Kiawah Island Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Kiawah Island Observatory clear sky chart from 2005-11-06 to 2024-11-01.

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	10% 6% 2 6% 4 4 5% 4 6% 9% 44%	101072
	Night	11% 6% 2 6% 4 4 5% 4 6% 8% 43%	97830
Transparency	Day	35% 10% 17% 20% 14% 4	100884
	Night	37% 9% 14% 19% 16% 5%	97688
Seeing	Day	11% 4 16% 28% 30% 11%	15543
	Night	12% 5% 19% 30% 27% 7%	25624

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 7% 4 5% 5% 3 6% 8% 43%	2836
	11th to 20th	Day	12% 6% 3 6% 3 4 3 3 5% 8% 45%	2840
	21st to end	Day	14% 11% 3 7% 4 2 3 2 4 5% 45%	3124
February	1st to 10th	Day	14% 8% 3 6% 4 5% 4 4 5% 7% 41%	1710
	11th to 20th	Day	17% 7% 3 5% 3 3 3 3 4 6% 45%	1826
	21st to end	Day	12% 7% 2 7% 5% 4 3 3 6% 6% 45%	1714
March	1st to 10th	Day	18% 9% 4 8% 4 4 3 4 4 6% 36%	3435
	11th to 20th	Day	7% 4 2 4 3 4 4 4 6% 8% 54%	3480
	21st to end	Day	16% 6% 2 5% 4 4 4 4 4 6% 46%	3815
April	1st to 10th	Day	7% 4 2 5% 4 4 5% 3 5% 8% 53%	2102
	11th to 20th	Day	9% 4 2 5% 3 3 4 4 6% 8% 52%	2254
	21st to end	Day	5% 4 1 4 3 3 4 4 5% 9% 59%	2280
May	1st to 10th	Day	6% 4 2 5% 4 5% 5% 5% 7% 10% 48%	4019
	11th to 20th	Day	13% 7% 2 6% 4 4 5% 4 6% 7% 43%	4081
	21st to end	Day	5% 3 2 4 3 4 4 4 7% 11% 53%	4476
June	1st to 10th	Day	8% 6% 2 7% 6% 5% 6% 6% 9% 10% 36%	2470
	11th to 20th	Day	7% 5% 2 4 5% 5% 7% 5% 7% 11% 42%	2470
	21st to end	Day	6% 5% 2 5% 5% 5% 7% 6% 10% 13% 36%	2470
July	1st to 10th	Day	11% 6% 2 7% 5% 6% 7% 6% 8% 11% 32%	4120
	11th to 20th	Day	5% 4 2 7% 5% 6% 6% 6% 9% 14% 37%	4120
	21st to end	Day	5% 5% 2 7% 6% 6% 7% 6% 9% 14% 34%	4466
August	1st to 10th	Day	19% 7% 3 7% 5% 5% 5% 5% 8% 10% 27%	4104
	11th to 20th	Day	5% 4 2 6% 5% 5% 6% 6% 8% 12% 40%	3925
	21st to end	Day	10% 6% 2 6% 4 4 5% 4 7% 9% 41%	4180
September	1st to 10th	Day	12% 5% 3 7% 5% 4 4 5% 6% 10% 38%	2157
	11th to 20th	Day	10% 7% 2 7% 5% 6% 6% 4 8% 9% 37%	2090
	21st to end	Day	13% 6% 3 6% 4 5% 5% 4 6% 8% 41%	2090
October	1st to 10th	Day	11% 6% 2 6% 5% 4 5% 4 6% 5% 47%	1940
	11th to 20th	Day	8% 3 1 4 2 3 3 3 4 6% 61%	1900
	21st to end	Day	9% 5% 2 5% 3 3 3 3 4 7% 56%	2090
November	1st to 10th	Day	10% 5% 1 5% 3 4 4 4 4 6% 54%	1857
	11th to 20th	Day	11% 5% 3 6% 4 4 3 2 4 7% 50%	1900
	21st to end	Day	12% 6% 1 6% 3 3 3 3 4 7% 51%	1744
December	1st to 10th	Day	11% 7% 3 5% 5% 5% 4 3 6% 7% 45%	1710
	11th to 20th	Day	15% 4 2 4 3 2 3 3 4 7% 52%	2153
	21st to end	Day	15% 10% 2 6% 3 3 4 3 5% 5% 42%	3124
January	1st to 10th	Night	13% 6% 2 5% 4 5% 5% 4 5% 7% 43%	4109
	11th to 20th	Night	9% 7% 3 7% 5% 4 5% 4 6% 8% 41%	4120
	21st to end	Night	12% 8% 4 7% 4 4 3 3 5% 6% 44%	4532
February	1st to 10th	Night	15% 6% 2 5% 5% 4 4 4 5% 6% 44%	2470
	11th to 20th	Night	15% 8% 3 5% 4 4 4 3 6% 6% 43%	2237
	21st to end	Night	12% 7% 3 8% 4 5% 4 4 5% 6% 42%	1737
