Stone Tavern Farm
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stone Tavern Farm clear sky chart from 2005-11-06 to 2025-11-18.

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	16% 12% 4 10% 5% 5% 4 4 5% 6% 28%	127072
	Night	16% 13% 5% 11% 6% 4 4 3 4 6% 29%	123303
Transparency	Day	54% 7% 11% 18% 10% 1	130561
	Night	56% 6% 11% 16% 10% 1	127901
Seeing	Day	27% 20% 27% 16% 7% 3	16138
	Night	26% 20% 25% 21% 8% 1	25242

By Month

Percentage Cloud Cover NE (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	10% 14% 12% 24% 8% 3 2 2 3 3 18%	3597
	11th to 20th	Day	11% 17% 7% 22% 9% 6% 4 2 4 3 15%	3570
	21st to end	Day	15% 15% 8% 12% 7% 5% 3 3 4 4 25%	4259
February	1st to 10th	Day	13% 16% 6% 15% 9% 5% 5% 4 4 5% 20%	1800
	11th to 20th	Day	10% 13% 6% 15% 8% 6% 4 4 5% 5% 24%	1884
	21st to end	Day	15% 16% 4 11% 8% 4 4 3 5% 5% 24%	1650
March	1st to 10th	Day	18% 17% 6% 12% 5% 4 4 2 3 4 25%	4476
	11th to 20th	Day	12% 15% 7% 9% 5% 4 3 2 4 5% 34%	4842
	21st to end	Day	18% 12% 4 11% 5% 4 3 3 4 5% 30%	5872
April	1st to 10th	Day	16% 17% 4 9% 5% 4 4 3 4 5% 28%	2400
	11th to 20th	Day	15% 13% 3 8% 5% 4 5% 4 4 5% 33%	2374
	21st to end	Day	18% 15% 4 8% 4 4 4 3 4 6% 32%	2430
May	1st to 10th	Day	29% 13% 3 7% 4 4 4 3 5% 6% 23%	6106
	11th to 20th	Day	17% 12% 3 8% 6% 5% 5% 4 6% 6% 28%	6318
	21st to end	Day	21% 10% 3 7% 5% 5% 5% 5% 6% 7% 27%	6949
June	1st to 10th	Day	19% 8% 3 7% 5% 5% 5% 5% 6% 9% 29%	2800
	11th to 20th	Day	18% 8% 3 7% 5% 5% 5% 5% 7% 9% 29%	2800
	21st to end	Day	19% 8% 3 6% 5% 5% 5% 4 7% 8% 30%	2800
July	1st to 10th	Day	11% 7% 3 9% 6% 5% 6% 4 7% 8% 32%	6360
	11th to 20th	Day	11% 6% 3 8% 6% 6% 7% 5% 8% 10% 30%	6360
	21st to end	Day	15% 7% 3 6% 5% 5% 5% 4 6% 8% 37%	6926
August	1st to 10th	Day	19% 8% 3 8% 5% 5% 5% 4 6% 8% 29%	4410
	11th to 20th	Day	15% 7% 3 8% 6% 6% 6% 5% 8% 8% 27%	3891
	21st to end	Day	15% 8% 2 6% 4 5% 5% 4 7% 8% 35%	4312
September	1st to 10th	Day	16% 6% 2 7% 5% 4 4 3 5% 8% 39%	2400
	11th to 20th	Day	14% 8% 2 6% 4 4 3 4 5% 7% 44%	2345
	21st to end	Day	17% 7% 2 8% 5% 4 5% 4 5% 8% 35%	2200
October	1st to 10th	Day	18% 10% 3 8% 5% 4 4 3 4 5% 34%	2031
	11th to 20th	Day	15% 13% 3 6% 4 4 4 4 6% 6% 34%	2000
	21st to end	Day	20% 17% 3 7% 4 4 4 3 5% 6% 27%	2042
November	1st to 10th	Day	13% 14% 4 7% 4 4 4 3 5% 6% 36%	1851
	11th to 20th	Day	14% 19% 5% 10% 5% 5% 4 3 4 3 29%	1863
	21st to end	Day	15% 19% 5% 8% 5% 5% 4 3 4 6% 25%	1608
December	1st to 10th	Day	11% 20% 7% 23% 6% 5% 4 3 4 4 13%	2600
	11th to 20th	Day	15% 19% 8% 13% 5% 3 3 2 3 3 24%	2986
	21st to end	Day	14% 17% 8% 14% 6% 4 3 3 5% 5% 21%	3960
January	1st to 10th	Night	12% 13% 8% 24% 7% 5% 4 3 3 4 17%	6349
	11th to 20th	Night	8% 18% 8% 24% 9% 5% 3 3 3 4 14%	6315
	21st to end	Night	13% 13% 6% 14% 9% 6% 6% 3 4 5% 21%	6696
February	1st to 10th	Night	12% 16% 6% 13% 8% 6% 4 4 5% 5% 21%	2600
