Camp Perry
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Camp Perry clear sky chart from 2005-11-06 to 2025-11-18.

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	11% 6% 2 6% 5% 5% 5% 4 6% 8% 42%	126396
	Night	13% 6% 2 6% 4 4 4 4 5% 7% 45%	123982
Transparency	Day	38% 5% 11% 21% 19% 6%	130199
	Night	37% 4 10% 20% 20% 8%	128252
Seeing	Day	15% 9% 22% 25% 20% 10%	15822
	Night	14% 7% 22% 30% 22% 4	25758

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% 9% 3 5% 2 3 3 3 4 4 48%	4056
	11th to 20th	Day	12% 6% 4 4 4 3 4 3 5% 6% 49%	4456
	21st to end	Day	22% 9% 2 5% 4 3 3 3 4 5% 40%	4972
February	1st to 10th	Day	17% 8% 3 6% 5% 4 3 4 5% 7% 38%	2000
	11th to 20th	Day	21% 6% 3 7% 4 3 3 3 5% 5% 41%	1948
	21st to end	Day	17% 7% 3 8% 5% 4 3 3 5% 5% 40%	1650
March	1st to 10th	Day	18% 8% 3 7% 5% 5% 4 4 5% 6% 36%	4480
	11th to 20th	Day	12% 6% 2 5% 4 4 5% 3 5% 7% 47%	4699
	21st to end	Day	14% 7% 3 7% 5% 5% 4 3 5% 6% 41%	5873
April	1st to 10th	Day	12% 6% 2 6% 5% 5% 4 4 6% 7% 46%	2400
	11th to 20th	Day	11% 6% 2 7% 4 3 4 3 5% 7% 47%	2374
	21st to end	Day	8% 5% 2 5% 4 4 5% 4 5% 7% 51%	2400
May	1st to 10th	Day	13% 7% 3 7% 5% 5% 5% 4 6% 8% 38%	5584
	11th to 20th	Day	13% 6% 3 7% 5% 6% 6% 5% 7% 10% 33%	5861
	21st to end	Day	9% 5% 2 6% 5% 4 6% 5% 6% 9% 43%	6433
June	1st to 10th	Day	10% 6% 3 7% 6% 5% 5% 5% 7% 11% 34%	2600
	11th to 20th	Day	6% 3 1 5% 6% 7% 6% 5% 9% 10% 41%	2600
	21st to end	Day	7% 5% 2 5% 4 5% 6% 6% 8% 12% 39%	2600
July	1st to 10th	Day	6% 5% 2 7% 6% 7% 7% 6% 9% 12% 33%	5900
	11th to 20th	Day	6% 4 2 6% 6% 6% 7% 6% 9% 14% 35%	5900
	21st to end	Day	6% 6% 2 7% 6% 8% 9% 7% 10% 13% 26%	5981
August	1st to 10th	Day	3 2 1 4 4 4 4 5% 8% 11% 52%	3905
	11th to 20th	Day	6% 4 2 5% 4 5% 5% 5% 7% 10% 48%	3849
	21st to end	Day	7% 3 2 5% 5% 5% 6% 4 7% 9% 46%	4312
September	1st to 10th	Day	8% 6% 3 7% 5% 6% 5% 4 7% 7% 42%	2379
	11th to 20th	Day	13% 6% 2 7% 4 4 4 4 5% 7% 43%	2200
	21st to end	Day	9% 5% 2 6% 4 4 5% 3 5% 7% 51%	2200
October	1st to 10th	Day	9% 5% 2 6% 4 3 4 3 5% 6% 54%	2200
	11th to 20th	Day	8% 4 2 5% 4 4 3 2 4 6% 58%	2186
	21st to end	Day	13% 5% 2 5% 3 3 3 2 4 6% 55%	2114
November	1st to 10th	Day	12% 4 3 4 3 3 3 3 4 6% 55%	1852
	11th to 20th	Day	13% 5% 1 5% 4 3 3 3 4 5% 55%	1863
	21st to end	Day	13% 6% 2 6% 4 3 3 4 5% 6% 49%	1800
December	1st to 10th	Day	18% 6% 2 5% 3 3 3 3 5% 6% 46%	2930
	11th to 20th	Day	14% 7% 2 7% 4 4 4 3 4 5% 46%	3373
	21st to end	Day	20% 7% 2 6% 3 3 3 3 4 5% 44%	4466
January	1st to 10th	Night	16% 9% 4 6% 3 3 3 2 3 4 47%	5889
	11th to 20th	Night	15% 7% 3 7% 3 3 3 3 4 5% 46%	5486
	21st to end	Night	19% 11% 2 6% 4 3 3 2 4 5% 41%	5984
February	1st to 10th	Night	16% 9% 2 6% 4 4 3 3 5% 6% 42%	2400
	11th to 20th	Night	21% 8% 2 6% 4 3 3 2 4 4 44%	2338
	21st to end	Night	17% 7% 2 7% 3 3 3 3 5% 6% 43%	1980
