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 2025-04-26.

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	13% 7% 3 7% 4 4 5% 4 6% 7% 40%	113962
	Night	14% 7% 3 7% 4 4 4 3 5% 7% 42%	114682
Transparency	Day	40% 7% 11% 23% 17% 3	117697
	Night	39% 6% 10% 22% 18% 4	119088
Seeing	Day	17% 10% 23% 24% 18% 8%	15732
	Night	17% 8% 24% 30% 18% 3	25528

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	15% 12% 7% 11% 5% 4 4 3 4 5% 29%	3617
	11th to 20th	Day	17% 8% 4 11% 4 3 4 2 4 5% 38%	3816
	21st to end	Day	20% 9% 4 5% 3 4 4 3 5% 6% 36%	4855
February	1st to 10th	Day	18% 11% 4 8% 5% 5% 4 3 4 6% 35%	2000
	11th to 20th	Day	22% 10% 3 8% 5% 3 4 3 4 6% 33%	1948
	21st to end	Day	20% 9% 3 7% 4 4 4 3 5% 5% 38%	1650
March	1st to 10th	Day	16% 12% 4 8% 5% 5% 4 3 4 5% 35%	4480
	11th to 20th	Day	13% 8% 2 7% 4 4 4 2 4 5% 46%	4786
	21st to end	Day	12% 7% 3 7% 5% 4 4 3 5% 7% 43%	5737
April	1st to 10th	Day	13% 7% 2 5% 5% 4 5% 3 5% 6% 45%	2400
	11th to 20th	Day	14% 7% 3 6% 4 4 4 3 5% 7% 43%	2374
	21st to end	Day	13% 7% 3 7% 5% 5% 5% 4 5% 7% 40%	2392
May	1st to 10th	Day	18% 7% 2 6% 4 4 4 4 6% 8% 34%	4082
	11th to 20th	Day	15% 8% 3 7% 5% 4 4 3 5% 7% 38%	4081
	21st to end	Day	10% 7% 3 7% 5% 4 5% 4 6% 7% 40%	4476
June	1st to 10th	Day	9% 6% 2 6% 4 6% 5% 4 6% 10% 42%	2471
	11th to 20th	Day	4 4 2 5% 4 5% 6% 5% 8% 10% 46%	2660
	21st to end	Day	4 4 2 5% 6% 6% 6% 6% 9% 12% 41%	2660
July	1st to 10th	Day	6% 5% 2 8% 6% 7% 6% 5% 9% 11% 36%	4440
	11th to 20th	Day	7% 6% 2 7% 5% 5% 6% 5% 8% 12% 37%	4327
	21st to end	Day	16% 10% 3 8% 6% 6% 6% 5% 6% 7% 25%	4466
August	1st to 10th	Day	3 3 2 4 4 4 5% 5% 7% 9% 52%	3946
	11th to 20th	Day	6% 4 2 6% 5% 6% 7% 6% 8% 10% 39%	3729
	21st to end	Day	6% 3 1 5% 4 4 4 4 7% 9% 54%	4180
September	1st to 10th	Day	11% 6% 2 6% 4 5% 5% 4 6% 8% 42%	2247
	11th to 20th	Day	12% 6% 2 6% 4 4 4 3 6% 6% 46%	2090
	21st to end	Day	11% 5% 2 5% 4 4 4 4 5% 7% 49%	2090
October	1st to 10th	Day	9% 5% 2 5% 3 3 3 3 4 7% 55%	2090
	11th to 20th	Day	12% 6% 2 5% 3 2 2 3 5% 7% 52%	2057
	21st to end	Day	16% 6% 2 6% 3 4 4 3 4 5% 46%	1882
November	1st to 10th	Day	12% 6% 2 5% 3 2 3 2 4 6% 54%	1762
	11th to 20th	Day	15% 7% 2 5% 3 3 3 4 5% 7% 48%	1800
	21st to end	Day	15% 9% 2 6% 4 4 3 3 5% 5% 45%	1800
December	1st to 10th	Day	17% 7% 2 7% 4 4 4 3 5% 6% 42%	2930
	11th to 20th	Day	21% 9% 4 8% 5% 4 4 3 4 7% 32%	3373
	21st to end	Day	19% 11% 4 8% 5% 5% 5% 4 6% 7% 26%	4268
January	1st to 10th	Night	16% 10% 4 11% 5% 4 4 4 5% 6% 32%	6348
	11th to 20th	Night	18% 10% 3 7% 5% 4 4 4 4 5% 36%	6133
	21st to end	Night	18% 10% 3 7% 4 4 3 3 4 6% 38%	6099
February	1st to 10th	Night	22% 10% 3 8% 4 4 4 3 5% 5% 32%	2400
	11th to 20th	Night	24% 9% 3 6% 5% 3 3 2 5% 4 35%	2338
	21st to end	Night	23% 8% 3 7% 4 3 3 3 5% 5% 34%	1980
March	1st to 10th	Night	20% 11% 3 6% 4 4 4 3 5% 6% 35%	5373
