BuckSnort Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the BuckSnort Observatory clear sky chart from 2005-11-06 to 2026-01-17.

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	10% 5% 2 5% 4 4 4 3 5% 7% 52%	127381
	Night	11% 5% 2 4 3 3 3 3 5% 6% 56%	124606
Transparency	Day	31% 5% 10% 21% 22% 11%	131149
	Night	29% 4 10% 21% 22% 14%	128901
Seeing	Day	12% 7% 22% 30% 23% 7%	16527
	Night	12% 7% 27% 37% 16% 1	26521

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	12% 7% 3 5% 2 3 3 2 4 5% 53%	4167
	11th to 20th	Day	11% 5% 2 3 2 2 2 3 4 5% 60%	4134
	21st to end	Day	21% 6% 2 5% 3 2 2 2 3 4 48%	4699
February	1st to 10th	Day	16% 6% 2 5% 3 3 3 2 3 6% 52%	2000
	11th to 20th	Day	15% 8% 3 4 3 3 4 3 4 5% 49%	1949
	21st to end	Day	17% 6% 2 4 3 2 3 2 3 5% 54%	1650
March	1st to 10th	Day	12% 7% 2 5% 4 4 3 3 4 5% 51%	4846
	11th to 20th	Day	13% 5% 2 5% 3 3 3 3 5% 6% 53%	4980
	21st to end	Day	10% 6% 2 5% 3 4 4 3 6% 7% 50%	5462
April	1st to 10th	Day	12% 8% 2 5% 4 3 4 3 5% 7% 48%	2200
	11th to 20th	Day	15% 6% 2 6% 4 3 3 3 5% 6% 47%	2215
	21st to end	Day	12% 6% 2 6% 4 4 4 3 4 6% 50%	2580
May	1st to 10th	Day	16% 6% 3 6% 4 4 4 4 6% 8% 41%	5862
	11th to 20th	Day	12% 6% 3 6% 4 4 4 3 5% 6% 46%	5862
	21st to end	Day	12% 6% 3 7% 5% 5% 5% 4 7% 9% 38%	6434
June	1st to 10th	Day	5% 4 1 4 4 5% 4 4 6% 8% 54%	2600
	11th to 20th	Day	5% 3 2 4 5% 3 4 5% 6% 10% 53%	2600
	21st to end	Day	6% 3 2 4 5% 4 5% 4 7% 8% 52%	2600
July	1st to 10th	Day	10% 5% 2 6% 5% 6% 5% 4 6% 8% 41%	5900
	11th to 20th	Day	3 2 1 4 3 4 5% 4 6% 9% 58%	5900
	21st to end	Day	5% 4 2 5% 4 4 5% 4 7% 11% 50%	6422
August	1st to 10th	Day	2 1 2 3 3 3 3 5% 7% 72%	4234
	11th to 20th	Day	4 2 1 3 3 3 3 2 5% 8% 64%	3920
	21st to end	Day	4 3 1 4 4 4 4 4 6% 10% 55%	4162
September	1st to 10th	Day	11% 5% 1 5% 4 4 4 4 5% 6% 51%	2200
	11th to 20th	Day	10% 5% 2 6% 4 4 3 3 5% 7% 52%	2200
	21st to end	Day	7% 3 2 5% 2 3 4 4 6% 7% 57%	2200
October	1st to 10th	Day	5% 3 1 4 3 3 3 4 5% 5% 63%	2200
	11th to 20th	Day	10% 4 1 4 2 2 3 2 4 5% 62%	2051
	21st to end	Day	11% 5% 1 3 3 3 2 2 3 5% 63%	2200
November	1st to 10th	Day	13% 5% 2 4 3 2 3 3 4 5% 55%	2058
	11th to 20th	Day	7% 5% 2 5% 3 3 3 3 4 6% 60%	1906
	21st to end	Day	15% 6% 2 5% 3 3 3 2 4 5% 52%	1890
December	1st to 10th	Day	16% 6% 2 6% 4 4 4 3 4 5% 47%	3030
	11th to 20th	Day	12% 7% 3 6% 5% 4 4 3 4 5% 46%	3481
	21st to end	Day	13% 5% 1 4 2 2 2 2 3 4 60%	4587
January	1st to 10th	Night	15% 5% 2 4 2 2 2 2 3 4 58%	6018
	11th to 20th	Night	9% 3 1 3 2 2 2 1 2 6% 69%	5979
	21st to end	Night	23% 7% 2 6% 3 3 2 2 3 4 44%	6309
February	1st to 10th	Night	13% 6% 2 5% 3 4 2 2 3 5% 54%	2400
	11th to 20th	Night	16% 6% 2 5% 3 2 3 2 4 5% 52%	2338
	21st to end	Night	16% 5% 1 4 3 3 2 2 5% 5% 53%	1980
March	1st to 10th	Night	10% 5% 2 5% 3 4 3 3 6% 7% 51%	5011
