Benton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Benton clear sky chart from 2005-11-06 to 2024-11-05.

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% 7% 3 7% 5% 5% 5% 4 6% 7% 39%	100955
	Night	13% 8% 3 6% 4 4 4 4 5% 7% 41%	98056
Transparency	Day	41% 8% 11% 20% 16% 4	104750
	Night	39% 7% 11% 20% 17% 5%	102399
Seeing	Day	17% 12% 23% 23% 18% 8%	14786
	Night	16% 10% 22% 29% 19% 3	24797

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	17% 12% 4 7% 5% 4 4 3 5% 6% 34%	2836
	11th to 20th	Day	16% 10% 6% 9% 4 5% 3 2 4 4 36%	2840
	21st to end	Day	21% 14% 3 6% 4 3 3 2 4 6% 35%	3223
February	1st to 10th	Day	17% 11% 4 7% 4 4 4 3 5% 5% 34%	1900
	11th to 20th	Day	21% 10% 3 8% 5% 4 3 3 5% 6% 33%	1848
	21st to end	Day	21% 10% 3 8% 4 3 3 3 5% 5% 35%	1570
March	1st to 10th	Day	23% 9% 3 7% 4 4 4 3 5% 7% 32%	3171
	11th to 20th	Day	14% 7% 2 6% 4 4 3 2 4 5% 47%	3480
	21st to end	Day	17% 9% 3 7% 5% 4 4 3 5% 6% 38%	3815
April	1st to 10th	Day	11% 7% 2 6% 4 5% 6% 4 7% 7% 41%	2201
	11th to 20th	Day	14% 7% 3 7% 4 3 4 3 5% 7% 44%	2254
	21st to end	Day	12% 7% 3 6% 4 5% 5% 3 5% 7% 42%	2432
May	1st to 10th	Day	12% 7% 2 7% 5% 5% 6% 4 6% 7% 38%	4082
	11th to 20th	Day	16% 8% 3 8% 5% 6% 5% 4 5% 7% 34%	4081
	21st to end	Day	9% 6% 2 7% 5% 5% 5% 5% 7% 9% 41%	4476
June	1st to 10th	Day	8% 6% 2 7% 5% 5% 7% 5% 8% 9% 37%	2470
	11th to 20th	Day	5% 5% 2 6% 5% 6% 6% 6% 8% 10% 41%	2470
	21st to end	Day	7% 5% 2 7% 6% 5% 6% 6% 8% 10% 38%	2470
July	1st to 10th	Day	6% 5% 2 7% 6% 7% 7% 6% 9% 12% 33%	4120
	11th to 20th	Day	8% 6% 3 7% 6% 5% 6% 5% 7% 10% 36%	4120
	21st to end	Day	13% 10% 5% 12% 7% 7% 7% 6% 7% 7% 18%	4466
August	1st to 10th	Day	6% 4 2 6% 5% 6% 7% 5% 8% 12% 41%	4104
	11th to 20th	Day	7% 5% 2 6% 5% 6% 5% 6% 7% 11% 41%	3800
	21st to end	Day	7% 4 2 6% 4 5% 6% 5% 6% 8% 48%	4180
September	1st to 10th	Day	10% 6% 2 8% 5% 4 5% 5% 6% 9% 40%	2132
	11th to 20th	Day	14% 6% 3 7% 5% 4 4 5% 5% 7% 40%	2090
	21st to end	Day	13% 5% 2 6% 4 4 5% 3 5% 6% 47%	2090
October	1st to 10th	Day	11% 4 2 4 4 4 4 3 5% 6% 54%	2090
	11th to 20th	Day	11% 6% 2 4 3 3 3 3 3 6% 56%	1990
	21st to end	Day	13% 6% 1 4 3 3 3 3 5% 6% 52%	2039
November	1st to 10th	Day	13% 5% 2 4 3 4 4 3 4 6% 55%	1708
	11th to 20th	Day	12% 7% 2 5% 3 4 3 3 6% 6% 48%	1710
	21st to end	Day	16% 7% 2 4 4 3 5% 3 5% 7% 45%	1710
December	1st to 10th	Day	18% 11% 3 7% 5% 4 4 4 5% 5% 34%	1710
	11th to 20th	Day	16% 11% 3 7% 5% 4 4 3 5% 4 37%	2153
	21st to end	Day	16% 14% 4 8% 4 4 4 3 5% 7% 32%	3124
January	1st to 10th	Night	17% 12% 3 8% 5% 4 3 2 4 5% 37%	4109
	11th to 20th	Night	19% 10% 4 6% 5% 3 3 3 4 5% 38%	4120
	21st to end	Night	20% 14% 3 7% 3 3 3 3 3 5% 34%	4432
February	1st to 10th	Night	16% 9% 3 7% 4 3 3 3 5% 6% 40%	2280
	11th to 20th	Night	21% 10% 3 6% 5% 4 4 4 3 4 36%	2218
	21st to end	Night	22% 10% 3 6% 5% 4 4 3 5% 5% 33%	1884
