Brasstown Bald
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Brasstown Bald clear sky chart from 2005-11-06 to 2024-12-06.

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% 7% 3 7% 5% 5% 5% 4 6% 7% 37%	101279
	Night	13% 8% 3 7% 5% 4 4 4 5% 7% 39%	98402
Transparency	Day	42% 8% 11% 18% 16% 5%	105086
	Night	40% 8% 12% 18% 17% 5%	102734
Seeing	Day	19% 13% 23% 21% 16% 8%	15010
	Night	17% 12% 20% 28% 20% 4	25058

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% 9% 4 8% 4 4 4 3 7% 6% 37%	2836
	11th to 20th	Day	15% 7% 2 7% 6% 6% 4 3 4 5% 41%	2840
	21st to end	Day	22% 12% 3 5% 3 3 3 2 3 5% 39%	3132
February	1st to 10th	Day	17% 11% 3 7% 5% 4 3 4 4 6% 37%	1900
	11th to 20th	Day	18% 10% 3 7% 5% 4 4 3 4 6% 36%	1848
	21st to end	Day	20% 9% 3 7% 5% 4 3 3 4 6% 36%	1570
March	1st to 10th	Day	23% 9% 3 6% 3 4 3 3 5% 6% 36%	3248
	11th to 20th	Day	13% 7% 2 6% 4 4 3 3 4 6% 49%	3480
	21st to end	Day	16% 9% 3 7% 5% 3 4 3 4 5% 39%	3815
April	1st to 10th	Day	12% 7% 2 6% 6% 5% 4 5% 7% 6% 40%	2114
	11th to 20th	Day	14% 7% 3 7% 4 5% 4 4 6% 6% 41%	2263
	21st to end	Day	12% 6% 2 5% 5% 4 5% 4 6% 7% 43%	2470
May	1st to 10th	Day	14% 9% 3 7% 5% 5% 5% 4 5% 6% 35%	4082
	11th to 20th	Day	19% 9% 3 8% 6% 5% 5% 4 6% 6% 29%	4081
	21st to end	Day	9% 6% 2 7% 6% 6% 6% 5% 7% 10% 37%	4476
June	1st to 10th	Day	11% 7% 3 9% 8% 7% 6% 5% 7% 8% 29%	2470
	11th to 20th	Day	6% 6% 2 8% 6% 7% 6% 7% 9% 9% 34%	2470
	21st to end	Day	8% 6% 3 8% 6% 7% 6% 5% 8% 11% 33%	2470
July	1st to 10th	Day	6% 6% 3 10% 8% 8% 9% 6% 9% 10% 26%	4120
	11th to 20th	Day	10% 6% 3 9% 8% 7% 7% 5% 8% 9% 28%	4120
	21st to end	Day	13% 10% 5% 13% 9% 8% 8% 6% 7% 6% 15%	4466
August	1st to 10th	Day	7% 7% 2 8% 7% 6% 6% 6% 9% 12% 30%	4104
	11th to 20th	Day	8% 5% 3 6% 6% 6% 7% 6% 9% 12% 32%	3926
	21st to end	Day	8% 5% 2 7% 5% 6% 6% 5% 6% 7% 43%	4158
September	1st to 10th	Day	11% 7% 3 9% 6% 6% 6% 5% 6% 7% 34%	2090
	11th to 20th	Day	15% 9% 3 7% 5% 5% 6% 4 6% 6% 33%	2090
	21st to end	Day	14% 7% 2 7% 5% 5% 4 3 5% 7% 41%	2090
October	1st to 10th	Day	12% 6% 2 5% 3 4 4 3 5% 5% 51%	2090
	11th to 20th	Day	11% 7% 2 5% 3 4 4 3 4 5% 52%	1947
	21st to end	Day	13% 6% 2 5% 4 3 3 3 3 5% 53%	2090
November	1st to 10th	Day	11% 8% 2 4 3 3 4 2 4 5% 53%	1791
	11th to 20th	Day	13% 6% 2 5% 3 4 3 4 4 7% 49%	1800
	21st to end	Day	14% 7% 3 5% 4 4 4 3 5% 7% 45%	1800
December	1st to 10th	Day	20% 8% 3 6% 5% 4 4 4 5% 5% 36%	1755
	11th to 20th	Day	15% 7% 3 7% 4 5% 4 4 4 6% 41%	2153
	21st to end	Day	19% 8% 4 7% 5% 3 4 3 5% 7% 35%	3124
January	1st to 10th	Night	16% 12% 4 6% 4 4 3 3 4 5% 40%	4109
	11th to 20th	Night	15% 10% 3 7% 4 3 4 3 4 7% 40%	4120
	21st to end	Night	23% 13% 3 7% 4 3 3 2 3 4 36%	4521
February	1st to 10th	Night	13% 8% 4 7% 5% 4 4 3 5% 7% 41%	2280
	11th to 20th	Night	19% 9% 3 7% 5% 4 3 3 4 4 38%	2218
	21st to end	Night	20% 10% 4 8% 4 4 4 3 4 5% 34%	1884
