Buck Bald Mountain
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Buck Bald Mountain clear sky chart from 2005-11-06 to 2025-03-27.

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% 8% 3 7% 5% 5% 5% 4 6% 7% 37%	109360
	Night	13% 9% 3 7% 4 4 4 4 5% 7% 40%	109994
Transparency	Day	41% 8% 11% 20% 16% 4	113155
	Night	39% 8% 11% 20% 17% 4	114337
Seeing	Day	19% 13% 23% 22% 15% 8%	15275
	Night	17% 11% 22% 28% 18% 3	25413

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	14% 14% 6% 6% 3 3 3 3 4 5% 38%	4056
	11th to 20th	Day	13% 8% 8% 11% 3 4 3 2 3 4 41%	4060
	21st to end	Day	17% 15% 4 6% 4 3 3 3 4 6% 34%	4540
February	1st to 10th	Day	17% 11% 3 9% 5% 4 3 3 5% 6% 34%	2000
	11th to 20th	Day	21% 11% 4 8% 5% 3 4 3 4 5% 32%	1948
	21st to end	Day	19% 11% 3 7% 4 4 4 3 4 5% 36%	1650
March	1st to 10th	Day	22% 10% 4 6% 4 4 4 3 6% 6% 32%	3304
	11th to 20th	Day	13% 8% 2 6% 4 4 3 3 4 5% 48%	3590
	21st to end	Day	16% 10% 3 7% 5% 4 4 3 4 6% 38%	3881
April	1st to 10th	Day	11% 7% 3 6% 5% 5% 6% 5% 7% 7% 40%	2171
	11th to 20th	Day	14% 8% 2 6% 4 4 4 4 5% 7% 43%	2254
	21st to end	Day	13% 7% 2 7% 6% 5% 4 3 6% 7% 41%	2455
May	1st to 10th	Day	15% 7% 3 8% 5% 6% 5% 5% 6% 7% 35%	4082
	11th to 20th	Day	17% 9% 3 8% 6% 5% 5% 4 6% 7% 30%	4081
	21st to end	Day	10% 6% 2 7% 6% 6% 6% 4 7% 9% 38%	4476
June	1st to 10th	Day	9% 7% 3 7% 5% 6% 6% 6% 8% 10% 33%	2470
	11th to 20th	Day	5% 4 2 7% 6% 6% 7% 5% 8% 11% 37%	2470
	21st to end	Day	8% 6% 2 6% 6% 5% 7% 5% 7% 11% 36%	2470
July	1st to 10th	Day	6% 6% 3 8% 7% 6% 8% 7% 10% 11% 29%	4120
	11th to 20th	Day	9% 6% 3 8% 7% 6% 7% 5% 7% 8% 33%	4120
	21st to end	Day	14% 11% 4 10% 9% 8% 8% 6% 7% 7% 17%	4466
August	1st to 10th	Day	6% 5% 2 7% 5% 6% 7% 6% 9% 11% 38%	4104
	11th to 20th	Day	8% 6% 2 6% 5% 7% 6% 5% 9% 10% 36%	3860
	21st to end	Day	7% 4 2 6% 5% 5% 6% 5% 7% 8% 44%	4180
September	1st to 10th	Day	11% 6% 2 7% 7% 5% 6% 4 6% 8% 38%	2114
	11th to 20th	Day	13% 7% 3 8% 5% 4 5% 4 5% 8% 37%	2090
	21st to end	Day	13% 6% 2 6% 4 5% 5% 4 5% 6% 44%	2090
October	1st to 10th	Day	9% 6% 2 6% 4 4 4 4 5% 5% 51%	2090
	11th to 20th	Day	12% 7% 2 5% 3 3 3 3 4 6% 53%	1971
	21st to end	Day	13% 6% 2 4 4 3 3 3 5% 7% 51%	2066
November	1st to 10th	Day	12% 6% 2 5% 3 3 4 2 5% 5% 54%	1762
	11th to 20th	Day	12% 8% 3 4 4 3 4 3 6% 5% 47%	1800
	21st to end	Day	14% 9% 3 6% 4 4 4 4 5% 6% 44%	1800
December	1st to 10th	Day	17% 9% 3 6% 3 3 4 3 5% 4 44%	2930
	11th to 20th	Day	15% 14% 6% 9% 6% 5% 4 3 5% 4 30%	3373
	21st to end	Day	14% 11% 7% 7% 4 4 4 3 5% 7% 33%	4466
January	1st to 10th	Night	13% 14% 4 9% 4 3 3 2 4 5% 39%	5889
	11th to 20th	Night	18% 10% 3 8% 4 4 3 3 4 5% 40%	5900
	21st to end	Night	15% 12% 3 7% 4 3 3 3 5% 5% 39%	6398
February	1st to 10th	Night	16% 10% 3 6% 4 4 4 4 4 6% 39%	2400
	11th to 20th	Night	21% 10% 4 8% 5% 4 3 3 4 3 34%	2338
	21st to end	Night	20% 11% 4 7% 4 4 4 3 4 5% 34%	1980
