Calhoun County Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Calhoun County Park 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	16% 10% 3 8% 5% 4 5% 4 5% 7% 33%	119406
	Night	16% 11% 4 8% 5% 4 4 3 5% 6% 34%	118808
Transparency	Day	48% 6% 11% 21% 13% 2	123093
	Night	49% 5% 10% 20% 13% 2	123258
Seeing	Day	23% 14% 25% 22% 12% 5%	15673
	Night	22% 10% 24% 28% 14% 2	25983

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	17% 20% 10% 16% 6% 3 3 2 3 4 16%	4056
	11th to 20th	Day	16% 21% 9% 11% 7% 4 4 2 3 3 20%	4060
	21st to end	Day	19% 16% 4 11% 6% 4 4 3 5% 5% 25%	4466
February	1st to 10th	Day	21% 16% 5% 8% 5% 4 3 3 3 6% 27%	1800
	11th to 20th	Day	22% 15% 5% 10% 4 4 4 2 4 5% 25%	1837
	21st to end	Day	23% 15% 4 7% 4 4 4 2 4 5% 29%	1650
March	1st to 10th	Day	17% 15% 3 7% 4 4 4 3 4 5% 33%	4930
	11th to 20th	Day	14% 8% 3 5% 5% 3 4 3 5% 8% 42%	4980
	21st to end	Day	18% 10% 3 8% 5% 4 5% 4 5% 7% 30%	5465
April	1st to 10th	Day	17% 12% 2 7% 5% 5% 5% 3 6% 7% 32%	2234
	11th to 20th	Day	17% 8% 2 6% 4 4 4 3 4 7% 40%	2447
	21st to end	Day	20% 7% 3 7% 4 4 4 4 6% 7% 34%	2600
May	1st to 10th	Day	18% 10% 3 8% 6% 6% 6% 5% 6% 8% 25%	5862
	11th to 20th	Day	18% 8% 3 8% 5% 5% 5% 4 6% 8% 31%	5861
	21st to end	Day	16% 7% 2 6% 5% 5% 6% 4 6% 9% 34%	6433
June	1st to 10th	Day	12% 6% 2 6% 6% 6% 5% 4 6% 7% 39%	2587
	11th to 20th	Day	11% 6% 2 7% 6% 6% 5% 6% 6% 9% 37%	2470
	21st to end	Day	12% 5% 3 5% 5% 5% 6% 4 8% 10% 38%	2470
July	1st to 10th	Day	9% 5% 2 7% 5% 5% 5% 5% 7% 8% 42%	4120
	11th to 20th	Day	10% 6% 2 6% 5% 5% 5% 4 7% 9% 41%	4120
	21st to end	Day	18% 8% 3 8% 5% 4 5% 4 6% 8% 30%	4466
August	1st to 10th	Day	11% 6% 3 8% 5% 6% 6% 5% 8% 10% 32%	4104
	11th to 20th	Day	11% 6% 3 7% 5% 5% 6% 5% 8% 9% 35%	4044
	21st to end	Day	6% 4 1 5% 5% 5% 5% 4 7% 9% 49%	4354
September	1st to 10th	Day	14% 6% 2 5% 3 3 4 4 5% 7% 47%	2176
	11th to 20th	Day	12% 6% 2 6% 5% 4 5% 4 5% 7% 45%	2090
	21st to end	Day	19% 7% 3 7% 4 4 4 3 4 6% 39%	2090
October	1st to 10th	Day	16% 6% 3 5% 4 3 4 3 5% 8% 44%	1957
	11th to 20th	Day	17% 7% 2 6% 4 4 4 3 5% 6% 42%	1900
	21st to end	Day	21% 7% 2 5% 3 4 4 3 4 6% 40%	2090
November	1st to 10th	Day	13% 7% 2 6% 3 3 4 3 4 7% 49%	1861
	11th to 20th	Day	15% 13% 3 7% 4 4 4 3 6% 6% 35%	1800
	21st to end	Day	17% 14% 4 7% 4 4 4 3 4 5% 33%	1753
December	1st to 10th	Day	21% 13% 3 14% 6% 4 4 2 3 4 25%	2600
	11th to 20th	Day	24% 14% 5% 8% 3 3 4 3 5% 5% 25%	3207
	21st to end	Day	18% 16% 5% 10% 5% 5% 5% 4 6% 6% 19%	4466
January	1st to 10th	Night	17% 20% 6% 17% 5% 3 3 2 3 4 20%	5889
	11th to 20th	Night	19% 15% 6% 14% 7% 5% 4 2 3 4 20%	5900
	21st to end	Night	21% 13% 5% 9% 6% 4 3 2 4 4 30%	6490
February	1st to 10th	Night	20% 14% 4 9% 4 4 4 3 4 5% 29%	2600
	11th to 20th	Night	22% 14% 4 9% 5% 5% 4 3 4 4 25%	2448
	21st to end	Night	23% 14% 4 7% 4 3 4 3 5% 5% 28%	1980
