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 2025-12-18.

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	17% 9% 3 6% 4 4 4 3 5% 7% 39%	126745
	Night	17% 9% 3 7% 4 4 4 3 5% 6% 38%	124265
Transparency	Day	45% 4 12% 23% 14% 2	130294
	Night	47% 4 11% 22% 15% 2	128803
Seeing	Day	19% 6% 23% 30% 18% 5%	16607
	Night	21% 8% 27% 30% 13% 2	25481

By Month

Percentage Cloud Cover NE (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	12% 8% 3 7% 4 3 3 3 4 5% 48%	3597
	11th to 20th	Day	15% 10% 2 5% 3 2 3 3 4 5% 48%	3570
	21st to end	Day	18% 9% 3 8% 4 4 4 3 3 4 40%	4027
February	1st to 10th	Day	19% 9% 4 7% 4 5% 4 3 4 6% 35%	1895
	11th to 20th	Day	14% 8% 2 6% 4 4 4 3 4 6% 43%	1948
	21st to end	Day	18% 10% 3 5% 4 3 5% 3 4 6% 39%	1650
March	1st to 10th	Day	20% 13% 3 6% 4 3 3 2 4 5% 37%	4476
	11th to 20th	Day	15% 11% 3 6% 4 4 3 3 5% 7% 39%	4860
	21st to end	Day	24% 12% 3 7% 4 4 4 3 4 5% 32%	5638
April	1st to 10th	Day	20% 10% 3 6% 3 3 3 3 4 6% 38%	2400
	11th to 20th	Day	18% 8% 2 6% 4 4 4 3 4 6% 41%	2417
	21st to end	Day	19% 7% 2 5% 4 4 4 4 5% 6% 40%	2600
May	1st to 10th	Day	25% 12% 3 8% 4 4 4 3 5% 7% 25%	5886
	11th to 20th	Day	20% 12% 3 7% 5% 3 4 3 5% 7% 32%	5861
	21st to end	Day	19% 8% 2 7% 4 4 4 3 5% 7% 36%	6811
June	1st to 10th	Day	19% 8% 2 5% 4 4 4 4 7% 8% 35%	2800
	11th to 20th	Day	15% 7% 2 6% 5% 4 5% 4 6% 8% 39%	2800
	21st to end	Day	14% 7% 2 6% 4 4 5% 4 6% 9% 40%	2800
July	1st to 10th	Day	15% 9% 3 7% 5% 4 4 4 7% 10% 34%	6360
	11th to 20th	Day	10% 8% 2 7% 5% 5% 4 5% 7% 10% 36%	6360
	21st to end	Day	15% 6% 2 6% 4 3 4 4 5% 8% 44%	6801
August	1st to 10th	Day	16% 7% 3 7% 5% 5% 5% 4 6% 7% 35%	4235
	11th to 20th	Day	12% 7% 3 7% 4 5% 5% 4 6% 8% 40%	4175
	21st to end	Day	8% 4 1 5% 4 5% 5% 4 7% 11% 47%	4322
September	1st to 10th	Day	14% 6% 2 6% 4 4 4 3 5% 6% 47%	2355
	11th to 20th	Day	14% 5% 2 5% 3 3 3 2 5% 7% 50%	2200
	21st to end	Day	19% 6% 2 6% 4 3 4 3 5% 7% 40%	2200
October	1st to 10th	Day	20% 7% 1 4 3 3 4 3 4 6% 44%	2200
	11th to 20th	Day	16% 6% 2 5% 3 3 4 3 5% 7% 47%	1988
	21st to end	Day	19% 6% 2 5% 4 3 3 3 5% 6% 45%	1980
November	1st to 10th	Day	17% 7% 2 5% 4 4 4 2 5% 5% 45%	1851
	11th to 20th	Day	16% 8% 1 4 4 3 3 3 6% 6% 44%	1890
	21st to end	Day	18% 7% 2 5% 4 3 3 3 5% 6% 43%	1890
