Ragland Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ragland Observatory clear sky chart from 2005-11-06 to 2025-10-04.

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	13% 6% 2 6% 4 4 4 4 6% 8% 43%	126076
	Night	14% 6% 2 6% 4 4 4 3 5% 7% 44%	123289
Transparency	Day	37% 7% 13% 22% 17% 4	129677
	Night	38% 6% 11% 22% 19% 5%	127758
Seeing	Day	18% 12% 27% 25% 14% 5%	16331
	Night	17% 11% 29% 30% 12% 1	25979

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 2 4 3 3 3 3 4 5% 54%	3992
	11th to 20th	Day	13% 7% 2 4 3 3 3 3 4 5% 52%	4060
	21st to end	Day	14% 7% 3 7% 5% 4 3 4 4 5% 45%	4466
February	1st to 10th	Day	13% 7% 2 7% 5% 4 4 4 6% 7% 40%	1800
	11th to 20th	Day	21% 7% 2 4 3 3 3 4 6% 5% 42%	1817
	21st to end	Day	18% 7% 2 6% 5% 4 5% 3 5% 6% 39%	1662
March	1st to 10th	Day	17% 7% 3 7% 4 4 4 4 5% 6% 38%	4935
	11th to 20th	Day	10% 5% 2 4 3 3 4 4 5% 7% 52%	4980
	21st to end	Day	16% 6% 2 7% 5% 4 4 3 5% 6% 43%	5499
April	1st to 10th	Day	11% 6% 1 5% 4 3 4 3 6% 7% 50%	2400
	11th to 20th	Day	11% 6% 2 5% 4 4 4 4 4 8% 48%	2374
	21st to end	Day	15% 6% 2 7% 4 4 4 4 5% 6% 43%	2400
May	1st to 10th	Day	13% 8% 3 7% 5% 5% 5% 5% 7% 10% 33%	5698
	11th to 20th	Day	19% 8% 3 7% 5% 4 4 4 7% 9% 31%	5861
	21st to end	Day	14% 5% 2 5% 4 4 5% 4 6% 9% 42%	6930
June	1st to 10th	Day	10% 4 2 5% 5% 5% 6% 4 7% 10% 42%	2800
	11th to 20th	Day	11% 4 2 6% 5% 4 5% 5% 7% 10% 41%	2800
	21st to end	Day	8% 4 2 6% 5% 5% 5% 4 8% 10% 43%	2800
July	1st to 10th	Day	6% 5% 2 6% 5% 5% 5% 5% 8% 12% 40%	6232
	11th to 20th	Day	10% 6% 3 8% 6% 6% 6% 5% 9% 13% 28%	5900
	21st to end	Day	7% 5% 2 6% 5% 5% 5% 5% 8% 11% 41%	6424
August	1st to 10th	Day	15% 8% 3 7% 5% 5% 5% 5% 7% 11% 29%	4234
	11th to 20th	Day	9% 6% 3 8% 5% 5% 6% 5% 8% 9% 37%	3977
	21st to end	Day	8% 5% 2 5% 3 4 4 4 6% 11% 49%	4312
September	1st to 10th	Day	13% 5% 2 5% 4 4 4 4 6% 9% 45%	2400
	11th to 20th	Day	12% 7% 2 7% 3 3 4 4 5% 8% 46%	2400
	21st to end	Day	20% 7% 2 6% 4 4 4 3 5% 7% 36%	2088
October	1st to 10th	Day	16% 5% 2 5% 4 4 3 3 4 5% 48%	1930
	11th to 20th	Day	16% 4 2 4 3 4 3 3 4 5% 53%	1900
	21st to end	Day	13% 5% 2 4 4 3 3 2 4 5% 54%	2090
November	1st to 10th	Day	13% 4 2 5% 4 3 4 3 4 5% 54%	1948
	11th to 20th	Day	14% 6% 2 5% 3 3 4 3 5% 6% 49%	1800
	21st to end	Day	14% 5% 2 5% 3 3 4 3 4 6% 52%	1617
December	1st to 10th	Day	11% 5% 2 5% 3 3 3 3 5% 6% 52%	2600
	11th to 20th	Day	17% 7% 2 5% 3 3 3 2 4 6% 47%	2990
	21st to end	Day	14% 6% 2 6% 4 4 4 3 5% 7% 45%	3960
January	1st to 10th	Night	14% 6% 2 5% 3 3 3 3 4 5% 54%	5935
	11th to 20th	Night	14% 6% 2 5% 3 3 3 2 4 4 54%	5900
	21st to end	Night	17% 7% 2 5% 3 3 3 3 4 5% 50%	6490
February	1st to 10th	Night	16% 6% 2 6% 4 3 4 4 6% 6% 43%	2600
	11th to 20th	Night	19% 7% 2 7% 4 3 3 2 4 6% 42%	2468
	21st to end	Night	16% 6% 2 6% 4 4 3 2 4 6% 46%	1965
