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 2026-10-14.

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 4 2 5% 4 4 4 4 5% 7% 58%	158319
	Night	3 5% 2 6% 4 4 5% 4 7% 8% 53%	150849
Transparency	Day	25% 3 8% 21% 24% 18%	153220
	Night	28% 3 11% 23% 22% 12%	146937
Seeing	Day	5% 7% 22% 30% 24% 12%	17341
	Night	5% 4 19% 45% 24% 3	26486

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	2 9% 4 10% 7% 7% 8% 6% 9% 11% 27%	4722
	11th to 20th	Day	2 6% 3 9% 6% 6% 5% 4 5% 7% 48%	4740
	21st to end	Day	3 8% 3 7% 5% 5% 5% 4 6% 8% 45%	5721
February	1st to 10th	Day	3 7% 3 7% 6% 6% 7% 7% 7% 11% 37%	1890
	11th to 20th	Day	2 6% 3 9% 7% 7% 8% 5% 7% 11% 35%	1973
	21st to end	Day	3 7% 3 7% 6% 6% 7% 5% 8% 10% 37%	1730
March	1st to 10th	Day	3 11% 5% 11% 7% 7% 6% 5% 6% 8% 31%	4618
	11th to 20th	Day	2 7% 2 6% 4 5% 6% 5% 7% 11% 45%	5037
	21st to end	Day	3 8% 4 10% 7% 6% 6% 5% 7% 8% 36%	5955
April	1st to 10th	Day	4 10% 4 9% 7% 6% 5% 4 6% 8% 37%	2520
	11th to 20th	Day	5% 8% 2 7% 5% 5% 5% 4 5% 8% 46%	2489
	21st to end	Day	5% 7% 2 7% 5% 5% 5% 4 6% 9% 46%	2520
May	1st to 10th	Day	4 6% 2 5% 3 3 3 3 4 6% 60%	7795
	11th to 20th	Day	2 3 1 3 3 3 3 3 5% 7% 66%	8160
	21st to end	Day	5% 3 1 4 3 3 3 3 5% 7% 62%	8992
June	1st to 10th	Day	5% 4 2 5% 4 4 5% 5% 7% 9% 50%	2940
	11th to 20th	Day	3 3 1 4 2 3 3 3 4 6% 67%	2940
	21st to end	Day	3 2 1 3 2 3 3 2 4 5% 74%	2940
July	1st to 10th	Day	1 1 1 1 2 2 2 3 4 82%	8219
	11th to 20th	Day	2 2 1 3 2 2 3 2 3 4 75%	8220
	21st to end	Day	2 2 1 3 3 3 4 3 4 5% 72%	8922
August	1st to 10th	Day	1 1 1 2 1 2 2 2 4 5% 80%	7627
	11th to 20th	Day	1 1 1 1 2 2 2 4 5% 81%	7166
	21st to end	Day	3 3 1 2 2 3 3 3 4 6% 71%	7750
September	1st to 10th	Day	2 2 1 3 2 2 3 2 3 5% 76%	2520
	11th to 20th	Day	3 2 1 4 3 3 4 4 4 6% 66%	2504
	21st to end	Day	3 3 1 3 2 3 3 2 3 5% 71%	2305
October	1st to 10th	Day	3 2 1 2 2 3 3 2 3 6% 72%	3380
	11th to 20th	Day	3 4 1 4 3 2 4 3 6% 8% 61%	3292
	21st to end	Day	3 3 1 5% 4 3 6% 5% 7% 9% 54%	3403
November	1st to 10th	Day	5% 6% 3 7% 5% 5% 5% 4 8% 8% 43%	1854
	11th to 20th	Day	4 6% 2 8% 7% 6% 6% 6% 8% 11% 35%	1890
	21st to end	Day	3 6% 2 6% 6% 6% 5% 5% 7% 11% 43%	1685
December	1st to 10th	Day	2 4 2 6% 5% 4 5% 4 8% 11% 49%	2700
	11th to 20th	Day	4 9% 3 9% 7% 7% 7% 6% 9% 10% 29%	3108
	21st to end	Day	4 7% 4 12% 7% 6% 6% 6% 10% 11% 26%	4092
January	1st to 10th	Night	2 7% 4 9% 7% 8% 8% 7% 9% 11% 28%	8172
	11th to 20th	Night	2 7% 2 9% 7% 6% 5% 4 7% 6% 46%	8220
	21st to end	Night	2 8% 3 8% 6% 6% 6% 5% 7% 8% 40%	8485
February	1st to 10th	Night	3 7% 3 7% 6% 5% 6% 6% 10% 12% 34%	2730
	11th to 20th	Night	2 8% 3 9% 6% 7% 7% 6% 9% 13% 31%	2534
	21st to end	Night	2 7% 3 8% 7% 7% 6% 6% 9% 12% 35%	2076
March	1st to 10th	Night	2 11% 5% 10% 7% 7% 6% 4 8% 8% 32%	5496
