Hendersonville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hendersonville clear sky chart from 2005-11-06 to 2026-02-01.

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% 41%	127474
	Night	13% 6% 2 6% 4 4 4 4 6% 7% 44%	124558
Transparency	Day	39% 5% 12% 20% 18% 6%	131185
	Night	37% 5% 12% 21% 19% 6%	128916
Seeing	Day	19% 12% 23% 22% 15% 8%	16688
	Night	18% 12% 21% 27% 19% 4	26796

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	11% 5% 2 4 3 3 3 2 4 6% 59%	4146
	11th to 20th	Day	9% 5% 2 3 3 2 3 3 5% 3 62%	4150
	21st to end	Day	17% 5% 2 6% 4 4 3 3 4 5% 46%	4565
February	1st to 10th	Day	14% 7% 2 6% 4 4 5% 3 5% 7% 45%	1887
	11th to 20th	Day	16% 8% 3 5% 4 3 4 3 5% 5% 44%	1948
	21st to end	Day	15% 7% 3 6% 5% 4 4 4 5% 6% 41%	1650
March	1st to 10th	Day	18% 6% 2 7% 4 4 4 3 5% 5% 42%	4843
	11th to 20th	Day	9% 6% 3 6% 4 3 3 2 5% 6% 54%	4980
	21st to end	Day	16% 7% 2 6% 4 3 4 3 5% 6% 45%	5465
April	1st to 10th	Day	12% 6% 2 4 4 4 5% 4 6% 8% 45%	2200
	11th to 20th	Day	12% 6% 2 5% 4 4 4 4 6% 7% 44%	2379
	21st to end	Day	13% 5% 2 5% 4 5% 5% 4 5% 8% 46%	2600
May	1st to 10th	Day	10% 7% 3 8% 6% 6% 7% 5% 7% 9% 33%	5862
	11th to 20th	Day	18% 7% 3 8% 5% 6% 6% 5% 7% 8% 28%	5861
	21st to end	Day	12% 6% 2 6% 5% 5% 5% 5% 7% 9% 38%	6433
June	1st to 10th	Day	10% 6% 3 9% 5% 6% 7% 6% 8% 9% 31%	2600
	11th to 20th	Day	7% 5% 3 7% 6% 6% 7% 6% 9% 11% 33%	2600
	21st to end	Day	9% 4 2 7% 6% 6% 6% 6% 9% 10% 34%	2600
July	1st to 10th	Day	6% 5% 2 8% 7% 7% 7% 6% 8% 11% 34%	5900
	11th to 20th	Day	7% 6% 3 10% 8% 7% 8% 6% 8% 11% 26%	5900
	21st to end	Day	9% 7% 4 10% 9% 8% 9% 6% 8% 9% 21%	6424
August	1st to 10th	Day	16% 6% 3 9% 6% 6% 7% 5% 8% 10% 22%	4234
	11th to 20th	Day	10% 6% 2 7% 6% 6% 6% 6% 8% 11% 30%	4174
	21st to end	Day	8% 4 2 6% 5% 5% 5% 4 6% 8% 46%	4305
September	1st to 10th	Day	11% 6% 3 7% 5% 6% 5% 4 7% 8% 39%	2200
	11th to 20th	Day	17% 7% 2 7% 5% 4 6% 4 7% 8% 34%	2200
	21st to end	Day	17% 6% 2 6% 5% 4 4 4 6% 7% 38%	2200
October	1st to 10th	Day	15% 5% 2 5% 3 3 4 3 4 6% 50%	2162
	11th to 20th	Day	12% 5% 2 3 3 3 3 3 4 5% 58%	2000
	21st to end	Day	14% 5% 2 4 3 3 3 2 4 5% 56%	2200
November	1st to 10th	Day	11% 6% 2 5% 2 3 2 2 5% 6% 56%	1978
	11th to 20th	Day	11% 5% 1 4 3 3 3 3 5% 7% 54%	1890
	21st to end	Day	13% 5% 2 4 3 2 4 3 6% 6% 52%	1890
December	1st to 10th	Day	10% 7% 2 6% 3 4 4 4 4 5% 51%	3020
	11th to 20th	Day	14% 5% 2 5% 4 4 5% 3 6% 7% 45%	3463
	21st to end	Day	17% 7% 2 5% 3 3 3 3 4 7% 47%	4565
January	1st to 10th	Night	12% 4 2 4 3 3 3 3 4 5% 58%	6019
	11th to 20th	Night	8% 5% 2 4 3 3 4 3 5% 5% 59%	6030
	21st to end	Night	16% 6% 2 5% 3 3 3 3 5% 6% 48%	6633
February	1st to 10th	Night	12% 6% 2 5% 4 5% 4 4 5% 6% 48%	2511
	11th to 20th	Night	16% 8% 2 5% 3 3 4 4 5% 5% 45%	2338
	21st to end	Night	14% 6% 2 5% 5% 4 4 5% 5% 6% 44%	1980
