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 2024-11-08.

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% 5% 5% 5% 4 6% 8% 43%	100766
	Night	12% 6% 2 6% 4 4 4 4 6% 8% 45%	98290
Transparency	Day	38% 5% 11% 21% 19% 7%	104605
	Night	37% 4 10% 20% 21% 9%	102589
Seeing	Day	15% 9% 21% 26% 20% 10%	14480
	Night	14% 7% 22% 30% 22% 5%	24431

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	16% 10% 3 5% 3 4 4 4 4 5% 41%	2836
	11th to 20th	Day	13% 6% 2 4 4 4 4 3 4 5% 50%	3110
	21st to end	Day	23% 10% 2 4 3 2 3 2 4 5% 42%	3476
February	1st to 10th	Day	18% 8% 2 6% 5% 4 3 4 5% 7% 38%	1900
	11th to 20th	Day	21% 6% 3 6% 4 3 3 3 5% 4 42%	1848
	21st to end	Day	18% 7% 3 8% 5% 4 3 3 5% 5% 39%	1570
March	1st to 10th	Day	22% 9% 3 7% 4 4 3 3 5% 7% 34%	3120
	11th to 20th	Day	14% 7% 2 6% 5% 4 4 3 5% 7% 42%	3283
	21st to end	Day	15% 6% 3 7% 4 5% 4 4 5% 6% 41%	4099
April	1st to 10th	Day	12% 6% 2 6% 5% 4 4 4 6% 7% 46%	2280
	11th to 20th	Day	12% 6% 2 7% 5% 4 4 3 5% 7% 46%	2254
	21st to end	Day	8% 5% 2 5% 4 4 5% 4 5% 7% 52%	2280
May	1st to 10th	Day	8% 5% 2 6% 5% 5% 5% 5% 7% 9% 44%	3888
	11th to 20th	Day	15% 6% 2 6% 4 4 5% 4 6% 9% 39%	4081
	21st to end	Day	8% 5% 2 6% 4 4 5% 5% 7% 9% 45%	4476
June	1st to 10th	Day	10% 6% 3 7% 6% 5% 5% 5% 7% 11% 34%	2470
	11th to 20th	Day	6% 3 1 5% 6% 6% 6% 5% 8% 10% 42%	2470
	21st to end	Day	7% 5% 2 5% 5% 5% 5% 6% 8% 12% 39%	2470
July	1st to 10th	Day	7% 6% 2 8% 7% 8% 7% 6% 10% 11% 28%	4120
	11th to 20th	Day	7% 6% 2 7% 6% 7% 7% 6% 8% 12% 33%	4120
	21st to end	Day	8% 7% 3 8% 7% 8% 9% 6% 10% 11% 22%	4163
August	1st to 10th	Day	3 2 1 4 4 4 4 5% 8% 11% 53%	3785
	11th to 20th	Day	6% 4 2 5% 4 5% 5% 5% 7% 9% 48%	3729
	21st to end	Day	7% 3 2 5% 5% 5% 6% 5% 7% 9% 47%	4180
September	1st to 10th	Day	8% 7% 3 7% 5% 6% 5% 4 7% 7% 42%	2260
	11th to 20th	Day	14% 7% 2 8% 4 4 4 4 6% 7% 41%	2090
	21st to end	Day	10% 5% 2 6% 4 4 5% 3 5% 6% 50%	2090
October	1st to 10th	Day	8% 5% 2 6% 4 3 4 3 5% 6% 55%	2090
	11th to 20th	Day	8% 4 2 5% 4 4 4 3 4 6% 56%	2077
	21st to end	Day	12% 5% 2 5% 3 3 3 2 4 6% 55%	2009
November	1st to 10th	Day	13% 4 2 4 3 3 3 3 4 5% 55%	1735
	11th to 20th	Day	13% 5% 1 5% 5% 3 3 3 4 5% 53%	1710
	21st to end	Day	14% 6% 2 6% 4 3 3 4 4 6% 48%	1710
December	1st to 10th	Day	17% 7% 2 7% 4 3 3 4 5% 6% 42%	1710
	11th to 20th	Day	18% 7% 2 6% 5% 4 3 3 4 5% 42%	2153
	21st to end	Day	18% 9% 3 7% 4 4 3 3 5% 6% 39%	3124
January	1st to 10th	Night	18% 11% 3 5% 3 3 4 3 4 5% 41%	4109
	11th to 20th	Night	15% 8% 2 6% 4 3 3 3 4 5% 47%	3832
	21st to end	Night	22% 13% 3 6% 3 3 2 2 3 4 40%	4180
February	1st to 10th	Night	16% 9% 2 6% 4 4 3 3 5% 6% 41%	2280
	11th to 20th	Night	20% 8% 2 5% 4 3 4 2 4 4 45%	2218
	21st to end	Night	18% 7% 2 7% 3 4 3 3 5% 6% 42%	1884
March	1st to 10th	Night	24% 10% 3 6% 3 3 3 3 4 6% 36%	3733
