Bonebrake Center of Nature and History
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bonebrake Center of Nature and History clear sky chart from 2005-11-06 to 2024-01-15.

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	12% 7% 3 6% 5% 3 5% 4 5% 7% 42%	74714
	Night	12% 8% 3 5% 5% 3 4 4 5% 7% 45%	75073
Transparency	Day	41% 5% 11% 24% 16% 3	74427
	Night	39% 5% 11% 25% 18% 3	74880
Seeing	Day	18% 13% 28% 25% 14% 3	14408
	Night	18% 13% 32% 25% 11% 1	24352

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	12% 9% 3 7% 7% 2 4 4 4 5% 44%	1583
	11th to 20th	Day	15% 11% 4 7% 5% 3 4 4 4 6% 37%	1656
	21st to end	Day	13% 10% 4 6% 5% 3 3 3 5% 5% 44%	1782
February	1st to 10th	Day	15% 10% 4 7% 6% 3 5% 3 4 6% 36%	1620
	11th to 20th	Day	14% 9% 4 6% 4 3 5% 4 5% 7% 38%	1688
	21st to end	Day	15% 12% 3 6% 5% 4 5% 4 5% 6% 37%	1480
March	1st to 10th	Day	14% 9% 4 6% 5% 3 4 3 4 5% 44%	1912
	11th to 20th	Day	20% 10% 3 6% 5% 2 4 4 4 6% 35%	1980
	21st to end	Day	18% 12% 4 7% 6% 4 6% 4 4 6% 29%	2236
April	1st to 10th	Day	11% 6% 3 5% 5% 2 4 4 6% 8% 46%	2160
	11th to 20th	Day	17% 8% 3 6% 6% 3 3 4 5% 6% 39%	2134
	21st to end	Day	20% 8% 3 6% 5% 2 4 4 5% 6% 36%	2160
May	1st to 10th	Day	18% 7% 3 6% 5% 4 5% 5% 5% 7% 35%	2175
	11th to 20th	Day	16% 6% 2 5% 5% 3 4 4 5% 8% 41%	2402
	21st to end	Day	10% 7% 4 7% 7% 4 7% 6% 6% 9% 34%	2725
June	1st to 10th	Day	9% 5% 2 6% 5% 4 6% 5% 5% 9% 44%	2520
	11th to 20th	Day	6% 4 2 4 5% 3 5% 6% 6% 10% 48%	2520
	21st to end	Day	5% 3 2 4 4 4 5% 5% 7% 10% 51%	2520
July	1st to 10th	Day	10% 5% 2 6% 5% 2 6% 6% 7% 10% 41%	2520
	11th to 20th	Day	4 3 2 5% 5% 3 5% 5% 8% 11% 48%	2422
	21st to end	Day	9% 4 3 5% 5% 4 6% 6% 7% 9% 42%	2546
August	1st to 10th	Day	8% 5% 2 5% 6% 4 6% 6% 8% 10% 41%	2328
	11th to 20th	Day	10% 5% 3 5% 6% 4 6% 4 7% 10% 39%	2155
	21st to end	Day	9% 5% 2 4 4 3 5% 5% 5% 9% 47%	2376
September	1st to 10th	Day	13% 5% 2 4 4 3 4 4 5% 9% 48%	2160
	11th to 20th	Day	10% 4 2 5% 5% 3 4 4 6% 7% 48%	2160
	21st to end	Day	9% 4 2 5% 5% 3 4 4 4 7% 53%	1918
October	1st to 10th	Day	10% 4 2 5% 3 3 3 4 5% 7% 54%	1800
	11th to 20th	Day	15% 7% 2 5% 3 2 2 2 4 5% 53%	1800
	21st to end	Day	18% 7% 2 5% 3 2 3 3 4 5% 46%	1980
November	1st to 10th	Day	12% 5% 2 4 4 2 3 4 4 5% 54%	1759
	11th to 20th	Day	13% 7% 4 5% 4 2 4 3 3 7% 48%	1710
	21st to end	Day	15% 9% 4 6% 4 2 4 3 3 5% 45%	1606
December	1st to 10th	Day	13% 11% 4 5% 5% 3 3 4 5% 6% 41%	1520
	11th to 20th	Day	13% 10% 6% 8% 6% 3 4 4 3 5% 39%	1918
	21st to end	Day	14% 17% 5% 8% 5% 3 4 4 4 6% 31%	2783
January	1st to 10th	Night	11% 9% 5% 6% 5% 4 4 4 4 6% 42%	2577
	11th to 20th	Night	14% 9% 5% 6% 6% 3 5% 3 4 6% 39%	2393
	21st to end	Night	13% 9% 4 7% 5% 3 4 4 5% 6% 39%	2574
February	1st to 10th	Night	15% 10% 4 7% 5% 3 3 4 4 6% 38%	2340
	11th to 20th	Night	15% 8% 4 6% 4 3 4 3 4 6% 43%	2157