March	1st to 10th	Night	17% 6% 2 5% 4 3 3 3 5% 6% 46%	4918
	11th to 20th	Night	13% 4 2 5% 3 3 3 3 5% 7% 51%	4980
	21st to end	Night	13% 7% 2 6% 4 4 4 3 4 6% 47%	5432
April	1st to 10th	Night	13% 8% 2 6% 5% 4 3 3 5% 7% 44%	2000
	11th to 20th	Night	10% 7% 2 5% 3 4 4 3 5% 6% 49%	1975
	21st to end	Night	14% 6% 2 7% 4 4 3 3 5% 7% 45%	2000
May	1st to 10th	Night	14% 8% 2 7% 6% 5% 5% 4 7% 9% 33%	4225
	11th to 20th	Night	21% 8% 3 7% 4 4 4 4 5% 7% 32%	4032
	21st to end	Night	14% 7% 2 7% 5% 5% 4 3 6% 9% 39%	3920
June	1st to 10th	Night	10% 6% 2 6% 5% 5% 6% 4 8% 9% 40%	1600
	11th to 20th	Night	10% 5% 2 7% 5% 4 5% 5% 7% 9% 40%	1600
	21st to end	Night	8% 5% 2 5% 4 4 5% 5% 7% 10% 44%	1600
July	1st to 10th	Night	9% 5% 3 7% 5% 5% 5% 5% 7% 9% 38%	3708
	11th to 20th	Night	11% 8% 3 8% 6% 6% 6% 5% 8% 10% 29%	4057
	21st to end	Night	8% 7% 2 9% 6% 6% 7% 6% 7% 8% 34%	4427
August	1st to 10th	Night	16% 8% 4 7% 5% 5% 4 4 6% 10% 31%	2915
	11th to 20th	Night	9% 7% 2 6% 5% 5% 5% 5% 8% 10% 38%	3038
	21st to end	Night	9% 5% 2 5% 4 4 5% 3 6% 8% 47%	3586
September	1st to 10th	Night	12% 6% 3 5% 5% 5% 4 3 5% 9% 44%	2000
	11th to 20th	Night	13% 5% 1 5% 5% 5% 3 4 5% 6% 46%	2000
	21st to end	Night	21% 9% 3 7% 4 3 3 3 5% 6% 35%	2306
October	1st to 10th	Night	15% 5% 2 7% 3 4 4 3 4 5% 48%	2317
	11th to 20th	Night	16% 5% 2 5% 4 3 3 3 4 6% 49%	2280
	21st to end	Night	14% 5% 2 4 4 2 4 2 5% 6% 52%	2508
November	1st to 10th	Night	13% 6% 2 5% 4 3 3 3 4 5% 51%	2346
	11th to 20th	Night	15% 6% 2 5% 3 3 3 3 5% 5% 49%	2600
	21st to end	Night	13% 5% 2 4 3 3 4 3 5% 6% 51%	2780
December	1st to 10th	Night	10% 5% 2 4 3 4 4 3 5% 6% 55%	4580
	11th to 20th	Night	20% 7% 3 7% 4 4 4 2 4 6% 40%	5205
	21st to end	Night	14% 8% 2 6% 3 3 3 4 5% 7% 46%	6996

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	33% 3 6% 25% 24% 9%	3993
	11th to 20th	Day	34% 5% 7% 19% 27% 9%	4060
	21st to end	Day	41% 5% 8% 25% 17% 3	4466
February	1st to 10th	Day	41% 6% 11% 25% 14% 3	1800
	11th to 20th	Day	42% 4 9% 21% 19% 4	1826
	21st to end	Day	46% 6% 10% 16% 18% 5%	1662
March	1st to 10th	Day	44% 5% 8% 17% 18% 8%	4935
	11th to 20th	Day	31% 5% 9% 23% 23% 10%	4980
	21st to end	Day	42% 6% 10% 18% 19% 6%	5499
April	1st to 10th	Day	32% 6% 12% 23% 19% 8%	2400
	11th to 20th	Day	35% 5% 11% 21% 22% 6%	2374
	21st to end	Day	40% 6% 12% 22% 16% 5%	2400
May	1st to 10th	Day	43% 11% 16% 18% 11% 1	5731
	11th to 20th	Day	47% 8% 14% 20% 11% 1	5865
	21st to end	Day	37% 8% 15% 22% 17% 2	6945
June	1st to 10th	Day	34% 9% 17% 24% 15% 1	2800
	11th to 20th	Day	35% 11% 16% 22% 16% 1	2800
	21st to end	Day	32% 11% 16% 24% 15% 2	2800
July	1st to 10th	Day	34% 10% 20% 18% 14% 4	6164
	11th to 20th	Day	44% 12% 23% 16% 5% 1	5831
	21st to end	Day	35% 9% 15% 22% 19%	6240
August	1st to 10th	Day	47% 8% 16% 22% 6%	4221
	11th to 20th	Day	39% 9% 15% 24% 13%	4016