	11th to 20th	Night	11% 6% 2 5% 4 4 4 4 6% 6% 49%	5174
	21st to end	Night	13% 7% 3 7% 5% 4 4 3 6% 7% 41%	5220
April	1st to 10th	Night	12% 6% 2 6% 4 5% 5% 3 5% 6% 46%	2000
	11th to 20th	Night	15% 7% 2 4 3 4 4 3 5% 6% 47%	1975
	21st to end	Night	14% 7% 3 5% 5% 4 4 3 6% 8% 41%	1903
May	1st to 10th	Night	13% 8% 3 7% 4 5% 5% 4 5% 6% 39%	2813
	11th to 20th	Night	12% 7% 3 7% 5% 4 4 3 6% 8% 42%	2812
	21st to end	Night	6% 6% 2 7% 5% 5% 5% 5% 7% 9% 43%	3079
June	1st to 10th	Night	8% 6% 2 7% 4 4 4 4 7% 8% 46%	1703
	11th to 20th	Night	3 3 1 3 4 4 4 4 8% 11% 54%	1520
	21st to end	Night	3 4 2 5% 4 5% 5% 6% 7% 11% 48%	1520
July	1st to 10th	Night	5% 4 2 6% 5% 5% 6% 5% 8% 13% 40%	2530
	11th to 20th	Night	6% 6% 2 5% 4 4 5% 4 6% 11% 47%	2623
	21st to end	Night	11% 10% 4 9% 7% 6% 6% 6% 6% 9% 27%	3087
August	1st to 10th	Night	4 3 1 4 4 4 4 3 6% 9% 60%	2979
	11th to 20th	Night	4 4 1 5% 4 4 5% 5% 8% 12% 48%	3100
	21st to end	Night	4 3 1 4 3 3 5% 4 6% 8% 58%	3476
September	1st to 10th	Night	10% 5% 2 7% 4 4 4 4 5% 6% 49%	1914
	11th to 20th	Night	10% 5% 3 7% 4 4 4 3 6% 7% 48%	2090
	21st to end	Night	11% 5% 2 5% 4 4 4 3 6% 6% 51%	2090
October	1st to 10th	Night	9% 4 2 4 3 3 3 2 4 7% 60%	2090
	11th to 20th	Night	14% 6% 2 6% 3 3 3 2 4 7% 51%	2118
	21st to end	Night	14% 7% 2 5% 3 3 3 3 4 6% 50%	2713
November	1st to 10th	Night	13% 5% 2 5% 4 3 4 3 5% 5% 52%	2536
	11th to 20th	Night	13% 6% 2 6% 3 3 3 3 6% 7% 49%	2600
	21st to end	Night	17% 7% 3 5% 4 3 4 3 5% 6% 45%	2600
December	1st to 10th	Night	18% 10% 3 8% 4 3 4 4 4 5% 37%	4250
	11th to 20th	Night	24% 8% 2 5% 3 3 3 3 3 5% 39%	4822
	21st to end	Night	19% 12% 4 9% 5% 6% 4 3 5% 5% 27%	6674

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	55% 6% 11% 16% 10% 2	3618
	11th to 20th	Day	48% 5% 7% 23% 17% 1	3816
	21st to end	Day	47% 4 8% 22% 16% 4	4855
February	1st to 10th	Day	53% 3 9% 20% 12% 2	2000
	11th to 20th	Day	55% 4 7% 18% 13% 3	1958
	21st to end	Day	48% 4 9% 18% 15% 6%	1650
March	1st to 10th	Day	51% 5% 6% 14% 16% 8%	4480
	11th to 20th	Day	40% 5% 8% 22% 19% 6%	4786
	21st to end	Day	41% 6% 9% 29% 15% 1	5739
April	1st to 10th	Day	38% 6% 10% 23% 19% 3	2400
	11th to 20th	Day	39% 6% 7% 22% 20% 5%	2374
	21st to end	Day	42% 8% 9% 24% 15% 2	2392
May	1st to 10th	Day	44% 10% 12% 21% 12% 1	4120
	11th to 20th	Day	43% 9% 11% 24% 12% 1	4085
	21st to end	Day	38% 11% 11% 20% 20% 1	4489
June	1st to 10th	Day	36% 10% 12% 22% 17% 3	2471
	11th to 20th	Day	28% 11% 17% 22% 19% 3	2660
	21st to end	Day	31% 11% 17% 22% 15% 4	2660
July	1st to 10th	Day	38% 9% 19% 24% 9% 2	4371
	11th to 20th	Day	37% 7% 16% 29% 9% 2	4252
	21st to end	Day	56% 8% 12% 17% 6% 1	4324
August	1st to 10th	Day	25% 8% 14% 33% 19% 1	3933
	11th to 20th	Day	36% 7% 13% 26% 16% 2	3765
	21st to end	Day	26% 8% 11% 32% 21% 2	4179
September	1st to 10th	Day	38% 10% 12% 19% 19% 4	2247
