Augusta
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Augusta 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%	125671
	Night	13% 6% 2 6% 4 4 4 4 6% 8% 44%	122403
Transparency	Day	24% 39% 8% 13% 12% 4	129369
	Night	24% 38% 7% 12% 14% 5%	126774
Seeing	Day	15% 8% 22% 24% 21% 11%	16218
	Night	15% 6% 22% 32% 22% 3	26262

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 3 2 3 3 5% 6% 53%	4056
	11th to 20th	Day	13% 4 2 5% 3 2 2 2 3 6% 57%	4060
	21st to end	Day	17% 7% 2 5% 4 4 3 3 4 6% 45%	4466
February	1st to 10th	Day	15% 6% 3 5% 5% 4 4 4 6% 8% 40%	1910
	11th to 20th	Day	20% 7% 2 5% 3 3 3 3 4 4 45%	1948
	21st to end	Day	17% 7% 2 5% 3 4 4 4 4 5% 45%	1660
March	1st to 10th	Day	19% 8% 3 7% 4 3 4 3 4 5% 39%	4935
	11th to 20th	Day	8% 4 2 5% 3 3 4 3 5% 7% 56%	4980
	21st to end	Day	16% 6% 2 6% 4 4 3 3 3 5% 46%	5465
April	1st to 10th	Day	10% 5% 2 5% 4 4 5% 3 5% 7% 50%	2200
	11th to 20th	Day	10% 5% 2 6% 4 3 4 4 5% 7% 50%	2279
	21st to end	Day	7% 4 2 5% 4 4 4 4 6% 9% 51%	2596
May	1st to 10th	Day	11% 6% 2 6% 4 5% 5% 4 6% 9% 41%	5862
	11th to 20th	Day	17% 7% 2 7% 5% 5% 5% 5% 7% 8% 32%	5861
	21st to end	Day	11% 5% 2 6% 5% 5% 5% 4 7% 8% 43%	6433
June	1st to 10th	Day	10% 6% 2 6% 5% 5% 6% 4 8% 11% 36%	2600
	11th to 20th	Day	6% 4 2 5% 4 6% 5% 5% 9% 11% 44%	2600
	21st to end	Day	5% 5% 1 6% 5% 6% 6% 6% 9% 11% 39%	2600
July	1st to 10th	Day	11% 6% 3 8% 6% 7% 7% 6% 9% 10% 26%	5900
	11th to 20th	Day	4 4 2 6% 6% 7% 7% 6% 10% 16% 33%	5900
	21st to end	Day	8% 6% 3 8% 6% 7% 6% 7% 10% 14% 26%	6424
August	1st to 10th	Day	17% 7% 2 8% 5% 5% 7% 6% 9% 10% 24%	4156
	11th to 20th	Day	9% 5% 2 7% 5% 5% 6% 6% 8% 12% 35%	4044
	21st to end	Day	7% 5% 2 5% 5% 5% 5% 4 7% 11% 46%	4072
September	1st to 10th	Day	8% 6% 2 7% 5% 5% 7% 4 7% 8% 41%	2090
	11th to 20th	Day	14% 6% 2 6% 4 4 5% 5% 6% 8% 40%	2090
	21st to end	Day	15% 7% 3 6% 5% 4 4 3 5% 6% 42%	2090
October	1st to 10th	Day	12% 6% 3 6% 4 3 4 4 4 5% 50%	2043
	11th to 20th	Day	10% 5% 1 4 3 3 2 2 5% 5% 59%	1900
	21st to end	Day	11% 4 2 5% 4 4 3 3 3 4 57%	2090
November	1st to 10th	Day	13% 6% 2 5% 4 3 3 3 4 6% 51%	1957
	11th to 20th	Day	14% 6% 2 3 2 3 3 3 4 6% 54%	1835
	21st to end	Day	14% 5% 3 5% 4 4 3 3 5% 6% 49%	1800
December	1st to 10th	Day	13% 4 2 5% 4 4 4 3 5% 6% 50%	2930
	11th to 20th	Day	15% 6% 2 5% 4 4 3 3 5% 6% 47%	3373
	21st to end	Day	21% 7% 2 4 3 3 3 3 4 6% 44%	4466
January	1st to 10th	Night	13% 5% 2 4 3 3 3 2 4 5% 56%	5889
	11th to 20th	Night	12% 5% 1 5% 4 4 4 4 6% 7% 49%	5900
	21st to end	Night	17% 8% 2 5% 4 3 3 3 4 5% 46%	6490
February	1st to 10th	Night	15% 6% 2 5% 4 3 4 3 5% 7% 44%	2485
	11th to 20th	Night	19% 7% 2 5% 4 4 3 3 4 5% 44%	2338
	21st to end	Night	13% 7% 2 6% 4 5% 3 3 5% 6% 46%	1970
March	1st to 10th	Night	21% 7% 2 6% 4 3 4 3 5% 6% 39%	4918
