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 2024-11-04.

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	15% 7% 2 6% 5% 4 4 4 6% 7% 40%	101270
	Night	15% 7% 2 6% 4 4 4 4 5% 7% 41%	97678
Transparency	Day	41% 6% 12% 23% 15% 3	104908
	Night	40% 6% 11% 24% 16% 3	102179
Seeing	Day	19% 15% 28% 22% 13% 4	14936
	Night	17% 13% 31% 27% 11% 1	24361

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 6% 3 4 5% 3 5% 5% 43%	2517
	11th to 20th	Day	14% 11% 4 11% 6% 5% 4 3 4 5% 34%	2822
	21st to end	Day	18% 11% 3 8% 5% 5% 4 3 5% 5% 33%	3124
February	1st to 10th	Day	14% 9% 2 6% 5% 5% 5% 4 5% 6% 37%	1710
	11th to 20th	Day	16% 8% 2 7% 6% 4 4 3 5% 7% 39%	1715
	21st to end	Day	18% 10% 3 6% 5% 4 3 2 5% 5% 38%	1570
March	1st to 10th	Day	22% 8% 2 6% 4 4 4 4 5% 7% 35%	3338
	11th to 20th	Day	10% 7% 3 6% 5% 5% 4 5% 6% 6% 44%	3480
	21st to end	Day	20% 8% 2 6% 5% 4 3 3 4 6% 40%	3900
April	1st to 10th	Day	13% 9% 3 6% 4 4 6% 4 6% 7% 37%	2280
	11th to 20th	Day	14% 6% 2 6% 5% 4 4 3 5% 7% 44%	2254
	21st to end	Day	18% 7% 3 6% 3 5% 3 4 6% 5% 41%	2280
May	1st to 10th	Day	26% 7% 2 6% 4 4 4 4 5% 8% 30%	4035
	11th to 20th	Day	23% 7% 3 8% 5% 4 5% 4 6% 7% 28%	4361
	21st to end	Day	10% 5% 2 5% 4 5% 5% 4 7% 9% 44%	4823
June	1st to 10th	Day	13% 6% 2 5% 5% 4 5% 4 7% 11% 39%	2660
	11th to 20th	Day	12% 6% 2 5% 5% 5% 5% 4 7% 8% 40%	2660
	21st to end	Day	10% 4 2 4 5% 5% 5% 4 7% 10% 44%	2660
July	1st to 10th	Day	6% 4 2 7% 5% 6% 6% 6% 8% 10% 41%	4440
	11th to 20th	Day	9% 5% 2 6% 5% 5% 5% 5% 8% 11% 39%	4413
	21st to end	Day	11% 8% 3 8% 5% 5% 5% 5% 7% 8% 36%	4466
August	1st to 10th	Day	17% 6% 2 7% 5% 4 6% 5% 6% 9% 34%	4104
	11th to 20th	Day	11% 5% 2 7% 4 5% 6% 4 7% 9% 40%	3871
	21st to end	Day	11% 6% 2 5% 4 4 4 4 6% 7% 47%	4180
September	1st to 10th	Day	15% 6% 2 5% 4 4 4 4 4 7% 45%	2280
	11th to 20th	Day	12% 5% 2 5% 4 4 4 3 6% 8% 48%	2280
	21st to end	Day	20% 8% 2 6% 4 4 4 3 5% 7% 38%	2005
October	1st to 10th	Day	17% 5% 2 4 5% 3 4 4 4 7% 45%	1900
	11th to 20th	Day	16% 7% 2 6% 3 3 3 3 4 5% 48%	1900
	21st to end	Day	14% 7% 3 5% 3 3 4 3 6% 6% 46%	2090
November	1st to 10th	Day	12% 6% 2 4 3 3 3 3 6% 7% 50%	1753
	11th to 20th	Day	15% 6% 2 4 5% 3 4 4 5% 6% 46%	1677
	21st to end	Day	16% 6% 3 6% 4 4 5% 3 5% 6% 43%	1520
December	1st to 10th	Day	17% 8% 3 6% 4 5% 4 4 5% 7% 36%	1520
	11th to 20th	Day	15% 8% 3 7% 5% 4 4 3 5% 8% 38%	1910
	21st to end	Day	17% 9% 3 6% 5% 4 5% 4 7% 7% 34%	2772
January	1st to 10th	Night	14% 9% 3 8% 5% 5% 4 3 5% 7% 37%	4429
	11th to 20th	Night	18% 8% 2 6% 4 3 4 3 5% 6% 41%	4123
	21st to end	Night	20% 11% 3 5% 5% 4 4 3 4 6% 35%	4532
February	1st to 10th	Night	15% 9% 3 5% 4 4 4 3 6% 7% 39%	2470
	11th to 20th	Night	17% 9% 3 6% 4 4 4 3 5% 5% 40%	2351
	21st to end	Night	17% 10% 3 6% 4 4 4 4 5% 6% 38%	1884
March	1st to 10th	Night	21% 8% 2 6% 4 4 4 3 5% 5% 38%	3511
	11th to 20th	Night	11% 6% 2 6% 5% 5% 4 3 5% 6% 48%	3480
	21st to end	Night	13% 10% 3 7% 4 3 3 2 3 5% 46%	3730
April	1st to 10th	Night	15% 9% 3 6% 6% 4 4 4 6% 7% 37%	1900
	11th to 20th	Night	13% 6% 2 6% 4 4 4 4 5% 8% 44%	1875