March	1st to 10th	Night	21% 12% 3 6% 4 4 3 3 3 6% 36%	4922
	11th to 20th	Night	13% 9% 3 6% 4 4 4 3 5% 7% 42%	4980
	21st to end	Night	17% 10% 3 8% 5% 5% 5% 4 5% 6% 34%	5467
April	1st to 10th	Night	18% 11% 3 6% 5% 4 4 4 5% 6% 34%	2165
	11th to 20th	Night	15% 7% 2 8% 4 4 4 4 6% 8% 38%	1919
	21st to end	Night	15% 7% 3 8% 4 5% 4 4 5% 6% 39%	1800
May	1st to 10th	Night	23% 10% 4 9% 5% 5% 4 3 5% 7% 24%	4033
	11th to 20th	Night	16% 9% 3 7% 5% 5% 5% 4 6% 9% 33%	4032
	21st to end	Night	19% 8% 3 8% 5% 4 4 3 6% 7% 32%	4421
June	1st to 10th	Night	11% 5% 2 6% 4 4 4 5% 7% 8% 44%	1797
	11th to 20th	Night	9% 6% 2 6% 4 5% 5% 6% 7% 9% 40%	1710
	21st to end	Night	12% 5% 2 6% 4 4 5% 3 7% 10% 43%	1710
July	1st to 10th	Night	10% 6% 2 7% 5% 5% 5% 5% 8% 9% 39%	2840
	11th to 20th	Night	10% 7% 2 7% 5% 4 4 4 6% 9% 41%	2840
	21st to end	Night	12% 9% 3 8% 5% 5% 5% 4 6% 7% 35%	3087
August	1st to 10th	Night	12% 7% 3 7% 5% 6% 6% 5% 7% 10% 32%	2825
	11th to 20th	Night	13% 7% 3 7% 4 4 4 4 6% 7% 41%	2785
	21st to end	Night	7% 4 1 6% 5% 5% 4 4 6% 9% 49%	3269
September	1st to 10th	Night	12% 5% 2 6% 4 3 5% 4 6% 8% 46%	2000
	11th to 20th	Night	11% 4 2 5% 4 4 4 3 5% 7% 51%	2090
	21st to end	Night	16% 7% 2 6% 4 4 4 3 5% 5% 44%	2090
October	1st to 10th	Night	13% 5% 2 6% 3 4 5% 3 5% 7% 47%	2223
	11th to 20th	Night	15% 7% 3 6% 4 3 3 3 4 6% 46%	2280
	21st to end	Night	21% 7% 2 6% 4 4 3 2 4 5% 42%	2508
November	1st to 10th	Night	13% 7% 2 6% 4 3 4 4 5% 5% 47%	2434
	11th to 20th	Night	19% 11% 3 6% 5% 4 4 4 4 7% 34%	2600
	21st to end	Night	18% 12% 3 7% 5% 4 4 3 4 5% 35%	2639
December	1st to 10th	Night	18% 13% 4 13% 4 3 4 3 4 5% 27%	4580
	11th to 20th	Night	19% 16% 7% 9% 5% 4 3 2 4 5% 26%	4965
	21st to end	Night	18% 17% 5% 9% 5% 5% 5% 4 4 6% 22%	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	73% 4 9% 11% 4	4057
	11th to 20th	Day	71% 3 6% 12% 7%	4060
	21st to end	Day	62% 4 8% 18% 7% 1	4466
February	1st to 10th	Day	60% 4 9% 18% 8% 1	1800
	11th to 20th	Day	62% 4 8% 16% 9% 1	1846
	21st to end	Day	57% 5% 8% 18% 10% 1	1650
March	1st to 10th	Day	52% 4 7% 22% 11% 4	4930
	11th to 20th	Day	39% 5% 8% 27% 18% 3	4980
	21st to end	Day	52% 6% 8% 20% 12% 2	5465
April	1st to 10th	Day	50% 5% 11% 18% 13% 3	2234
	11th to 20th	Day	44% 5% 12% 19% 17% 4	2447
	21st to end	Day	47% 6% 12% 21% 12% 2	2600
May	1st to 10th	Day	54% 7% 11% 17% 8% 2	5897
	11th to 20th	Day	50% 7% 12% 20% 10% 1	5865
	21st to end	Day	43% 9% 14% 21% 11% 3	6447
June	1st to 10th	Day	40% 7% 14% 22% 16% 1	2587
	11th to 20th	Day	41% 9% 14% 21% 14% 1	2470
	21st to end	Day	39% 9% 16% 22% 14% 2	2470
July	1st to 10th	Day	38% 8% 13% 24% 13% 3	4055
	11th to 20th	Day	37% 8% 12% 28% 14% 2	4051
	21st to end	Day	50% 6% 11% 16% 14% 1	4324
August	1st to 10th	Day	42% 9% 14% 25% 9%	4091
	11th to 20th	Day	40% 8% 11% 27% 14%	4083
