Bear Branch Nature Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bear Branch Nature Center clear sky chart from 2005-11-06 to 2024-04-03.

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	14% 6% 3 5% 5% 3 5% 5% 6% 7% 40%	78861
	Night	15% 7% 3 5% 5% 3 5% 5% 5% 7% 41%	81257
Transparency	Day	42% 6% 12% 22% 15% 3	78571
	Night	41% 6% 11% 23% 16% 3	81066
Seeing	Day	19% 15% 28% 22% 12% 4	14077
	Night	17% 13% 31% 27% 11% 1	23674

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	16% 7% 3 5% 4 3 5% 4 5% 6% 43%	2517
	11th to 20th	Day	14% 11% 4 9% 8% 4 4 4 4 5% 34%	2822
	21st to end	Day	18% 10% 4 6% 7% 3 5% 4 5% 5% 33%	3124
February	1st to 10th	Day	14% 8% 3 6% 6% 4 5% 5% 5% 7% 37%	1710
	11th to 20th	Day	16% 7% 3 6% 6% 3 5% 4 5% 7% 39%	1715
	21st to end	Day	18% 9% 4 5% 5% 3 4 3 5% 5% 38%	1570
March	1st to 10th	Day	14% 6% 3 5% 4 3 3 4 5% 7% 45%	2028
	11th to 20th	Day	15% 7% 3 5% 6% 4 4 5% 6% 7% 39%	2090
	21st to end	Day	18% 7% 3 7% 6% 4 5% 3 5% 6% 37%	2346
April	1st to 10th	Day	14% 8% 4 5% 5% 3 5% 6% 6% 7% 38%	2184
	11th to 20th	Day	14% 5% 3 5% 5% 3 4 4 5% 7% 44%	2134
	21st to end	Day	19% 6% 3 5% 4 3 4 5% 6% 5% 40%	2160
May	1st to 10th	Day	16% 6% 3 6% 5% 3 4 5% 6% 9% 36%	2306
	11th to 20th	Day	19% 7% 3 6% 6% 3 5% 5% 5% 8% 35%	2455
	21st to end	Day	13% 6% 3 5% 6% 4 5% 4 7% 9% 39%	2725
June	1st to 10th	Day	13% 5% 2 4 5% 3 5% 5% 7% 10% 39%	2520
	11th to 20th	Day	12% 6% 3 5% 6% 4 5% 5% 6% 8% 39%	2520
	21st to end	Day	11% 4 2 3 5% 3 5% 5% 7% 10% 44%	2520
July	1st to 10th	Day	10% 5% 2 5% 6% 3 6% 6% 6% 9% 42%	2520
	11th to 20th	Day	7% 4 2 5% 5% 4 6% 7% 7% 11% 43%	2507
	21st to end	Day	10% 5% 4 6% 5% 4 6% 6% 7% 9% 37%	2547
August	1st to 10th	Day	10% 4 2 6% 7% 4 6% 7% 7% 9% 38%	2327
	11th to 20th	Day	10% 6% 3 6% 5% 4 6% 6% 7% 9% 39%	2214
	21st to end	Day	11% 5% 2 5% 6% 3 6% 5% 7% 8% 41%	2376
September	1st to 10th	Day	16% 6% 2 4 5% 4 4 5% 5% 7% 44%	2160
	11th to 20th	Day	13% 4 2 4 5% 3 4 4 6% 8% 48%	2160
	21st to end	Day	18% 7% 2 6% 5% 3 4 4 5% 7% 40%	1901
October	1st to 10th	Day	17% 5% 2 4 5% 3 3 5% 4 7% 44%	1800
	11th to 20th	Day	17% 7% 2 5% 5% 2 3 3 4 5% 46%	1800
	21st to end	Day	15% 7% 3 5% 4 2 4 4 5% 6% 45%	1980
November	1st to 10th	Day	12% 6% 3 4 4 2 4 3 6% 7% 50%	1724
	11th to 20th	Day	15% 5% 3 4 5% 2 4 5% 5% 6% 46%	1677
	21st to end	Day	16% 5% 3 5% 4 3 5% 4 5% 6% 43%	1520
December	1st to 10th	Day	17% 8% 3 5% 5% 3 5% 5% 5% 7% 36%	1520
	11th to 20th	Day	15% 8% 3 6% 6% 3 4 4 5% 8% 38%	1910
	21st to end	Day	17% 8% 3 6% 5% 3 5% 5% 7% 7% 34%	2772
January	1st to 10th	Night	14% 9% 4 7% 6% 4 4 4 5% 7% 38%	4429
	11th to 20th	Night	19% 7% 2 5% 5% 2 4 4 5% 6% 41%	4123
	21st to end	Night	20% 10% 3 5% 5% 3 4 3 4 6% 35%	4532
February	1st to 10th	Night	15% 8% 4 5% 5% 3 4 4 5% 8% 40%	2470
	11th to 20th	Night	17% 9% 3 5% 5% 3 4 3 5% 6% 40%	2351
	21st to end	Night	17% 9% 3 5% 5% 3 4 5% 5% 6% 38%	1884