	11th to 20th	Night	3 7% 2 6% 5% 5% 5% 5% 11% 15% 36%	5166
	21st to end	Night	2 7% 2 8% 6% 6% 7% 6% 8% 10% 36%	5262
April	1st to 10th	Night	3 7% 3 7% 6% 5% 7% 5% 9% 9% 40%	2100
	11th to 20th	Night	3 8% 2 6% 6% 6% 4 4 6% 8% 46%	2079
	21st to end	Night	5% 7% 2 5% 4 4 4 3 7% 8% 49%	2100
May	1st to 10th	Night	4 6% 2 5% 3 3 4 3 5% 5% 60%	5125
	11th to 20th	Night	2 3 1 3 3 3 4 3 6% 8% 63%	4700
	21st to end	Night	3 4 1 3 3 3 2 2 5% 7% 66%	5181
June	1st to 10th	Night	6% 6% 2 5% 3 4 4 4 5% 8% 54%	1680
	11th to 20th	Night	4 4 1 3 2 3 2 3 4 6% 68%	1680
	21st to end	Night	2 3 3 2 3 3 3 3 5% 73%	1680
July	1st to 10th	Night	1 1 1 1 1 2 2 4 4 83%	4740
	11th to 20th	Night	3 2 1 3 2 3 2 2 3 4 76%	4740
	21st to end	Night	1 2 1 3 3 2 3 3 4 6% 72%	5153
August	1st to 10th	Night	1 1 1 2 2 2 2 1 3 6% 79%	5187
	11th to 20th	Night	1 1 1 1 1 2 2 2 3 5% 81%	5711
	21st to end	Night	2 2 1 2 2 2 3 3 5% 6% 71%	6499
September	1st to 10th	Night	3 2 1 2 2 2 2 2 3 4 79%	2100
	11th to 20th	Night	2 2 2 3 2 2 3 2 5% 6% 69%	2116
	21st to end	Night	3 3 1 2 2 2 3 3 4 6% 71%	2312
October	1st to 10th	Night	3 3 1 2 2 3 3 2 3 3 75%	4040
	11th to 20th	Night	2 3 1 3 3 3 3 3 4 6% 68%	3933
	21st to end	Night	4 4 1 4 3 4 5% 4 6% 8% 58%	4401
November	1st to 10th	Night	5% 6% 2 6% 6% 5% 6% 5% 7% 8% 45%	2665
	11th to 20th	Night	4 7% 2 8% 6% 5% 7% 6% 8% 11% 36%	2730
	21st to end	Night	2 7% 2 7% 6% 5% 6% 5% 8% 11% 41%	2934
December	1st to 10th	Night	3 4 2 6% 4 5% 6% 5% 12% 11% 42%	4700
	11th to 20th	Night	4 8% 3 8% 6% 6% 7% 7% 11% 13% 25%	5316
	21st to end	Night	4 8% 3 11% 8% 8% 8% 6% 8% 10% 27%	7106

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	45% 6% 17% 26% 6%	4723
	11th to 20th	Day	35% 3 8% 20% 26% 8%	4740
	21st to end	Day	35% 3 12% 20% 22% 8%	5721
February	1st to 10th	Day	38% 6% 16% 25% 12% 2	1890
	11th to 20th	Day	38% 7% 18% 24% 12% 2	1982
	21st to end	Day	36% 8% 18% 24% 10% 4	1730
March	1st to 10th	Day	48% 4 8% 24% 13% 3	4618
	11th to 20th	Day	30% 3 14% 35% 16% 1	5037
	21st to end	Day	43% 5% 16% 22% 12% 2	5955
April	1st to 10th	Day	43% 5% 17% 22% 12% 2	2520
	11th to 20th	Day	36% 4 12% 28% 17% 3	2492
	21st to end	Day	35% 4 14% 28% 16% 2	2520
May	1st to 10th	Day	25% 2 6% 28% 36% 3	7795
	11th to 20th	Day	19% 2 7% 23% 41% 8%	8163
	21st to end	Day	23% 2 7% 34% 30% 4	8994
June	1st to 10th	Day	30% 4 10% 28% 22% 5%	2940
	11th to 20th	Day	19% 3 8% 23% 33% 15%	2940
	21st to end	Day	14% 3 4 19% 37% 24%	2940
July	1st to 10th	Day	8% 1 1 10% 25% 54%	8151
	11th to 20th	Day	15% 1 1 7% 21% 55%	8145
	21st to end	Day	17% 1 2 15% 25% 40%	8723
August	1st to 10th	Day	11% 2 1 7% 23% 56%	6043
	11th to 20th	Day	9% 1 1 16% 39% 34%	5648
	21st to end	Day	15% 1 2 20% 38% 24%	6077
September	1st to 10th	Day	13% 2 2 13% 31% 40%	2520
	11th to 20th	Day	20% 3 5% 20% 30% 22%	2504
