Cedarville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cedarville clear sky chart from 2005-11-06 to 2025-06-10.

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	3 5% 2 6% 4 4 4 4 5% 7% 55%	123608
	Night	3 6% 2 6% 5% 5% 5% 4 7% 8% 49%	123436
Transparency	Day	28% 4 9% 22% 23% 15%	123351
	Night	30% 4 11% 23% 20% 11%	123280
Seeing	Day	5% 8% 22% 30% 24% 11%	15551
	Night	6% 4 19% 44% 24% 3	24833

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	1 10% 5% 12% 8% 7% 8% 6% 8% 9% 25%	3639
	11th to 20th	Day	3 7% 3 11% 8% 8% 5% 4 5% 6% 38%	3640
	21st to end	Day	4 10% 4 9% 6% 5% 5% 3 5% 6% 43%	4416
February	1st to 10th	Day	3 7% 3 8% 6% 6% 7% 7% 7% 11% 35%	1800
	11th to 20th	Day	2 6% 3 9% 7% 6% 8% 5% 7% 12% 36%	1877
	21st to end	Day	2 8% 3 7% 6% 6% 7% 6% 8% 10% 37%	1650
March	1st to 10th	Day	3 11% 5% 11% 8% 7% 6% 5% 6% 8% 31%	4518
	11th to 20th	Day	2 7% 2 6% 4 5% 6% 5% 7% 11% 44%	4929
	21st to end	Day	3 8% 4 10% 7% 7% 6% 5% 7% 8% 35%	5827
April	1st to 10th	Day	4 10% 4 9% 7% 5% 5% 4 6% 8% 37%	2400
	11th to 20th	Day	5% 8% 3 7% 5% 4 5% 4 5% 8% 45%	2369
	21st to end	Day	5% 7% 3 7% 5% 5% 5% 4 6% 8% 45%	2400
May	1st to 10th	Day	5% 6% 2 6% 3 3 3 3 4 6% 58%	6011
	11th to 20th	Day	3 4 1 4 3 3 3 4 5% 8% 61%	6277
	21st to end	Day	4 4 1 4 3 3 3 3 4 7% 64%	6902
June	1st to 10th	Day	5% 5% 2 6% 4 4 4 5% 7% 9% 49%	2789
	11th to 20th	Day	3 4 1 4 2 3 4 3 4 6% 65%	2660
	21st to end	Day	3 2 1 3 2 3 3 2 4 5% 74%	2660
July	1st to 10th	Day	1 1 1 1 2 1 1 3 3 86%	4420
	11th to 20th	Day	2 2 1 2 2 2 2 2 3 4 78%	4420
	21st to end	Day	1 1 2 2 2 3 2 4 5% 78%	4790
August	1st to 10th	Day	2 2 1 3 2 2 3 3 5% 6% 70%	4132
	11th to 20th	Day	1 1 1 1 1 2 2 3 3 85%	3811
	21st to end	Day	2 2 1 1 1 2 2 2 2 4 82%	4180
September	1st to 10th	Day	2 1 1 2 2 2 2 2 3 5% 78%	2280
	11th to 20th	Day	3 2 1 4 3 3 4 4 4 6% 66%	2266
	21st to end	Day	3 3 1 3 2 3 3 2 3 5% 71%	2085
October	1st to 10th	Day	3 2 1 2 2 2 3 2 3 6% 72%	3180
	11th to 20th	Day	3 4 1 4 3 2 4 3 6% 8% 61%	3161
	21st to end	Day	2 4 1 5% 4 4 6% 5% 7% 9% 54%	3298
November	1st to 10th	Day	5% 6% 3 7% 5% 5% 5% 4 8% 8% 43%	1764
	11th to 20th	Day	4 6% 3 8% 7% 6% 6% 6% 8% 12% 35%	1800
	21st to end	Day	3 6% 2 6% 7% 6% 5% 5% 7% 11% 41%	1605
December	1st to 10th	Day	2 4 2 6% 5% 4 5% 5% 8% 11% 49%	2620
	11th to 20th	Day	4 9% 3 9% 8% 7% 7% 6% 9% 10% 28%	3028
	21st to end	Day	4 7% 4 12% 7% 6% 6% 6% 10% 11% 26%	4004
January	1st to 10th	Night	2 8% 4 10% 8% 9% 9% 7% 8% 10% 25%	6306
	11th to 20th	Night	2 9% 3 11% 9% 8% 6% 4 6% 6% 36%	6320
	21st to end	Night	3 10% 4 10% 6% 5% 5% 4 6% 7% 41%	6556
February	1st to 10th	Night	4 7% 3 7% 6% 5% 6% 6% 10% 13% 33%	2600
	11th to 20th	Night	2 8% 3 8% 6% 7% 7% 6% 9% 13% 31%	2410
	21st to end	Night	2 7% 3 8% 7% 7% 6% 6% 9% 11% 34%	1980