March	1st to 10th	Night	19% 12% 4 8% 5% 3 3 3 3 5% 35%	3418
	11th to 20th	Night	10% 5% 2 5% 4 4 4 4 6% 8% 49%	3480
	21st to end	Night	14% 6% 2 6% 4 3 4 3 5% 7% 45%	3817
April	1st to 10th	Night	8% 5% 3 5% 5% 4 4 4 6% 7% 51%	2076
	11th to 20th	Night	11% 3 2 5% 4 4 4 3 5% 7% 52%	1875
	21st to end	Night	6% 4 2 4 3 3 4 4 7% 7% 55%	1900
May	1st to 10th	Night	4 4 2 5% 4 4 4 4 8% 11% 50%	2890
	11th to 20th	Night	12% 6% 2 5% 4 4 4 4 6% 8% 44%	2812
	21st to end	Night	6% 3 1 5% 4 4 5% 3 7% 9% 52%	3079
June	1st to 10th	Night	8% 7% 2 5% 5% 5% 6% 5% 9% 12% 35%	1710
	11th to 20th	Night	6% 5% 2 5% 5% 6% 6% 6% 8% 13% 38%	1710
	21st to end	Night	5% 5% 2 6% 6% 6% 7% 6% 9% 15% 33%	1710
July	1st to 10th	Night	9% 6% 3 7% 6% 5% 7% 6% 9% 12% 31%	2840
	11th to 20th	Night	5% 4 3 6% 6% 6% 6% 6% 10% 15% 33%	2840
	21st to end	Night	6% 5% 2 8% 6% 6% 8% 7% 10% 15% 27%	3087
August	1st to 10th	Night	17% 8% 2 7% 4 5% 5% 6% 8% 12% 25%	2825
	11th to 20th	Night	6% 4 2 6% 4 6% 6% 5% 8% 13% 38%	2871
	21st to end	Night	8% 6% 3 8% 4 5% 5% 4 7% 9% 43%	3476
September	1st to 10th	Night	10% 6% 3 7% 5% 5% 6% 5% 7% 11% 36%	2019
	11th to 20th	Night	12% 7% 2 7% 5% 6% 7% 4 6% 10% 36%	2090
	21st to end	Night	13% 6% 3 7% 4 4 5% 4 6% 8% 38%	2090
October	1st to 10th	Night	11% 6% 3 6% 5% 4 3 3 5% 8% 46%	2238
	11th to 20th	Night	8% 3 1 4 4 3 4 4 5% 6% 58%	2280
	21st to end	Night	9% 4 1 6% 4 3 3 3 4 5% 57%	2508
November	1st to 10th	Night	10% 5% 2 4 4 3 3 3 5% 7% 55%	2228
	11th to 20th	Night	13% 7% 2 5% 4 3 4 3 5% 6% 50%	2280
	21st to end	Night	11% 6% 2 6% 4 4 4 4 6% 6% 47%	2432
December	1st to 10th	Night	13% 7% 3 6% 4 5% 5% 4 6% 7% 40%	2470
	11th to 20th	Night	15% 7% 2 5% 4 3 3 3 4 6% 48%	3042
	21st to end	Night	17% 8% 3 6% 5% 4 4 4 4 7% 39%	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% 6% 10% 20% 20% 8%	2837
	11th to 20th	Day	36% 5% 9% 17% 23% 10%	2840
	21st to end	Day	41% 7% 7% 16% 22% 8%	3124
February	1st to 10th	Day	42% 6% 11% 17% 19% 6%	1710
	11th to 20th	Day	40% 5% 9% 15% 23% 7%	1836
	21st to end	Day	38% 6% 10% 19% 16% 11%	1714
March	1st to 10th	Day	47% 8% 10% 15% 13% 6%	3435
	11th to 20th	Day	25% 8% 15% 17% 22% 13%	3480
	21st to end	Day	38% 8% 9% 18% 19% 7%	3815
April	1st to 10th	Day	29% 7% 15% 21% 19% 9%	2102
	11th to 20th	Day	29% 7% 13% 24% 18% 9%	2254
	21st to end	Day	22% 7% 15% 31% 20% 5%	2280
May	1st to 10th	Day	27% 11% 20% 28% 11% 3	4056
	11th to 20th	Day	38% 8% 16% 26% 11% 1	4085
	21st to end	Day	23% 10% 21% 27% 18%	4489
June	1st to 10th	Day	36% 15% 19% 18% 10%	2470
	11th to 20th	Day	31% 12% 22% 27% 8%	2470
	21st to end	Day	32% 18% 24% 19% 7% 1	2470
July	1st to 10th	Day	41% 14% 21% 20% 4	4055
	11th to 20th	Day	33% 18% 36% 10% 3	4051
	21st to end	Day	36% 17% 30% 15% 2	4324
August	1st to 10th	Day	48% 12% 26% 11% 2	4091
	11th to 20th	Day	32% 14% 24% 23% 8%	3964
	21st to end	Day	37% 11% 19% 30% 3	4180
