Dixon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dixon 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	13% 8% 4 7% 6% 3 5% 5% 5% 7% 37%	78758
	Night	13% 9% 4 7% 5% 3 4 4 5% 6% 39%	81292
Transparency	Day	46% 5% 12% 23% 12% 2	78459
	Night	46% 4 11% 23% 14% 2	81111
Seeing	Day	16% 9% 28% 27% 15% 5%	14886
	Night	17% 9% 31% 31% 12% 1	24953

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	11% 10% 6% 17% 9% 5% 5% 5% 5% 5% 24%	2527
	11th to 20th	Day	12% 10% 5% 11% 11% 4 6% 6% 7% 6% 22%	2534
	21st to end	Day	15% 17% 8% 15% 9% 3 4 4 4 5% 18%	3135
February	1st to 10th	Day	13% 12% 5% 9% 6% 4 5% 5% 4 7% 29%	1710
	11th to 20th	Day	14% 9% 3 6% 6% 4 5% 4 5% 8% 36%	1740
	21st to end	Day	13% 10% 5% 9% 6% 3 5% 4 6% 6% 33%	1570
March	1st to 10th	Day	15% 9% 5% 7% 5% 2 5% 4 6% 7% 36%	1924
	11th to 20th	Day	12% 7% 5% 7% 8% 4 4 5% 5% 7% 36%	2090
	21st to end	Day	21% 11% 3 7% 6% 3 5% 5% 5% 6% 26%	2365
April	1st to 10th	Day	15% 12% 6% 7% 6% 3 4 5% 4 6% 33%	2160
	11th to 20th	Day	16% 10% 3 6% 6% 3 4 5% 5% 6% 35%	2134
	21st to end	Day	21% 9% 3 6% 5% 3 4 4 5% 7% 34%	2160
May	1st to 10th	Day	16% 7% 4 7% 6% 3 5% 5% 7% 8% 31%	2409
	11th to 20th	Day	20% 7% 4 6% 5% 4 5% 5% 5% 7% 33%	2479
	21st to end	Day	14% 7% 3 6% 5% 3 7% 6% 7% 7% 34%	2725
June	1st to 10th	Day	9% 4 2 5% 4 3 5% 6% 7% 9% 44%	2520
	11th to 20th	Day	9% 6% 2 6% 5% 3 5% 5% 6% 7% 47%	2520
	21st to end	Day	11% 5% 3 7% 5% 3 6% 5% 6% 8% 40%	2520
July	1st to 10th	Day	8% 4 2 4 4 3 5% 5% 6% 10% 48%	2520
	11th to 20th	Day	9% 3 2 4 5% 3 5% 5% 8% 10% 46%	2520
	21st to end	Day	6% 4 2 5% 5% 3 5% 5% 8% 10% 48%	2738
August	1st to 10th	Day	6% 5% 2 6% 5% 4 5% 7% 8% 12% 41%	2328
	11th to 20th	Day	9% 6% 3 5% 5% 3 5% 5% 6% 8% 48%	2213
	21st to end	Day	9% 4 2 4 4 3 3 5% 5% 8% 52%	2376
September	1st to 10th	Day	13% 5% 2 5% 5% 4 4 4 5% 8% 47%	2160
	11th to 20th	Day	11% 3 2 3 3 2 5% 4 4 9% 53%	2156
	21st to end	Day	10% 5% 3 6% 4 3 5% 5% 5% 7% 46%	1936
October	1st to 10th	Day	12% 8% 2 5% 5% 3 4 4 4 6% 48%	1800
	11th to 20th	Day	17% 7% 3 5% 5% 3 4 4 4 7% 40%	1800
	21st to end	Day	19% 8% 3 6% 4 3 3 4 4 6% 40%	1908
November	1st to 10th	Day	11% 8% 3 5% 5% 3 5% 4 5% 7% 45%	1672
	11th to 20th	Day	14% 10% 4 6% 6% 3 5% 3 5% 7% 36%	1668
	21st to end	Day	17% 10% 4 7% 5% 3 4 4 4 6% 38%	1520
December	1st to 10th	Day	15% 11% 4 8% 6% 3 4 3 4 7% 33%	1520
	11th to 20th	Day	14% 10% 5% 8% 6% 4 5% 4 5% 8% 31%	1918
	21st to end	Day	22% 19% 8% 11% 7% 2 3 4 3 5% 16%	2783
January	1st to 10th	Night	14% 10% 7% 13% 6% 4 4 4 4 5% 30%	4428
	11th to 20th	Night	12% 15% 7% 11% 7% 3 4 5% 7% 5% 24%	4431
	21st to end	Night	17% 16% 6% 11% 7% 3 4 4 4 5% 23%	4532
February	1st to 10th	Night	14% 11% 5% 6% 6% 4 4 3 5% 6% 34%	2470
	11th to 20th	Night	13% 8% 3 7% 6% 3 4 4 4 5% 41%	2325
	21st to end	Night	14% 11% 4 7% 5% 3 4 4 4 5% 40%	1884
