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 2024-03-18.

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% 10% 4 6% 6% 3 5% 5% 5% 7% 33%	78720
	Night	17% 10% 4 6% 5% 3 4 4 5% 6% 34%	81068
Transparency	Day	50% 6% 11% 20% 12% 2	78442
	Night	50% 6% 11% 19% 13% 2	80865
Seeing	Day	23% 13% 24% 22% 13% 5%	14011
	Night	22% 10% 24% 28% 14% 2	24373

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	19% 19% 10% 8% 5% 2 4 3 4 5% 20%	2836
	11th to 20th	Day	18% 19% 9% 11% 9% 3 3 3 3 3 19%	2840
	21st to end	Day	24% 20% 6% 8% 7% 2 3 3 4 5% 18%	3124
February	1st to 10th	Day	21% 14% 5% 7% 6% 3 4 3 3 6% 27%	1710
	11th to 20th	Day	21% 13% 6% 9% 5% 3 4 4 4 5% 26%	1742
	21st to end	Day	24% 15% 4 6% 4 3 4 3 4 5% 28%	1570
March	1st to 10th	Day	17% 13% 4 6% 4 3 4 3 4 5% 36%	2085
	11th to 20th	Day	20% 10% 5% 5% 6% 3 4 4 5% 7% 32%	2058
	21st to end	Day	21% 11% 3 7% 5% 3 4 4 4 6% 31%	2178
April	1st to 10th	Day	15% 10% 4 6% 6% 4 5% 5% 6% 7% 34%	2010
	11th to 20th	Day	18% 7% 2 6% 4 3 4 4 4 7% 40%	2199
	21st to end	Day	21% 7% 3 6% 5% 3 4 4 6% 7% 34%	2340
May	1st to 10th	Day	20% 7% 3 6% 7% 4 5% 5% 5% 7% 31%	2340
	11th to 20th	Day	21% 7% 3 6% 6% 3 5% 5% 5% 7% 32%	2301
	21st to end	Day	12% 6% 2 5% 6% 4 6% 6% 7% 10% 38%	2531
June	1st to 10th	Day	13% 6% 2 5% 6% 4 5% 5% 6% 8% 39%	2340
	11th to 20th	Day	11% 6% 2 5% 7% 4 6% 7% 6% 9% 37%	2340
	21st to end	Day	13% 5% 3 5% 6% 4 6% 6% 7% 10% 37%	2340
July	1st to 10th	Day	12% 5% 3 6% 7% 3 7% 5% 7% 8% 37%	2340
	11th to 20th	Day	11% 5% 3 6% 7% 4 7% 6% 7% 8% 38%	2340
	21st to end	Day	16% 6% 3 6% 5% 3 6% 6% 6% 9% 34%	2547
August	1st to 10th	Day	13% 5% 2 6% 6% 4 6% 6% 9% 10% 32%	2327
	11th to 20th	Day	14% 6% 3 6% 5% 4 6% 7% 7% 10% 32%	2303
	21st to end	Day	11% 6% 2 5% 7% 4 5% 6% 6% 9% 40%	2480
September	1st to 10th	Day	15% 6% 2 4 3 2 4 5% 5% 7% 45%	2062
	11th to 20th	Day	12% 5% 2 5% 5% 3 4 5% 5% 8% 45%	1980
	21st to end	Day	19% 6% 3 5% 5% 4 4 4 4 6% 41%	1980
October	1st to 10th	Day	16% 6% 3 5% 4 2 4 4 5% 9% 43%	1854
	11th to 20th	Day	18% 7% 2 5% 5% 3 4 4 5% 6% 41%	1800
	21st to end	Day	23% 7% 3 5% 4 3 4 4 4 6% 39%	1980
November	1st to 10th	Day	13% 6% 3 5% 4 2 4 4 3 7% 49%	1766
	11th to 20th	Day	15% 12% 4 6% 5% 3 4 4 5% 6% 36%	1710
	21st to end	Day	18% 12% 4 5% 5% 3 4 4 4 6% 35%	1666
December	1st to 10th	Day	26% 14% 5% 7% 6% 3 5% 3 4 5% 23%	1520
	11th to 20th	Day	22% 15% 5% 8% 4 2 4 3 4 5% 28%	2057
	21st to end	Day	21% 18% 6% 8% 6% 3 5% 5% 6% 6% 17%	3124
January	1st to 10th	Night	18% 21% 6% 8% 7% 3 4 3 4 5% 21%	4109
	11th to 20th	Night	21% 15% 6% 11% 7% 4 4 3 3 4 21%	4120
	21st to end	Night	26% 16% 6% 8% 7% 2 3 3 3 4 22%	4532
February	1st to 10th	Night	21% 13% 5% 8% 5% 3 4 4 4 5% 29%	2470
	11th to 20th	Night	23% 13% 4 8% 6% 4 5% 4 4 4 27%	2323
	21st to end	Night	24% 14% 4 6% 5% 2 4 3 4 5% 28%	1884
