Dacula
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dacula clear sky chart from 2005-11-06 to 2025-11-18.

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 6% 4 4 5% 4 6% 8% 42%	126655
	Night	13% 6% 2 6% 4 4 4 4 5% 7% 44%	123714
Transparency	Day	38% 7% 12% 20% 18% 6%	130431
	Night	37% 6% 10% 19% 20% 7%	128007
Seeing	Day	16% 10% 23% 24% 18% 8%	16311
	Night	15% 9% 24% 29% 20% 3	26316

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	17% 10% 3 5% 3 2 3 3 3 5% 47%	4056
	11th to 20th	Day	11% 8% 2 5% 3 2 4 3 4 5% 54%	4060
	21st to end	Day	23% 9% 3 6% 3 2 3 2 4 5% 41%	4580
February	1st to 10th	Day	16% 7% 2 7% 5% 4 4 4 5% 6% 41%	2000
	11th to 20th	Day	23% 7% 1 4 3 3 3 3 4 5% 42%	1948
	21st to end	Day	19% 7% 2 6% 4 4 3 3 5% 6% 41%	1650
March	1st to 10th	Day	21% 9% 2 8% 4 4 4 3 4 6% 35%	4664
	11th to 20th	Day	10% 5% 2 6% 4 4 4 3 5% 6% 51%	4980
	21st to end	Day	17% 6% 3 6% 4 4 4 3 4 5% 45%	5465
April	1st to 10th	Day	13% 5% 2 6% 5% 4 4 4 5% 6% 46%	2215
	11th to 20th	Day	11% 5% 2 6% 4 4 4 4 5% 7% 48%	2374
	21st to end	Day	10% 5% 1 5% 4 4 3 4 6% 7% 50%	2585
May	1st to 10th	Day	14% 7% 2 6% 4 4 5% 4 6% 9% 38%	5862
	11th to 20th	Day	17% 9% 3 7% 5% 5% 5% 4 7% 8% 30%	5861
	21st to end	Day	13% 7% 2 6% 4 4 5% 4 6% 8% 41%	6433
June	1st to 10th	Day	10% 5% 2 7% 6% 6% 6% 5% 8% 11% 35%	2600
	11th to 20th	Day	6% 4 1 5% 5% 5% 5% 6% 9% 11% 43%	2600
	21st to end	Day	6% 4 2 6% 6% 5% 6% 6% 8% 10% 41%	2600
July	1st to 10th	Day	6% 5% 2 7% 6% 6% 8% 6% 9% 11% 34%	5900
	11th to 20th	Day	5% 4 2 6% 6% 7% 7% 7% 9% 13% 34%	5900
	21st to end	Day	8% 8% 4 9% 6% 7% 8% 6% 8% 11% 25%	6424
August	1st to 10th	Day	9% 6% 2 7% 5% 6% 6% 5% 8% 12% 34%	4234
	11th to 20th	Day	7% 5% 2 6% 4 5% 6% 5% 7% 11% 41%	3981
	21st to end	Day	7% 5% 2 5% 4 4 5% 5% 6% 9% 48%	4284
September	1st to 10th	Day	9% 6% 3 6% 6% 5% 5% 5% 7% 8% 40%	2200
	11th to 20th	Day	15% 6% 3 5% 3 5% 5% 5% 7% 8% 40%	2200
	21st to end	Day	13% 6% 2 6% 4 4 4 3 5% 7% 47%	2200
October	1st to 10th	Day	11% 6% 2 4 3 3 4 2 5% 5% 55%	2200
	11th to 20th	Day	11% 5% 1 5% 3 2 3 2 5% 5% 59%	2065
	21st to end	Day	12% 5% 2 5% 3 3 3 3 4 5% 55%	2200
November	1st to 10th	Day	12% 5% 2 5% 3 3 3 3 4 5% 56%	1902
	11th to 20th	Day	13% 5% 2 3 3 3 3 3 4 7% 53%	1863
	21st to end	Day	14% 5% 2 5% 3 4 4 4 5% 7% 48%	1800
December	1st to 10th	Day	19% 6% 1 5% 3 3 3 4 5% 5% 46%	2930
	11th to 20th	Day	15% 8% 3 7% 4 4 4 3 5% 5% 42%	3373
	21st to end	Day	23% 6% 2 4 3 4 3 3 5% 7% 40%	4466
January	1st to 10th	Night	16% 5% 2 5% 3 3 3 3 4 6% 50%	5889
	11th to 20th	Night	13% 7% 2 5% 4 3 4 3 4 5% 49%	5900
	21st to end	Night	19% 8% 2 5% 3 3 3 3 4 5% 44%	6373
February	1st to 10th	Night	16% 7% 2 5% 4 3 4 3 5% 6% 45%	2400
	11th to 20th	Night	22% 6% 2 6% 4 3 3 2 4 4 43%	2338
	21st to end	Night	20% 6% 2 6% 3 4 3 3 5% 5% 43%	1980