September	1st to 10th	Day	39% 13% 20% 15% 11% 3	2157
	11th to 20th	Day	41% 12% 17% 18% 11% 2	2090
	21st to end	Day	39% 9% 15% 20% 13% 3	2090
October	1st to 10th	Day	36% 7% 11% 18% 21% 7%	1940
	11th to 20th	Day	24% 7% 11% 21% 27% 10%	1900
	21st to end	Day	29% 5% 9% 18% 28% 11%	2090
November	1st to 10th	Day	31% 6% 11% 17% 25% 11%	1857
	11th to 20th	Day	35% 5% 11% 17% 22% 10%	1900
	21st to end	Day	34% 6% 10% 23% 22% 6%	1744
December	1st to 10th	Day	39% 7% 13% 20% 15% 7%	1710
	11th to 20th	Day	34% 5% 8% 22% 25% 6%	2150
	21st to end	Day	42% 6% 8% 19% 21% 4	3124
January	1st to 10th	Night	38% 7% 8% 15% 22% 10%	4109
	11th to 20th	Night	38% 6% 9% 17% 25% 5%	4120
	21st to end	Night	40% 7% 8% 13% 23% 10%	4532
February	1st to 10th	Night	40% 5% 9% 21% 18% 8%	2470
	11th to 20th	Night	41% 6% 10% 14% 20% 10%	2238
	21st to end	Night	42% 6% 10% 18% 14% 11%	1737
March	1st to 10th	Night	51% 6% 11% 13% 12% 7%	3418
	11th to 20th	Night	32% 7% 10% 17% 22% 11%	3480
	21st to end	Night	37% 7% 11% 18% 18% 8%	3817
April	1st to 10th	Night	32% 7% 13% 20% 20% 9%	2076
	11th to 20th	Night	32% 5% 10% 22% 20% 11%	1875
	21st to end	Night	26% 8% 13% 25% 23% 5%	1900
May	1st to 10th	Night	24% 11% 21% 28% 13% 3	2918
	11th to 20th	Night	35% 11% 15% 24% 14% 1	2813
	21st to end	Night	25% 10% 17% 29% 17% 1	3087
June	1st to 10th	Night	37% 14% 21% 19% 9%	1710
	11th to 20th	Night	34% 13% 21% 25% 7%	1710
	21st to end	Night	34% 17% 25% 20% 4	1710
July	1st to 10th	Night	41% 12% 21% 21% 4 1	2795
	11th to 20th	Night	36% 17% 34% 10% 3	2786
	21st to end	Night	40% 16% 25% 16% 1	2988
August	1st to 10th	Night	48% 14% 25% 11% 2	2814
	11th to 20th	Night	32% 15% 24% 23% 6%	2898
	21st to end	Night	36% 11% 17% 33% 3	3476
September	1st to 10th	Night	39% 14% 19% 16% 11% 1	2019
	11th to 20th	Night	42% 13% 15% 18% 11% 1	2090
	21st to end	Night	41% 10% 15% 19% 13% 2	2090
October	1st to 10th	Night	37% 8% 11% 19% 19% 7%	2238
	11th to 20th	Night	26% 8% 9% 22% 25% 11%	2280
	21st to end	Night	29% 5% 9% 18% 26% 13%	2508
November	1st to 10th	Night	30% 6% 10% 19% 24% 11%	2228
	11th to 20th	Night	35% 6% 8% 18% 23% 10%	2280
	21st to end	Night	36% 6% 10% 18% 21% 9%	2432
December	1st to 10th	Night	41% 7% 14% 15% 16% 6%	2470
	11th to 20th	Night	38% 5% 8% 17% 26% 6%	3044
	21st to end	Night	44% 7% 7% 20% 18% 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% 5% 33% 41% 8%	270
	11th to 20th	Day	8% 6% 26% 42% 14% 3	270
	21st to end	Day	20% 8% 37% 26% 8%	297
February	1st to 10th	Day	17% 8% 23% 38% 14%	270
	11th to 20th	Day	22% 7% 26% 34% 11%	270
	21st to end	Day	11% 6% 34% 37% 11% 1	369
March	1st to 10th	Day	12% 6% 29% 32% 19% 1	460
	11th to 20th	Day	13% 4 29% 39% 13% 2	460
	21st to end	Day	12% 7% 30% 33% 16% 2	506
April	1st to 10th	Day	10% 7% 26% 36% 18% 2	460
	11th to 20th	Day	9% 6% 23% 31% 24% 7%	452
	21st to end	Day	5% 3 18% 35% 29% 10%	460