	11th to 20th	Night	12% 6% 2 5% 4 4 4 3 6% 8% 46%	3677
	21st to end	Night	16% 6% 3 7% 5% 3 4 4 5% 5% 42%	3546
April	1st to 10th	Night	12% 5% 2 6% 4 4 4 5% 5% 8% 46%	1900
	11th to 20th	Night	14% 5% 1 5% 3 4 3 3 6% 8% 47%	1875
	21st to end	Night	8% 4 2 4 3 4 5% 3 6% 7% 54%	1900
May	1st to 10th	Night	9% 5% 2 6% 5% 5% 4 4 6% 10% 46%	3003
	11th to 20th	Night	15% 7% 2 5% 4 4 4 4 6% 8% 41%	2812
	21st to end	Night	5% 3 2 5% 4 5% 5% 5% 8% 10% 47%	3079
June	1st to 10th	Night	7% 6% 2 7% 6% 7% 7% 6% 8% 11% 35%	1710
	11th to 20th	Night	6% 4 1 4 4 3 5% 4 8% 12% 48%	1710
	21st to end	Night	5% 5% 2 5% 6% 5% 6% 5% 7% 12% 42%	1710
July	1st to 10th	Night	7% 6% 2 8% 6% 7% 7% 5% 7% 13% 31%	2840
	11th to 20th	Night	6% 5% 2 6% 5% 6% 7% 6% 10% 13% 35%	2840
	21st to end	Night	9% 9% 4 9% 7% 7% 7% 6% 8% 10% 26%	3386
August	1st to 10th	Night	3 2 1 4 4 4 5% 5% 8% 12% 53%	3144
	11th to 20th	Night	5% 4 1 6% 4 4 5% 4 6% 12% 48%	3100
	21st to end	Night	5% 4 2 5% 4 5% 5% 6% 7% 8% 49%	3476
September	1st to 10th	Night	9% 7% 3 7% 5% 5% 5% 4 6% 9% 41%	1900
	11th to 20th	Night	12% 6% 2 4 3 4 5% 4 5% 9% 45%	2090
	21st to end	Night	7% 5% 2 6% 4 3 3 4 6% 6% 52%	2090
October	1st to 10th	Night	8% 4 1 4 3 3 3 3 5% 7% 58%	2090
	11th to 20th	Night	11% 4 1 3 3 3 2 2 5% 6% 59%	2099
	21st to end	Night	13% 5% 2 5% 3 3 3 2 3 5% 57%	2589
November	1st to 10th	Night	10% 4 1 4 4 3 3 3 5% 5% 57%	2504
	11th to 20th	Night	12% 5% 2 4 3 3 3 3 5% 6% 54%	2470
	21st to end	Night	14% 6% 2 4 4 3 4 3 6% 7% 48%	2470
December	1st to 10th	Night	16% 7% 3 5% 4 3 4 3 4 6% 46%	2470
	11th to 20th	Night	17% 7% 2 6% 4 3 3 3 4 4 46%	3042
	21st to end	Night	18% 8% 3 6% 4 4 4 3 6% 7% 38%	4532

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	46% 3 4 19% 24% 5%	2837
	11th to 20th	Day	37% 2 6% 25% 23% 6%	3110
	21st to end	Day	47% 2 6% 18% 19% 9%	3476
February	1st to 10th	Day	46% 3 6% 20% 18% 7%	1900
	11th to 20th	Day	46% 2 4 18% 21% 9%	1858
	21st to end	Day	46% 2 7% 16% 19% 9%	1570
March	1st to 10th	Day	51% 3 9% 13% 17% 7%	3120
	11th to 20th	Day	42% 2 7% 20% 20% 8%	3283
	21st to end	Day	44% 3 9% 17% 21% 7%	4099
April	1st to 10th	Day	38% 3 9% 20% 21% 8%	2280
	11th to 20th	Day	39% 3 7% 21% 21% 9%	2254
	21st to end	Day	31% 5% 9% 23% 29% 4	2280
May	1st to 10th	Day	36% 3 11% 28% 18% 3	3923
	11th to 20th	Day	41% 4 12% 28% 13% 2	4085
	21st to end	Day	35% 4 13% 29% 17% 2	4489
June	1st to 10th	Day	42% 5% 13% 25% 13% 2	2470
	11th to 20th	Day	33% 8% 15% 25% 17% 3	2470
	21st to end	Day	35% 8% 17% 24% 13% 3	2470
July	1st to 10th	Day	43% 11% 22% 19% 5% 1	4055
	11th to 20th	Day	40% 10% 22% 23% 5% 1	4051
	21st to end	Day	49% 12% 15% 18% 5%	4030
August	1st to 10th	Day	22% 6% 14% 32% 26% 1	3773
	11th to 20th	Day	30% 7% 16% 29% 16% 3	3765
	21st to end	Day	32% 7% 18% 23% 16% 4	4179
