Bonny Doon Airfield
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bonny Doon Airfield clear sky chart from 2005-11-06 to 2024-03-28.

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	10% 5% 2 4 4 2 3 4 5% 8% 54%	78942
	Night	11% 5% 2 4 4 2 4 4 5% 7% 51%	81084
Transparency	Day	30% 4 9% 21% 22% 13%	78664
	Night	34% 5% 10% 19% 20% 13%	80884
Seeing	Day	9% 8% 22% 33% 22% 5%	14609
	Night	10% 5% 15% 31% 30% 8%	24118

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	16% 7% 2 6% 5% 2 3 5% 5% 6% 42%	2765
	11th to 20th	Day	18% 7% 3 7% 6% 4 5% 4 5% 7% 34%	2860
	21st to end	Day	21% 8% 3 6% 6% 3 5% 5% 6% 7% 31%	3146
February	1st to 10th	Day	21% 4 2 4 4 2 4 3 5% 6% 44%	1710
	11th to 20th	Day	16% 6% 2 5% 4 3 4 4 6% 7% 44%	1764
	21st to end	Day	16% 6% 3 5% 4 2 4 4 4 6% 46%	1570
March	1st to 10th	Day	18% 7% 3 7% 5% 4 5% 5% 5% 7% 35%	2057
	11th to 20th	Day	17% 7% 3 5% 5% 2 4 5% 5% 8% 38%	2090
	21st to end	Day	14% 5% 3 4 4 3 5% 5% 5% 7% 46%	2284
April	1st to 10th	Day	16% 6% 2 4 3 3 4 4 5% 7% 46%	2160
	11th to 20th	Day	10% 5% 2 4 3 2 4 5% 5% 8% 53%	2129
	21st to end	Day	7% 5% 2 5% 4 2 3 4 5% 8% 56%	2160
May	1st to 10th	Day	7% 5% 2 4 3 2 3 4 5% 8% 57%	2200
	11th to 20th	Day	6% 4 2 3 3 2 4 3 4 8% 61%	2317
	21st to end	Day	6% 6% 3 5% 5% 2 4 4 4 7% 52%	2723
June	1st to 10th	Day	5% 4 2 4 4 2 3 4 5% 8% 58%	2520
	11th to 20th	Day	3 2 1 3 3 2 3 3 5% 8% 68%	2520
	21st to end	Day	2 3 1 3 3 2 2 3 3 7% 71%	2520
July	1st to 10th	Day	1 2 1 3 3 1 3 3 4 9% 68%	2492
	11th to 20th	Day	2 2 1 3 4 2 4 3 5% 10% 64%	2340
	21st to end	Day	1 2 1 2 2 2 3 3 5% 11% 68%	2546
August	1st to 10th	Day	1 3 2 4 3 2 2 4 5% 11% 63%	2328
	11th to 20th	Day	1 2 1 2 3 2 3 3 5% 9% 70%	2169
	21st to end	Day	1 3 2 4 4 2 3 3 4 10% 66%	2376
September	1st to 10th	Day	2 2 1 2 2 1 2 2 3 7% 76%	2160
	11th to 20th	Day	3 3 2 4 3 2 3 4 5% 9% 62%	2160
	21st to end	Day	4 2 1 2 2 1 3 3 4 5% 74%	1911
October	1st to 10th	Day	4 3 2 3 3 1 3 3 4 7% 67%	1800
	11th to 20th	Day	6% 3 2 3 4 2 3 4 4 7% 62%	1800
	21st to end	Day	7% 4 2 4 3 2 3 3 3 7% 62%	1980
November	1st to 10th	Day	10% 4 2 4 4 2 4 5% 4 8% 54%	1846
	11th to 20th	Day	11% 4 3 4 4 2 4 5% 6% 7% 52%	1710
	21st to end	Day	12% 4 1 3 3 2 2 4 4 7% 56%	1587
December	1st to 10th	Day	15% 6% 2 4 4 2 5% 4 6% 8% 44%	1520
	11th to 20th	Day	31% 7% 2 5% 4 2 3 3 5% 6% 32%	1928
	21st to end	Day	24% 7% 2 4 5% 3 3 4 5% 7% 37%	2794
January	1st to 10th	Night	14% 7% 2 5% 4 2 4 5% 5% 7% 46%	4185
	11th to 20th	Night	20% 7% 3 5% 5% 3 5% 5% 6% 6% 33%	4110
	21st to end	Night	21% 7% 3 6% 7% 3 4 4 5% 7% 33%	4521
February	1st to 10th	Night	19% 5% 2 3 4 1 3 4 4 7% 48%	2470
	11th to 20th	Night	14% 5% 2 4 4 2 5% 5% 6% 8% 45%	2301
	21st to end	Night	12% 7% 2 4 4 2 3 4 6% 6% 50%	1884
March	1st to 10th	Night	18% 9% 3 6% 5% 3 4 5% 5% 5% 37%	2119
