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 2024-01-14.

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	13% 6% 2 5% 5% 3 5% 5% 6% 8% 41%	74907
	Night	14% 6% 2 5% 5% 3 4 5% 5% 7% 44%	74864
Transparency	Day	41% 6% 12% 20% 17% 4	74630
	Night	39% 5% 12% 21% 19% 5%	74660
Seeing	Day	19% 12% 22% 23% 16% 9%	13943
	Night	18% 12% 20% 27% 19% 4	24072

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	14% 7% 2 4 3 3 3 4 4 6% 50%	1706
	11th to 20th	Day	15% 7% 3 4 5% 3 4 4 4 4 47%	1647
	21st to end	Day	13% 7% 2 5% 4 3 4 3 4 6% 51%	1782
February	1st to 10th	Day	15% 6% 2 5% 4 3 5% 4 4 7% 44%	1698
	11th to 20th	Day	16% 7% 3 5% 4 2 4 4 5% 5% 44%	1748
	21st to end	Day	16% 8% 3 5% 6% 3 5% 5% 5% 6% 40%	1480
March	1st to 10th	Day	13% 5% 2 5% 4 3 4 4 5% 6% 49%	1940
	11th to 20th	Day	18% 6% 3 6% 5% 3 4 4 5% 7% 38%	1980
	21st to end	Day	17% 6% 2 5% 5% 3 5% 5% 6% 7% 39%	2178
April	1st to 10th	Day	11% 6% 2 3 4 3 5% 5% 7% 8% 45%	1980
	11th to 20th	Day	13% 6% 2 5% 4 3 5% 5% 5% 8% 44%	2137
	21st to end	Day	12% 4 2 5% 5% 4 5% 5% 5% 8% 47%	2340
May	1st to 10th	Day	10% 6% 3 5% 7% 4 5% 6% 5% 8% 41%	2340
	11th to 20th	Day	15% 6% 3 7% 5% 4 5% 7% 6% 8% 34%	2301
	21st to end	Day	13% 6% 2 5% 6% 4 6% 6% 8% 10% 34%	2531
June	1st to 10th	Day	11% 6% 3 7% 6% 5% 8% 7% 8% 9% 31%	2340
	11th to 20th	Day	7% 5% 3 6% 7% 4 7% 7% 8% 10% 34%	2340
	21st to end	Day	9% 4 3 7% 7% 4 7% 7% 8% 10% 33%	2340
July	1st to 10th	Day	10% 6% 3 7% 8% 5% 7% 8% 7% 10% 27%	2340
	11th to 20th	Day	11% 6% 3 7% 8% 5% 7% 8% 8% 11% 26%	2340
	21st to end	Day	9% 5% 3 7% 9% 5% 8% 7% 7% 10% 29%	2547
August	1st to 10th	Day	14% 6% 3 8% 8% 5% 8% 7% 8% 9% 25%	2327
	11th to 20th	Day	14% 6% 2 6% 7% 5% 7% 7% 7% 10% 28%	2303
	21st to end	Day	14% 5% 3 5% 7% 4 6% 7% 8% 9% 32%	2383
September	1st to 10th	Day	12% 5% 4 6% 6% 5% 5% 5% 7% 7% 38%	1980
	11th to 20th	Day	17% 6% 3 5% 6% 3 5% 5% 6% 8% 35%	1980
	21st to end	Day	17% 6% 2 5% 6% 3 5% 4 5% 7% 40%	1980
October	1st to 10th	Day	17% 5% 2 3 4 2 3 4 4 6% 50%	1946
	11th to 20th	Day	13% 5% 2 3 3 2 3 3 4 6% 57%	1800
	21st to end	Day	14% 5% 2 3 4 2 3 3 4 5% 56%	1980
November	1st to 10th	Day	11% 6% 2 4 2 2 2 3 4 6% 58%	1786
	11th to 20th	Day	12% 4 2 4 4 2 3 4 5% 6% 53%	1710
	21st to end	Day	14% 4 2 3 4 2 4 3 5% 7% 51%	1710
December	1st to 10th	Day	15% 8% 2 7% 5% 4 5% 5% 4 5% 40%	1710
	11th to 20th	Day	15% 4 1 4 3 2 4 4 5% 7% 51%	2153
	21st to end	Day	19% 6% 2 4 4 3 4 4 4 7% 44%	3124
January	1st to 10th	Night	16% 5% 2 4 4 2 4 5% 4 6% 49%	2459
	11th to 20th	Night	15% 6% 3 4 4 3 4 4 5% 6% 45%	2391
	21st to end	Night	14% 6% 2 4 4 2 4 4 4 6% 49%	2574
February	1st to 10th	Night	14% 6% 2 4 4 3 5% 4 4 6% 48%	2259
	11th to 20th	Night	16% 7% 2 5% 3 2 4 5% 4 6% 45%	2098
	21st to end	Night	16% 6% 3 5% 5% 3 4 6% 5% 6% 41%	1776
March	1st to 10th	Night	11% 8% 2 5% 4 3 5% 5% 5% 6% 47%	2018