March	1st to 10th	Night	21% 12% 4 9% 5% 4 4 2 4 4 29%	3605
	11th to 20th	Night	11% 7% 2 5% 3 4 4 3 7% 7% 47%	3480
	21st to end	Night	15% 7% 3 9% 5% 4 4 3 4 6% 39%	3817
April	1st to 10th	Night	12% 8% 3 5% 4 3 4 3 5% 7% 46%	2081
	11th to 20th	Night	13% 7% 2 6% 4 4 4 3 5% 7% 46%	1865
	21st to end	Night	10% 7% 3 5% 4 4 4 4 5% 5% 48%	1710
May	1st to 10th	Night	12% 9% 3 8% 5% 5% 4 4 6% 9% 36%	2813
	11th to 20th	Night	17% 10% 3 8% 5% 4 4 3 5% 7% 33%	2812
	21st to end	Night	7% 5% 2 6% 5% 6% 5% 5% 7% 12% 41%	3079
June	1st to 10th	Night	8% 7% 3 8% 7% 6% 5% 5% 8% 9% 34%	1710
	11th to 20th	Night	5% 5% 2 6% 5% 5% 7% 4 8% 12% 42%	1710
	21st to end	Night	8% 5% 2 5% 4 5% 5% 5% 7% 11% 42%	1710
July	1st to 10th	Night	9% 7% 3 11% 7% 7% 6% 4 7% 10% 30%	2840
	11th to 20th	Night	7% 6% 3 8% 6% 5% 6% 5% 9% 12% 34%	2840
	21st to end	Night	12% 11% 5% 12% 7% 6% 5% 5% 7% 7% 22%	3087
August	1st to 10th	Night	7% 7% 3 8% 7% 5% 5% 5% 8% 12% 33%	2825
	11th to 20th	Night	10% 7% 3 8% 5% 5% 5% 4 6% 9% 40%	2899
	21st to end	Night	7% 4 2 6% 4 4 5% 4 7% 9% 47%	3476
September	1st to 10th	Night	10% 7% 2 7% 5% 5% 5% 5% 7% 9% 38%	2079
	11th to 20th	Night	14% 7% 3 7% 4 5% 4 4 6% 8% 37%	2090
	21st to end	Night	13% 6% 2 6% 4 4 4 4 5% 7% 46%	2090
October	1st to 10th	Night	12% 6% 2 4 3 2 4 3 4 5% 54%	2090
	11th to 20th	Night	11% 6% 2 6% 4 4 4 3 4 5% 50%	2232
	21st to end	Night	11% 7% 2 6% 4 3 3 2 4 5% 54%	2508
November	1st to 10th	Night	12% 5% 2 7% 4 4 3 3 4 6% 50%	2506
	11th to 20th	Night	13% 7% 3 5% 4 3 3 3 4 6% 48%	2600
	21st to end	Night	13% 8% 3 6% 4 4 4 4 5% 6% 42%	2600
December	1st to 10th	Night	18% 9% 3 8% 4 4 4 3 5% 6% 35%	2542
	11th to 20th	Night	14% 9% 4 8% 4 4 3 3 5% 5% 42%	3042
	21st to end	Night	19% 9% 4 9% 5% 5% 4 3 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	44% 5% 7% 15% 21% 7%	2837
	11th to 20th	Day	41% 6% 8% 16% 20% 8%	2840
	21st to end	Day	47% 6% 6% 15% 20% 7%	3132
February	1st to 10th	Day	48% 5% 6% 17% 18% 5%	1900
	11th to 20th	Day	49% 4 7% 16% 18% 6%	1858
	21st to end	Day	50% 6% 8% 12% 18% 6%	1570
March	1st to 10th	Day	47% 6% 8% 16% 15% 9%	3248
	11th to 20th	Day	37% 6% 7% 18% 21% 11%	3480
	21st to end	Day	46% 5% 8% 19% 17% 4	3815
April	1st to 10th	Day	40% 7% 10% 20% 18% 4	2114
	11th to 20th	Day	41% 6% 9% 16% 22% 5%	2263
	21st to end	Day	38% 6% 11% 26% 16% 3	2470
May	1st to 10th	Day	46% 8% 12% 19% 13% 2	4120
	11th to 20th	Day	50% 10% 10% 19% 9% 1	4085
	21st to end	Day	39% 10% 14% 21% 15% 1	4489
June	1st to 10th	Day	48% 10% 16% 19% 5% 1	2470
	11th to 20th	Day	39% 12% 17% 20% 11% 1	2470
	21st to end	Day	42% 12% 16% 16% 12% 2	2470
July	1st to 10th	Day	44% 15% 19% 17% 4 1	4055
	11th to 20th	Day	46% 12% 20% 17% 4 1	4051
	21st to end	Day	65% 11% 11% 9% 4	4324
August	1st to 10th	Day	41% 11% 18% 24% 6%	4091
	11th to 20th	Day	37% 11% 22% 15% 13% 1	3965
	21st to end	Day	37% 9% 11% 28% 13% 1	4158