December	1st to 10th	Day	14% 10% 2 5% 3 3 3 2 4 6% 49%	2900
	11th to 20th	Day	17% 8% 2 6% 3 3 3 3 4 6% 44%	3042
	21st to end	Day	19% 12% 4 9% 4 4 4 3 5% 5% 32%	3960
January	1st to 10th	Night	14% 7% 2 4 3 3 3 3 4 6% 52%	6349
	11th to 20th	Night	15% 11% 4 7% 4 3 3 2 4 5% 41%	6315
	21st to end	Night	17% 10% 4 9% 4 4 4 3 4 4 36%	6927
February	1st to 10th	Night	17% 10% 3 8% 4 4 4 3 4 6% 38%	2503
	11th to 20th	Night	18% 10% 3 5% 4 4 3 3 5% 5% 39%	2338
	21st to end	Night	17% 8% 3 7% 5% 4 3 3 4 6% 41%	1980
March	1st to 10th	Night	25% 10% 2 5% 3 3 3 3 4 5% 36%	5364
	11th to 20th	Night	16% 12% 5% 8% 4 4 4 3 4 5% 36%	5099
	21st to end	Night	24% 12% 3 7% 4 4 4 3 3 4 32%	5289
April	1st to 10th	Night	19% 9% 3 7% 5% 4 4 3 4 6% 36%	2000
	11th to 20th	Night	19% 9% 2 5% 5% 4 4 3 6% 6% 37%	1931
	21st to end	Night	18% 8% 3 6% 5% 4 5% 3 5% 6% 37%	1800
May	1st to 10th	Night	27% 11% 3 9% 4 4 4 3 5% 6% 24%	4054
	11th to 20th	Night	20% 12% 4 9% 4 4 5% 4 5% 7% 26%	4033
	21st to end	Night	19% 10% 4 9% 5% 5% 4 4 6% 6% 28%	4092
June	1st to 10th	Night	16% 8% 3 7% 5% 5% 5% 4 5% 8% 34%	1600
	11th to 20th	Night	18% 9% 2 5% 4 4 5% 3 5% 8% 38%	1600
	21st to end	Night	17% 9% 3 6% 4 4 4 3 6% 9% 36%	1600
July	1st to 10th	Night	15% 13% 4 9% 4 4 4 3 5% 8% 30%	3600
	11th to 20th	Night	13% 14% 4 6% 4 4 4 3 6% 9% 33%	3600
	21st to end	Night	13% 7% 3 7% 5% 4 5% 4 6% 6% 39%	4006
August	1st to 10th	Night	19% 10% 3 6% 4 5% 5% 4 7% 6% 30%	2915
	11th to 20th	Night	9% 9% 3 7% 5% 5% 6% 4 7% 8% 38%	2872
	21st to end	Night	8% 5% 2 5% 3 3 3 4 5% 7% 54%	3572
September	1st to 10th	Night	13% 6% 2 6% 6% 4 4 4 4 7% 45%	2045
	11th to 20th	Night	14% 6% 2 5% 3 3 3 2 5% 6% 50%	2200
	21st to end	Night	19% 7% 2 7% 4 4 4 3 5% 5% 40%	2200
October	1st to 10th	Night	20% 6% 3 6% 4 4 3 3 4 5% 42%	2200
	11th to 20th	Night	16% 5% 2 5% 4 3 4 3 5% 6% 47%	2409
	21st to end	Night	18% 8% 2 6% 4 4 4 3 5% 6% 40%	2860
November	1st to 10th	Night	16% 6% 2 6% 4 4 4 3 4 5% 45%	2667
	11th to 20th	Night	16% 8% 3 5% 4 4 3 3 5% 5% 45%	2730
	21st to end	Night	15% 8% 2 5% 3 3 4 3 5% 6% 45%	2730
December	1st to 10th	Night	17% 8% 2 5% 4 3 3 3 4 4 47%	4482
	11th to 20th	Night	18% 10% 3 6% 4 3 4 3 4 5% 41%	5307
	21st to end	Night	17% 11% 5% 7% 4 4 3 3 4 7% 34%	6996