March	1st to 10th	Night	19% 14% 3 7% 5% 5% 4 4 5% 6% 29%	3767
	11th to 20th	Night	13% 7% 2 5% 3 3 4 4 5% 8% 47%	3590
	21st to end	Night	14% 9% 3 7% 5% 4 4 3 5% 6% 40%	3890
April	1st to 10th	Night	13% 7% 2 5% 4 4 4 3 6% 7% 45%	2024
	11th to 20th	Night	12% 8% 2 5% 4 3 4 3 5% 7% 47%	1875
	21st to end	Night	12% 5% 3 5% 5% 4 5% 3 6% 6% 46%	1724
May	1st to 10th	Night	13% 7% 3 7% 6% 5% 5% 5% 6% 8% 36%	2813
	11th to 20th	Night	18% 9% 3 7% 4 5% 4 4 5% 8% 34%	2812
	21st to end	Night	8% 5% 2 7% 5% 6% 5% 5% 8% 10% 39%	3079
June	1st to 10th	Night	7% 6% 2 8% 6% 6% 5% 5% 8% 11% 36%	1710
	11th to 20th	Night	5% 4 1 5% 3 4 6% 7% 8% 13% 45%	1710
	21st to end	Night	6% 6% 2 6% 5% 5% 5% 5% 7% 11% 43%	1710
July	1st to 10th	Night	8% 7% 2 7% 6% 6% 6% 5% 9% 11% 33%	2840
	11th to 20th	Night	8% 5% 2 5% 5% 5% 6% 5% 8% 11% 41%	2840
	21st to end	Night	12% 11% 4 10% 7% 6% 6% 5% 8% 8% 22%	3087
August	1st to 10th	Night	7% 4 2 6% 5% 5% 5% 5% 8% 11% 42%	2825
	11th to 20th	Night	9% 7% 2 6% 4 5% 5% 4 7% 8% 44%	2965
	21st to end	Night	6% 5% 2 5% 4 4 5% 5% 6% 10% 49%	3476
September	1st to 10th	Night	10% 5% 3 8% 5% 5% 5% 4 6% 7% 41%	2047
	11th to 20th	Night	10% 6% 3 8% 5% 4 5% 5% 6% 8% 40%	2090
	21st to end	Night	11% 5% 2 6% 4 4 4 4 6% 7% 47%	2090
October	1st to 10th	Night	11% 5% 2 5% 3 2 3 3 4 5% 58%	2090
	11th to 20th	Night	13% 5% 2 4 3 4 4 2 4 4 53%	2208
	21st to end	Night	12% 7% 2 4 3 3 3 3 4 6% 53%	2529
November	1st to 10th	Night	10% 6% 2 6% 4 4 3 3 5% 5% 51%	2536
	11th to 20th	Night	13% 9% 2 5% 3 3 3 3 4 7% 48%	2600
	21st to end	Night	14% 9% 3 5% 3 4 4 3 5% 6% 43%	2600
December	1st to 10th	Night	18% 10% 3 8% 3 3 3 2 4 5% 40%	4250
	11th to 20th	Night	17% 12% 5% 8% 4 4 4 3 5% 5% 32%	4822
	21st to end	Night	13% 12% 6% 9% 4 4 4 3 5% 7% 34%	6490

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	46% 5% 6% 18% 24% 2	4057
	11th to 20th	Day	44% 4 6% 14% 28% 4	4060
	21st to end	Day	49% 4 7% 19% 16% 5%	4540
February	1st to 10th	Day	50% 5% 7% 18% 17% 3	2000
	11th to 20th	Day	54% 5% 6% 16% 16% 4	1958
	21st to end	Day	50% 4 7% 13% 20% 5%	1650
March	1st to 10th	Day	50% 6% 9% 14% 14% 7%	3304
	11th to 20th	Day	37% 6% 8% 20% 22% 8%	3590
	21st to end	Day	46% 6% 8% 24% 13% 3	3881
April	1st to 10th	Day	40% 8% 11% 21% 17% 3	2171
	11th to 20th	Day	41% 6% 8% 17% 23% 4	2254
	21st to end	Day	41% 7% 10% 26% 14% 2	2455
May	1st to 10th	Day	44% 10% 11% 20% 13% 2	4120
	11th to 20th	Day	49% 10% 11% 22% 8% 1	4085
	21st to end	Day	38% 11% 12% 22% 15% 1	4489
June	1st to 10th	Day	42% 12% 16% 21% 9% 1	2470
	11th to 20th	Day	36% 12% 19% 21% 12% 1	2470
	21st to end	Day	39% 12% 16% 18% 12% 3	2470
July	1st to 10th	Day	39% 16% 20% 18% 6% 1	4055
	11th to 20th	Day	44% 12% 18% 19% 6% 1	4051
	21st to end	Day	62% 12% 11% 11% 4	4324
August	1st to 10th	Day	34% 14% 18% 25% 8%	4091
	11th to 20th	Day	34% 12% 20% 21% 12% 1	3899
	21st to end	Day	33% 11% 12% 31% 11% 1	4179
