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 2024-02-20.

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 6% 6% 3 5% 5% 6% 7% 37%	78750
	Night	13% 8% 3 6% 5% 3 4 5% 5% 7% 40%	80437
Transparency	Day	44% 8% 11% 18% 16% 3	78473
	Night	41% 8% 11% 19% 17% 4	80233
Seeing	Day	18% 13% 23% 22% 16% 8%	13818
	Night	17% 11% 21% 28% 19% 3	23958

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% 13% 6% 6% 5% 3 4 4 5% 6% 33%	2836
	11th to 20th	Day	17% 8% 7% 11% 5% 3 3 3 4 4 34%	2840
	21st to end	Day	19% 17% 4 5% 4 2 3 4 4 5% 33%	3170
February	1st to 10th	Day	18% 10% 4 8% 5% 2 3 4 4 6% 34%	1900
	11th to 20th	Day	20% 10% 5% 7% 5% 2 3 4 4 5% 33%	1838
	21st to end	Day	20% 11% 4 6% 4 3 4 4 4 5% 34%	1480
March	1st to 10th	Day	16% 9% 3 6% 4 3 5% 4 6% 6% 38%	1840
	11th to 20th	Day	18% 9% 3 7% 6% 4 4 5% 5% 6% 34%	1980
	21st to end	Day	15% 11% 3 6% 5% 3 6% 5% 4 6% 36%	2178
April	1st to 10th	Day	11% 7% 3 5% 5% 3 6% 6% 6% 7% 41%	2056
	11th to 20th	Day	14% 7% 2 5% 5% 3 4 5% 4 7% 43%	2134
	21st to end	Day	13% 6% 2 6% 6% 4 5% 4 6% 7% 41%	2325
May	1st to 10th	Day	13% 5% 3 5% 5% 4 6% 5% 6% 7% 42%	2340
	11th to 20th	Day	14% 6% 2 7% 8% 4 6% 6% 6% 8% 34%	2301
	21st to end	Day	10% 6% 2 7% 6% 4 7% 5% 6% 9% 36%	2531
June	1st to 10th	Day	9% 7% 2 6% 6% 4 7% 7% 8% 10% 34%	2340
	11th to 20th	Day	6% 4 3 6% 7% 4 7% 6% 8% 11% 38%	2340
	21st to end	Day	8% 5% 3 6% 7% 4 7% 7% 7% 12% 36%	2340
July	1st to 10th	Day	9% 7% 4 7% 7% 4 7% 7% 9% 11% 29%	2340
	11th to 20th	Day	10% 5% 4 7% 8% 5% 7% 8% 8% 9% 28%	2340
	21st to end	Day	10% 7% 3 6% 8% 5% 8% 8% 8% 9% 27%	2547
August	1st to 10th	Day	10% 5% 3 6% 7% 4 7% 8% 9% 10% 31%	2327
	11th to 20th	Day	11% 6% 4 6% 7% 5% 6% 6% 7% 10% 31%	2203
	21st to end	Day	13% 6% 3 7% 7% 5% 7% 6% 8% 8% 30%	2376
September	1st to 10th	Day	11% 6% 2 6% 8% 4 6% 5% 7% 8% 37%	2003
	11th to 20th	Day	13% 7% 3 6% 7% 3 5% 5% 5% 8% 37%	1980
	21st to end	Day	12% 5% 3 5% 5% 3 5% 5% 4 6% 46%	1980
October	1st to 10th	Day	9% 5% 2 5% 5% 4 4 5% 5% 6% 51%	1980
	11th to 20th	Day	13% 7% 2 4 3 2 3 4 4 6% 52%	1868
	21st to end	Day	14% 6% 1 4 4 2 3 4 5% 7% 50%	1958
November	1st to 10th	Day	12% 5% 3 4 3 2 4 2 4 6% 55%	1672
	11th to 20th	Day	11% 7% 4 4 4 3 4 4 6% 5% 48%	1710
	21st to end	Day	15% 8% 3 5% 4 3 4 4 4 6% 44%	1710
December	1st to 10th	Day	20% 10% 3 7% 5% 2 5% 5% 5% 4 34%	1710
	11th to 20th	Day	15% 11% 5% 6% 5% 3 5% 4 5% 5% 36%	2153
	21st to end	Day	16% 12% 7% 6% 5% 3 4 4 5% 7% 32%	3124
January	1st to 10th	Night	16% 15% 4 6% 5% 2 4 3 4 5% 35%	4109
	11th to 20th	Night	20% 10% 4 7% 5% 3 3 4 4 5% 36%	4120
	21st to end	Night	20% 16% 3 6% 4 2 3 4 4 4 33%	4468
February	1st to 10th	Night	16% 9% 4 6% 5% 3 4 5% 4 6% 40%	2280
	11th to 20th	Night	21% 9% 5% 7% 5% 3 4 4 4 3 35%	2213
	21st to end	Night	21% 11% 4 6% 5% 3 4 4 4 5% 32%	1776
March	1st to 10th	Night	15% 8% 4 6% 5% 3 4 4 4 6% 41%	2119
