Oconee Observing Field
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Oconee Observing Field clear sky chart from 2005-11-06 to 2026-02-01.

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% 43%	127372
	Night	13% 6% 2 6% 4 4 4 4 6% 8% 45%	124661
Transparency	Day	37% 7% 12% 20% 18% 6%	131122
	Night	36% 6% 11% 19% 20% 8%	128980
Seeing	Day	16% 9% 24% 24% 19% 8%	16683
	Night	15% 9% 23% 30% 20% 3	26768

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% 6% 2 4 3 3 3 3 5% 5% 50%	4146
	11th to 20th	Day	12% 6% 3 4 3 2 3 2 5% 6% 55%	4150
	21st to end	Day	20% 6% 2 7% 4 3 3 2 4 5% 43%	4587
February	1st to 10th	Day	16% 7% 2 7% 4 4 5% 3 5% 7% 41%	2000
	11th to 20th	Day	22% 7% 2 4 4 2 3 2 5% 4 44%	1948
	21st to end	Day	18% 6% 2 5% 4 4 4 4 5% 6% 42%	1650
March	1st to 10th	Day	21% 7% 3 7% 4 4 4 3 4 5% 38%	4797
	11th to 20th	Day	9% 4 2 5% 3 4 4 4 5% 7% 54%	4980
	21st to end	Day	16% 7% 2 6% 4 4 4 3 3 4 46%	5465
April	1st to 10th	Day	12% 4 2 6% 5% 4 3 4 5% 5% 50%	2200
	11th to 20th	Day	11% 5% 2 5% 5% 4 4 3 5% 7% 50%	2318
	21st to end	Day	8% 5% 2 5% 4 5% 4 4 5% 8% 51%	2600
May	1st to 10th	Day	12% 6% 2 6% 4 4 5% 4 6% 9% 41%	5862
	11th to 20th	Day	17% 8% 3 7% 4 5% 6% 5% 6% 9% 31%	5861
	21st to end	Day	10% 6% 2 6% 5% 5% 5% 4 6% 8% 44%	6433
June	1st to 10th	Day	10% 5% 3 7% 6% 7% 6% 5% 9% 10% 34%	2600
	11th to 20th	Day	6% 4 2 6% 4 5% 6% 5% 8% 12% 43%	2600
	21st to end	Day	5% 4 2 6% 6% 6% 7% 6% 9% 11% 38%	2600
July	1st to 10th	Day	8% 6% 3 8% 6% 6% 7% 6% 9% 11% 30%	5900
	11th to 20th	Day	4 4 2 6% 6% 6% 6% 6% 10% 13% 37%	5900
	21st to end	Day	7% 6% 3 9% 7% 7% 8% 6% 9% 12% 27%	6424
August	1st to 10th	Day	14% 5% 2 7% 5% 6% 7% 5% 9% 12% 28%	4234
	11th to 20th	Day	7% 4 2 6% 5% 5% 6% 4 7% 10% 44%	4084
	21st to end	Day	8% 4 2 5% 4 5% 5% 4 7% 9% 47%	4187
September	1st to 10th	Day	10% 5% 2 6% 5% 5% 6% 4 7% 9% 40%	2200
	11th to 20th	Day	14% 5% 2 6% 4 4 5% 4 6% 8% 42%	2200
	21st to end	Day	14% 7% 2 6% 4 4 4 3 5% 7% 45%	2200
October	1st to 10th	Day	12% 6% 2 5% 3 3 3 3 5% 7% 50%	2200
	11th to 20th	Day	13% 4 1 3 3 3 3 3 4 5% 58%	2024
	21st to end	Day	12% 4 2 5% 3 4 3 3 4 5% 56%	2200
November	1st to 10th	Day	12% 5% 3 5% 3 3 4 3 4 5% 54%	1994
	11th to 20th	Day	14% 5% 1 4 3 3 2 3 4 6% 56%	1890
	21st to end	Day	13% 6% 2 5% 3 4 4 3 5% 7% 49%	1890
December	1st to 10th	Day	14% 7% 2 6% 4 4 3 3 5% 5% 47%	3020
	11th to 20th	Day	16% 7% 2 5% 4 3 3 3 5% 6% 47%	3463
	21st to end	Day	22% 6% 3 5% 2 3 3 2 4 6% 44%	4565
January	1st to 10th	Night	13% 6% 2 4 3 3 3 3 4 6% 53%	6019
	11th to 20th	Night	13% 6% 2 5% 3 3 4 4 5% 6% 49%	6030
	21st to end	Night	17% 9% 2 5% 4 3 3 3 4 6% 43%	6609
February	1st to 10th	Night	16% 6% 2 6% 4 3 4 3 5% 5% 46%	2401
	11th to 20th	Night	20% 7% 2 5% 4 3 4 3 4 6% 43%	2338
	21st to end	Night	15% 6% 2 6% 4 4 4 3 4 6% 46%	1980
March	1st to 10th	Night	20% 8% 3 6% 4 3 4 4 5% 6% 38%	5055
