Aiken
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Aiken clear sky chart from 2005-11-06 to 2025-08-05.

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% 4 4 5% 4 6% 8% 42%	125690
	Night	12% 6% 2 6% 4 4 4 4 6% 8% 44%	122370
Transparency	Day	37% 7% 12% 19% 18% 6%	129375
	Night	37% 6% 11% 18% 20% 8%	126754
Seeing	Day	14% 8% 22% 24% 21% 12%	16253
	Night	14% 6% 22% 32% 22% 3	26300

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% 4 1 4 2 3 3 3 5% 6% 52%	4056
	11th to 20th	Day	12% 5% 2 4 3 3 3 2 4 6% 56%	4060
	21st to end	Day	15% 8% 3 6% 4 4 3 3 5% 6% 44%	4466
February	1st to 10th	Day	13% 7% 2 7% 4 4 4 4 7% 8% 41%	1885
	11th to 20th	Day	20% 7% 2 6% 3 3 3 3 4 5% 44%	1948
	21st to end	Day	17% 6% 2 5% 4 4 4 4 4 5% 45%	1675
March	1st to 10th	Day	19% 8% 2 7% 4 4 4 4 5% 5% 39%	4935
	11th to 20th	Day	8% 4 2 5% 4 3 4 3 5% 6% 56%	4980
	21st to end	Day	15% 7% 3 7% 4 4 4 3 4 4 46%	5465
April	1st to 10th	Day	9% 6% 2 6% 5% 5% 4 3 5% 8% 49%	2200
	11th to 20th	Day	9% 5% 2 6% 4 4 4 4 5% 7% 49%	2297
	21st to end	Day	7% 4 1 4 5% 4 5% 4 7% 8% 51%	2572
May	1st to 10th	Day	10% 6% 2 6% 5% 5% 5% 3 7% 9% 41%	5862
	11th to 20th	Day	16% 8% 3 7% 4 5% 6% 5% 7% 9% 31%	5861
	21st to end	Day	10% 6% 2 6% 5% 5% 5% 4 7% 8% 42%	6433
June	1st to 10th	Day	10% 6% 3 8% 5% 5% 5% 5% 8% 10% 36%	2600
	11th to 20th	Day	7% 4 2 5% 4 6% 5% 5% 9% 11% 43%	2600
	21st to end	Day	5% 4 2 6% 6% 6% 6% 5% 9% 11% 39%	2600
July	1st to 10th	Day	11% 7% 3 9% 6% 5% 7% 6% 9% 11% 26%	5900
	11th to 20th	Day	3 4 2 6% 5% 6% 7% 6% 11% 16% 33%	5900
	21st to end	Day	7% 7% 3 9% 6% 6% 7% 6% 10% 13% 26%	6424
August	1st to 10th	Day	18% 7% 2 8% 5% 6% 6% 5% 8% 11% 24%	4156
	11th to 20th	Day	9% 5% 2 7% 5% 5% 7% 5% 8% 12% 36%	4044
	21st to end	Day	6% 4 2 5% 4 5% 6% 5% 7% 10% 45%	4102
September	1st to 10th	Day	7% 5% 2 7% 6% 6% 6% 5% 7% 9% 38%	2090
	11th to 20th	Day	13% 7% 2 6% 5% 5% 4 4 6% 8% 40%	2090
	21st to end	Day	15% 7% 3 6% 5% 5% 4 3 5% 6% 42%	2090
October	1st to 10th	Day	11% 6% 2 6% 5% 3 3 3 4 5% 51%	2028
	11th to 20th	Day	9% 5% 2 4 3 3 2 2 4 6% 58%	1900
	21st to end	Day	11% 5% 1 5% 3 3 4 3 4 5% 57%	2090
November	1st to 10th	Day	13% 7% 2 6% 4 3 3 3 4 6% 51%	1957
	11th to 20th	Day	13% 7% 2 4 3 2 3 2 4 6% 54%	1855
	21st to end	Day	14% 5% 2 5% 4 4 3 3 5% 6% 49%	1800
December	1st to 10th	Day	10% 5% 2 5% 3 5% 4 4 5% 7% 50%	2930
	11th to 20th	Day	13% 6% 2 6% 4 4 4 3 5% 7% 46%	3373
	21st to end	Day	20% 7% 2 5% 3 3 3 3 4 6% 44%	4466
January	1st to 10th	Night	12% 5% 2 5% 3 3 3 3 4 5% 56%	5889
	11th to 20th	Night	12% 5% 2 5% 4 4 4 3 6% 7% 48%	5900
	21st to end	Night	15% 8% 3 6% 3 3 3 3 4 5% 45%	6490
February	1st to 10th	Night	14% 6% 2 6% 4 4 4 4 5% 7% 44%	2510
	11th to 20th	Night	18% 8% 2 5% 4 3 3 2 4 5% 44%	2338
	21st to end	Night	13% 6% 2 6% 3 4 5% 3 5% 6% 46%	1954
March	1st to 10th	Night	19% 8% 3 5% 4 4 4 3 5% 6% 38%	4918