	11th to 20th	Night	17% 9% 3 7% 4 2 4 5% 5% 7% 38%	1980
	21st to end	Night	14% 9% 4 5% 6% 4 5% 4 5% 6% 39%	2178
April	1st to 10th	Night	13% 6% 2 4 4 3 4 4 6% 8% 47%	1918
	11th to 20th	Night	11% 7% 2 5% 4 3 4 3 5% 8% 48%	1775
	21st to end	Night	12% 5% 3 5% 5% 2 6% 4 5% 7% 46%	1634
May	1st to 10th	Night	11% 5% 2 5% 6% 3 4 6% 6% 8% 43%	1620
	11th to 20th	Night	11% 6% 3 6% 6% 3 5% 5% 6% 9% 41%	1592
	21st to end	Night	7% 4 3 6% 7% 4 6% 6% 7% 10% 39%	1744
June	1st to 10th	Night	7% 5% 2 6% 7% 4 5% 7% 8% 11% 37%	1620
	11th to 20th	Night	5% 3 1 4 4 3 5% 9% 8% 12% 46%	1620
	21st to end	Night	6% 5% 2 5% 6% 3 5% 6% 7% 11% 44%	1620
July	1st to 10th	Night	9% 6% 3 5% 7% 4 6% 7% 8% 11% 35%	1620
	11th to 20th	Night	9% 4 2 4 5% 4 6% 7% 9% 13% 37%	1620
	21st to end	Night	7% 5% 2 5% 6% 4 6% 8% 10% 11% 36%	1771
August	1st to 10th	Night	8% 3 2 5% 7% 4 6% 7% 8% 11% 39%	1611
	11th to 20th	Night	8% 6% 2 6% 6% 4 6% 7% 7% 10% 39%	1694
	21st to end	Night	10% 6% 3 6% 6% 4 5% 6% 7% 11% 37%	1980
September	1st to 10th	Night	10% 5% 3 7% 6% 4 6% 5% 6% 8% 42%	1939
	11th to 20th	Night	11% 6% 3 6% 6% 3 4 6% 6% 8% 41%	1980
	21st to end	Night	9% 5% 2 5% 5% 3 5% 5% 6% 7% 49%	1980
October	1st to 10th	Night	12% 5% 2 4 3 1 3 3 4 5% 58%	1980
	11th to 20th	Night	14% 5% 2 4 4 3 4 3 4 5% 51%	2091
	21st to end	Night	12% 7% 2 4 3 2 3 4 4 6% 52%	2395
November	1st to 10th	Night	11% 5% 2 5% 4 3 3 3 5% 5% 53%	2406
	11th to 20th	Night	13% 8% 2 5% 4 2 3 4 4 6% 49%	2470
	21st to end	Night	15% 8% 3 5% 4 3 4 4 4 6% 43%	2470
December	1st to 10th	Night	19% 10% 4 7% 5% 2 5% 4 5% 6% 32%	2470
	11th to 20th	Night	15% 12% 4 7% 4 3 3 3 4 6% 38%	3042
	21st to end	Night	15% 13% 5% 7% 6% 3 5% 5% 5% 7% 29%	4532

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	48% 5% 7% 15% 22% 2	2837
	11th to 20th	Day	50% 5% 8% 13% 21% 2	2840
	21st to end	Day	52% 4 7% 18% 17% 2	3170
February	1st to 10th	Day	52% 4 7% 17% 17% 3	1900
	11th to 20th	Day	52% 5% 6% 16% 16% 4	1848
	21st to end	Day	52% 4 8% 12% 18% 6%	1480
March	1st to 10th	Day	45% 6% 9% 14% 19% 7%	1840
	11th to 20th	Day	49% 7% 11% 15% 14% 4	1980
	21st to end	Day	48% 7% 11% 21% 12% 2	2178
April	1st to 10th	Day	39% 8% 11% 22% 17% 3	2056
	11th to 20th	Day	41% 6% 8% 18% 23% 4	2134
	21st to end	Day	41% 7% 11% 26% 14% 2	2325
May	1st to 10th	Day	40% 8% 14% 21% 15% 3	2340
	11th to 20th	Day	46% 10% 12% 20% 11% 1	2305
	21st to end	Day	41% 11% 13% 21% 12% 2	2531
June	1st to 10th	Day	42% 12% 16% 21% 9% 1	2340
	11th to 20th	Day	36% 12% 19% 21% 11% 1	2340
	21st to end	Day	39% 12% 16% 18% 12% 2	2340
July	1st to 10th	Day	44% 14% 17% 17% 7% 1	2275
	11th to 20th	Day	47% 14% 16% 12% 10% 2	2271
	21st to end	Day	45% 15% 16% 17% 7%	2405
August	1st to 10th	Day	42% 15% 18% 18% 6% 1	2314
	11th to 20th	Day	45% 13% 15% 15% 10% 1	2203
	21st to end	Day	48% 13% 13% 15% 9% 2	2376