March	1st to 10th	Night	2 11% 5% 10% 7% 7% 6% 4 8% 8% 32%	5376
	11th to 20th	Night	3 7% 3 6% 5% 5% 6% 5% 11% 15% 35%	5054
	21st to end	Night	2 8% 2 8% 6% 7% 7% 6% 8% 10% 35%	5148
April	1st to 10th	Night	4 7% 3 7% 7% 5% 7% 5% 9% 9% 39%	2000
	11th to 20th	Night	3 8% 2 6% 6% 5% 5% 4 6% 8% 47%	1979
	21st to end	Night	5% 8% 3 5% 3 4 4 3 7% 8% 49%	2000
May	1st to 10th	Night	4 6% 2 5% 3 3 4 3 5% 5% 60%	3944
	11th to 20th	Night	3 4 2 4 4 3 4 3 7% 9% 58%	3616
	21st to end	Night	3 3 1 4 3 3 2 2 5% 7% 66%	3972
June	1st to 10th	Night	6% 6% 2 5% 3 4 4 4 5% 8% 53%	1595
	11th to 20th	Night	4 5% 1 3 2 3 2 3 4 6% 67%	1520
	21st to end	Night	2 3 1 2 3 3 3 3 3 5% 73%	1520
July	1st to 10th	Night	1 1 1 1 2 2 3 3 86%	2540
	11th to 20th	Night	2 1 1 2 2 2 2 2 4 4 79%	2540
	21st to end	Night	1 1 1 2 2 2 2 2 4 5% 79%	2761
August	1st to 10th	Night	2 2 1 3 3 3 3 2 4 6% 71%	2802
	11th to 20th	Night	1 1 1 2 1 2 1 1 3 3 83%	3035
	21st to end	Night	1 2 1 1 2 2 2 3 4 82%	3498
September	1st to 10th	Night	2 1 1 2 2 2 2 1 3 4 81%	1900
	11th to 20th	Night	2 2 2 3 2 2 3 2 5% 6% 70%	1914
	21st to end	Night	3 3 1 2 2 2 3 3 5% 7% 71%	2092
October	1st to 10th	Night	3 3 1 3 3 3 3 2 3 3 75%	3800
	11th to 20th	Night	2 3 1 3 3 3 3 3 4 6% 69%	3777
	21st to end	Night	4 4 1 4 3 4 4 4 6% 8% 57%	4264
November	1st to 10th	Night	5% 7% 2 6% 6% 5% 6% 5% 7% 8% 44%	2535
	11th to 20th	Night	4 7% 2 8% 6% 5% 7% 6% 8% 11% 37%	2600
	21st to end	Night	2 7% 2 7% 6% 5% 6% 5% 8% 11% 40%	2794
December	1st to 10th	Night	3 4 2 6% 4 5% 6% 5% 12% 11% 41%	4560
	11th to 20th	Night	4 8% 3 9% 6% 7% 7% 7% 11% 13% 24%	5176
	21st to end	Night	4 8% 3 11% 8% 8% 8% 6% 8% 10% 26%	6952

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	49% 7% 15% 22% 7%	3639
	11th to 20th	Day	44% 4 10% 24% 15% 3	3640
	21st to end	Day	41% 3 10% 15% 23% 7%	4416
February	1st to 10th	Day	39% 7% 16% 24% 11% 3	1800
	11th to 20th	Day	37% 7% 18% 24% 12% 2	1886
	21st to end	Day	36% 9% 17% 24% 10% 4	1650
March	1st to 10th	Day	49% 4 8% 24% 13% 3	4518
	11th to 20th	Day	31% 3 14% 36% 16% 1	4929
	21st to end	Day	43% 5% 16% 22% 11% 2	5827
April	1st to 10th	Day	43% 5% 17% 22% 11% 2	2400
	11th to 20th	Day	36% 4 12% 28% 17% 3	2372
	21st to end	Day	36% 5% 15% 28% 15% 2	2400
May	1st to 10th	Day	27% 3 8% 28% 33% 2	6011
	11th to 20th	Day	22% 2 8% 25% 38% 5%	6280
	21st to end	Day	22% 3 7% 34% 31% 4	6904
June	1st to 10th	Day	31% 5% 11% 28% 21% 5%	2789
	11th to 20th	Day	20% 3 8% 23% 33% 13%	2660
	21st to end	Day	14% 3 4 19% 36% 24%	2660
July	1st to 10th	Day	6% 2 2 7% 18% 65%	4351
	11th to 20th	Day	13% 2 1 7% 19% 58%	4345
	21st to end	Day	12% 2 1 9% 32% 44%	4639
August	1st to 10th	Day	15% 2 2 10% 26% 45%	4116
	11th to 20th	Day	7% 2 1 10% 37% 42%	3849
	21st to end	Day	10% 1 1 17% 38% 33%	4179
September	1st to 10th	Day	12% 2 2 11% 31% 43%	2280