March	1st to 10th	Night	22% 11% 3 6% 4 4 4 3 5% 6% 32%	3680
	11th to 20th	Night	13% 6% 2 5% 3 3 4 4 6% 8% 47%	3480
	21st to end	Night	14% 9% 3 7% 4 4 5% 3 4 6% 40%	3817
April	1st to 10th	Night	13% 5% 2 5% 4 4 4 4 6% 8% 47%	1994
	11th to 20th	Night	13% 7% 2 5% 3 4 3 3 5% 7% 48%	1875
	21st to end	Night	13% 5% 2 6% 4 4 3 4 6% 7% 46%	1746
May	1st to 10th	Night	11% 7% 2 7% 6% 5% 5% 4 7% 8% 38%	2813
	11th to 20th	Night	16% 8% 3 7% 5% 4 4 4 5% 7% 37%	2812
	21st to end	Night	7% 6% 2 6% 5% 5% 5% 5% 7% 11% 41%	3079
June	1st to 10th	Night	6% 6% 3 7% 6% 6% 6% 5% 7% 11% 38%	1710
	11th to 20th	Night	4 3 1 5% 5% 5% 5% 4 8% 12% 48%	1710
	21st to end	Night	4 5% 2 7% 4 5% 5% 4 8% 11% 45%	1710
July	1st to 10th	Night	9% 6% 2 7% 6% 6% 6% 5% 7% 11% 35%	2840
	11th to 20th	Night	9% 5% 2 5% 5% 5% 5% 5% 7% 11% 42%	2840
	21st to end	Night	13% 10% 3 8% 7% 6% 7% 5% 8% 9% 23%	3087
August	1st to 10th	Night	6% 4 2 5% 5% 4 5% 4 8% 11% 45%	2825
	11th to 20th	Night	8% 5% 2 6% 4 5% 4 4 6% 10% 45%	3025
	21st to end	Night	6% 4 2 5% 4 5% 5% 5% 7% 10% 49%	3476
September	1st to 10th	Night	10% 5% 2 7% 6% 4 6% 5% 6% 7% 41%	2028
	11th to 20th	Night	11% 6% 2 7% 5% 4 5% 3 6% 7% 42%	2090
	21st to end	Night	10% 6% 3 5% 4 4 4 3 5% 7% 49%	2090
October	1st to 10th	Night	11% 4 2 4 3 3 3 2 4 6% 58%	2090
	11th to 20th	Night	14% 4 1 5% 3 4 4 2 4 4 54%	2187
	21st to end	Night	13% 6% 2 4 2 3 3 3 5% 5% 54%	2555
November	1st to 10th	Night	12% 7% 2 4 4 3 2 3 5% 5% 53%	2470
	11th to 20th	Night	13% 7% 2 5% 4 2 3 4 4 7% 49%	2470
	21st to end	Night	14% 8% 3 5% 4 4 4 4 4 6% 44%	2470
December	1st to 10th	Night	19% 10% 3 7% 4 4 4 4 6% 6% 34%	2470
	11th to 20th	Night	17% 10% 3 7% 3 3 3 3 4 6% 41%	3042
	21st to end	Night	16% 11% 4 9% 5% 5% 5% 4 5% 7% 29%	4532

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	50% 5% 7% 14% 23% 2	2837
	11th to 20th	Day	51% 6% 6% 14% 21% 3	2840
	21st to end	Day	52% 4 7% 17% 18% 2	3223
February	1st to 10th	Day	51% 5% 7% 17% 17% 3	1900
	11th to 20th	Day	53% 5% 6% 17% 16% 4	1858
	21st to end	Day	52% 5% 7% 12% 19% 5%	1570
March	1st to 10th	Day	50% 5% 10% 14% 13% 8%	3171
	11th to 20th	Day	40% 4 7% 21% 21% 8%	3480
	21st to end	Day	47% 6% 9% 22% 14% 3	3815
April	1st to 10th	Day	39% 9% 10% 21% 17% 4	2201
	11th to 20th	Day	40% 6% 8% 18% 24% 5%	2254
	21st to end	Day	41% 7% 10% 26% 14% 2	2432
May	1st to 10th	Day	42% 11% 12% 21% 13% 2	4120
	11th to 20th	Day	48% 10% 10% 22% 8% 1	4085
	21st to end	Day	37% 11% 11% 23% 16% 1	4489
June	1st to 10th	Day	40% 12% 16% 22% 9% 1	2470
	11th to 20th	Day	35% 12% 17% 23% 12% 2	2470
	21st to end	Day	37% 13% 16% 18% 13% 3	2470
July	1st to 10th	Day	37% 15% 21% 18% 8% 1	4055
	11th to 20th	Day	40% 12% 20% 20% 7% 2	4051
	21st to end	Day	61% 11% 12% 11% 4	4324
August	1st to 10th	Day	32% 12% 17% 31% 9%	4091
	11th to 20th	Day	34% 10% 19% 24% 12% 1	3838
	21st to end	Day	32% 10% 12% 29% 15% 2	4179