	11th to 20th	Night	9% 4 2 4 3 3 4 4 6% 7% 55%	4980
	21st to end	Night	14% 5% 2 5% 3 4 4 3 5% 6% 48%	5467
April	1st to 10th	Night	11% 5% 2 5% 4 4 5% 4 5% 6% 49%	2200
	11th to 20th	Night	11% 5% 2 4 4 4 4 3 5% 7% 52%	2050
	21st to end	Night	8% 4 2 5% 5% 4 4 3 5% 7% 54%	1843
May	1st to 10th	Night	9% 6% 3 7% 5% 5% 4 5% 7% 10% 39%	4033
	11th to 20th	Night	17% 6% 2 6% 4 4 5% 4 7% 10% 35%	4032
	21st to end	Night	10% 6% 2 5% 4 4 5% 4 7% 9% 46%	4421
June	1st to 10th	Night	11% 8% 2 7% 5% 5% 6% 6% 8% 10% 34%	1800
	11th to 20th	Night	6% 6% 3 6% 5% 5% 5% 5% 8% 11% 41%	1800
	21st to end	Night	6% 6% 2 6% 6% 7% 6% 7% 8% 13% 34%	1800
July	1st to 10th	Night	12% 9% 3 9% 6% 6% 7% 6% 8% 9% 25%	4058
	11th to 20th	Night	5% 5% 2 7% 6% 6% 7% 6% 11% 16% 29%	4057
	21st to end	Night	9% 9% 3 10% 7% 6% 7% 6% 8% 11% 24%	4427
August	1st to 10th	Night	17% 7% 3 9% 6% 6% 7% 6% 8% 10% 22%	2861
	11th to 20th	Night	8% 6% 3 7% 5% 6% 6% 5% 9% 11% 35%	2785
	21st to end	Night	5% 5% 2 4 4 4 4 4 6% 11% 49%	3503
September	1st to 10th	Night	9% 6% 2 6% 5% 4 7% 5% 7% 10% 38%	2090
	11th to 20th	Night	11% 7% 3 8% 5% 4 5% 4 5% 7% 41%	2090
	21st to end	Night	13% 6% 2 6% 5% 4 5% 4 5% 6% 42%	2090
October	1st to 10th	Night	11% 5% 2 6% 4 4 3 3 4 5% 52%	2152
	11th to 20th	Night	12% 4 1 5% 3 2 3 3 4 5% 58%	2280
	21st to end	Night	10% 4 2 5% 4 3 4 3 4 6% 57%	2508
November	1st to 10th	Night	12% 5% 2 5% 3 4 3 3 5% 5% 54%	2341
	11th to 20th	Night	14% 7% 3 5% 3 3 3 3 3 7% 51%	2541
	21st to end	Night	12% 6% 1 5% 3 4 4 4 5% 6% 50%	2600
December	1st to 10th	Night	12% 5% 2 5% 3 3 3 3 4 6% 55%	4250
	11th to 20th	Night	16% 7% 3 5% 3 4 3 3 4 6% 47%	4822
	21st to end	Night	19% 8% 2 6% 3 3 4 3 4 5% 43%	6490

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	31% 5% 6% 21% 29% 8%	4057
	11th to 20th	Day	31% 3 5% 17% 34% 10%	4060
	21st to end	Day	41% 3 5% 17% 22% 11%	4466
February	1st to 10th	Day	40% 5% 10% 21% 19% 7%	1885
	11th to 20th	Day	43% 4 5% 18% 24% 6%	1958
	21st to end	Day	41% 4 8% 15% 22% 10%	1675
March	1st to 10th	Day	48% 4 6% 10% 23% 9%	4935
	11th to 20th	Day	28% 4 8% 16% 24% 19%	4980
	21st to end	Day	42% 4 5% 18% 22% 8%	5465
April	1st to 10th	Day	34% 5% 9% 20% 25% 7%	2200
	11th to 20th	Day	34% 5% 10% 20% 21% 10%	2297
	21st to end	Day	29% 6% 12% 26% 22% 4	2572
May	1st to 10th	Day	37% 7% 17% 25% 12% 2	5897
	11th to 20th	Day	48% 7% 16% 18% 11% 1	5865
	21st to end	Day	37% 7% 14% 19% 21% 2	6447
June	1st to 10th	Day	41% 8% 18% 21% 10% 1	2600
	11th to 20th	Day	31% 11% 18% 26% 14% 1	2600
	21st to end	Day	34% 12% 18% 22% 12% 2	2600
July	1st to 10th	Day	46% 11% 18% 19% 5% 1	5835
	11th to 20th	Day	33% 15% 31% 18% 3 1	5831
	21st to end	Day	43% 14% 20% 17% 5%	6240
August	1st to 10th	Day	51% 10% 20% 15% 3	4143
	11th to 20th	Day	38% 11% 17% 22% 12% 1	4083
	21st to end	Day	32% 9% 13% 31% 14% 1	4102