March	1st to 10th	Night	17% 8% 3 6% 6% 3 3 4 4 5% 41%	2272
	11th to 20th	Night	11% 7% 4 7% 5% 4 5% 4 4 8% 40%	2090
	21st to end	Night	21% 10% 4 7% 5% 3 5% 5% 5% 6% 28%	2145
April	1st to 10th	Night	16% 9% 4 6% 5% 2 4 3 4 7% 40%	1800
	11th to 20th	Night	17% 9% 3 6% 5% 3 4 4 5% 6% 40%	1775
	21st to end	Night	16% 9% 3 7% 6% 3 4 4 4 6% 37%	1800
May	1st to 10th	Night	15% 6% 3 5% 6% 3 4 4 5% 8% 39%	1546
	11th to 20th	Night	17% 6% 2 6% 5% 4 4 5% 4 7% 39%	1416
	21st to end	Night	11% 5% 3 5% 6% 3 5% 5% 5% 9% 43%	1551
June	1st to 10th	Night	7% 6% 2 5% 5% 3 4 4 6% 7% 50%	1440
	11th to 20th	Night	10% 5% 2 5% 4 3 4 5% 6% 10% 45%	1440
	21st to end	Night	11% 4 2 4 4 4 5% 5% 6% 8% 48%	1440
July	1st to 10th	Night	7% 3 2 4 4 3 4 5% 6% 10% 52%	1440
	11th to 20th	Night	5% 3 1 4 4 2 4 4 5% 9% 59%	1440
	21st to end	Night	6% 5% 1 3 5% 3 6% 5% 7% 10% 50%	1577
August	1st to 10th	Night	5% 3 2 4 5% 3 5% 5% 6% 9% 54%	1611
	11th to 20th	Night	5% 4 2 5% 4 3 4 4 6% 8% 55%	1686
	21st to end	Night	7% 4 2 4 4 2 4 4 4 7% 58%	1980
September	1st to 10th	Night	10% 5% 2 4 4 2 4 3 5% 7% 54%	1800
	11th to 20th	Night	10% 4 2 3 4 2 4 4 6% 8% 53%	1800
	21st to end	Night	7% 5% 2 4 5% 3 4 4 6% 7% 52%	2008
October	1st to 10th	Night	12% 5% 2 4 4 2 3 3 3 6% 54%	2160
	11th to 20th	Night	15% 7% 2 5% 5% 3 3 3 4 6% 46%	2160
	21st to end	Night	18% 8% 3 6% 5% 3 4 4 4 5% 40%	2448
November	1st to 10th	Night	11% 6% 2 4 4 2 3 3 5% 7% 52%	2406
	11th to 20th	Night	14% 8% 4 7% 5% 3 4 3 5% 7% 40%	2508
	21st to end	Night	17% 8% 3 6% 5% 3 4 3 4 7% 40%	2660
December	1st to 10th	Night	14% 10% 4 8% 6% 3 5% 4 5% 5% 35%	2660
	11th to 20th	Night	14% 11% 5% 8% 5% 3 5% 5% 5% 6% 33%	3279
	21st to end	Night	21% 16% 6% 10% 7% 3 5% 4 4 5% 19%	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	63% 5% 11% 16% 6%	2528
	11th to 20th	Day	62% 3 11% 15% 8%	2534
	21st to end	Day	70% 3 10% 11% 5%	3135
February	1st to 10th	Day	55% 4 13% 20% 7% 1	1710
	11th to 20th	Day	48% 4 12% 24% 11% 1	1749
	21st to end	Day	51% 5% 11% 22% 9% 2	1570
March	1st to 10th	Day	48% 5% 15% 22% 10% 1	1924
	11th to 20th	Day	48% 5% 13% 23% 11% 1	2090
	21st to end	Day	58% 5% 11% 20% 5% 1	2365
April	1st to 10th	Day	52% 4 12% 21% 10%	2160
	11th to 20th	Day	49% 4 10% 23% 12% 1	2134
	21st to end	Day	51% 5% 10% 20% 12% 2	2160
May	1st to 10th	Day	50% 6% 13% 22% 8% 1	2409
	11th to 20th	Day	49% 7% 10% 22% 12%	2483
	21st to end	Day	46% 8% 12% 18% 14% 2	2725
June	1st to 10th	Day	34% 7% 14% 27% 16% 2	2520
	11th to 20th	Day	36% 5% 12% 22% 22% 3	2520
	21st to end	Day	40% 7% 14% 23% 15% 1	2520
July	1st to 10th	Day	31% 6% 15% 30% 15% 3	2451
	11th to 20th	Day	31% 8% 14% 28% 16% 3	2445
	21st to end	Day	29% 8% 17% 27% 16% 2	2586
August	1st to 10th	Day	32% 9% 16% 29% 12% 1	2314
	11th to 20th	Day	35% 6% 13% 27% 18% 2	2213
	21st to end	Day	31% 7% 11% 29% 19% 3	2376
