Bickleton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bickleton clear sky chart from 2005-11-06 to 2024-01-12.

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	7% 6% 3 6% 5% 3 5% 5% 5% 7% 49%	74774
	Night	8% 7% 3 6% 6% 3 5% 5% 5% 7% 46%	74967
Transparency	Day	34% 7% 12% 23% 18% 6%	74477
	Night	37% 7% 13% 22% 15% 5%	74785
Seeing	Day	11% 13% 24% 26% 20% 7%	13345
	Night	11% 12% 23% 30% 20% 4	22503

By Month

Percentage Cloud Cover SW (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	10% 15% 6% 12% 8% 4 7% 6% 5% 8% 19%	1519
	11th to 20th	Day	11% 9% 4 10% 10% 4 7% 7% 5% 6% 28%	1451
	21st to end	Day	11% 10% 5% 9% 7% 4 7% 6% 7% 7% 26%	1589
February	1st to 10th	Day	10% 11% 4 8% 7% 5% 5% 6% 6% 8% 31%	1620
	11th to 20th	Day	9% 10% 4 6% 7% 4 5% 5% 7% 7% 37%	1593
	21st to end	Day	7% 8% 4 5% 5% 3 7% 6% 7% 9% 38%	1480
March	1st to 10th	Day	9% 9% 4 6% 6% 3 6% 7% 7% 8% 33%	1800
	11th to 20th	Day	6% 8% 4 8% 8% 4 6% 7% 7% 8% 35%	1930
	21st to end	Day	8% 9% 4 9% 8% 5% 7% 6% 7% 8% 29%	2317
April	1st to 10th	Day	7% 9% 4 7% 7% 4 6% 6% 6% 8% 37%	2160
	11th to 20th	Day	7% 8% 3 6% 6% 4 5% 5% 5% 7% 44%	2129
	21st to end	Day	6% 6% 2 5% 5% 3 5% 5% 7% 8% 48%	2301
May	1st to 10th	Day	6% 4 2 5% 5% 4 4 5% 6% 7% 51%	2520
	11th to 20th	Day	8% 6% 3 5% 7% 3 5% 5% 7% 9% 41%	2477
	21st to end	Day	9% 5% 3 6% 6% 4 5% 5% 6% 8% 43%	2723
June	1st to 10th	Day	11% 4 2 5% 4 3 4 5% 6% 8% 47%	2520
	11th to 20th	Day	7% 5% 2 4 5% 3 5% 5% 5% 6% 53%	2520
	21st to end	Day	5% 3 2 3 3 2 3 3 4 6% 66%	2520
July	1st to 10th	Day	2 1 1 3 3 2 3 3 4 5% 75%	2520
	11th to 20th	Day	2 1 1 2 2 2 2 3 4 4 75%	2520
	21st to end	Day	1 1 1 1 2 1 1 2 2 3 84%	2741
August	1st to 10th	Day	3 3 1 2 2 1 2 3 4 5% 75%	2507
	11th to 20th	Day	2 2 1 2 2 1 2 2 3 6% 77%	2293
	21st to end	Day	3 2 1 3 3 2 3 3 4 5% 71%	2376
September	1st to 10th	Day	3 2 1 2 2 1 3 3 4 7% 72%	2160
	11th to 20th	Day	4 4 2 4 4 2 4 5% 5% 6% 59%	2160
	21st to end	Day	6% 6% 2 4 4 3 4 3 4 7% 57%	1944
October	1st to 10th	Day	9% 6% 3 5% 4 2 3 4 5% 6% 54%	1800
	11th to 20th	Day	6% 6% 2 6% 5% 3 4 5% 7% 8% 48%	1800
	21st to end	Day	10% 7% 3 7% 5% 4 4 5% 5% 7% 42%	1818
November	1st to 10th	Day	8% 9% 4 8% 7% 3 5% 6% 6% 9% 37%	1674
	11th to 20th	Day	8% 9% 5% 6% 7% 5% 7% 7% 7% 8% 31%	1530
	21st to end	Day	7% 8% 5% 9% 7% 4 7% 6% 6% 8% 34%	1520
December	1st to 10th	Day	8% 10% 7% 10% 8% 4 5% 6% 6% 5% 32%	1520
	11th to 20th	Day	10% 12% 6% 11% 9% 5% 7% 6% 7% 7% 20%	1928
	21st to end	Day	9% 12% 5% 12% 10% 5% 6% 7% 5% 7% 23%	2794
January	1st to 10th	Night	11% 12% 5% 10% 9% 4 7% 6% 6% 7% 24%	2646
	11th to 20th	Night	10% 10% 6% 10% 7% 4 5% 6% 6% 8% 28%	2548
	21st to end	Night	10% 10% 5% 10% 6% 4 6% 5% 6% 7% 31%	2763
February	1st to 10th	Night	9% 11% 4 7% 6% 3 5% 6% 6% 8% 35%	2340
	11th to 20th	Night	9% 10% 4 7% 6% 3 5% 5% 6% 5% 40%	2254
