day	5% 5% 2 6% 5% 7% 6% 5% 8% 10% 39%	2730
July	1st to 10th	Day	10% 6% 2 8% 6% 7% 7% 6% 9% 11% 27%	6030
	11th to 20th	Day	4 4 2 6% 6% 6% 7% 6% 9% 13% 36%	5965
	21st to end	Day	7% 6% 3 9% 6% 7% 8% 7% 10% 12% 25%	6424
August	1st to 10th	Day	13% 6% 2 6% 5% 6% 6% 5% 9% 12% 29%	4234
	11th to 20th	Day	6% 5% 2 5% 5% 5% 5% 4 7% 10% 47%	3953
	21st to end	Day	8% 4 2 6% 4 4 6% 4 6% 9% 48%	4228
September	1st to 10th	Day	10% 7% 3 7% 4 5% 5% 4 8% 10% 38%	2200
	11th to 20th	Day	13% 6% 2 6% 4 4 5% 4 6% 8% 41%	2200
	21st to end	Day	13% 6% 2 7% 5% 5% 4 3 5% 6% 45%	2200
October	1st to 10th	Day	12% 6% 2 4 3 3 3 3 4 6% 53%	2200
	11th to 20th	Day	11% 4 1 3 2 3 3 3 5% 5% 59%	2062
	21st to end	Day	11% 5% 2 4 4 3 3 3 4 5% 57%	2200
November	1st to 10th	Day	12% 6% 2 5% 3 3 4 3 3 5% 53%	1962
	11th to 20th	Day	13% 4 1 4 3 3 2 3 4 6% 56%	1890
	21st to end	Day	14% 5% 2 6% 4 4 3 4 5% 6% 48%	1890
December	1st to 10th	Day	14% 7% 2 5% 4 3 3 3 4 6% 48%	3020
	11th to 20th	Day	17% 7% 2 5% 3 4 3 2 4 6% 48%	3463
	21st to end	Day	22% 6% 2 6% 3 3 3 3 4 6% 44%	4565
January	1st to 10th	Night	13% 6% 2 5% 4 4 4 3 6% 7% 46%	7635
	11th to 20th	Night	13% 6% 2 6% 4 4 4 3 5% 5% 50%	7680
	21st to end	Night	19% 10% 3 6% 4 3 4 3 4 5% 39%	8184
February	1st to 10th	Night	15% 6% 3 6% 4 3 3 3 4 6% 46%	2520
	11th to 20th	Night	19% 8% 2 5% 4 3 3 2 4 5% 43%	2458
	21st to end	Night	15% 6% 3 7% 4 4 4 4 5% 6% 43%	2076
March	1st to 10th	Night	20% 7% 2 6% 4 3 4 3 5% 6% 39%	5225
	11th to 20th	Night	10% 5% 1 3 3 3 4 4 6% 8% 52%	5090
	21st to end	Night	15% 5% 2 5% 4 4 4 3 6% 6% 47%	5588
April	1st to 10th	Night	11% 5% 2 5% 4 4 4 4 5% 8% 48%	2310
	11th to 20th	Night	11% 4 1 5% 3 3 4 3 5% 8% 53%	2128
	21st to end	Night	7% 4 2 6% 5% 4 4 4 5% 8% 53%	1907
May	1st to 10th	Night	13% 6% 2 6% 5% 5% 5% 4 7% 10% 38%	5237
	11th to 20th	Night	14% 6% 2 6% 4 5% 5% 4 7% 9% 39%	5234
	21st to end	Night	13% 7% 3 6% 5% 4 4 4 6% 10% 37%	5761
June	1st to 10th	Night	8% 6% 2 6% 5% 6% 6% 5% 8% 11% 37%	1890
	11th to 20th	Night	5% 5% 1 6% 5% 5% 4 4 8% 13% 44%	1890
	21st to end	Night	5% 5% 2 5% 5% 6% 6% 5% 10% 12% 39%	1890
July	1st to 10th	Night	11% 7% 3 9% 6% 6% 7% 6% 8% 10% 27%	4148
	11th to 20th	Night	5% 4 2 7% 5% 7% 8% 7% 10% 14% 32%	4102
	21st to end	Night	9% 7% 3 8% 6% 6% 7% 5% 8% 11% 28%	4427
August	1st to 10th	Night	12% 6% 2 8% 7% 6% 6% 5% 8% 11% 28%	2915
	11th to 20th	Night	7% 5% 2 6% 5% 5% 5% 4 7% 10% 45%	3091
	21st to end	Night	8% 5% 2 5% 4 3 5% 4 6% 9% 50%	3637
September	1st to 10th	Night	8% 7% 3 7% 5% 6% 7% 4 7% 9% 37%	2200