	11th to 20th	Night	12% 5% 2 4 3 3 3 3 5% 6% 53%	4980
	21st to end	Night	11% 7% 2 5% 4 3 4 3 4 7% 52%	5467
April	1st to 10th	Night	9% 5% 2 4 4 4 4 4 5% 6% 53%	2200
	11th to 20th	Night	12% 5% 2 6% 3 4 4 3 4 5% 50%	2128
	21st to end	Night	11% 6% 1 4 3 3 3 3 5% 6% 53%	1820
May	1st to 10th	Night	19% 8% 2 4 3 3 3 3 4 6% 44%	4053
	11th to 20th	Night	7% 7% 2 7% 4 5% 4 4 5% 6% 49%	4053
	21st to end	Night	12% 6% 2 6% 3 4 4 4 6% 9% 44%	4443
June	1st to 10th	Night	3 2 1 4 3 3 3 4 6% 10% 61%	1800
	11th to 20th	Night	5% 2 1 3 3 3 3 4 5% 9% 62%	1800
	21st to end	Night	4 5% 1 3 3 3 3 3 7% 8% 60%	1800
July	1st to 10th	Night	9% 4 2 5% 4 3 4 4 6% 10% 50%	4078
	11th to 20th	Night	2 2 1 3 3 3 3 4 6% 10% 64%	4077
	21st to end	Night	4 4 1 5% 3 4 4 3 6% 10% 57%	4449
August	1st to 10th	Night	1 1 1 1 1 2 2 4 7% 79%	2926
	11th to 20th	Night	3 2 1 3 2 2 3 3 6% 10% 64%	3133
	21st to end	Night	4 2 1 3 3 3 3 3 7% 10% 60%	3740
September	1st to 10th	Night	9% 3 2 4 3 3 5% 3 6% 7% 54%	2200
	11th to 20th	Night	9% 6% 2 4 3 4 3 4 5% 8% 51%	2200
	21st to end	Night	7% 4 1 4 2 3 4 3 5% 7% 61%	2200
October	1st to 10th	Night	5% 3 1 3 2 3 3 3 4 6% 69%	2200
	11th to 20th	Night	9% 3 1 4 2 2 3 3 4 5% 64%	2326
	21st to end	Night	12% 4 2 4 2 3 2 2 3 4 63%	2640
November	1st to 10th	Night	11% 4 2 5% 3 2 3 2 4 4 60%	2460
	11th to 20th	Night	6% 5% 2 4 3 3 3 3 5% 5% 61%	2709
	21st to end	Night	15% 5% 2 4 3 3 3 3 4 5% 53%	2730
December	1st to 10th	Night	17% 5% 2 5% 3 2 3 2 5% 6% 49%	4380
	11th to 20th	Night	17% 7% 3 6% 3 3 3 3 4 4 50%	4946
	21st to end	Night	15% 5% 2 4 2 2 2 2 3 4 59%	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	34% 4 5% 23% 24% 10%	4168
	11th to 20th	Day	27% 3 5% 19% 28% 18%	4134
	21st to end	Day	42% 3 4 11% 24% 16%	4699
February	1st to 10th	Day	37% 4 6% 14% 22% 17%	2000
	11th to 20th	Day	38% 4 6% 19% 19% 13%	1959
	21st to end	Day	35% 3 4 15% 24% 18%	1650
March	1st to 10th	Day	35% 4 5% 14% 21% 21%	4846
	11th to 20th	Day	32% 6% 8% 9% 15% 30%	4980
	21st to end	Day	32% 6% 9% 20% 22% 10%	5464
April	1st to 10th	Day	38% 4 7% 18% 17% 15%	2200
	11th to 20th	Day	38% 5% 8% 17% 20% 12%	2215
	21st to end	Day	34% 6% 8% 19% 24% 9%	2580
May	1st to 10th	Day	40% 7% 10% 19% 20% 4	5900
	11th to 20th	Day	38% 5% 8% 15% 26% 8%	5866
	21st to end	Day	40% 8% 11% 22% 13% 6%	6447
June	1st to 10th	Day	26% 7% 13% 28% 22% 4	2600
	11th to 20th	Day	26% 6% 13% 29% 19% 7%	2600
	21st to end	Day	28% 7% 14% 24% 23% 5%	2600
July	1st to 10th	Day	39% 6% 18% 28% 8% 1	5836
	11th to 20th	Day	22% 5% 17% 33% 19% 4	5831
	21st to end	Day	27% 6% 16% 29% 20% 2	6240
August	1st to 10th	Day	13% 4 11% 33% 37% 2	4220
	11th to 20th	Day	18% 5% 16% 40% 18% 2	3958
	21st to end	Day	24% 7% 19% 27% 20% 3	4161
September	1st to 10th	Day	33% 6% 10% 19% 20% 11%	2200
