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 2024-11-04.

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% 8% 3 8% 5% 4 5% 4 6% 7% 38%	101470
	Night	13% 9% 3 8% 5% 4 4 3 5% 6% 40%	97642
Transparency	Day	43% 5% 12% 24% 14% 2	105038
	Night	43% 5% 11% 23% 15% 2	102201
Seeing	Day	16% 9% 28% 27% 15% 5%	15837
	Night	17% 9% 31% 31% 12% 1	25663

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% 11% 6% 18% 7% 6% 5% 3 5% 5% 23%	2527
	11th to 20th	Day	11% 11% 4 13% 9% 6% 5% 4 7% 6% 22%	2534
	21st to end	Day	14% 17% 7% 16% 8% 4 4 3 4 5% 18%	3135
February	1st to 10th	Day	13% 13% 5% 9% 6% 5% 4 4 5% 7% 29%	1710
	11th to 20th	Day	14% 10% 2 7% 5% 5% 4 3 5% 8% 36%	1740
	21st to end	Day	13% 11% 4 10% 5% 4 4 4 6% 6% 33%	1570
March	1st to 10th	Day	15% 11% 3 7% 3 3 4 3 5% 6% 40%	3170
	11th to 20th	Day	10% 5% 3 5% 6% 4 4 4 6% 7% 45%	3480
	21st to end	Day	21% 13% 4 11% 6% 5% 5% 4 6% 5% 22%	4005
April	1st to 10th	Day	16% 13% 4 7% 5% 4 4 3 5% 6% 33%	2280
	11th to 20th	Day	16% 10% 3 7% 5% 4 5% 4 4 6% 35%	2254
	21st to end	Day	21% 9% 3 7% 4 4 4 3 5% 6% 34%	2280
May	1st to 10th	Day	15% 7% 3 8% 5% 4 4 4 6% 8% 35%	4221
	11th to 20th	Day	16% 7% 3 6% 4 4 5% 3 5% 7% 40%	4399
	21st to end	Day	12% 6% 3 6% 4 4 5% 4 6% 7% 42%	4824
June	1st to 10th	Day	9% 5% 2 6% 4 4 5% 5% 8% 9% 44%	2660
	11th to 20th	Day	9% 6% 2 6% 5% 4 5% 4 6% 7% 46%	2660
	21st to end	Day	11% 6% 3 8% 5% 5% 5% 5% 6% 8% 40%	2660
July	1st to 10th	Day	9% 8% 3 8% 4 6% 5% 5% 7% 9% 35%	4440
	11th to 20th	Day	6% 4 1 5% 4 4 4 4 7% 9% 52%	4440
	21st to end	Day	6% 5% 2 7% 5% 5% 5% 5% 9% 10% 41%	4795
August	1st to 10th	Day	7% 6% 2 6% 4 4 5% 4 8% 12% 43%	4104
	11th to 20th	Day	10% 6% 2 5% 4 5% 5% 4 7% 9% 43%	3883
	21st to end	Day	8% 5% 2 6% 4 4 4 3 6% 9% 50%	4180
September	1st to 10th	Day	12% 5% 1 5% 4 5% 3 3 4 8% 49%	2280
	11th to 20th	Day	10% 4 2 4 3 3 5% 3 4 9% 53%	2275
	21st to end	Day	10% 6% 2 6% 4 4 5% 4 5% 7% 47%	2043
October	1st to 10th	Day	11% 8% 2 5% 4 3 4 3 4 6% 50%	1900
	11th to 20th	Day	16% 8% 2 6% 4 4 4 3 4 7% 42%	1900
	21st to end	Day	18% 9% 3 6% 3 3 4 3 4 6% 41%	2013
November	1st to 10th	Day	11% 9% 3 5% 4 4 4 3 5% 7% 44%	1699
	11th to 20th	Day	14% 12% 4 7% 5% 4 4 3 5% 7% 35%	1668
	21st to end	Day	16% 11% 3 8% 4 4 4 3 4 6% 38%	1520
December	1st to 10th	Day	15% 12% 4 9% 5% 4 4 3 4 7% 33%	1520
	11th to 20th	Day	14% 10% 6% 9% 5% 6% 5% 3 5% 7% 31%	1918
	21st to end	Day	22% 19% 8% 12% 6% 3 4 3 4 4 16%	2783
January	1st to 10th	Night	13% 11% 7% 14% 5% 5% 4 3 4 5% 30%	4428
	11th to 20th	Night	12% 16% 6% 12% 6% 5% 4 4 7% 5% 24%	4431
	21st to end	Night	17% 16% 6% 12% 6% 4 4 3 4 4 23%	4532
February	1st to 10th	Night	14% 12% 5% 7% 5% 5% 4 3 5% 6% 34%	2470
	11th to 20th	Night	12% 9% 2 8% 5% 4 4 3 4 5% 41%	2325
	21st to end	Night	14% 11% 3 8% 4 4 4 3 4 5% 39%	1884
March	1st to 10th	Night	19% 8% 2 6% 4 3 4 3 4 4 43%	3712
	11th to 20th	Night	10% 6% 2 7% 4 4 4 3 4 7% 48%	3480
	21st to end	Night	23% 13% 5% 11% 5% 4 4 3 5% 5% 22%	3626
April	1st to 10th	Night	17% 10% 3 6% 4 3 4 3 4 6% 40%	1900
	11th to 20th	Night	16% 10% 2 7% 3 3 3 3 5% 6% 41%	1875