	21st to end	Night	8% 8% 4 8% 6% 3 5% 6% 6% 8% 38%	1776
March	1st to 10th	Night	10% 7% 3 6% 6% 3 6% 6% 6% 8% 38%	2160
	11th to 20th	Night	7% 8% 4 7% 7% 4 5% 7% 6% 7% 38%	2026
	21st to end	Night	7% 9% 4 8% 7% 5% 6% 7% 6% 7% 34%	2039
April	1st to 10th	Night	9% 10% 4 7% 6% 3 5% 4 5% 9% 38%	1800
	11th to 20th	Night	7% 7% 3 5% 5% 3 4 3 5% 6% 51%	1779
	21st to end	Night	9% 6% 2 4 6% 4 4 5% 6% 9% 45%	1656
May	1st to 10th	Night	5% 5% 2 4 4 3 4 4 6% 9% 55%	1440
	11th to 20th	Night	9% 4 2 4 4 3 5% 5% 6% 9% 49%	1416
	21st to end	Night	6% 4 2 4 5% 3 5% 6% 7% 9% 48%	1552
June	1st to 10th	Night	11% 4 2 4 5% 3 4 5% 5% 7% 50%	1440
	11th to 20th	Night	9% 5% 2 4 4 2 4 3 5% 5% 58%	1440
	21st to end	Night	5% 2 1 3 5% 3 3 3 4 4 66%	1440
July	1st to 10th	Night	3 1 1 2 3 2 3 3 5% 5% 73%	1440
	11th to 20th	Night	3 1 1 2 1 1 2 3 3 5% 78%	1440
	21st to end	Night	1 1 1 2 1 1 2 2 3 4 82%	1576
August	1st to 10th	Night	3 2 1 2 3 2 2 3 3 6% 74%	1432
	11th to 20th	Night	2 2 2 2 1 2 3 3 6% 75%	1603
	21st to end	Night	2 2 1 3 2 2 3 4 4 6% 72%	1980
September	1st to 10th	Night	3 2 1 2 2 2 2 2 4 5% 75%	1800
	11th to 20th	Night	5% 3 1 3 4 2 4 4 4 5% 64%	1800
	21st to end	Night	5% 4 1 3 4 3 4 4 5% 5% 61%	2012
October	1st to 10th	Night	9% 5% 2 4 4 3 4 3 4 7% 55%	2160
	11th to 20th	Night	8% 5% 2 5% 5% 3 4 4 6% 6% 50%	2160
	21st to end	Night	9% 7% 2 6% 5% 3 4 4 5% 6% 49%	2538
November	1st to 10th	Night	11% 8% 3 7% 6% 3 5% 6% 6% 7% 38%	2405
	11th to 20th	Night	8% 7% 3 7% 7% 4 7% 6% 6% 8% 37%	2648
	21st to end	Night	7% 8% 5% 7% 7% 4 5% 6% 7% 7% 37%	2660
December	1st to 10th	Night	7% 12% 4 10% 8% 4 5% 5% 6% 8% 31%	2660
	11th to 20th	Night	10% 11% 5% 11% 9% 4 7% 5% 7% 8% 22%	3276
	21st to end	Night	9% 9% 5% 12% 9% 4 6% 5% 5% 7% 29%	4862

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	63% 9% 14% 11% 4	1519
	11th to 20th	Day	55% 10% 18% 13% 4	1451
	21st to end	Day	54% 7% 18% 15% 5% 1	1589
February	1st to 10th	Day	50% 10% 18% 17% 4 1	1620
	11th to 20th	Day	45% 8% 16% 22% 9% 1	1602
	21st to end	Day	40% 11% 19% 19% 11% 1	1480
March	1st to 10th	Day	44% 9% 13% 23% 11%	1800
	11th to 20th	Day	43% 8% 14% 25% 10%	1930
	21st to end	Day	48% 11% 14% 21% 6%	2317
April	1st to 10th	Day	42% 7% 11% 24% 14% 1	2160
	11th to 20th	Day	38% 7% 14% 24% 15% 3	2132
	21st to end	Day	31% 8% 13% 29% 17% 3	2301
May	1st to 10th	Day	29% 7% 10% 32% 20% 1	2520
	11th to 20th	Day	36% 7% 11% 28% 16% 2	2480
	21st to end	Day	36% 7% 13% 28% 14% 2	2724
June	1st to 10th	Day	33% 6% 11% 30% 17% 3	2520
	11th to 20th	Day	29% 6% 10% 32% 20% 3	2520
	21st to end	Day	19% 5% 9% 32% 26% 9%	2520
July	1st to 10th	Day	13% 3 6% 24% 36% 18%	2451
	11th to 20th	Day	13% 3 6% 16% 36% 26%	2445
	21st to end	Day	8% 3 3 15% 44% 28%	2589
August	1st to 10th	Day	13% 3 7% 21% 37% 19%	2490
	11th to 20th	Day	11% 3 6% 25% 39% 15%	2293
	21st to end	Day	16% 3 6% 29% 35% 10%	2376