	11th to 20th	Night	10% 13% 7% 15% 9% 6% 6% 4 5% 6% 20%	2402
	21st to end	Night	17% 13% 5% 13% 7% 5% 4 4 4 6% 24%	1980
March	1st to 10th	Night	15% 11% 5% 14% 7% 5% 4 3 4 5% 26%	5364
	11th to 20th	Night	13% 15% 7% 10% 5% 4 3 3 4 6% 31%	5099
	21st to end	Night	17% 14% 6% 11% 5% 4 3 3 4 5% 29%	5059
April	1st to 10th	Night	15% 16% 5% 9% 6% 5% 4 4 4 6% 26%	2000
	11th to 20th	Night	17% 16% 3 6% 5% 4 3 3 4 5% 34%	1975
	21st to end	Night	19% 13% 4 6% 4 3 4 3 4 6% 34%	1968
May	1st to 10th	Night	32% 15% 3 6% 3 3 3 3 4 5% 25%	3877
	11th to 20th	Night	18% 15% 3 8% 4 4 4 3 4 6% 29%	3575
	21st to end	Night	23% 11% 3 7% 4 4 4 3 5% 7% 28%	3926
June	1st to 10th	Night	16% 9% 3 7% 5% 4 4 4 6% 7% 37%	1600
	11th to 20th	Night	18% 8% 2 5% 4 4 4 4 6% 9% 37%	1600
	21st to end	Night	14% 6% 2 4 4 6% 5% 4 7% 8% 40%	1600
July	1st to 10th	Night	12% 9% 3 7% 5% 4 4 4 6% 8% 38%	3600
	11th to 20th	Night	16% 8% 3 8% 5% 4 5% 3 5% 8% 35%	3600
	21st to end	Night	14% 7% 2 6% 4 4 4 3 5% 6% 44%	3926
August	1st to 10th	Night	25% 8% 3 7% 4 4 4 3 4 6% 32%	2735
	11th to 20th	Night	16% 10% 3 7% 4 3 5% 3 4 6% 38%	3122
	21st to end	Night	13% 12% 2 5% 4 4 4 3 5% 6% 43%	3586
September	1st to 10th	Night	15% 7% 3 6% 4 4 4 3 5% 6% 44%	2000
	11th to 20th	Night	14% 6% 1 6% 3 3 3 3 4 6% 50%	2055
	21st to end	Night	18% 7% 2 7% 5% 5% 3 3 4 6% 39%	2200
October	1st to 10th	Night	19% 11% 3 6% 4 4 4 4 5% 6% 35%	2365
	11th to 20th	Night	17% 11% 3 8% 4 4 4 3 5% 6% 37%	2400
	21st to end	Night	20% 16% 3 8% 5% 4 3 3 5% 7% 27%	2796
November	1st to 10th	Night	12% 16% 4 7% 4 4 4 3 5% 5% 37%	2667
	11th to 20th	Night	15% 16% 5% 9% 5% 4 4 4 4 6% 28%	2692
	21st to end	Night	12% 16% 6% 9% 5% 5% 5% 3 5% 6% 27%	2790
December	1st to 10th	Night	12% 19% 8% 18% 6% 5% 4 3 4 5% 15%	4580
	11th to 20th	Night	20% 16% 7% 11% 5% 3 3 2 3 4 25%	5208
	21st to end	Night	17% 18% 7% 15% 6% 4 3 3 4 4 21%	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	69% 7% 7% 13% 4 1	3598
	11th to 20th	Day	74% 5% 5% 10% 5% 2	3600
	21st to end	Day	62% 4 7% 18% 7% 2	4259
February	1st to 10th	Day	66% 6% 9% 13% 6% 1	1800
	11th to 20th	Day	60% 6% 8% 16% 8% 1	1893
	21st to end	Day	60% 6% 10% 15% 9%	1650
March	1st to 10th	Day	63% 4 10% 11% 9% 3	4479
	11th to 20th	Day	52% 6% 14% 19% 6% 4	4842
	21st to end	Day	55% 6% 7% 12% 17% 3	5872
April	1st to 10th	Day	58% 5% 7% 19% 9% 2	2400
	11th to 20th	Day	51% 7% 10% 17% 13% 1	2374
	21st to end	Day	55% 5% 9% 17% 12% 2	2430
May	1st to 10th	Day	62% 6% 9% 13% 9% 1	6117
	11th to 20th	Day	54% 8% 10% 18% 9% 1	6322
	21st to end	Day	53% 8% 11% 18% 8% 1	6949
June	1st to 10th	Day	50% 8% 14% 17% 11%	2800
	11th to 20th	Day	49% 8% 15% 18% 9% 1	2800
	21st to end	Day	51% 8% 13% 19% 9%	2800
July	1st to 10th	Day	47% 8% 14% 20% 10%	6290
	11th to 20th	Day	45% 10% 14% 22% 9%	6285
	21st to end	Day	43% 7% 11% 26% 12%	6728
August	1st to 10th	Day	53% 8% 13% 17% 8% 1	4396