	11th to 20th	Night	11% 6% 2 7% 4 5% 5% 4 6% 6% 44%	2200
	21st to end	Night	12% 5% 3 6% 4 4 5% 5% 6% 7% 45%	2200
October	1st to 10th	Night	11% 6% 2 5% 4 4 4 3 4 7% 51%	2200
	11th to 20th	Night	10% 4 1 3 3 3 3 3 3 6% 60%	2336
	21st to end	Night	12% 5% 1 4 3 3 3 3 4 6% 56%	2640
November	1st to 10th	Night	11% 6% 1 4 3 3 4 2 5% 6% 54%	2552
	11th to 20th	Night	14% 5% 2 3 3 3 3 2 4 6% 55%	2730
	21st to end	Night	13% 5% 2 5% 5% 4 3 3 4 6% 50%	2730
December	1st to 10th	Night	14% 6% 2 4 3 3 3 3 4 6% 53%	4380
	11th to 20th	Night	16% 5% 2 4 4 3 3 3 4 6% 49%	4952
	21st to end	Night	20% 7% 2 6% 4 4 3 3 4 5% 42%	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	38% 4 7% 20% 24% 7%	5259
	11th to 20th	Day	29% 2 4 17% 32% 16%	5280
	21st to end	Day	48% 3 5% 15% 20% 10%	5978
February	1st to 10th	Day	43% 4 7% 18% 20% 8%	2100
	11th to 20th	Day	43% 4 4 20% 23% 6%	2058
	21st to end	Day	44% 4 6% 15% 21% 10%	1730
March	1st to 10th	Day	47% 5% 7% 12% 23% 7%	4833
	11th to 20th	Day	29% 5% 7% 15% 22% 22%	5090
	21st to end	Day	41% 4 6% 20% 18% 11%	5586
April	1st to 10th	Day	37% 5% 9% 21% 19% 9%	2310
	11th to 20th	Day	32% 5% 7% 20% 24% 11%	2457
	21st to end	Day	31% 6% 10% 23% 26% 4	2710
May	1st to 10th	Day	42% 7% 14% 19% 16% 2	7651
	11th to 20th	Day	41% 9% 16% 20% 11% 3	7630
	21st to end	Day	44% 10% 12% 16% 16% 2	8405
June	1st to 10th	Day	43% 8% 14% 19% 13% 2	2730
	11th to 20th	Day	34% 9% 17% 24% 15% 1	2730
	21st to end	Day	36% 10% 18% 20% 13% 3	2730
July	1st to 10th	Day	44% 13% 20% 18% 4 1	5965
	11th to 20th	Day	33% 15% 28% 21% 3 1	5896
	21st to end	Day	45% 15% 18% 18% 3	6240
August	1st to 10th	Day	42% 11% 17% 27% 4	4221
	11th to 20th	Day	30% 8% 16% 30% 13% 1	3992
	21st to end	Day	32% 8% 15% 28% 15% 2	4228
September	1st to 10th	Day	40% 7% 15% 18% 16% 4	2200
	11th to 20th	Day	40% 7% 10% 21% 19% 4	2200
	21st to end	Day	40% 5% 9% 21% 20% 6%	2200
October	1st to 10th	Day	29% 3 6% 14% 34% 13%	3590
	11th to 20th	Day	17% 2 5% 17% 29% 31%	3341
	21st to end	Day	23% 3 4 19% 36% 15%	3538
November	1st to 10th	Day	34% 4 7% 14% 28% 13%	1962
	11th to 20th	Day	31% 3 6% 20% 27% 13%	1890
	21st to end	Day	37% 4 8% 17% 26% 8%	1890
December	1st to 10th	Day	38% 4 5% 17% 26% 10%	3020
	11th to 20th	Day	40% 2 8% 20% 22% 8%	3460
	21st to end	Day	42% 3 7% 22% 23% 3	4565
January	1st to 10th	Night	36% 5% 6% 22% 23% 7%	7636
	11th to 20th	Night	37% 3 5% 18% 27% 10%	7680
	21st to end	Night	48% 3 4 14% 24% 8%	8184
February	1st to 10th	Night	40% 3 6% 18% 23% 10%	2520