	21st to end	Day	29% 7% 15% 28% 19% 1	4312
September	1st to 10th	Day	35% 9% 15% 16% 21% 4	2400
	11th to 20th	Day	37% 7% 10% 23% 19% 3	2400
	21st to end	Day	48% 6% 11% 18% 14% 3	2088
October	1st to 10th	Day	36% 5% 8% 19% 27% 5%	3190
	11th to 20th	Day	24% 3 6% 20% 33% 13%	3140
	21st to end	Day	20% 4 8% 29% 26% 13%	3428
November	1st to 10th	Day	33% 5% 8% 25% 25% 4	1948
	11th to 20th	Day	35% 5% 10% 21% 22% 7%	1800
	21st to end	Day	34% 5% 7% 25% 24% 5%	1617
December	1st to 10th	Day	32% 4 8% 28% 20% 8%	2600
	11th to 20th	Day	41% 3 12% 23% 16% 5%	2986
	21st to end	Day	37% 6% 13% 27% 16% 1	3960
January	1st to 10th	Night	33% 4 7% 20% 27% 10%	5935
	11th to 20th	Night	33% 4 5% 22% 28% 7%	5900
	21st to end	Night	38% 3 6% 26% 21% 5%	6490
February	1st to 10th	Night	40% 5% 12% 23% 17% 3	2600
	11th to 20th	Night	45% 4 7% 19% 19% 6%	2470
	21st to end	Night	40% 4 9% 21% 18% 8%	1965
March	1st to 10th	Night	38% 5% 7% 20% 22% 8%	4918
	11th to 20th	Night	33% 5% 8% 20% 24% 11%	4980
	21st to end	Night	39% 4 8% 22% 21% 6%	5432
April	1st to 10th	Night	40% 6% 9% 17% 21% 6%	2000
	11th to 20th	Night	34% 6% 10% 22% 22% 6%	1975
	21st to end	Night	38% 6% 12% 23% 17% 5%	2000
May	1st to 10th	Night	45% 9% 17% 17% 11% 1	4255
	11th to 20th	Night	49% 8% 12% 21% 9% 1	4033
	21st to end	Night	41% 8% 14% 24% 13% 1	3927
June	1st to 10th	Night	37% 11% 14% 22% 15% 1	1600
	11th to 20th	Night	36% 11% 17% 19% 15% 1	1600
	21st to end	Night	31% 11% 14% 23% 17% 4	1600
July	1st to 10th	Night	40% 11% 17% 17% 13% 3	3668
	11th to 20th	Night	47% 12% 22% 15% 4 1	4006
	21st to end	Night	44% 10% 12% 19% 15%	4297
August	1st to 10th	Night	47% 8% 16% 22% 6%	2904
	11th to 20th	Night	38% 9% 18% 23% 12%	3065
	21st to end	Night	33% 7% 12% 28% 19% 1	3586
September	1st to 10th	Night	38% 8% 14% 18% 16% 5%	2000
	11th to 20th	Night	37% 7% 11% 23% 20% 2	2000
	21st to end	Night	48% 7% 11% 16% 15% 3	2306
October	1st to 10th	Night	39% 4 11% 17% 23% 5%	3837
	11th to 20th	Night	25% 3 7% 21% 30% 13%	3779
	21st to end	Night	21% 3 6% 31% 26% 13%	4120
November	1st to 10th	Night	35% 5% 10% 21% 24% 5%	2346
	11th to 20th	Night	37% 5% 9% 18% 23% 9%	2600
	21st to end	Night	32% 5% 9% 25% 23% 6%	2780
December	1st to 10th	Night	31% 4 8% 27% 25% 6%	4580
	11th to 20th	Night	46% 4 10% 18% 15% 6%	5208
	21st to end	Night	37% 5% 12% 28% 17% 1	6996

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% 26% 30% 15% 4	287
	11th to 20th	Day	27% 30% 31% 9% 2	300
	21st to end	Day	23% 25% 40% 11% 2	330
February	1st to 10th	Day	21% 27% 38% 12% 2	300
	11th to 20th	Day	35% 23% 30% 10% 1	364
	21st to end	Day	28% 17% 33% 20% 3	414
March	1st to 10th	Day	23% 20% 33% 19% 5%	500
	11th to 20th	Day	23% 23% 34% 15% 5% 1	500
	21st to end	Day	23% 18% 39% 15% 5% 1	550
April	1st to 10th	Day	23% 20% 32% 19% 6%	500
	11th to 20th	Day	17% 14% 33% 25% 7% 4	492
