Stokesville Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stokesville Observatory clear sky chart from 2005-11-06 to 2026-08-30.

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% 5% 5% 5% 4 6% 8% 41%	143183
	Night	12% 6% 2 6% 4 4 4 4 6% 8% 45%	138989
Transparency	Day	39% 7% 11% 22% 16% 5%	146789
	Night	37% 6% 12% 23% 18% 5%	143454
Seeing	Day	17% 12% 25% 24% 15% 6%	17349
	Night	16% 8% 26% 33% 15% 2	27137

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	11% 6% 2 6% 5% 4 4 3 4 6% 48%	5258
	11th to 20th	Day	10% 8% 2 7% 4 4 4 3 4 4 50%	5280
	21st to end	Day	12% 6% 3 7% 4 4 4 3 5% 5% 47%	5780
February	1st to 10th	Day	10% 8% 3 7% 5% 4 4 4 6% 6% 42%	1890
	11th to 20th	Day	14% 8% 3 7% 4 4 4 5% 4 7% 41%	1843
	21st to end	Day	13% 8% 2 6% 4 4 4 5% 6% 7% 41%	1801
March	1st to 10th	Day	14% 7% 2 5% 4 4 5% 5% 6% 6% 42%	5045
	11th to 20th	Day	8% 6% 2 5% 4 3 4 3 6% 7% 52%	5090
	21st to end	Day	11% 7% 3 7% 5% 5% 5% 4 5% 6% 41%	5586
April	1st to 10th	Day	10% 6% 2 6% 5% 4 5% 4 6% 6% 46%	2447
	11th to 20th	Day	12% 5% 2 5% 4 4 4 4 6% 7% 47%	2494
	21st to end	Day	15% 6% 2 6% 5% 4 4 3 5% 7% 42%	2619
May	1st to 10th	Day	12% 6% 2 7% 5% 5% 7% 5% 7% 9% 34%	7616
	11th to 20th	Day	18% 6% 2 6% 4 5% 5% 4 5% 8% 37%	7626
	21st to end	Day	20% 5% 2 6% 4 4 5% 4 6% 8% 36%	8628
June	1st to 10th	Day	10% 4 2 6% 5% 5% 6% 4 6% 9% 42%	2940
	11th to 20th	Day	9% 5% 2 6% 5% 5% 6% 6% 7% 11% 36%	2940
	21st to end	Day	8% 5% 1 6% 5% 5% 6% 5% 7% 11% 41%	2940
July	1st to 10th	Day	8% 5% 2 7% 6% 5% 6% 5% 7% 10% 40%	7684
	11th to 20th	Day	9% 5% 2 7% 6% 6% 7% 6% 9% 13% 31%	7680
	21st to end	Day	9% 6% 2 8% 5% 6% 6% 5% 8% 10% 34%	8340
August	1st to 10th	Day	13% 5% 2 8% 6% 6% 6% 6% 8% 10% 32%	4364
	11th to 20th	Day	8% 4 2 7% 5% 6% 7% 6% 9% 9% 37%	4286
	21st to end	Day	8% 4 2 5% 5% 5% 5% 5% 6% 10% 46%	4420
September	1st to 10th	Day	11% 6% 2 6% 4 4 4 4 5% 6% 46%	2400
	11th to 20th	Day	14% 6% 2 5% 4 5% 4 4 5% 7% 44%	2261
	21st to end	Day	23% 5% 2 6% 4 4 4 4 6% 6% 36%	2162
October	1st to 10th	Day	15% 5% 2 5% 3 4 4 4 4 7% 47%	2000
	11th to 20th	Day	15% 4 1 5% 3 4 4 3 5% 6% 50%	2000
	21st to end	Day	13% 5% 2 4 5% 3 4 4 3 6% 52%	2200
November	1st to 10th	Day	9% 6% 2 4 3 4 3 3 6% 6% 55%	2057
	11th to 20th	Day	12% 5% 2 5% 3 4 4 3 6% 6% 50%	1858
	21st to end	Day	12% 5% 2 5% 4 4 3 4 5% 6% 49%	1680
December	1st to 10th	Day	9% 5% 2 5% 4 4 5% 4 5% 7% 51%	2680
	11th to 20th	Day	18% 5% 1 5% 3 3 3 3 5% 7% 46%	3070
	21st to end	Day	17% 6% 2 7% 4 5% 5% 4 6% 7% 37%	4218
January	1st to 10th	Night	10% 6% 2 5% 4 4 5% 4 5% 6% 49%	7635
	11th to 20th	Night	10% 7% 2 5% 3 3 3 2 5% 6% 54%	7680
	21st to end	Night	13% 6% 2 5% 4 3 3 3 4 5% 53%	8401
February	1st to 10th	Night	10% 7% 2 6% 4 4 4 5% 6% 7% 45%	2730
	11th to 20th	Night	16% 7% 2 6% 4 4 4 3 5% 7% 41%	2663
	21st to end	Night	13% 7% 2 6% 4 4 4 4 6% 8% 43%	2001