March	1st to 10th	Night	15% 5% 2 4 5% 3 5% 5% 5% 6% 46%	2148
	11th to 20th	Night	16% 7% 3 5% 5% 4 4 4 4 6% 43%	2090
	21st to end	Night	14% 8% 3 6% 5% 3 5% 3 4 7% 41%	2250
April	1st to 10th	Night	16% 8% 3 6% 6% 3 4 5% 6% 7% 37%	1821
	11th to 20th	Night	13% 6% 2 5% 5% 3 5% 4 6% 8% 44%	1775
	21st to end	Night	17% 5% 3 5% 5% 3 4 5% 6% 7% 41%	1800
May	1st to 10th	Night	16% 6% 4 5% 5% 3 5% 4 6% 7% 38%	1669
	11th to 20th	Night	17% 7% 3 6% 4 3 5% 5% 6% 8% 37%	1434
	21st to end	Night	12% 7% 3 5% 5% 3 4 5% 6% 9% 41%	1550
June	1st to 10th	Night	11% 5% 3 4 4 2 5% 4 6% 8% 47%	1440
	11th to 20th	Night	10% 6% 3 5% 6% 4 5% 5% 7% 10% 39%	1440
	21st to end	Night	7% 5% 2 5% 5% 3 5% 6% 7% 10% 43%	1440
July	1st to 10th	Night	8% 5% 3 7% 6% 4 6% 6% 7% 10% 37%	1440
	11th to 20th	Night	6% 4 2 5% 4 4 5% 6% 7% 10% 47%	1449
	21st to end	Night	8% 5% 1 4 5% 3 5% 5% 7% 11% 45%	1771
August	1st to 10th	Night	10% 5% 2 4 5% 4 6% 6% 7% 9% 41%	1611
	11th to 20th	Night	9% 7% 3 7% 6% 4 5% 6% 6% 7% 42%	1669
	21st to end	Night	11% 5% 3 5% 5% 3 5% 6% 5% 9% 43%	1980
September	1st to 10th	Night	13% 5% 3 6% 5% 3 4 4 6% 7% 45%	1800
	11th to 20th	Night	11% 5% 3 4 4 3 4 3 4 7% 53%	1800
	21st to end	Night	17% 5% 2 5% 4 3 5% 4 5% 7% 43%	2054
October	1st to 10th	Night	18% 6% 3 4 4 3 4 3 5% 6% 43%	2160
	11th to 20th	Night	15% 6% 2 4 4 3 4 4 4 6% 49%	2160
	21st to end	Night	16% 6% 2 4 4 2 4 4 5% 6% 47%	2376
November	1st to 10th	Night	12% 5% 2 5% 4 2 4 3 5% 7% 52%	2353
	11th to 20th	Night	14% 7% 3 5% 5% 2 4 3 4 6% 47%	2499
	21st to end	Night	14% 4 3 4 5% 3 4 5% 6% 7% 45%	2660
December	1st to 10th	Night	17% 7% 3 6% 6% 3 5% 5% 5% 6% 37%	2660
	11th to 20th	Night	17% 6% 3 5% 5% 4 5% 5% 5% 6% 40%	3285
	21st to end	Night	16% 8% 2 5% 6% 4 6% 6% 7% 8% 32%	4884

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	42% 4 11% 28% 12% 4	2518
	11th to 20th	Day	51% 4 10% 19% 12% 3	2822
	21st to end	Day	51% 6% 10% 21% 9% 2	3124
February	1st to 10th	Day	46% 5% 13% 24% 10% 2	1710
	11th to 20th	Day	45% 5% 10% 24% 14% 3	1724
	21st to end	Day	49% 4 11% 20% 13% 4	1570
March	1st to 10th	Day	39% 4 13% 25% 17% 2	2028
	11th to 20th	Day	43% 5% 11% 19% 17% 5%	2090
	21st to end	Day	49% 5% 8% 18% 17% 3	2346
April	1st to 10th	Day	44% 5% 12% 19% 16% 4	2184
	11th to 20th	Day	40% 6% 11% 21% 18% 5%	2134
	21st to end	Day	44% 6% 10% 20% 18% 3	2160
May	1st to 10th	Day	44% 7% 12% 21% 15% 2	2306
	11th to 20th	Day	47% 7% 11% 18% 13% 3	2459
	21st to end	Day	41% 8% 13% 24% 12% 2	2725
June	1st to 10th	Day	38% 8% 14% 23% 14% 2	2520
	11th to 20th	Day	41% 9% 14% 21% 13% 2	2520
	21st to end	Day	34% 9% 14% 26% 16% 1	2520
July	1st to 10th	Day	37% 11% 12% 21% 16% 3	2450
	11th to 20th	Day	33% 9% 14% 26% 16% 3	2432
	21st to end	Day	41% 10% 11% 20% 16% 2	2405
August	1st to 10th	Day	39% 10% 13% 24% 13% 1	2314
	11th to 20th	Day	40% 7% 14% 22% 15% 2	2214