	21st to end	Night	16% 9% 4 7% 5% 3 4 3 4 5% 39%	1776
March	1st to 10th	Night	15% 9% 4 6% 4 2 3 4 5% 5% 43%	2062
	11th to 20th	Night	18% 10% 4 6% 5% 2 4 4 4 5% 38%	1980
	21st to end	Night	19% 11% 4 6% 6% 2 5% 5% 5% 5% 32%	2119
April	1st to 10th	Night	9% 5% 3 4 5% 2 3 4 6% 9% 50%	1800
	11th to 20th	Night	14% 9% 2 5% 5% 3 3 4 4 6% 45%	1775
	21st to end	Night	19% 7% 3 6% 5% 3 4 3 5% 7% 40%	1800
May	1st to 10th	Night	15% 7% 2 4 4 3 4 4 5% 7% 46%	1782
	11th to 20th	Night	14% 7% 3 5% 4 3 3 3 4 8% 46%	1488
	21st to end	Night	9% 6% 4 8% 7% 4 5% 4 7% 9% 38%	1551
June	1st to 10th	Night	8% 4 1 5% 5% 3 5% 4 6% 9% 51%	1440
	11th to 20th	Night	5% 3 2 3 4 2 3 4 7% 11% 56%	1440
	21st to end	Night	3 3 1 2 3 2 5% 4 6% 11% 60%	1440
July	1st to 10th	Night	8% 4 2 4 4 2 6% 5% 6% 9% 51%	1440
	11th to 20th	Night	4 3 1 3 4 2 3 5% 7% 9% 58%	1534
	21st to end	Night	6% 3 1 5% 5% 3 4 5% 7% 8% 52%	1772
August	1st to 10th	Night	5% 3 1 5% 5% 3 4 5% 7% 10% 50%	1611
	11th to 20th	Night	7% 3 2 4 5% 2 4 5% 6% 9% 54%	1746
	21st to end	Night	7% 4 2 4 4 2 3 4 4 8% 57%	1980
September	1st to 10th	Night	12% 5% 2 3 4 2 4 3 5% 5% 54%	1800
	11th to 20th	Night	9% 5% 2 4 4 2 4 5% 5% 8% 52%	1800
	21st to end	Night	9% 4 2 3 4 2 4 4 5% 7% 56%	2019
October	1st to 10th	Night	7% 4 1 4 4 2 3 4 4 7% 61%	2160
	11th to 20th	Night	15% 6% 2 4 4 2 4 3 3 5% 53%	2160
	21st to end	Night	19% 7% 2 4 4 3 3 3 4 4 48%	2376
November	1st to 10th	Night	11% 5% 2 4 4 2 3 4 4 5% 57%	2319
	11th to 20th	Night	13% 6% 3 5% 4 2 4 3 4 6% 49%	2470
	21st to end	Night	16% 10% 4 5% 4 2 3 3 4 5% 45%	2569
December	1st to 10th	Night	16% 9% 3 6% 5% 3 3 4 6% 7% 38%	2660
	11th to 20th	Night	14% 11% 5% 7% 5% 3 4 3 3 5% 40%	3279
	21st to end	Night	14% 17% 8% 8% 6% 3 4 4 4 5% 26%	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	44% 3 9% 25% 16% 3	1584
	11th to 20th	Day	48% 4 10% 24% 12% 1	1656
	21st to end	Day	44% 3 12% 25% 13% 3	1782
February	1st to 10th	Day	51% 4 10% 22% 13% 1	1620
	11th to 20th	Day	46% 5% 12% 21% 13% 4	1697
	21st to end	Day	49% 3 7% 24% 12% 6%	1480
March	1st to 10th	Day	44% 4 8% 22% 18% 5%	1912
	11th to 20th	Day	51% 5% 8% 18% 14% 3	1980
	21st to end	Day	57% 5% 10% 18% 9% 1	2236
April	1st to 10th	Day	37% 4 13% 25% 20% 1	2160
	11th to 20th	Day	47% 5% 10% 20% 16% 3	2134
	21st to end	Day	49% 5% 11% 21% 14% 1	2160
May	1st to 10th	Day	47% 7% 13% 22% 11% 1	2175
	11th to 20th	Day	42% 6% 12% 23% 15% 2	2406
	21st to end	Day	45% 8% 13% 21% 12% 1	2725
June	1st to 10th	Day	37% 6% 14% 26% 15% 2	2520
	11th to 20th	Day	29% 6% 13% 29% 18% 3	2520
	21st to end	Day	27% 6% 19% 28% 16% 5%	2520
July	1st to 10th	Day	36% 7% 16% 25% 12% 3	2451
	11th to 20th	Day	28% 7% 15% 28% 19% 4	2348
	21st to end	Day	36% 8% 14% 30% 10% 1	2405
August	1st to 10th	Day	35% 8% 15% 27% 15%	2314
	11th to 20th	Day	38% 7% 13% 27% 13% 2	2155