	21st to end	Night	16% 9% 3 7% 6% 3 4 3 4 6% 38%	1900
May	1st to 10th	Night	18% 8% 3 7% 6% 3 4 4 6% 6% 35%	2676
	11th to 20th	Night	13% 6% 2 7% 5% 5% 5% 4 5% 7% 42%	2506
	21st to end	Night	7% 5% 2 5% 5% 4 5% 4 6% 9% 48%	2743
June	1st to 10th	Night	7% 6% 2 7% 4 4 4 4 7% 7% 49%	1520
	11th to 20th	Night	9% 5% 2 6% 4 4 4 4 7% 9% 45%	1520
	21st to end	Night	10% 5% 2 5% 4 5% 5% 4 6% 8% 47%	1520
July	1st to 10th	Night	12% 6% 3 8% 5% 5% 5% 4 6% 8% 40%	2530
	11th to 20th	Night	4 3 1 5% 4 3 3 3 5% 9% 59%	2530
	21st to end	Night	5% 5% 2 5% 5% 5% 5% 5% 7% 10% 47%	2765
August	1st to 10th	Night	5% 3 2 5% 4 4 4 4 6% 9% 55%	2836
	11th to 20th	Night	6% 5% 2 6% 3 4 4 4 6% 8% 54%	2949
	21st to end	Night	7% 4 2 5% 4 4 4 3 5% 8% 53%	3476
September	1st to 10th	Night	10% 5% 2 4 3 3 3 2 5% 7% 56%	1900
	11th to 20th	Night	10% 4 2 3 4 4 4 4 6% 8% 52%	1900
	21st to end	Night	7% 5% 2 5% 5% 4 3 3 6% 7% 52%	2121
October	1st to 10th	Night	11% 5% 2 5% 4 3 3 3 3 6% 54%	2280
	11th to 20th	Night	14% 7% 2 6% 4 4 3 3 4 6% 48%	2280
	21st to end	Night	18% 8% 3 7% 4 4 4 3 4 5% 39%	2584
November	1st to 10th	Night	11% 6% 2 5% 4 3 3 3 5% 6% 52%	2452
	11th to 20th	Night	14% 9% 3 8% 4 4 4 3 5% 7% 40%	2508
	21st to end	Night	17% 9% 3 6% 5% 3 4 3 4 6% 40%	2660
December	1st to 10th	Night	14% 11% 4 9% 5% 5% 4 3 6% 5% 35%	2660
	11th to 20th	Night	14% 12% 4 9% 4 4 4 3 6% 6% 33%	3279
	21st to end	Night	20% 16% 6% 11% 5% 5% 5% 3 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	45% 5% 11% 23% 14% 1	3170
	11th to 20th	Day	38% 4 12% 29% 15% 1	3480
	21st to end	Day	62% 4 15% 15% 3 1	4005
April	1st to 10th	Day	52% 4 12% 22% 10%	2280
	11th to 20th	Day	49% 4 10% 23% 13% 2	2254
	21st to end	Day	50% 5% 10% 20% 13% 2	2280
May	1st to 10th	Day	46% 5% 12% 22% 15% 1	4259
	11th to 20th	Day	43% 6% 10% 28% 12%	4403
	21st to end	Day	39% 6% 10% 25% 18% 2	4837
June	1st to 10th	Day	34% 7% 14% 26% 17% 2	2660
	11th to 20th	Day	36% 5% 12% 22% 22% 3	2660
	21st to end	Day	40% 7% 13% 23% 14% 2	2660
July	1st to 10th	Day	43% 6% 13% 26% 10% 2	4371
	11th to 20th	Day	27% 7% 15% 31% 18% 2	4365
	21st to end	Day	33% 9% 18% 20% 18% 2	4644
August	1st to 10th	Day	31% 7% 18% 29% 14% 1	4090
	11th to 20th	Day	36% 6% 15% 26% 16% 1	3922
	21st to end	Day	31% 6% 13% 31% 16% 2	4179
September	1st to 10th	Day	35% 5% 9% 25% 22% 3	2280
	11th to 20th	Day	29% 5% 12% 31% 20% 3	2275
	21st to end	Day	35% 6% 10% 29% 18% 2	2043
October	1st to 10th	Day	24% 2 5% 31% 36% 1	3160
	11th to 20th	Day	28% 3 12% 23% 30% 4	3140
	21st to end	Day	40% 3 9% 29% 14% 4	3290
November	1st to 10th	Day	39% 5% 13% 26% 14% 3	1699
	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 11% 24% 14% 2	3712
	11th to 20th	Night	35% 5% 10% 30% 17% 2	3480
	21st to end	Night	64% 5% 12% 14% 5% 1	3626
April	1st to 10th	Night	46% 4 10% 24% 14% 2	1900
	11th to 20th	Night	45% 4 8% 22% 17% 4	1875
	21st to end	Night	47% 5% 11% 21% 14% 3	1900
May	1st to 10th	Night	48% 6% 11% 19% 16% 2	2703
	11th to 20th	Night	41% 6% 13% 25% 14% 1	2507
	21st to end	Night	31% 7% 11% 29% 21% 2	2751