March	1st to 10th	Night	17% 7% 2 6% 4 4 5% 4 5% 6% 40%	5008
	11th to 20th	Night	9% 4 2 4 3 4 4 4 6% 7% 54%	4980
	21st to end	Night	15% 6% 3 5% 4 4 5% 3 5% 7% 44%	5467
April	1st to 10th	Night	11% 6% 2 6% 4 3 3 3 5% 8% 48%	2200
	11th to 20th	Night	12% 6% 2 4 4 4 3 3 5% 7% 50%	1984
	21st to end	Night	11% 6% 2 5% 4 3 4 3 5% 6% 52%	1800
May	1st to 10th	Night	11% 7% 2 6% 5% 5% 5% 4 8% 10% 37%	4033
	11th to 20th	Night	19% 8% 2 7% 4 5% 4 3 6% 10% 31%	4032
	21st to end	Night	14% 5% 2 5% 4 4 5% 4 6% 10% 41%	4421
June	1st to 10th	Night	8% 6% 2 7% 6% 6% 6% 5% 9% 11% 33%	1800
	11th to 20th	Night	10% 6% 2 5% 5% 5% 6% 5% 7% 10% 39%	1800
	21st to end	Night	7% 5% 2 5% 6% 5% 6% 5% 8% 11% 40%	1800
July	1st to 10th	Night	6% 6% 3 9% 6% 7% 7% 5% 8% 11% 32%	4058
	11th to 20th	Night	6% 6% 3 8% 6% 6% 7% 6% 10% 12% 29%	4057
	21st to end	Night	10% 9% 3 10% 7% 6% 7% 5% 7% 10% 25%	4427
August	1st to 10th	Night	13% 9% 3 8% 5% 7% 6% 5% 6% 8% 28%	2915
	11th to 20th	Night	11% 9% 3 9% 6% 6% 6% 5% 7% 9% 28%	2875
	21st to end	Night	7% 4 2 7% 5% 5% 5% 5% 6% 9% 45%	3553
September	1st to 10th	Night	12% 7% 2 7% 5% 5% 4 4 6% 9% 39%	2200
	11th to 20th	Night	17% 9% 3 7% 4 5% 4 3 6% 7% 35%	2200
	21st to end	Night	19% 6% 2 5% 4 4 3 3 4 8% 43%	2200
October	1st to 10th	Night	15% 5% 2 5% 3 3 3 3 6% 5% 49%	2236
	11th to 20th	Night	13% 5% 2 5% 3 4 3 3 5% 5% 53%	2400
	21st to end	Night	14% 5% 1 4 2 2 3 2 4 4 57%	2640
November	1st to 10th	Night	13% 5% 2 4 4 4 3 3 4 5% 54%	2536
	11th to 20th	Night	12% 6% 2 4 4 3 3 3 4 6% 55%	2730
	21st to end	Night	12% 5% 2 5% 4 3 4 3 5% 7% 50%	2730
December	1st to 10th	Night	11% 6% 2 5% 3 3 4 3 4 5% 53%	4380
	11th to 20th	Night	13% 8% 2 7% 4 3 4 3 5% 6% 44%	4952
	21st to end	Night	18% 6% 2 5% 3 3 3 3 4 6% 46%	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	29% 3 5% 20% 37% 6%	4147
	11th to 20th	Day	26% 3 7% 15% 39% 11%	4150
	21st to end	Day	40% 3 4 17% 27% 9%	4565
February	1st to 10th	Day	39% 4 9% 23% 20% 5%	1887
	11th to 20th	Day	42% 4 9% 20% 20% 6%	1958
	21st to end	Day	44% 4 7% 16% 21% 8%	1650
March	1st to 10th	Day	44% 3 4 17% 19% 12%	4843
	11th to 20th	Day	32% 3 6% 16% 24% 19%	4980
	21st to end	Day	41% 3 7% 27% 17% 5%	5465
April	1st to 10th	Day	36% 5% 11% 22% 21% 5%	2200
	11th to 20th	Day	38% 4 8% 21% 21% 7%	2379
	21st to end	Day	37% 4 13% 27% 16% 3	2600
May	1st to 10th	Day	46% 5% 16% 20% 11% 1	5897
	11th to 20th	Day	51% 6% 15% 18% 10% 1	5865
	21st to end	Day	41% 5% 14% 21% 16% 3	6447
June	1st to 10th	Day	45% 8% 18% 21% 7% 1	2600
	11th to 20th	Day	39% 8% 21% 19% 11% 2	2600
	21st to end	Day	41% 8% 18% 18% 12% 2	2600
July	1st to 10th	Day	40% 11% 17% 22% 9% 1	5835
	11th to 20th	Day	47% 10% 26% 14% 3	5831
	21st to end	Day	54% 10% 18% 13% 6%	6240
August	1st to 10th	Day	52% 7% 19% 19% 4	4221
	11th to 20th	Day	42% 9% 22% 15% 9% 3	4213
	21st to end	Day	33% 7% 14% 29% 15% 1	4305
