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 2026-10-14.

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 6% 7% 33%	148702
	Night	16% 10% 4 8% 5% 4 4 3 5% 6% 33%	143020
Transparency	Day	48% 6% 11% 21% 12% 2	152347
	Night	50% 5% 10% 20% 13% 2	147447
Seeing	Day	23% 14% 25% 22% 12% 5%	17504
	Night	22% 10% 24% 28% 14% 2	27735

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	18% 19% 8% 14% 5% 3 3 2 3 5% 18%	5258
	11th to 20th	Day	15% 18% 8% 15% 7% 4 4 2 3 4 21%	5280
	21st to end	Day	18% 14% 4 13% 8% 5% 4 3 5% 5% 21%	5780
February	1st to 10th	Day	20% 15% 5% 8% 6% 4 3 3 3 6% 27%	1890
	11th to 20th	Day	21% 14% 5% 10% 4 4 4 2 4 5% 25%	1931
	21st to end	Day	22% 15% 4 7% 4 4 4 2 4 5% 29%	1730
March	1st to 10th	Day	17% 15% 3 7% 4 4 4 3 4 5% 33%	5040
	11th to 20th	Day	14% 8% 3 5% 5% 4 4 3 5% 8% 42%	5090
	21st to end	Day	18% 10% 3 8% 5% 4 5% 4 5% 7% 30%	5586
April	1st to 10th	Day	16% 11% 2 7% 5% 5% 5% 3 6% 7% 34%	2346
	11th to 20th	Day	17% 8% 2 6% 4 4 4 4 4 7% 40%	2571
	21st to end	Day	19% 7% 3 7% 4 4 4 4 6% 7% 34%	2730
May	1st to 10th	Day	17% 9% 3 8% 5% 5% 5% 4 7% 8% 28%	7616
	11th to 20th	Day	16% 8% 3 8% 5% 5% 5% 4 6% 8% 33%	7626
	21st to end	Day	20% 7% 2 7% 5% 5% 5% 4 6% 8% 32%	8391
June	1st to 10th	Day	13% 7% 2 6% 6% 5% 5% 4 6% 8% 39%	2730
	11th to 20th	Day	10% 6% 2 7% 6% 6% 6% 6% 6% 10% 36%	2730
	21st to end	Day	12% 5% 2 5% 5% 5% 5% 5% 8% 10% 38%	2730
July	1st to 10th	Day	10% 6% 2 7% 5% 5% 5% 4 6% 8% 41%	7680
	11th to 20th	Day	13% 7% 2 7% 5% 5% 6% 5% 8% 10% 34%	7680
	21st to end	Day	15% 7% 3 8% 5% 5% 5% 5% 7% 9% 31%	8340
August	1st to 10th	Day	13% 8% 3 9% 5% 6% 6% 5% 8% 10% 27%	6014
	11th to 20th	Day	15% 7% 3 8% 5% 5% 6% 5% 8% 8% 29%	5951
	21st to end	Day	5% 4 1 5% 5% 5% 5% 4 7% 9% 48%	6341
September	1st to 10th	Day	13% 6% 2 5% 3 3 4 4 5% 7% 47%	2405
	11th to 20th	Day	12% 6% 2 6% 5% 4 5% 4 5% 7% 45%	2310
	21st to end	Day	19% 7% 3 7% 4 4 4 3 5% 6% 37%	2310
October	1st to 10th	Day	15% 6% 3 5% 4 3 4 3 5% 8% 46%	2163
	11th to 20th	Day	16% 7% 2 7% 4 4 4 4 5% 6% 43%	2030
	21st to end	Day	21% 7% 2 6% 4 4 4 3 5% 6% 39%	2200
November	1st to 10th	Day	13% 7% 3 6% 4 3 4 3 4 6% 48%	1956
	11th to 20th	Day	15% 13% 3 7% 4 4 4 3 6% 6% 35%	1890
	21st to end	Day	18% 15% 4 7% 4 4 3 3 4 6% 32%	1840
December	1st to 10th	Day	21% 14% 4 14% 6% 4 4 2 3 4 25%	2680
	11th to 20th	Day	24% 14% 5% 8% 4 3 4 3 5% 5% 25%	3292
	21st to end	Day	18% 16% 5% 10% 5% 5% 5% 4 6% 6% 19%	4565
January	1st to 10th	Night	19% 18% 6% 15% 5% 4 4 3 4 4 19%	7635
	11th to 20th	Night	18% 15% 7% 15% 7% 5% 4 2 3 4 21%	7680
	21st to end	Night	19% 12% 5% 10% 7% 5% 3 2 4 5% 28%	8401
February	1st to 10th	Night	19% 14% 4 9% 4 4 4 3 4 5% 29%	2730
	11th to 20th	Night	22% 14% 4 9% 5% 5% 4 3 4 4 26%	2573
	21st to end	Night	22% 14% 4 7% 4 3 4 3 5% 5% 28%	2076
