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 2024-01-12.

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% 5% 2 5% 5% 3 5% 5% 6% 8% 42%	74871
	Night	13% 5% 2 5% 5% 3 4 5% 5% 8% 45%	74862
Transparency	Day	39% 7% 12% 19% 18% 5%	74594
	Night	37% 7% 11% 19% 20% 6%	74658
Seeing	Day	16% 10% 22% 23% 19% 9%	13803
	Night	15% 9% 23% 28% 20% 3	23901

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% 7% 3 5% 4 2 4 4 5% 6% 44%	1706
	11th to 20th	Day	17% 7% 3 5% 4 2 4 4 5% 5% 45%	1635
	21st to end	Day	18% 7% 3 6% 4 2 4 4 5% 6% 44%	1826
February	1st to 10th	Day	17% 6% 3 7% 6% 3 5% 4 4 6% 39%	1800
	11th to 20th	Day	23% 6% 1 4 4 2 4 4 4 5% 43%	1748
	21st to end	Day	21% 7% 2 5% 5% 3 3 4 5% 6% 40%	1480
March	1st to 10th	Day	14% 6% 1 4 5% 2 4 3 4 8% 47%	1872
	11th to 20th	Day	19% 5% 3 5% 5% 3 4 4 5% 7% 40%	1980
	21st to end	Day	16% 5% 3 5% 5% 3 4 5% 6% 7% 41%	2178
April	1st to 10th	Day	13% 5% 2 5% 5% 3 4 5% 5% 6% 47%	1993
	11th to 20th	Day	12% 5% 2 6% 4 3 4 4 5% 7% 47%	2134
	21st to end	Day	10% 4 2 4 4 2 3 5% 6% 8% 52%	2326
May	1st to 10th	Day	10% 4 2 4 4 3 4 4 5% 8% 50%	2340
	11th to 20th	Day	11% 6% 2 6% 5% 3 5% 5% 6% 9% 42%	2301
	21st to end	Day	11% 5% 3 5% 5% 3 5% 5% 7% 10% 42%	2531
June	1st to 10th	Day	10% 5% 3 6% 7% 5% 6% 6% 7% 11% 36%	2340
	11th to 20th	Day	6% 4 2 4 5% 4 5% 7% 8% 11% 44%	2340
	21st to end	Day	6% 4 3 5% 6% 4 7% 7% 8% 10% 40%	2340
July	1st to 10th	Day	9% 5% 3 6% 6% 5% 7% 8% 8% 10% 32%	2340
	11th to 20th	Day	9% 6% 2 6% 6% 5% 7% 8% 8% 12% 31%	2340
	21st to end	Day	7% 5% 3 6% 6% 6% 7% 9% 8% 11% 32%	2547
August	1st to 10th	Day	9% 6% 2 7% 8% 5% 8% 7% 8% 11% 30%	2327
	11th to 20th	Day	12% 6% 3 6% 7% 5% 7% 7% 7% 9% 32%	2200
	21st to end	Day	13% 7% 3 7% 7% 4 6% 6% 7% 10% 30%	2363
September	1st to 10th	Day	10% 6% 3 6% 7% 4 4 6% 7% 8% 39%	1980
	11th to 20th	Day	14% 6% 2 4 4 3 5% 6% 7% 8% 40%	1980
	21st to end	Day	13% 5% 2 5% 4 3 4 4 5% 6% 48%	1980
October	1st to 10th	Day	12% 5% 2 4 4 2 4 3 4 5% 56%	1980
	11th to 20th	Day	11% 5% 1 4 3 2 3 3 5% 5% 56%	1859
	21st to end	Day	12% 5% 2 4 4 2 3 4 4 5% 54%	1980
November	1st to 10th	Day	11% 4 2 4 4 2 3 3 4 5% 57%	1718
	11th to 20th	Day	14% 5% 2 3 3 2 4 4 4 6% 53%	1710
	21st to end	Day	15% 5% 2 5% 4 3 4 4 5% 7% 47%	1710
December	1st to 10th	Day	21% 7% 2 6% 5% 3 3 5% 5% 6% 37%	1710
	11th to 20th	Day	17% 6% 2 6% 5% 3 4 4 4 5% 45%	2153
	21st to end	Day	22% 7% 3 5% 4 3 3 4 6% 7% 37%	3124
January	1st to 10th	Night	20% 7% 2 4 4 2 4 3 4 6% 44%	2459
	11th to 20th	Night	17% 7% 3 5% 5% 3 5% 4 4 6% 42%	2365
	21st to end	Night	18% 6% 3 4 3 3 3 3 4 6% 47%	2527
February	1st to 10th	Night	17% 6% 2 4 4 2 4 4 4 7% 44%	2160
	11th to 20th	Night	22% 5% 3 5% 3 3 4 3 4 5% 44%	2098
	21st to end	Night	22% 6% 2 5% 4 3 3 3 5% 6% 41%	1776
March	1st to 10th	Night	14% 6% 2 5% 4 3 3 4 4 6% 50%	2087