March	1st to 10th	Night	21% 8% 3 6% 4 3 4 4 5% 6% 37%	5174
	11th to 20th	Night	10% 4 1 4 3 3 4 3 6% 7% 53%	4980
	21st to end	Night	15% 6% 2 6% 4 4 4 3 5% 7% 45%	5467
April	1st to 10th	Night	11% 5% 1 4 4 4 4 5% 6% 7% 49%	2200
	11th to 20th	Night	12% 5% 2 5% 2 3 4 4 6% 6% 51%	1975
	21st to end	Night	9% 5% 2 6% 4 4 3 4 5% 7% 51%	1812
May	1st to 10th	Night	10% 7% 3 8% 5% 5% 5% 4 7% 9% 36%	4033
	11th to 20th	Night	19% 7% 2 7% 5% 5% 5% 4 6% 9% 32%	4032
	21st to end	Night	12% 6% 2 5% 4 4 4 4 6% 9% 43%	4421
June	1st to 10th	Night	8% 4 2 7% 5% 6% 5% 5% 9% 11% 37%	1800
	11th to 20th	Night	5% 4 2 5% 5% 6% 5% 5% 8% 12% 43%	1800
	21st to end	Night	6% 4 2 6% 5% 5% 6% 6% 9% 11% 41%	1800
July	1st to 10th	Night	7% 7% 4 9% 6% 6% 6% 5% 8% 11% 32%	4058
	11th to 20th	Night	5% 5% 2 8% 5% 6% 7% 7% 11% 14% 32%	4057
	21st to end	Night	10% 9% 3 8% 6% 6% 7% 5% 7% 10% 28%	4427
August	1st to 10th	Night	9% 6% 3 7% 5% 5% 6% 5% 8% 13% 34%	2915
	11th to 20th	Night	8% 5% 2 7% 5% 5% 4 4 7% 9% 44%	3063
	21st to end	Night	8% 5% 2 5% 4 4 4 4 5% 8% 51%	3586
September	1st to 10th	Night	9% 6% 2 7% 5% 5% 6% 4 6% 9% 42%	2195
	11th to 20th	Night	13% 5% 3 7% 5% 4 5% 4 6% 8% 42%	2200
	21st to end	Night	13% 5% 2 6% 4 4 4 3 5% 8% 46%	2200
October	1st to 10th	Night	12% 5% 1 5% 4 3 3 3 5% 7% 53%	2200
	11th to 20th	Night	10% 4 2 5% 4 3 3 2 4 4 60%	2334
	21st to end	Night	13% 4 1 4 3 3 3 3 3 5% 58%	2640
November	1st to 10th	Night	13% 6% 2 4 3 3 3 3 4 5% 55%	2611
	11th to 20th	Night	14% 5% 1 4 3 3 2 2 4 6% 55%	2692
	21st to end	Night	15% 6% 1 4 3 4 4 4 5% 6% 48%	2600
December	1st to 10th	Night	16% 6% 2 5% 3 2 3 2 4 5% 51%	4250
	11th to 20th	Night	18% 6% 2 5% 3 3 3 3 5% 6% 46%	4822
	21st to end	Night	21% 7% 2 6% 4 3 3 3 4 6% 41%	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	40% 4 6% 19% 23% 8%	4057
	11th to 20th	Day	33% 3 5% 21% 28% 10%	4060
	21st to end	Day	47% 3 4 17% 21% 9%	4580
February	1st to 10th	Day	43% 5% 8% 19% 20% 5%	2000
	11th to 20th	Day	44% 5% 6% 18% 20% 6%	1958
	21st to end	Day	44% 5% 8% 14% 21% 8%	1650
March	1st to 10th	Day	50% 4 7% 12% 19% 8%	4664
	11th to 20th	Day	33% 4 7% 14% 23% 18%	4980
	21st to end	Day	42% 4 6% 22% 21% 5%	5465
April	1st to 10th	Day	37% 6% 9% 23% 20% 6%	2215
	11th to 20th	Day	35% 5% 9% 19% 24% 8%	2374
	21st to end	Day	31% 7% 11% 27% 21% 3	2585
May	1st to 10th	Day	41% 8% 15% 20% 15% 1	5897
	11th to 20th	Day	48% 9% 14% 20% 8% 1	5865
	21st to end	Day	39% 8% 11% 23% 18% 1	6447
June	1st to 10th	Day	39% 11% 17% 22% 9% 2	2600
	11th to 20th	Day	29% 11% 21% 24% 13% 1	2600
	21st to end	Day	34% 10% 18% 23% 13% 3	2600
July	1st to 10th	Day	39% 12% 18% 24% 6% 1	5835
	11th to 20th	Day	37% 14% 27% 17% 4 1	5831
	21st to end	Day	48% 12% 17% 19% 3	6240
August	1st to 10th	Day	39% 9% 16% 29% 7%	4221
	11th to 20th	Day	33% 9% 19% 23% 14% 2	4020
	21st to end	Day	31% 8% 15% 23% 20% 3	4284