September	1st to 10th	Day	13% 4 7% 30% 30% 16%	2160
	11th to 20th	Day	24% 6% 10% 25% 25% 10%	2160
	21st to end	Day	27% 5% 13% 31% 19% 6%	1944
October	1st to 10th	Day	32% 5% 11% 29% 21% 2	1800
	11th to 20th	Day	32% 7% 17% 27% 15% 2	1800
	21st to end	Day	40% 8% 13% 26% 13% 1	1818
November	1st to 10th	Day	43% 8% 17% 22% 8% 1	1674
	11th to 20th	Day	48% 10% 18% 17% 6% 1	1530
	21st to end	Day	46% 10% 19% 16% 8% 1	1520
December	1st to 10th	Day	52% 9% 14% 18% 7% 1	1520
	11th to 20th	Day	61% 10% 16% 10% 3	1928
	21st to end	Day	60% 9% 13% 12% 4	2794
January	1st to 10th	Night	59% 10% 15% 12% 4	2646
	11th to 20th	Night	54% 9% 15% 15% 6% 1	2548
	21st to end	Night	52% 6% 18% 18% 5% 1	2763
February	1st to 10th	Night	46% 10% 18% 21% 5% 1	2340
	11th to 20th	Night	42% 8% 17% 21% 11% 1	2256
	21st to end	Night	42% 9% 15% 22% 11% 2	1776
March	1st to 10th	Night	41% 8% 15% 23% 12% 1	2160
	11th to 20th	Night	42% 8% 14% 25% 9% 1	2026
	21st to end	Night	46% 8% 16% 22% 8%	2039
April	1st to 10th	Night	43% 5% 14% 25% 12% 2	1800
	11th to 20th	Night	34% 6% 13% 29% 16% 3	1779
	21st to end	Night	34% 8% 13% 27% 15% 4	1656
May	1st to 10th	Night	25% 5% 12% 35% 20% 3	1440
	11th to 20th	Night	30% 7% 12% 30% 18% 3	1416
	21st to end	Night	29% 7% 17% 33% 13% 2	1552
June	1st to 10th	Night	32% 7% 9% 31% 18% 3	1440
	11th to 20th	Night	27% 5% 10% 34% 20% 4	1440
	21st to end	Night	21% 5% 6% 31% 27% 9%	1440
July	1st to 10th	Night	14% 3 5% 21% 33% 23%	1400
	11th to 20th	Night	11% 2 6% 19% 32% 30%	1392
	21st to end	Night	7% 3 3 13% 40% 35%	1488
August	1st to 10th	Night	14% 3 4 20% 38% 21%	1424
	11th to 20th	Night	12% 3 4 26% 32% 22%	1603
	21st to end	Night	14% 4 5% 25% 37% 14%	1980
September	1st to 10th	Night	13% 3 7% 28% 31% 18%	1800
	11th to 20th	Night	22% 5% 8% 27% 24% 15%	1800
	21st to end	Night	23% 5% 10% 31% 21% 9%	2012
October	1st to 10th	Night	30% 4 9% 27% 26% 4	2160
	11th to 20th	Night	33% 5% 13% 27% 19% 4	2160
	21st to end	Night	35% 7% 12% 26% 19% 1	2538
November	1st to 10th	Night	43% 7% 14% 24% 12% 1	2405
	11th to 20th	Night	44% 11% 18% 21% 7%	2648
	21st to end	Night	43% 9% 16% 22% 9%	2660
December	1st to 10th	Night	52% 9% 16% 17% 5%	2660
	11th to 20th	Night	59% 9% 18% 12% 2	3276
	21st to end	Night	56% 7% 14% 13% 8% 1	4862

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	23% 18% 22% 20% 12% 5%	180
	11th to 20th	Day	21% 8% 29% 24% 15% 4	163
	21st to end	Day	17% 20% 17% 23% 18% 4	181
February	1st to 10th	Day	19% 19% 27% 24% 10% 1	340
	11th to 20th	Day	20% 19% 28% 22% 9% 2	343
	21st to end	Day	18% 20% 27% 22% 10% 3	346
March	1st to 10th	Day	13% 23% 32% 20% 10% 2	420
	11th to 20th	Day	14% 22% 22% 26% 14% 2	420
	21st to end	Day	16% 23% 26% 24% 11% 1	462
April	1st to 10th	Day	20% 19% 26% 20% 11% 3	420
	11th to 20th	Day	17% 17% 30% 22% 10% 5%	412
	21st to end	Day	11% 16% 32% 21% 15% 5%	420