	21st to end	Day	17% 2 6% 22% 31% 22%	2305
October	1st to 10th	Day	17% 1 5% 17% 30% 30%	3380
	11th to 20th	Day	22% 2 6% 29% 32% 9%	3292
	21st to end	Day	24% 3 12% 32% 22% 7%	3403
November	1st to 10th	Day	36% 4 13% 22% 20% 5%	1854
	11th to 20th	Day	38% 5% 16% 24% 15% 1	1890
	21st to end	Day	32% 6% 16% 24% 18% 3	1685
December	1st to 10th	Day	28% 5% 12% 30% 23% 2	2700
	11th to 20th	Day	43% 5% 26% 18% 7% 1	3108
	21st to end	Day	45% 6% 18% 23% 8%	4092
January	1st to 10th	Night	43% 6% 20% 26% 5%	8172
	11th to 20th	Night	35% 4 10% 19% 27% 6%	8220
	21st to end	Night	38% 2 11% 21% 23% 5%	8485
February	1st to 10th	Night	36% 6% 17% 24% 15% 2	2730
	11th to 20th	Night	38% 7% 16% 23% 14% 2	2536
	21st to end	Night	35% 8% 20% 22% 13% 2	2076
March	1st to 10th	Night	45% 3 11% 25% 13% 3	5496
	11th to 20th	Night	32% 2 14% 34% 16% 1	5166
	21st to end	Night	40% 6% 19% 27% 8% 1	5262
April	1st to 10th	Night	36% 7% 20% 24% 11% 3	2100
	11th to 20th	Night	33% 5% 17% 26% 16% 2	2079
	21st to end	Night	31% 5% 17% 31% 14% 3	2100
May	1st to 10th	Night	26% 2 7% 26% 32% 6%	5123
	11th to 20th	Night	20% 2 6% 28% 38% 6%	4700
	21st to end	Night	19% 2 10% 38% 30% 2	5182
June	1st to 10th	Night	28% 4 14% 31% 20% 3	1680
	11th to 20th	Night	19% 3 8% 25% 35% 11%	1680
	21st to end	Night	15% 3 5% 21% 36% 21%	1680
July	1st to 10th	Night	7% 1 2 13% 27% 50%	4700
	11th to 20th	Night	15% 1 1 7% 24% 52%	4692
	21st to end	Night	15% 1 5% 17% 24% 39%	5040
August	1st to 10th	Night	11% 1 2 8% 24% 53%	4095
	11th to 20th	Night	9% 1 1 21% 40% 27%	4498
	21st to end	Night	12% 1 2 28% 34% 23%	5092
September	1st to 10th	Night	12% 2 3 13% 31% 39%	2100
	11th to 20th	Night	16% 3 5% 22% 31% 23%	2116
	21st to end	Night	15% 3 4 26% 29% 23%	2312
October	1st to 10th	Night	17% 1 5% 14% 35% 28%	4040
	11th to 20th	Night	18% 2 9% 34% 29% 8%	3933
	21st to end	Night	25% 2 11% 33% 21% 8%	4401
November	1st to 10th	Night	35% 5% 15% 23% 17% 5%	2665
	11th to 20th	Night	37% 7% 15% 22% 17% 2	2730
	21st to end	Night	34% 5% 16% 22% 19% 4	2934
December	1st to 10th	Night	29% 6% 12% 29% 23% 2	4700
	11th to 20th	Night	41% 6% 21% 23% 8% 1	5316
	21st to end	Night	48% 5% 19% 20% 8% 1	7106

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% 13% 29% 30% 14% 4	220
	11th to 20th	Day	4 8% 19% 31% 28% 10%	220
	21st to end	Day	7% 3 23% 34% 23% 10%	429
February	1st to 10th	Day	5% 7% 25% 33% 24% 7%	430
	11th to 20th	Day	4 11% 30% 33% 18% 3	494
	21st to end	Day	6% 9% 29% 34% 18% 4	446
March	1st to 10th	Day	8% 9% 32% 34% 14% 2	540
	11th to 20th	Day	8% 9% 25% 35% 16% 8%	540
	21st to end	Day	9% 14% 26% 31% 17% 3	594
April	1st to 10th	Day	10% 10% 26% 29% 19% 6%	540
	11th to 20th	Day	6% 12% 27% 33% 16% 7%	532
	21st to end	Day	7% 9% 24% 30% 22% 8%	540
May	1st to 10th	Day	6% 10% 28% 26% 24% 7%	543