	11th to 20th	Night	16% 6% 3 5% 5% 3 4 6% 5% 7% 41%	1980
	21st to end	Night	15% 6% 3 5% 5% 3 5% 4 4 7% 43%	2178
April	1st to 10th	Night	12% 6% 2 5% 4 3 4 4 4 8% 49%	1980
	11th to 20th	Night	12% 6% 2 4 5% 3 3 4 5% 7% 50%	1786
	21st to end	Night	12% 5% 2 4 4 3 3 4 4 6% 53%	1620
May	1st to 10th	Night	12% 5% 3 5% 5% 4 5% 4 5% 9% 44%	1620
	11th to 20th	Night	14% 6% 3 6% 7% 3 4 4 5% 9% 38%	1592
	21st to end	Night	13% 4 2 5% 5% 3 5% 5% 7% 9% 41%	1744
June	1st to 10th	Night	8% 6% 2 7% 6% 4 6% 7% 9% 12% 33%	1620
	11th to 20th	Night	10% 5% 2 5% 5% 3 6% 6% 7% 10% 41%	1620
	21st to end	Night	7% 5% 2 5% 6% 4 6% 6% 8% 11% 39%	1620
July	1st to 10th	Night	9% 5% 3 7% 7% 5% 7% 7% 8% 11% 30%	1620
	11th to 20th	Night	7% 5% 4 6% 6% 5% 6% 6% 10% 12% 33%	1620
	21st to end	Night	7% 5% 2 6% 8% 4 7% 8% 9% 11% 33%	1771
August	1st to 10th	Night	13% 5% 2 5% 6% 5% 7% 6% 7% 9% 35%	1611
	11th to 20th	Night	13% 7% 3 6% 6% 4 6% 7% 6% 9% 34%	1598
	21st to end	Night	11% 6% 2 7% 7% 4 5% 7% 7% 9% 35%	1949
September	1st to 10th	Night	12% 6% 2 6% 6% 4 4 5% 6% 10% 39%	1980
	11th to 20th	Night	17% 7% 3 6% 5% 4 4 4 6% 7% 37%	1980
	21st to end	Night	18% 5% 1 4 4 2 3 4 4 8% 45%	1980
October	1st to 10th	Night	17% 5% 2 4 4 2 3 3 5% 5% 50%	2012
	11th to 20th	Night	14% 5% 2 4 3 3 4 3 4 6% 51%	2160
	21st to end	Night	14% 4 1 3 3 2 3 3 4 4 58%	2376
November	1st to 10th	Night	14% 4 2 3 4 2 3 4 4 4 55%	2288
	11th to 20th	Night	13% 5% 2 4 4 2 3 3 3 6% 54%	2470
	21st to end	Night	14% 5% 2 4 4 2 4 4 5% 7% 49%	2470
December	1st to 10th	Night	16% 7% 3 5% 5% 3 5% 5% 5% 6% 42%	2470
	11th to 20th	Night	14% 5% 2 4 4 2 3 4 4 6% 51%	3042
	21st to end	Night	21% 6% 2 4 4 3 4 5% 5% 7% 40%	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	36% 4 9% 24% 21% 6%	1707
	11th to 20th	Day	41% 4 8% 18% 23% 6%	1647
	21st to end	Day	36% 3 6% 24% 24% 8%	1782
February	1st to 10th	Day	41% 4 9% 22% 20% 6%	1698
	11th to 20th	Day	42% 4 9% 21% 19% 6%	1758
	21st to end	Day	45% 4 8% 17% 18% 9%	1480
March	1st to 10th	Day	36% 3 8% 23% 23% 8%	1940
	11th to 20th	Day	46% 4 11% 17% 17% 6%	1980
	21st to end	Day	44% 4 12% 21% 15% 3	2178
April	1st to 10th	Day	35% 5% 11% 23% 21% 5%	1980
	11th to 20th	Day	39% 4 8% 20% 22% 7%	2137
	21st to end	Day	36% 4 13% 27% 17% 3	2340
May	1st to 10th	Day	40% 6% 14% 22% 15% 3	2340
	11th to 20th	Day	46% 8% 14% 18% 11% 2	2305
	21st to end	Day	43% 6% 16% 24% 11% 1	2531
June	1st to 10th	Day	45% 8% 17% 21% 7% 1	2340
	11th to 20th	Day	40% 8% 20% 19% 11% 2	2340
	21st to end	Day	43% 8% 16% 18% 12% 2	2340
July	1st to 10th	Day	48% 9% 17% 15% 9% 2	2275
	11th to 20th	Day	47% 9% 21% 14% 8% 1	2271
	21st to end	Day	45% 9% 19% 18% 8% 1	2405
August	1st to 10th	Day	51% 9% 17% 18% 5%	2314
	11th to 20th	Day	48% 10% 18% 16% 8% 1	2303
	21st to end	Day	44% 9% 18% 19% 8% 2	2383