March	1st to 10th	Night	22% 9% 3 6% 4 3 4 3 4 6% 36%	5373
	11th to 20th	Night	13% 7% 2 4 4 3 3 3 5% 6% 49%	5261
	21st to end	Night	15% 6% 3 6% 4 3 4 3 4 6% 46%	5084
April	1st to 10th	Night	12% 5% 2 6% 4 4 4 5% 5% 8% 47%	2000
	11th to 20th	Night	14% 5% 1 6% 3 4 3 3 5% 8% 49%	1975
	21st to end	Night	8% 5% 2 4 3 4 5% 3 6% 7% 53%	2000
May	1st to 10th	Night	13% 6% 2 6% 5% 5% 4 4 6% 9% 40%	4307
	11th to 20th	Night	15% 7% 3 6% 5% 4 4 4 6% 8% 36%	4032
	21st to end	Night	8% 5% 2 5% 4 5% 5% 5% 8% 11% 42%	4421
June	1st to 10th	Night	7% 6% 2 7% 6% 7% 7% 5% 7% 11% 36%	1800
	11th to 20th	Night	6% 4 1 4 4 4 5% 5% 8% 12% 46%	1800
	21st to end	Night	5% 5% 3 5% 5% 5% 6% 5% 8% 12% 42%	1800
July	1st to 10th	Night	6% 5% 2 7% 6% 6% 7% 5% 8% 13% 35%	4058
	11th to 20th	Night	5% 4 2 6% 4 6% 7% 6% 10% 15% 35%	4057
	21st to end	Night	7% 8% 3 9% 6% 7% 7% 6% 9% 10% 28%	4852
August	1st to 10th	Night	3 2 1 4 3 4 5% 5% 8% 12% 53%	3244
	11th to 20th	Night	5% 4 1 6% 4 5% 5% 4 6% 12% 48%	3200
	21st to end	Night	5% 4 2 5% 5% 5% 6% 5% 7% 8% 48%	3586
September	1st to 10th	Night	9% 7% 3 7% 5% 5% 5% 4 6% 9% 41%	2000
	11th to 20th	Night	11% 6% 2 4 4 4 5% 4 6% 9% 46%	2200
	21st to end	Night	7% 5% 2 6% 5% 3 4 4 6% 6% 52%	2200
October	1st to 10th	Night	8% 4 2 5% 3 3 3 3 5% 7% 56%	2200
	11th to 20th	Night	11% 4 1 3 2 3 2 2 4 6% 60%	2210
	21st to end	Night	13% 5% 2 5% 3 3 3 2 3 5% 57%	2725
November	1st to 10th	Night	10% 4 2 4 4 3 3 3 5% 5% 58%	2666
	11th to 20th	Night	12% 5% 2 4 3 3 3 3 4 6% 55%	2692
	21st to end	Night	14% 5% 2 4 4 3 4 3 6% 6% 49%	2600
December	1st to 10th	Night	17% 6% 3 4 3 2 3 3 3 6% 50%	4250
	11th to 20th	Night	15% 7% 2 6% 4 3 3 3 4 5% 48%	4822
	21st to end	Night	20% 7% 2 5% 3 3 3 3 4 6% 43%	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	41% 2 3 29% 21% 4	4057
	11th to 20th	Day	37% 2 5% 23% 28% 5%	4456
	21st to end	Day	49% 2 6% 15% 16% 12%	4972
February	1st to 10th	Day	46% 3 6% 19% 19% 8%	2000
	11th to 20th	Day	46% 3 4 18% 21% 8%	1958
	21st to end	Day	45% 2 7% 16% 20% 10%	1650
March	1st to 10th	Day	49% 2 7% 14% 20% 7%	4480
	11th to 20th	Day	37% 2 5% 18% 21% 17%	4699
	21st to end	Day	45% 2 8% 18% 20% 7%	5875
April	1st to 10th	Day	38% 4 10% 20% 21% 8%	2400
	11th to 20th	Day	38% 3 7% 21% 23% 9%	2374
	21st to end	Day	31% 5% 10% 24% 27% 4	2400
May	1st to 10th	Day	45% 4 10% 25% 14% 2	5619
	11th to 20th	Day	44% 6% 17% 23% 10% 1	5865
	21st to end	Day	37% 5% 13% 25% 19% 1	6447
June	1st to 10th	Day	42% 5% 13% 25% 13% 2	2600
	11th to 20th	Day	34% 8% 16% 24% 16% 2	2600
	21st to end	Day	35% 8% 18% 24% 13% 3	2600
July	1st to 10th	Day	38% 11% 21% 21% 8% 1	5835
	11th to 20th	Day	35% 13% 28% 20% 3 1	5831
	21st to end	Day	43% 13% 19% 21% 3	5809
August	1st to 10th	Day	23% 6% 14% 31% 25%	3893
	11th to 20th	Day	30% 8% 16% 29% 15% 2	3885
	21st to end	Day	32% 7% 18% 23% 16% 3	4311