	11th to 20th	Day	10% 10% 22% 28% 20% 10%	568
	21st to end	Day	10% 7% 17% 26% 25% 15%	617
June	1st to 10th	Day	4 8% 19% 27% 27% 14%	570
	11th to 20th	Day	4 8% 28% 24% 23% 11%	570
	21st to end	Day	1 5% 19% 29% 26% 20%	570
July	1st to 10th	Day	3 2 17% 27% 33% 17%	566
	11th to 20th	Day	2 2 18% 30% 32% 16%	564
	21st to end	Day	2 3 16% 31% 31% 18%	619
August	1st to 10th	Day	2 2 17% 29% 29% 21%	567
	11th to 20th	Day	2 5% 18% 29% 29% 18%	557
	21st to end	Day	3 4 17% 26% 30% 19%	627
September	1st to 10th	Day	4 4 18% 26% 30% 19%	570
	11th to 20th	Day	5% 5% 18% 27% 28% 17%	570
	21st to end	Day	4 6% 18% 29% 28% 16%	570
October	1st to 10th	Day	6% 8% 19% 25% 26% 16%	570
	11th to 20th	Day	6% 10% 20% 24% 26% 14%	543
	21st to end	Day	5% 9% 21% 31% 22% 11%	490
November	1st to 10th	Day	8% 9% 16% 33% 22% 11%	330
	11th to 20th	Day	5% 7% 22% 35% 22% 10%	330
	21st to end	Day	4 7% 20% 33% 29% 8%	223
December	1st to 10th	Day	4 10% 15% 36% 22% 14%	220
	11th to 20th	Day	7% 4 25% 37% 19% 9%	220
	21st to end	Day	5% 13% 21% 33% 22% 5%	242
January	1st to 10th	Night	6% 5% 28% 42% 17% 2	840
	11th to 20th	Night	4 6% 27% 39% 21% 3	840
	21st to end	Night	8% 3 23% 41% 21% 3	924
February	1st to 10th	Night	7% 5% 24% 46% 16% 2	840
	11th to 20th	Night	4 5% 24% 49% 15% 3	824
	21st to end	Night	4 6% 24% 48% 17% 1	692
March	1st to 10th	Night	7% 7% 27% 43% 15% 2	840
	11th to 20th	Night	8% 6% 22% 40% 21% 3	840
	21st to end	Night	8% 7% 27% 41% 16% 1	924
April	1st to 10th	Night	5% 6% 23% 47% 18% 1	840
	11th to 20th	Night	6% 6% 24% 40% 19% 4	831
	21st to end	Night	9% 5% 17% 43% 24% 3	840
May	1st to 10th	Night	6% 5% 24% 41% 22% 1	562
	11th to 20th	Night	9% 2 16% 41% 28% 4	414
	21st to end	Night	9% 3 15% 41% 30% 3	455
June	1st to 10th	Night	7% 2 13% 46% 30% 1	420
	11th to 20th	Night	5% 2 14% 54% 24% 2	420
	21st to end	Night	2 10% 54% 33% 1	420
July	1st to 10th	Night	1 5% 59% 34% 1	410
	11th to 20th	Night	2 1 6% 60% 31%	408
	21st to end	Night	1 1 5% 55% 38% 1	460
August	1st to 10th	Night	3 1 3 50% 41% 3	591
	11th to 20th	Night	1 1 9% 47% 38% 4	771
	21st to end	Night	2 8% 49% 37% 3	924
September	1st to 10th	Night	3 2 8% 47% 37% 4	840
	11th to 20th	Night	4 1 11% 37% 40% 7%	840
	21st to end	Night	5% 2 10% 42% 33% 8%	840
October	1st to 10th	Night	5% 3 13% 44% 31% 4	840
	11th to 20th	Night	4 5% 14% 45% 28% 5%	812
	21st to end	Night	6% 4 16% 46% 22% 8%	880
November	1st to 10th	Night	7% 5% 19% 44% 22% 4	820
	11th to 20th	Night	7% 4 24% 46% 17% 3	840
	21st to end	Night	4 5% 24% 45% 20% 3	840
December	1st to 10th	Night	5% 6% 22% 44% 19% 3	840
	11th to 20th	Night	8% 7% 26% 38% 17% 3	840
	21st to end	Night	9% 7% 32% 40% 10% 1	924

Page generated at 2026-10-11 02:06:32. Version ac07

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