	11th to 20th	Night	44% 3 5% 17% 21% 9%	2459
	21st to end	Night	42% 4 6% 16% 17% 14%	2076
March	1st to 10th	Night	46% 5% 8% 15% 15% 11%	5225
	11th to 20th	Night	30% 5% 9% 13% 25% 19%	5090
	21st to end	Night	38% 4 6% 20% 20% 12%	5588
April	1st to 10th	Night	34% 5% 10% 21% 19% 11%	2310
	11th to 20th	Night	31% 3 5% 23% 26% 12%	2128
	21st to end	Night	29% 5% 12% 24% 23% 7%	1907
May	1st to 10th	Night	39% 9% 14% 19% 15% 5%	5264
	11th to 20th	Night	39% 8% 16% 24% 13% 1	5235
	21st to end	Night	41% 9% 13% 19% 15% 2	5771
June	1st to 10th	Night	37% 11% 17% 19% 15% 2	1890
	11th to 20th	Night	30% 10% 19% 27% 12% 2	1890
	21st to end	Night	33% 9% 23% 19% 12% 4	1890
July	1st to 10th	Night	47% 14% 20% 15% 3 1	4105
	11th to 20th	Night	35% 15% 29% 16% 4	4051
	21st to end	Night	46% 14% 20% 15% 3 1	4297
August	1st to 10th	Night	46% 10% 19% 21% 4	2904
	11th to 20th	Night	32% 10% 18% 25% 13% 1	3118
	21st to end	Night	30% 7% 17% 29% 15% 2	3637
September	1st to 10th	Night	40% 10% 15% 16% 16% 4	2200
	11th to 20th	Night	38% 9% 10% 18% 19% 5%	2200
	21st to end	Night	38% 6% 10% 18% 21% 7%	2200
October	1st to 10th	Night	33% 6% 6% 13% 29% 13%	3590
	11th to 20th	Night	17% 2 4 14% 31% 32%	3796
	21st to end	Night	21% 3 4 19% 33% 19%	4252
November	1st to 10th	Night	33% 4 8% 14% 28% 13%	2552
	11th to 20th	Night	32% 2 6% 18% 28% 14%	2730
	21st to end	Night	37% 4 7% 18% 25% 11%	2730
December	1st to 10th	Night	34% 4 5% 20% 29% 8%	4380
	11th to 20th	Night	37% 4 10% 18% 23% 8%	4954
	21st to end	Night	45% 3 5% 23% 22% 3	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	24% 18% 42% 14% 2	330
	11th to 20th	Day	22% 26% 31% 14% 6% 1	330
	21st to end	Day	26% 26% 34% 10% 3	363
February	1st to 10th	Day	25% 18% 38% 16% 3	330
	11th to 20th	Day	35% 18% 33% 13% 2	330
	21st to end	Day	28% 18% 38% 12% 3	273
March	1st to 10th	Day	24% 18% 27% 25% 6% 1	440
	11th to 20th	Day	21% 15% 34% 20% 9% 1	540
	21st to end	Day	19% 16% 36% 21% 9%	594
April	1st to 10th	Day	20% 16% 27% 25% 11% 1	540
	11th to 20th	Day	14% 13% 28% 26% 15% 3	532
	21st to end	Day	12% 10% 26% 31% 18% 3	540
May	1st to 10th	Day	13% 12% 27% 27% 14% 6%	543
	11th to 20th	Day	14% 6% 24% 28% 19% 9%	567
	21st to end	Day	13% 6% 20% 28% 20% 13%	617
June	1st to 10th	Day	12% 4 18% 26% 28% 12%	570
	11th to 20th	Day	8% 4 19% 26% 25% 18%	570
	21st to end	Day	6% 2 15% 31% 28% 18%	570
July	1st to 10th	Day	7% 2 10% 24% 34% 22%	565
	11th to 20th	Day	7% 2 6% 21% 38% 26%	544