September	1st to 10th	Day	39% 5% 15% 17% 19% 6%	2379
	11th to 20th	Day	40% 5% 11% 19% 22% 4	2200
	21st to end	Day	34% 4 8% 23% 23% 7%	2200
October	1st to 10th	Day	24% 3 5% 13% 31% 24%	3590
	11th to 20th	Day	18% 2 3 17% 30% 31%	3542
	21st to end	Day	23% 2 4 17% 39% 14%	3391
November	1st to 10th	Day	32% 3 6% 19% 27% 13%	1852
	11th to 20th	Day	32% 3 7% 17% 29% 12%	1863
	21st to end	Day	37% 3 8% 17% 26% 9%	1800
December	1st to 10th	Day	40% 2 5% 21% 27% 5%	2930
	11th to 20th	Day	42% 2 8% 20% 22% 5%	3370
	21st to end	Day	44% 2 4 24% 24% 2	4466
January	1st to 10th	Night	43% 2 3 21% 27% 4	5889
	11th to 20th	Night	42% 2 3 18% 26% 9%	5486
	21st to end	Night	48% 2 3 14% 25% 8%	5984
February	1st to 10th	Night	44% 2 6% 16% 21% 10%	2400
	11th to 20th	Night	45% 3 5% 15% 22% 11%	2339
	21st to end	Night	42% 3 8% 17% 18% 12%	1980
March	1st to 10th	Night	50% 2 5% 15% 18% 10%	5373
	11th to 20th	Night	37% 3 7% 15% 22% 16%	5261
	21st to end	Night	41% 2 6% 22% 18% 9%	5084
April	1st to 10th	Night	36% 4 11% 19% 20% 11%	2000
	11th to 20th	Night	35% 3 7% 19% 25% 11%	1975
	21st to end	Night	30% 4 11% 23% 24% 8%	2000
May	1st to 10th	Night	41% 4 14% 20% 17% 3	4337
	11th to 20th	Night	44% 5% 16% 23% 11% 2	4033
	21st to end	Night	35% 5% 14% 26% 18% 3	4429
June	1st to 10th	Night	40% 7% 17% 18% 16% 2	1800
	11th to 20th	Night	28% 7% 20% 24% 17% 4	1800
	21st to end	Night	33% 9% 19% 21% 15% 4	1800
July	1st to 10th	Night	39% 10% 24% 20% 6% 1	4015
	11th to 20th	Night	33% 13% 29% 21% 3	4006
	21st to end	Night	47% 12% 19% 19% 3	4710
August	1st to 10th	Night	22% 7% 14% 36% 18% 2	3232
	11th to 20th	Night	28% 8% 19% 30% 13% 3	3230
	21st to end	Night	31% 8% 15% 21% 21% 4	3586
September	1st to 10th	Night	39% 8% 13% 17% 15% 7%	2000
	11th to 20th	Night	35% 7% 13% 19% 21% 6%	2200
	21st to end	Night	31% 5% 9% 23% 24% 8%	2200
October	1st to 10th	Night	26% 3 7% 13% 24% 27%	3590
	11th to 20th	Night	16% 2 3 15% 30% 34%	3593
	21st to end	Night	22% 2 3 20% 33% 20%	4398
November	1st to 10th	Night	29% 3 8% 17% 28% 16%	2666
	11th to 20th	Night	31% 2 4 20% 29% 14%	2692
	21st to end	Night	36% 3 7% 21% 21% 13%	2600
December	1st to 10th	Night	38% 2 6% 22% 27% 6%	4250
	11th to 20th	Night	40% 3 9% 17% 26% 5%	4824
	21st to end	Night	43% 2 5% 22% 26% 2	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% 22% 35% 15% 3	300
	11th to 20th	Day	21% 20% 34% 17% 6% 1	300
	21st to end	Day	26% 22% 35% 15% 3 1	330
February	1st to 10th	Day	24% 18% 33% 17% 7%	300
	11th to 20th	Day	32% 22% 29% 16% 2	300
	21st to end	Day	24% 20% 41% 13% 2	249
March	1st to 10th	Day	24% 19% 37% 15% 4 1	300
	11th to 20th	Day	24% 18% 32% 20% 7%	375
	21st to end	Day	21% 16% 32% 22% 8%	550
April	1st to 10th	Day	20% 15% 31% 20% 12% 2	500
	11th to 20th	Day	16% 12% 33% 27% 9% 2	492