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	40% 3 8% 26% 20% 3	3598
	11th to 20th	Day	42% 4 12% 24% 13% 6%	3600
	21st to end	Day	52% 3 9% 19% 16% 1	4027
February	1st to 10th	Day	53% 2 12% 18% 13% 2	1895
	11th to 20th	Day	46% 4 11% 23% 14% 2	1957
	21st to end	Day	49% 3 11% 21% 15% 2	1650
March	1st to 10th	Day	51% 4 11% 14% 12% 8%	4479
	11th to 20th	Day	47% 3 14% 24% 11% 1	4860
	21st to end	Day	56% 3 6% 15% 13% 7%	5638
April	1st to 10th	Day	47% 3 9% 20% 18% 4	2400
	11th to 20th	Day	44% 2 10% 25% 17% 3	2417
	21st to end	Day	44% 3 9% 23% 17% 4	2600
May	1st to 10th	Day	60% 4 13% 15% 6% 1	5897
	11th to 20th	Day	53% 4 14% 19% 10% 1	5865
	21st to end	Day	46% 4 12% 23% 14% 1	6811
June	1st to 10th	Day	46% 5% 13% 24% 12%	2800
	11th to 20th	Day	41% 4 14% 25% 14% 2	2800
	21st to end	Day	41% 5% 16% 24% 13% 1	2800
July	1st to 10th	Day	45% 7% 14% 20% 12% 2	6290
	11th to 20th	Day	38% 7% 19% 24% 10% 1	6285
	21st to end	Day	38% 5% 13% 30% 13% 1	6605
August	1st to 10th	Day	46% 6% 17% 22% 8% 1	4222
	11th to 20th	Day	40% 7% 15% 28% 9% 1	4214
	21st to end	Day	27% 7% 17% 29% 19% 1	4322
September	1st to 10th	Day	38% 4 9% 27% 21% 1	2355
	11th to 20th	Day	34% 3 9% 29% 22% 3	2200
	21st to end	Day	44% 5% 8% 22% 19% 2	2200
October	1st to 10th	Day	37% 5% 12% 28% 16% 2	3590
	11th to 20th	Day	33% 3 8% 30% 24% 2	3204
	21st to end	Day	30% 4 13% 34% 16% 2	3180
November	1st to 10th	Day	42% 4 13% 23% 15% 2	1851
	11th to 20th	Day	42% 4 10% 22% 19% 3	1890
	21st to end	Day	43% 5% 11% 26% 13% 2	1890
December	1st to 10th	Day	41% 3 14% 28% 14% 1	2900
	11th to 20th	Day	44% 4 15% 16% 16% 4	3042
	21st to end	Day	63% 3 9% 16% 8% 2	3960
January	1st to 10th	Night	38% 2 9% 34% 15% 2	6349
	11th to 20th	Night	49% 4 10% 21% 12% 3	6360
	21st to end	Night	54% 3 8% 19% 14% 3	6927
February	1st to 10th	Night	51% 4 11% 22% 11% 1	2503
	11th to 20th	Night	50% 4 8% 21% 15% 2	2340
	21st to end	Night	47% 3 8% 25% 14% 3	1980
March	1st to 10th	Night	53% 3 9% 16% 14% 6%	5374
	11th to 20th	Night	52% 3 13% 18% 13% 2	5100
	21st to end	Night	59% 2 5% 11% 18% 5%	5289
April	1st to 10th	Night	51% 2 8% 20% 16% 3	2000
	11th to 20th	Night	48% 3 8% 20% 18% 3	1931
	21st to end	Night	50% 3 8% 20% 16% 4	1800
May	1st to 10th	Night	61% 4 12% 14% 6% 2	4060
	11th to 20th	Night	57% 4 13% 16% 8% 2	4034
	21st to end	Night	55% 4 10% 19% 12%	4093
June	1st to 10th	Night	49% 5% 12% 22% 12% 1	1600
	11th to 20th	Night	45% 4 10% 25% 15% 1	1600
	21st to end	Night	45% 5% 13% 23% 13% 1	1600
July	1st to 10th	Night	49% 6% 11% 19% 14%	3560
	11th to 20th	Night	44% 7% 17% 22% 10% 1	3552
	21st to end	Night	43% 5% 11% 26% 13% 1	3888
August	1st to 10th	Night	50% 7% 14% 18% 11% 1	2903
	11th to 20th	Night	40% 8% 16% 26% 9%	2899
	21st to end	Night	27% 6% 15% 28% 22% 1	3572
September	1st to 10th	Night	38% 4 11% 25% 20% 1	2045
	11th to 20th	Night	35% 3 10% 25% 23% 2	2200
	21st to end	Night	45% 5% 6% 22% 20% 2	2200
October	1st to 10th	Night	42% 5% 10% 27% 14% 2	3590
	11th to 20th	Night	30% 3 8% 26% 30% 3	3932
	21st to end	Night	35% 4 10% 29% 21% 2	4610
November	1st to 10th	Night	42% 4 11% 24% 16% 3	2667
	11th to 20th	Night	44% 3 10% 21% 18% 3	2730
	21st to end	Night	42% 3 13% 27% 12% 2	2730
December	1st to 10th	Night	44% 3 13% 25% 14%	4482
	11th to 20th	Night	50% 4 13% 15% 17% 1	5307
	21st to end	Night	57% 6% 10% 17% 10%	6996