	11th to 20th	Day	48% 10% 15% 23% 4	3928
	21st to end	Day	44% 6% 14% 28% 8% 1	4312
September	1st to 10th	Day	43% 7% 13% 24% 13% 1	2400
	11th to 20th	Day	39% 6% 10% 23% 20% 1	2345
	21st to end	Day	46% 7% 12% 20% 13% 2	2200
October	1st to 10th	Day	51% 5% 8% 20% 15% 1	3304
	11th to 20th	Day	44% 5% 9% 20% 16% 5%	3240
	21st to end	Day	42% 6% 14% 24% 12% 2	3280
November	1st to 10th	Day	48% 6% 11% 20% 13% 2	1851
	11th to 20th	Day	59% 5% 8% 14% 11% 2	1863
	21st to end	Day	59% 7% 11% 16% 5% 1	1608
December	1st to 10th	Day	74% 5% 8% 10% 3	2600
	11th to 20th	Day	67% 3 9% 13% 8%	2986
	21st to end	Day	64% 5% 7% 10% 11% 3	3960
January	1st to 10th	Night	68% 7% 9% 10% 6% 1	6349
	11th to 20th	Night	74% 5% 8% 8% 4 1	6360
	21st to end	Night	64% 6% 9% 9% 10% 2	6696
February	1st to 10th	Night	63% 8% 9% 13% 7% 1	2600
	11th to 20th	Night	63% 8% 9% 12% 7% 1	2404
	21st to end	Night	60% 6% 10% 15% 7% 2	1980
March	1st to 10th	Night	60% 4 12% 13% 10% 1	5374
	11th to 20th	Night	54% 6% 16% 15% 6% 3	5100
	21st to end	Night	58% 5% 6% 14% 16% 1	5059
April	1st to 10th	Night	59% 6% 10% 16% 8% 1	2000
	11th to 20th	Night	52% 6% 10% 18% 13%	1975
	21st to end	Night	51% 8% 8% 19% 12% 2	1968
May	1st to 10th	Night	63% 5% 9% 13% 9% 2	3883
	11th to 20th	Night	55% 9% 10% 18% 7% 1	3576
	21st to end	Night	54% 8% 11% 17% 9% 1	3927
June	1st to 10th	Night	45% 7% 11% 23% 13% 1	1600
	11th to 20th	Night	44% 7% 17% 23% 9%	1600
	21st to end	Night	40% 10% 16% 23% 11% 1	1600
July	1st to 10th	Night	44% 6% 16% 19% 14% 1	3560
	11th to 20th	Night	46% 8% 14% 22% 10% 1	3552
	21st to end	Night	40% 6% 13% 27% 12% 1	3809
August	1st to 10th	Night	53% 8% 13% 19% 7% 1	2725
	11th to 20th	Night	46% 7% 16% 24% 8%	3151
	21st to end	Night	41% 6% 12% 31% 9%	3586
September	1st to 10th	Night	40% 7% 13% 26% 14% 1	2000
	11th to 20th	Night	35% 6% 11% 27% 21% 1	2055
	21st to end	Night	47% 6% 10% 22% 14% 2	2200
October	1st to 10th	Night	53% 6% 10% 19% 10% 1	3872
	11th to 20th	Night	45% 5% 14% 16% 16% 6%	3899
	21st to end	Night	45% 6% 15% 23% 10% 1	4508
November	1st to 10th	Night	49% 7% 10% 18% 14% 2	2667
	11th to 20th	Night	56% 6% 10% 15% 10% 3	2692
	21st to end	Night	56% 8% 14% 17% 6%	2790
December	1st to 10th	Night	70% 7% 9% 13% 2	4580
	11th to 20th	Night	64% 4 9% 12% 11%	5208
	21st to end	Night	67% 5% 7% 9% 9% 3	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	34% 29% 24% 10% 3 1	200
	11th to 20th	Day	41% 28% 22% 8% 1 1	200
	21st to end	Day	33% 30% 26% 8% 2	285
February	1st to 10th	Day	43% 31% 22% 4	300
	11th to 20th	Day	42% 33% 18% 7% 1	432
	21st to end	Day	39% 26% 25% 8% 2	414
March	1st to 10th	Day	34% 26% 27% 10% 2	500
	11th to 20th	Day	37% 24% 26% 10% 3	500
	21st to end	Day	36% 28% 22% 9% 4 1	550
April	1st to 10th	Day	38% 26% 20% 12% 4	500
	11th to 20th	Day	33% 26% 24% 10% 5% 2	492
	21st to end	Day	32% 24% 28% 10% 4 2	500