March	1st to 10th	Night	15% 5% 2 5% 3 3 3 3 5% 6% 47%	5028
	11th to 20th	Night	9% 3 1 4 4 4 4 3 6% 8% 53%	5090
	21st to end	Night	10% 6% 2 6% 4 5% 4 3 5% 7% 46%	5588
April	1st to 10th	Night	13% 7% 2 4 4 5% 5% 4 6% 6% 44%	2171
	11th to 20th	Night	11% 4 2 5% 4 4 4 3 7% 9% 46%	2075
	21st to end	Night	16% 4 2 5% 4 4 4 4 6% 8% 45%	2018
May	1st to 10th	Night	14% 6% 2 6% 4 4 5% 4 6% 9% 39%	5237
	11th to 20th	Night	18% 5% 2 5% 4 3 5% 4 7% 9% 38%	5234
	21st to end	Night	20% 6% 2 6% 4 4 5% 4 5% 9% 35%	5506
June	1st to 10th	Night	9% 5% 2 6% 5% 3 4 4 7% 12% 44%	1680
	11th to 20th	Night	10% 5% 2 5% 4 4 5% 4 7% 10% 44%	1680
	21st to end	Night	8% 4 2 5% 4 3 6% 5% 7% 10% 46%	1680
July	1st to 10th	Night	7% 5% 2 7% 5% 4 5% 4 7% 10% 43%	5253
	11th to 20th	Night	12% 7% 2 8% 6% 5% 6% 5% 7% 10% 30%	5277
	21st to end	Night	9% 7% 3 8% 6% 6% 5% 5% 7% 10% 34%	5736
August	1st to 10th	Night	15% 5% 2 6% 5% 5% 4 5% 7% 10% 36%	3005
	11th to 20th	Night	9% 6% 3 7% 5% 5% 6% 5% 7% 8% 39%	2965
	21st to end	Night	9% 5% 2 6% 5% 4 4 4 6% 9% 47%	3659
September	1st to 10th	Night	12% 4 2 6% 4 4 4 4 4 7% 50%	2000
	11th to 20th	Night	14% 6% 2 6% 4 4 3 3 5% 7% 46%	2135
	21st to end	Night	23% 7% 2 5% 4 3 4 3 5% 6% 39%	2237
October	1st to 10th	Night	15% 6% 2 5% 4 4 4 2 4 6% 47%	2400
	11th to 20th	Night	13% 5% 1 5% 3 3 4 3 5% 6% 51%	2400
	21st to end	Night	14% 4 1 4 4 3 4 3 5% 6% 52%	2640
November	1st to 10th	Night	10% 6% 3 5% 3 3 4 3 4 5% 53%	2461
	11th to 20th	Night	11% 6% 1 5% 4 3 4 3 5% 7% 51%	2757
	21st to end	Night	13% 4 2 5% 4 4 4 4 6% 6% 49%	2940
December	1st to 10th	Night	8% 5% 2 5% 3 4 4 4 5% 7% 53%	4720
	11th to 20th	Night	14% 8% 2 6% 4 4 4 3 5% 6% 43%	5345
	21st to end	Night	15% 5% 2 5% 4 4 5% 5% 7% 9% 39%	6962

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	38% 3 8% 21% 22% 8%	5259
	11th to 20th	Day	37% 3 5% 16% 23% 16%	5280
	21st to end	Day	40% 3 6% 25% 21% 5%	5780
February	1st to 10th	Day	42% 5% 10% 21% 18% 4	1890
	11th to 20th	Day	43% 4 10% 20% 18% 5%	1852
	21st to end	Day	42% 5% 11% 19% 17% 6%	1801
March	1st to 10th	Day	41% 4 9% 19% 17% 10%	5045
	11th to 20th	Day	31% 5% 8% 26% 21% 9%	5090
	21st to end	Day	43% 6% 9% 17% 18% 7%	5586
April	1st to 10th	Day	37% 6% 12% 20% 18% 7%	2447
	11th to 20th	Day	36% 5% 12% 21% 20% 5%	2494
	21st to end	Day	42% 6% 10% 23% 14% 4	2619
May	1st to 10th	Day	43% 8% 10% 22% 14% 2	7651
	11th to 20th	Day	45% 7% 11% 23% 13% 1	7630
	21st to end	Day	45% 7% 11% 19% 15% 4	8643
June	1st to 10th	Day	37% 8% 14% 23% 17% 1	2940
	11th to 20th	Day	39% 10% 15% 20% 14% 2	2940
	21st to end	Day	36% 8% 15% 25% 13% 1	2940
July	1st to 10th	Day	38% 10% 15% 23% 11% 3	7619
	11th to 20th	Day	41% 12% 16% 24% 7% 1	7611
	21st to end	Day	41% 9% 13% 23% 14% 1	8156
August	1st to 10th	Day	44% 9% 17% 23% 7%	4351
	11th to 20th	Day	38% 9% 13% 28% 11% 1	4325
	21st to end	Day	33% 9% 16% 27% 13% 2	4420