September	1st to 10th	Day	42% 7% 13% 20% 15% 3	1980
	11th to 20th	Day	46% 6% 11% 19% 16% 3	1980
	21st to end	Day	43% 4 9% 21% 17% 6%	1980
October	1st to 10th	Day	36% 4 9% 21% 25% 5%	1946
	11th to 20th	Day	30% 4 8% 26% 23% 9%	1800
	21st to end	Day	32% 3 6% 22% 27% 10%	1980
November	1st to 10th	Day	29% 2 8% 21% 30% 9%	1786
	11th to 20th	Day	32% 3 6% 23% 28% 8%	1710
	21st to end	Day	33% 3 8% 23% 27% 6%	1710
December	1st to 10th	Day	46% 5% 6% 21% 16% 5%	1710
	11th to 20th	Day	34% 2 8% 20% 28% 9%	2150
	21st to end	Day	40% 4 6% 23% 23% 4	3124
January	1st to 10th	Night	37% 4 10% 20% 24% 6%	2459
	11th to 20th	Night	39% 5% 9% 18% 24% 5%	2391
	21st to end	Night	36% 4 5% 23% 27% 5%	2574
February	1st to 10th	Night	38% 3 10% 22% 21% 6%	2259
	11th to 20th	Night	41% 4 7% 20% 22% 6%	2099
	21st to end	Night	43% 5% 9% 17% 20% 6%	1776
March	1st to 10th	Night	37% 5% 9% 18% 23% 9%	2018
	11th to 20th	Night	41% 5% 11% 19% 19% 5%	1980
	21st to end	Night	42% 4 10% 24% 17% 2	2178
April	1st to 10th	Night	35% 4 11% 23% 24% 4	1980
	11th to 20th	Night	35% 3 9% 25% 21% 6%	1786
	21st to end	Night	33% 3 14% 27% 19% 3	1620
May	1st to 10th	Night	37% 5% 15% 25% 16% 2	1620
	11th to 20th	Night	44% 7% 16% 20% 13% 1	1593
	21st to end	Night	39% 6% 17% 28% 9% 1	1745
June	1st to 10th	Night	40% 8% 22% 22% 8% 1	1620
	11th to 20th	Night	37% 7% 24% 22% 9% 1	1620
	21st to end	Night	37% 9% 20% 18% 12% 3	1620
July	1st to 10th	Night	45% 9% 20% 15% 9% 1	1575
	11th to 20th	Night	39% 11% 24% 17% 7% 2	1566
	21st to end	Night	39% 12% 22% 20% 7% 1	1672
August	1st to 10th	Night	44% 9% 21% 18% 8%	1600
	11th to 20th	Night	45% 10% 19% 15% 10% 1	1598
	21st to end	Night	43% 8% 19% 21% 7% 2	1949
September	1st to 10th	Night	39% 7% 15% 22% 13% 3	1980
	11th to 20th	Night	46% 6% 12% 19% 15% 2	1980
	21st to end	Night	39% 4 9% 24% 19% 4	1980
October	1st to 10th	Night	37% 4 9% 21% 24% 4	2012
	11th to 20th	Night	35% 3 8% 25% 21% 7%	2160
	21st to end	Night	30% 3 6% 23% 28% 10%	2376
November	1st to 10th	Night	33% 4 7% 21% 25% 10%	2288
	11th to 20th	Night	34% 3 6% 20% 27% 11%	2470
	21st to end	Night	35% 4 6% 23% 26% 6%	2470
December	1st to 10th	Night	43% 4 9% 20% 19% 5%	2470
	11th to 20th	Night	34% 4 9% 18% 29% 7%	3044
	21st to end	Night	44% 4 8% 19% 22% 4	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	27% 26% 33% 10% 3	270
	11th to 20th	Day	27% 22% 30% 17% 4	249
	21st to end	Day	22% 27% 34% 14% 2	264
February	1st to 10th	Day	26% 25% 35% 11% 3	240
	11th to 20th	Day	38% 28% 27% 7%	240
	21st to end	Day	33% 23% 31% 11% 2	198
March	1st to 10th	Day	22% 27% 29% 16% 7%	380
	11th to 20th	Day	28% 20% 27% 18% 5% 1	420
	21st to end	Day	26% 19% 29% 20% 7% 1	462
April	1st to 10th	Day	21% 20% 25% 22% 10%	420
	11th to 20th	Day	18% 20% 25% 21% 14% 1	412
	21st to end	Day	21% 13% 28% 21% 12% 5%	420