	11th to 20th	Day	19% 3 6% 20% 29% 23%	2266
	21st to end	Day	17% 3 6% 22% 31% 22%	2085
October	1st to 10th	Day	17% 1 5% 17% 30% 30%	3180
	11th to 20th	Day	22% 2 6% 29% 32% 9%	3161
	21st to end	Day	24% 3 12% 31% 22% 8%	3298
November	1st to 10th	Day	37% 4 13% 21% 20% 5%	1764
	11th to 20th	Day	38% 6% 16% 24% 15% 2	1800
	21st to end	Day	33% 6% 16% 22% 19% 4	1605
December	1st to 10th	Day	28% 5% 11% 29% 24% 2	2620
	11th to 20th	Day	44% 6% 26% 18% 7%	3028
	21st to end	Day	45% 6% 18% 22% 8%	4004
January	1st to 10th	Night	46% 7% 18% 23% 5%	6306
	11th to 20th	Night	43% 5% 11% 24% 14% 3	6320
	21st to end	Night	41% 2 10% 19% 22% 7%	6556
February	1st to 10th	Night	37% 7% 17% 23% 14% 2	2600
	11th to 20th	Night	37% 7% 16% 23% 14% 2	2412
	21st to end	Night	36% 8% 18% 22% 13% 2	1980
March	1st to 10th	Night	45% 3 11% 25% 13% 3	5376
	11th to 20th	Night	33% 3 14% 34% 16%	5054
	21st to end	Night	40% 6% 19% 26% 8% 1	5148
April	1st to 10th	Night	37% 7% 19% 23% 11% 3	2000
	11th to 20th	Night	33% 5% 17% 26% 16% 3	1979
	21st to end	Night	30% 5% 18% 31% 14% 2	2000
May	1st to 10th	Night	26% 2 9% 27% 30% 7%	3941
	11th to 20th	Night	23% 3 8% 28% 32% 6%	3616
	21st to end	Night	19% 2 10% 36% 30% 2	3972
June	1st to 10th	Night	29% 4 15% 31% 19% 3	1595
	11th to 20th	Night	20% 3 8% 26% 34% 9%	1520
	21st to end	Night	15% 3 5% 20% 36% 22%	1520
July	1st to 10th	Night	5% 2 3 8% 19% 62%	2500
	11th to 20th	Night	11% 1 1 9% 20% 56%	2492
	21st to end	Night	10% 2 3 9% 34% 43%	2674
August	1st to 10th	Night	16% 2 3 10% 28% 41%	2794
	11th to 20th	Night	9% 2 1 11% 43% 33%	3063
	21st to end	Night	9% 1 2 23% 34% 30%	3498
September	1st to 10th	Night	10% 2 2 12% 30% 43%	1900
	11th to 20th	Night	15% 3 6% 22% 30% 24%	1914
	21st to end	Night	15% 3 4 25% 29% 24%	2092
October	1st to 10th	Night	17% 2 5% 14% 34% 28%	3800
	11th to 20th	Night	17% 2 9% 34% 29% 8%	3777
	21st to end	Night	25% 2 11% 32% 21% 9%	4264
November	1st to 10th	Night	37% 5% 15% 21% 18% 5%	2535
	11th to 20th	Night	36% 8% 15% 22% 18% 2	2600
	21st to end	Night	34% 6% 16% 21% 19% 4	2794
December	1st to 10th	Night	29% 6% 11% 29% 23% 2	4560
	11th to 20th	Night	42% 6% 21% 23% 8%	5176
	21st to end	Night	49% 5% 19% 19% 8% 1	6952

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	11% 13% 28% 32% 14% 4	200
	11th to 20th	Day	5% 9% 21% 35% 25% 7%	200
	21st to end	Day	8% 4 23% 33% 23% 10%	398
February	1st to 10th	Day	5% 7% 26% 33% 23% 6%	400
	11th to 20th	Day	3 12% 29% 34% 19% 4	458
	21st to end	Day	5% 10% 26% 35% 20% 4	414
March	1st to 10th	Day	8% 10% 32% 33% 15% 2	500
	11th to 20th	Day	8% 9% 25% 35% 15% 8%	500
	21st to end	Day	9% 14% 26% 31% 17% 3	550
April	1st to 10th	Day	9% 10% 27% 31% 19% 4	500
	11th to 20th	Day	6% 12% 28% 33% 16% 6%	492
	21st to end	Day	7% 10% 24% 31% 22% 7%	500