September	1st to 10th	Day	39% 10% 16% 14% 16% 5%	2090
	11th to 20th	Day	41% 7% 12% 17% 18% 4	2090
	21st to end	Day	42% 6% 10% 18% 17% 7%	2090
October	1st to 10th	Day	33% 4 6% 15% 30% 11%	3366
	11th to 20th	Day	17% 2 5% 16% 29% 31%	3140
	21st to end	Day	25% 3 4 20% 33% 15%	3428
November	1st to 10th	Day	36% 4 7% 16% 24% 13%	1957
	11th to 20th	Day	33% 3 7% 20% 24% 12%	1855
	21st to end	Day	36% 5% 9% 19% 22% 9%	1800
December	1st to 10th	Day	35% 5% 7% 17% 28% 9%	2930
	11th to 20th	Day	38% 4 10% 21% 21% 6%	3370
	21st to end	Day	42% 3 7% 23% 23% 2	4466
January	1st to 10th	Night	30% 5% 5% 19% 34% 8%	5889
	11th to 20th	Night	34% 4 5% 18% 31% 7%	5900
	21st to end	Night	41% 4 4 13% 27% 10%	6490
February	1st to 10th	Night	38% 5% 8% 19% 20% 9%	2510
	11th to 20th	Night	43% 4 6% 17% 21% 9%	2339
	21st to end	Night	38% 5% 10% 16% 19% 13%	1954
March	1st to 10th	Night	46% 4 9% 11% 22% 8%	4918
	11th to 20th	Night	28% 4 7% 13% 28% 20%	4980
	21st to end	Night	37% 4 7% 19% 20% 13%	5467
April	1st to 10th	Night	34% 6% 10% 20% 22% 9%	2200
	11th to 20th	Night	32% 5% 8% 21% 23% 11%	2050
	21st to end	Night	29% 6% 11% 26% 22% 6%	1843
May	1st to 10th	Night	38% 9% 15% 24% 12% 2	4060
	11th to 20th	Night	43% 8% 20% 18% 11%	4033
	21st to end	Night	33% 8% 13% 22% 21% 3	4429
June	1st to 10th	Night	41% 10% 17% 18% 12% 1	1800
	11th to 20th	Night	34% 10% 18% 24% 12% 1	1800
	21st to end	Night	35% 13% 21% 18% 11% 2	1800
July	1st to 10th	Night	50% 12% 19% 13% 4 1	4015
	11th to 20th	Night	36% 15% 32% 13% 2 1	4006
	21st to end	Night	51% 12% 18% 15% 4	4297
August	1st to 10th	Night	54% 12% 18% 13% 3	2850
	11th to 20th	Night	39% 11% 21% 20% 9% 1	2812
	21st to end	Night	28% 7% 17% 32% 14% 1	3503
September	1st to 10th	Night	37% 11% 18% 16% 12% 6%	2090
	11th to 20th	Night	41% 8% 13% 17% 17% 4	2090
	21st to end	Night	41% 7% 13% 18% 16% 5%	2090
October	1st to 10th	Night	34% 4 8% 16% 30% 9%	3594
	11th to 20th	Night	19% 2 6% 14% 23% 36%	3779
	21st to end	Night	23% 3 6% 18% 31% 19%	4120
November	1st to 10th	Night	32% 4 8% 17% 25% 14%	2341
	11th to 20th	Night	36% 4 6% 16% 24% 14%	2541
	21st to end	Night	34% 4 9% 18% 24% 10%	2600
December	1st to 10th	Night	32% 4 7% 16% 32% 9%	4250
	11th to 20th	Night	40% 4 11% 18% 20% 8%	4824
	21st to end	Night	43% 4 5% 23% 22% 3	6490

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	16% 21% 43% 17% 3	300
	11th to 20th	Day	19% 20% 32% 23% 6%	300
	21st to end	Day	21% 22% 38% 15% 4	330
February	1st to 10th	Day	17% 16% 42% 19% 5%	300
	11th to 20th	Day	30% 20% 33% 15% 2	300
	21st to end	Day	20% 22% 34% 19% 5% 1	274
March	1st to 10th	Day	19% 14% 30% 26% 11% 1	500
	11th to 20th	Day	14% 13% 40% 25% 7% 1	500
	21st to end	Day	17% 14% 37% 22% 9% 1	550
April	1st to 10th	Day	14% 15% 32% 25% 12% 2	500
	11th to 20th	Day	12% 11% 25% 28% 18% 5%	492
	21st to end	Day	9% 11% 22% 28% 22% 8%	500