	21st to end	Night	16% 6% 3 5% 4 4 4 4 7% 7% 41%	1900
May	1st to 10th	Night	25% 8% 3 6% 4 4 4 3 6% 8% 30%	2889
	11th to 20th	Night	22% 8% 3 8% 5% 4 4 3 5% 7% 29%	2528
	21st to end	Night	11% 6% 2 6% 4 4 4 5% 7% 9% 41%	2732
June	1st to 10th	Night	11% 5% 2 5% 4 3 5% 4 6% 8% 46%	1520
	11th to 20th	Night	10% 6% 2 6% 5% 4 5% 5% 6% 11% 40%	1520
	21st to end	Night	7% 6% 2 6% 4 5% 5% 4 7% 10% 43%	1520
July	1st to 10th	Night	6% 5% 2 8% 5% 6% 6% 5% 7% 11% 40%	2520
	11th to 20th	Night	7% 6% 2 7% 5% 5% 5% 5% 8% 10% 39%	2543
	21st to end	Night	12% 8% 2 7% 4 4 5% 4 6% 8% 40%	3087
August	1st to 10th	Night	18% 7% 2 6% 4 5% 5% 4 7% 9% 33%	2825
	11th to 20th	Night	9% 8% 3 8% 5% 5% 4 5% 6% 7% 40%	2912
	21st to end	Night	10% 6% 2 6% 4 4 4 4 6% 8% 47%	3476
September	1st to 10th	Night	12% 6% 3 6% 4 4 4 4 6% 6% 46%	1900
	11th to 20th	Night	11% 5% 2 5% 3 4 4 3 4 7% 53%	1900
	21st to end	Night	19% 6% 2 5% 4 4 4 3 4 6% 41%	2169
October	1st to 10th	Night	18% 7% 3 5% 3 4 4 3 5% 6% 44%	2280
	11th to 20th	Night	14% 6% 2 4 3 3 4 3 4 6% 50%	2280
	21st to end	Night	15% 6% 2 5% 3 3 4 3 5% 6% 48%	2508
November	1st to 10th	Night	12% 5% 2 5% 4 3 3 3 5% 7% 52%	2396
	11th to 20th	Night	13% 8% 2 6% 4 3 3 3 5% 6% 47%	2499
	21st to end	Night	14% 5% 2 5% 5% 4 4 4 6% 6% 45%	2660
December	1st to 10th	Night	17% 8% 3 7% 5% 4 5% 4 6% 6% 37%	2660
	11th to 20th	Night	17% 6% 2 6% 5% 5% 5% 4 5% 6% 39%	3285
	21st to end	Night	16% 8% 2 7% 5% 5% 5% 5% 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	46% 4 11% 24% 11% 3	3338
	11th to 20th	Day	36% 5% 10% 27% 18% 4	3480
	21st to end	Day	46% 4 9% 20% 17% 3	3900
April	1st to 10th	Day	44% 5% 12% 19% 16% 4	2280
	11th to 20th	Day	40% 6% 11% 21% 18% 5%	2254
	21st to end	Day	44% 6% 10% 20% 18% 3	2280
May	1st to 10th	Day	52% 7% 9% 20% 10% 1	4072
	11th to 20th	Day	52% 8% 13% 17% 8% 1	4365
	21st to end	Day	34% 8% 13% 26% 17% 2	4837
June	1st to 10th	Day	38% 8% 14% 24% 15% 2	2660
	11th to 20th	Day	39% 8% 14% 23% 13% 2	2660
	21st to end	Day	34% 9% 14% 26% 17% 1	2660
July	1st to 10th	Day	35% 10% 15% 21% 14% 4	4370
	11th to 20th	Day	36% 8% 15% 27% 12% 2	4338
	21st to end	Day	44% 8% 11% 19% 18% 1	4324
August	1st to 10th	Day	45% 8% 13% 25% 8%	4091
	11th to 20th	Day	38% 6% 12% 28% 15% 1	3910
	21st to end	Day	35% 6% 12% 27% 18% 2	4180
September	1st to 10th	Day	40% 6% 10% 20% 20% 4	2280
	11th to 20th	Day	34% 5% 9% 26% 22% 3	2280
	21st to end	Day	47% 5% 8% 19% 19% 2	2005
October	1st to 10th	Day	38% 4 7% 20% 27% 5%	3160
	11th to 20th	Day	29% 3 10% 27% 21% 10%	3140
	21st to end	Day	26% 4 10% 29% 29% 3	3428
November	1st to 10th	Day	34% 5% 12% 26% 20% 4	1753
	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	48% 6% 9% 25% 11% 1	3511
	11th to 20th	Night	35% 5% 10% 33% 15% 2	3480
	21st to end	Night	41% 4 8% 21% 21% 5%	3730
April	1st to 10th	Night	45% 5% 11% 19% 17% 4	1900
	11th to 20th	Night	38% 5% 11% 22% 18% 5%	1875
	21st to end	Night	40% 5% 11% 22% 17% 4	1900
May	1st to 10th	Night	52% 6% 9% 18% 12% 3	2917
	11th to 20th	Night	53% 9% 11% 15% 10% 1	2529
	21st to end	Night	36% 10% 15% 25% 11% 3	2739