	11th to 20th	Day	34% 5% 11% 22% 22% 6%	2200
	21st to end	Day	26% 6% 9% 21% 22% 15%	2200
October	1st to 10th	Day	13% 4 6% 13% 27% 37%	3590
	11th to 20th	Day	17% 3 7% 18% 32% 22%	3317
	21st to end	Day	21% 4 3 21% 38% 13%	3538
November	1st to 10th	Day	33% 4 8% 17% 27% 11%	2058
	11th to 20th	Day	26% 4 9% 19% 24% 18%	1906
	21st to end	Day	36% 3 5% 19% 22% 14%	1890
December	1st to 10th	Day	41% 2 6% 18% 22% 10%	3030
	11th to 20th	Day	40% 4 7% 11% 25% 14%	3479
	21st to end	Day	29% 3 4 18% 29% 17%	4587
January	1st to 10th	Night	32% 2 5% 20% 28% 12%	6018
	11th to 20th	Night	21% 2 3 18% 33% 22%	5979
	21st to end	Night	46% 3 3 10% 20% 17%	6309
February	1st to 10th	Night	35% 4 6% 13% 23% 19%	2400
	11th to 20th	Night	36% 3 6% 17% 22% 15%	2338
	21st to end	Night	35% 4 6% 14% 21% 20%	1980
March	1st to 10th	Night	32% 4 7% 16% 24% 17%	5011
	11th to 20th	Night	31% 6% 8% 13% 16% 26%	4980
	21st to end	Night	34% 5% 8% 18% 24% 11%	5467
April	1st to 10th	Night	31% 5% 9% 19% 18% 17%	2200
	11th to 20th	Night	35% 5% 10% 15% 20% 15%	2128
	21st to end	Night	32% 6% 11% 20% 22% 9%	1820
May	1st to 10th	Night	41% 5% 8% 22% 16% 8%	4080
	11th to 20th	Night	34% 6% 12% 17% 19% 12%	4054
	21st to end	Night	36% 6% 13% 29% 11% 6%	4452
June	1st to 10th	Night	18% 7% 17% 32% 22% 4	1800
	11th to 20th	Night	18% 6% 16% 31% 21% 8%	1800
	21st to end	Night	21% 8% 13% 30% 23% 5%	1800
July	1st to 10th	Night	31% 5% 21% 34% 8% 1	4035
	11th to 20th	Night	15% 5% 21% 39% 18% 2	4026
	21st to end	Night	24% 6% 19% 30% 17% 4	4320
August	1st to 10th	Night	8% 3 13% 37% 37% 3	2916
	11th to 20th	Night	16% 4 24% 36% 17% 2	3161
	21st to end	Night	19% 8% 21% 30% 18% 3	3740
September	1st to 10th	Night	28% 7% 12% 22% 19% 11%	2200
	11th to 20th	Night	31% 6% 13% 24% 19% 7%	2200
	21st to end	Night	23% 4 11% 26% 21% 15%	2200
October	1st to 10th	Night	11% 3 6% 16% 22% 42%	3590
	11th to 20th	Night	17% 3 8% 18% 31% 24%	3786
	21st to end	Night	21% 3 4 20% 36% 16%	4252
November	1st to 10th	Night	28% 4 7% 20% 27% 15%	2460
	11th to 20th	Night	25% 4 8% 21% 24% 18%	2709
	21st to end	Night	35% 4 7% 17% 23% 15%	2730
December	1st to 10th	Night	37% 3 7% 19% 23% 12%	4380
	11th to 20th	Night	40% 3 5% 11% 25% 16%	4947
	21st to end	Night	31% 2 4 18% 26% 19%	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	17% 14% 37% 26% 5% 1	330
	11th to 20th	Day	20% 11% 34% 24% 8% 3	318
	21st to end	Day	20% 11% 38% 24% 8%	330
February	1st to 10th	Day	21% 16% 36% 20% 7%	300
	11th to 20th	Day	21% 17% 40% 19% 4	300
	21st to end	Day	20% 19% 35% 24% 2	249
March	1st to 10th	Day	21% 18% 31% 25% 4	300
	11th to 20th	Day	19% 16% 38% 21% 6%	300
	21st to end	Day	14% 15% 42% 23% 7%	330
April	1st to 10th	Day	19% 15% 42% 18% 6%	300
	11th to 20th	Day	14% 14% 44% 20% 7% 1	333
	21st to end	Day	14% 15% 39% 23% 8% 1	680