September	1st to 10th	Day	42% 9% 13% 16% 15% 4	2114
	11th to 20th	Day	43% 9% 12% 17% 17% 1	2090
	21st to end	Day	38% 8% 13% 17% 19% 6%	2090
October	1st to 10th	Day	24% 7% 8% 17% 33% 11%	3480
	11th to 20th	Day	21% 5% 6% 21% 28% 19%	3250
	21st to end	Day	25% 6% 8% 27% 24% 11%	3380
November	1st to 10th	Day	32% 6% 7% 17% 30% 8%	1762
	11th to 20th	Day	36% 5% 6% 21% 25% 8%	1800
	21st to end	Day	41% 5% 8% 20% 23% 5%	1800
December	1st to 10th	Day	41% 5% 7% 17% 25% 5%	2930
	11th to 20th	Day	54% 5% 7% 16% 15% 3	3370
	21st to end	Day	46% 6% 12% 24% 10% 1	4466
January	1st to 10th	Night	45% 5% 8% 19% 22% 2	5889
	11th to 20th	Night	45% 6% 6% 16% 20% 8%	5900
	21st to end	Night	45% 5% 6% 18% 20% 5%	6398
February	1st to 10th	Night	46% 5% 10% 17% 19% 3	2400
	11th to 20th	Night	54% 5% 6% 16% 15% 5%	2339
	21st to end	Night	51% 6% 6% 16% 16% 5%	1980
March	1st to 10th	Night	50% 9% 10% 12% 15% 4	3767
	11th to 20th	Night	33% 6% 10% 22% 19% 9%	3590
	21st to end	Night	43% 7% 9% 21% 16% 3	3890
April	1st to 10th	Night	36% 7% 12% 21% 21% 4	2024
	11th to 20th	Night	35% 7% 10% 21% 21% 6%	1875
	21st to end	Night	35% 8% 12% 29% 15% 1	1724
May	1st to 10th	Night	39% 13% 14% 22% 11% 1	2840
	11th to 20th	Night	44% 10% 14% 21% 10%	2813
	21st to end	Night	31% 15% 15% 26% 12% 1	3087
June	1st to 10th	Night	39% 11% 18% 22% 10% 1	1710
	11th to 20th	Night	26% 13% 22% 27% 10% 1	1710
	21st to end	Night	32% 13% 18% 21% 12% 4	1710
July	1st to 10th	Night	39% 16% 20% 19% 6% 1	2795
	11th to 20th	Night	32% 12% 25% 23% 6% 2	2786
	21st to end	Night	55% 13% 14% 13% 4 1	2988
August	1st to 10th	Night	31% 13% 20% 27% 8%	2814
	11th to 20th	Night	32% 12% 21% 23% 11% 1	2992
	21st to end	Night	27% 10% 18% 32% 12% 1	3476
September	1st to 10th	Night	39% 10% 15% 18% 14% 4	2047
	11th to 20th	Night	37% 12% 14% 18% 18% 1	2090
	21st to end	Night	34% 9% 11% 20% 20% 5%	2090
October	1st to 10th	Night	23% 6% 13% 18% 26% 14%	3480
	11th to 20th	Night	22% 5% 7% 19% 32% 16%	3668
	21st to end	Night	22% 7% 7% 26% 26% 12%	4165
November	1st to 10th	Night	34% 5% 8% 20% 24% 8%	2536
	11th to 20th	Night	37% 4 7% 20% 24% 9%	2600
	21st to end	Night	41% 4 7% 22% 21% 4	2600
December	1st to 10th	Night	44% 5% 8% 15% 23% 4	4250
	11th to 20th	Night	50% 7% 7% 16% 17% 3	4824
	21st to end	Night	48% 7% 12% 21% 11% 1	6490

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	33% 27% 30% 6% 3	300
	11th to 20th	Day	32% 27% 26% 12% 3	300
	21st to end	Day	26% 33% 29% 10% 2	330
February	1st to 10th	Day	27% 24% 37% 11% 1	300
	11th to 20th	Day	41% 27% 24% 8%	300
	21st to end	Day	39% 25% 30% 6%	249
March	1st to 10th	Day	32% 23% 27% 14% 4	345
	11th to 20th	Day	27% 23% 28% 16% 5% 1	500
	21st to end	Day	28% 20% 31% 16% 5%	530
April	1st to 10th	Day	24% 18% 28% 17% 11% 1	460
	11th to 20th	Day	21% 20% 27% 20% 10% 3	452
	21st to end	Day	21% 15% 28% 23% 11% 3	460