	11th to 20th	Night	10% 3 2 3 3 3 3 3 6% 8% 55%	4980
	21st to end	Night	15% 4 2 5% 3 3 4 4 5% 6% 48%	5467
April	1st to 10th	Night	11% 5% 1 5% 5% 4 5% 4 5% 7% 49%	2200
	11th to 20th	Night	11% 4 1 5% 4 3 4 3 5% 7% 53%	2069
	21st to end	Night	8% 4 2 6% 4 4 4 4 6% 7% 53%	1819
May	1st to 10th	Night	10% 6% 3 6% 5% 5% 5% 4 7% 10% 39%	4033
	11th to 20th	Night	18% 5% 2 6% 4 4 4 4 7% 10% 36%	4032
	21st to end	Night	11% 5% 2 5% 4 4 5% 4 6% 8% 46%	4421
June	1st to 10th	Night	10% 7% 2 6% 5% 6% 6% 6% 7% 10% 34%	1800
	11th to 20th	Night	6% 6% 2 7% 5% 5% 5% 5% 7% 11% 41%	1800
	21st to end	Night	6% 4 2 6% 6% 7% 6% 6% 10% 12% 35%	1800
July	1st to 10th	Night	15% 7% 3 8% 7% 6% 6% 5% 8% 10% 25%	4058
	11th to 20th	Night	5% 5% 2 7% 5% 6% 7% 6% 11% 16% 30%	4057
	21st to end	Night	11% 7% 3 9% 6% 7% 7% 6% 9% 11% 24%	4427
August	1st to 10th	Night	17% 7% 3 8% 6% 6% 7% 6% 8% 10% 22%	2861
	11th to 20th	Night	10% 6% 2 6% 5% 5% 7% 5% 7% 10% 36%	2785
	21st to end	Night	6% 5% 1 5% 4 4 5% 4 6% 11% 49%	3547
September	1st to 10th	Night	9% 6% 2 7% 5% 5% 5% 6% 7% 10% 38%	2090
	11th to 20th	Night	12% 6% 3 8% 5% 6% 4 4 5% 7% 40%	2090
	21st to end	Night	14% 5% 2 6% 4 5% 4 4 6% 7% 43%	2090
October	1st to 10th	Night	13% 5% 2 6% 4 4 3 2 4 7% 51%	2136
	11th to 20th	Night	12% 4 2 5% 3 2 3 3 4 5% 59%	2280
	21st to end	Night	10% 4 1 5% 3 3 4 3 4 6% 58%	2508
November	1st to 10th	Night	13% 5% 2 5% 3 3 3 2 4 6% 54%	2341
	11th to 20th	Night	14% 7% 2 4 4 3 3 2 4 5% 52%	2560
	21st to end	Night	13% 5% 2 5% 3 4 4 4 4 7% 50%	2600
December	1st to 10th	Night	13% 5% 2 4 3 3 3 2 4 5% 56%	4250
	11th to 20th	Night	19% 6% 2 5% 3 3 3 3 4 5% 47%	4822
	21st to end	Night	21% 7% 2 5% 4 4 3 3 4 5% 42%	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	25% 25% 2 16% 25% 7%	4057
	11th to 20th	Day	22% 25% 2 14% 28% 9%	4060
	21st to end	Day	30% 28% 2 14% 16% 10%	4466
February	1st to 10th	Day	16% 62% 3 10% 6% 3	1910
	11th to 20th	Day	18% 61% 2 8% 9% 2	1958
	21st to end	Day	18% 61% 2 6% 9% 5%	1660
March	1st to 10th	Day	39% 29% 4 7% 17% 5%	4935
	11th to 20th	Day	19% 28% 4 12% 18% 19%	4980
	21st to end	Day	32% 27% 2 14% 17% 8%	5465
April	1st to 10th	Day	14% 61% 4 9% 9% 4	2200
	11th to 20th	Day	15% 62% 4 9% 6% 3	2279
	21st to end	Day	13% 62% 4 11% 8% 2	2596
May	1st to 10th	Day	31% 29% 12% 19% 7% 1	5897
	11th to 20th	Day	38% 30% 11% 14% 7%	5865
	21st to end	Day	28% 28% 10% 13% 18% 2	6447
June	1st to 10th	Day	17% 63% 7% 8% 4 1	2600
	11th to 20th	Day	10% 63% 9% 11% 6% 1	2600
	21st to end	Day	13% 63% 9% 11% 4	2600
July	1st to 10th	Day	36% 31% 15% 16% 2	5835
	11th to 20th	Day	22% 35% 26% 15% 1	5831
	21st to end	Day	33% 34% 15% 13% 5%	6240
August	1st to 10th	Day	37% 40% 14% 8% 1	4143
	11th to 20th	Day	20% 41% 10% 18% 11% 1	4083
	21st to end	Day	11% 38% 9% 29% 12% 1	4072
September	1st to 10th	Day	14% 61% 8% 8% 7% 2	2090