September	1st to 10th	Day	44% 10% 11% 16% 14% 3	2090
	11th to 20th	Day	47% 8% 12% 16% 16% 2	2090
	21st to end	Day	41% 6% 13% 15% 19% 6%	2090
October	1st to 10th	Day	26% 5% 7% 16% 36% 11%	3480
	11th to 20th	Day	22% 4 6% 17% 26% 25%	3213
	21st to end	Day	28% 4 8% 23% 24% 14%	3428
November	1st to 10th	Day	33% 5% 7% 15% 29% 11%	1791
	11th to 20th	Day	35% 4 6% 18% 27% 10%	1800
	21st to end	Day	40% 5% 7% 16% 26% 6%	1800
December	1st to 10th	Day	49% 5% 7% 16% 18% 5%	1755
	11th to 20th	Day	42% 5% 8% 13% 23% 8%	2150
	21st to end	Day	45% 7% 7% 20% 17% 3	3124
January	1st to 10th	Night	46% 5% 5% 13% 25% 7%	4109
	11th to 20th	Night	43% 5% 7% 14% 21% 10%	4120
	21st to end	Night	51% 6% 6% 11% 19% 8%	4521
February	1st to 10th	Night	44% 4 9% 18% 19% 6%	2280
	11th to 20th	Night	50% 5% 6% 16% 19% 5%	2219
	21st to end	Night	52% 5% 7% 14% 16% 6%	1884
March	1st to 10th	Night	51% 10% 7% 12% 14% 5%	3605
	11th to 20th	Night	34% 6% 9% 21% 21% 9%	3480
	21st to end	Night	45% 6% 8% 20% 16% 6%	3817
April	1st to 10th	Night	36% 6% 13% 20% 21% 4	2081
	11th to 20th	Night	38% 4 10% 21% 21% 7%	1865
	21st to end	Night	35% 7% 13% 27% 16% 2	1710
May	1st to 10th	Night	42% 11% 15% 21% 11% 1	2840
	11th to 20th	Night	46% 11% 13% 20% 10%	2813
	21st to end	Night	31% 12% 18% 26% 12% 1	3087
June	1st to 10th	Night	42% 12% 18% 20% 8% 1	1710
	11th to 20th	Night	30% 12% 22% 25% 10% 1	1710
	21st to end	Night	32% 13% 19% 20% 13% 3	1710
July	1st to 10th	Night	45% 12% 20% 18% 4	2795
	11th to 20th	Night	38% 14% 25% 18% 4 1	2786
	21st to end	Night	56% 13% 15% 11% 4 1	2988
August	1st to 10th	Night	38% 11% 26% 20% 5%	2814
	11th to 20th	Night	37% 12% 21% 16% 12% 1	2926
	21st to end	Night	30% 10% 17% 27% 15% 2	3476
September	1st to 10th	Night	39% 11% 16% 17% 15% 3	2079
	11th to 20th	Night	42% 10% 13% 19% 16% 1	2090
	21st to end	Night	36% 8% 12% 21% 17% 6%	2090
October	1st to 10th	Night	26% 4 10% 16% 36% 7%	3480
	11th to 20th	Night	22% 5% 7% 17% 28% 21%	3705
	21st to end	Night	27% 3 10% 21% 25% 14%	4120
November	1st to 10th	Night	35% 4 8% 19% 24% 10%	2506
	11th to 20th	Night	37% 5% 6% 17% 25% 10%	2600
	21st to end	Night	40% 5% 7% 20% 22% 6%	2600
December	1st to 10th	Night	49% 5% 8% 15% 16% 6%	2542
	11th to 20th	Night	40% 7% 8% 13% 25% 6%	3044
	21st to end	Night	50% 8% 10% 16% 14% 3	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	29% 27% 34% 9% 2	270
	11th to 20th	Day	36% 23% 25% 12% 4	270
	21st to end	Day	29% 31% 29% 8% 3	297
February	1st to 10th	Day	30% 26% 34% 9% 1	270
	11th to 20th	Day	40% 30% 24% 5% 1	270
	21st to end	Day	40% 25% 28% 6%	225
March	1st to 10th	Day	30% 16% 31% 17% 6%	346
	11th to 20th	Day	27% 21% 29% 18% 5% 1	460
	21st to end	Day	26% 22% 28% 19% 6% 1	506
April	1st to 10th	Day	24% 16% 28% 20% 10% 1	460
	11th to 20th	Day	17% 26% 24% 21% 11% 1	452
	21st to end	Day	20% 15% 24% 24% 13% 4	460
May	1st to 10th	Day	19% 19% 25% 19% 13% 5%	463