September	1st to 10th	Day	40% 8% 15% 17% 17% 4	2200
	11th to 20th	Day	39% 8% 12% 19% 20% 2	2200
	21st to end	Day	37% 5% 13% 19% 20% 6%	2200
October	1st to 10th	Day	26% 3 7% 13% 39% 12%	3590
	11th to 20th	Day	20% 3 5% 15% 29% 28%	3344
	21st to end	Day	27% 3 5% 21% 31% 13%	3538
November	1st to 10th	Day	32% 4 7% 15% 30% 11%	1902
	11th to 20th	Day	31% 4 7% 20% 27% 10%	1863
	21st to end	Day	35% 6% 7% 19% 27% 7%	1800
December	1st to 10th	Day	40% 4 5% 17% 27% 8%	2930
	11th to 20th	Day	45% 4 7% 17% 20% 6%	3370
	21st to end	Day	43% 4 8% 25% 18% 2	4466
January	1st to 10th	Night	34% 4 6% 20% 29% 7%	5889
	11th to 20th	Night	37% 3 5% 19% 27% 9%	5900
	21st to end	Night	43% 3 5% 15% 28% 6%	6373
February	1st to 10th	Night	39% 4 9% 19% 20% 8%	2400
	11th to 20th	Night	46% 3 5% 18% 20% 8%	2339
	21st to end	Night	43% 4 7% 17% 19% 11%	1980
March	1st to 10th	Night	47% 5% 8% 14% 19% 8%	5174
	11th to 20th	Night	29% 5% 8% 14% 27% 18%	4980
	21st to end	Night	39% 4 6% 21% 20% 10%	5467
April	1st to 10th	Night	33% 7% 11% 19% 23% 8%	2200
	11th to 20th	Night	32% 4 8% 21% 24% 10%	1975
	21st to end	Night	31% 5% 11% 26% 21% 5%	1812
May	1st to 10th	Night	40% 10% 16% 19% 13% 2	4060
	11th to 20th	Night	47% 7% 16% 19% 10% 1	4033
	21st to end	Night	35% 8% 13% 24% 18% 2	4429
June	1st to 10th	Night	37% 11% 18% 21% 12% 2	1800
	11th to 20th	Night	29% 11% 20% 25% 13% 1	1800
	21st to end	Night	30% 13% 19% 20% 14% 4	1800
July	1st to 10th	Night	43% 12% 19% 21% 5% 1	4015
	11th to 20th	Night	36% 16% 26% 17% 4 1	4006
	21st to end	Night	48% 11% 20% 16% 4 1	4297
August	1st to 10th	Night	40% 10% 17% 27% 6%	2904
	11th to 20th	Night	35% 9% 18% 22% 14% 1	3090
	21st to end	Night	31% 8% 13% 22% 24% 2	3586
September	1st to 10th	Night	37% 10% 15% 18% 17% 4	2195
	11th to 20th	Night	38% 9% 12% 20% 18% 3	2200
	21st to end	Night	36% 7% 13% 17% 19% 8%	2200
October	1st to 10th	Night	28% 4 8% 13% 36% 10%	3590
	11th to 20th	Night	18% 3 4 17% 31% 27%	3794
	21st to end	Night	24% 3 5% 21% 30% 18%	4252
November	1st to 10th	Night	33% 4 7% 19% 26% 13%	2611
	11th to 20th	Night	32% 4 5% 18% 29% 13%	2692
	21st to end	Night	35% 4 7% 20% 25% 8%	2600
December	1st to 10th	Night	37% 4 5% 18% 29% 8%	4250
	11th to 20th	Night	39% 4 11% 17% 23% 7%	4824
	21st to end	Night	44% 4 6% 26% 17% 2	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	25% 24% 39% 11% 1	300
	11th to 20th	Day	26% 24% 28% 17% 5% 1	300
	21st to end	Day	23% 26% 38% 10% 2 1	330
February	1st to 10th	Day	20% 22% 34% 19% 5%	300
	11th to 20th	Day	42% 20% 26% 11% 1	300
	21st to end	Day	30% 21% 37% 11% 2	249
March	1st to 10th	Day	24% 18% 31% 19% 8%	380
	11th to 20th	Day	22% 20% 34% 19% 6% 1	500
	21st to end	Day	20% 19% 34% 20% 6% 1	550
April	1st to 10th	Day	19% 18% 30% 22% 10% 1	500
	11th to 20th	Day	14% 16% 30% 24% 14% 1	492
	21st to end	Day	14% 12% 26% 28% 17% 3	500