	11th to 20th	Night	15% 6% 2 5% 4 3 4 5% 6% 6% 44%	1980
	21st to end	Night	14% 5% 2 5% 4 3 5% 4 5% 8% 45%	2178
April	1st to 10th	Night	11% 5% 2 3 4 3 4 6% 5% 7% 50%	1980
	11th to 20th	Night	13% 5% 2 4 3 3 3 4 6% 7% 50%	1775
	21st to end	Night	9% 4 2 5% 3 3 4 5% 5% 7% 53%	1632
May	1st to 10th	Night	10% 4 2 5% 5% 3 5% 5% 5% 8% 50%	1620
	11th to 20th	Night	9% 5% 3 5% 6% 3 5% 5% 6% 8% 45%	1592
	21st to end	Night	10% 6% 2 5% 6% 3 5% 5% 6% 9% 44%	1744
June	1st to 10th	Night	8% 4 2 6% 6% 5% 6% 6% 9% 11% 37%	1620
	11th to 20th	Night	4 4 2 4 5% 4 5% 7% 7% 12% 45%	1620
	21st to end	Night	7% 3 2 5% 5% 3 7% 7% 9% 11% 41%	1620
July	1st to 10th	Night	8% 5% 3 5% 6% 4 6% 6% 7% 12% 35%	1620
	11th to 20th	Night	6% 4 3 6% 7% 5% 7% 8% 10% 13% 32%	1620
	21st to end	Night	7% 4 2 6% 6% 5% 8% 7% 8% 13% 33%	1771
August	1st to 10th	Night	8% 6% 3 6% 7% 4 6% 7% 8% 12% 35%	1611
	11th to 20th	Night	12% 4 2 6% 6% 4 5% 5% 7% 10% 38%	1696
	21st to end	Night	14% 7% 3 6% 6% 4 5% 6% 7% 8% 35%	1980
September	1st to 10th	Night	9% 5% 2 6% 6% 3 6% 5% 6% 9% 43%	1975
	11th to 20th	Night	13% 5% 3 5% 6% 3 5% 5% 5% 8% 43%	1980
	21st to end	Night	12% 5% 2 5% 4 3 4 4 5% 7% 48%	1980
October	1st to 10th	Night	13% 5% 1 4 4 2 3 3 5% 7% 53%	1980
	11th to 20th	Night	11% 4 2 4 4 2 3 3 4 5% 56%	2100
	21st to end	Night	13% 4 1 4 3 2 3 4 3 5% 57%	2376
November	1st to 10th	Night	12% 5% 2 3 4 2 3 3 4 5% 58%	2356
	11th to 20th	Night	15% 5% 2 4 4 2 3 3 4 6% 54%	2470
	21st to end	Night	16% 5% 2 4 4 3 4 5% 5% 6% 47%	2470
December	1st to 10th	Night	18% 5% 2 6% 6% 2 4 4 5% 6% 41%	2470
	11th to 20th	Night	17% 6% 2 4 3 2 2 3 5% 6% 49%	3042
	21st to end	Night	20% 8% 3 6% 5% 3 4 4 5% 7% 35%	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	41% 4 10% 18% 22% 5%	1707
	11th to 20th	Day	41% 4 8% 19% 23% 5%	1635
	21st to end	Day	42% 4 6% 21% 21% 7%	1826
February	1st to 10th	Day	45% 5% 8% 17% 20% 4	1800
	11th to 20th	Day	43% 5% 6% 19% 20% 6%	1758
	21st to end	Day	46% 5% 8% 14% 19% 8%	1480
March	1st to 10th	Day	36% 5% 10% 18% 22% 9%	1872
	11th to 20th	Day	44% 5% 11% 17% 17% 6%	1980
	21st to end	Day	42% 6% 11% 21% 17% 4	2178
April	1st to 10th	Day	37% 5% 9% 23% 20% 6%	1993
	11th to 20th	Day	37% 5% 9% 18% 23% 8%	2134
	21st to end	Day	30% 7% 11% 28% 22% 3	2326
May	1st to 10th	Day	31% 6% 14% 22% 23% 3	2340
	11th to 20th	Day	39% 8% 16% 22% 14% 2	2305
	21st to end	Day	35% 10% 12% 26% 16% 2	2531
June	1st to 10th	Day	39% 11% 16% 22% 9% 2	2340
	11th to 20th	Day	30% 11% 21% 24% 12% 1	2340
	21st to end	Day	36% 10% 17% 22% 12% 3	2340
July	1st to 10th	Day	40% 13% 18% 18% 8% 2	2275
	11th to 20th	Day	42% 14% 20% 15% 7% 3	2271
	21st to end	Day	39% 14% 20% 20% 7%	2405
August	1st to 10th	Day	43% 13% 18% 20% 6%	2314
	11th to 20th	Day	45% 12% 16% 16% 10% 2	2200
	21st to end	Day	46% 11% 15% 15% 10% 2	2363