March	1st to 10th	Night	18% 10% 3 6% 6% 3 4 4 4 5% 36%	2094
	11th to 20th	Night	21% 8% 4 6% 6% 3 4 3 5% 7% 33%	2068
	21st to end	Night	22% 8% 4 5% 5% 3 4 4 4 6% 34%	2178
April	1st to 10th	Night	18% 10% 3 5% 5% 3 4 5% 5% 7% 37%	1949
	11th to 20th	Night	15% 7% 3 6% 5% 3 4 4 5% 9% 39%	1725
	21st to end	Night	16% 6% 3 7% 5% 4 4 5% 5% 6% 39%	1620
May	1st to 10th	Night	19% 6% 3 6% 6% 4 5% 5% 5% 6% 35%	1620
	11th to 20th	Night	17% 8% 3 6% 6% 4 5% 4 6% 8% 33%	1592
	21st to end	Night	13% 4 2 5% 5% 3 5% 5% 7% 10% 41%	1744
June	1st to 10th	Night	10% 4 3 5% 5% 3 5% 5% 6% 9% 45%	1620
	11th to 20th	Night	9% 6% 2 5% 5% 4 5% 7% 7% 9% 40%	1620
	21st to end	Night	12% 5% 2 4 5% 3 5% 4 7% 10% 43%	1620
July	1st to 10th	Night	12% 6% 2 6% 6% 3 5% 5% 7% 9% 40%	1620
	11th to 20th	Night	9% 4 3 5% 5% 3 5% 5% 7% 10% 43%	1620
	21st to end	Night	11% 5% 3 5% 5% 3 5% 6% 7% 9% 40%	1771
August	1st to 10th	Night	8% 5% 3 6% 7% 4 6% 7% 7% 9% 38%	1611
	11th to 20th	Night	10% 5% 3 6% 5% 3 6% 4 6% 9% 43%	1598
	21st to end	Night	11% 5% 2 4 5% 3 4 5% 6% 9% 47%	1857
September	1st to 10th	Night	12% 5% 2 5% 5% 2 5% 5% 6% 8% 45%	1894
	11th to 20th	Night	11% 4 2 4 4 3 4 4 5% 8% 51%	1980
	21st to end	Night	16% 6% 2 5% 5% 3 4 4 5% 6% 46%	1980
October	1st to 10th	Night	14% 4 2 5% 4 2 5% 5% 5% 7% 47%	2106
	11th to 20th	Night	15% 7% 3 6% 4 2 3 4 4 6% 45%	2160
	21st to end	Night	22% 7% 2 5% 4 2 4 3 5% 5% 40%	2376
November	1st to 10th	Night	13% 6% 3 6% 4 3 4 5% 5% 5% 48%	2309
	11th to 20th	Night	19% 10% 3 5% 5% 3 4 5% 4 7% 35%	2470
	21st to end	Night	18% 10% 3 6% 6% 3 4 4 4 5% 36%	2507
December	1st to 10th	Night	24% 15% 5% 8% 5% 2 4 4 4 5% 25%	2660
	11th to 20th	Night	20% 15% 7% 8% 5% 3 3 4 4 5% 27%	3129
	21st to end	Night	21% 18% 6% 8% 6% 3 4 4 4 5% 22%	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	67% 4 11% 13% 5%	2837
	11th to 20th	Day	72% 3 7% 13% 4	2840
	21st to end	Day	69% 4 7% 15% 4 1	3124
February	1st to 10th	Day	60% 4 9% 18% 8% 1	1710
	11th to 20th	Day	61% 4 9% 17% 9% 1	1751
	21st to end	Day	58% 5% 8% 17% 10% 1	1570
March	1st to 10th	Day	51% 4 9% 24% 11% 1	2085
	11th to 20th	Day	52% 5% 9% 20% 13% 2	2058
	21st to end	Day	54% 6% 9% 18% 11% 2	2178
April	1st to 10th	Day	48% 5% 11% 18% 13% 3	2010
	11th to 20th	Day	44% 4 11% 19% 17% 4	2199
	21st to end	Day	48% 6% 12% 20% 11% 2	2340
May	1st to 10th	Day	52% 6% 10% 19% 10% 2	2340
	11th to 20th	Day	52% 6% 13% 17% 11% 2	2305
	21st to end	Day	39% 10% 16% 23% 11% 1	2531
June	1st to 10th	Day	41% 7% 14% 22% 16% 1	2340
	11th to 20th	Day	42% 9% 14% 21% 13% 2	2340
	21st to end	Day	39% 9% 16% 21% 14% 2	2340
July	1st to 10th	Day	43% 8% 14% 19% 13% 3	2275
	11th to 20th	Day	41% 9% 13% 21% 14% 3	2271
	21st to end	Day	43% 8% 13% 23% 11% 2	2405
August	1st to 10th	Day	43% 10% 15% 23% 9%	2314
	11th to 20th	Day	44% 9% 13% 24% 10% 1	2303
	21st to end	Day	39% 8% 14% 22% 14% 3	2480