September	1st to 10th	Day	40% 11% 13% 15% 16% 5%	2132
	11th to 20th	Day	43% 9% 11% 19% 17% 1	2090
	21st to end	Day	37% 8% 13% 16% 20% 6%	2090
October	1st to 10th	Day	26% 6% 7% 16% 34% 11%	3480
	11th to 20th	Day	22% 4 6% 21% 31% 16%	3282
	21st to end	Day	24% 5% 8% 28% 26% 10%	3341
November	1st to 10th	Day	32% 5% 8% 18% 29% 7%	1708
	11th to 20th	Day	36% 5% 7% 20% 25% 7%	1710
	21st to end	Day	40% 5% 7% 19% 24% 4	1710
December	1st to 10th	Day	51% 7% 6% 17% 16% 3	1710
	11th to 20th	Day	48% 4 8% 15% 20% 4	2150
	21st to end	Day	50% 5% 9% 20% 14% 2	3124
January	1st to 10th	Night	49% 5% 7% 15% 21% 3	4109
	11th to 20th	Night	48% 7% 7% 14% 16% 9%	4120
	21st to end	Night	54% 5% 7% 13% 18% 4	4432
February	1st to 10th	Night	46% 5% 9% 18% 19% 4	2280
	11th to 20th	Night	53% 5% 6% 15% 15% 5%	2219
	21st to end	Night	52% 5% 7% 15% 16% 5%	1884
March	1st to 10th	Night	53% 6% 10% 13% 14% 5%	3680
	11th to 20th	Night	35% 6% 9% 22% 19% 9%	3480
	21st to end	Night	45% 5% 9% 22% 16% 3	3817
April	1st to 10th	Night	34% 7% 12% 21% 22% 4	1994
	11th to 20th	Night	35% 5% 9% 22% 22% 7%	1875
	21st to end	Night	36% 6% 12% 29% 16% 1	1746
May	1st to 10th	Night	39% 12% 15% 21% 12% 1	2840
	11th to 20th	Night	45% 10% 12% 23% 10%	2813
	21st to end	Night	32% 12% 15% 26% 14% 1	3087
June	1st to 10th	Night	37% 12% 17% 21% 12% 2	1710
	11th to 20th	Night	26% 12% 21% 28% 12% 2	1710
	21st to end	Night	31% 10% 21% 20% 14% 4	1710
July	1st to 10th	Night	39% 12% 21% 21% 6% 1	2795
	11th to 20th	Night	34% 9% 24% 24% 6% 3	2786
	21st to end	Night	54% 12% 15% 14% 5% 1	2988
August	1st to 10th	Night	30% 10% 17% 32% 11%	2814
	11th to 20th	Night	32% 9% 22% 25% 11% 1	3053
	21st to end	Night	27% 10% 16% 31% 15% 1	3476
September	1st to 10th	Night	37% 10% 15% 18% 14% 5%	2028
	11th to 20th	Night	38% 9% 15% 18% 19% 1	2090
	21st to end	Night	34% 8% 11% 20% 21% 6%	2090
October	1st to 10th	Night	22% 6% 9% 19% 29% 14%	3480
	11th to 20th	Night	23% 3 6% 18% 33% 17%	3634
	21st to end	Night	22% 4 4 28% 29% 12%	4203
November	1st to 10th	Night	34% 5% 8% 21% 23% 9%	2470
	11th to 20th	Night	36% 5% 6% 20% 24% 9%	2470
	21st to end	Night	42% 5% 6% 21% 23% 4	2470
December	1st to 10th	Night	51% 7% 8% 16% 15% 3	2470
	11th to 20th	Night	45% 6% 7% 13% 26% 3	3044
	21st to end	Night	53% 5% 8% 20% 13% 1	4532

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	27% 24% 33% 13% 3	270
	11th to 20th	Day	28% 26% 29% 13% 4	270
	21st to end	Day	23% 29% 37% 9% 2	297
February	1st to 10th	Day	27% 23% 34% 13% 4	270
	11th to 20th	Day	38% 27% 26% 10%	270
	21st to end	Day	40% 23% 30% 7%	225
March	1st to 10th	Day	28% 24% 27% 15% 6%	295
	11th to 20th	Day	25% 22% 31% 17% 6%	460
	21st to end	Day	25% 19% 34% 16% 6%	506
April	1st to 10th	Day	20% 19% 28% 20% 12% 1	460
	11th to 20th	Day	19% 19% 29% 21% 11% 1	452
	21st to end	Day	19% 14% 30% 24% 11% 2	460