March	1st to 10th	Night	21% 12% 3 6% 4 4 3 3 3 6% 36%	5032
	11th to 20th	Night	13% 9% 3 6% 4 4 4 3 5% 7% 42%	5090
	21st to end	Night	17% 10% 3 8% 5% 5% 5% 4 5% 6% 33%	5588
April	1st to 10th	Night	17% 11% 3 6% 5% 4 4 3 5% 7% 35%	2273
	11th to 20th	Night	14% 7% 2 8% 4 4 4 4 6% 8% 38%	2016
	21st to end	Night	15% 7% 3 8% 5% 5% 4 4 5% 6% 39%	1890
May	1st to 10th	Night	21% 9% 4 8% 5% 5% 4 3 5% 6% 28%	5237
	11th to 20th	Night	13% 7% 3 7% 5% 5% 5% 5% 6% 9% 35%	5234
	21st to end	Night	23% 10% 4 8% 5% 4 4 3 5% 7% 29%	5761
June	1st to 10th	Night	11% 5% 2 6% 4 4 4 4 7% 8% 43%	1890
	11th to 20th	Night	9% 7% 3 7% 5% 5% 5% 5% 7% 9% 39%	1890
	21st to end	Night	12% 5% 2 6% 4 4 5% 3 7% 9% 42%	1890
July	1st to 10th	Night	11% 8% 2 7% 5% 5% 4 4 6% 8% 39%	5278
	11th to 20th	Night	14% 7% 3 7% 5% 4 5% 4 6% 10% 35%	5277
	21st to end	Night	12% 8% 3 8% 5% 4 5% 5% 7% 8% 35%	5736
August	1st to 10th	Night	14% 8% 3 9% 6% 6% 7% 5% 7% 9% 26%	4135
	11th to 20th	Night	18% 9% 3 8% 5% 4 4 3 5% 7% 32%	4095
	21st to end	Night	6% 4 1 5% 4 5% 5% 4 6% 10% 48%	4737
September	1st to 10th	Night	11% 5% 2 5% 4 3 5% 4 6% 8% 47%	2210
	11th to 20th	Night	11% 4 2 5% 4 4 4 3 5% 7% 51%	2310
	21st to end	Night	17% 7% 2 6% 4 4 4 3 5% 5% 42%	2310
October	1st to 10th	Night	13% 4 2 6% 3 4 4 3 5% 7% 49%	2457
	11th to 20th	Night	15% 7% 2 6% 4 3 4 3 4 6% 46%	2437
	21st to end	Night	21% 7% 2 6% 4 4 3 2 5% 5% 41%	2640
November	1st to 10th	Night	13% 7% 2 6% 4 3 4 4 5% 5% 47%	2559
	11th to 20th	Night	19% 11% 3 6% 5% 4 4 3 4 6% 35%	2730
	21st to end	Night	19% 12% 4 7% 5% 4 4 3 4 5% 34%	2771
December	1st to 10th	Night	18% 13% 4 14% 4 4 4 3 4 5% 27%	4720
	11th to 20th	Night	19% 16% 7% 9% 5% 4 3 2 4 5% 26%	5099
	21st to end	Night	18% 17% 5% 10% 5% 5% 5% 4 4 6% 22%	6633

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	70% 4 11% 12% 3	5259
	11th to 20th	Day	69% 3 7% 12% 8% 1	5280
	21st to end	Day	65% 4 8% 16% 6% 1	5780
February	1st to 10th	Day	60% 4 9% 19% 8% 1	1890
	11th to 20th	Day	62% 4 8% 16% 9% 1	1940
	21st to end	Day	58% 5% 8% 19% 10% 1	1730
March	1st to 10th	Day	52% 4 7% 21% 11% 4	5040
	11th to 20th	Day	40% 5% 8% 27% 18% 3	5090
	21st to end	Day	52% 6% 8% 20% 12% 2	5586
April	1st to 10th	Day	49% 5% 11% 19% 13% 3	2346
	11th to 20th	Day	43% 5% 12% 20% 17% 4	2571
	21st to end	Day	47% 6% 12% 22% 12% 2	2730
May	1st to 10th	Day	51% 7% 11% 21% 8% 2	7651
	11th to 20th	Day	47% 7% 12% 23% 11% 1	7630
	21st to end	Day	48% 7% 11% 17% 12% 5%	8405
June	1st to 10th	Day	41% 7% 13% 21% 16% 1	2730
	11th to 20th	Day	41% 9% 14% 21% 13% 1	2730
	21st to end	Day	38% 9% 15% 22% 14% 2	2730
July	1st to 10th	Day	40% 8% 12% 23% 15% 2	7615
	11th to 20th	Day	42% 8% 12% 28% 10% 1	7611
	21st to end	Day	46% 7% 12% 18% 16% 1	8156
August	1st to 10th	Day	48% 10% 15% 20% 7%	6001
	11th to 20th	Day	48% 8% 12% 22% 10%	5990
	21st to end	Day	29% 7% 16% 28% 19% 1	6341