September	1st to 10th	Day	37% 6% 10% 25% 20% 3	2160
	11th to 20th	Day	29% 5% 12% 31% 19% 3	2156
	21st to end	Day	36% 6% 10% 29% 18% 2	1936
October	1st to 10th	Day	39% 3 9% 28% 19% 1	1800
	11th to 20th	Day	44% 3 11% 24% 16% 2	1800
	21st to end	Day	46% 4 12% 24% 13% 2	1908
November	1st to 10th	Day	39% 5% 13% 26% 14% 3	1672
	11th to 20th	Day	48% 4 14% 21% 12% 1	1668
	21st to end	Day	50% 4 14% 22% 9% 1	1520
December	1st to 10th	Day	53% 3 13% 21% 8% 1	1520
	11th to 20th	Day	53% 3 15% 20% 8% 2	1915
	21st to end	Day	73% 4 8% 10% 4	2783
January	1st to 10th	Night	58% 4 11% 18% 9%	4428
	11th to 20th	Night	61% 3 12% 14% 10%	4431
	21st to end	Night	65% 4 9% 16% 6% 1	4532
February	1st to 10th	Night	52% 4 10% 21% 12% 1	2470
	11th to 20th	Night	45% 5% 11% 24% 14% 2	2326
	21st to end	Night	47% 4 10% 23% 13% 3	1884
March	1st to 10th	Night	46% 4 13% 24% 12% 1	2272
	11th to 20th	Night	45% 4 12% 22% 14% 3	2090
	21st to end	Night	57% 5% 11% 18% 8% 1	2145
April	1st to 10th	Night	46% 4 10% 23% 14% 2	1800
	11th to 20th	Night	46% 4 8% 22% 16% 4	1775
	21st to end	Night	48% 5% 11% 21% 13% 3	1800
May	1st to 10th	Night	44% 6% 13% 23% 13% 1	1546
	11th to 20th	Night	45% 6% 11% 22% 14% 1	1417
	21st to end	Night	38% 8% 13% 23% 16% 3	1552
June	1st to 10th	Night	32% 5% 13% 26% 20% 3	1440
	11th to 20th	Night	35% 5% 11% 24% 21% 5%	1440
	21st to end	Night	33% 7% 15% 22% 18% 4	1440
July	1st to 10th	Night	27% 6% 15% 31% 17% 5%	1400
	11th to 20th	Night	23% 5% 13% 35% 20% 3	1392
	21st to end	Night	27% 6% 15% 31% 17% 4	1489
August	1st to 10th	Night	25% 8% 17% 33% 13% 3	1601
	11th to 20th	Night	27% 6% 13% 32% 19% 2	1686
	21st to end	Night	27% 5% 10% 30% 22% 6%	1980
September	1st to 10th	Night	31% 4 12% 24% 25% 3	1800
	11th to 20th	Night	30% 4 11% 31% 20% 4	1800
	21st to end	Night	30% 4 11% 29% 23% 3	2008
October	1st to 10th	Night	34% 4 9% 27% 23% 3	2160
	11th to 20th	Night	40% 3 10% 24% 20% 2	2160
	21st to end	Night	47% 4 10% 21% 16% 2	2448
November	1st to 10th	Night	33% 4 13% 26% 19% 4	2406
	11th to 20th	Night	44% 3 12% 25% 14% 2	2508
	21st to end	Night	47% 4 10% 27% 11% 1	2660
December	1st to 10th	Night	50% 4 13% 23% 9% 1	2660
	11th to 20th	Night	51% 4 12% 24% 8% 1	3281
	21st to end	Night	68% 5% 9% 13% 5%	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	21% 12% 30% 29% 7% 2	270
	11th to 20th	Day	21% 13% 39% 21% 5% 1	270
	21st to end	Day	18% 13% 36% 26% 6% 1	297
February	1st to 10th	Day	20% 13% 38% 25% 4	270
	11th to 20th	Day	21% 18% 31% 22% 6% 1	270
	21st to end	Day	21% 15% 42% 17% 4	225
March	1st to 10th	Day	17% 20% 39% 19% 5%	270
	11th to 20th	Day	19% 17% 33% 21% 8% 2	270
	21st to end	Day	30% 14% 30% 18% 6% 1	395
April	1st to 10th	Day	24% 15% 33% 21% 7% 1	420
	11th to 20th	Day	21% 18% 27% 20% 12% 1	412
	21st to end	Day	25% 11% 32% 22% 10% 1	420
