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 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 4 5% 6% 8% 44%	74626
	Night	14% 6% 2 5% 5% 3 4 4 5% 7% 44%	75077
Transparency	Day	38% 7% 12% 22% 17% 4	74344
	Night	38% 7% 11% 21% 18% 4	74878
Seeing	Day	18% 11% 26% 25% 14% 5%	13985
	Night	17% 10% 29% 30% 13% 1	23758

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% 7% 2 5% 4 3 4 4 5% 5% 47%	1682
	11th to 20th	Day	17% 7% 3 4 5% 3 4 5% 5% 5% 43%	1629
	21st to end	Day	17% 6% 3 5% 5% 2 3 4 5% 7% 45%	1782
February	1st to 10th	Day	13% 7% 2 6% 5% 3 4 6% 6% 8% 39%	1620
	11th to 20th	Day	21% 6% 2 3 4 2 3 4 5% 5% 44%	1630
	21st to end	Day	18% 7% 3 5% 6% 3 6% 5% 4 6% 37%	1490
March	1st to 10th	Day	13% 6% 2 4 4 2 3 3 4 7% 51%	1980
	11th to 20th	Day	17% 6% 3 5% 4 3 4 5% 5% 6% 43%	1980
	21st to end	Day	17% 7% 3 7% 6% 3 4 4 4 6% 40%	2185
April	1st to 10th	Day	11% 5% 2 4 4 2 4 4 5% 7% 52%	2160
	11th to 20th	Day	12% 5% 2 5% 4 3 4 5% 4 8% 48%	2134
	21st to end	Day	15% 6% 2 7% 4 3 4 5% 5% 7% 43%	2160
May	1st to 10th	Day	14% 6% 3 5% 5% 3 4 6% 7% 8% 40%	2272
	11th to 20th	Day	18% 6% 2 5% 6% 3 4 4 6% 7% 39%	2301
	21st to end	Day	14% 5% 2 5% 6% 3 5% 5% 7% 8% 40%	2721
June	1st to 10th	Day	11% 3 3 4 5% 4 6% 6% 6% 10% 43%	2520
	11th to 20th	Day	11% 4 2 6% 6% 3 5% 7% 7% 9% 40%	2520
	21st to end	Day	9% 4 2 5% 5% 4 6% 5% 8% 10% 42%	2520
July	1st to 10th	Day	8% 5% 2 6% 6% 4 6% 5% 7% 11% 39%	2476
	11th to 20th	Day	7% 3 2 6% 6% 4 6% 6% 7% 13% 40%	2340
	21st to end	Day	7% 4 2 5% 7% 4 6% 7% 8% 11% 39%	2547
August	1st to 10th	Day	10% 6% 3 6% 6% 4 6% 7% 7% 10% 35%	2327
	11th to 20th	Day	11% 6% 3 8% 6% 4 6% 6% 7% 8% 36%	2196
	21st to end	Day	9% 6% 2 6% 6% 3 5% 6% 7% 11% 40%	2376
September	1st to 10th	Day	14% 5% 2 4 4 3 4 4 6% 9% 44%	2160
	11th to 20th	Day	11% 6% 3 6% 4 3 3 5% 5% 7% 47%	2160
	21st to end	Day	20% 6% 3 6% 5% 3 4 4 5% 6% 39%	1880
October	1st to 10th	Day	16% 5% 2 5% 5% 3 3 4 4 5% 48%	1800
	11th to 20th	Day	17% 4 2 4 4 3 3 4 4 5% 51%	1800
	21st to end	Day	13% 5% 2 4 4 2 4 3 4 6% 52%	1980
November	1st to 10th	Day	14% 4 2 4 4 2 4 4 4 5% 55%	1849
	11th to 20th	Day	14% 5% 2 4 4 2 4 4 4 6% 50%	1710
	21st to end	Day	14% 4 3 4 3 2 3 3 4 6% 52%	1537
December	1st to 10th	Day	17% 7% 2 4 4 3 4 5% 6% 8% 41%	1520
	11th to 20th	Day	15% 6% 3 3 4 2 3 3 4 4 53%	1910
	21st to end	Day	17% 7% 2 6% 5% 3 4 4 5% 7% 41%	2772
January	1st to 10th	Night	17% 6% 2 4 4 2 4 4 4 5% 47%	2478
	11th to 20th	Night	17% 6% 3 5% 6% 3 5% 4 5% 6% 40%	2354
	21st to end	Night	17% 6% 2 3 3 2 3 4 4 6% 48%	2574
February	1st to 10th	Night	17% 6% 2 5% 5% 3 4 5% 6% 6% 42%	2340
	11th to 20th	Night	19% 6% 3 6% 5% 2 4 3 4 6% 42%	2215
	21st to end	Night	18% 6% 3 5% 4 2 3 3 3 6% 46%	1763
March	1st to 10th	Night	13% 4 2 5% 4 3 4 4 5% 5% 51%	1980
	11th to 20th	Night	18% 6% 1 5% 5% 3 4 4 6% 8% 40%	1980