	21st to end	Day	38% 8% 13% 24% 14% 3	2376
September	1st to 10th	Day	41% 7% 11% 20% 18% 4	2160
	11th to 20th	Day	34% 6% 10% 26% 21% 4	2160
	21st to end	Day	45% 5% 8% 19% 20% 3	1901
October	1st to 10th	Day	41% 6% 10% 24% 17% 2	1800
	11th to 20th	Day	41% 4 11% 22% 21% 2	1800
	21st to end	Day	40% 6% 9% 25% 18% 2	1980
November	1st to 10th	Day	34% 5% 12% 25% 20% 4	1724
	11th to 20th	Day	36% 6% 11% 23% 21% 3	1677
	21st to end	Day	41% 5% 11% 29% 12% 2	1520
December	1st to 10th	Day	47% 6% 13% 23% 11% 1	1520
	11th to 20th	Day	44% 4 12% 29% 9% 1	1906
	21st to end	Day	47% 5% 18% 19% 11%	2772
January	1st to 10th	Night	44% 4 12% 25% 12% 3	4429
	11th to 20th	Night	43% 4 11% 26% 13% 2	4123
	21st to end	Night	49% 4 8% 27% 10% 2	4532
February	1st to 10th	Night	43% 5% 13% 24% 13% 2	2470
	11th to 20th	Night	46% 4 9% 21% 18% 4	2353
	21st to end	Night	45% 5% 11% 20% 14% 5%	1884
March	1st to 10th	Night	39% 5% 10% 26% 17% 2	2148
	11th to 20th	Night	41% 6% 10% 23% 17% 3	2090
	21st to end	Night	43% 4 10% 20% 18% 5%	2250
April	1st to 10th	Night	45% 5% 11% 18% 17% 4	1821
	11th to 20th	Night	38% 5% 11% 22% 19% 6%	1775
	21st to end	Night	41% 5% 11% 21% 16% 5%	1800
May	1st to 10th	Night	44% 6% 11% 21% 13% 4	1669
	11th to 20th	Night	44% 8% 11% 17% 17% 3	1435
	21st to end	Night	39% 9% 16% 22% 12% 2	1551
June	1st to 10th	Night	35% 8% 11% 26% 18% 2	1440
	11th to 20th	Night	38% 10% 13% 23% 15% 2	1440
	21st to end	Night	34% 9% 12% 26% 18% 2	1440
July	1st to 10th	Night	40% 11% 15% 20% 12% 3	1400
	11th to 20th	Night	30% 11% 14% 26% 16% 3	1401
	21st to end	Night	32% 8% 18% 23% 18% 1	1672
August	1st to 10th	Night	36% 10% 16% 23% 13% 1	1600
	11th to 20th	Night	40% 10% 12% 22% 15% 2	1669
	21st to end	Night	36% 8% 12% 24% 16% 3	1980
September	1st to 10th	Night	38% 6% 11% 20% 19% 5%	1800
	11th to 20th	Night	33% 5% 10% 25% 24% 3	1800
	21st to end	Night	42% 7% 9% 20% 20% 3	2054
October	1st to 10th	Night	43% 6% 10% 22% 17% 2	2160
	11th to 20th	Night	37% 5% 10% 28% 19% 2	2160
	21st to end	Night	37% 6% 9% 27% 19% 2	2376
November	1st to 10th	Night	33% 4 11% 26% 21% 5%	2353
	11th to 20th	Night	39% 4 9% 24% 20% 4	2499
	21st to end	Night	37% 5% 12% 26% 18% 2	2660
December	1st to 10th	Night	47% 5% 12% 24% 13% 1	2660
	11th to 20th	Night	42% 4 12% 22% 16% 3	3288
	21st to end	Night	46% 7% 15% 21% 11% 1	4884

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	26% 28% 32% 12% 3 1	180
	11th to 20th	Day	27% 29% 31% 12% 1	267
	21st to end	Day	22% 33% 29% 12% 4	297
February	1st to 10th	Day	23% 27% 36% 11% 2	270
	11th to 20th	Day	34% 27% 33% 6% 1	322
	21st to end	Day	31% 24% 30% 13% 2	382
March	1st to 10th	Day	23% 27% 30% 18% 3	460
	11th to 20th	Day	25% 24% 31% 15% 3 2	460
	21st to end	Day	24% 24% 31% 15% 5% 1	506
April	1st to 10th	Day	24% 21% 34% 14% 6% 1	428
	11th to 20th	Day	17% 22% 30% 17% 12% 3	412