May	1st to 10th	Day	14% 8% 38% 31% 9%	703
	11th to 20th	Day	17% 7% 29% 32% 11% 3	725
	21st to end	Day	15% 6% 25% 35% 15% 4	789
June	1st to 10th	Day	6% 2 15% 44% 27% 6%	730
	11th to 20th	Day	5% 2 15% 49% 24% 5%	730
	21st to end	Day	5% 2 10% 36% 37% 11%	730
July	1st to 10th	Day	9% 2 7% 32% 37% 14%	721
	11th to 20th	Day	3 1 5% 33% 46% 12%	718
	21st to end	Day	4 1 4 31% 45% 15%	794
August	1st to 10th	Day	2 4 30% 46% 17%	726
	11th to 20th	Day	7% 1 3 33% 41% 16%	567
	21st to end	Day	5% 1 5% 26% 39% 24%	498
September	1st to 10th	Day	12% 1 6% 18% 41% 23%	330
	11th to 20th	Day	3 1 6% 23% 42% 25%	330
	21st to end	Day	12% 2 5% 29% 37% 16%	330
October	1st to 10th	Day	3 2 10% 33% 39% 13%	330
	11th to 20th	Day	8% 3 26% 33% 25% 5%	330
	21st to end	Day	17% 10% 23% 24% 21% 4	363
November	1st to 10th	Day	19% 6% 27% 28% 15% 5%	330
	11th to 20th	Day	12% 11% 22% 35% 16% 4	330
	21st to end	Day	20% 13% 33% 19% 13% 2	330
December	1st to 10th	Day	17% 8% 34% 27% 11% 3	330
	11th to 20th	Day	16% 13% 35% 23% 10% 2	330
	21st to end	Day	18% 9% 34% 28% 10% 2	363
January	1st to 10th	Night	15% 10% 37% 32% 7%	1050
	11th to 20th	Night	15% 12% 32% 33% 7%	1031
	21st to end	Night	19% 10% 35% 29% 6%	1023
February	1st to 10th	Night	18% 12% 34% 31% 5%	800
	11th to 20th	Night	20% 13% 39% 25% 3	784
	21st to end	Night	21% 11% 42% 22% 3	660
March	1st to 10th	Night	17% 14% 36% 30% 3	644
	11th to 20th	Night	15% 12% 38% 29% 6%	600
	21st to end	Night	11% 10% 47% 29% 3	660
April	1st to 10th	Night	11% 10% 47% 28% 4	600
	11th to 20th	Night	14% 11% 44% 27% 4	593
	21st to end	Night	13% 9% 44% 26% 7%	600
May	1st to 10th	Night	14% 9% 42% 31% 5%	600
	11th to 20th	Night	11% 6% 36% 35% 12%	591
	21st to end	Night	11% 5% 32% 38% 14%	650
June	1st to 10th	Night	4 2 22% 49% 22% 2	600
	11th to 20th	Night	5% 2 24% 53% 17%	600
	21st to end	Night	3 3 15% 49% 29% 2	600
July	1st to 10th	Night	6% 1 9% 48% 32% 4	585
	11th to 20th	Night	3 1 8% 54% 33% 2	582
	21st to end	Night	2 6% 50% 38% 4	657
August	1st to 10th	Night	1 1 4 51% 40% 4	597
	11th to 20th	Night	6% 1 4 46% 39% 3	594
	21st to end	Night	4 3 43% 43% 7%	660
September	1st to 10th	Night	8% 3 8% 40% 36% 6%	600
	11th to 20th	Night	11% 1 5% 41% 39% 3	600
	21st to end	Night	9% 1 9% 41% 37% 3	600
October	1st to 10th	Night	6% 1 13% 47% 31% 3	600
	11th to 20th	Night	10% 3 25% 41% 18% 1	726
	21st to end	Night	14% 7% 27% 34% 16% 1	880
November	1st to 10th	Night	13% 3 24% 44% 15% 1	820
	11th to 20th	Night	9% 7% 29% 39% 15% 1	1029
	21st to end	Night	18% 9% 31% 31% 11% 1	1050
December	1st to 10th	Night	14% 8% 30% 38% 9% 1	1050
	11th to 20th	Night	19% 9% 30% 34% 7%	1050
	21st to end	Night	16% 8% 32% 34% 9%	1155

Page generated at 2026-01-14 00:14:30. Version ac07

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