	11th to 20th	Night	10% 4 1 3 3 3 4 4 6% 8% 54%	4980
	21st to end	Night	16% 5% 2 5% 4 4 4 3 5% 6% 47%	5467
April	1st to 10th	Night	12% 4 2 5% 4 3 4 4 5% 7% 49%	2200
	11th to 20th	Night	12% 5% 2 4 3 4 3 3 5% 8% 53%	2043
	21st to end	Night	8% 4 1 5% 4 4 5% 4 6% 7% 53%	1800
May	1st to 10th	Night	10% 5% 2 7% 5% 5% 5% 4 7% 10% 41%	4033
	11th to 20th	Night	18% 4 2 6% 4 5% 5% 5% 7% 9% 35%	4032
	21st to end	Night	11% 5% 2 5% 4 4 4 4 7% 9% 46%	4421
June	1st to 10th	Night	9% 7% 3 6% 5% 5% 6% 5% 7% 11% 36%	1800
	11th to 20th	Night	5% 5% 2 5% 6% 5% 5% 4 8% 12% 43%	1800
	21st to end	Night	6% 5% 1 6% 4 6% 6% 6% 9% 12% 39%	1800
July	1st to 10th	Night	10% 7% 3 9% 6% 6% 6% 5% 8% 11% 29%	4058
	11th to 20th	Night	4 4 2 7% 6% 6% 7% 6% 11% 15% 32%	4057
	21st to end	Night	9% 7% 3 9% 6% 6% 7% 5% 8% 12% 27%	4427
August	1st to 10th	Night	13% 6% 2 8% 5% 7% 6% 6% 8% 12% 26%	2915
	11th to 20th	Night	7% 5% 2 6% 5% 5% 5% 4 8% 10% 42%	2961
	21st to end	Night	7% 5% 2 5% 4 5% 4 4 8% 9% 48%	3675
September	1st to 10th	Night	10% 5% 2 7% 5% 5% 6% 5% 7% 10% 39%	2200
	11th to 20th	Night	12% 6% 3 7% 5% 5% 4 4 6% 7% 43%	2200
	21st to end	Night	12% 5% 2 6% 4 4 4 4 5% 6% 47%	2200
October	1st to 10th	Night	12% 5% 2 5% 3 3 4 3 5% 6% 52%	2200
	11th to 20th	Night	12% 3 2 4 3 3 3 2 3 5% 59%	2375
	21st to end	Night	11% 3 2 5% 3 4 3 3 4 5% 57%	2640
November	1st to 10th	Night	10% 6% 2 6% 3 3 3 3 5% 6% 54%	2520
	11th to 20th	Night	14% 5% 2 5% 3 3 3 2 4 5% 55%	2730
	21st to end	Night	13% 5% 2 5% 4 4 4 3 5% 5% 50%	2730
December	1st to 10th	Night	14% 6% 2 4 3 3 3 3 4 5% 54%	4380
	11th to 20th	Night	16% 6% 2 5% 3 3 3 3 5% 7% 48%	4952
	21st to end	Night	20% 7% 2 6% 4 3 4 3 4 5% 42%	6633

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% 3 6% 19% 28% 8%	4147
	11th to 20th	Day	32% 3 4 18% 31% 13%	4150
	21st to end	Day	45% 3 4 18% 21% 9%	4587
February	1st to 10th	Day	43% 4 8% 19% 18% 7%	2000
	11th to 20th	Day	43% 3 5% 20% 22% 6%	1958
	21st to end	Day	42% 5% 7% 15% 23% 9%	1650
March	1st to 10th	Day	49% 3 6% 11% 24% 7%	4797
	11th to 20th	Day	29% 5% 8% 15% 22% 21%	4980
	21st to end	Day	42% 4 5% 20% 20% 9%	5465
April	1st to 10th	Day	35% 4 10% 22% 20% 8%	2200
	11th to 20th	Day	33% 5% 9% 20% 23% 10%	2318
	21st to end	Day	30% 6% 12% 25% 24% 4	2600
May	1st to 10th	Day	39% 7% 16% 23% 14% 2	5897
	11th to 20th	Day	48% 8% 15% 18% 10% 1	5865
	21st to end	Day	37% 7% 13% 21% 20% 2	6447
June	1st to 10th	Day	42% 10% 16% 19% 12% 2	2600
	11th to 20th	Day	31% 10% 18% 25% 14% 1	2600
	21st to end	Day	35% 12% 18% 19% 13% 3	2600
July	1st to 10th	Day	41% 13% 19% 21% 5% 1	5835
	11th to 20th	Day	32% 14% 29% 21% 3 1	5831
	21st to end	Day	44% 15% 18% 19% 3	6240
August	1st to 10th	Day	45% 10% 18% 24% 3	4221
	11th to 20th	Day	32% 10% 17% 26% 14% 1	4123
	21st to end	Day	32% 8% 16% 26% 15% 3	4187