May	1st to 10th	Day	15% 12% 34% 22% 12% 6%	463
	11th to 20th	Day	14% 7% 26% 29% 16% 8%	487
	21st to end	Day	11% 8% 21% 29% 19% 13%	529
June	1st to 10th	Day	9% 6% 22% 29% 22% 11%	490
	11th to 20th	Day	6% 4 15% 32% 27% 16%	490
	21st to end	Day	8% 4 20% 30% 23% 15%	490
July	1st to 10th	Day	9% 4 15% 25% 28% 19%	485
	11th to 20th	Day	9% 3 10% 25% 33% 19%	484
	21st to end	Day	12% 4 9% 25% 31% 19%	532
August	1st to 10th	Day	10% 3 15% 26% 26% 19%	486
	11th to 20th	Day	10% 3 17% 30% 27% 13%	479
	21st to end	Day	13% 3 10% 22% 31% 19%	539
September	1st to 10th	Day	10% 3 13% 30% 28% 16%	490
	11th to 20th	Day	16% 5% 12% 24% 30% 14%	490
	21st to end	Day	14% 7% 13% 29% 30% 6%	490
October	1st to 10th	Day	12% 7% 18% 32% 23% 7%	490
	11th to 20th	Day	12% 13% 25% 29% 19% 2	490
	21st to end	Day	18% 10% 24% 28% 18% 3	488
November	1st to 10th	Day	22% 10% 27% 26% 14% 2	282
	11th to 20th	Day	17% 15% 36% 25% 7%	270
	21st to end	Day	16% 17% 37% 21% 9% 1	270
December	1st to 10th	Day	26% 21% 31% 17% 4	270
	11th to 20th	Day	23% 19% 31% 20% 6% 1	270
	21st to end	Day	25% 21% 34% 15% 4	297
January	1st to 10th	Night	23% 21% 28% 23% 4	760
	11th to 20th	Night	25% 17% 30% 23% 5%	760
	21st to end	Night	22% 16% 33% 26% 3	836
February	1st to 10th	Night	20% 15% 34% 26% 5%	760
	11th to 20th	Night	27% 20% 31% 20% 2	743
	21st to end	Night	29% 21% 30% 17% 2	628
March	1st to 10th	Night	20% 15% 34% 26% 5%	760
	11th to 20th	Night	21% 18% 31% 22% 7% 1	760
	21st to end	Night	20% 14% 32% 26% 8%	836
April	1st to 10th	Night	14% 18% 29% 29% 9%	664
	11th to 20th	Night	16% 13% 32% 28% 10% 1	563
	21st to end	Night	14% 9% 28% 35% 13% 1	570
May	1st to 10th	Night	11% 7% 28% 34% 18% 2	570
	11th to 20th	Night	14% 6% 20% 31% 24% 4	561
	21st to end	Night	10% 3 14% 36% 31% 6%	617
June	1st to 10th	Night	7% 4 15% 37% 33% 4	570
	11th to 20th	Night	4 2 12% 34% 36% 11%	570
	21st to end	Night	7% 1 11% 34% 38% 8%	570
July	1st to 10th	Night	11% 3 9% 28% 40% 9%	555
	11th to 20th	Night	9% 2 6% 27% 45% 11%	552
	21st to end	Night	9% 2 9% 26% 45% 10%	624
August	1st to 10th	Night	9% 2 6% 26% 48% 9%	567
	11th to 20th	Night	9% 3 8% 34% 40% 6%	564
	21st to end	Night	11% 3 7% 28% 41% 10%	627
September	1st to 10th	Night	11% 3 10% 31% 39% 6%	698
	11th to 20th	Night	13% 3 12% 33% 34% 5%	760
	21st to end	Night	14% 3 15% 34% 32% 2	760
October	1st to 10th	Night	13% 5% 19% 29% 28% 6%	760
	11th to 20th	Night	15% 6% 25% 32% 20% 2	760
	21st to end	Night	16% 9% 21% 36% 17% 2	836
November	1st to 10th	Night	15% 8% 20% 37% 17% 3	760
	11th to 20th	Night	15% 13% 29% 32% 10% 1	760
	21st to end	Night	19% 12% 27% 31% 10%	760
December	1st to 10th	Night	24% 16% 25% 28% 7%	760
	11th to 20th	Night	22% 12% 31% 28% 7%	760
	21st to end	Night	23% 15% 27% 30% 5%	836

Page generated at 2024-11-03 02:11:27. Version ac07

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