Dixon Ball Field
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dixon Ball Field clear sky chart from 2005-11-06 to 2026-01-02.

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	2 4 1 4 3 3 4 4 6% 8% 60%	135471
	Night	3 5% 2 5% 3 4 4 3 5% 7% 58%	133341
Transparency	Day	19% 8% 14% 23% 25% 12%	130469
	Night	22% 7% 12% 21% 26% 11%	129347
Seeing	Day	6% 12% 27% 31% 19% 4	16736
	Night	5% 6% 29% 42% 17% 1	26909

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	1 7% 4 6% 3 3 3 3 5% 6% 58%	3876
	11th to 20th	Day	2 4 2 4 3 3 4 4 5% 5% 64%	4100
	21st to end	Day	2 6% 2 5% 4 4 4 3 4 5% 59%	4510
February	1st to 10th	Day	1 7% 2 5% 3 4 3 3 5% 8% 58%	1821
	11th to 20th	Day	3 6% 2 6% 3 3 3 3 5% 7% 58%	1949
	21st to end	Day	2 8% 2 5% 3 3 3 4 6% 7% 58%	1650
March	1st to 10th	Day	2 4 2 5% 3 3 4 3 5% 6% 63%	4675
	11th to 20th	Day	2 8% 3 6% 4 4 5% 3 5% 8% 50%	5000
	21st to end	Day	2 5% 2 5% 4 4 5% 3 5% 8% 57%	5700
April	1st to 10th	Day	3 5% 2 4 3 3 3 3 5% 7% 62%	2400
	11th to 20th	Day	3 4 2 4 3 4 4 3 5% 7% 61%	2371
	21st to end	Day	3 5% 1 3 3 3 3 4 5% 9% 61%	2400
May	1st to 10th	Day	4 3 1 4 3 4 4 4 6% 8% 58%	5440
	11th to 20th	Day	3 3 1 3 3 4 4 3 6% 8% 63%	5820
	21st to end	Day	1 2 1 2 2 2 3 3 5% 8% 69%	6925
June	1st to 10th	Day	2 2 1 2 3 3 5% 6% 7% 9% 62%	2800
	11th to 20th	Day	1 1 1 2 2 2 3 3 6% 7% 71%	2800
	21st to end	Day	4 3 1 4 3 3 4 5% 8% 8% 57%	2800
July	1st to 10th	Day	1 2 1 3 3 4 5% 4 7% 8% 63%	6339
	11th to 20th	Day	1 1 1 2 3 4 6% 6% 11% 14% 51%	5984
	21st to end	Day	2 3 1 5% 5% 6% 6% 6% 9% 11% 45%	6401
August	1st to 10th	Day	2 2 1 4 4 5% 6% 6% 9% 12% 48%	5651
	11th to 20th	Day	1 1 1 3 2 4 5% 4 8% 11% 59%	5366
	21st to end	Day	2 3 1 4 3 5% 6% 6% 11% 13% 45%	5984
September	1st to 10th	Day	4 3 1 4 4 4 5% 5% 6% 9% 55%	2400
	11th to 20th	Day	4 3 1 4 3 3 4 4 6% 7% 61%	2400
	21st to end	Day	3 2 1 2 2 2 3 3 4 6% 70%	2182
October	1st to 10th	Day	2 2 1 3 2 2 3 2 4 6% 74%	3270
	11th to 20th	Day	5% 4 1 5% 3 3 4 4 5% 6% 61%	3250
	21st to end	Day	3 2 1 2 2 2 2 2 3 4 77%	3548
November	1st to 10th	Day	2 4 1 3 1 2 3 2 4 7% 71%	1948
	11th to 20th	Day	2 3 1 2 2 3 2 2 4 6% 72%	1890
	21st to end	Day	3 6% 2 5% 3 3 3 3 4 6% 63%	1890
December	1st to 10th	Day	2 4 1 2 2 1 2 1 3 6% 77%	2733
	11th to 20th	Day	2 4 1 4 3 2 3 3 4 9% 65%	3106
	21st to end	Day	2 5% 2 4 3 3 3 2 4 6% 66%	4092
January	1st to 10th	Night	1 7% 3 7% 4 4 4 3 5% 6% 57%	6140
	11th to 20th	Night	2 7% 2 6% 4 4 4 3 4 5% 58%	5880
	21st to end	Night	3 7% 3 8% 4 4 3 2 4 7% 56%	6468
February	1st to 10th	Night	2 7% 2 6% 3 3 3 3 4 6% 61%	2576
	11th to 20th	Night	4 9% 2 5% 4 3 4 3 4 6% 56%	2338
	21st to end	Night	5% 8% 2 4 3 3 2 2 4 6% 61%	1980
March	1st to 10th	Night	3 10% 2 4 3 3 3 3 4 5% 60%	5203
	11th to 20th	Night	5% 8% 3 7% 4 4 4 3 4 5% 55%	5000