	21st to end	Night	16% 7% 3 5% 6% 3 4 4 4 6% 43%	2170
April	1st to 10th	Night	13% 6% 3 5% 6% 4 4 3 4 7% 45%	1800
	11th to 20th	Night	11% 6% 3 4 4 3 4 3 5% 7% 50%	1775
	21st to end	Night	16% 5% 2 6% 5% 3 4 3 5% 6% 46%	1800
May	1st to 10th	Night	14% 6% 2 5% 5% 3 4 5% 7% 9% 41%	1703
	11th to 20th	Night	16% 7% 2 5% 5% 3 5% 5% 6% 7% 39%	1592
	21st to end	Night	13% 5% 2 5% 5% 4 4 5% 5% 9% 41%	1550
June	1st to 10th	Night	11% 5% 2 5% 5% 4 6% 5% 7% 10% 40%	1440
	11th to 20th	Night	10% 5% 2 6% 5% 3 6% 7% 7% 9% 41%	1440
	21st to end	Night	9% 5% 3 4 4 3 5% 6% 7% 10% 43%	1440
July	1st to 10th	Night	10% 4 3 7% 6% 4 4 5% 6% 9% 42%	1480
	11th to 20th	Night	5% 3 3 5% 6% 3 7% 7% 6% 10% 45%	1620
	21st to end	Night	7% 5% 2 6% 6% 4 7% 7% 6% 9% 39%	1771
August	1st to 10th	Night	9% 5% 3 7% 6% 5% 4 6% 7% 12% 37%	1611
	11th to 20th	Night	12% 7% 3 6% 6% 3 6% 7% 9% 9% 34%	1686
	21st to end	Night	9% 6% 2 5% 6% 4 6% 6% 8% 10% 39%	1980
September	1st to 10th	Night	13% 5% 3 4 5% 3 4 4 6% 9% 43%	1800
	11th to 20th	Night	11% 5% 2 4 6% 4 4 5% 5% 6% 47%	1800
	21st to end	Night	21% 8% 2 5% 5% 3 3 4 5% 6% 37%	2074
October	1st to 10th	Night	15% 5% 2 6% 4 3 3 4 4 6% 48%	2160
	11th to 20th	Night	16% 5% 3 5% 4 2 3 3 4 6% 47%	2160
	21st to end	Night	15% 5% 2 4 4 2 3 3 5% 6% 51%	2376
November	1st to 10th	Night	13% 6% 3 4 4 2 4 4 4 5% 51%	2225
	11th to 20th	Night	15% 5% 2 4 4 2 4 4 4 6% 50%	2470
	21st to end	Night	13% 4 2 4 4 2 4 5% 5% 6% 51%	2641
December	1st to 10th	Night	17% 7% 2 5% 5% 3 4 4 5% 6% 43%	2660
	11th to 20th	Night	18% 6% 2 5% 3 2 3 3 4 6% 47%	3285
	21st to end	Night	15% 8% 3 5% 4 2 4 4 5% 7% 42%	4884

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% 3 10% 24% 18% 5%	1683
	11th to 20th	Day	43% 6% 9% 21% 18% 3	1629
	21st to end	Day	40% 3 10% 23% 19% 5%	1782
February	1st to 10th	Day	42% 7% 11% 24% 13% 3	1620
	11th to 20th	Day	41% 4 8% 21% 20% 4	1639
	21st to end	Day	48% 6% 10% 15% 16% 5%	1490
March	1st to 10th	Day	35% 5% 9% 24% 21% 5%	1980
	11th to 20th	Day	41% 5% 10% 20% 16% 7%	1980
	21st to end	Day	45% 6% 9% 18% 17% 4	2185
April	1st to 10th	Day	31% 6% 12% 23% 20% 8%	2160
	11th to 20th	Day	35% 6% 12% 20% 22% 7%	2134
	21st to end	Day	40% 6% 12% 21% 16% 5%	2160
May	1st to 10th	Day	39% 9% 16% 18% 15% 3	2272
	11th to 20th	Day	44% 8% 13% 22% 11% 2	2305
	21st to end	Day	39% 9% 15% 24% 12%	2721
June	1st to 10th	Day	35% 9% 17% 24% 14% 1	2520
	11th to 20th	Day	36% 11% 16% 21% 15% 1	2520
	21st to end	Day	34% 11% 16% 23% 15% 2	2520
July	1st to 10th	Day	37% 11% 14% 20% 15% 3	2408
	11th to 20th	Day	32% 11% 21% 23% 12% 1	2271
	21st to end	Day	35% 11% 16% 22% 14% 1	2405
August	1st to 10th	Day	41% 11% 16% 22% 10% 1	2314
	11th to 20th	Day	42% 11% 15% 20% 11% 1	2196
	21st to end	Day	36% 9% 18% 22% 12% 3	2376