September	1st to 10th	Day	42% 9% 13% 17% 14% 4	2003
	11th to 20th	Day	43% 9% 12% 18% 17% 2	1980
	21st to end	Day	37% 8% 12% 18% 20% 6%	1980
October	1st to 10th	Day	32% 8% 9% 19% 26% 6%	1980
	11th to 20th	Day	32% 7% 9% 22% 22% 8%	1868
	21st to end	Day	34% 5% 7% 23% 25% 7%	1958
November	1st to 10th	Day	32% 5% 7% 17% 31% 8%	1672
	11th to 20th	Day	36% 5% 6% 20% 25% 8%	1710
	21st to end	Day	41% 5% 7% 19% 23% 5%	1710
December	1st to 10th	Day	52% 6% 7% 16% 16% 3	1710
	11th to 20th	Day	48% 6% 8% 14% 20% 4	2150
	21st to end	Day	50% 6% 9% 21% 13% 2	3124
January	1st to 10th	Night	49% 5% 7% 17% 19% 2	4109
	11th to 20th	Night	49% 6% 6% 15% 16% 8%	4120
	21st to end	Night	54% 5% 6% 14% 19% 3	4468
February	1st to 10th	Night	46% 4 10% 17% 19% 4	2280
	11th to 20th	Night	53% 5% 5% 16% 15% 5%	2214
	21st to end	Night	54% 6% 6% 15% 15% 4	1776
March	1st to 10th	Night	44% 5% 9% 15% 19% 7%	2119
	11th to 20th	Night	44% 7% 11% 20% 15% 3	1980
	21st to end	Night	46% 7% 10% 22% 14% 2	2178
April	1st to 10th	Night	35% 7% 12% 22% 22% 3	1918
	11th to 20th	Night	34% 6% 11% 22% 21% 6%	1775
	21st to end	Night	35% 8% 12% 29% 15% 1	1634
May	1st to 10th	Night	35% 10% 13% 23% 17% 2	1620
	11th to 20th	Night	39% 11% 16% 23% 11%	1593
	21st to end	Night	34% 14% 15% 25% 10% 2	1745
June	1st to 10th	Night	38% 11% 18% 22% 9% 1	1620
	11th to 20th	Night	27% 13% 23% 26% 10% 1	1620
	21st to end	Night	31% 13% 19% 22% 12% 4	1620
July	1st to 10th	Night	38% 14% 18% 19% 10% 1	1575
	11th to 20th	Night	33% 14% 24% 17% 9% 4	1566
	21st to end	Night	35% 15% 20% 22% 7% 1	1672
August	1st to 10th	Night	35% 15% 20% 23% 7%	1600
	11th to 20th	Night	37% 13% 18% 18% 13% 1	1694
	21st to end	Night	39% 11% 19% 21% 8% 2	1980
September	1st to 10th	Night	39% 10% 15% 19% 13% 4	1939
	11th to 20th	Night	37% 12% 14% 19% 19% 1	1980
	21st to end	Night	33% 9% 11% 21% 21% 6%	1980
October	1st to 10th	Night	29% 5% 11% 20% 28% 6%	1980
	11th to 20th	Night	34% 6% 10% 21% 22% 7%	2091
	21st to end	Night	34% 4 5% 22% 27% 8%	2395
November	1st to 10th	Night	34% 5% 8% 21% 25% 8%	2406
	11th to 20th	Night	37% 4 6% 20% 23% 9%	2470
	21st to end	Night	42% 4 7% 22% 21% 4	2470
December	1st to 10th	Night	51% 7% 9% 16% 13% 4	2470
	11th to 20th	Night	45% 6% 7% 16% 23% 4	3044
	21st to end	Night	51% 7% 9% 19% 11% 1	4532

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	31% 25% 33% 7% 3	270
	11th to 20th	Day	30% 27% 26% 13% 3	270
	21st to end	Day	27% 32% 30% 9% 2	297
February	1st to 10th	Day	29% 23% 36% 11% 1	270
	11th to 20th	Day	39% 28% 25% 8%	267
	21st to end	Day	39% 25% 29% 7%	198
March	1st to 10th	Day	27% 25% 31% 15% 3	280
	11th to 20th	Day	27% 23% 27% 17% 5% 1	420
	21st to end	Day	27% 19% 31% 17% 6%	462
April	1st to 10th	Day	23% 18% 27% 19% 12% 1	420
	11th to 20th	Day	19% 20% 27% 21% 10% 3	412
	21st to end	Day	21% 15% 26% 23% 11% 3	420