	21st to end	Night	5% 8% 2 4 3 3 4 3 4 7% 57%	5265
April	1st to 10th	Night	3 5% 2 5% 4 3 4 4 4 8% 59%	2000
	11th to 20th	Night	4 7% 2 5% 3 3 4 3 5% 7% 57%	1977
	21st to end	Night	4 5% 2 4 3 4 3 4 5% 5% 61%	2000
May	1st to 10th	Night	7% 6% 2 5% 3 4 4 3 5% 7% 54%	4540
	11th to 20th	Night	4 4 2 5% 4 4 4 4 6% 7% 57%	4063
	21st to end	Night	3 3 1 4 3 3 3 4 6% 6% 65%	3972
June	1st to 10th	Night	1 1 1 4 3 4 4 3 7% 10% 60%	1600
	11th to 20th	Night	2 3 1 3 3 3 4 3 4 6% 69%	1600
	21st to end	Night	4 3 1 4 4 4 4 4 7% 10% 54%	1600
July	1st to 10th	Night	2 3 1 6% 4 5% 5% 4 6% 8% 57%	3640
	11th to 20th	Night	1 2 1 4 4 5% 8% 7% 11% 14% 43%	3978
	21st to end	Night	4 4 2 7% 6% 6% 7% 6% 10% 12% 37%	4472
August	1st to 10th	Night	2 3 1 6% 6% 7% 7% 6% 8% 11% 42%	4160
	11th to 20th	Night	2 3 1 5% 5% 6% 6% 6% 9% 14% 42%	4483
	21st to end	Night	4 5% 2 8% 6% 7% 8% 6% 9% 11% 33%	4993
September	1st to 10th	Night	5% 4 1 4 4 5% 5% 4 7% 9% 52%	2000
	11th to 20th	Night	4 3 1 4 2 3 4 4 5% 9% 61%	2000
	21st to end	Night	5% 3 1 4 2 2 3 3 5% 7% 65%	2213
October	1st to 10th	Night	3 2 1 2 2 2 2 2 3 6% 74%	3920
	11th to 20th	Night	5% 3 1 4 3 3 3 2 4 7% 64%	3898
	21st to end	Night	3 2 1 2 1 2 2 2 3 5% 76%	4252
November	1st to 10th	Night	3 3 1 1 1 2 2 2 4 6% 75%	2549
	11th to 20th	Night	2 3 1 2 2 2 2 2 3 6% 76%	2730
	21st to end	Night	5% 6% 1 3 2 2 2 3 5% 6% 64%	2730
December	1st to 10th	Night	3 4 2 3 2 2 2 2 3 4 75%	4672
	11th to 20th	Night	2 4 1 3 2 2 3 2 4 8% 68%	5321
	21st to end	Night	2 6% 3 5% 3 3 3 3 4 6% 61%	7128

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	24% 6% 13% 28% 25% 3	3877
	11th to 20th	Day	17% 8% 14% 25% 21% 16%	4100
	21st to end	Day	25% 8% 10% 18% 26% 13%	4510
February	1st to 10th	Day	26% 7% 14% 24% 21% 8%	1821
	11th to 20th	Day	26% 6% 11% 25% 25% 7%	1959
	21st to end	Day	24% 5% 12% 17% 28% 14%	1650
March	1st to 10th	Day	18% 6% 10% 17% 35% 15%	4675
	11th to 20th	Day	23% 10% 14% 21% 26% 6%	5000
	21st to end	Day	22% 6% 11% 35% 21% 5%	5700
April	1st to 10th	Day	21% 5% 12% 23% 26% 13%	2400
	11th to 20th	Day	22% 6% 10% 18% 29% 13%	2374
	21st to end	Day	20% 7% 11% 23% 28% 11%	2400
May	1st to 10th	Day	18% 7% 15% 22% 25% 12%	5440
	11th to 20th	Day	17% 7% 12% 17% 33% 14%	5824
	21st to end	Day	11% 5% 12% 18% 30% 25%	6926
June	1st to 10th	Day	15% 8% 15% 22% 22% 18%	2800
	11th to 20th	Day	11% 5% 9% 16% 25% 33%	2800
	21st to end	Day	23% 7% 13% 19% 22% 18%	2800
July	1st to 10th	Day	17% 9% 13% 15% 19% 26%	6271
	11th to 20th	Day	15% 11% 25% 33% 10% 6%	5912
	21st to end	Day	26% 12% 22% 25% 12% 2	6217
August	1st to 10th	Day	26% 16% 21% 22% 10% 5%	4113
	11th to 20th	Day	16% 9% 19% 24% 21% 10%	3882
	21st to end	Day	24% 13% 24% 22% 14% 3	4311
September	1st to 10th	Day	24% 9% 16% 22% 21% 8%	2400