September	1st to 10th	Day	36% 9% 16% 16% 20% 3	2160
	11th to 20th	Day	36% 7% 10% 23% 20% 4	2160
	21st to end	Day	46% 6% 9% 20% 16% 3	1880
October	1st to 10th	Day	39% 6% 9% 23% 20% 4	1800
	11th to 20th	Day	35% 5% 9% 24% 23% 4	1800
	21st to end	Day	34% 5% 6% 24% 25% 6%	1980
November	1st to 10th	Day	33% 5% 9% 24% 25% 4	1849
	11th to 20th	Day	35% 5% 10% 21% 22% 7%	1710
	21st to end	Day	34% 5% 7% 25% 24% 5%	1537
December	1st to 10th	Day	39% 6% 11% 24% 15% 4	1520
	11th to 20th	Day	36% 4 8% 29% 17% 7%	1906
	21st to end	Day	40% 7% 10% 27% 14% 1	2772
January	1st to 10th	Night	39% 4 9% 20% 20% 7%	2478
	11th to 20th	Night	43% 7% 10% 21% 15% 4	2354
	21st to end	Night	37% 5% 9% 23% 21% 5%	2574
February	1st to 10th	Night	41% 6% 11% 22% 17% 3	2340
	11th to 20th	Night	45% 4 7% 20% 18% 7%	2217
	21st to end	Night	41% 4 9% 21% 18% 7%	1763
March	1st to 10th	Night	35% 5% 8% 24% 24% 4	1980
	11th to 20th	Night	42% 6% 8% 22% 18% 4	1980
	21st to end	Night	43% 6% 9% 21% 17% 4	2170
April	1st to 10th	Night	39% 5% 9% 18% 22% 6%	1800
	11th to 20th	Night	34% 6% 10% 21% 22% 7%	1775
	21st to end	Night	39% 6% 12% 22% 16% 5%	1800
May	1st to 10th	Night	38% 8% 15% 20% 15% 3	1703
	11th to 20th	Night	42% 10% 13% 19% 14% 2	1593
	21st to end	Night	39% 9% 13% 26% 12% 1	1551
June	1st to 10th	Night	36% 10% 14% 23% 14% 1	1440
	11th to 20th	Night	37% 12% 18% 18% 15% 1	1440
	21st to end	Night	33% 11% 14% 21% 17% 4	1440
July	1st to 10th	Night	38% 10% 15% 18% 15% 4	1438
	11th to 20th	Night	31% 12% 22% 24% 10% 2	1566
	21st to end	Night	36% 12% 16% 22% 14% 1	1672
August	1st to 10th	Night	38% 11% 18% 23% 10% 1	1600
	11th to 20th	Night	40% 11% 19% 18% 12%	1686
	21st to end	Night	37% 11% 16% 23% 11% 2	1980
September	1st to 10th	Night	39% 9% 14% 18% 15% 5%	1800
	11th to 20th	Night	35% 7% 11% 23% 21% 3	1800
	21st to end	Night	46% 7% 11% 17% 16% 3	2074
October	1st to 10th	Night	38% 6% 10% 22% 19% 4	2160
	11th to 20th	Night	38% 5% 8% 23% 22% 5%	2160
	21st to end	Night	34% 5% 9% 22% 24% 6%	2376
November	1st to 10th	Night	35% 5% 9% 21% 23% 6%	2225
	11th to 20th	Night	36% 5% 9% 18% 23% 9%	2470
	21st to end	Night	33% 5% 9% 24% 23% 6%	2641
December	1st to 10th	Night	43% 6% 9% 22% 17% 4	2660
	11th to 20th	Night	38% 5% 10% 21% 21% 6%	3288
	21st to end	Night	39% 6% 12% 24% 17% 2	4884

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% 29% 16% 4	258
	11th to 20th	Day	27% 29% 32% 10% 3	243
	21st to end	Day	25% 25% 38% 11% 2	264
February	1st to 10th	Day	23% 25% 38% 11% 3	240
	11th to 20th	Day	35% 23% 31% 11% 1	297
	21st to end	Day	29% 18% 33% 17% 3	346
March	1st to 10th	Day	22% 21% 34% 19% 5%	420
	11th to 20th	Day	24% 23% 34% 14% 4 1	420
	21st to end	Day	24% 17% 37% 16% 5% 1	462
April	1st to 10th	Day	24% 18% 30% 20% 7%	420
	11th to 20th	Day	17% 14% 32% 25% 8% 4	412
	21st to end	Day	22% 17% 32% 21% 7% 1	420