	21st to end	Day	31% 7% 14% 28% 19% 2	4354
September	1st to 10th	Day	36% 6% 10% 21% 22% 5%	2176
	11th to 20th	Day	37% 5% 11% 26% 18% 3	2090
	21st to end	Day	46% 5% 9% 21% 18% 1	2090
October	1st to 10th	Day	30% 4 8% 23% 32% 3	3256
	11th to 20th	Day	35% 4 11% 24% 19% 6%	3140
	21st to end	Day	31% 3 9% 32% 20% 4	3428
November	1st to 10th	Day	37% 4 9% 27% 18% 4	1861
	11th to 20th	Day	49% 3 9% 19% 17% 3	1800
	21st to end	Day	53% 4 9% 19% 14%	1753
December	1st to 10th	Day	64% 3 9% 20% 4 1	2600
	11th to 20th	Day	61% 4 11% 16% 7%	3204
	21st to end	Day	63% 6% 11% 15% 4	4466
January	1st to 10th	Night	69% 4 8% 14% 5% 1	5889
	11th to 20th	Night	68% 4 8% 13% 6% 1	5900
	21st to end	Night	60% 2 9% 19% 8% 1	6490
February	1st to 10th	Night	58% 4 10% 18% 9%	2600
	11th to 20th	Night	62% 4 8% 16% 10%	2450
	21st to end	Night	58% 5% 9% 16% 10% 3	1980
March	1st to 10th	Night	50% 4 7% 23% 13% 2	4922
	11th to 20th	Night	41% 4 9% 24% 19% 3	4980
	21st to end	Night	50% 5% 8% 21% 14% 2	5467
April	1st to 10th	Night	49% 6% 8% 20% 15% 2	2165
	11th to 20th	Night	42% 6% 12% 20% 15% 6%	1919
	21st to end	Night	45% 6% 10% 21% 17% 2	1800
May	1st to 10th	Night	58% 7% 11% 12% 9% 2	4060
	11th to 20th	Night	46% 10% 13% 20% 10% 1	4033
	21st to end	Night	48% 8% 14% 19% 8% 3	4429
June	1st to 10th	Night	36% 9% 13% 24% 16% 3	1797
	11th to 20th	Night	36% 11% 15% 19% 17% 2	1710
	21st to end	Night	36% 7% 16% 24% 16% 2	1710
July	1st to 10th	Night	39% 8% 13% 22% 15% 4	2795
	11th to 20th	Night	37% 8% 12% 27% 13% 2	2786
	21st to end	Night	45% 9% 10% 18% 15% 3	2988
August	1st to 10th	Night	44% 9% 15% 22% 8% 1	2814
	11th to 20th	Night	41% 6% 10% 22% 20% 1	2812
	21st to end	Night	30% 6% 12% 30% 19% 2	3269
September	1st to 10th	Night	34% 9% 12% 20% 19% 7%	2000
	11th to 20th	Night	32% 7% 12% 23% 23% 3	2090
	21st to end	Night	41% 5% 10% 23% 20% 1	2090
October	1st to 10th	Night	30% 5% 8% 25% 26% 5%	3704
	11th to 20th	Night	33% 4 10% 22% 23% 9%	3779
	21st to end	Night	32% 3 6% 27% 25% 6%	4120
November	1st to 10th	Night	38% 5% 11% 21% 20% 5%	2434
	11th to 20th	Night	50% 4 8% 18% 16% 4	2600
	21st to end	Night	51% 4 10% 19% 14% 1	2639
December	1st to 10th	Night	59% 4 10% 20% 5% 1	4580
	11th to 20th	Night	62% 4 11% 16% 7%	4967
	21st to end	Night	62% 5% 10% 15% 7%	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	34% 26% 23% 13% 3 1	300
	11th to 20th	Day	39% 26% 27% 6% 1	300
	21st to end	Day	35% 26% 28% 8% 2 1	330
February	1st to 10th	Day	36% 20% 34% 6% 3	300
	11th to 20th	Day	48% 24% 22% 5% 1	300
	21st to end	Day	37% 25% 29% 8%	249
March	1st to 10th	Day	32% 20% 26% 18% 4	495
	11th to 20th	Day	28% 24% 29% 13% 4 1	500
	21st to end	Day	34% 18% 28% 16% 4	550
April	1st to 10th	Day	33% 19% 23% 18% 7%	500
	11th to 20th	Day	26% 19% 28% 16% 8% 3	492
	21st to end	Day	28% 19% 26% 18% 8% 2	500
May	1st to 10th	Day	26% 18% 27% 16% 8% 4	503