September	1st to 10th	Day	41% 8% 15% 16% 16% 3	1980
	11th to 20th	Day	39% 9% 12% 18% 21% 2	1980
	21st to end	Day	37% 5% 10% 20% 21% 7%	1980
October	1st to 10th	Day	31% 4 11% 18% 29% 7%	1980
	11th to 20th	Day	30% 5% 8% 24% 25% 8%	1859
	21st to end	Day	32% 4 6% 18% 30% 11%	1980
November	1st to 10th	Day	31% 5% 7% 15% 31% 12%	1718
	11th to 20th	Day	32% 4 8% 19% 27% 10%	1710
	21st to end	Day	36% 6% 7% 19% 26% 7%	1710
December	1st to 10th	Day	47% 6% 6% 18% 16% 7%	1710
	11th to 20th	Day	42% 4 6% 16% 24% 8%	2150
	21st to end	Day	44% 6% 9% 18% 19% 3	3124
January	1st to 10th	Night	42% 4 7% 17% 24% 5%	2459
	11th to 20th	Night	44% 3 8% 19% 20% 6%	2365
	21st to end	Night	39% 3 5% 21% 26% 6%	2527
February	1st to 10th	Night	40% 4 9% 19% 20% 8%	2160
	11th to 20th	Night	44% 4 5% 18% 21% 7%	2099
	21st to end	Night	45% 4 8% 16% 18% 9%	1776
March	1st to 10th	Night	37% 4 8% 17% 21% 13%	2087
	11th to 20th	Night	38% 7% 11% 16% 21% 7%	1980
	21st to end	Night	38% 6% 9% 22% 21% 5%	2178
April	1st to 10th	Night	32% 6% 11% 19% 23% 8%	1980
	11th to 20th	Night	33% 4 9% 21% 24% 10%	1775
	21st to end	Night	30% 5% 11% 27% 22% 5%	1632
May	1st to 10th	Night	32% 7% 14% 21% 23% 4	1620
	11th to 20th	Night	35% 9% 16% 22% 15% 2	1593
	21st to end	Night	35% 9% 12% 24% 17% 3	1745
June	1st to 10th	Night	37% 11% 18% 20% 12% 2	1620
	11th to 20th	Night	28% 10% 21% 26% 13% 2	1620
	21st to end	Night	30% 14% 20% 20% 13% 3	1620
July	1st to 10th	Night	38% 13% 19% 19% 9% 2	1575
	11th to 20th	Night	36% 15% 24% 16% 8% 2	1566
	21st to end	Night	36% 13% 24% 18% 7% 2	1672
August	1st to 10th	Night	40% 13% 19% 22% 7% 1	1600
	11th to 20th	Night	40% 11% 18% 17% 13% 1	1696
	21st to end	Night	44% 11% 17% 17% 10% 2	1980
September	1st to 10th	Night	35% 10% 15% 18% 17% 4	1975
	11th to 20th	Night	37% 9% 12% 19% 19% 3	1980
	21st to end	Night	34% 8% 12% 18% 20% 9%	1980
October	1st to 10th	Night	31% 6% 10% 18% 28% 7%	1980
	11th to 20th	Night	32% 5% 7% 21% 25% 10%	2100
	21st to end	Night	29% 4 6% 18% 30% 13%	2376
November	1st to 10th	Night	31% 4 7% 19% 26% 14%	2356
	11th to 20th	Night	33% 4 5% 18% 27% 13%	2470
	21st to end	Night	36% 4 7% 19% 25% 8%	2470
December	1st to 10th	Night	43% 6% 8% 20% 18% 6%	2470
	11th to 20th	Night	37% 3 8% 18% 27% 7%	3044
	21st to end	Night	47% 6% 7% 20% 17% 3	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	23% 22% 40% 13% 1	270
	11th to 20th	Day	24% 22% 27% 20% 5% 1	245
	21st to end	Day	21% 28% 38% 10% 2 1	264
February	1st to 10th	Day	22% 23% 32% 19% 4	240
	11th to 20th	Day	40% 21% 29% 10% 1	240
	21st to end	Day	31% 21% 36% 10% 2	198
March	1st to 10th	Day	19% 18% 34% 21% 8%	312
	11th to 20th	Day	22% 20% 32% 19% 6% 1	420
	21st to end	Day	19% 20% 31% 22% 8% 1	462
April	1st to 10th	Day	18% 17% 29% 23% 12% 1	420
	11th to 20th	Day	15% 17% 29% 22% 16% 2	412
	21st to end	Day	14% 13% 26% 26% 18% 3	420