	21st to end	Day	5% 2 7% 28% 37% 21%	576
August	1st to 10th	Day	14% 4 13% 24% 28% 17%	526
	11th to 20th	Day	9% 2 8% 25% 36% 20%	519
	21st to end	Day	14% 2 10% 27% 32% 14%	583
September	1st to 10th	Day	10% 3 16% 28% 31% 13%	530
	11th to 20th	Day	15% 3 13% 28% 31% 10%	530
	21st to end	Day	13% 4 18% 29% 25% 10%	530
October	1st to 10th	Day	16% 7% 25% 25% 19% 8%	530
	11th to 20th	Day	12% 8% 23% 33% 18% 6%	530
	21st to end	Day	15% 8% 26% 29% 18% 5%	583
November	1st to 10th	Day	20% 8% 27% 26% 16% 3	440
	11th to 20th	Day	17% 13% 40% 21% 7% 2	330
	21st to end	Day	18% 13% 33% 25% 10% 1	330
December	1st to 10th	Day	29% 16% 31% 17% 5% 1	330
	11th to 20th	Day	26% 13% 33% 17% 9% 1	330
	21st to end	Day	31% 13% 33% 18% 5% 1	363
January	1st to 10th	Night	22% 17% 32% 22% 5%	840
	11th to 20th	Night	21% 15% 30% 26% 9%	840
	21st to end	Night	22% 16% 34% 25% 3	924
February	1st to 10th	Night	19% 12% 32% 30% 6%	840
	11th to 20th	Night	23% 18% 30% 26% 3	823
	21st to end	Night	21% 15% 34% 27% 3	692
March	1st to 10th	Night	16% 13% 33% 31% 7%	840
	11th to 20th	Night	17% 14% 31% 28% 9%	840
	21st to end	Night	17% 12% 32% 29% 9% 1	924
April	1st to 10th	Night	14% 14% 31% 28% 13%	840
	11th to 20th	Night	13% 11% 27% 32% 16% 1	676
	21st to end	Night	8% 7% 25% 40% 19% 1	630
May	1st to 10th	Night	10% 7% 25% 36% 20% 2	630
	11th to 20th	Night	11% 3 22% 36% 23% 5%	621
	21st to end	Night	12% 3 17% 34% 30% 5%	683
June	1st to 10th	Night	10% 2 13% 39% 31% 5%	630
	11th to 20th	Night	6% 3 14% 32% 34% 12%	630
	21st to end	Night	7% 1 8% 35% 39% 10%	630
July	1st to 10th	Night	8% 1 8% 27% 40% 15%	615
	11th to 20th	Night	8% 1 7% 21% 47% 16%	597
	21st to end	Night	6% 1 9% 28% 46% 11%	657
August	1st to 10th	Night	11% 1 9% 28% 40% 11%	597
	11th to 20th	Night	10% 1 8% 29% 41% 10%	594
	21st to end	Night	15% 1 10% 25% 38% 10%	685
September	1st to 10th	Night	9% 2 15% 28% 37% 10%	800
	11th to 20th	Night	13% 2 12% 29% 39% 5%	800
	21st to end	Night	14% 3 17% 30% 33% 4	800
October	1st to 10th	Night	13% 4 21% 33% 24% 5%	800
	11th to 20th	Night	12% 7% 22% 33% 24% 3	800
	21st to end	Night	14% 8% 23% 31% 22% 2	880
November	1st to 10th	Night	15% 6% 23% 35% 20% 1	820
	11th to 20th	Night	16% 10% 27% 31% 14% 2	840
	21st to end	Night	14% 12% 28% 32% 13% 1	840
December	1st to 10th	Night	19% 13% 29% 27% 10% 1	840
	11th to 20th	Night	20% 11% 28% 31% 10%	840
	21st to end	Night	27% 12% 24% 29% 8%	924

Page generated at 2026-07-13 03:14:50. Version ac07

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