	11th to 20th	Night	16% 6% 2 5% 5% 2 3 4 6% 7% 45%	2090
	21st to end	Night	14% 6% 2 4 5% 3 4 4 5% 7% 48%	2225
April	1st to 10th	Night	13% 6% 2 4 5% 2 4 5% 5% 7% 48%	1800
	11th to 20th	Night	11% 4 2 4 4 2 3 4 5% 7% 54%	1779
	21st to end	Night	5% 4 2 3 3 2 4 4 7% 10% 57%	1800
May	1st to 10th	Night	5% 5% 2 5% 5% 1 3 4 5% 8% 57%	1756
	11th to 20th	Night	4 4 2 4 4 2 4 4 6% 12% 55%	1572
	21st to end	Night	4 5% 3 5% 4 3 4 5% 6% 8% 52%	1552
June	1st to 10th	Night	3 3 1 4 4 2 3 5% 7% 9% 58%	1440
	11th to 20th	Night	1 3 2 4 4 3 3 4 6% 8% 63%	1440
	21st to end	Night	2 3 1 2 3 3 4 4 5% 7% 67%	1440
July	1st to 10th	Night	1 2 2 4 5% 2 3 4 4 8% 66%	1463
	11th to 20th	Night	1 2 2 5% 5% 2 3 5% 6% 10% 60%	1620
	21st to end	Night	1 2 2 5% 7% 3 5% 7% 8% 10% 50%	1773
August	1st to 10th	Night	1 4 1 6% 7% 4 4 5% 7% 10% 52%	1611
	11th to 20th	Night	3 2 5% 4 3 3 5% 7% 10% 59%	1730
	21st to end	Night	1 2 2 7% 5% 3 4 4 5% 8% 60%	1980
September	1st to 10th	Night	1 2 1 2 3 2 3 4 4 7% 71%	1800
	11th to 20th	Night	4 2 2 5% 4 2 3 4 5% 9% 61%	1800
	21st to end	Night	3 3 2 3 2 1 2 2 3 6% 73%	2042
October	1st to 10th	Night	4 3 1 4 4 2 3 3 4 6% 66%	2160
	11th to 20th	Night	5% 4 2 4 3 2 3 4 5% 7% 62%	2160
	21st to end	Night	7% 4 1 3 3 2 3 3 4 6% 64%	2376
November	1st to 10th	Night	8% 4 2 4 3 2 3 3 4 7% 59%	2229
	11th to 20th	Night	10% 4 2 3 4 2 3 4 6% 9% 53%	2470
	21st to end	Night	8% 5% 2 4 3 2 3 3 4 6% 58%	2588
December	1st to 10th	Night	16% 5% 2 4 4 2 4 3 4 6% 49%	2660
	11th to 20th	Night	30% 8% 2 4 3 2 3 4 5% 6% 33%	3276
	21st to end	Night	22% 7% 2 5% 5% 3 4 4 5% 7% 37%	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	39% 5% 13% 28% 10% 4	2765
	11th to 20th	Day	48% 6% 12% 15% 11% 8%	2860
	21st to end	Day	50% 5% 10% 16% 13% 5%	3146
February	1st to 10th	Day	40% 3 7% 20% 19% 10%	1710
	11th to 20th	Day	38% 5% 9% 20% 20% 8%	1773
	21st to end	Day	38% 5% 8% 24% 18% 7%	1570
March	1st to 10th	Day	45% 6% 9% 20% 15% 4	2057
	11th to 20th	Day	43% 4 10% 20% 17% 5%	2090
	21st to end	Day	36% 7% 14% 21% 17% 4	2284
April	1st to 10th	Day	36% 5% 15% 19% 21% 5%	2160
	11th to 20th	Day	29% 5% 14% 26% 20% 7%	2132
	21st to end	Day	28% 5% 13% 29% 21% 4	2160
May	1st to 10th	Day	25% 4 12% 26% 28% 5%	2200
	11th to 20th	Day	24% 3 13% 29% 23% 8%	2320
	21st to end	Day	33% 5% 15% 24% 20% 4	2724
June	1st to 10th	Day	26% 5% 13% 25% 24% 6%	2520
	11th to 20th	Day	19% 4 11% 24% 29% 13%	2520
	21st to end	Day	20% 3 4 18% 31% 23%	2520
July	1st to 10th	Day	19% 3 4 13% 32% 30%	2424
	11th to 20th	Day	22% 4 5% 14% 26% 28%	2271
	21st to end	Day	19% 3 4 16% 31% 27%	2405
August	1st to 10th	Day	24% 3 4 18% 29% 23%	2312
	11th to 20th	Day	17% 4 3 18% 29% 28%	2169
	21st to end	Day	23% 3 3 19% 28% 24%	2376
September	1st to 10th	Day	16% 2 3 14% 28% 37%	2160
	11th to 20th	Day	22% 3 8% 21% 30% 15%	2160