	21st to end	Day	33% 6% 14% 24% 16% 6%	2376
September	1st to 10th	Day	34% 5% 13% 29% 15% 5%	2160
	11th to 20th	Day	34% 5% 8% 26% 25% 2	2160
	21st to end	Day	32% 5% 8% 28% 25% 3	1918
October	1st to 10th	Day	31% 4 11% 25% 26% 3	1800
	11th to 20th	Day	36% 2 7% 26% 23% 6%	1800
	21st to end	Day	42% 3 7% 25% 18% 5%	1980
November	1st to 10th	Day	34% 4 10% 24% 22% 7%	1759
	11th to 20th	Day	38% 4 7% 23% 22% 6%	1710
	21st to end	Day	44% 3 8% 26% 18% 2	1606
December	1st to 10th	Day	44% 4 9% 27% 14% 2	1520
	11th to 20th	Day	50% 4 5% 17% 22% 1	1915
	21st to end	Day	56% 5% 8% 16% 13% 2	2783
January	1st to 10th	Night	44% 4 9% 21% 19% 2	2577
	11th to 20th	Night	48% 4 9% 23% 15% 1	2393
	21st to end	Night	46% 4 11% 23% 15% 2	2574
February	1st to 10th	Night	48% 4 10% 22% 14% 2	2340
	11th to 20th	Night	43% 3 11% 22% 17% 3	2158
	21st to end	Night	48% 4 7% 22% 15% 4	1776
March	1st to 10th	Night	43% 4 8% 21% 18% 6%	2062
	11th to 20th	Night	49% 5% 8% 21% 14% 3	1980
	21st to end	Night	53% 5% 11% 20% 10% 1	2119
April	1st to 10th	Night	31% 3 14% 29% 20% 3	1800
	11th to 20th	Night	40% 4 11% 25% 14% 5%	1775
	21st to end	Night	46% 4 8% 26% 16% 1	1800
May	1st to 10th	Night	38% 6% 14% 23% 18% 1	1782
	11th to 20th	Night	39% 5% 15% 21% 18% 2	1489
	21st to end	Night	43% 7% 14% 20% 13% 3	1552
June	1st to 10th	Night	30% 6% 17% 26% 19% 1	1440
	11th to 20th	Night	22% 7% 13% 34% 20% 5%	1440
	21st to end	Night	19% 6% 18% 31% 19% 7%	1440
July	1st to 10th	Night	31% 7% 17% 25% 16% 4	1400
	11th to 20th	Night	22% 6% 16% 30% 21% 4	1485
	21st to end	Night	27% 8% 14% 36% 16% 1	1673
August	1st to 10th	Night	27% 8% 16% 34% 14% 2	1601
	11th to 20th	Night	26% 6% 16% 31% 18% 2	1746
	21st to end	Night	26% 5% 16% 27% 21% 6%	1980
September	1st to 10th	Night	31% 4 10% 29% 21% 5%	1800
	11th to 20th	Night	30% 5% 10% 27% 26% 2	1800
	21st to end	Night	28% 4 9% 26% 29% 3	2019
October	1st to 10th	Night	24% 4 11% 29% 26% 5%	2160
	11th to 20th	Night	36% 3 6% 26% 24% 5%	2160
	21st to end	Night	41% 3 7% 22% 22% 5%	2376
November	1st to 10th	Night	30% 4 10% 28% 22% 6%	2319
	11th to 20th	Night	37% 3 7% 24% 23% 7%	2470
	21st to end	Night	43% 3 7% 24% 20% 2	2569
December	1st to 10th	Night	45% 4 10% 23% 17% 2	2660
	11th to 20th	Night	47% 3 7% 23% 17% 2	3281
	21st to end	Night	60% 6% 8% 15% 9% 2	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% 25% 36% 11% 1	270
	11th to 20th	Day	33% 23% 36% 8%	252
	21st to end	Day	20% 36% 33% 10% 2	264
February	1st to 10th	Day	28% 26% 36% 9%	240
	11th to 20th	Day	35% 28% 30% 6% 1	240
	21st to end	Day	35% 24% 30% 9% 2	198
March	1st to 10th	Day	26% 24% 40% 9%	240
	11th to 20th	Day	38% 19% 29% 12% 2	240
	21st to end	Day	34% 22% 33% 11% 1	322
April	1st to 10th	Day	22% 20% 38% 15% 4	420
	11th to 20th	Day	26% 20% 30% 18% 4	412
	21st to end	Day	24% 21% 31% 19% 3 1	420