September	1st to 10th	Day	38% 7% 13% 18% 20% 4	2400
	11th to 20th	Day	40% 5% 7% 25% 19% 3	2261
	21st to end	Day	48% 7% 9% 18% 16% 2	2162
October	1st to 10th	Day	32% 4 7% 21% 28% 8%	3260
	11th to 20th	Day	26% 3 7% 28% 23% 13%	3240
	21st to end	Day	23% 3 10% 29% 21% 14%	3538
November	1st to 10th	Day	31% 4 10% 24% 26% 5%	2057
	11th to 20th	Day	35% 5% 9% 21% 23% 9%	1858
	21st to end	Day	36% 4 10% 25% 22% 3	1680
December	1st to 10th	Day	33% 5% 9% 26% 20% 7%	2680
	11th to 20th	Day	39% 5% 12% 21% 18% 5%	3066
	21st to end	Day	44% 6% 13% 19% 16% 2	4218
January	1st to 10th	Night	35% 4 9% 22% 22% 7%	7636
	11th to 20th	Night	32% 3 7% 22% 25% 12%	7680
	21st to end	Night	35% 3 7% 26% 23% 6%	8401
February	1st to 10th	Night	38% 6% 12% 24% 17% 3	2730
	11th to 20th	Night	44% 5% 8% 20% 17% 6%	2665
	21st to end	Night	39% 6% 12% 21% 15% 7%	2001
March	1st to 10th	Night	38% 5% 7% 21% 19% 9%	5028
	11th to 20th	Night	28% 4 10% 25% 26% 7%	5090
	21st to end	Night	38% 5% 13% 20% 19% 5%	5588
April	1st to 10th	Night	39% 7% 11% 20% 19% 4	2171
	11th to 20th	Night	33% 6% 15% 22% 19% 4	2075
	21st to end	Night	37% 6% 12% 27% 15% 3	2018
May	1st to 10th	Night	42% 8% 13% 22% 12% 3	5264
	11th to 20th	Night	41% 8% 14% 25% 11% 1	5235
	21st to end	Night	46% 8% 14% 20% 9% 3	5514
June	1st to 10th	Night	33% 9% 15% 26% 16% 1	1680
	11th to 20th	Night	34% 10% 18% 23% 13% 2	1680
	21st to end	Night	31% 10% 17% 22% 17% 2	1680
July	1st to 10th	Night	36% 10% 17% 22% 13% 1	5210
	11th to 20th	Night	46% 11% 16% 19% 8%	5226
	21st to end	Night	43% 9% 17% 19% 13%	5606
August	1st to 10th	Night	42% 9% 18% 24% 6% 1	2994
	11th to 20th	Night	40% 8% 14% 25% 13%	2992
	21st to end	Night	34% 7% 17% 31% 10% 2	3659
September	1st to 10th	Night	34% 7% 15% 21% 19% 4	2000
	11th to 20th	Night	38% 5% 9% 27% 18% 3	2135
	21st to end	Night	47% 6% 9% 19% 16% 2	2237
October	1st to 10th	Night	40% 4 8% 20% 23% 5%	3920
	11th to 20th	Night	25% 4 10% 21% 28% 11%	3899
	21st to end	Night	22% 3 11% 29% 27% 9%	4252
November	1st to 10th	Night	34% 4 8% 23% 24% 7%	2461
	11th to 20th	Night	34% 4 9% 23% 25% 6%	2757
	21st to end	Night	35% 5% 10% 24% 21% 5%	2940
December	1st to 10th	Night	31% 4 11% 29% 23% 3	4720
	11th to 20th	Night	42% 4 12% 18% 17% 7%	5348
	21st to end	Night	39% 7% 13% 21% 18% 1	6962

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	22% 31% 27% 16% 4 1	330
	11th to 20th	Day	26% 31% 28% 14% 2	330
	21st to end	Day	24% 27% 32% 15% 2	363
February	1st to 10th	Day	22% 24% 35% 15% 3	330
	11th to 20th	Day	34% 26% 31% 8% 2	330
	21st to end	Day	26% 19% 35% 18% 3	393
March	1st to 10th	Day	18% 23% 31% 23% 6%	540
	11th to 20th	Day	21% 22% 32% 18% 6% 2	540
	21st to end	Day	20% 19% 33% 22% 6% 1	594
April	1st to 10th	Day	21% 21% 27% 20% 10% 1	540
	11th to 20th	Day	18% 14% 29% 23% 13% 3	532
	21st to end	Day	22% 15% 28% 23% 10% 3	540