May	1st to 10th	Day	9% 11% 24% 30% 20% 7%	503
	11th to 20th	Day	15% 3 19% 29% 22% 13%	527
	21st to end	Day	14% 5% 14% 25% 24% 17%	573
June	1st to 10th	Day	11% 2 16% 26% 29% 16%	530
	11th to 20th	Day	7% 3 12% 25% 26% 25%	530
	21st to end	Day	7% 1 8% 32% 28% 24%	530
July	1st to 10th	Day	8% 3 7% 19% 34% 30%	525
	11th to 20th	Day	7% 2 4 17% 40% 31%	524
	21st to end	Day	7% 1 6% 24% 36% 25%	576
August	1st to 10th	Day	13% 2 11% 19% 34% 22%	502
	11th to 20th	Day	13% 3 6% 17% 37% 25%	479
	21st to end	Day	12% 3 7% 22% 31% 24%	539
September	1st to 10th	Day	10% 4 9% 27% 29% 21%	490
	11th to 20th	Day	17% 3 12% 24% 31% 13%	490
	21st to end	Day	17% 3 16% 23% 29% 13%	490
October	1st to 10th	Day	15% 3 20% 30% 23% 9%	490
	11th to 20th	Day	9% 5% 21% 31% 23% 11%	490
	21st to end	Day	13% 5% 23% 30% 22% 5%	539
November	1st to 10th	Day	19% 6% 24% 27% 19% 5%	495
	11th to 20th	Day	18% 11% 36% 23% 10% 2	355
	21st to end	Day	11% 13% 32% 27% 13% 2	300
December	1st to 10th	Day	20% 12% 38% 23% 7% 1	300
	11th to 20th	Day	18% 15% 38% 18% 10% 1	300
	21st to end	Day	28% 14% 30% 18% 8% 2	330
January	1st to 10th	Night	19% 11% 35% 30% 6%	800
	11th to 20th	Night	17% 10% 34% 31% 8%	800
	21st to end	Night	19% 11% 38% 29% 3	880
February	1st to 10th	Night	17% 10% 31% 34% 8%	800
	11th to 20th	Night	21% 11% 34% 31% 3	783
	21st to end	Night	17% 13% 35% 30% 4	660
March	1st to 10th	Night	15% 10% 33% 35% 7%	800
	11th to 20th	Night	15% 9% 36% 32% 8% 1	800
	21st to end	Night	14% 11% 36% 30% 9%	880
April	1st to 10th	Night	13% 10% 32% 34% 12%	800
	11th to 20th	Night	14% 9% 27% 34% 16%	791
	21st to end	Night	8% 5% 23% 44% 18% 1	643
May	1st to 10th	Night	10% 5% 27% 39% 18% 1	600
	11th to 20th	Night	10% 4 23% 39% 20% 4	591
	21st to end	Night	11% 3 10% 36% 35% 4	650
June	1st to 10th	Night	14% 2 13% 36% 33% 4	600
	11th to 20th	Night	7% 4 12% 31% 35% 12%	600
	21st to end	Night	7% 3 8% 32% 45% 6%	600
July	1st to 10th	Night	11% 2 6% 28% 45% 8%	585
	11th to 20th	Night	8% 1 3 25% 52% 10%	582
	21st to end	Night	6% 4 7% 28% 49% 7%	657
August	1st to 10th	Night	11% 2 6% 27% 45% 9%	579
	11th to 20th	Night	13% 2 4 30% 44% 8%	564
	21st to end	Night	11% 2 10% 27% 41% 8%	759
September	1st to 10th	Night	10% 3 9% 30% 42% 6%	760
	11th to 20th	Night	14% 3 11% 29% 39% 4	760
	21st to end	Night	16% 2 13% 31% 33% 5%	760
October	1st to 10th	Night	14% 4 15% 36% 26% 6%	760
	11th to 20th	Night	15% 3 20% 35% 24% 3	760
	21st to end	Night	11% 5% 22% 34% 26% 2	836
November	1st to 10th	Night	14% 5% 22% 33% 22% 3	780
	11th to 20th	Night	17% 8% 26% 34% 14% 1	800
	21st to end	Night	15% 7% 28% 34% 16% 1	800
December	1st to 10th	Night	18% 7% 29% 34% 11% 1	800
	11th to 20th	Night	19% 5% 29% 34% 12% 1	800
	21st to end	Night	24% 10% 26% 31% 9%	880

Page generated at 2025-08-02 01:32:24. Version ac07

Copyright © 2025 Attilla Danko.