May	1st to 10th	Day	13% 13% 32% 21% 14% 6%	503
	11th to 20th	Day	17% 6% 25% 26% 18% 9%	527
	21st to end	Day	16% 7% 19% 26% 21% 11%	573
June	1st to 10th	Day	12% 5% 17% 29% 27% 11%	530
	11th to 20th	Day	6% 4 17% 29% 25% 18%	530
	21st to end	Day	8% 3 17% 31% 27% 15%	530
July	1st to 10th	Day	9% 2 9% 28% 27% 25%	525
	11th to 20th	Day	9% 2 8% 24% 35% 22%	524
	21st to end	Day	7% 1 10% 25% 38% 19%	576
August	1st to 10th	Day	15% 4 15% 23% 25% 18%	526
	11th to 20th	Day	12% 3 9% 25% 35% 16%	519
	21st to end	Day	14% 3 10% 27% 27% 19%	583
September	1st to 10th	Day	9% 4 15% 31% 29% 12%	530
	11th to 20th	Day	15% 4 12% 26% 31% 12%	530
	21st to end	Day	15% 5% 17% 26% 29% 8%	530
October	1st to 10th	Day	16% 5% 23% 28% 19% 8%	530
	11th to 20th	Day	11% 8% 27% 26% 23% 5%	530
	21st to end	Day	17% 10% 26% 26% 19% 2	583
November	1st to 10th	Day	20% 8% 29% 27% 14% 2	380
	11th to 20th	Day	16% 19% 36% 19% 7% 2	321
	21st to end	Day	14% 16% 36% 23% 9% 2	300
December	1st to 10th	Day	29% 21% 31% 15% 3 1	300
	11th to 20th	Day	24% 16% 33% 22% 5% 1	300
	21st to end	Day	30% 18% 29% 16% 4 2	330
January	1st to 10th	Night	25% 20% 30% 21% 5%	800
	11th to 20th	Night	20% 19% 32% 22% 7%	800
	21st to end	Night	20% 18% 37% 21% 3	880
February	1st to 10th	Night	19% 15% 32% 30% 5%	800
	11th to 20th	Night	24% 19% 33% 22% 3	783
	21st to end	Night	22% 18% 34% 23% 3	660
March	1st to 10th	Night	19% 14% 34% 29% 4	800
	11th to 20th	Night	17% 13% 37% 25% 8%	800
	21st to end	Night	17% 16% 30% 29% 8%	880
April	1st to 10th	Night	13% 17% 31% 28% 10%	800
	11th to 20th	Night	15% 10% 31% 30% 13% 1	593
	21st to end	Night	10% 8% 29% 31% 20% 1	600
May	1st to 10th	Night	11% 7% 28% 33% 20% 1	600
	11th to 20th	Night	13% 5% 24% 32% 22% 4	591
	21st to end	Night	12% 3 15% 34% 30% 5%	650
June	1st to 10th	Night	9% 2 14% 38% 32% 6%	600
	11th to 20th	Night	5% 3 17% 31% 33% 12%	600
	21st to end	Night	7% 2 10% 36% 36% 9%	600
July	1st to 10th	Night	10% 2 8% 26% 42% 14%	585
	11th to 20th	Night	7% 2 8% 23% 50% 10%	582
	21st to end	Night	7% 2 8% 31% 44% 9%	657
August	1st to 10th	Night	13% 2 9% 28% 39% 8%	597
	11th to 20th	Night	11% 3 10% 27% 40% 9%	594
	21st to end	Night	15% 2 10% 28% 37% 8%	660
September	1st to 10th	Night	10% 3 12% 29% 38% 9%	795
	11th to 20th	Night	16% 2 11% 28% 38% 4	800
	21st to end	Night	15% 3 15% 33% 32% 3	800
October	1st to 10th	Night	14% 4 19% 32% 26% 6%	800
	11th to 20th	Night	12% 7% 25% 32% 22% 3	800
	21st to end	Night	14% 8% 23% 33% 20% 2	880
November	1st to 10th	Night	16% 7% 24% 32% 20% 1	820
	11th to 20th	Night	17% 11% 31% 28% 13%	829
	21st to end	Night	18% 11% 28% 29% 13% 1	800
December	1st to 10th	Night	19% 15% 31% 28% 8% 1	800
	11th to 20th	Night	21% 12% 33% 25% 9%	800
	21st to end	Night	26% 14% 27% 29% 5%	880

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