May	1st to 10th	Day	18% 11% 34% 28% 7% 2	542
	11th to 20th	Day	24% 12% 25% 24% 12% 3	625
	21st to end	Day	15% 9% 27% 27% 15% 7%	679
June	1st to 10th	Day	8% 5% 23% 36% 22% 6%	630
	11th to 20th	Day	11% 4 30% 32% 19% 4	630
	21st to end	Day	12% 7% 28% 31% 16% 6%	630
July	1st to 10th	Day	9% 3 13% 33% 26% 15%	621
	11th to 20th	Day	11% 3 22% 34% 21% 9%	618
	21st to end	Day	6% 2 22% 37% 27% 6%	684
August	1st to 10th	Day	7% 2 20% 33% 28% 10%	626
	11th to 20th	Day	11% 4 17% 29% 28% 11%	527
	21st to end	Day	9% 3 19% 32% 27% 11%	495
September	1st to 10th	Day	16% 7% 20% 27% 23% 8%	450
	11th to 20th	Day	9% 3 18% 35% 26% 10%	450
	21st to end	Day	12% 7% 29% 25% 20% 7%	406
October	1st to 10th	Day	19% 8% 27% 26% 14% 5%	270
	11th to 20th	Day	20% 20% 33% 16% 10%	270
	21st to end	Day	30% 13% 28% 20% 6% 2	297
November	1st to 10th	Day	14% 11% 40% 20% 11% 4	270
	11th to 20th	Day	19% 16% 34% 21% 7% 2	270
	21st to end	Day	24% 12% 34% 23% 6%	270
December	1st to 10th	Day	16% 13% 38% 24% 7% 2	270
	11th to 20th	Day	17% 13% 36% 25% 9%	270
	21st to end	Day	26% 15% 36% 20% 3	297
January	1st to 10th	Night	16% 13% 37% 26% 8%	950
	11th to 20th	Night	18% 12% 38% 26% 6% 1	950
	21st to end	Night	19% 11% 36% 27% 7%	1045
February	1st to 10th	Night	20% 11% 37% 26% 5%	950
	11th to 20th	Night	18% 12% 37% 28% 5%	851
	21st to end	Night	20% 12% 42% 22% 4 1	628
March	1st to 10th	Night	22% 11% 36% 24% 7% 1	752
	11th to 20th	Night	16% 11% 34% 32% 6%	570
	21st to end	Night	25% 11% 36% 23% 4 1	615
April	1st to 10th	Night	21% 12% 37% 25% 4	540
	11th to 20th	Night	22% 12% 30% 28% 8% 1	533
	21st to end	Night	20% 10% 32% 30% 8%	540
May	1st to 10th	Night	18% 7% 35% 31% 7% 1	540
	11th to 20th	Night	19% 8% 27% 33% 13%	531
	21st to end	Night	12% 3 29% 35% 18% 2	584
June	1st to 10th	Night	9% 3 23% 46% 17% 1	540
	11th to 20th	Night	11% 4 29% 41% 14% 1	540
	21st to end	Night	11% 4 27% 39% 18% 1	540
July	1st to 10th	Night	8% 2 12% 40% 32% 5%	525
	11th to 20th	Night	6% 2 20% 44% 25% 3	522
	21st to end	Night	7% 1 17% 44% 30% 1	591
August	1st to 10th	Night	5% 2 14% 43% 33% 3	537
	11th to 20th	Night	6% 2 12% 43% 31% 6%	534
	21st to end	Night	9% 2 13% 46% 26% 4	594
September	1st to 10th	Night	13% 3 18% 39% 24% 4	540
	11th to 20th	Night	12% 1 20% 35% 26% 6%	540
	21st to end	Night	10% 6% 25% 35% 22% 2	706
October	1st to 10th	Night	14% 6% 28% 32% 20% 1	720
	11th to 20th	Night	18% 12% 31% 28% 11%	720
	21st to end	Night	23% 11% 33% 27% 7% 1	792
November	1st to 10th	Night	15% 9% 40% 26% 10%	740
	11th to 20th	Night	19% 12% 37% 25% 7%	798
	21st to end	Night	21% 12% 34% 26% 7%	950
December	1st to 10th	Night	20% 11% 38% 24% 6%	950
	11th to 20th	Night	23% 8% 33% 30% 5%	950
	21st to end	Night	27% 13% 33% 24% 3	1045

Page generated at 2024-03-24 22:37:00. Version ac07

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