September	1st to 10th	Day	38% 8% 14% 18% 17% 4	2200
	11th to 20th	Day	40% 7% 10% 20% 20% 2	2200
	21st to end	Day	39% 7% 11% 20% 19% 5%	2200
October	1st to 10th	Day	31% 3 7% 14% 32% 12%	3590
	11th to 20th	Day	18% 2 5% 16% 28% 31%	3277
	21st to end	Day	24% 3 3 21% 35% 14%	3538
November	1st to 10th	Day	33% 4 8% 15% 27% 13%	1994
	11th to 20th	Day	31% 3 7% 21% 26% 12%	1890
	21st to end	Day	35% 5% 8% 19% 26% 7%	1890
December	1st to 10th	Day	39% 4 5% 16% 25% 10%	3020
	11th to 20th	Day	39% 3 9% 20% 21% 7%	3460
	21st to end	Day	42% 3 7% 22% 23% 3	4565
January	1st to 10th	Night	32% 4 5% 20% 30% 8%	6019
	11th to 20th	Night	35% 3 5% 19% 28% 10%	6030
	21st to end	Night	43% 3 4 14% 27% 7%	6609
February	1st to 10th	Night	39% 4 8% 18% 20% 10%	2401
	11th to 20th	Night	43% 4 5% 17% 21% 9%	2339
	21st to end	Night	40% 5% 7% 16% 20% 13%	1980
March	1st to 10th	Night	46% 4 9% 14% 18% 9%	5055
	11th to 20th	Night	28% 4 8% 13% 27% 20%	4980
	21st to end	Night	38% 4 6% 19% 20% 13%	5467
April	1st to 10th	Night	34% 5% 10% 20% 22% 10%	2200
	11th to 20th	Night	31% 4 7% 24% 23% 11%	2043
	21st to end	Night	29% 7% 11% 25% 22% 7%	1800
May	1st to 10th	Night	37% 9% 15% 23% 13% 3	4060
	11th to 20th	Night	44% 9% 16% 20% 11% 1	4033
	21st to end	Night	32% 7% 14% 23% 20% 3	4429
June	1st to 10th	Night	39% 10% 18% 18% 13% 1	1800
	11th to 20th	Night	31% 10% 19% 25% 12% 2	1800
	21st to end	Night	32% 12% 20% 19% 13% 4	1800
July	1st to 10th	Night	45% 12% 21% 17% 4 1	4015
	11th to 20th	Night	36% 14% 28% 18% 3 1	4006
	21st to end	Night	46% 15% 18% 16% 4 1	4297
August	1st to 10th	Night	46% 11% 20% 19% 3	2904
	11th to 20th	Night	34% 10% 21% 22% 11% 2	2988
	21st to end	Night	30% 8% 16% 27% 17% 2	3675
September	1st to 10th	Night	37% 11% 16% 17% 14% 5%	2200
	11th to 20th	Night	39% 7% 13% 18% 18% 5%	2200
	21st to end	Night	37% 6% 12% 18% 21% 6%	2200
October	1st to 10th	Night	33% 3 9% 13% 33% 10%	3590
	11th to 20th	Night	18% 2 4 15% 27% 33%	3861
	21st to end	Night	21% 3 5% 19% 33% 19%	4252
November	1st to 10th	Night	32% 4 8% 16% 26% 14%	2520
	11th to 20th	Night	33% 3 6% 17% 27% 14%	2730
	21st to end	Night	36% 4 7% 17% 26% 10%	2730
December	1st to 10th	Night	34% 4 6% 18% 31% 7%	4380
	11th to 20th	Night	38% 3 12% 17% 22% 8%	4954
	21st to end	Night	44% 3 5% 23% 21% 3	6633

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	24% 24% 38% 12% 3	330
	11th to 20th	Day	25% 23% 33% 12% 6% 1	330
	21st to end	Day	27% 26% 33% 11% 3	363
February	1st to 10th	Day	25% 17% 39% 15% 4	300
	11th to 20th	Day	38% 16% 33% 11% 1	300
	21st to end	Day	28% 19% 39% 10% 4	249
March	1st to 10th	Day	23% 19% 28% 23% 6% 1	435
	11th to 20th	Day	22% 14% 37% 19% 7% 1	500
	21st to end	Day	21% 18% 33% 21% 7% 1	550
April	1st to 10th	Day	21% 15% 30% 24% 9% 1	500
	11th to 20th	Day	13% 16% 30% 25% 13% 3	492
	21st to end	Day	12% 10% 27% 30% 18% 3	500