June	1st to 10th	Night	35% 8% 10% 26% 18% 2	1520
	11th to 20th	Night	36% 10% 12% 24% 16% 1	1520
	21st to end	Night	34% 8% 12% 25% 18% 2	1520
July	1st to 10th	Night	37% 10% 18% 18% 12% 5%	2480
	11th to 20th	Night	37% 10% 14% 25% 12% 2	2495
	21st to end	Night	41% 7% 14% 20% 18% 1	2988
August	1st to 10th	Night	45% 8% 18% 21% 8% 1	2814
	11th to 20th	Night	40% 8% 10% 28% 13% 1	2939
	21st to end	Night	34% 6% 11% 30% 17% 2	3476
September	1st to 10th	Night	37% 6% 11% 20% 21% 5%	1900
	11th to 20th	Night	33% 5% 9% 26% 24% 3	1900
	21st to end	Night	44% 7% 9% 19% 19% 3	2169
October	1st to 10th	Night	42% 5% 10% 19% 21% 3	3800
	11th to 20th	Night	25% 4 10% 26% 27% 7%	3779
	21st to end	Night	25% 4 10% 32% 24% 5%	4120
November	1st to 10th	Night	33% 4 10% 26% 22% 5%	2396
	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	23% 22% 34% 14% 6% 1	460
	11th to 20th	Day	18% 22% 30% 17% 11% 2	452
	21st to end	Day	25% 15% 34% 17% 8% 1	460
May	1st to 10th	Day	25% 16% 30% 17% 10% 2	463
	11th to 20th	Day	22% 16% 29% 21% 10% 2	487
	21st to end	Day	15% 6% 26% 28% 21% 5%	529
June	1st to 10th	Day	15% 11% 31% 23% 16% 5%	490
	11th to 20th	Day	16% 9% 30% 28% 14% 4	490
	21st to end	Day	12% 8% 28% 33% 15% 4	490
July	1st to 10th	Day	11% 5% 22% 31% 20% 11%	485
	11th to 20th	Day	5% 2 24% 35% 25% 8%	484
	21st to end	Day	12% 5% 22% 35% 20% 5%	532
August	1st to 10th	Day	13% 5% 20% 30% 24% 8%	486
	11th to 20th	Day	11% 4 24% 31% 22% 8%	479
	21st to end	Day	11% 4 20% 32% 21% 12%	539
September	1st to 10th	Day	17% 9% 18% 23% 22% 11%	490
	11th to 20th	Day	11% 5% 23% 30% 22% 9%	490
	21st to end	Day	26% 12% 23% 23% 12% 4	490
October	1st to 10th	Day	20% 10% 24% 24% 16% 6%	490
	11th to 20th	Day	18% 16% 27% 25% 12% 2	490
	21st to end	Day	17% 14% 36% 21% 9% 2	539
November	1st to 10th	Day	18% 13% 32% 23% 12% 2	402
	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% 16% 42% 18% 4	836
April	1st to 10th	Night	21% 21% 36% 18% 4	760
	11th to 20th	Night	16% 15% 37% 24% 8% 1	751
	21st to end	Night	20% 15% 33% 24% 7% 1	760
May	1st to 10th	Night	18% 10% 34% 28% 10%	621
	11th to 20th	Night	19% 8% 31% 32% 8% 1	394
	21st to end	Night	14% 6% 25% 36% 18% 1	411
June	1st to 10th	Night	11% 3 31% 33% 21%	380
	11th to 20th	Night	13% 4 28% 38% 16% 1	380
	21st to end	Night	9% 5% 26% 45% 16%	380
July	1st to 10th	Night	8% 3 21% 39% 25% 4	370
	11th to 20th	Night	8% 2 19% 40% 28% 3	378
	21st to end	Night	10% 2 19% 40% 26% 3	624
August	1st to 10th	Night	12% 2 12% 47% 24% 2	567
	11th to 20th	Night	12% 4 18% 40% 24% 2	639
	21st to end	Night	12% 4 18% 38% 25% 4	836
September	1st to 10th	Night	15% 3 22% 34% 24% 3	760
	11th to 20th	Night	11% 4 18% 36% 26% 4	760
	21st to end	Night	23% 5% 23% 30% 17% 2	760
October	1st to 10th	Night	22% 6% 22% 29% 17% 3	760
	11th to 20th	Night	16% 11% 29% 30% 12% 1	760
	21st to end	Night	18% 11% 34% 25% 12%	836
November	1st to 10th	Night	14% 11% 35% 30% 9% 1	755
	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 2024-11-01 22:47:50. Version ac07

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