Charles Towne Landing State Historic Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Charles Towne Landing State Historic Site clear sky chart from 2005-11-06 to 2024-01-13.

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	11% 5% 2 5% 5% 3 5% 5% 6% 9% 42%	74950
	Night	11% 6% 2 5% 5% 3 5% 5% 6% 8% 44%	74798
Transparency	Day	37% 9% 15% 19% 15% 5%	74673
	Night	36% 9% 14% 19% 17% 6%	74594
Seeing	Day	12% 6% 22% 28% 24% 9%	14415
	Night	12% 5% 22% 31% 24% 5%	24567

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	12% 6% 3 5% 5% 3 3 4 5% 9% 44%	1706
	11th to 20th	Day	12% 5% 3 5% 5% 3 4 5% 5% 9% 44%	1638
	21st to end	Day	15% 7% 3 6% 5% 2 4 3 4 5% 46%	1782
February	1st to 10th	Day	15% 6% 2 5% 5% 3 5% 5% 6% 7% 41%	1620
	11th to 20th	Day	17% 6% 2 5% 4 2 4 3 4 5% 47%	1712
	21st to end	Day	14% 7% 3 5% 5% 3 4 4 5% 5% 46%	1620
March	1st to 10th	Day	12% 5% 2 5% 4 2 4 3 5% 7% 51%	1980
	11th to 20th	Day	12% 4 2 5% 5% 3 5% 5% 6% 8% 46%	1980
	21st to end	Day	11% 6% 2 5% 5% 3 5% 5% 5% 8% 45%	2178
April	1st to 10th	Day	8% 4 2 4 4 3 4 5% 5% 7% 54%	2001
	11th to 20th	Day	10% 4 2 4 4 3 5% 4 6% 8% 51%	2134
	21st to end	Day	5% 4 2 3 3 2 4 5% 6% 10% 56%	2160
May	1st to 10th	Day	7% 3 2 4 4 4 5% 5% 6% 9% 50%	2300
	11th to 20th	Day	10% 5% 2 5% 4 3 5% 6% 7% 9% 44%	2301
	21st to end	Day	9% 6% 2 6% 5% 3 6% 6% 8% 12% 37%	2531
June	1st to 10th	Day	8% 6% 3 6% 7% 4 8% 8% 8% 10% 32%	2340
	11th to 20th	Day	7% 4 2 4 6% 4 6% 7% 9% 12% 37%	2340
	21st to end	Day	6% 4 3 6% 6% 5% 8% 7% 9% 12% 34%	2340
July	1st to 10th	Day	8% 5% 3 5% 6% 4 7% 9% 8% 13% 32%	2340
	11th to 20th	Day	8% 6% 3 6% 6% 4 8% 7% 8% 12% 32%	2340
	21st to end	Day	7% 4 3 6% 6% 5% 8% 8% 8% 12% 32%	2547
August	1st to 10th	Day	8% 5% 2 6% 8% 4 7% 8% 11% 13% 27%	2327
	11th to 20th	Day	7% 6% 3 7% 8% 5% 8% 7% 9% 11% 30%	2236
	21st to end	Day	13% 6% 3 8% 8% 6% 7% 7% 8% 9% 26%	2376
September	1st to 10th	Day	11% 5% 2 6% 6% 4 6% 8% 6% 11% 35%	2061
	11th to 20th	Day	11% 8% 2 6% 7% 4 6% 7% 7% 8% 34%	1980
	21st to end	Day	14% 7% 3 6% 5% 4 5% 5% 6% 9% 37%	1980
October	1st to 10th	Day	12% 6% 2 5% 5% 3 4 4 5% 5% 48%	1832
	11th to 20th	Day	8% 4 2 4 4 2 3 4 5% 8% 56%	1800
	21st to end	Day	9% 5% 2 4 4 3 3 3 4 6% 55%	1980
November	1st to 10th	Day	10% 5% 2 3 3 2 3 4 5% 6% 55%	1857
	11th to 20th	Day	12% 7% 3 5% 5% 3 4 4 4 6% 49%	1900
	21st to end	Day	13% 5% 2 4 4 3 3 4 5% 7% 52%	1744
December	1st to 10th	Day	13% 6% 2 6% 4 3 5% 6% 5% 7% 42%	1710
	11th to 20th	Day	15% 5% 2 4 3 2 3 3 4 6% 54%	2153
	21st to end	Day	17% 9% 3 5% 4 2 4 4 5% 5% 43%	3124
January	1st to 10th	Night	11% 6% 3 6% 5% 4 5% 5% 6% 6% 45%	2459
	11th to 20th	Night	12% 6% 2 5% 5% 3 4 4 5% 7% 46%	2378
	21st to end	Night	15% 7% 3 5% 5% 2 3 5% 4 6% 44%	2574
February	1st to 10th	Night	15% 7% 2 6% 5% 2 4 4 6% 6% 43%	2340
	11th to 20th	Night	16% 7% 2 5% 4 3 5% 4 5% 6% 44%	2130