May	1st to 10th	Day	6% 11% 28% 25% 23% 7%	503
	11th to 20th	Day	11% 9% 22% 28% 20% 10%	528
	21st to end	Day	10% 7% 16% 27% 25% 15%	573
June	1st to 10th	Day	4 8% 18% 27% 28% 14%	527
	11th to 20th	Day	5% 9% 29% 24% 23% 9%	490
	21st to end	Day	2 5% 19% 29% 27% 19%	490
July	1st to 10th	Day	3 2 17% 28% 33% 17%	486
	11th to 20th	Day	1 2 18% 28% 34% 16%	484
	21st to end	Day	2 3 15% 32% 32% 17%	531
August	1st to 10th	Day	3 2 17% 29% 29% 20%	487
	11th to 20th	Day	2 5% 18% 28% 28% 18%	477
	21st to end	Day	3 4 18% 26% 30% 19%	539
September	1st to 10th	Day	3 4 17% 26% 30% 19%	490
	11th to 20th	Day	4 5% 18% 28% 29% 16%	490
	21st to end	Day	3 6% 19% 30% 29% 12%	490
October	1st to 10th	Day	6% 9% 19% 26% 26% 15%	490
	11th to 20th	Day	6% 10% 21% 23% 27% 14%	490
	21st to end	Day	5% 10% 22% 32% 20% 11%	451
November	1st to 10th	Day	8% 10% 16% 32% 22% 11%	300
	11th to 20th	Day	4 7% 22% 35% 22% 10%	300
	21st to end	Day	4 8% 21% 31% 29% 7%	203
December	1st to 10th	Day	4 10% 16% 34% 22% 15%	200
	11th to 20th	Day	8% 4 25% 38% 20% 7%	200
	21st to end	Day	6% 10% 21% 35% 23% 5%	220
January	1st to 10th	Night	6% 5% 28% 42% 17% 2	800
	11th to 20th	Night	4 7% 28% 37% 21% 3	800
	21st to end	Night	9% 4 23% 40% 21% 3	880
February	1st to 10th	Night	7% 5% 24% 45% 17% 2	800
	11th to 20th	Night	4 5% 24% 48% 15% 3	784
	21st to end	Night	5% 6% 23% 48% 17% 1	660
March	1st to 10th	Night	7% 8% 26% 42% 15% 2	800
	11th to 20th	Night	9% 6% 21% 40% 22% 3	800
	21st to end	Night	9% 7% 26% 41% 16% 1	880
April	1st to 10th	Night	5% 6% 24% 47% 17% 1	800
	11th to 20th	Night	6% 6% 24% 40% 19% 4	791
	21st to end	Night	9% 5% 17% 43% 24% 3	800
May	1st to 10th	Night	6% 5% 24% 41% 22% 1	535
	11th to 20th	Night	9% 2 15% 40% 29% 4	394
	21st to end	Night	9% 3 14% 40% 31% 3	433
June	1st to 10th	Night	7% 3 12% 46% 31% 2	399
	11th to 20th	Night	6% 2 13% 53% 24% 2	380
	21st to end	Night	2 10% 53% 34% 1	380
July	1st to 10th	Night	1 4 58% 36% 1	370
	11th to 20th	Night	1 1 6% 59% 33%	368
	21st to end	Night	1 1 4 54% 39% 1	416
August	1st to 10th	Night	3 1 3 49% 41% 3	534
	11th to 20th	Night	1 1 8% 45% 39% 4	697
	21st to end	Night	2 8% 49% 37% 4	836
September	1st to 10th	Night	2 2 8% 46% 38% 5%	760
	11th to 20th	Night	4 1 11% 35% 41% 8%	760
	21st to end	Night	5% 3 9% 42% 33% 8%	760
October	1st to 10th	Night	5% 3 13% 43% 31% 4	760
	11th to 20th	Night	3 5% 13% 44% 29% 5%	760
	21st to end	Night	6% 4 16% 46% 21% 8%	836
November	1st to 10th	Night	7% 5% 18% 45% 21% 4	780
	11th to 20th	Night	6% 4 25% 45% 17% 3	800
	21st to end	Night	4 5% 24% 44% 19% 4	800
December	1st to 10th	Night	6% 7% 22% 43% 20% 3	800
	11th to 20th	Night	9% 8% 25% 39% 17% 3	800
	21st to end	Night	9% 8% 31% 41% 10% 1	880

Page generated at 2025-06-07 07:28:16. Version ac07

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