May	1st to 10th	Day	37% 19% 26% 9% 5% 3	503
	11th to 20th	Day	22% 21% 31% 18% 6% 2	527
	21st to end	Day	21% 14% 34% 19% 9% 3	573
June	1st to 10th	Day	23% 20% 30% 18% 8% 2	530
	11th to 20th	Day	21% 19% 28% 23% 7% 2	530
	21st to end	Day	23% 18% 33% 18% 6% 2	530
July	1st to 10th	Day	13% 12% 35% 24% 13% 3	525
	11th to 20th	Day	11% 11% 37% 25% 13% 2	524
	21st to end	Day	15% 13% 38% 22% 9% 2	576
August	1st to 10th	Day	11% 15% 29% 23% 15% 6%	526
	11th to 20th	Day	16% 12% 30% 24% 11% 7%	519
	21st to end	Day	16% 15% 31% 21% 11% 6%	583
September	1st to 10th	Day	21% 13% 24% 23% 13% 6%	530
	11th to 20th	Day	14% 13% 24% 22% 14% 12%	530
	21st to end	Day	22% 15% 28% 21% 10% 5%	530
October	1st to 10th	Day	25% 16% 25% 16% 13% 4	530
	11th to 20th	Day	28% 21% 25% 18% 6% 2	530
	21st to end	Day	31% 22% 26% 16% 4	495
November	1st to 10th	Day	30% 21% 24% 17% 8% 1	425
	11th to 20th	Day	36% 24% 22% 13% 4 1	421
	21st to end	Day	39% 23% 27% 9% 1	208
December	1st to 10th	Day	36% 28% 24% 9% 4	200
	11th to 20th	Day	40% 26% 27% 7% 1	200
	21st to end	Day	35% 26% 28% 8% 2	220
January	1st to 10th	Night	29% 31% 28% 11% 2	800
	11th to 20th	Night	31% 26% 26% 14% 3	800
	21st to end	Night	25% 31% 27% 14% 2	880
February	1st to 10th	Night	32% 24% 31% 12% 1	800
	11th to 20th	Night	31% 29% 28% 11% 1	783
	21st to end	Night	34% 25% 27% 11% 2	660
March	1st to 10th	Night	30% 28% 27% 13% 2	800
	11th to 20th	Night	29% 28% 24% 16% 3	800
	21st to end	Night	28% 26% 25% 15% 5%	880
April	1st to 10th	Night	29% 25% 27% 17% 2	800
	11th to 20th	Night	29% 23% 25% 17% 6%	791
	21st to end	Night	30% 20% 23% 20% 7%	768
May	1st to 10th	Night	31% 15% 25% 21% 7% 1	527
	11th to 20th	Night	21% 14% 31% 28% 5% 1	394
	21st to end	Night	17% 9% 29% 30% 13% 1	433
June	1st to 10th	Night	18% 14% 24% 32% 13%	400
	11th to 20th	Night	20% 11% 20% 36% 12%	400
	21st to end	Night	17% 8% 25% 37% 13% 1	400
July	1st to 10th	Night	14% 9% 22% 38% 15% 1	390
	11th to 20th	Night	13% 5% 26% 35% 20% 1	388
	21st to end	Night	11% 7% 23% 44% 14% 1	438
August	1st to 10th	Night	14% 7% 23% 32% 23% 2	482
	11th to 20th	Night	15% 7% 18% 37% 20% 3	739
	21st to end	Night	17% 9% 20% 30% 22% 2	880
September	1st to 10th	Night	18% 8% 26% 28% 17% 3	800
	11th to 20th	Night	18% 9% 21% 25% 21% 7%	800
	21st to end	Night	21% 12% 24% 25% 15% 3	800
October	1st to 10th	Night	25% 15% 20% 22% 15% 3	800
	11th to 20th	Night	25% 17% 25% 25% 7% 1	800
	21st to end	Night	31% 21% 24% 21% 3	880
November	1st to 10th	Night	26% 20% 27% 20% 6%	820
	11th to 20th	Night	29% 25% 24% 15% 5% 2	829
	21st to end	Night	26% 27% 25% 17% 4 1	800
December	1st to 10th	Night	31% 29% 24% 13% 4	800
	11th to 20th	Night	33% 26% 24% 15% 2	800
	21st to end	Night	31% 30% 23% 14% 3	880

Page generated at 2025-11-15 00:56:01. Version ac07

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