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% 13% 34% 22% 8% 1	200
	11th to 20th	Day	22% 12% 35% 25% 7%	200
	21st to end	Day	19% 8% 41% 25% 5% 2	248
February	1st to 10th	Day	25% 9% 33% 29% 4	447
	11th to 20th	Day	20% 14% 42% 21% 4	496
	21st to end	Day	20% 11% 31% 29% 7% 1	414
March	1st to 10th	Day	22% 10% 34% 28% 6%	500
	11th to 20th	Day	17% 9% 35% 30% 9% 1	500
	21st to end	Day	23% 8% 32% 25% 8% 3	550
April	1st to 10th	Day	25% 8% 28% 28% 8% 3	500
	11th to 20th	Day	22% 7% 28% 33% 9%	492
	21st to end	Day	22% 4 22% 36% 14% 2	500
May	1st to 10th	Day	29% 4 20% 35% 11% 2	503
	11th to 20th	Day	17% 3 22% 36% 16% 6%	527
	21st to end	Day	17% 2 18% 34% 23% 6%	573
June	1st to 10th	Day	20% 2 13% 35% 25% 6%	530
	11th to 20th	Day	15% 2 17% 37% 24% 6%	530
	21st to end	Day	14% 2 14% 34% 30% 6%	530
July	1st to 10th	Day	14% 3 9% 32% 33% 9%	525
	11th to 20th	Day	11% 2 8% 31% 36% 11%	524
	21st to end	Day	13% 2 11% 36% 32% 6%	576
August	1st to 10th	Day	13% 2 8% 39% 32% 8%	526
	11th to 20th	Day	15% 3 8% 31% 34% 11%	519
	21st to end	Day	11% 3 11% 32% 29% 13%	583
September	1st to 10th	Day	16% 1 14% 33% 25% 10%	530
	11th to 20th	Day	17% 2 14% 28% 27% 12%	530
	21st to end	Day	23% 3 19% 29% 20% 7%	530
October	1st to 10th	Day	23% 4 17% 26% 22% 8%	530
	11th to 20th	Day	19% 6% 25% 26% 20% 4	451
	21st to end	Day	22% 5% 30% 26% 13% 4	462
November	1st to 10th	Day	16% 9% 26% 32% 15% 3	425
	11th to 20th	Day	21% 10% 35% 25% 9%	430
	21st to end	Day	21% 10% 32% 27% 9% 1	430
December	1st to 10th	Day	21% 9% 35% 27% 9%	362
	11th to 20th	Day	24% 14% 36% 21% 5%	214
	21st to end	Day	24% 7% 38% 20% 8% 3	220
January	1st to 10th	Night	22% 14% 40% 20% 4	800
	11th to 20th	Night	26% 15% 35% 22% 3	800
	21st to end	Night	22% 14% 38% 21% 5% 1	880
February	1st to 10th	Night	23% 13% 34% 27% 2	800
	11th to 20th	Night	24% 14% 41% 18% 2	783
	21st to end	Night	22% 13% 36% 25% 5%	660
March	1st to 10th	Night	23% 13% 34% 24% 6%	800
	11th to 20th	Night	19% 11% 34% 27% 7% 1	800
	21st to end	Night	24% 9% 31% 26% 9% 1	880
April	1st to 10th	Night	24% 7% 32% 29% 7% 1	800
	11th to 20th	Night	23% 5% 31% 33% 8%	747
	21st to end	Night	22% 4 27% 34% 13% 1	600
May	1st to 10th	Night	27% 4 23% 33% 12% 2	600
	11th to 20th	Night	23% 3 26% 35% 11% 2	592
	21st to end	Night	22% 4 14% 41% 18% 2	508
June	1st to 10th	Night	23% 2 17% 38% 19% 3	400
	11th to 20th	Night	23% 2 14% 43% 17% 2	400
	21st to end	Night	20% 3 11% 43% 23% 1	400
July	1st to 10th	Night	12% 3 12% 44% 27% 2	390
	11th to 20th	Night	15% 3 8% 42% 29% 3	388
	21st to end	Night	16% 2 9% 44% 27% 2	468
August	1st to 10th	Night	11% 2 10% 45% 30% 3	598
	11th to 20th	Night	13% 3 10% 43% 29% 3	592
	21st to end	Night	13% 2 10% 39% 30% 6%	866
September	1st to 10th	Night	15% 1 15% 36% 30% 3	800
	11th to 20th	Night	16% 3 15% 33% 26% 8%	800
	21st to end	Night	21% 3 17% 33% 24% 4	800
October	1st to 10th	Night	22% 7% 20% 27% 19% 5%	800
	11th to 20th	Night	20% 7% 28% 27% 16% 3	800
	21st to end	Night	24% 7% 31% 27% 10% 1	880
November	1st to 10th	Night	19% 7% 28% 31% 13% 2	820
	11th to 20th	Night	21% 13% 33% 24% 8% 1	840
	21st to end	Night	19% 17% 29% 26% 7% 1	840
December	1st to 10th	Night	24% 13% 35% 22% 6% 1	840
	11th to 20th	Night	24% 16% 35% 20% 4	829
	21st to end	Night	23% 11% 38% 23% 5%	880

Page generated at 2025-12-15 01:13:57. Version ac07

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