	21st to end	Day	15% 2 6% 22% 36% 18%	1911
October	1st to 10th	Day	18% 3 8% 20% 27% 23%	1800
	11th to 20th	Day	23% 3 10% 19% 23% 22%	1800
	21st to end	Day	26% 2 9% 22% 21% 20%	1980
November	1st to 10th	Day	29% 4 7% 26% 23% 11%	1846
	11th to 20th	Day	30% 4 11% 23% 23% 9%	1710
	21st to end	Day	29% 2 11% 19% 28% 12%	1587
December	1st to 10th	Day	38% 4 10% 20% 17% 11%	1520
	11th to 20th	Day	52% 4 10% 13% 14% 6%	1928
	21st to end	Day	46% 4 12% 23% 12% 4	2794
January	1st to 10th	Night	36% 4 18% 26% 12% 4	4185
	11th to 20th	Night	47% 5% 15% 14% 11% 8%	4110
	21st to end	Night	49% 4 12% 15% 12% 7%	4521
February	1st to 10th	Night	38% 3 8% 18% 19% 14%	2470
	11th to 20th	Night	35% 5% 11% 19% 22% 8%	2303
	21st to end	Night	32% 4 11% 30% 17% 6%	1884
March	1st to 10th	Night	47% 5% 11% 17% 15% 5%	2119
	11th to 20th	Night	38% 4 9% 22% 21% 6%	2090
	21st to end	Night	36% 5% 14% 21% 17% 6%	2225
April	1st to 10th	Night	35% 5% 15% 21% 18% 6%	1800
	11th to 20th	Night	31% 6% 11% 27% 17% 8%	1779
	21st to end	Night	24% 8% 12% 30% 20% 6%	1800
May	1st to 10th	Night	28% 5% 11% 22% 24% 11%	1756
	11th to 20th	Night	29% 6% 13% 22% 23% 7%	1573
	21st to end	Night	30% 10% 15% 20% 21% 4	1552
June	1st to 10th	Night	26% 9% 9% 24% 23% 9%	1440
	11th to 20th	Night	25% 5% 8% 15% 29% 19%	1440
	21st to end	Night	26% 6% 4 14% 26% 24%	1440
July	1st to 10th	Night	24% 6% 2 9% 26% 33%	1422
	11th to 20th	Night	24% 8% 5% 13% 20% 29%	1566
	21st to end	Night	36% 9% 4 11% 19% 22%	1674
August	1st to 10th	Night	38% 7% 3 14% 19% 19%	1602
	11th to 20th	Night	27% 5% 2 12% 26% 28%	1730
	21st to end	Night	30% 7% 3 12% 24% 25%	1980
September	1st to 10th	Night	18% 5% 3 11% 27% 36%	1800
	11th to 20th	Night	25% 5% 5% 21% 29% 17%	1800
	21st to end	Night	17% 3 4 19% 35% 22%	2042
October	1st to 10th	Night	23% 4 8% 16% 23% 27%	2160
	11th to 20th	Night	25% 5% 7% 20% 21% 23%	2160
	21st to end	Night	25% 3 6% 21% 23% 22%	2376
November	1st to 10th	Night	27% 3 8% 25% 22% 14%	2229
	11th to 20th	Night	29% 4 11% 22% 25% 10%	2470
	21st to end	Night	28% 4 9% 20% 23% 16%	2588
December	1st to 10th	Night	36% 3 10% 19% 18% 13%	2660
	11th to 20th	Night	52% 3 11% 14% 16% 5%	3276
	21st to end	Night	46% 4 14% 18% 13% 5%	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	29% 11% 22% 20% 16% 2	315
	11th to 20th	Day	18% 8% 23% 32% 17% 3	370
	21st to end	Day	18% 7% 23% 28% 21% 3	407
February	1st to 10th	Day	21% 11% 21% 23% 19% 5%	370
	11th to 20th	Day	18% 15% 26% 25% 15% 1	413
	21st to end	Day	12% 13% 28% 32% 13% 2	382
March	1st to 10th	Day	23% 15% 25% 27% 10% 1	460
	11th to 20th	Day	22% 12% 23% 24% 15% 4	460
	21st to end	Day	16% 13% 32% 27% 10% 2	491
April	1st to 10th	Day	19% 10% 31% 27% 12% 1	420
	11th to 20th	Day	12% 15% 29% 29% 13% 2	412
	21st to end	Day	6% 14% 32% 28% 15% 5%	420
May	1st to 10th	Day	9% 14% 27% 31% 15% 3	423