	21st to end	Night	12% 8% 3 7% 6% 3 4 4 5% 7% 42%	1633
March	1st to 10th	Night	9% 5% 2 5% 5% 2 4 5% 4 7% 50%	1980
	11th to 20th	Night	11% 6% 2 6% 5% 3 3 4 6% 8% 45%	1980
	21st to end	Night	11% 6% 2 5% 5% 3 5% 4 6% 8% 46%	2178
April	1st to 10th	Night	9% 5% 2 5% 4 3 4 4 5% 7% 52%	1958
	11th to 20th	Night	12% 3 1 5% 4 3 4 5% 5% 8% 51%	1775
	21st to end	Night	7% 4 2 4 4 3 4 4 5% 9% 55%	1800
May	1st to 10th	Night	6% 3 3 4 3 3 5% 5% 6% 8% 53%	1674
	11th to 20th	Night	9% 4 3 4 4 3 3 5% 6% 10% 47%	1592
	21st to end	Night	8% 4 2 5% 5% 4 5% 6% 8% 10% 43%	1744
June	1st to 10th	Night	9% 5% 2 7% 5% 4 6% 6% 8% 12% 35%	1620
	11th to 20th	Night	6% 4 2 5% 6% 3 6% 6% 9% 13% 39%	1620
	21st to end	Night	5% 5% 3 5% 7% 5% 6% 8% 8% 14% 35%	1620
July	1st to 10th	Night	6% 5% 3 5% 5% 4 6% 8% 9% 12% 37%	1620
	11th to 20th	Night	7% 5% 3 6% 6% 4 6% 8% 8% 13% 34%	1620
	21st to end	Night	6% 4 3 5% 6% 3 6% 6% 8% 13% 39%	1771
August	1st to 10th	Night	7% 5% 2 6% 5% 3 6% 8% 11% 14% 32%	1611
	11th to 20th	Night	7% 6% 2 7% 7% 5% 7% 8% 7% 13% 30%	1645
	21st to end	Night	10% 7% 2 6% 8% 5% 6% 7% 7% 12% 31%	1980
September	1st to 10th	Night	9% 5% 2 7% 6% 5% 5% 7% 7% 10% 37%	1895
	11th to 20th	Night	9% 6% 3 6% 6% 4 5% 6% 7% 9% 39%	1980
	21st to end	Night	14% 6% 3 6% 5% 3 4 5% 7% 9% 38%	1980
October	1st to 10th	Night	12% 5% 2 4 5% 2 4 4 5% 8% 48%	2128
	11th to 20th	Night	9% 3 2 3 4 2 3 5% 6% 7% 56%	2160
	21st to end	Night	10% 5% 2 5% 3 2 3 3 6% 6% 55%	2376
November	1st to 10th	Night	10% 5% 2 4 3 2 4 3 4 6% 56%	2221
	11th to 20th	Night	14% 6% 3 4 4 2 3 3 4 6% 51%	2280
	21st to end	Night	11% 6% 2 6% 4 3 4 5% 6% 8% 46%	2432
December	1st to 10th	Night	14% 6% 3 5% 5% 3 6% 5% 6% 6% 41%	2470
	11th to 20th	Night	16% 6% 2 5% 3 2 3 4 4 6% 49%	3042
	21st to end	Night	18% 7% 2 5% 5% 3 4 4 4 6% 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	37% 7% 12% 20% 20% 5%	1707
	11th to 20th	Day	37% 6% 11% 18% 21% 7%	1638
	21st to end	Day	41% 4 7% 20% 22% 7%	1782
February	1st to 10th	Day	42% 6% 10% 19% 17% 6%	1620
	11th to 20th	Day	40% 5% 9% 16% 22% 8%	1722
	21st to end	Day	40% 6% 10% 19% 16% 10%	1620
March	1st to 10th	Day	33% 6% 9% 20% 19% 12%	1980
	11th to 20th	Day	36% 8% 15% 18% 14% 8%	1980
	21st to end	Day	37% 7% 13% 20% 18% 5%	2178
April	1st to 10th	Day	29% 6% 14% 21% 21% 8%	2001
	11th to 20th	Day	30% 6% 13% 24% 18% 9%	2134
	21st to end	Day	23% 7% 15% 30% 20% 5%	2160
May	1st to 10th	Day	29% 8% 14% 25% 18% 5%	2300
	11th to 20th	Day	33% 10% 20% 22% 14% 1	2305
	21st to end	Day	36% 12% 17% 22% 12%	2531
June	1st to 10th	Day	42% 13% 18% 17% 10%	2340
	11th to 20th	Day	34% 12% 23% 24% 7%	2340
	21st to end	Day	36% 15% 23% 18% 7% 1	2340
July	1st to 10th	Day	37% 15% 22% 18% 7% 1	2275
	11th to 20th	Day	40% 14% 26% 15% 6%	2271
	21st to end	Day	36% 16% 26% 19% 2 1	2405
August	1st to 10th	Day	39% 17% 23% 18% 3	2314
	11th to 20th	Day	43% 16% 22% 16% 3	2236