	11th to 20th	Day	38% 6% 11% 23% 20% 2	2090
	21st to end	Day	34% 6% 12% 23% 21% 4	2090
October	1st to 10th	Day	22% 4 6% 18% 41% 9%	3480
	11th to 20th	Day	23% 4 7% 24% 29% 12%	3401
	21st to end	Day	31% 4 7% 24% 27% 8%	3082
November	1st to 10th	Day	32% 4 9% 24% 25% 6%	1762
	11th to 20th	Day	36% 4 8% 23% 23% 6%	1800
	21st to end	Day	41% 4 7% 24% 18% 4	1800
December	1st to 10th	Day	44% 4 7% 25% 19% 1	2930
	11th to 20th	Day	53% 5% 9% 20% 11% 2	3370
	21st to end	Day	54% 6% 12% 21% 6% 1	4268
January	1st to 10th	Night	50% 6% 11% 19% 13% 1	6348
	11th to 20th	Night	48% 7% 5% 18% 18% 3	6133
	21st to end	Night	48% 4 6% 21% 15% 5%	6099
February	1st to 10th	Night	54% 5% 9% 17% 14% 1	2400
	11th to 20th	Night	53% 3 7% 19% 14% 4	2339
	21st to end	Night	52% 5% 7% 15% 16% 4	1980
March	1st to 10th	Night	49% 6% 6% 15% 19% 6%	5373
	11th to 20th	Night	33% 5% 9% 20% 20% 12%	5174
	21st to end	Night	43% 5% 9% 26% 15% 2	5220
April	1st to 10th	Night	37% 6% 11% 23% 20% 3	2000
	11th to 20th	Night	37% 5% 9% 20% 22% 7%	1975
	21st to end	Night	39% 7% 10% 26% 16% 2	1903
May	1st to 10th	Night	42% 10% 13% 22% 12% 2	2840
	11th to 20th	Night	38% 10% 15% 20% 16%	2813
	21st to end	Night	32% 12% 15% 23% 18% 2	3087
June	1st to 10th	Night	35% 8% 12% 25% 16% 4	1703
	11th to 20th	Night	22% 7% 19% 31% 19% 3	1520
	21st to end	Night	27% 10% 17% 27% 15% 4	1520
July	1st to 10th	Night	33% 8% 20% 27% 10% 2	2490
	11th to 20th	Night	30% 7% 18% 33% 9% 3	2575
	21st to end	Night	52% 8% 13% 17% 8% 1	2988
August	1st to 10th	Night	22% 6% 10% 38% 23% 1	2968
	11th to 20th	Night	26% 7% 20% 31% 15% 1	3130
	21st to end	Night	22% 6% 12% 34% 23% 3	3476
September	1st to 10th	Night	34% 8% 12% 22% 19% 5%	1914
	11th to 20th	Night	35% 6% 10% 22% 23% 3	2090
	21st to end	Night	31% 6% 11% 22% 23% 7%	2090
October	1st to 10th	Night	21% 4 6% 18% 40% 11%	3480
	11th to 20th	Night	21% 5% 6% 23% 31% 14%	3513
	21st to end	Night	25% 4 8% 24% 30% 10%	4463
November	1st to 10th	Night	34% 4 8% 23% 24% 7%	2536
	11th to 20th	Night	34% 5% 7% 21% 26% 7%	2600
	21st to end	Night	41% 4 8% 24% 19% 4	2600
December	1st to 10th	Night	49% 6% 6% 17% 20% 2	4250
	11th to 20th	Night	48% 4 7% 21% 18% 2	4824
	21st to end	Night	56% 6% 9% 19% 9% 1	6674

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% 23% 31% 16% 5% 1	300
	11th to 20th	Day	29% 25% 28% 14% 3 1	300
	21st to end	Day	22% 22% 41% 13% 2	330
February	1st to 10th	Day	27% 19% 34% 17% 2 1	300
	11th to 20th	Day	36% 25% 29% 8% 3	300
	21st to end	Day	31% 21% 35% 11% 2	249
March	1st to 10th	Day	27% 21% 32% 15% 4 1	300
	11th to 20th	Day	25% 20% 32% 16% 6%	410
	21st to end	Day	26% 17% 33% 17% 7%	550
April	1st to 10th	Day	23% 14% 30% 24% 8% 1	500
	11th to 20th	Day	21% 14% 30% 23% 11% 2	492
	21st to end	Day	20% 15% 30% 21% 12% 2	480
May	1st to 10th	Day	20% 14% 28% 21% 13% 4	463