May	1st to 10th	Day	14% 12% 28% 27% 13% 6%	503
	11th to 20th	Day	16% 5% 23% 28% 21% 7%	527
	21st to end	Day	14% 5% 20% 29% 21% 11%	573
June	1st to 10th	Day	13% 3 18% 31% 24% 11%	530
	11th to 20th	Day	6% 4 17% 29% 26% 18%	530
	21st to end	Day	7% 2 15% 29% 28% 18%	530
July	1st to 10th	Day	6% 2 11% 26% 33% 22%	525
	11th to 20th	Day	7% 2 7% 22% 42% 20%	524
	21st to end	Day	6% 2 10% 26% 38% 17%	576
August	1st to 10th	Day	14% 3 16% 23% 29% 15%	526
	11th to 20th	Day	10% 2 10% 27% 33% 19%	519
	21st to end	Day	15% 2 12% 26% 28% 16%	583
September	1st to 10th	Day	11% 5% 14% 29% 28% 13%	530
	11th to 20th	Day	16% 2 14% 28% 28% 11%	530
	21st to end	Day	15% 6% 17% 28% 24% 9%	530
October	1st to 10th	Day	17% 5% 25% 29% 18% 7%	530
	11th to 20th	Day	14% 8% 22% 28% 20% 6%	530
	21st to end	Day	15% 10% 27% 27% 17% 4	583
November	1st to 10th	Day	17% 9% 28% 26% 17% 3	472
	11th to 20th	Day	18% 13% 38% 24% 6% 2	330
	21st to end	Day	16% 15% 33% 25% 8% 2	330
December	1st to 10th	Day	28% 17% 34% 15% 6% 1	330
	11th to 20th	Day	27% 13% 36% 17% 7%	330
	21st to end	Day	28% 15% 34% 16% 6% 1	363
January	1st to 10th	Night	23% 18% 33% 21% 5%	840
	11th to 20th	Night	21% 17% 31% 25% 6%	840
	21st to end	Night	22% 18% 34% 24% 3	924
February	1st to 10th	Night	20% 15% 30% 30% 6%	801
	11th to 20th	Night	24% 16% 32% 24% 3	783
	21st to end	Night	19% 15% 37% 27% 3	660
March	1st to 10th	Night	17% 17% 30% 31% 5%	800
	11th to 20th	Night	17% 14% 33% 27% 9% 1	800
	21st to end	Night	17% 14% 33% 27% 8%	880
April	1st to 10th	Night	16% 15% 31% 27% 11%	800
	11th to 20th	Night	16% 12% 27% 31% 14% 1	690
	21st to end	Night	9% 7% 28% 40% 16% 1	600
May	1st to 10th	Night	9% 7% 26% 40% 16% 2	600
	11th to 20th	Night	12% 3 23% 36% 22% 4	591
	21st to end	Night	12% 2 16% 34% 30% 6%	650
June	1st to 10th	Night	10% 3 12% 41% 31% 4	600
	11th to 20th	Night	6% 3 15% 32% 34% 10%	600
	21st to end	Night	7% 2 9% 37% 39% 7%	600
July	1st to 10th	Night	8% 2 8% 29% 39% 13%	585
	11th to 20th	Night	7% 2 7% 27% 46% 12%	582
	21st to end	Night	6% 2 9% 28% 48% 7%	657
August	1st to 10th	Night	11% 1 8% 32% 39% 9%	597
	11th to 20th	Night	11% 1 10% 26% 41% 9%	594
	21st to end	Night	14% 2 10% 29% 37% 8%	710
September	1st to 10th	Night	11% 2 12% 32% 36% 7%	800
	11th to 20th	Night	14% 3 12% 31% 36% 5%	800
	21st to end	Night	14% 4 16% 32% 31% 4	800
October	1st to 10th	Night	14% 4 18% 35% 24% 5%	800
	11th to 20th	Night	13% 7% 23% 31% 23% 3	800
	21st to end	Night	14% 8% 23% 33% 20% 2	880
November	1st to 10th	Night	12% 9% 22% 36% 19% 2	820
	11th to 20th	Night	17% 11% 27% 31% 13% 1	840
	21st to end	Night	15% 12% 30% 29% 14% 1	840
December	1st to 10th	Night	20% 14% 26% 30% 8% 1	840
	11th to 20th	Night	20% 13% 26% 29% 11%	840
	21st to end	Night	26% 14% 25% 29% 7%	924

Page generated at 2026-01-29 01:21:44. Version ac07

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