September	1st to 10th	Day	35% 6% 11% 21% 23% 4	2405
	11th to 20th	Day	37% 5% 11% 26% 19% 2	2310
	21st to end	Day	47% 5% 9% 20% 17% 2	2310
October	1st to 10th	Day	30% 3 8% 23% 33% 3	3462
	11th to 20th	Day	35% 4 11% 25% 19% 6%	3270
	21st to end	Day	32% 3 9% 31% 20% 4	3538
November	1st to 10th	Day	38% 4 10% 27% 18% 4	1956
	11th to 20th	Day	49% 3 9% 19% 16% 3	1890
	21st to end	Day	53% 4 10% 19% 13%	1840
December	1st to 10th	Day	65% 3 9% 20% 4 1	2680
	11th to 20th	Day	61% 4 11% 17% 7%	3289
	21st to end	Day	63% 6% 11% 15% 4	4565
January	1st to 10th	Night	68% 4 9% 14% 4	7636
	11th to 20th	Night	67% 4 7% 13% 9% 1	7680
	21st to end	Night	60% 3 10% 18% 7% 1	8401
February	1st to 10th	Night	58% 4 10% 18% 10%	2730
	11th to 20th	Night	62% 4 8% 16% 9%	2575
	21st to end	Night	58% 5% 9% 16% 10% 3	2076
March	1st to 10th	Night	50% 4 7% 23% 13% 2	5032
	11th to 20th	Night	41% 4 9% 24% 19% 3	5090
	21st to end	Night	50% 5% 8% 21% 14% 2	5588
April	1st to 10th	Night	48% 6% 9% 20% 15% 2	2273
	11th to 20th	Night	42% 6% 12% 20% 14% 6%	2016
	21st to end	Night	45% 6% 10% 21% 16% 2	1890
May	1st to 10th	Night	55% 7% 11% 15% 10% 2	5264
	11th to 20th	Night	43% 9% 14% 21% 12% 1	5235
	21st to end	Night	53% 7% 11% 15% 10% 4	5771
June	1st to 10th	Night	36% 8% 12% 24% 17% 2	1890
	11th to 20th	Night	38% 10% 14% 18% 17% 2	1890
	21st to end	Night	36% 7% 16% 22% 17% 2	1890
July	1st to 10th	Night	41% 8% 10% 23% 16% 2	5235
	11th to 20th	Night	44% 8% 13% 25% 9% 1	5226
	21st to end	Night	44% 8% 12% 19% 16% 2	5606
August	1st to 10th	Night	52% 10% 12% 19% 7% 1	4124
	11th to 20th	Night	50% 6% 11% 18% 14% 1	4122
	21st to end	Night	30% 7% 15% 31% 17% 2	4737
September	1st to 10th	Night	33% 9% 12% 20% 20% 6%	2210
	11th to 20th	Night	32% 6% 12% 23% 23% 3	2310
	21st to end	Night	43% 5% 10% 21% 19% 2	2310
October	1st to 10th	Night	30% 5% 8% 25% 27% 5%	3938
	11th to 20th	Night	33% 4 10% 22% 23% 8%	3936
	21st to end	Night	33% 3 6% 27% 25% 6%	4252
November	1st to 10th	Night	38% 4 11% 21% 20% 5%	2559
	11th to 20th	Night	50% 4 7% 19% 16% 4	2730
	21st to end	Night	52% 4 10% 19% 13% 1	2771
December	1st to 10th	Night	60% 4 10% 20% 5% 1	4720
	11th to 20th	Night	62% 4 11% 16% 7%	5101
	21st to end	Night	62% 5% 10% 15% 7%	6633

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% 24% 13% 3 1	330
	11th to 20th	Day	39% 29% 25% 6% 1	330
	21st to end	Day	36% 27% 28% 7% 2 1	363
February	1st to 10th	Day	35% 19% 35% 7% 4	330
	11th to 20th	Day	47% 24% 22% 6% 1	330
	21st to end	Day	36% 25% 31% 9%	273
March	1st to 10th	Day	33% 20% 26% 18% 4	535
	11th to 20th	Day	29% 24% 29% 13% 4 1	540
	21st to end	Day	33% 18% 29% 16% 4	594
April	1st to 10th	Day	32% 19% 25% 18% 7%	540
	11th to 20th	Day	26% 20% 29% 15% 8% 3	532
	21st to end	Day	28% 19% 26% 18% 7% 2	540
May	1st to 10th	Day	26% 20% 27% 16% 8% 3	543