	21st to end	Day	49% 13% 19% 15% 5%	2376
September	1st to 10th	Day	40% 13% 18% 15% 13% 2	2061
	11th to 20th	Day	42% 12% 15% 17% 11% 3	1980
	21st to end	Day	42% 8% 14% 18% 13% 3	1980
October	1st to 10th	Day	37% 6% 10% 18% 23% 6%	1832
	11th to 20th	Day	27% 6% 11% 22% 25% 9%	1800
	21st to end	Day	31% 4 8% 18% 28% 11%	1980
November	1st to 10th	Day	29% 6% 11% 17% 26% 11%	1857
	11th to 20th	Day	37% 5% 8% 18% 21% 11%	1900
	21st to end	Day	33% 5% 10% 23% 22% 7%	1744
December	1st to 10th	Day	40% 8% 11% 20% 13% 8%	1710
	11th to 20th	Day	33% 4 8% 22% 27% 6%	2150
	21st to end	Day	42% 6% 8% 18% 23% 4	3124
January	1st to 10th	Night	38% 6% 10% 18% 20% 8%	2459
	11th to 20th	Night	38% 5% 9% 18% 22% 7%	2378
	21st to end	Night	41% 4 7% 16% 23% 8%	2574
February	1st to 10th	Night	41% 5% 9% 19% 18% 8%	2340
	11th to 20th	Night	41% 6% 9% 14% 19% 10%	2131
	21st to end	Night	43% 5% 10% 18% 13% 11%	1633
March	1st to 10th	Night	33% 6% 11% 19% 19% 12%	1980
	11th to 20th	Night	37% 8% 14% 19% 15% 8%	1980
	21st to end	Night	35% 8% 14% 19% 17% 7%	2178
April	1st to 10th	Night	32% 7% 13% 19% 20% 9%	1958
	11th to 20th	Night	33% 6% 9% 22% 20% 11%	1775
	21st to end	Night	26% 7% 14% 26% 22% 5%	1800
May	1st to 10th	Night	27% 8% 14% 25% 20% 5%	1674
	11th to 20th	Night	31% 11% 18% 23% 15% 1	1593
	21st to end	Night	33% 12% 16% 25% 13% 1	1745
June	1st to 10th	Night	38% 12% 21% 20% 9%	1620
	11th to 20th	Night	32% 13% 23% 25% 7% 1	1620
	21st to end	Night	35% 14% 26% 20% 4 1	1620
July	1st to 10th	Night	32% 16% 25% 21% 6% 1	1575
	11th to 20th	Night	37% 16% 26% 15% 6% 1	1566
	21st to end	Night	31% 16% 27% 24% 3	1672
August	1st to 10th	Night	34% 19% 25% 18% 4	1600
	11th to 20th	Night	42% 16% 20% 19% 3	1645
	21st to end	Night	44% 14% 20% 18% 4 1	1980
September	1st to 10th	Night	40% 13% 17% 18% 11% 2	1895
	11th to 20th	Night	39% 11% 17% 18% 13% 2	1980
	21st to end	Night	41% 9% 14% 20% 13% 3	1980
October	1st to 10th	Night	35% 7% 11% 20% 21% 5%	2128
	11th to 20th	Night	26% 8% 11% 22% 25% 9%	2160
	21st to end	Night	29% 5% 9% 18% 25% 13%	2376
November	1st to 10th	Night	30% 5% 9% 18% 25% 12%	2221
	11th to 20th	Night	35% 5% 8% 18% 22% 12%	2280
	21st to end	Night	36% 5% 10% 18% 21% 10%	2432
December	1st to 10th	Night	41% 8% 13% 15% 17% 6%	2470
	11th to 20th	Night	37% 5% 9% 16% 27% 6%	3044
	21st to end	Night	43% 6% 7% 19% 20% 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	13% 10% 46% 27% 4	270
	11th to 20th	Day	11% 9% 39% 26% 14% 2	246
	21st to end	Day	20% 16% 39% 21% 3 1	264
February	1st to 10th	Day	17% 14% 35% 25% 9%	240
	11th to 20th	Day	24% 10% 39% 22% 4	240
	21st to end	Day	12% 9% 45% 26% 8% 1	338
March	1st to 10th	Day	12% 13% 35% 29% 12%	420
	11th to 20th	Day	15% 9% 37% 30% 8% 2	420
	21st to end	Day	12% 9% 39% 27% 11% 2	462
April	1st to 10th	Day	12% 12% 34% 28% 13% 2	420
	11th to 20th	Day	8% 11% 31% 24% 19% 7%	412