May	1st to 10th	Day	5% 3 22% 39% 23% 9%	463
	11th to 20th	Day	10% 3 13% 29% 34% 11%	487
	21st to end	Day	11% 2 8% 26% 38% 16%	529
June	1st to 10th	Day	9% 1 9% 29% 40% 12%	490
	11th to 20th	Day	8% 2 8% 22% 39% 20%	490
	21st to end	Day	6% 1 6% 25% 43% 19%	490
July	1st to 10th	Day	7% 2 5% 15% 45% 27%	485
	11th to 20th	Day	7% 2 3 11% 47% 29%	484
	21st to end	Day	7% 2 4 17% 53% 17%	532
August	1st to 10th	Day	13% 1 4 17% 43% 22%	486
	11th to 20th	Day	7% 1 5% 13% 45% 29%	479
	21st to end	Day	14% 3 6% 16% 37% 24%	539
September	1st to 10th	Day	13% 2 6% 20% 38% 20%	490
	11th to 20th	Day	14% 3 10% 21% 40% 11%	490
	21st to end	Day	15% 2 7% 24% 36% 16%	490
October	1st to 10th	Day	14% 5% 14% 30% 27% 10%	490
	11th to 20th	Day	9% 2 15% 33% 31% 10%	490
	21st to end	Day	11% 5% 14% 29% 33% 8%	539
November	1st to 10th	Day	14% 5% 17% 32% 24% 8%	455
	11th to 20th	Day	15% 6% 25% 34% 17% 2	460
	21st to end	Day	12% 6% 22% 35% 24% 3	304
December	1st to 10th	Day	17% 4 23% 34% 21% 1	270
	11th to 20th	Day	17% 5% 26% 34% 14% 4	270
	21st to end	Day	20% 6% 22% 31% 19% 2	297
January	1st to 10th	Night	12% 10% 33% 34% 10% 1	760
	11th to 20th	Night	13% 10% 30% 32% 15% 1	760
	21st to end	Night	17% 9% 36% 32% 6%	836
February	1st to 10th	Night	17% 8% 28% 34% 13%	760
	11th to 20th	Night	17% 10% 28% 36% 8%	743
	21st to end	Night	15% 6% 27% 40% 11% 1	628
March	1st to 10th	Night	11% 6% 29% 38% 15% 1	760
	11th to 20th	Night	13% 7% 26% 39% 15% 1	760
	21st to end	Night	11% 8% 27% 34% 19% 2	836
April	1st to 10th	Night	9% 8% 27% 33% 20% 3	760
	11th to 20th	Night	11% 6% 20% 34% 23% 5%	751
	21st to end	Night	8% 4 21% 36% 28% 4	760
May	1st to 10th	Night	7% 3 21% 36% 24% 8%	622
	11th to 20th	Night	8% 4 17% 32% 30% 9%	561
	21st to end	Night	10% 1 9% 24% 41% 16%	617
June	1st to 10th	Night	10% 2 8% 31% 38% 11%	570
	11th to 20th	Night	7% 2 8% 23% 41% 19%	570
	21st to end	Night	6% 2 7% 27% 43% 15%	570
July	1st to 10th	Night	9% 2 5% 20% 48% 16%	555
	11th to 20th	Night	10% 1 3 14% 53% 20%	552
	21st to end	Night	6% 1 4 25% 52% 12%	624
August	1st to 10th	Night	11% 2 4 20% 46% 16%	567
	11th to 20th	Night	8% 3 5% 20% 47% 18%	611
	21st to end	Night	13% 1 7% 17% 39% 22%	836
September	1st to 10th	Night	11% 2 8% 21% 42% 16%	760
	11th to 20th	Night	14% 3 8% 22% 43% 10%	760
	21st to end	Night	16% 2 10% 21% 40% 11%	760
October	1st to 10th	Night	14% 3 14% 31% 29% 8%	760
	11th to 20th	Night	10% 3 18% 32% 29% 8%	760
	21st to end	Night	10% 4 19% 29% 30% 7%	836
November	1st to 10th	Night	13% 4 20% 31% 27% 4	743
	11th to 20th	Night	16% 7% 24% 31% 20% 3	760
	21st to end	Night	13% 7% 23% 33% 21% 3	760
December	1st to 10th	Night	15% 8% 25% 34% 15% 3	760
	11th to 20th	Night	19% 7% 25% 29% 17% 3	760
	21st to end	Night	20% 8% 27% 31% 14% 1	836

Page generated at 2024-10-29 11:20:46. Version ac07

Copyright © 2024 Attilla Danko.