June	1st to 10th	Night	32% 5% 13% 26% 20% 3	1520
	11th to 20th	Night	34% 5% 11% 24% 21% 5%	1520
	21st to end	Night	35% 7% 15% 22% 18% 4	1520
July	1st to 10th	Night	42% 6% 13% 24% 13% 3	2490
	11th to 20th	Night	22% 6% 15% 34% 21% 2	2482
	21st to end	Night	30% 8% 18% 23% 18% 3	2677
August	1st to 10th	Night	25% 6% 17% 33% 17% 2	2826
	11th to 20th	Night	28% 6% 17% 31% 17% 1	2976
	21st to end	Night	29% 6% 12% 30% 18% 5%	3476
September	1st to 10th	Night	29% 4 11% 25% 27% 3	1900
	11th to 20th	Night	31% 4 10% 30% 20% 4	1900
	21st to end	Night	30% 4 10% 29% 23% 3	2121
October	1st to 10th	Night	24% 3 6% 31% 34% 3	3800
	11th to 20th	Night	28% 3 9% 23% 33% 4	3779
	21st to end	Night	46% 3 8% 22% 18% 4	4244
November	1st to 10th	Night	34% 4 13% 26% 19% 4	2452
	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% 31% 18% 6% 1	411
April	1st to 10th	Day	25% 15% 33% 20% 7% 1	460
	11th to 20th	Day	21% 19% 27% 20% 11% 1	452
	21st to end	Day	25% 12% 33% 21% 9% 1	460
May	1st to 10th	Day	17% 11% 34% 28% 7% 2	589
	11th to 20th	Day	23% 11% 26% 25% 13% 3	675
	21st to end	Day	14% 10% 27% 28% 14% 7%	734
June	1st to 10th	Day	8% 7% 24% 35% 21% 5%	680
	11th to 20th	Day	10% 5% 31% 32% 18% 3	680
	21st to end	Day	13% 7% 30% 30% 15% 5%	680
July	1st to 10th	Day	10% 4 15% 32% 26% 14%	671
	11th to 20th	Day	11% 3 22% 34% 21% 10%	668
	21st to end	Day	6% 2 21% 37% 27% 7%	739
August	1st to 10th	Day	8% 2 20% 34% 27% 9%	676
	11th to 20th	Day	12% 4 17% 30% 26% 10%	572
	21st to end	Day	9% 3 17% 32% 28% 10%	539
September	1st to 10th	Day	15% 7% 19% 28% 24% 8%	490
	11th to 20th	Day	8% 3 17% 36% 26% 10%	490
	21st to end	Day	12% 7% 30% 26% 19% 7%	443
October	1st to 10th	Day	17% 9% 27% 26% 16% 5%	300
	11th to 20th	Day	19% 18% 32% 19% 11%	300
	21st to end	Day	30% 13% 30% 21% 5% 2	330
November	1st to 10th	Day	15% 11% 39% 20% 11% 4	279
	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% 10% 37% 23% 4 1	627
April	1st to 10th	Night	21% 13% 37% 25% 4	570
	11th to 20th	Night	21% 13% 31% 28% 7% 1	563
	21st to end	Night	20% 10% 32% 30% 8%	570
May	1st to 10th	Night	18% 8% 35% 32% 7% 1	570
	11th to 20th	Night	18% 8% 28% 34% 13%	561
	21st to end	Night	12% 3 30% 36% 18% 1	617
June	1st to 10th	Night	10% 4 24% 46% 16% 1	570
	11th to 20th	Night	11% 4 31% 40% 14% 1	570
	21st to end	Night	12% 4 28% 38% 17% 1	570
July	1st to 10th	Night	10% 2 13% 40% 30% 4	555
	11th to 20th	Night	6% 2 20% 44% 25% 4	552
	21st to end	Night	7% 1 16% 44% 30% 1	624
August	1st to 10th	Night	5% 2 15% 43% 32% 2	567
	11th to 20th	Night	6% 2 13% 44% 30% 5%	564
	21st to end	Night	9% 2 13% 47% 26% 4	627
September	1st to 10th	Night	12% 2 18% 38% 25% 4	570
	11th to 20th	Night	12% 2 20% 36% 26% 5%	570
	21st to end	Night	10% 6% 26% 35% 22% 2	746
October	1st to 10th	Night	14% 6% 27% 33% 20% 1	760
	11th to 20th	Night	18% 12% 31% 28% 11%	760
	21st to end	Night	22% 11% 32% 27% 7%	836
November	1st to 10th	Night	15% 9% 40% 26% 10%	755
	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 2024-11-01 21:47:44. Version ac07

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