	11th to 20th	Day	18% 60% 5% 9% 7% 2	2090
	21st to end	Day	18% 60% 6% 8% 6% 1	2090
October	1st to 10th	Day	20% 37% 3 9% 24% 7%	3394
	11th to 20th	Day	6% 36% 2 8% 20% 28%	3140
	21st to end	Day	12% 36% 2 16% 23% 10%	3428
November	1st to 10th	Day	19% 55% 4 7% 10% 5%	1957
	11th to 20th	Day	18% 56% 3 9% 10% 4	1835
	21st to end	Day	14% 56% 4 10% 11% 4	1800
December	1st to 10th	Day	23% 36% 3 11% 21% 6%	2930
	11th to 20th	Day	26% 32% 5% 16% 17% 4	3370
	21st to end	Day	33% 25% 4 18% 19% 1	4466
January	1st to 10th	Night	23% 25% 2 13% 29% 7%	5889
	11th to 20th	Night	26% 25% 2 14% 26% 6%	5900
	21st to end	Night	31% 27% 3 9% 23% 7%	6490
February	1st to 10th	Night	13% 61% 4 10% 9% 3	2485
	11th to 20th	Night	20% 60% 2 8% 8% 2	2339
	21st to end	Night	17% 61% 3 6% 6% 7%	1970
March	1st to 10th	Night	38% 28% 5% 9% 15% 5%	4918
	11th to 20th	Night	20% 28% 3 8% 23% 18%	4980
	21st to end	Night	27% 28% 4 13% 16% 12%	5467
April	1st to 10th	Night	16% 62% 4 7% 7% 5%	2200
	11th to 20th	Night	15% 62% 3 10% 6% 4	2069
	21st to end	Night	12% 62% 5% 12% 7% 2	1819
May	1st to 10th	Night	31% 30% 11% 20% 8% 1	4060
	11th to 20th	Night	34% 29% 14% 14% 8%	4033
	21st to end	Night	25% 29% 9% 17% 17% 2	4429
June	1st to 10th	Night	19% 63% 7% 7% 4 1	1800
	11th to 20th	Night	13% 62% 10% 8% 6% 1	1800
	21st to end	Night	12% 64% 10% 9% 4	1800
July	1st to 10th	Night	41% 32% 16% 11% 1	4015
	11th to 20th	Night	27% 36% 25% 11% 1	4006
	21st to end	Night	40% 32% 13% 11% 3	4297
August	1st to 10th	Night	40% 40% 12% 7% 1	2850
	11th to 20th	Night	22% 41% 14% 16% 6% 1	2812
	21st to end	Night	10% 37% 11% 28% 11% 1	3547
September	1st to 10th	Night	14% 61% 9% 8% 6% 2	2090
	11th to 20th	Night	19% 60% 4 9% 6% 1	2090
	21st to end	Night	17% 60% 7% 9% 6% 1	2090
October	1st to 10th	Night	22% 38% 5% 10% 20% 6%	3565
	11th to 20th	Night	7% 36% 2 8% 15% 32%	3779
	21st to end	Night	12% 36% 3 12% 23% 14%	4120
November	1st to 10th	Night	19% 56% 4 7% 11% 4	2341
	11th to 20th	Night	18% 56% 2 7% 11% 6%	2560
	21st to end	Night	14% 57% 4 9% 12% 4	2600
December	1st to 10th	Night	21% 35% 3 10% 26% 6%	4250
	11th to 20th	Night	28% 31% 7% 14% 14% 6%	4824
	21st to end	Night	35% 25% 3 17% 19% 1	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	18% 20% 43% 16% 3	300
	11th to 20th	Day	20% 19% 33% 23% 5% 1	300
	21st to end	Day	22% 24% 35% 15% 3 1	330
February	1st to 10th	Day	19% 17% 42% 18% 5%	300
	11th to 20th	Day	32% 17% 34% 15% 2	300
	21st to end	Day	24% 18% 36% 17% 5%	259
March	1st to 10th	Day	20% 14% 31% 25% 10%	500
	11th to 20th	Day	17% 12% 40% 23% 8% 1	500
	21st to end	Day	18% 13% 38% 22% 9% 1	550
April	1st to 10th	Day	14% 17% 29% 27% 13% 1	500
	11th to 20th	Day	13% 11% 27% 27% 17% 5%	492
	21st to end	Day	11% 10% 24% 28% 21% 7%	500
May	1st to 10th	Day	10% 12% 25% 28% 19% 6%	503
