Denison
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Denison clear sky chart from 2005-11-06 to 2024-10-20.

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 4 4 5% 7% 40%	101147
	Night	11% 8% 3 8% 4 4 4 3 5% 6% 44%	97626
Transparency	Day	43% 6% 12% 24% 13% 2	100954
	Night	40% 5% 12% 25% 15% 2	97491
Seeing	Day	16% 9% 31% 28% 13% 3	15812
	Night	15% 9% 34% 31% 10% 1	25644

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	8% 13% 4 19% 10% 7% 5% 4 4 5% 22%	2719
	11th to 20th	Day	7% 14% 6% 12% 6% 6% 8% 3 5% 7% 26%	2850
	21st to end	Day	10% 14% 8% 18% 8% 6% 4 3 5% 5% 20%	3135
February	1st to 10th	Day	10% 13% 5% 10% 7% 6% 5% 4 5% 8% 28%	1710
	11th to 20th	Day	9% 11% 4 10% 5% 5% 5% 2 4 6% 37%	1664
	21st to end	Day	12% 12% 3 9% 6% 5% 4 4 5% 6% 35%	1534
March	1st to 10th	Day	13% 9% 3 8% 4 3 3 2 4 5% 45%	3434
	11th to 20th	Day	11% 9% 3 8% 4 3 4 3 5% 5% 45%	3480
	21st to end	Day	22% 13% 6% 11% 5% 5% 4 3 5% 5% 21%	3814
April	1st to 10th	Day	15% 10% 3 7% 4 4 4 3 5% 6% 38%	2190
	11th to 20th	Day	18% 10% 3 7% 4 5% 3 3 5% 6% 36%	2326
	21st to end	Day	21% 9% 2 7% 5% 3 4 4 4 6% 36%	2470
May	1st to 10th	Day	18% 9% 3 7% 5% 4 6% 5% 6% 7% 31%	4082
	11th to 20th	Day	13% 8% 3 6% 4 4 4 4 5% 6% 44%	4109
	21st to end	Day	15% 7% 3 6% 4 4 5% 4 7% 7% 39%	4824
June	1st to 10th	Day	10% 5% 2 6% 4 5% 5% 4 6% 8% 45%	2660
	11th to 20th	Day	9% 5% 2 6% 4 4 4 4 7% 9% 45%	2660
	21st to end	Day	8% 5% 2 5% 4 5% 5% 5% 6% 8% 47%	2660
July	1st to 10th	Day	11% 5% 2 7% 4 5% 5% 5% 7% 9% 40%	4440
	11th to 20th	Day	6% 3 1 5% 4 4 4 4 5% 7% 57%	4137
	21st to end	Day	4 3 2 5% 4 5% 5% 4 7% 10% 51%	4465
August	1st to 10th	Day	9% 6% 2 5% 4 5% 5% 4 7% 9% 44%	4104
	11th to 20th	Day	15% 7% 3 7% 4 4 5% 3 5% 7% 40%	4041
	21st to end	Day	9% 5% 2 5% 4 4 5% 4 6% 8% 48%	4411
September	1st to 10th	Day	12% 5% 2 5% 3 3 4 3 5% 7% 52%	2278
	11th to 20th	Day	10% 5% 2 5% 3 3 3 3 5% 9% 52%	2090
	21st to end	Day	11% 4 1 4 3 3 4 4 5% 8% 54%	2090
October	1st to 10th	Day	14% 5% 2 5% 4 3 3 3 4 6% 50%	1905
	11th to 20th	Day	13% 5% 3 5% 3 4 3 3 3 6% 52%	1890
	21st to end	Day	15% 8% 3 7% 3 3 4 3 4 5% 44%	1980
November	1st to 10th	Day	9% 6% 2 6% 4 4 4 3 5% 7% 50%	1719
	11th to 20th	Day	11% 8% 3 10% 7% 3 4 3 5% 8% 40%	1535
	21st to end	Day	12% 9% 3 7% 4 2 3 4 6% 7% 43%	1520
December	1st to 10th	Day	10% 8% 4 10% 6% 5% 4 4 5% 7% 38%	1520
	11th to 20th	Day	9% 11% 4 9% 7% 6% 5% 5% 6% 7% 31%	1918
	21st to end	Day	17% 11% 6% 18% 5% 4 4 4 4 5% 21%	2783
January	1st to 10th	Night	9% 12% 4 22% 10% 5% 4 3 4 5% 24%	4232
	11th to 20th	Night	7% 13% 4 10% 6% 5% 7% 5% 10% 6% 27%	4120
	21st to end	Night	10% 15% 7% 16% 6% 6% 4 3 4 5% 26%	4532
February	1st to 10th	Night	11% 11% 4 9% 6% 5% 5% 3 5% 6% 35%	2470
	11th to 20th	Night	10% 10% 4 7% 5% 5% 4 3 5% 6% 40%	2403
	21st to end	Night	9% 8% 4 9% 5% 4 5% 3 4 5% 44%	1937