	11th to 20th	Day	24% 12% 30% 19% 11% 3	527
	21st to end	Day	18% 8% 24% 27% 16% 8%	573
June	1st to 10th	Day	13% 9% 25% 30% 16% 6%	526
	11th to 20th	Day	13% 10% 26% 27% 18% 7%	490
	21st to end	Day	15% 9% 29% 27% 16% 5%	490
July	1st to 10th	Day	14% 6% 21% 26% 19% 15%	485
	11th to 20th	Day	10% 5% 22% 35% 18% 11%	484
	21st to end	Day	19% 5% 18% 28% 20% 9%	532
August	1st to 10th	Day	13% 5% 21% 31% 20% 10%	486
	11th to 20th	Day	13% 8% 20% 29% 20% 10%	479
	21st to end	Day	11% 5% 14% 32% 26% 12%	539
September	1st to 10th	Day	15% 6% 18% 29% 23% 9%	490
	11th to 20th	Day	13% 3 13% 31% 29% 11%	490
	21st to end	Day	22% 10% 24% 24% 15% 5%	490
October	1st to 10th	Day	17% 7% 26% 26% 20% 5%	490
	11th to 20th	Day	19% 14% 28% 21% 13% 4	490
	21st to end	Day	25% 15% 27% 23% 8% 2	539
November	1st to 10th	Day	20% 14% 29% 24% 10% 3	399
	11th to 20th	Day	29% 17% 28% 20% 6% 1	300
	21st to end	Day	27% 22% 30% 19% 1 1	275
December	1st to 10th	Day	35% 19% 29% 14% 4 1	200
	11th to 20th	Day	33% 20% 28% 14% 5%	250
	21st to end	Day	35% 21% 25% 14% 5%	330
January	1st to 10th	Night	31% 18% 28% 19% 4	800
	11th to 20th	Night	34% 17% 27% 20% 2	800
	21st to end	Night	28% 18% 32% 20% 2	880
February	1st to 10th	Night	30% 15% 29% 24% 2	800
	11th to 20th	Night	34% 20% 28% 17% 1	783
	21st to end	Night	32% 16% 33% 17% 2	660
March	1st to 10th	Night	28% 15% 28% 25% 4	800
	11th to 20th	Night	28% 16% 29% 19% 7% 1	800
	21st to end	Night	26% 16% 30% 23% 5%	880
April	1st to 10th	Night	26% 16% 31% 21% 6%	800
	11th to 20th	Night	19% 13% 32% 25% 10% 1	735
	21st to end	Night	18% 10% 33% 29% 9% 1	600
May	1st to 10th	Night	21% 9% 28% 28% 13% 1	600
	11th to 20th	Night	20% 8% 27% 30% 14% 1	591
	21st to end	Night	16% 4 22% 31% 24% 3	650
June	1st to 10th	Night	11% 4 21% 39% 25% 1	599
	11th to 20th	Night	11% 3 21% 36% 26% 3	570
	21st to end	Night	14% 5% 18% 41% 21% 2	570
July	1st to 10th	Night	14% 3 16% 32% 30% 5%	555
	11th to 20th	Night	9% 3 14% 36% 33% 4	552
	21st to end	Night	12% 2 14% 35% 31% 5%	624
August	1st to 10th	Night	11% 3 10% 39% 33% 4	567
	11th to 20th	Night	11% 4 12% 38% 31% 5%	564
	21st to end	Night	13% 2 10% 35% 33% 6%	707
September	1st to 10th	Night	13% 3 15% 35% 30% 5%	760
	11th to 20th	Night	12% 3 16% 33% 33% 4	760
	21st to end	Night	19% 5% 21% 29% 23% 3	760
October	1st to 10th	Night	15% 6% 20% 30% 26% 3	760
	11th to 20th	Night	19% 8% 26% 30% 15% 2	760
	21st to end	Night	24% 10% 22% 31% 12% 1	836
November	1st to 10th	Night	17% 9% 26% 33% 15% 1	780
	11th to 20th	Night	27% 13% 27% 25% 9% 1	800
	21st to end	Night	26% 13% 26% 28% 7% 1	800
December	1st to 10th	Night	32% 15% 27% 21% 5%	800
	11th to 20th	Night	26% 18% 26% 26% 4	800
	21st to end	Night	31% 12% 28% 27% 2	880

Page generated at 2025-06-07 10:28:17. Version ac07

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