	21st to end	Day	12% 9% 29% 31% 17% 2	500
May	1st to 10th	Day	13% 8% 28% 29% 17% 5%	503
	11th to 20th	Day	9% 6% 25% 29% 21% 9%	527
	21st to end	Day	11% 5% 21% 32% 17% 14%	573
June	1st to 10th	Day	14% 3 17% 29% 23% 15%	530
	11th to 20th	Day	8% 2 14% 26% 30% 19%	530
	21st to end	Day	9% 2 10% 28% 30% 21%	530
July	1st to 10th	Day	7% 2 7% 25% 34% 24%	525
	11th to 20th	Day	6% 2 4 22% 35% 30%	524
	21st to end	Day	6% 2 5% 23% 43% 22%	576
August	1st to 10th	Day	9% 2 8% 23% 34% 24%	526
	11th to 20th	Day	8% 2 6% 26% 37% 21%	519
	21st to end	Day	13% 2 9% 25% 30% 21%	583
September	1st to 10th	Day	7% 5% 11% 32% 30% 14%	530
	11th to 20th	Day	13% 4 12% 27% 32% 13%	530
	21st to end	Day	10% 5% 12% 34% 27% 12%	530
October	1st to 10th	Day	11% 4 22% 35% 20% 7%	530
	11th to 20th	Day	9% 7% 23% 34% 23% 3	516
	21st to end	Day	20% 13% 20% 31% 13% 3	363
November	1st to 10th	Day	20% 8% 29% 28% 10% 4	330
	11th to 20th	Day	17% 6% 41% 25% 9% 2	321
	21st to end	Day	13% 15% 32% 29% 10% 1	300
December	1st to 10th	Day	24% 18% 30% 21% 7%	300
	11th to 20th	Day	24% 13% 36% 20% 6%	300
	21st to end	Day	27% 12% 32% 22% 6% 1	330
January	1st to 10th	Night	22% 12% 37% 24% 5%	800
	11th to 20th	Night	21% 15% 27% 29% 9%	800
	21st to end	Night	21% 13% 34% 28% 4	880
February	1st to 10th	Night	21% 12% 32% 29% 6%	800
	11th to 20th	Night	26% 14% 31% 24% 5%	783
	21st to end	Night	21% 15% 36% 25% 2	660
March	1st to 10th	Night	18% 14% 32% 29% 7%	800
	11th to 20th	Night	18% 12% 34% 25% 11%	800
	21st to end	Night	17% 11% 31% 29% 11%	717
April	1st to 10th	Night	14% 10% 35% 28% 13%	600
	11th to 20th	Night	15% 10% 30% 29% 14% 2	593
	21st to end	Night	10% 8% 26% 37% 19% 1	600
May	1st to 10th	Night	11% 5% 24% 38% 19% 4	600
	11th to 20th	Night	10% 3 21% 38% 24% 4	591
	21st to end	Night	9% 2 13% 37% 33% 6%	650
June	1st to 10th	Night	9% 2 9% 39% 36% 6%	600
	11th to 20th	Night	7% 1 9% 28% 44% 10%	600
	21st to end	Night	6% 2 7% 28% 45% 12%	600
July	1st to 10th	Night	8% 2 3 28% 41% 17%	585
	11th to 20th	Night	5% 1 3 23% 47% 21%	582
	21st to end	Night	5% 2 4 25% 49% 14%	657
August	1st to 10th	Night	6% 1 3 23% 48% 19%	597
	11th to 20th	Night	8% 2 3 29% 47% 11%	594
	21st to end	Night	10% 3 7% 27% 39% 15%	660
September	1st to 10th	Night	12% 2 7% 30% 37% 11%	600
	11th to 20th	Night	14% 3 11% 29% 38% 5%	800
	21st to end	Night	9% 3 13% 32% 38% 5%	800
October	1st to 10th	Night	11% 2 20% 37% 26% 4	800
	11th to 20th	Night	13% 4 21% 38% 23% 1	800
	21st to end	Night	16% 6% 20% 35% 21% 2	880
November	1st to 10th	Night	12% 6% 22% 36% 20% 3	820
	11th to 20th	Night	14% 6% 30% 36% 13% 1	829
	21st to end	Night	15% 9% 29% 34% 12% 2	800
December	1st to 10th	Night	19% 12% 27% 30% 11% 1	800
	11th to 20th	Night	22% 8% 31% 30% 9%	800
	21st to end	Night	25% 10% 27% 31% 6%	880

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