September	1st to 10th	Day	41% 7% 14% 20% 16% 3	2200
	11th to 20th	Day	46% 6% 12% 19% 15% 2	2200
	21st to end	Day	44% 5% 11% 20% 15% 5%	2200
October	1st to 10th	Day	27% 5% 7% 21% 30% 10%	3526
	11th to 20th	Day	20% 3 5% 21% 28% 23%	3240
	21st to end	Day	27% 4 7% 24% 23% 16%	3538
November	1st to 10th	Day	30% 3 9% 21% 28% 9%	1978
	11th to 20th	Day	31% 3 7% 24% 27% 8%	1890
	21st to end	Day	32% 4 8% 23% 27% 6%	1890
December	1st to 10th	Day	35% 4 6% 19% 29% 8%	3020
	11th to 20th	Day	37% 3 10% 20% 23% 7%	3460
	21st to end	Day	38% 4 9% 27% 19% 3	4565
January	1st to 10th	Night	30% 3 6% 20% 35% 6%	6019
	11th to 20th	Night	28% 3 5% 18% 35% 11%	6030
	21st to end	Night	37% 3 5% 18% 27% 9%	6633
February	1st to 10th	Night	37% 3 9% 23% 22% 5%	2511
	11th to 20th	Night	42% 4 7% 19% 22% 6%	2339
	21st to end	Night	40% 5% 8% 18% 21% 7%	1980
March	1st to 10th	Night	43% 4 5% 16% 24% 7%	5008
	11th to 20th	Night	27% 4 7% 20% 25% 17%	4980
	21st to end	Night	42% 3 7% 26% 16% 6%	5467
April	1st to 10th	Night	35% 4 11% 23% 23% 4	2200
	11th to 20th	Night	34% 3 10% 25% 22% 6%	1984
	21st to end	Night	34% 3 15% 27% 18% 3	1800
May	1st to 10th	Night	43% 6% 17% 25% 9% 1	4060
	11th to 20th	Night	49% 6% 16% 20% 8%	4033
	21st to end	Night	40% 5% 16% 27% 12% 2	4429
June	1st to 10th	Night	41% 7% 22% 21% 9% 1	1800
	11th to 20th	Night	37% 8% 23% 23% 9% 1	1800
	21st to end	Night	37% 8% 20% 19% 13% 3	1800
July	1st to 10th	Night	42% 11% 19% 22% 6% 1	4015
	11th to 20th	Night	42% 12% 30% 12% 3 1	4006
	21st to end	Night	51% 10% 19% 15% 5%	4297
August	1st to 10th	Night	51% 7% 23% 15% 5%	2904
	11th to 20th	Night	47% 8% 21% 14% 9% 1	2902
	21st to end	Night	34% 7% 16% 32% 10% 1	3553
September	1st to 10th	Night	40% 7% 16% 21% 14% 3	2200
	11th to 20th	Night	48% 6% 12% 18% 15% 2	2200
	21st to end	Night	41% 5% 11% 23% 17% 4	2200
October	1st to 10th	Night	30% 6% 9% 21% 27% 8%	3652
	11th to 20th	Night	22% 2 6% 23% 26% 21%	3899
	21st to end	Night	29% 4 5% 22% 25% 15%	4252
November	1st to 10th	Night	34% 4 8% 21% 24% 9%	2536
	11th to 20th	Night	32% 3 6% 21% 28% 10%	2730
	21st to end	Night	34% 4 7% 24% 26% 6%	2730
December	1st to 10th	Night	33% 3 8% 23% 27% 6%	4380
	11th to 20th	Night	40% 5% 9% 18% 21% 7%	4954
	21st to end	Night	39% 3 11% 22% 22% 3	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	31% 25% 33% 8% 3	330
	11th to 20th	Day	31% 24% 28% 13% 3	330
	21st to end	Day	25% 26% 33% 14% 2	363
February	1st to 10th	Day	23% 25% 37% 13% 2	300
	11th to 20th	Day	39% 26% 26% 8% 1	300
	21st to end	Day	33% 23% 30% 12% 1	249
March	1st to 10th	Day	26% 24% 27% 16% 7%	456
	11th to 20th	Day	27% 21% 28% 18% 5% 1	500
	21st to end	Day	26% 20% 29% 18% 6% 1	550
April	1st to 10th	Day	24% 22% 25% 21% 8% 1	500
	11th to 20th	Day	19% 19% 27% 20% 12% 2	492
	21st to end	Day	21% 11% 29% 22% 13% 4	500
May	1st to 10th	Day	13% 16% 32% 24% 10% 5%	503