	11th to 20th	Day	14% 5% 18% 30% 21% 12%	527
	21st to end	Day	16% 4 14% 24% 25% 16%	573
June	1st to 10th	Day	13% 3 13% 28% 28% 15%	530
	11th to 20th	Day	7% 3 14% 25% 27% 24%	530
	21st to end	Day	7% 2 11% 30% 27% 23%	530
July	1st to 10th	Day	9% 2 7% 21% 30% 30%	525
	11th to 20th	Day	7% 1 4 20% 38% 29%	524
	21st to end	Day	6% 2 6% 24% 36% 25%	576
August	1st to 10th	Day	13% 3 9% 23% 33% 19%	502
	11th to 20th	Day	12% 3 6% 21% 36% 23%	479
	21st to end	Day	12% 3 9% 24% 29% 23%	539
September	1st to 10th	Day	10% 4 9% 28% 30% 20%	490
	11th to 20th	Day	18% 3 11% 24% 31% 12%	490
	21st to end	Day	18% 2 16% 26% 26% 12%	490
October	1st to 10th	Day	16% 3 19% 32% 22% 8%	490
	11th to 20th	Day	10% 6% 20% 30% 24% 10%	490
	21st to end	Day	14% 7% 22% 29% 23% 5%	539
November	1st to 10th	Day	20% 4 24% 27% 19% 5%	495
	11th to 20th	Day	20% 9% 38% 21% 10% 2	335
	21st to end	Day	12% 13% 34% 26% 13% 2	300
December	1st to 10th	Day	24% 14% 35% 19% 7% 1	300
	11th to 20th	Day	19% 13% 41% 16% 10% 2	300
	21st to end	Day	29% 13% 32% 18% 6% 2	330
January	1st to 10th	Night	20% 12% 33% 29% 6%	800
	11th to 20th	Night	18% 10% 32% 33% 7%	800
	21st to end	Night	21% 9% 38% 28% 4	880
February	1st to 10th	Night	18% 9% 33% 33% 7%	800
	11th to 20th	Night	23% 10% 34% 30% 3	783
	21st to end	Night	17% 14% 34% 31% 4	660
March	1st to 10th	Night	17% 9% 33% 35% 7%	800
	11th to 20th	Night	15% 9% 36% 31% 8% 1	800
	21st to end	Night	16% 10% 35% 30% 9%	880
April	1st to 10th	Night	13% 11% 33% 33% 11%	800
	11th to 20th	Night	14% 10% 28% 33% 15%	791
	21st to end	Night	10% 5% 23% 44% 18% 1	619
May	1st to 10th	Night	10% 5% 26% 39% 19% 1	600
	11th to 20th	Night	11% 3 22% 40% 19% 4	591
	21st to end	Night	12% 2 10% 36% 36% 4	650
June	1st to 10th	Night	14% 2 12% 37% 31% 5%	600
	11th to 20th	Night	9% 2 12% 31% 36% 11%	600
	21st to end	Night	8% 3 9% 31% 45% 6%	600
July	1st to 10th	Night	11% 2 6% 31% 42% 9%	585
	11th to 20th	Night	8% 2 3 26% 52% 9%	582
	21st to end	Night	9% 2 5% 32% 44% 8%	657
August	1st to 10th	Night	11% 2 7% 28% 43% 9%	579
	11th to 20th	Night	13% 3 4 30% 42% 8%	564
	21st to end	Night	13% 2 9% 27% 42% 8%	745
September	1st to 10th	Night	10% 2 9% 31% 41% 6%	760
	11th to 20th	Night	15% 3 10% 29% 39% 4	760
	21st to end	Night	16% 2 12% 32% 34% 4	760
October	1st to 10th	Night	15% 2 16% 35% 27% 5%	760
	11th to 20th	Night	13% 4 21% 34% 25% 4	760
	21st to end	Night	12% 5% 22% 35% 25% 2	836
November	1st to 10th	Night	14% 6% 22% 34% 21% 4	780
	11th to 20th	Night	17% 7% 28% 33% 14% 1	800
	21st to end	Night	15% 8% 27% 33% 17% 1	800
December	1st to 10th	Night	18% 7% 30% 33% 10% 1	800
	11th to 20th	Night	20% 6% 28% 32% 14% 1	800
	21st to end	Night	26% 9% 26% 31% 8%	880

Page generated at 2025-08-02 01:32:28. Version ac07

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