September	1st to 10th	Day	37% 6% 11% 21% 20% 4	2062
	11th to 20th	Day	37% 5% 11% 27% 18% 2	1980
	21st to end	Day	44% 5% 9% 22% 19% 2	1980
October	1st to 10th	Day	40% 5% 12% 22% 19% 2	1854
	11th to 20th	Day	44% 4 10% 25% 17% 1	1800
	21st to end	Day	47% 4 8% 24% 15% 1	1980
November	1st to 10th	Day	37% 4 10% 27% 18% 4	1766
	11th to 20th	Day	48% 3 9% 19% 17% 3	1710
	21st to end	Day	51% 5% 10% 20% 14%	1666
December	1st to 10th	Day	65% 3 9% 18% 4 1	1520
	11th to 20th	Day	60% 4 10% 17% 9%	2054
	21st to end	Day	65% 6% 12% 13% 3	3124
January	1st to 10th	Night	66% 5% 9% 13% 6% 1	4109
	11th to 20th	Night	67% 3 10% 15% 4	4120
	21st to end	Night	68% 3 8% 16% 4 1	4532
February	1st to 10th	Night	58% 4 9% 18% 9%	2470
	11th to 20th	Night	61% 4 7% 16% 10% 1	2325
	21st to end	Night	59% 5% 9% 15% 10% 3	1884
March	1st to 10th	Night	50% 4 8% 22% 13% 1	2094
	11th to 20th	Night	52% 4 10% 20% 13% 1	2068
	21st to end	Night	52% 5% 9% 18% 13% 3	2178
April	1st to 10th	Night	47% 6% 8% 21% 15% 3	1949
	11th to 20th	Night	42% 6% 12% 19% 16% 6%	1725
	21st to end	Night	46% 6% 10% 20% 15% 2	1620
May	1st to 10th	Night	49% 8% 10% 18% 12% 3	1620
	11th to 20th	Night	48% 8% 11% 19% 11% 3	1593
	21st to end	Night	36% 9% 18% 25% 12% 1	1745
June	1st to 10th	Night	35% 9% 13% 26% 15% 3	1620
	11th to 20th	Night	37% 11% 15% 18% 17% 2	1620
	21st to end	Night	36% 7% 16% 24% 15% 2	1620
July	1st to 10th	Night	41% 8% 13% 21% 15% 3	1575
	11th to 20th	Night	34% 9% 14% 23% 17% 3	1566
	21st to end	Night	37% 9% 14% 23% 15% 1	1672
August	1st to 10th	Night	39% 10% 15% 22% 13% 1	1600
	11th to 20th	Night	38% 7% 14% 24% 16% 1	1598
	21st to end	Night	33% 7% 14% 26% 16% 4	1857
September	1st to 10th	Night	34% 9% 13% 20% 18% 7%	1894
	11th to 20th	Night	31% 7% 13% 24% 22% 3	1980
	21st to end	Night	39% 5% 11% 23% 20% 1	1980
October	1st to 10th	Night	36% 7% 12% 25% 18% 3	2106
	11th to 20th	Night	41% 4 9% 23% 20% 2	2160
	21st to end	Night	47% 4 6% 23% 17% 3	2376
November	1st to 10th	Night	38% 5% 11% 21% 21% 6%	2309
	11th to 20th	Night	49% 4 8% 18% 17% 4	2470
	21st to end	Night	51% 4 10% 19% 14% 1	2507
December	1st to 10th	Night	63% 4 8% 18% 6% 1	2660
	11th to 20th	Night	60% 4 10% 17% 9% 1	3131
	21st to end	Night	64% 5% 9% 15% 6%	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	32% 26% 24% 14% 4 1	270
	11th to 20th	Day	39% 25% 28% 7% 1	270
	21st to end	Day	37% 25% 28% 8% 2 1	297
February	1st to 10th	Day	36% 20% 33% 7% 4	270
	11th to 20th	Day	45% 26% 22% 6% 1	270
	21st to end	Day	40% 24% 28% 8%	225
March	1st to 10th	Day	32% 19% 27% 18% 4	455
	11th to 20th	Day	27% 24% 29% 14% 4 1	449
	21st to end	Day	34% 17% 27% 16% 5%	462
April	1st to 10th	Day	30% 17% 25% 20% 8%	420
	11th to 20th	Day	25% 17% 28% 17% 9% 4	412
	21st to end	Day	31% 18% 25% 16% 7% 2	420
May	1st to 10th	Day	29% 17% 25% 17% 9% 4	423