May	1st to 10th	Day	17% 17% 34% 22% 8% 2	423
	11th to 20th	Day	21% 9% 28% 27% 11% 3	447
	21st to end	Day	20% 5% 22% 29% 20% 5%	485
June	1st to 10th	Day	11% 6% 27% 30% 22% 5%	450
	11th to 20th	Day	13% 6% 23% 35% 16% 8%	450
	21st to end	Day	12% 4 22% 36% 20% 5%	450
July	1st to 10th	Day	11% 2 17% 32% 29% 9%	445
	11th to 20th	Day	4 2 14% 39% 30% 10%	444
	21st to end	Day	10% 2 21% 34% 24% 9%	488
August	1st to 10th	Day	13% 2 18% 30% 28% 7%	446
	11th to 20th	Day	11% 5% 15% 31% 26% 11%	439
	21st to end	Day	8% 5% 16% 30% 25% 16%	495
September	1st to 10th	Day	16% 4 16% 27% 22% 16%	450
	11th to 20th	Day	14% 4 17% 30% 23% 12%	450
	21st to end	Day	26% 8% 22% 28% 12% 4	450
October	1st to 10th	Day	20% 7% 22% 25% 19% 7%	450
	11th to 20th	Day	17% 11% 23% 30% 17% 3	450
	21st to end	Day	15% 12% 34% 25% 10% 3	495
November	1st to 10th	Day	18% 10% 31% 24% 14% 4	451
	11th to 20th	Day	17% 15% 32% 22% 12% 1	370
	21st to end	Day	20% 16% 32% 21% 10% 2	197
December	1st to 10th	Day	23% 18% 36% 15% 8%	180
	11th to 20th	Day	23% 18% 33% 17% 9% 1	180
	21st to end	Day	22% 16% 33% 20% 9% 1	198
January	1st to 10th	Night	21% 18% 38% 20% 3	760
	11th to 20th	Night	21% 18% 31% 26% 4	725
	21st to end	Night	20% 16% 39% 23% 2	792
February	1st to 10th	Night	21% 15% 39% 23% 3	720
	11th to 20th	Night	23% 19% 38% 18% 1	703
	21st to end	Night	22% 17% 38% 20% 3	592
March	1st to 10th	Night	18% 16% 37% 25% 3	720
	11th to 20th	Night	22% 17% 35% 21% 5% 1	720
	21st to end	Night	18% 17% 39% 22% 4	792
April	1st to 10th	Night	16% 19% 40% 21% 3	720
	11th to 20th	Night	17% 12% 36% 27% 8%	711
	21st to end	Night	18% 10% 37% 29% 6%	720
May	1st to 10th	Night	16% 11% 34% 30% 7%	623
	11th to 20th	Night	17% 6% 30% 36% 11% 1	531
	21st to end	Night	15% 4 19% 41% 20% 2	389
June	1st to 10th	Night	13% 3 19% 43% 21% 1	360
	11th to 20th	Night	10% 4 21% 41% 23% 2	360
	21st to end	Night	9% 3 22% 46% 19% 1	360
July	1st to 10th	Night	11% 2 18% 40% 27% 3	388
	11th to 20th	Night	5% 1 12% 43% 35% 5%	522
	21st to end	Night	8% 2 18% 42% 26% 4	591
August	1st to 10th	Night	10% 2 15% 43% 27% 3	537
	11th to 20th	Night	15% 2 13% 40% 27% 3	622
	21st to end	Night	11% 3 14% 35% 31% 6%	792
September	1st to 10th	Night	15% 1 16% 34% 28% 6%	720
	11th to 20th	Night	13% 3 16% 34% 31% 3	720
	21st to end	Night	24% 5% 22% 31% 17% 1	720
October	1st to 10th	Night	17% 6% 22% 29% 23% 4	720
	11th to 20th	Night	18% 9% 25% 30% 16% 1	720
	21st to end	Night	17% 10% 30% 29% 14% 1	792
November	1st to 10th	Night	17% 8% 29% 30% 13% 2	740
	11th to 20th	Night	18% 13% 30% 29% 10%	760
	21st to end	Night	14% 13% 32% 30% 9% 1	760
December	1st to 10th	Night	20% 15% 35% 22% 8% 1	760
	11th to 20th	Night	18% 11% 37% 28% 6%	760
	21st to end	Night	20% 14% 30% 31% 5%	836

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