	11th to 20th	Day	22% 13% 31% 20% 11% 3	567
	21st to end	Day	19% 9% 24% 26% 15% 7%	617
June	1st to 10th	Day	14% 10% 24% 29% 17% 6%	570
	11th to 20th	Day	13% 11% 26% 26% 17% 6%	570
	21st to end	Day	15% 9% 27% 26% 18% 6%	570
July	1st to 10th	Day	14% 6% 19% 27% 20% 15%	565
	11th to 20th	Day	10% 5% 22% 34% 19% 11%	564
	21st to end	Day	19% 6% 18% 28% 21% 9%	620
August	1st to 10th	Day	13% 6% 21% 31% 20% 9%	566
	11th to 20th	Day	13% 8% 21% 28% 20% 9%	559
	21st to end	Day	10% 5% 16% 33% 26% 11%	627
September	1st to 10th	Day	14% 7% 18% 31% 22% 9%	570
	11th to 20th	Day	13% 3 12% 32% 29% 11%	570
	21st to end	Day	22% 9% 24% 24% 16% 5%	570
October	1st to 10th	Day	16% 7% 26% 26% 21% 5%	570
	11th to 20th	Day	19% 13% 29% 21% 13% 4	542
	21st to end	Day	26% 15% 27% 22% 8% 2	583
November	1st to 10th	Day	21% 15% 30% 23% 9% 3	434
	11th to 20th	Day	31% 18% 26% 18% 5% 1	330
	21st to end	Day	29% 22% 28% 18% 2 1	302
December	1st to 10th	Day	35% 19% 29% 13% 4	220
	11th to 20th	Day	32% 20% 29% 13% 5%	275
	21st to end	Day	36% 22% 24% 14% 5%	363
January	1st to 10th	Night	32% 18% 28% 19% 3	840
	11th to 20th	Night	34% 18% 26% 19% 2	840
	21st to end	Night	28% 18% 32% 19% 2	924
February	1st to 10th	Night	29% 15% 29% 25% 2	840
	11th to 20th	Night	34% 19% 28% 18% 1	823
	21st to end	Night	32% 16% 33% 18% 2	692
March	1st to 10th	Night	28% 15% 28% 25% 3	840
	11th to 20th	Night	29% 16% 29% 19% 7% 1	840
	21st to end	Night	26% 17% 30% 22% 5%	924
April	1st to 10th	Night	25% 17% 31% 21% 6%	840
	11th to 20th	Night	19% 13% 33% 25% 10% 1	772
	21st to end	Night	18% 10% 33% 29% 9%	630
May	1st to 10th	Night	21% 9% 29% 28% 12% 1	630
	11th to 20th	Night	19% 7% 27% 31% 14% 1	621
	21st to end	Night	18% 4 22% 30% 23% 3	683
June	1st to 10th	Night	11% 3 21% 38% 25% 2	630
	11th to 20th	Night	11% 4 21% 37% 25% 3	630
	21st to end	Night	14% 5% 17% 40% 23% 3	630
July	1st to 10th	Night	14% 3 15% 32% 31% 5%	615
	11th to 20th	Night	10% 3 14% 35% 34% 4	612
	21st to end	Night	13% 2 14% 36% 30% 5%	690
August	1st to 10th	Night	11% 3 11% 41% 31% 3	627
	11th to 20th	Night	11% 4 12% 37% 30% 5%	624
	21st to end	Night	12% 3 11% 37% 32% 5%	781
September	1st to 10th	Night	12% 4 15% 36% 29% 4	840
	11th to 20th	Night	13% 3 15% 33% 33% 4	840
	21st to end	Night	20% 5% 21% 30% 22% 2	840
October	1st to 10th	Night	14% 5% 19% 32% 25% 3	840
	11th to 20th	Night	19% 8% 25% 31% 15% 2	813
	21st to end	Night	24% 10% 22% 32% 11% 1	880
November	1st to 10th	Night	17% 9% 27% 33% 14%	820
	11th to 20th	Night	27% 14% 26% 24% 8%	840
	21st to end	Night	26% 12% 26% 28% 7% 1	840
December	1st to 10th	Night	32% 16% 27% 21% 4	840
	11th to 20th	Night	26% 18% 27% 25% 4	840
	21st to end	Night	31% 13% 28% 27% 2	924

Page generated at 2026-10-11 05:06:28. Version ac07

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