	21st to end	Day	19% 16% 33% 23% 7% 1	500
May	1st to 10th	Day	16% 17% 34% 21% 9% 2	503
	11th to 20th	Day	21% 10% 28% 27% 11% 3	527
	21st to end	Day	20% 6% 24% 28% 18% 5%	573
June	1st to 10th	Day	10% 6% 30% 28% 22% 4	530
	11th to 20th	Day	12% 5% 23% 35% 17% 7%	530
	21st to end	Day	11% 4 22% 35% 22% 6%	530
July	1st to 10th	Day	10% 2 16% 34% 28% 9%	525
	11th to 20th	Day	5% 2 14% 39% 28% 11%	524
	21st to end	Day	9% 2 20% 34% 24% 10%	576
August	1st to 10th	Day	15% 3 19% 30% 26% 6%	526
	11th to 20th	Day	11% 5% 18% 32% 25% 10%	519
	21st to end	Day	8% 4 19% 30% 25% 15%	583
September	1st to 10th	Day	15% 4 18% 27% 22% 14%	530
	11th to 20th	Day	16% 4 18% 29% 22% 12%	530
	21st to end	Day	27% 8% 23% 27% 12% 4	530
October	1st to 10th	Day	20% 6% 22% 26% 19% 8%	502
	11th to 20th	Day	16% 13% 22% 30% 17% 3	490
	21st to end	Day	14% 11% 34% 26% 11% 4	539
November	1st to 10th	Day	17% 10% 32% 24% 14% 3	490
	11th to 20th	Day	18% 15% 33% 22% 12% 1	400
	21st to end	Day	20% 17% 32% 19% 10% 2	217
December	1st to 10th	Day	23% 18% 38% 15% 7%	200
	11th to 20th	Day	22% 18% 34% 18% 9% 1	200
	21st to end	Day	22% 15% 34% 19% 9% 1	220
January	1st to 10th	Night	21% 19% 38% 19% 3	800
	11th to 20th	Night	20% 19% 32% 25% 4	800
	21st to end	Night	20% 16% 40% 23% 1	880
February	1st to 10th	Night	20% 15% 39% 24% 3	800
	11th to 20th	Night	24% 20% 36% 18% 1	783
	21st to end	Night	21% 18% 38% 21% 3	660
March	1st to 10th	Night	19% 17% 37% 25% 3	800
	11th to 20th	Night	22% 18% 35% 21% 5% 1	800
	21st to end	Night	18% 17% 39% 21% 4	880
April	1st to 10th	Night	17% 20% 40% 20% 3	800
	11th to 20th	Night	17% 13% 36% 26% 8%	791
	21st to end	Night	17% 10% 38% 29% 6%	800
May	1st to 10th	Night	16% 11% 34% 31% 7%	691
	11th to 20th	Night	18% 7% 29% 36% 10% 1	591
	21st to end	Night	15% 4 20% 39% 19% 2	433
June	1st to 10th	Night	12% 3 21% 44% 20% 1	400
	11th to 20th	Night	11% 4 21% 42% 21% 2	400
	21st to end	Night	9% 3 22% 47% 19% 1	400
July	1st to 10th	Night	12% 2 17% 40% 27% 3	433
	11th to 20th	Night	6% 1 12% 43% 34% 4	582
	21st to end	Night	8% 2 18% 41% 27% 4	657
August	1st to 10th	Night	12% 3 14% 43% 25% 3	597
	11th to 20th	Night	14% 2 14% 40% 26% 3	692
	21st to end	Night	11% 3 15% 36% 29% 5%	880
September	1st to 10th	Night	15% 2 16% 36% 26% 5%	800
	11th to 20th	Night	15% 3 16% 33% 30% 3	800
	21st to end	Night	25% 5% 21% 32% 16% 1	800
October	1st to 10th	Night	17% 5% 22% 30% 22% 4	773
	11th to 20th	Night	18% 9% 25% 31% 16% 1	760
	21st to end	Night	16% 9% 29% 30% 15% 1	836
November	1st to 10th	Night	17% 8% 30% 30% 13% 2	780
	11th to 20th	Night	19% 12% 30% 29% 9%	800
	21st to end	Night	14% 14% 33% 29% 9% 1	800
December	1st to 10th	Night	20% 15% 36% 22% 7% 1	800
	11th to 20th	Night	18% 11% 37% 28% 6%	800
	21st to end	Night	20% 14% 31% 31% 5%	880

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