May	1st to 10th	Day	12% 13% 32% 22% 15% 6%	423
	11th to 20th	Day	15% 4 21% 29% 20% 11%	447
	21st to end	Day	15% 5% 16% 27% 24% 12%	485
June	1st to 10th	Day	12% 4 14% 30% 28% 12%	450
	11th to 20th	Day	6% 5% 15% 28% 25% 20%	450
	21st to end	Day	8% 4 20% 29% 25% 15%	450
July	1st to 10th	Day	11% 2 8% 27% 27% 25%	445
	11th to 20th	Day	11% 2 8% 22% 34% 23%	444
	21st to end	Day	6% 1 9% 24% 39% 22%	488
August	1st to 10th	Day	13% 3 15% 22% 27% 21%	446
	11th to 20th	Day	13% 3 8% 25% 35% 17%	439
	21st to end	Day	15% 3 9% 26% 27% 19%	495
September	1st to 10th	Day	9% 4 13% 27% 32% 14%	450
	11th to 20th	Day	14% 4 12% 25% 31% 13%	450
	21st to end	Day	15% 3 17% 26% 30% 9%	450
October	1st to 10th	Day	16% 5% 23% 26% 20% 10%	450
	11th to 20th	Day	12% 8% 28% 24% 23% 5%	450
	21st to end	Day	17% 10% 25% 26% 19% 3	495
November	1st to 10th	Day	19% 8% 29% 27% 15% 3	316
	11th to 20th	Day	16% 20% 34% 20% 7% 2	270
	21st to end	Day	12% 16% 36% 24% 10% 2	270
December	1st to 10th	Day	29% 20% 30% 17% 3 1	270
	11th to 20th	Day	23% 17% 34% 21% 4 1	270
	21st to end	Day	30% 20% 29% 16% 4 2	297
January	1st to 10th	Night	24% 19% 30% 22% 5%	760
	11th to 20th	Night	20% 17% 31% 24% 8%	728
	21st to end	Night	20% 17% 37% 22% 4	792
February	1st to 10th	Night	19% 15% 32% 28% 5%	720
	11th to 20th	Night	23% 18% 35% 22% 3	703
	21st to end	Night	24% 17% 33% 23% 3	592
March	1st to 10th	Night	18% 15% 34% 30% 4	720
	11th to 20th	Night	17% 13% 36% 24% 9%	720
	21st to end	Night	17% 15% 29% 30% 9%	792
April	1st to 10th	Night	13% 16% 30% 30% 11%	720
	11th to 20th	Night	15% 11% 29% 30% 15% 1	533
	21st to end	Night	11% 8% 29% 30% 21% 1	540
May	1st to 10th	Night	11% 7% 28% 32% 21% 1	540
	11th to 20th	Night	12% 4 23% 32% 24% 5%	531
	21st to end	Night	12% 2 14% 33% 33% 6%	584
June	1st to 10th	Night	9% 1 13% 38% 33% 6%	540
	11th to 20th	Night	4 2 16% 30% 34% 13%	540
	21st to end	Night	8% 2 10% 37% 34% 9%	540
July	1st to 10th	Night	9% 2 7% 26% 42% 14%	525
	11th to 20th	Night	8% 1 7% 22% 51% 11%	522
	21st to end	Night	7% 2 8% 29% 45% 9%	591
August	1st to 10th	Night	12% 2 8% 27% 42% 9%	537
	11th to 20th	Night	11% 3 8% 28% 41% 8%	534
	21st to end	Night	15% 2 9% 28% 37% 9%	594
September	1st to 10th	Night	10% 2 10% 28% 41% 10%	715
	11th to 20th	Night	16% 2 12% 28% 38% 4	720
	21st to end	Night	14% 3 15% 33% 32% 3	720
October	1st to 10th	Night	14% 4 19% 30% 26% 7%	720
	11th to 20th	Night	13% 7% 25% 31% 21% 3	720
	21st to end	Night	14% 8% 23% 32% 21% 2	792
November	1st to 10th	Night	15% 8% 24% 32% 21% 1	740
	11th to 20th	Night	16% 11% 30% 29% 13% 1	760
	21st to end	Night	19% 9% 27% 30% 14% 1	760
December	1st to 10th	Night	19% 15% 29% 28% 8% 1	760
	11th to 20th	Night	21% 11% 33% 26% 9%	760
	21st to end	Night	26% 14% 27% 28% 5%	836

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