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 2024-11-04.

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%	101116
	Night	13% 6% 2 6% 4 4 4 4 6% 8% 43%	97841
Transparency	Day	37% 7% 12% 19% 18% 6%	104845
	Night	37% 7% 11% 18% 19% 8%	102251
Seeing	Day	14% 8% 21% 24% 21% 12%	15264
	Night	14% 6% 22% 32% 22% 3	25311

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	16% 5% 2 5% 3 4 4 3 7% 8% 44%	2836
	11th to 20th	Day	13% 5% 1 4 4 3 3 3 5% 7% 52%	2840
	21st to end	Day	18% 9% 2 6% 4 4 3 3 4 6% 43%	3124
February	1st to 10th	Day	14% 7% 2 7% 4 4 3 4 7% 8% 39%	1790
	11th to 20th	Day	19% 7% 2 6% 3 3 3 3 5% 5% 45%	1848
	21st to end	Day	18% 6% 3 5% 4 4 4 4 4 5% 43%	1594
March	1st to 10th	Day	21% 10% 3 7% 4 3 3 4 5% 5% 36%	3435
	11th to 20th	Day	9% 4 2 5% 4 3 4 3 5% 6% 53%	3480
	21st to end	Day	19% 7% 2 6% 4 3 3 3 5% 5% 42%	3815
April	1st to 10th	Day	9% 6% 2 6% 5% 5% 4 3 5% 7% 49%	2090
	11th to 20th	Day	10% 6% 2 6% 5% 4 4 4 5% 7% 47%	2181
	21st to end	Day	7% 4 1 4 5% 4 4 4 7% 8% 52%	2443
May	1st to 10th	Day	9% 6% 2 6% 5% 5% 5% 3 7% 9% 43%	4082
	11th to 20th	Day	15% 8% 3 6% 4 4 4 4 6% 7% 38%	4081
	21st to end	Day	7% 4 2 5% 4 5% 5% 4 8% 10% 46%	4476
June	1st to 10th	Day	10% 6% 3 8% 5% 5% 5% 5% 8% 10% 36%	2470
	11th to 20th	Day	7% 4 1 5% 4 6% 5% 5% 8% 11% 44%	2470
	21st to end	Day	6% 4 2 6% 6% 6% 6% 5% 8% 11% 38%	2470
July	1st to 10th	Day	12% 8% 3 8% 5% 5% 6% 6% 8% 11% 28%	4120
	11th to 20th	Day	4 5% 2 7% 6% 6% 7% 6% 11% 13% 32%	4120
	21st to end	Day	8% 8% 3 9% 6% 6% 7% 6% 10% 14% 22%	4466
August	1st to 10th	Day	18% 7% 2 8% 5% 6% 6% 5% 8% 11% 24%	4104
	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	12% 6% 2 5% 4 2 3 3 4 6% 53%	1887
	11th to 20th	Day	13% 7% 2 4 3 2 3 2 4 6% 54%	1763
	21st to end	Day	14% 5% 2 5% 4 4 3 3 5% 6% 48%	1710
December	1st to 10th	Day	17% 8% 2 5% 3 5% 4 4 5% 8% 39%	1710
	11th to 20th	Day	16% 5% 2 4 3 3 4 3 5% 7% 49%	2153
	21st to end	Day	18% 8% 2 5% 4 3 3 3 4 7% 42%	3124
January	1st to 10th	Night	17% 6% 2 6% 3 3 4 3 5% 6% 45%	4109
	11th to 20th	Night	10% 6% 2 5% 4 4 4 4 6% 8% 45%	4120
	21st to end	Night	17% 8% 3 7% 3 4 4 3 3 4 44%	4532
February	1st to 10th	Night	15% 6% 2 6% 4 4 4 4 5% 7% 43%	2385
	11th to 20th	Night	18% 7% 2 5% 4 4 3 2 5% 5% 45%	2218
	21st to end	Night	14% 7% 2 6% 3 4 5% 3 5% 7% 44%	1860
March	1st to 10th	Night	21% 9% 3 6% 4 4 3 3 5% 5% 36%	3418
	11th to 20th	Night	11% 5% 2 4 3 3 4 3 6% 8% 51%	3480
	21st to end	Night	18% 6% 2 5% 4 4 4 4 6% 6% 42%	3817
April	1st to 10th	Night	10% 4 2 5% 4 4 5% 4 5% 6% 50%	2090
	11th to 20th	Night	12% 5% 2 4 4 4 4 3 5% 7% 51%	1946
	21st to end	Night	8% 4 1 5% 5% 4 4 3 5% 7% 55%	1751
May	1st to 10th	Night	10% 6% 2 7% 5% 4 4 5% 7% 9% 42%	2813
	11th to 20th	Night	13% 6% 2 6% 4 4 4 3 7% 9% 41%	2812
	21st to end	Night	6% 4 2 5% 4 4 5% 4 7% 9% 50%	3079
June	1st to 10th	Night	11% 8% 2 7% 5% 5% 6% 6% 7% 10% 33%	1710
	11th to 20th	Night	6% 6% 3 6% 5% 5% 4 5% 8% 11% 42%	1710
	21st to end	Night	6% 6% 2 6% 6% 7% 6% 7% 8% 13% 34%	1710