	11th to 20th	Day	16% 7% 27% 25% 18% 6%	487
	21st to end	Day	12% 5% 22% 26% 22% 14%	529
June	1st to 10th	Day	12% 5% 19% 23% 25% 15%	491
	11th to 20th	Day	5% 4 18% 29% 31% 14%	680
	21st to end	Day	5% 3 20% 34% 23% 15%	680
July	1st to 10th	Day	9% 3 12% 29% 30% 17%	671
	11th to 20th	Day	9% 3 9% 26% 35% 17%	607
	21st to end	Day	10% 2 11% 27% 30% 19%	532
August	1st to 10th	Day	9% 4 9% 28% 31% 18%	486
	11th to 20th	Day	9% 3 14% 34% 29% 11%	479
	21st to end	Day	12% 2 10% 20% 35% 21%	539
September	1st to 10th	Day	12% 3 11% 28% 31% 15%	490
	11th to 20th	Day	14% 3 10% 28% 29% 17%	490
	21st to end	Day	16% 7% 17% 24% 28% 8%	490
October	1st to 10th	Day	11% 4 21% 28% 27% 9%	490
	11th to 20th	Day	15% 13% 30% 25% 14% 4	457
	21st to end	Day	22% 13% 27% 28% 8% 1	330
November	1st to 10th	Day	19% 10% 29% 26% 14% 2	300
	11th to 20th	Day	15% 21% 33% 24% 7%	300
	21st to end	Day	21% 15% 33% 22% 8% 2	300
December	1st to 10th	Day	27% 17% 28% 22% 5%	300
	11th to 20th	Day	24% 19% 31% 16% 9%	300
	21st to end	Day	27% 19% 32% 18% 5%	330
January	1st to 10th	Night	24% 16% 29% 27% 4	1000
	11th to 20th	Night	28% 15% 30% 22% 4	903
	21st to end	Night	21% 14% 38% 24% 3	880
February	1st to 10th	Night	26% 13% 33% 24% 4	800
	11th to 20th	Night	28% 15% 34% 20% 3	783
	21st to end	Night	28% 16% 33% 22% 1	660
March	1st to 10th	Night	22% 14% 31% 27% 6%	800
	11th to 20th	Night	21% 14% 32% 27% 6% 1	800
	21st to end	Night	21% 11% 32% 28% 7%	775
April	1st to 10th	Night	15% 12% 33% 31% 9%	600
	11th to 20th	Night	20% 9% 32% 28% 11%	593
	21st to end	Night	18% 8% 32% 30% 11% 2	587
May	1st to 10th	Night	12% 6% 33% 30% 18% 1	570
	11th to 20th	Night	11% 4 24% 36% 19% 5%	561
	21st to end	Night	6% 2 17% 38% 31% 6%	617
June	1st to 10th	Night	12% 3 16% 37% 29% 4	570
	11th to 20th	Night	5% 1 11% 39% 37% 7%	570
	21st to end	Night	5% 2 13% 36% 38% 6%	570
July	1st to 10th	Night	9% 3 7% 31% 40% 11%	555
	11th to 20th	Night	8% 2 6% 31% 44% 10%	552
	21st to end	Night	9% 2 7% 30% 43% 8%	624
August	1st to 10th	Night	7% 1 5% 31% 47% 8%	567
	11th to 20th	Night	6% 2 9% 39% 37% 6%	564
	21st to end	Night	8% 2 8% 29% 44% 9%	627
September	1st to 10th	Night	11% 1 11% 33% 39% 6%	584
	11th to 20th	Night	12% 3 13% 30% 37% 6%	760
	21st to end	Night	13% 3 17% 29% 35% 4	760
October	1st to 10th	Night	11% 5% 19% 32% 29% 5%	760
	11th to 20th	Night	18% 7% 22% 34% 18% 1	760
	21st to end	Night	17% 9% 27% 29% 17% 1	836
November	1st to 10th	Night	16% 6% 23% 35% 18% 2	780
	11th to 20th	Night	16% 10% 32% 31% 10% 1	800
	21st to end	Night	20% 10% 27% 32% 10% 1	800
December	1st to 10th	Night	28% 11% 28% 27% 7%	800
	11th to 20th	Night	25% 9% 31% 28% 7% 1	800
	21st to end	Night	28% 12% 28% 26% 5%	960

Page generated at 2025-04-23 08:25:04. Version ac07

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