May	1st to 10th	Day	17% 15% 31% 21% 10% 6%	423
	11th to 20th	Day	14% 8% 27% 27% 16% 8%	447
	21st to end	Day	14% 9% 17% 29% 19% 13%	485
June	1st to 10th	Day	12% 7% 18% 28% 24% 11%	450
	11th to 20th	Day	7% 5% 18% 28% 26% 16%	450
	21st to end	Day	10% 4 23% 26% 21% 16%	450
July	1st to 10th	Day	11% 4 13% 24% 28% 20%	445
	11th to 20th	Day	9% 5% 9% 28% 27% 21%	444
	21st to end	Day	11% 3 9% 24% 31% 22%	488
August	1st to 10th	Day	13% 5% 14% 25% 21% 23%	446
	11th to 20th	Day	13% 5% 13% 28% 25% 17%	439
	21st to end	Day	16% 3 13% 23% 28% 17%	495
September	1st to 10th	Day	12% 6% 12% 26% 30% 15%	450
	11th to 20th	Day	16% 6% 14% 24% 26% 15%	450
	21st to end	Day	14% 6% 15% 31% 27% 7%	450
October	1st to 10th	Day	14% 8% 23% 27% 22% 7%	450
	11th to 20th	Day	16% 13% 26% 24% 18% 3	450
	21st to end	Day	20% 12% 24% 27% 14% 3	473
November	1st to 10th	Day	20% 18% 26% 22% 13% 1	270
	11th to 20th	Day	20% 18% 36% 20% 6%	270
	21st to end	Day	19% 19% 40% 13% 8%	270
December	1st to 10th	Day	30% 21% 29% 16% 4	270
	11th to 20th	Day	26% 20% 32% 17% 5%	270
	21st to end	Day	27% 25% 30% 16% 2	297
January	1st to 10th	Night	25% 22% 28% 20% 4	760
	11th to 20th	Night	27% 20% 26% 22% 5%	760
	21st to end	Night	23% 19% 30% 25% 3	836
February	1st to 10th	Night	22% 17% 29% 29% 4	760
	11th to 20th	Night	29% 21% 30% 19% 2	742
	21st to end	Night	30% 22% 29% 17% 3	592
March	1st to 10th	Night	20% 18% 33% 25% 4	720
	11th to 20th	Night	23% 18% 27% 22% 8% 1	720
	21st to end	Night	20% 17% 29% 25% 9%	792
April	1st to 10th	Night	16% 16% 28% 29% 9% 1	658
	11th to 20th	Night	14% 17% 29% 27% 12% 1	533
	21st to end	Night	14% 9% 26% 36% 13% 1	540
May	1st to 10th	Night	11% 9% 30% 31% 17% 2	540
	11th to 20th	Night	13% 6% 21% 33% 22% 5%	531
	21st to end	Night	10% 3 14% 37% 29% 7%	584
June	1st to 10th	Night	8% 4 14% 36% 34% 5%	540
	11th to 20th	Night	6% 3 11% 32% 37% 11%	540
	21st to end	Night	6% 2 9% 35% 38% 9%	540
July	1st to 10th	Night	10% 2 8% 26% 45% 10%	525
	11th to 20th	Night	10% 3 7% 25% 42% 13%	522
	21st to end	Night	9% 1 6% 25% 50% 9%	591
August	1st to 10th	Night	10% 2 7% 27% 42% 12%	537
	11th to 20th	Night	9% 2 8% 30% 45% 6%	534
	21st to end	Night	11% 3 10% 26% 40% 8%	594
September	1st to 10th	Night	11% 3 11% 28% 40% 8%	679
	11th to 20th	Night	12% 3 14% 33% 33% 4	720
	21st to end	Night	13% 3 17% 34% 30% 3	720
October	1st to 10th	Night	13% 8% 19% 29% 26% 5%	720
	11th to 20th	Night	17% 8% 25% 29% 19% 2	720
	21st to end	Night	17% 11% 22% 31% 17% 2	792
November	1st to 10th	Night	15% 8% 22% 35% 17% 3	740
	11th to 20th	Night	17% 16% 25% 28% 13% 1	760
	21st to end	Night	21% 15% 26% 26% 12% 1	760
December	1st to 10th	Night	24% 18% 24% 27% 7%	760
	11th to 20th	Night	23% 13% 27% 28% 8%	760
	21st to end	Night	25% 18% 25% 27% 5%	836

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