September	1st to 10th	Day	40% 6% 14% 16% 19% 6%	2260
	11th to 20th	Day	42% 5% 11% 17% 21% 4	2090
	21st to end	Day	35% 4 8% 23% 23% 8%	2090
October	1st to 10th	Day	24% 3 5% 13% 32% 25%	3480
	11th to 20th	Day	18% 2 3 17% 29% 31%	3433
	21st to end	Day	23% 2 4 17% 40% 14%	3286
November	1st to 10th	Day	32% 3 6% 19% 28% 12%	1735
	11th to 20th	Day	34% 3 7% 18% 27% 12%	1710
	21st to end	Day	37% 3 8% 17% 25% 9%	1710
December	1st to 10th	Day	44% 3 7% 19% 20% 7%	1710
	11th to 20th	Day	46% 2 6% 16% 25% 5%	2150
	21st to end	Day	47% 3 5% 22% 21% 3	3124
January	1st to 10th	Night	46% 3 4 14% 27% 6%	4109
	11th to 20th	Night	41% 2 4 21% 23% 10%	3832
	21st to end	Night	50% 2 2 15% 25% 6%	4180
February	1st to 10th	Night	45% 2 6% 16% 21% 10%	2280
	11th to 20th	Night	44% 3 5% 14% 22% 11%	2219
	21st to end	Night	43% 4 8% 15% 18% 12%	1884
March	1st to 10th	Night	52% 3 7% 16% 15% 8%	3733
	11th to 20th	Night	38% 4 9% 18% 22% 10%	3677
	21st to end	Night	44% 3 7% 20% 20% 7%	3546
April	1st to 10th	Night	36% 4 10% 19% 20% 11%	1900
	11th to 20th	Night	36% 3 7% 19% 24% 11%	1875
	21st to end	Night	29% 4 10% 23% 25% 8%	1900
May	1st to 10th	Night	35% 3 14% 22% 22% 4	3033
	11th to 20th	Night	40% 5% 13% 25% 15% 2	2813
	21st to end	Night	30% 5% 14% 29% 19% 4	3087
June	1st to 10th	Night	41% 7% 17% 19% 15% 2	1710
	11th to 20th	Night	27% 6% 20% 25% 18% 4	1710
	21st to end	Night	33% 8% 18% 21% 16% 4	1710
July	1st to 10th	Night	43% 10% 23% 17% 6% 1	2795
	11th to 20th	Night	35% 11% 25% 23% 4 1	2786
	21st to end	Night	51% 10% 17% 16% 5% 1	3278
August	1st to 10th	Night	22% 7% 14% 36% 19% 2	3132
	11th to 20th	Night	28% 8% 18% 30% 13% 3	3130
	21st to end	Night	31% 8% 15% 21% 21% 4	3476
September	1st to 10th	Night	39% 8% 14% 17% 15% 7%	1900
	11th to 20th	Night	35% 7% 13% 19% 21% 6%	2090
	21st to end	Night	31% 5% 9% 24% 23% 9%	2090
October	1st to 10th	Night	25% 3 7% 13% 24% 28%	3480
	11th to 20th	Night	17% 2 3 15% 30% 33%	3482
	21st to end	Night	21% 2 3 20% 33% 20%	4262
November	1st to 10th	Night	29% 3 8% 17% 27% 16%	2504
	11th to 20th	Night	32% 2 4 19% 28% 14%	2470
	21st to end	Night	36% 3 7% 20% 21% 12%	2470
December	1st to 10th	Night	40% 3 10% 19% 22% 6%	2470
	11th to 20th	Night	42% 2 6% 13% 30% 6%	3044
	21st to end	Night	45% 3 5% 21% 23% 3	4532

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% 21% 36% 15% 3	270
	11th to 20th	Day	22% 20% 33% 17% 7% 1	270
	21st to end	Day	26% 23% 34% 14% 3 1	297
February	1st to 10th	Day	26% 20% 33% 16% 6%	270
	11th to 20th	Day	31% 21% 29% 17% 2	270
	21st to end	Day	25% 22% 40% 12% 1	225
March	1st to 10th	Day	23% 20% 35% 16% 4 1	270
	11th to 20th	Day	23% 17% 32% 22% 7%	341
	21st to end	Day	21% 16% 31% 22% 9%	506
April	1st to 10th	Day	20% 15% 30% 20% 13% 2	460
	11th to 20th	Day	17% 12% 32% 27% 9% 3	452
	21st to end	Day	12% 10% 30% 30% 16% 2	460