May	1st to 10th	Day	11% 13% 24% 30% 16% 5%	423
	11th to 20th	Day	15% 11% 25% 22% 20% 7%	448
	21st to end	Day	8% 9% 21% 29% 24% 9%	485
June	1st to 10th	Day	10% 13% 22% 25% 22% 7%	450
	11th to 20th	Day	10% 16% 27% 28% 15% 4	450
	21st to end	Day	3 8% 22% 30% 27% 10%	450
July	1st to 10th	Day	1 4 22% 34% 32% 7%	446
	11th to 20th	Day	2 6% 20% 33% 30% 9%	444
	21st to end	Day	2 4 15% 32% 31% 16%	487
August	1st to 10th	Day	4 4 14% 31% 30% 16%	447
	11th to 20th	Day	3 2 16% 24% 36% 18%	437
	21st to end	Day	4 6% 21% 32% 25% 11%	495
September	1st to 10th	Day	4 6% 21% 32% 26% 11%	450
	11th to 20th	Day	8% 7% 24% 27% 26% 8%	450
	21st to end	Day	10% 10% 25% 27% 24% 4	450
October	1st to 10th	Day	11% 12% 27% 24% 21% 5%	450
	11th to 20th	Day	12% 17% 20% 24% 21% 7%	450
	21st to end	Day	17% 20% 23% 23% 12% 5%	333
November	1st to 10th	Day	18% 18% 22% 27% 13% 2	270
	11th to 20th	Day	21% 21% 18% 21% 15% 5%	185
	21st to end	Day	16% 14% 28% 21% 16% 5%	180
December	1st to 10th	Day	19% 14% 23% 22% 14% 8%	180
	11th to 20th	Day	15% 21% 29% 21% 13% 1	180
	21st to end	Day	17% 13% 27% 26% 17% 1	198
January	1st to 10th	Night	17% 19% 20% 27% 15% 2	760
	11th to 20th	Night	14% 13% 23% 27% 20% 3	728
	21st to end	Night	15% 11% 20% 29% 20% 4	792
February	1st to 10th	Night	14% 18% 21% 29% 14% 4	720
	11th to 20th	Night	13% 18% 23% 25% 19% 2	704
	21st to end	Night	15% 16% 27% 29% 12% 1	592
March	1st to 10th	Night	12% 16% 29% 25% 16% 2	720
	11th to 20th	Night	10% 17% 27% 29% 15% 2	720
	21st to end	Night	11% 18% 32% 25% 12% 2	792
April	1st to 10th	Night	14% 16% 25% 27% 15% 3	720
	11th to 20th	Night	10% 16% 29% 24% 16% 4	711
	21st to end	Night	9% 15% 29% 30% 15% 3	576
May	1st to 10th	Night	7% 11% 27% 33% 19% 4	360
	11th to 20th	Night	10% 6% 25% 30% 24% 5%	354
	21st to end	Night	7% 5% 27% 33% 24% 5%	389
June	1st to 10th	Night	12% 7% 31% 29% 18% 3	360
	11th to 20th	Night	10% 10% 30% 34% 15% 1	360
	21st to end	Night	6% 9% 18% 41% 24% 4	360
July	1st to 10th	Night	3 1 21% 43% 28% 3	350
	11th to 20th	Night	4 5% 23% 44% 22% 3	348
	21st to end	Night	1 3 18% 41% 33% 5%	394
August	1st to 10th	Night	3 3 14% 41% 35% 5%	358
	11th to 20th	Night	3 1 11% 33% 36% 16%	535
	21st to end	Night	3 6% 22% 35% 28% 7%	792
September	1st to 10th	Night	3 4 19% 35% 32% 7%	720
	11th to 20th	Night	6% 4 20% 28% 31% 11%	720
	21st to end	Night	8% 8% 22% 26% 30% 8%	720
October	1st to 10th	Night	10% 7% 18% 37% 22% 6%	720
	11th to 20th	Night	12% 12% 19% 26% 25% 6%	720
	21st to end	Night	11% 14% 26% 26% 17% 6%	792
November	1st to 10th	Night	16% 15% 22% 31% 15% 1	740
	11th to 20th	Night	14% 18% 25% 23% 16% 4	760
	21st to end	Night	10% 16% 21% 30% 20% 4	760
December	1st to 10th	Night	13% 12% 22% 29% 20% 3	760
	11th to 20th	Night	19% 15% 19% 31% 15% 1	760
	21st to end	Night	17% 17% 23% 30% 12% 1	836

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