March	1st to 10th	Night	11% 8% 3 6% 3 3 3 3 3 5% 51%	3420
	11th to 20th	Night	10% 7% 3 5% 3 3 3 3 4 7% 52%	3480
	21st to end	Night	21% 11% 4 10% 6% 5% 4 3 5% 7% 25%	3817
April	1st to 10th	Night	13% 9% 2 6% 4 3 4 3 6% 7% 43%	1989
	11th to 20th	Night	13% 9% 3 6% 4 4 3 3 5% 6% 43%	1801
	21st to end	Night	17% 10% 2 6% 4 4 4 3 5% 8% 38%	1710
May	1st to 10th	Night	18% 7% 2 6% 3 3 3 3 5% 7% 42%	2823
	11th to 20th	Night	11% 6% 2 6% 3 3 4 3 5% 7% 50%	2792
	21st to end	Night	14% 7% 2 7% 4 4 4 3 5% 7% 43%	2743
June	1st to 10th	Night	6% 4 2 6% 4 4 5% 4 6% 8% 52%	1520
	11th to 20th	Night	7% 4 1 6% 4 3 4 4 6% 10% 50%	1520
	21st to end	Night	5% 4 2 5% 3 3 4 4 7% 9% 54%	1520
July	1st to 10th	Night	8% 5% 2 5% 4 3 4 3 6% 9% 50%	2530
	11th to 20th	Night	5% 2 1 3 2 3 3 3 5% 8% 66%	2815
	21st to end	Night	3 3 1 5% 3 4 5% 4 7% 9% 57%	3098
August	1st to 10th	Night	5% 4 2 5% 3 4 4 3 6% 9% 54%	2836
	11th to 20th	Night	10% 6% 2 5% 3 3 3 3 5% 7% 53%	2798
	21st to end	Night	8% 5% 2 5% 3 4 3 3 5% 7% 55%	3250
September	1st to 10th	Night	9% 4 1 4 3 3 3 3 4 7% 59%	1900
	11th to 20th	Night	9% 4 1 4 4 3 4 4 5% 7% 56%	2089
	21st to end	Night	10% 5% 1 4 3 3 3 3 5% 5% 58%	2090
October	1st to 10th	Night	13% 7% 2 5% 2 2 3 2 5% 6% 52%	2256
	11th to 20th	Night	15% 7% 3 5% 2 3 3 2 4 5% 52%	2275
	21st to end	Night	15% 8% 2 6% 3 3 3 2 3 6% 48%	2376
November	1st to 10th	Night	8% 5% 2 5% 3 3 3 3 6% 6% 55%	2359
	11th to 20th	Night	10% 8% 2 7% 5% 4 3 4 6% 6% 47%	2642
	21st to end	Night	12% 10% 3 5% 4 3 3 3 4 6% 47%	2660
December	1st to 10th	Night	8% 10% 3 9% 6% 4 5% 4 5% 7% 39%	2660
	11th to 20th	Night	10% 10% 4 8% 5% 5% 4 3 5% 8% 39%	3279
	21st to end	Night	16% 13% 6% 16% 6% 4 4 2 4 4 26%	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	65% 4 11% 14% 6% 1	2720
	11th to 20th	Day	59% 3 9% 23% 6%	2850
	21st to end	Day	66% 4 12% 12% 5%	3135
February	1st to 10th	Day	55% 5% 12% 17% 10% 1	1710
	11th to 20th	Day	48% 4 11% 21% 14% 2	1673
	21st to end	Day	50% 6% 9% 22% 10% 4	1534
March	1st to 10th	Day	43% 3 9% 29% 15% 2	3434
	11th to 20th	Day	40% 5% 10% 28% 14% 3	3480
	21st to end	Day	64% 7% 11% 13% 4 1	3814
April	1st to 10th	Day	47% 5% 12% 25% 11% 1	2190
	11th to 20th	Day	49% 5% 11% 21% 12% 2	2326
	21st to end	Day	50% 5% 9% 22% 13%	2470
May	1st to 10th	Day	49% 7% 12% 19% 12% 1	4120
	11th to 20th	Day	41% 6% 9% 28% 15% 1	4113
	21st to end	Day	41% 7% 12% 23% 16% 1	4837
June	1st to 10th	Day	36% 6% 16% 28% 12% 2	2660
	11th to 20th	Day	34% 7% 15% 27% 16% 2	2660
	21st to end	Day	33% 7% 16% 28% 13% 3	2660
July	1st to 10th	Day	38% 8% 15% 29% 9% 2	4371
	11th to 20th	Day	26% 5% 15% 32% 20% 3	4067
	21st to end	Day	24% 9% 18% 27% 20% 2	4325
August	1st to 10th	Day	36% 7% 13% 28% 15% 1	4090
	11th to 20th	Day	44% 5% 10% 30% 11% 1	4080
	21st to end	Day	32% 8% 15% 25% 18% 3	4410