	11th to 20th	Day	11% 9% 32% 31% 15% 3	448
	21st to end	Day	9% 10% 28% 29% 19% 5%	485
June	1st to 10th	Day	6% 8% 24% 37% 21% 4	450
	11th to 20th	Day	3 8% 26% 40% 20% 3	450
	21st to end	Day	1 3 20% 47% 25% 5%	450
July	1st to 10th	Day	2 1 17% 44% 32% 4	446
	11th to 20th	Day	1 14% 48% 30% 7%	444
	21st to end	Day	1 12% 41% 37% 9%	487
August	1st to 10th	Day	3 1 21% 41% 28% 5%	447
	11th to 20th	Day	1 12% 44% 32% 10%	437
	21st to end	Day	2 3 13% 40% 35% 8%	495
September	1st to 10th	Day	2 2 14% 39% 34% 8%	450
	11th to 20th	Day	3 4 24% 37% 26% 6%	450
	21st to end	Day	4 7% 16% 33% 32% 9%	450
October	1st to 10th	Day	4 4 25% 30% 27% 10%	450
	11th to 20th	Day	6% 6% 17% 31% 30% 10%	450
	21st to end	Day	8% 6% 21% 29% 27% 9%	495
November	1st to 10th	Day	7% 10% 20% 27% 27% 9%	442
	11th to 20th	Day	9% 6% 20% 29% 25% 11%	270
	21st to end	Day	8% 7% 20% 32% 25% 8%	212
December	1st to 10th	Day	17% 8% 18% 28% 23% 6%	180
	11th to 20th	Day	14% 16% 22% 19% 20% 8%	180
	21st to end	Day	19% 17% 21% 23% 15% 5%	198
January	1st to 10th	Night	19% 7% 17% 27% 25% 6%	760
	11th to 20th	Night	19% 5% 13% 31% 24% 9%	760
	21st to end	Night	19% 5% 14% 30% 27% 6%	836
February	1st to 10th	Night	19% 8% 14% 28% 24% 7%	760
	11th to 20th	Night	15% 9% 17% 32% 21% 6%	744
	21st to end	Night	15% 9% 22% 31% 20% 3	628
March	1st to 10th	Night	20% 9% 19% 26% 22% 4	760
	11th to 20th	Night	17% 7% 16% 29% 26% 5%	760
	21st to end	Night	15% 8% 24% 31% 19% 3	820
April	1st to 10th	Night	15% 6% 22% 32% 21% 3	720
	11th to 20th	Night	11% 12% 20% 30% 20% 6%	711
	21st to end	Night	7% 7% 28% 28% 22% 9%	720
May	1st to 10th	Night	7% 6% 22% 33% 27% 6%	676
	11th to 20th	Night	5% 4 19% 33% 32% 7%	510
	21st to end	Night	5% 8% 20% 36% 25% 6%	389
June	1st to 10th	Night	4 3 16% 39% 31% 6%	360
	11th to 20th	Night	2 3 15% 44% 32% 4	360
	21st to end	Night	3 2 11% 37% 41% 7%	360
July	1st to 10th	Night	2 9% 34% 45% 9%	372
	11th to 20th	Night	2 1 4 32% 43% 19%	522
	21st to end	Night	2 5% 32% 47% 15%	591
August	1st to 10th	Night	3 2 11% 32% 42% 9%	537
	11th to 20th	Night	1 2 9% 33% 45% 11%	662
	21st to end	Night	2 1 8% 29% 48% 12%	792
September	1st to 10th	Night	1 1 8% 31% 44% 14%	720
	11th to 20th	Night	4 2 12% 32% 40% 10%	720
	21st to end	Night	3 3 10% 27% 41% 15%	720
October	1st to 10th	Night	5% 3 13% 31% 37% 13%	720
	11th to 20th	Night	7% 4 10% 25% 41% 13%	720
	21st to end	Night	8% 3 11% 30% 31% 16%	792
November	1st to 10th	Night	8% 4 15% 27% 34% 11%	740
	11th to 20th	Night	11% 3 13% 33% 33% 8%	760
	21st to end	Night	10% 4 16% 35% 28% 7%	760
December	1st to 10th	Night	18% 5% 16% 30% 24% 7%	760
	11th to 20th	Night	22% 6% 16% 31% 22% 4	760
	21st to end	Night	17% 11% 20% 30% 19% 3	836

Page generated at 2024-03-24 20:37:00. Version ac07

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