	11th to 20th	Day	25% 11% 30% 19% 12% 3	447
	21st to end	Day	16% 7% 22% 28% 18% 9%	485
June	1st to 10th	Day	14% 8% 24% 30% 17% 7%	450
	11th to 20th	Day	14% 10% 26% 25% 18% 7%	450
	21st to end	Day	15% 9% 28% 27% 15% 6%	450
July	1st to 10th	Day	14% 5% 20% 25% 19% 16%	445
	11th to 20th	Day	9% 4 22% 34% 19% 11%	444
	21st to end	Day	18% 5% 18% 29% 21% 10%	488
August	1st to 10th	Day	13% 4 19% 32% 21% 11%	446
	11th to 20th	Day	14% 7% 18% 29% 21% 11%	439
	21st to end	Day	12% 5% 15% 32% 24% 12%	495
September	1st to 10th	Day	15% 6% 18% 28% 24% 9%	450
	11th to 20th	Day	13% 3 13% 31% 28% 12%	450
	21st to end	Day	21% 9% 24% 24% 16% 5%	450
October	1st to 10th	Day	17% 7% 26% 25% 20% 5%	450
	11th to 20th	Day	20% 14% 29% 21% 13% 2	450
	21st to end	Day	27% 15% 26% 22% 9% 2	495
November	1st to 10th	Day	20% 14% 29% 24% 10% 3	364
	11th to 20th	Day	29% 17% 25% 20% 7% 1	270
	21st to end	Day	25% 22% 31% 20% 2 1	248
December	1st to 10th	Day	34% 20% 27% 14% 4 1	180
	11th to 20th	Day	32% 21% 28% 14% 4	225
	21st to end	Day	35% 22% 25% 13% 5%	297
January	1st to 10th	Night	31% 18% 28% 19% 4	760
	11th to 20th	Night	34% 17% 27% 21% 3	760
	21st to end	Night	29% 18% 31% 20% 2	836
February	1st to 10th	Night	30% 14% 29% 25% 2	760
	11th to 20th	Night	34% 19% 28% 18% 1	743
	21st to end	Night	33% 15% 33% 17% 2	628
March	1st to 10th	Night	28% 15% 28% 25% 4	760
	11th to 20th	Night	28% 16% 30% 19% 7% 1	752
	21st to end	Night	27% 15% 29% 23% 5%	792
April	1st to 10th	Night	25% 16% 30% 22% 7%	720
	11th to 20th	Night	19% 13% 31% 26% 11% 1	661
	21st to end	Night	19% 10% 33% 28% 9% 1	540
May	1st to 10th	Night	21% 8% 29% 28% 13% 1	540
	11th to 20th	Night	21% 7% 27% 30% 15% 1	531
	21st to end	Night	15% 3 21% 32% 26% 3	584
June	1st to 10th	Night	10% 4 20% 39% 25% 1	540
	11th to 20th	Night	11% 3 21% 36% 26% 3	540
	21st to end	Night	13% 4 18% 42% 21% 1	540
July	1st to 10th	Night	14% 3 16% 31% 31% 5%	525
	11th to 20th	Night	10% 2 14% 36% 34% 5%	522
	21st to end	Night	12% 2 14% 34% 32% 6%	591
August	1st to 10th	Night	10% 3 10% 39% 34% 4	537
	11th to 20th	Night	11% 4 11% 37% 32% 5%	534
	21st to end	Night	14% 3 10% 36% 32% 6%	669
September	1st to 10th	Night	13% 3 15% 33% 31% 5%	720
	11th to 20th	Night	13% 2 16% 32% 33% 4	720
	21st to end	Night	19% 5% 20% 29% 24% 3	720
October	1st to 10th	Night	15% 6% 21% 30% 26% 3	720
	11th to 20th	Night	20% 8% 26% 30% 15% 2	720
	21st to end	Night	26% 11% 21% 31% 11% 1	792
November	1st to 10th	Night	17% 9% 26% 33% 15% 1	740
	11th to 20th	Night	27% 12% 26% 25% 9% 1	760
	21st to end	Night	25% 12% 26% 29% 7% 1	760
December	1st to 10th	Night	33% 15% 26% 21% 4	760
	11th to 20th	Night	26% 18% 26% 26% 5%	760
	21st to end	Night	31% 12% 28% 27% 2	836

Page generated at 2024-03-15 14:01:41. Version ac07

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