July	1st to 10th	Night	14% 9% 3 8% 5% 5% 6% 5% 8% 9% 29%	2840
	11th to 20th	Night	7% 6% 3 8% 6% 6% 7% 6% 10% 12% 28%	2840
	21st to end	Night	10% 8% 4 10% 6% 7% 7% 5% 9% 11% 23%	3087
August	1st to 10th	Night	17% 7% 3 9% 6% 5% 7% 6% 8% 10% 22%	2825
	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	11% 5% 2 5% 3 3 3 3 5% 5% 55%	2264
	11th to 20th	Night	14% 7% 2 5% 3 3 3 3 3 7% 51%	2413
	21st to end	Night	13% 6% 1 5% 3 3 4 4 5% 6% 49%	2470
December	1st to 10th	Night	16% 5% 2 5% 4 4 4 3 6% 8% 43%	2470
	11th to 20th	Night	17% 6% 2 4 3 3 3 3 4 5% 51%	3042
	21st to end	Night	18% 9% 2 6% 3 4 4 3 5% 6% 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	35% 7% 8% 22% 21% 8%	2837
	11th to 20th	Day	33% 4 6% 18% 28% 11%	2840
	21st to end	Day	43% 4 4 16% 24% 9%	3124
February	1st to 10th	Day	41% 5% 10% 19% 19% 7%	1790
	11th to 20th	Day	42% 4 5% 18% 25% 6%	1858
	21st to end	Day	43% 5% 8% 14% 21% 10%	1594
March	1st to 10th	Day	50% 5% 7% 13% 15% 10%	3435
	11th to 20th	Day	30% 5% 10% 16% 26% 12%	3480
	21st to end	Day	44% 4 6% 19% 22% 5%	3815
April	1st to 10th	Day	34% 5% 9% 19% 26% 7%	2090
	11th to 20th	Day	35% 5% 10% 19% 21% 10%	2181
	21st to end	Day	28% 7% 12% 26% 23% 5%	2443
May	1st to 10th	Day	35% 8% 14% 26% 14% 3	4120
	11th to 20th	Day	44% 6% 11% 23% 15% 1	4085
	21st to end	Day	29% 9% 17% 21% 22% 2	4489
June	1st to 10th	Day	41% 9% 18% 21% 10% 1	2470
	11th to 20th	Day	31% 11% 17% 27% 14% 1	2470
	21st to end	Day	34% 12% 18% 21% 12% 2	2470
July	1st to 10th	Day	45% 11% 19% 18% 6% 2	4055
	11th to 20th	Day	36% 15% 25% 19% 4 1	4051
	21st to end	Day	47% 15% 21% 13% 4 1	4324
August	1st to 10th	Day	51% 11% 20% 15% 3	4091
	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	34% 4 8% 16% 25% 13%	1887
	11th to 20th	Day	33% 3 7% 21% 24% 12%	1763
	21st to end	Day	36% 5% 9% 19% 21% 9%	1710
December	1st to 10th	Day	44% 6% 9% 16% 18% 7%	1710
	11th to 20th	Day	36% 4 7% 19% 24% 9%	2150
	21st to end	Day	43% 4 8% 19% 23% 3	3124
January	1st to 10th	Night	37% 6% 6% 18% 24% 8%	4109
	11th to 20th	Night	35% 5% 7% 21% 25% 7%	4120
	21st to end	Night	44% 5% 4 12% 25% 9%	4532
February	1st to 10th	Night	39% 5% 9% 18% 20% 9%	2385
	11th to 20th	Night	42% 4 6% 18% 22% 9%	2219
	21st to end	Night	39% 5% 10% 16% 18% 12%	1860
March	1st to 10th	Night	49% 6% 11% 13% 14% 7%	3418
	11th to 20th	Night	31% 5% 8% 14% 27% 15%	3480
	21st to end	Night	41% 5% 7% 19% 17% 10%	3817
April	1st to 10th	Night	33% 6% 10% 19% 23% 10%	2090
	11th to 20th	Night	33% 5% 8% 20% 23% 11%	1946
	21st to end	Night	28% 6% 11% 26% 23% 6%	1751
May	1st to 10th	Night	35% 10% 15% 23% 14% 3	2840
	11th to 20th	Night	38% 8% 15% 21% 16% 1	2813
	21st to end	Night	27% 9% 14% 25% 22% 3	3087
June	1st to 10th	Night	41% 11% 17% 18% 12% 1	1710
	11th to 20th	Night	33% 10% 18% 24% 13% 1	1710
	21st to end	Night	36% 13% 21% 17% 11% 2	1710
July	1st to 10th	Night	48% 11% 20% 14% 5% 2	2795
	11th to 20th	Night	41% 15% 25% 15% 4 1	2786
	21st to end	Night	52% 14% 19% 11% 4	2988
August	1st to 10th	Night	53% 12% 18% 13% 3	2814