May	1st to 10th	Day	12% 9% 26% 30% 18% 5%	463
	11th to 20th	Day	9% 5% 23% 31% 23% 10%	487
	21st to end	Day	11% 5% 19% 33% 18% 15%	529
June	1st to 10th	Day	13% 3 16% 29% 23% 16%	490
	11th to 20th	Day	8% 2 14% 25% 30% 20%	490
	21st to end	Day	9% 2 11% 28% 30% 20%	490
July	1st to 10th	Day	8% 3 7% 25% 33% 25%	485
	11th to 20th	Day	6% 2 4 23% 34% 30%	484
	21st to end	Day	7% 2 5% 23% 42% 22%	532
August	1st to 10th	Day	7% 2 7% 22% 36% 25%	486
	11th to 20th	Day	8% 2 6% 27% 38% 20%	479
	21st to end	Day	13% 2 7% 24% 31% 22%	539
September	1st to 10th	Day	7% 5% 9% 31% 31% 16%	490
	11th to 20th	Day	14% 4 12% 26% 32% 12%	490
	21st to end	Day	11% 4 12% 33% 27% 13%	490
October	1st to 10th	Day	11% 4 22% 35% 21% 7%	490
	11th to 20th	Day	10% 7% 23% 34% 23% 2	477
	21st to end	Day	18% 13% 19% 33% 14% 4	330
November	1st to 10th	Day	22% 7% 29% 27% 11% 3	291
	11th to 20th	Day	17% 7% 42% 24% 8% 1	270
	21st to end	Day	13% 14% 33% 29% 10% 1	270
December	1st to 10th	Day	24% 17% 29% 22% 8%	270
	11th to 20th	Day	26% 13% 36% 19% 7%	270
	21st to end	Day	27% 11% 34% 23% 5% 1	297
January	1st to 10th	Night	22% 12% 36% 24% 5%	760
	11th to 20th	Night	21% 14% 27% 29% 9%	760
	21st to end	Night	21% 13% 34% 28% 4	836
February	1st to 10th	Night	21% 12% 33% 28% 6%	760
	11th to 20th	Night	25% 13% 32% 25% 6%	743
	21st to end	Night	22% 15% 36% 24% 2	628
March	1st to 10th	Night	18% 13% 32% 29% 8%	760
	11th to 20th	Night	18% 12% 34% 25% 12%	760
	21st to end	Night	17% 12% 31% 29% 11%	681
April	1st to 10th	Night	13% 10% 34% 29% 14%	570
	11th to 20th	Night	16% 10% 30% 28% 15% 2	563
	21st to end	Night	10% 8% 27% 37% 18% 1	570
May	1st to 10th	Night	11% 5% 24% 37% 20% 4	570
	11th to 20th	Night	10% 3 20% 38% 25% 5%	561
	21st to end	Night	8% 1 12% 37% 35% 7%	617
June	1st to 10th	Night	9% 1 9% 39% 36% 6%	570
	11th to 20th	Night	7% 1 9% 29% 43% 11%	570
	21st to end	Night	6% 2 7% 28% 44% 13%	570
July	1st to 10th	Night	8% 2 3 28% 41% 18%	555
	11th to 20th	Night	5% 1 3 23% 47% 20%	552
	21st to end	Night	6% 2 4 25% 49% 14%	624
August	1st to 10th	Night	5% 1 3 22% 48% 20%	567
	11th to 20th	Night	8% 2 3 30% 47% 10%	564
	21st to end	Night	10% 3 7% 26% 39% 16%	627
September	1st to 10th	Night	13% 2 7% 29% 38% 12%	570
	11th to 20th	Night	15% 3 11% 28% 38% 5%	760
	21st to end	Night	9% 3 13% 31% 39% 5%	760
October	1st to 10th	Night	10% 2 19% 37% 27% 4	760
	11th to 20th	Night	13% 4 21% 38% 23% 1	760
	21st to end	Night	15% 6% 20% 35% 22% 2	836
November	1st to 10th	Night	13% 6% 22% 36% 21% 3	771
	11th to 20th	Night	14% 7% 30% 36% 13% 1	760
	21st to end	Night	16% 8% 29% 34% 12% 2	760
December	1st to 10th	Night	19% 12% 27% 30% 12% 1	760
	11th to 20th	Night	22% 8% 30% 30% 9%	760
	21st to end	Night	25% 10% 27% 32% 5%	836

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