	11th to 20th	Day	21% 8% 12% 18% 27% 13%	2400
	21st to end	Day	14% 7% 12% 21% 34% 12%	2182
October	1st to 10th	Day	13% 5% 7% 15% 37% 22%	3270
	11th to 20th	Day	20% 7% 9% 17% 33% 13%	3250
	21st to end	Day	12% 4 7% 23% 40% 15%	3548
November	1st to 10th	Day	13% 4 13% 24% 35% 11%	1948
	11th to 20th	Day	14% 5% 10% 29% 35% 7%	1890
	21st to end	Day	21% 5% 11% 25% 27% 11%	1890
December	1st to 10th	Day	13% 3 9% 32% 36% 7%	2733
	11th to 20th	Day	18% 7% 9% 30% 32% 4	3104
	21st to end	Day	18% 5% 12% 28% 31% 6%	4092
January	1st to 10th	Night	27% 7% 10% 28% 23% 5%	6140
	11th to 20th	Night	17% 14% 13% 22% 22% 12%	5880
	21st to end	Night	27% 8% 9% 20% 29% 7%	6468
February	1st to 10th	Night	26% 6% 15% 23% 22% 8%	2576
	11th to 20th	Night	28% 6% 13% 24% 22% 6%	2338
	21st to end	Night	24% 4 10% 19% 31% 12%	1980
March	1st to 10th	Night	23% 4 10% 14% 37% 12%	5203
	11th to 20th	Night	27% 8% 10% 21% 26% 9%	5000
	21st to end	Night	22% 6% 12% 33% 22% 4	5265
April	1st to 10th	Night	21% 6% 10% 23% 28% 12%	2000
	11th to 20th	Night	25% 5% 12% 17% 26% 15%	1977
	21st to end	Night	22% 7% 11% 22% 27% 11%	2000
May	1st to 10th	Night	23% 6% 15% 19% 23% 13%	4537
	11th to 20th	Night	21% 8% 11% 19% 24% 17%	4064
	21st to end	Night	15% 6% 13% 14% 23% 29%	3972
June	1st to 10th	Night	18% 7% 17% 20% 19% 19%	1600
	11th to 20th	Night	15% 4 9% 12% 25% 34%	1600
	21st to end	Night	23% 8% 14% 15% 21% 19%	1600
July	1st to 10th	Night	25% 9% 12% 11% 16% 28%	3600
	11th to 20th	Night	24% 14% 28% 22% 6% 8%	3927
	21st to end	Night	33% 14% 22% 20% 10% 1	4344
August	1st to 10th	Night	34% 16% 21% 14% 10% 6%	3022
	11th to 20th	Night	26% 12% 20% 18% 13% 12%	3243
	21st to end	Night	36% 13% 19% 18% 10% 3	3597
September	1st to 10th	Night	25% 10% 14% 24% 18% 9%	2000
	11th to 20th	Night	18% 8% 15% 17% 25% 16%	2000
	21st to end	Night	18% 7% 11% 19% 33% 13%	2213
October	1st to 10th	Night	13% 5% 8% 14% 40% 21%	3920
	11th to 20th	Night	18% 6% 9% 18% 33% 16%	3898
	21st to end	Night	11% 4 6% 25% 38% 17%	4252
November	1st to 10th	Night	11% 4 9% 25% 41% 11%	2549
	11th to 20th	Night	13% 3 9% 30% 36% 9%	2730
	21st to end	Night	23% 4 10% 23% 29% 11%	2730
December	1st to 10th	Night	15% 4 7% 33% 34% 7%	4672
	11th to 20th	Night	17% 5% 8% 28% 37% 5%	5322
	21st to end	Night	23% 5% 13% 26% 30% 3	7128

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	8% 12% 38% 30% 11% 1	303
	11th to 20th	Day	10% 14% 31% 36% 8% 1	300
	21st to end	Day	5% 8% 38% 34% 14% 2	330
February	1st to 10th	Day	5% 16% 38% 32% 9%	300
	11th to 20th	Day	7% 17% 43% 25% 8%	300
	21st to end	Day	11% 25% 33% 25% 5%	249
March	1st to 10th	Day	7% 23% 32% 29% 9% 1	371
	11th to 20th	Day	12% 24% 31% 23% 9% 2	500
	21st to end	Day	13% 28% 34% 19% 6% 1	550
April	1st to 10th	Day	12% 22% 39% 19% 7% 1	500
	11th to 20th	Day	12% 28% 39% 14% 5% 1	492