May	1st to 10th	Day	13% 17% 31% 23% 11% 6%	423
	11th to 20th	Day	19% 8% 20% 28% 16% 9%	447
	21st to end	Day	17% 6% 16% 25% 22% 14%	485
June	1st to 10th	Day	13% 7% 16% 30% 21% 13%	450
	11th to 20th	Day	11% 6% 18% 23% 27% 14%	450
	21st to end	Day	12% 4 19% 31% 21% 14%	450
July	1st to 10th	Day	12% 3 7% 26% 31% 21%	445
	11th to 20th	Day	8% 3 9% 25% 31% 23%	444
	21st to end	Day	8% 2 8% 29% 26% 27%	488
August	1st to 10th	Day	19% 4 11% 26% 18% 22%	446
	11th to 20th	Day	15% 2 9% 28% 27% 20%	439
	21st to end	Day	16% 2 12% 24% 28% 19%	495
September	1st to 10th	Day	13% 4 11% 25% 31% 17%	450
	11th to 20th	Day	19% 4 11% 25% 28% 13%	450
	21st to end	Day	22% 4 16% 30% 23% 6%	450
October	1st to 10th	Day	24% 7% 14% 27% 19% 9%	450
	11th to 20th	Day	14% 14% 26% 26% 16% 4	450
	21st to end	Day	21% 11% 24% 27% 14% 3	495
November	1st to 10th	Day	23% 12% 26% 24% 11% 4	384
	11th to 20th	Day	18% 21% 36% 17% 7% 1	270
	21st to end	Day	17% 21% 33% 19% 9% 1	270
December	1st to 10th	Day	28% 23% 31% 16% 3	270
	11th to 20th	Day	21% 16% 37% 18% 7%	270
	21st to end	Day	24% 18% 37% 14% 5% 2	297
January	1st to 10th	Night	21% 23% 27% 22% 7%	760
	11th to 20th	Night	20% 18% 31% 25% 5%	736
	21st to end	Night	19% 22% 31% 25% 3	792
February	1st to 10th	Night	20% 18% 31% 27% 5%	720
	11th to 20th	Night	24% 23% 33% 19% 2	703
	21st to end	Night	20% 21% 33% 23% 2	592
March	1st to 10th	Night	18% 21% 29% 27% 4	720
	11th to 20th	Night	23% 18% 29% 22% 7% 1	720
	21st to end	Night	19% 19% 29% 25% 7% 1	792
April	1st to 10th	Night	17% 17% 31% 26% 9%	720
	11th to 20th	Night	19% 15% 26% 26% 13% 1	636
	21st to end	Night	15% 11% 25% 33% 16%	540
May	1st to 10th	Night	14% 11% 23% 34% 17% 1	540
	11th to 20th	Night	18% 8% 16% 32% 23% 3	531
	21st to end	Night	16% 2 11% 27% 36% 9%	584
June	1st to 10th	Night	10% 2 12% 34% 36% 5%	540
	11th to 20th	Night	12% 4 12% 26% 34% 12%	540
	21st to end	Night	8% 2 11% 32% 39% 8%	540
July	1st to 10th	Night	12% 3 5% 24% 43% 13%	525
	11th to 20th	Night	9% 2 4 23% 47% 15%	522
	21st to end	Night	8% 3 6% 26% 45% 13%	591
August	1st to 10th	Night	16% 1 7% 21% 43% 12%	537
	11th to 20th	Night	16% 2 6% 21% 43% 11%	534
	21st to end	Night	14% 3 5% 23% 43% 12%	649
September	1st to 10th	Night	14% 4 8% 26% 40% 9%	720
	11th to 20th	Night	21% 4 8% 25% 36% 7%	720
	21st to end	Night	20% 4 15% 30% 27% 4	720
October	1st to 10th	Night	19% 8% 16% 23% 26% 8%	720
	11th to 20th	Night	18% 10% 23% 28% 18% 3	720
	21st to end	Night	17% 10% 20% 34% 15% 3	792
November	1st to 10th	Night	18% 10% 19% 33% 18% 3	740
	11th to 20th	Night	17% 14% 23% 33% 11% 1	760
	21st to end	Night	17% 16% 23% 30% 13% 1	760
December	1st to 10th	Night	22% 18% 22% 30% 8%	760
	11th to 20th	Night	18% 13% 29% 32% 7% 1	760
	21st to end	Night	25% 15% 23% 30% 6% 1	836

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