	21st to end	Day	25% 15% 35% 16% 7% 1	420
May	1st to 10th	Day	24% 17% 31% 17% 10% 2	423
	11th to 20th	Day	22% 16% 29% 21% 9% 2	447
	21st to end	Day	15% 6% 25% 28% 21% 5%	485
June	1st to 10th	Day	14% 11% 30% 24% 16% 5%	450
	11th to 20th	Day	17% 9% 30% 26% 13% 4	450
	21st to end	Day	12% 8% 26% 34% 16% 4	450
July	1st to 10th	Day	12% 5% 21% 29% 21% 12%	445
	11th to 20th	Day	5% 2 23% 36% 26% 9%	444
	21st to end	Day	12% 5% 22% 34% 22% 5%	488
August	1st to 10th	Day	12% 5% 20% 30% 25% 8%	446
	11th to 20th	Day	11% 3 22% 31% 23% 9%	439
	21st to end	Day	11% 4 21% 32% 21% 12%	495
September	1st to 10th	Day	18% 8% 18% 22% 22% 12%	450
	11th to 20th	Day	11% 5% 23% 28% 22% 10%	450
	21st to end	Day	21% 13% 24% 25% 13% 4	450
October	1st to 10th	Day	21% 10% 23% 24% 16% 6%	450
	11th to 20th	Day	18% 15% 28% 24% 12% 2	450
	21st to end	Day	18% 15% 37% 20% 7% 2	495
November	1st to 10th	Day	18% 13% 31% 24% 12% 2	391
	11th to 20th	Day	19% 20% 33% 18% 9% 1	337
	21st to end	Day	20% 22% 34% 18% 6%	180
December	1st to 10th	Day	25% 23% 34% 13% 4 1	180
	11th to 20th	Day	25% 27% 28% 16% 4	180
	21st to end	Day	19% 23% 34% 18% 7%	198
January	1st to 10th	Night	18% 22% 41% 17% 2	760
	11th to 20th	Night	23% 19% 33% 22% 3	760
	21st to end	Night	18% 20% 42% 19% 1	836
February	1st to 10th	Night	19% 20% 36% 24% 2	760
	11th to 20th	Night	25% 25% 35% 14% 1	743
	21st to end	Night	25% 20% 38% 14% 3	628
March	1st to 10th	Night	20% 19% 40% 18% 3	760
	11th to 20th	Night	21% 21% 34% 19% 5%	760
	21st to end	Night	19% 15% 43% 18% 4	836
April	1st to 10th	Night	21% 21% 35% 18% 4	729
	11th to 20th	Night	16% 14% 37% 24% 8% 1	711
	21st to end	Night	21% 14% 33% 24% 7% 1	720
May	1st to 10th	Night	17% 10% 34% 29% 10%	589
	11th to 20th	Night	20% 8% 31% 32% 8% 1	373
	21st to end	Night	15% 6% 25% 35% 18% 1	389
June	1st to 10th	Night	12% 3 31% 33% 21%	360
	11th to 20th	Night	13% 4 28% 36% 17% 1	360
	21st to end	Night	9% 4 26% 46% 16%	360
July	1st to 10th	Night	8% 3 20% 39% 26% 4	350
	11th to 20th	Night	8% 1 19% 40% 29% 3	357
	21st to end	Night	9% 2 19% 41% 27% 3	591
August	1st to 10th	Night	12% 2 13% 48% 24% 2	537
	11th to 20th	Night	12% 4 17% 39% 26% 2	605
	21st to end	Night	12% 3 18% 37% 26% 4	792
September	1st to 10th	Night	15% 3 21% 34% 25% 3	720
	11th to 20th	Night	11% 4 19% 35% 27% 4	720
	21st to end	Night	20% 5% 23% 32% 18% 2	720
October	1st to 10th	Night	22% 6% 22% 29% 17% 4	720
	11th to 20th	Night	17% 11% 30% 30% 12% 1	720
	21st to end	Night	19% 12% 34% 24% 11%	792
November	1st to 10th	Night	14% 11% 34% 30% 9% 1	740
	11th to 20th	Night	18% 18% 31% 25% 7% 1	760
	21st to end	Night	15% 17% 37% 24% 7% 1	760
December	1st to 10th	Night	23% 14% 38% 18% 7%	760
	11th to 20th	Night	18% 15% 41% 21% 5%	760
	21st to end	Night	20% 17% 36% 25% 2	836

Page generated at 2024-03-31 06:08:54. Version ac07

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