September	1st to 10th	Day	32% 5% 11% 28% 20% 3	2278
	11th to 20th	Day	30% 4 14% 33% 17% 2	2090
	21st to end	Day	28% 4 12% 30% 24% 1	2090
October	1st to 10th	Day	36% 4 9% 29% 21% 1	1905
	11th to 20th	Day	36% 4 9% 28% 19% 4	1890
	21st to end	Day	43% 4 11% 21% 18% 3	1980
November	1st to 10th	Day	34% 4 16% 24% 20% 2	1719
	11th to 20th	Day	44% 3 12% 24% 16% 1	1535
	21st to end	Day	41% 3 15% 26% 13% 1	1520
December	1st to 10th	Day	46% 5% 15% 22% 10% 2	1520
	11th to 20th	Day	50% 6% 16% 22% 5%	1915
	21st to end	Day	64% 5% 9% 14% 7% 1	2783
January	1st to 10th	Night	64% 3 9% 14% 9%	4232
	11th to 20th	Night	52% 5% 13% 19% 10% 2	4120
	21st to end	Night	62% 4 12% 13% 8% 1	4532
February	1st to 10th	Night	51% 4 11% 22% 11% 2	2470
	11th to 20th	Night	44% 4 11% 24% 14% 3	2404
	21st to end	Night	43% 4 11% 22% 18% 3	1937
March	1st to 10th	Night	37% 4 8% 29% 19% 2	3420
	11th to 20th	Night	33% 5% 9% 34% 15% 5%	3480
	21st to end	Night	58% 8% 15% 13% 4 1	3817
April	1st to 10th	Night	41% 4 12% 25% 16% 2	1989
	11th to 20th	Night	42% 4 12% 22% 18% 2	1801
	21st to end	Night	45% 5% 12% 23% 14% 1	1710
May	1st to 10th	Night	41% 5% 12% 23% 17% 2	2850
	11th to 20th	Night	34% 7% 11% 25% 18% 5%	2793
	21st to end	Night	41% 6% 13% 22% 16% 3	2751
June	1st to 10th	Night	29% 7% 14% 31% 15% 4	1520
	11th to 20th	Night	28% 7% 14% 26% 21% 4	1520
	21st to end	Night	25% 8% 15% 31% 18% 3	1520
July	1st to 10th	Night	30% 6% 17% 32% 13% 2	2490
	11th to 20th	Night	18% 5% 18% 35% 22% 3	2763
	21st to end	Night	22% 9% 16% 32% 20% 2	2999
August	1st to 10th	Night	26% 6% 16% 34% 16% 2	2826
	11th to 20th	Night	31% 5% 16% 29% 16% 2	2825
	21st to end	Night	28% 6% 16% 26% 19% 6%	3250
September	1st to 10th	Night	26% 4 12% 31% 24% 4	1900
	11th to 20th	Night	27% 5% 12% 33% 21% 2	2089
	21st to end	Night	28% 3 10% 31% 24% 4	2090
October	1st to 10th	Night	34% 4 9% 27% 23% 2	2256
	11th to 20th	Night	35% 4 9% 25% 23% 4	2275
	21st to end	Night	39% 4 13% 23% 21% 2	2376
November	1st to 10th	Night	29% 5% 16% 25% 22% 4	2359
	11th to 20th	Night	38% 4 13% 27% 17% 2	2642
	21st to end	Night	40% 4 10% 29% 15% 2	2660
December	1st to 10th	Night	44% 5% 12% 27% 11% 1	2660
	11th to 20th	Night	44% 4 15% 29% 7%	3281
	21st to end	Night	62% 4 8% 19% 7%	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	18% 15% 34% 25% 7%	270
	11th to 20th	Day	19% 13% 41% 23% 3 1	270
	21st to end	Day	19% 10% 40% 24% 6% 1	297
February	1st to 10th	Day	18% 16% 40% 24% 2	270
	11th to 20th	Day	16% 16% 40% 23% 6% 1	270
	21st to end	Day	21% 16% 40% 19% 3	225
March	1st to 10th	Day	19% 16% 43% 18% 4 1	270
	11th to 20th	Day	24% 13% 38% 20% 6%	270
	21st to end	Day	35% 14% 33% 15% 3	297
April	1st to 10th	Day	25% 16% 37% 19% 3	370
	11th to 20th	Day	27% 13% 33% 20% 7% 1	524
	21st to end	Day	27% 13% 30% 21% 7% 2	650