May	1st to 10th	Day	24% 20% 33% 19% 4 1	438
	11th to 20th	Day	19% 15% 31% 22% 11% 2	625
	21st to end	Day	14% 10% 35% 26% 11% 4	679
June	1st to 10th	Day	11% 5% 24% 32% 22% 6%	630
	11th to 20th	Day	8% 3 26% 41% 19% 4	630
	21st to end	Day	6% 7% 31% 35% 17% 4	630
July	1st to 10th	Day	12% 1 18% 29% 30% 9%	621
	11th to 20th	Day	5% 4 21% 38% 26% 6%	618
	21st to end	Day	11% 4 17% 34% 28% 7%	684
August	1st to 10th	Day	9% 4 15% 42% 25% 5%	626
	11th to 20th	Day	12% 3 19% 33% 26% 7%	469
	21st to end	Day	14% 1 14% 34% 28% 9%	495
September	1st to 10th	Day	14% 5% 16% 34% 26% 6%	450
	11th to 20th	Day	8% 2 24% 34% 24% 8%	450
	21st to end	Day	11% 10% 26% 29% 19% 5%	361
October	1st to 10th	Day	14% 11% 36% 26% 10% 3	270
	11th to 20th	Day	23% 16% 38% 18% 4	270
	21st to end	Day	32% 19% 31% 16% 1	297
November	1st to 10th	Day	15% 17% 41% 19% 4 3	270
	11th to 20th	Day	24% 19% 35% 17% 5%	270
	21st to end	Day	28% 15% 37% 15% 4	270
December	1st to 10th	Day	21% 27% 31% 14% 5% 2	270
	11th to 20th	Day	27% 21% 34% 14% 3	270
	21st to end	Day	28% 27% 33% 9% 3	297
January	1st to 10th	Night	22% 23% 37% 15% 3	950
	11th to 20th	Night	24% 25% 35% 12% 4	921
	21st to end	Night	20% 23% 39% 17% 1	990
February	1st to 10th	Night	24% 22% 38% 15% 2	900
	11th to 20th	Night	23% 21% 41% 13% 2	762
	21st to end	Night	28% 23% 33% 15% 2	592
March	1st to 10th	Night	24% 18% 38% 18% 1	622
	11th to 20th	Night	25% 16% 36% 20% 4	540
	21st to end	Night	29% 16% 34% 18% 4	594
April	1st to 10th	Night	14% 19% 43% 22% 3	540
	11th to 20th	Night	19% 17% 34% 26% 5%	533
	21st to end	Night	22% 14% 37% 19% 6%	540
May	1st to 10th	Night	18% 10% 36% 28% 8%	540
	11th to 20th	Night	19% 7% 33% 26% 13% 2	531
	21st to end	Night	12% 7% 32% 30% 17% 2	584
June	1st to 10th	Night	8% 5% 21% 36% 28% 3	540
	11th to 20th	Night	7% 3 26% 40% 22% 2	540
	21st to end	Night	3 2 28% 44% 21% 2	540
July	1st to 10th	Night	11% 1 12% 37% 31% 7%	525
	11th to 20th	Night	6% 2 18% 39% 31% 4	522
	21st to end	Night	6% 2 17% 45% 28% 3	591
August	1st to 10th	Night	6% 2 17% 42% 32% 2	537
	11th to 20th	Night	6% 2 17% 41% 29% 4	534
	21st to end	Night	7% 3 16% 37% 32% 5%	594
September	1st to 10th	Night	14% 2 18% 36% 26% 5%	540
	11th to 20th	Night	12% 2 17% 39% 24% 6%	540
	21st to end	Night	11% 6% 26% 30% 22% 5%	674
October	1st to 10th	Night	9% 7% 33% 27% 22% 3	720
	11th to 20th	Night	18% 13% 36% 25% 7%	720
	21st to end	Night	25% 14% 33% 21% 6%	792
November	1st to 10th	Night	14% 11% 42% 25% 7%	740
	11th to 20th	Night	21% 16% 34% 22% 6%	760
	21st to end	Night	22% 19% 35% 18% 5%	859
December	1st to 10th	Night	23% 18% 36% 19% 4	950
	11th to 20th	Night	25% 15% 38% 19% 4	950
	21st to end	Night	24% 24% 36% 15% 2	1045

Page generated at 2024-01-11 21:33:52. Version ac07

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