May	1st to 10th	Day	17% 15% 32% 21% 9% 6%	463
	11th to 20th	Day	15% 9% 26% 27% 15% 7%	487
	21st to end	Day	13% 9% 20% 29% 17% 12%	529
June	1st to 10th	Day	11% 8% 20% 28% 22% 10%	490
	11th to 20th	Day	7% 4 20% 29% 25% 15%	490
	21st to end	Day	9% 4 23% 27% 21% 15%	490
July	1st to 10th	Day	11% 5% 14% 25% 28% 18%	485
	11th to 20th	Day	10% 5% 10% 30% 26% 20%	484
	21st to end	Day	12% 4 10% 25% 29% 20%	532
August	1st to 10th	Day	12% 5% 17% 25% 20% 21%	486
	11th to 20th	Day	13% 6% 15% 28% 23% 15%	479
	21st to end	Day	15% 3 12% 25% 28% 18%	539
September	1st to 10th	Day	11% 6% 13% 27% 29% 14%	490
	11th to 20th	Day	16% 6% 17% 24% 24% 13%	490
	21st to end	Day	16% 7% 16% 30% 25% 6%	490
October	1st to 10th	Day	13% 8% 23% 29% 21% 7%	490
	11th to 20th	Day	16% 12% 27% 25% 17% 2	490
	21st to end	Day	18% 12% 25% 28% 14% 3	515
November	1st to 10th	Day	19% 18% 29% 21% 13% 1	300
	11th to 20th	Day	21% 18% 36% 20% 5%	300
	21st to end	Day	21% 21% 38% 13% 7%	300
December	1st to 10th	Day	30% 24% 28% 15% 3	300
	11th to 20th	Day	28% 19% 32% 17% 4	300
	21st to end	Day	27% 25% 29% 17% 2	330
January	1st to 10th	Night	26% 22% 29% 20% 4	800
	11th to 20th	Night	27% 21% 26% 21% 5%	800
	21st to end	Night	23% 19% 31% 24% 3	880
February	1st to 10th	Night	23% 17% 29% 28% 4	800
	11th to 20th	Night	30% 21% 29% 19% 1	783
	21st to end	Night	28% 22% 30% 17% 2	660
March	1st to 10th	Night	23% 18% 31% 24% 4	800
	11th to 20th	Night	24% 18% 28% 22% 7% 1	800
	21st to end	Night	20% 17% 29% 25% 8%	863
April	1st to 10th	Night	17% 18% 28% 28% 9% 1	694
	11th to 20th	Night	15% 17% 29% 28% 11% 1	563
	21st to end	Night	14% 9% 27% 36% 13% 1	570
May	1st to 10th	Night	11% 10% 29% 31% 17% 2	570
	11th to 20th	Night	14% 7% 20% 33% 21% 4	561
	21st to end	Night	10% 3 15% 37% 28% 7%	617
June	1st to 10th	Night	8% 4 15% 36% 32% 5%	570
	11th to 20th	Night	6% 3 12% 33% 36% 11%	570
	21st to end	Night	7% 2 9% 36% 37% 8%	570
July	1st to 10th	Night	10% 2 8% 26% 45% 9%	555
	11th to 20th	Night	10% 3 6% 26% 43% 12%	552
	21st to end	Night	10% 1 7% 25% 47% 9%	624
August	1st to 10th	Night	10% 3 7% 29% 41% 11%	567
	11th to 20th	Night	9% 2 10% 30% 43% 5%	564
	21st to end	Night	11% 3 10% 28% 40% 8%	627
September	1st to 10th	Night	11% 2 13% 28% 38% 8%	717
	11th to 20th	Night	12% 4 15% 33% 33% 4	760
	21st to end	Night	14% 4 17% 34% 29% 2	760
October	1st to 10th	Night	12% 7% 19% 31% 25% 5%	760
	11th to 20th	Night	16% 8% 25% 31% 18% 2	760
	21st to end	Night	16% 11% 22% 33% 16% 2	836
November	1st to 10th	Night	15% 8% 23% 35% 16% 2	780
	11th to 20th	Night	18% 17% 24% 29% 12% 1	800
	21st to end	Night	21% 15% 27% 25% 11% 1	800
December	1st to 10th	Night	25% 19% 24% 27% 7%	800
	11th to 20th	Night	24% 14% 27% 28% 8%	800
	21st to end	Night	25% 18% 25% 27% 5%	880

Page generated at 2025-03-24 09:04:28. Version ac07

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