	11th to 20th	Day	20% 9% 23% 26% 15% 8%	527
	21st to end	Day	17% 8% 19% 24% 19% 12%	573
June	1st to 10th	Day	12% 8% 20% 30% 19% 12%	530
	11th to 20th	Day	9% 6% 19% 25% 27% 13%	530
	21st to end	Day	10% 4 19% 32% 22% 13%	530
July	1st to 10th	Day	11% 3 8% 26% 32% 20%	525
	11th to 20th	Day	7% 3 9% 26% 33% 22%	524
	21st to end	Day	8% 4 9% 30% 25% 25%	576
August	1st to 10th	Day	20% 5% 12% 26% 18% 19%	526
	11th to 20th	Day	14% 3 12% 28% 26% 17%	519
	21st to end	Day	14% 2 13% 25% 28% 18%	583
September	1st to 10th	Day	13% 4 13% 26% 28% 15%	530
	11th to 20th	Day	19% 5% 14% 24% 26% 13%	530
	21st to end	Day	22% 5% 18% 29% 22% 5%	530
October	1st to 10th	Day	21% 7% 15% 29% 19% 8%	530
	11th to 20th	Day	14% 14% 26% 27% 16% 4	530
	21st to end	Day	21% 12% 25% 26% 13% 3	583
November	1st to 10th	Day	24% 12% 29% 23% 10% 3	456
	11th to 20th	Day	17% 23% 37% 15% 7% 1	330
	21st to end	Day	20% 24% 31% 17% 8% 1	330
December	1st to 10th	Day	27% 24% 34% 14% 2	330
	11th to 20th	Day	24% 15% 38% 17% 7%	330
	21st to end	Day	25% 17% 38% 14% 5% 2	363
January	1st to 10th	Night	23% 22% 27% 22% 6%	840
	11th to 20th	Night	21% 19% 33% 23% 4	840
	21st to end	Night	20% 22% 33% 23% 3	924
February	1st to 10th	Night	19% 18% 31% 28% 4	801
	11th to 20th	Night	25% 22% 32% 19% 2	783
	21st to end	Night	20% 21% 35% 22% 2	660
March	1st to 10th	Night	20% 21% 28% 26% 5%	800
	11th to 20th	Night	23% 17% 30% 22% 7% 1	800
	21st to end	Night	20% 19% 30% 24% 7% 1	880
April	1st to 10th	Night	18% 17% 31% 26% 8%	800
	11th to 20th	Night	19% 15% 28% 26% 12% 1	706
	21st to end	Night	14% 11% 25% 34% 16%	600
May	1st to 10th	Night	14% 10% 24% 33% 18% 1	600
	11th to 20th	Night	19% 8% 16% 32% 22% 3	591
	21st to end	Night	17% 4 12% 27% 32% 8%	650
June	1st to 10th	Night	10% 3 13% 35% 34% 5%	600
	11th to 20th	Night	11% 4 12% 28% 34% 11%	600
	21st to end	Night	7% 2 11% 32% 40% 8%	600
July	1st to 10th	Night	11% 3 5% 24% 45% 11%	585
	11th to 20th	Night	8% 2 4 22% 48% 14%	582
	21st to end	Night	8% 4 5% 27% 44% 12%	657
August	1st to 10th	Night	18% 2 7% 21% 40% 11%	597
	11th to 20th	Night	17% 4 7% 21% 40% 10%	594
	21st to end	Night	14% 4 6% 22% 43% 12%	722
September	1st to 10th	Night	14% 4 8% 28% 38% 8%	800
	11th to 20th	Night	21% 4 8% 25% 35% 7%	800
	21st to end	Night	21% 5% 15% 30% 27% 3	800
October	1st to 10th	Night	18% 8% 15% 26% 26% 7%	800
	11th to 20th	Night	17% 11% 23% 30% 17% 3	800
	21st to end	Night	18% 11% 20% 34% 15% 3	880
November	1st to 10th	Night	18% 10% 20% 33% 17% 3	820
	11th to 20th	Night	17% 14% 25% 32% 10% 1	840
	21st to end	Night	17% 17% 24% 29% 12% 1	840
December	1st to 10th	Night	22% 18% 25% 28% 7%	840
	11th to 20th	Night	19% 13% 29% 32% 6%	840
	21st to end	Night	24% 15% 24% 30% 6% 1	924

Page generated at 2026-01-29 01:21:45. Version ac07

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