	11th to 20th	Day	17% 11% 21% 28% 12% 10%	487
	21st to end	Day	13% 9% 25% 23% 17% 13%	529
June	1st to 10th	Day	13% 6% 21% 27% 21% 11%	490
	11th to 20th	Day	8% 5% 23% 25% 24% 15%	490
	21st to end	Day	11% 5% 25% 25% 20% 15%	490
July	1st to 10th	Day	9% 4 14% 25% 29% 19%	485
	11th to 20th	Day	9% 4 12% 26% 26% 24%	484
	21st to end	Day	9% 4 13% 27% 27% 22%	532
August	1st to 10th	Day	14% 6% 17% 23% 20% 20%	486
	11th to 20th	Day	11% 6% 15% 23% 29% 16%	479
	21st to end	Day	12% 4 13% 23% 30% 18%	539
September	1st to 10th	Day	10% 6% 16% 25% 31% 12%	490
	11th to 20th	Day	18% 5% 16% 21% 31% 10%	490
	21st to end	Day	14% 7% 20% 26% 26% 7%	490
October	1st to 10th	Day	16% 6% 23% 29% 18% 8%	490
	11th to 20th	Day	17% 12% 25% 27% 17% 3	490
	21st to end	Day	18% 12% 28% 25% 15% 2	539
November	1st to 10th	Day	17% 18% 30% 23% 9% 2	329
	11th to 20th	Day	23% 22% 32% 17% 5%	300
	21st to end	Day	18% 24% 36% 15% 6% 1	300
December	1st to 10th	Day	32% 24% 27% 13% 3	285
	11th to 20th	Day	26% 20% 35% 13% 5% 1	270
	21st to end	Day	29% 24% 31% 12% 3 1	297
January	1st to 10th	Night	26% 19% 28% 21% 5% 1	760
	11th to 20th	Night	23% 22% 25% 23% 7%	760
	21st to end	Night	22% 21% 31% 23% 3	836
February	1st to 10th	Night	20% 19% 26% 29% 6%	760
	11th to 20th	Night	27% 21% 29% 21% 2	743
	21st to end	Night	28% 22% 29% 18% 3	628
March	1st to 10th	Night	21% 18% 32% 25% 4	760
	11th to 20th	Night	21% 19% 25% 26% 8% 1	760
	21st to end	Night	20% 17% 28% 25% 10%	836
April	1st to 10th	Night	17% 17% 28% 28% 9% 1	751
	11th to 20th	Night	17% 14% 22% 30% 15% 1	563
	21st to end	Night	12% 10% 24% 34% 17% 2	570
May	1st to 10th	Night	15% 9% 20% 33% 21% 2	570
	11th to 20th	Night	14% 7% 18% 32% 24% 4	561
	21st to end	Night	11% 4 12% 33% 32% 7%	617
June	1st to 10th	Night	10% 5% 12% 35% 33% 6%	570
	11th to 20th	Night	6% 2 14% 30% 34% 14%	570
	21st to end	Night	8% 2 11% 31% 38% 9%	570
July	1st to 10th	Night	9% 2 10% 24% 45% 10%	555
	11th to 20th	Night	9% 3 9% 21% 44% 14%	552
	21st to end	Night	9% 2 8% 22% 45% 14%	624
August	1st to 10th	Night	9% 4 7% 24% 43% 13%	567
	11th to 20th	Night	11% 2 12% 27% 40% 9%	564
	21st to end	Night	13% 2 9% 24% 40% 12%	627
September	1st to 10th	Night	11% 3 13% 28% 36% 9%	749
	11th to 20th	Night	16% 5% 14% 27% 34% 4	760
	21st to end	Night	14% 6% 13% 32% 31% 3	760
October	1st to 10th	Night	14% 7% 19% 30% 24% 7%	760
	11th to 20th	Night	16% 10% 21% 32% 21% 2	760
	21st to end	Night	15% 13% 17% 36% 16% 2	836
November	1st to 10th	Night	14% 10% 24% 30% 19% 3	780
	11th to 20th	Night	19% 16% 23% 28% 13% 2	800
	21st to end	Night	20% 17% 21% 29% 13% 1	800
December	1st to 10th	Night	25% 18% 23% 26% 7% 1	783
	11th to 20th	Night	21% 16% 25% 30% 7% 1	760
	21st to end	Night	27% 15% 25% 28% 5%	836

Page generated at 2024-12-03 06:45:13. Version ac07

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