	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	31% 4 9% 16% 26% 14%	2264
	11th to 20th	Night	35% 4 7% 16% 24% 15%	2413
	21st to end	Night	35% 4 9% 18% 24% 10%	2470
December	1st to 10th	Night	38% 7% 11% 19% 19% 7%	2470
	11th to 20th	Night	36% 4 8% 17% 26% 9%	3044
	21st to end	Night	45% 5% 7% 20% 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	16% 21% 42% 17% 4	270
	11th to 20th	Day	19% 19% 32% 24% 6%	270
	21st to end	Day	21% 21% 38% 15% 4	297
February	1st to 10th	Day	19% 16% 40% 19% 5%	270
	11th to 20th	Day	27% 20% 35% 16% 2	270
	21st to end	Day	21% 23% 33% 17% 5% 1	249
March	1st to 10th	Day	19% 12% 30% 27% 11%	460
	11th to 20th	Day	15% 12% 41% 24% 8% 1	460
	21st to end	Day	18% 14% 36% 22% 9% 1	506
April	1st to 10th	Day	14% 16% 32% 24% 13% 2	460
	11th to 20th	Day	12% 12% 26% 26% 18% 6%	452
	21st to end	Day	10% 12% 22% 28% 21% 8%	460
May	1st to 10th	Day	9% 11% 24% 29% 20% 7%	463
	11th to 20th	Day	15% 2 17% 29% 24% 14%	487
	21st to end	Day	14% 4 12% 26% 26% 19%	529
June	1st to 10th	Day	10% 2 14% 26% 30% 17%	490
	11th to 20th	Day	8% 3 13% 24% 24% 27%	490
	21st to end	Day	8% 1 8% 34% 26% 23%	490
July	1st to 10th	Day	8% 3 6% 18% 33% 31%	485
	11th to 20th	Day	8% 1 4 17% 40% 30%	484
	21st to end	Day	8% 1 6% 25% 35% 24%	532
August	1st to 10th	Day	11% 2 12% 19% 34% 23%	486
	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	17% 6% 25% 27% 19% 6%	467
	11th to 20th	Day	17% 11% 36% 24% 10% 2	323
	21st to end	Day	12% 13% 32% 26% 14% 3	270
December	1st to 10th	Day	22% 11% 34% 24% 7% 1	270
	11th to 20th	Day	19% 14% 38% 18% 10% 1	270
	21st to end	Day	27% 15% 30% 18% 8% 2	297
January	1st to 10th	Night	19% 10% 34% 30% 6%	760
	11th to 20th	Night	17% 10% 33% 32% 8%	760
	21st to end	Night	19% 10% 38% 29% 3	836
February	1st to 10th	Night	18% 10% 31% 34% 7%	760
	11th to 20th	Night	21% 11% 34% 32% 3	743
	21st to end	Night	18% 14% 35% 30% 4	628
March	1st to 10th	Night	15% 9% 33% 36% 7%	760
	11th to 20th	Night	15% 9% 35% 32% 8% 1	760
	21st to end	Night	14% 11% 34% 31% 10%	836
April	1st to 10th	Night	12% 10% 32% 33% 12%	760
	11th to 20th	Night	15% 9% 27% 33% 16%	751
	21st to end	Night	9% 5% 24% 44% 18% 1	611
May	1st to 10th	Night	9% 5% 27% 38% 19% 1	570
	11th to 20th	Night	10% 4 22% 40% 21% 4	561
	21st to end	Night	11% 2 9% 37% 36% 5%	617
June	1st to 10th	Night	14% 2 11% 35% 33% 4	570
	11th to 20th	Night	7% 4 12% 31% 35% 13%	570
	21st to end	Night	7% 3 8% 32% 44% 6%	570
July	1st to 10th	Night	11% 2 6% 28% 45% 8%	555
	11th to 20th	Night	9% 1 3 25% 53% 9%	552
	21st to end	Night	7% 3 7% 29% 48% 7%	624
August	1st to 10th	Night	10% 2 5% 28% 45% 10%	567
	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	13% 5% 22% 34% 22% 3	755
	11th to 20th	Night	17% 8% 26% 34% 14% 1	760
	21st to end	Night	15% 6% 27% 34% 16% 1	760
December	1st to 10th	Night	18% 7% 28% 34% 12% 1	760
	11th to 20th	Night	19% 5% 28% 34% 12% 1	760
	21st to end	Night	24% 10% 26% 31% 9%	836

Page generated at 2024-11-01 22:47:38. Version ac07

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