	21st to end	Day	5% 7% 28% 31% 21% 8%	420
May	1st to 10th	Day	4 9% 33% 30% 17% 7%	423
	11th to 20th	Day	11% 3 20% 31% 25% 10%	447
	21st to end	Day	11% 3 11% 33% 28% 14%	485
June	1st to 10th	Day	9% 2 17% 33% 26% 12%	450
	11th to 20th	Day	9% 3 12% 26% 30% 20%	450
	21st to end	Day	7% 2 12% 31% 34% 15%	450
July	1st to 10th	Day	6% 2 5% 24% 44% 18%	445
	11th to 20th	Day	7% 1 5% 22% 44% 20%	444
	21st to end	Day	6% 2 6% 33% 40% 13%	488
August	1st to 10th	Day	10% 1 9% 26% 36% 17%	446
	11th to 20th	Day	6% 2 5% 23% 42% 21%	439
	21st to end	Day	13% 2 9% 22% 36% 19%	495
September	1st to 10th	Day	10% 4 5% 25% 40% 17%	450
	11th to 20th	Day	14% 3 11% 32% 31% 10%	450
	21st to end	Day	16% 1 10% 30% 29% 13%	450
October	1st to 10th	Day	18% 3 21% 29% 19% 10%	450
	11th to 20th	Day	10% 2 20% 30% 26% 10%	450
	21st to end	Day	11% 5% 22% 31% 27% 5%	495
November	1st to 10th	Day	14% 5% 26% 28% 21% 5%	455
	11th to 20th	Day	16% 5% 34% 27% 16% 2	460
	21st to end	Day	12% 8% 29% 33% 16% 2	304
December	1st to 10th	Day	18% 8% 30% 32% 12% 1	270
	11th to 20th	Day	17% 10% 34% 26% 10% 3	270
	21st to end	Day	22% 10% 30% 27% 11% 1	297
January	1st to 10th	Night	13% 10% 36% 34% 7%	760
	11th to 20th	Night	14% 10% 31% 32% 12%	732
	21st to end	Night	17% 9% 40% 29% 5%	792
February	1st to 10th	Night	17% 9% 32% 32% 10%	720
	11th to 20th	Night	17% 10% 35% 32% 6%	703
	21st to end	Night	16% 8% 34% 34% 8% 1	592
March	1st to 10th	Night	10% 8% 34% 36% 11%	720
	11th to 20th	Night	13% 8% 30% 36% 12% 1	720
	21st to end	Night	11% 7% 34% 32% 15% 1	792
April	1st to 10th	Night	11% 10% 29% 34% 16% 1	720
	11th to 20th	Night	12% 8% 24% 31% 22% 3	711
	21st to end	Night	9% 5% 25% 36% 23% 1	720
May	1st to 10th	Night	8% 5% 24% 36% 24% 4	594
	11th to 20th	Night	10% 3 19% 31% 31% 7%	531
	21st to end	Night	9% 1 11% 27% 40% 13%	584
June	1st to 10th	Night	10% 3 11% 36% 32% 8%	540
	11th to 20th	Night	6% 1 9% 24% 42% 16%	540
	21st to end	Night	6% 1 9% 30% 41% 12%	540
July	1st to 10th	Night	8% 2 6% 24% 48% 12%	525
	11th to 20th	Night	9% 1 4 21% 49% 16%	522
	21st to end	Night	5% 2 3 31% 47% 11%	591
August	1st to 10th	Night	10% 2 4 23% 47% 14%	537
	11th to 20th	Night	9% 2 6% 24% 44% 14%	581
	21st to end	Night	11% 2 7% 24% 40% 17%	792
September	1st to 10th	Night	10% 2 8% 26% 43% 11%	720
	11th to 20th	Night	10% 3 8% 31% 38% 10%	720
	21st to end	Night	16% 2 10% 27% 35% 10%	720
October	1st to 10th	Night	14% 2 17% 31% 28% 8%	720
	11th to 20th	Night	10% 4 21% 32% 27% 6%	720
	21st to end	Night	11% 5% 22% 31% 26% 5%	792
November	1st to 10th	Night	12% 5% 23% 35% 22% 3	740
	11th to 20th	Night	15% 8% 24% 35% 16% 2	760
	21st to end	Night	12% 9% 24% 34% 18% 3	760
December	1st to 10th	Night	16% 6% 30% 33% 14% 1	760
	11th to 20th	Night	18% 7% 28% 29% 17% 1	760
	21st to end	Night	20% 10% 29% 29% 11% 1	836

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