May	1st to 10th	Day	19% 18% 29% 20% 10% 4	543
	11th to 20th	Day	22% 10% 27% 21% 15% 5%	567
	21st to end	Day	19% 8% 21% 24% 19% 8%	617
June	1st to 10th	Day	12% 5% 27% 28% 21% 8%	570
	11th to 20th	Day	12% 8% 21% 30% 17% 11%	570
	21st to end	Day	9% 5% 25% 33% 21% 7%	570
July	1st to 10th	Day	11% 3 16% 26% 30% 14%	565
	11th to 20th	Day	5% 3 16% 31% 31% 14%	564
	21st to end	Day	12% 4 15% 33% 24% 13%	620
August	1st to 10th	Day	13% 5% 16% 28% 22% 15%	566
	11th to 20th	Day	12% 3 18% 29% 25% 14%	559
	21st to end	Day	9% 3 15% 31% 28% 15%	619
September	1st to 10th	Day	14% 5% 16% 28% 21% 16%	530
	11th to 20th	Day	15% 4 15% 27% 28% 12%	530
	21st to end	Day	27% 8% 18% 24% 18% 5%	530
October	1st to 10th	Day	18% 7% 19% 28% 22% 6%	530
	11th to 20th	Day	14% 13% 26% 27% 17% 3	530
	21st to end	Day	17% 13% 29% 29% 10% 2	583
November	1st to 10th	Day	16% 11% 30% 29% 12% 2	535
	11th to 20th	Day	19% 16% 33% 21% 9% 1	346
	21st to end	Day	22% 20% 29% 21% 8%	220
December	1st to 10th	Day	20% 20% 34% 21% 4	220
	11th to 20th	Day	23% 18% 29% 22% 8% 1	220
	21st to end	Day	21% 21% 34% 15% 8% 1	283
January	1st to 10th	Night	16% 17% 38% 25% 3	840
	11th to 20th	Night	18% 15% 35% 28% 4	840
	21st to end	Night	16% 13% 43% 26% 3	924
February	1st to 10th	Night	15% 14% 39% 29% 3	840
	11th to 20th	Night	24% 14% 39% 22% 1	823
	21st to end	Night	20% 15% 37% 25% 3	692
March	1st to 10th	Night	16% 13% 38% 30% 4	840
	11th to 20th	Night	20% 15% 32% 25% 7% 1	840
	21st to end	Night	19% 11% 35% 29% 6% 1	924
April	1st to 10th	Night	18% 15% 33% 27% 6%	840
	11th to 20th	Night	14% 11% 34% 30% 11% 1	831
	21st to end	Night	18% 6% 28% 37% 9% 1	758
May	1st to 10th	Night	16% 7% 27% 35% 14% 1	630
	11th to 20th	Night	20% 4 24% 34% 16% 2	621
	21st to end	Night	17% 2 16% 37% 26% 2	595
June	1st to 10th	Night	9% 1 17% 48% 23% 2	420
	11th to 20th	Night	11% 3 15% 46% 24% 2	420
	21st to end	Night	9% 1 17% 44% 27% 2	420
July	1st to 10th	Night	12% 2 8% 37% 37% 5%	603
	11th to 20th	Night	7% 1 8% 39% 38% 7%	612
	21st to end	Night	8% 2 10% 42% 34% 5%	690
August	1st to 10th	Night	14% 1 8% 42% 31% 4	627
	11th to 20th	Night	12% 3 10% 38% 33% 4	624
	21st to end	Night	12% 2 14% 35% 32% 5%	899
September	1st to 10th	Night	13% 1 12% 38% 29% 7%	800
	11th to 20th	Night	16% 3 10% 35% 31% 6%	800
	21st to end	Night	26% 3 17% 33% 20% 2	800
October	1st to 10th	Night	17% 5% 18% 32% 24% 4	800
	11th to 20th	Night	15% 8% 27% 33% 16% 1	800
	21st to end	Night	16% 9% 25% 36% 12% 2	880
November	1st to 10th	Night	15% 5% 27% 38% 12% 2	820
	11th to 20th	Night	16% 11% 29% 34% 9% 1	840
	21st to end	Night	16% 10% 32% 32% 8% 1	840
December	1st to 10th	Night	17% 11% 35% 31% 6%	840
	11th to 20th	Night	15% 10% 36% 34% 5%	840
	21st to end	Night	17% 11% 33% 34% 4	924

Page generated at 2026-08-27 04:07:13. Version ac07

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