	21st to end	Day	10% 26% 40% 20% 4	500
May	1st to 10th	Day	8% 22% 40% 22% 6% 1	503
	11th to 20th	Day	6% 15% 33% 30% 14% 2	625
	21st to end	Day	6% 12% 31% 36% 14% 1	789
June	1st to 10th	Day	3 5% 26% 39% 24% 2	730
	11th to 20th	Day	2 9% 27% 37% 21% 4	730
	21st to end	Day	5% 7% 23% 34% 26% 5%	730
July	1st to 10th	Day	4 2 16% 39% 33% 6%	721
	11th to 20th	Day	2 1 11% 30% 42% 13%	573
	21st to end	Day	5% 1 9% 31% 41% 14%	575
August	1st to 10th	Day	3 3 13% 38% 33% 10%	527
	11th to 20th	Day	3 3 18% 34% 35% 7%	517
	21st to end	Day	3 2 14% 41% 31% 9%	583
September	1st to 10th	Day	4 3 17% 35% 33% 8%	530
	11th to 20th	Day	5% 4 24% 37% 24% 6%	530
	21st to end	Day	3 7% 21% 32% 29% 8%	342
October	1st to 10th	Day	4 12% 24% 28% 24% 8%	330
	11th to 20th	Day	8% 12% 26% 29% 19% 6%	330
	21st to end	Day	8% 11% 26% 32% 21% 3	363
November	1st to 10th	Day	5% 15% 28% 35% 15% 2	330
	11th to 20th	Day	6% 8% 26% 39% 21% 1	330
	21st to end	Day	9% 12% 33% 29% 16% 2	330
December	1st to 10th	Day	7% 13% 32% 30% 15% 3	330
	11th to 20th	Day	7% 9% 34% 37% 12% 1	330
	21st to end	Day	13% 14% 35% 33% 5% 1	363
January	1st to 10th	Night	5% 5% 33% 42% 13% 1	921
	11th to 20th	Night	7% 5% 35% 40% 11% 2	800
	21st to end	Night	6% 5% 33% 43% 12% 1	880
February	1st to 10th	Night	5% 7% 42% 37% 9%	800
	11th to 20th	Night	8% 8% 43% 33% 7% 1	784
	21st to end	Night	9% 9% 43% 37% 2	660
March	1st to 10th	Night	6% 11% 40% 35% 8% 1	800
	11th to 20th	Night	7% 10% 33% 37% 15%	800
	21st to end	Night	8% 12% 39% 35% 7%	785
April	1st to 10th	Night	6% 11% 46% 31% 6%	600
	11th to 20th	Night	7% 15% 37% 34% 6%	593
	21st to end	Night	5% 9% 43% 37% 7%	600
May	1st to 10th	Night	5% 9% 36% 40% 10%	600
	11th to 20th	Night	8% 4 32% 41% 14% 1	591
	21st to end	Night	4 7% 32% 46% 11%	650
June	1st to 10th	Night	2 2 26% 51% 19%	600
	11th to 20th	Night	2 3 25% 53% 16% 1	600
	21st to end	Night	3 2 18% 50% 26% 1	600
July	1st to 10th	Night	4 1 10% 48% 35% 2	585
	11th to 20th	Night	2 1 6% 42% 46% 3	582
	21st to end	Night	4 1 5% 34% 50% 6%	657
August	1st to 10th	Night	4 1 6% 39% 44% 6%	597
	11th to 20th	Night	4 1 8% 50% 35% 2	594
	21st to end	Night	5% 1 7% 45% 39% 3	660
September	1st to 10th	Night	6% 1 11% 50% 31% 1	600
	11th to 20th	Night	4 1 14% 55% 26% 2	600
	21st to end	Night	6% 3 19% 51% 21%	626
October	1st to 10th	Night	5% 3 24% 49% 18% 1	800
	11th to 20th	Night	5% 4 29% 44% 16% 2	800
	21st to end	Night	5% 4 28% 42% 19% 3	880
November	1st to 10th	Night	4 5% 28% 46% 17% 1	909
	11th to 20th	Night	3 4 31% 46% 14% 1	1050
	21st to end	Night	8% 7% 30% 38% 16% 1	1050
December	1st to 10th	Night	6% 8% 33% 41% 10% 1	1050
	11th to 20th	Night	7% 7% 33% 42% 10%	1050
	21st to end	Night	6% 8% 38% 41% 6% 1	1155

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