May	1st to 10th	Day	24% 12% 31% 23% 8% 1	653
	11th to 20th	Day	21% 11% 29% 23% 12% 3	675
	21st to end	Day	19% 7% 31% 29% 13% 2	734
June	1st to 10th	Day	8% 6% 27% 35% 21% 3	680
	11th to 20th	Day	10% 8% 33% 30% 15% 3	680
	21st to end	Day	9% 8% 34% 31% 15% 3	680
July	1st to 10th	Day	9% 3 19% 35% 25% 8%	671
	11th to 20th	Day	7% 3 28% 39% 16% 7%	668
	21st to end	Day	6% 3 23% 38% 26% 4	739
August	1st to 10th	Day	9% 3 22% 38% 24% 4	676
	11th to 20th	Day	12% 3 23% 35% 22% 4	665
	21st to end	Day	10% 4 21% 40% 19% 5%	679
September	1st to 10th	Day	13% 4 26% 35% 17% 5%	488
	11th to 20th	Day	7% 7% 36% 30% 16% 4	300
	21st to end	Day	12% 7% 37% 29% 12% 2	300
October	1st to 10th	Day	18% 9% 29% 26% 14% 4	300
	11th to 20th	Day	16% 17% 38% 22% 5% 2	297
	21st to end	Day	22% 16% 35% 21% 6% 1	297
November	1st to 10th	Day	16% 15% 40% 19% 7% 3	270
	11th to 20th	Day	19% 19% 39% 19% 4	270
	21st to end	Day	21% 15% 34% 24% 6%	270
December	1st to 10th	Day	11% 14% 40% 26% 7% 1	270
	11th to 20th	Day	16% 16% 37% 24% 7% 1	270
	21st to end	Day	26% 16% 40% 17% 2	297
January	1st to 10th	Night	13% 15% 38% 29% 4 1	950
	11th to 20th	Night	15% 13% 40% 25% 6% 1	950
	21st to end	Night	19% 9% 40% 26% 5%	1045
February	1st to 10th	Night	16% 9% 44% 26% 4	950
	11th to 20th	Night	16% 11% 43% 25% 5%	929
	21st to end	Night	15% 11% 45% 23% 5% 1	681
March	1st to 10th	Night	18% 12% 38% 25% 6% 1	571
	11th to 20th	Night	19% 10% 38% 26% 8%	570
	21st to end	Night	26% 9% 34% 24% 5% 1	627
April	1st to 10th	Night	18% 15% 41% 23% 4	570
	11th to 20th	Night	20% 12% 37% 24% 7%	563
	21st to end	Night	22% 11% 32% 26% 8%	570
May	1st to 10th	Night	20% 7% 35% 30% 8%	570
	11th to 20th	Night	17% 8% 30% 35% 10%	561
	21st to end	Night	16% 6% 33% 33% 12%	617
June	1st to 10th	Night	8% 4 27% 46% 16% 1	570
	11th to 20th	Night	9% 4 34% 39% 13% 1	570
	21st to end	Night	6% 6% 32% 41% 15%	570
July	1st to 10th	Night	6% 3 18% 46% 25% 1	555
	11th to 20th	Night	5% 1 22% 49% 21% 2	552
	21st to end	Night	4 2 17% 52% 24% 1	624
August	1st to 10th	Night	9% 2 20% 44% 23% 2	567
	11th to 20th	Night	12% 3 21% 41% 22% 2	564
	21st to end	Night	8% 2 23% 45% 19% 3	627
September	1st to 10th	Night	11% 4 24% 39% 20% 2	570
	11th to 20th	Night	10% 2 32% 40% 14% 2	570
	21st to end	Night	13% 5% 34% 34% 14% 1	570
October	1st to 10th	Night	16% 8% 30% 33% 11% 2	736
	11th to 20th	Night	19% 11% 37% 28% 5%	759
	21st to end	Night	22% 12% 29% 29% 8%	792
November	1st to 10th	Night	11% 13% 39% 29% 8%	879
	11th to 20th	Night	14% 14% 42% 24% 5%	950
	21st to end	Night	18% 11% 37% 25% 8%	950
December	1st to 10th	Night	15% 12% 40% 27% 5%	950
	11th to 20th	Night	17% 10% 39% 28% 6%	950
	21st to end	Night	20% 13% 38% 24% 4	1045

Page generated at 2024-10-17 12:09:41. Version ac07

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