Delta State University
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Delta State University clear sky chart from 2005-11-06 to 2025-03-27.

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% 6% 2 6% 4 4 4 4 5% 7% 44%	108720
	Night	13% 6% 2 5% 4 3 4 3 5% 7% 48%	110769
Transparency	Day	37% 6% 10% 22% 19% 6%	112366
	Night	35% 5% 9% 22% 22% 8%	115264
Seeing	Day	14% 7% 20% 24% 23% 12%	15644
	Night	15% 6% 23% 32% 21% 4	25563

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	16% 10% 4 9% 3 3 2 2 3 4 45%	4077
	11th to 20th	Day	17% 5% 3 6% 3 3 3 3 4 5% 49%	4080
	21st to end	Day	19% 9% 3 6% 4 3 2 1 3 4 46%	4488
February	1st to 10th	Day	19% 9% 3 5% 4 4 4 3 5% 5% 40%	1924
	11th to 20th	Day	22% 8% 3 6% 4 3 3 2 4 4 40%	1948
	21st to end	Day	22% 8% 2 7% 4 3 4 3 3 6% 38%	1650
March	1st to 10th	Day	18% 11% 4 10% 4 4 3 3 5% 5% 32%	3408
	11th to 20th	Day	14% 7% 3 7% 4 4 4 4 6% 7% 40%	3590
	21st to end	Day	12% 7% 3 9% 5% 4 4 4 5% 5% 42%	4031
April	1st to 10th	Day	13% 6% 2 7% 4 5% 4 4 5% 7% 44%	2280
	11th to 20th	Day	14% 7% 3 5% 4 3 4 4 6% 6% 44%	2254
	21st to end	Day	9% 6% 2 6% 4 5% 5% 3 5% 8% 46%	2280
May	1st to 10th	Day	13% 5% 3 6% 5% 4 4 4 6% 8% 43%	3765
	11th to 20th	Day	11% 5% 2 7% 5% 5% 6% 4 7% 8% 42%	3764
	21st to end	Day	11% 6% 2 7% 5% 5% 6% 5% 8% 9% 37%	4617
June	1st to 10th	Day	7% 5% 2 6% 6% 5% 5% 4 6% 10% 43%	2660
	11th to 20th	Day	5% 4 2 5% 4 6% 5% 5% 7% 9% 48%	2660
	21st to end	Day	6% 5% 2 4 5% 5% 5% 5% 7% 10% 48%	2660
July	1st to 10th	Day	4 5% 2 7% 6% 7% 7% 5% 8% 11% 37%	4188
	11th to 20th	Day	9% 6% 2 7% 5% 5% 6% 5% 9% 11% 34%	4120
	21st to end	Day	14% 8% 3 8% 6% 5% 6% 5% 8% 9% 30%	4465
August	1st to 10th	Day	3 2 1 3 4 3 4 4 5% 7% 65%	3826
	11th to 20th	Day	5% 4 2 6% 4 5% 5% 5% 8% 11% 45%	3729
	21st to end	Day	7% 5% 2 5% 4 5% 4 4 6% 9% 49%	4180
September	1st to 10th	Day	8% 5% 3 7% 4 5% 6% 4 6% 7% 46%	2280
	11th to 20th	Day	11% 6% 2 7% 4 4 5% 3 5% 7% 46%	2261
	21st to end	Day	10% 4 1 5% 4 3 4 3 5% 6% 54%	2090
October	1st to 10th	Day	6% 4 1 5% 3 3 3 3 5% 6% 61%	1905
	11th to 20th	Day	11% 4 2 4 3 3 3 2 4 5% 59%	1900
	21st to end	Day	15% 6% 2 4 3 3 2 2 4 5% 54%	2090
November	1st to 10th	Day	12% 5% 2 5% 4 3 2 2 3 5% 56%	1943
	11th to 20th	Day	11% 5% 2 6% 4 3 4 3 4 7% 54%	1800
	21st to end	Day	17% 8% 3 5% 3 4 3 3 5% 5% 45%	1800
December	1st to 10th	Day	17% 8% 2 6% 4 3 3 3 4 4 45%	2905
	11th to 20th	Day	20% 10% 3 6% 4 3 3 2 4 4 40%	3008
	21st to end	Day	14% 7% 3 7% 4 4 4 3 4 6% 45%	4094
January	1st to 10th	Night	17% 6% 2 5% 3 3 3 3 4 5% 48%	5888
	11th to 20th	Night	17% 6% 2 5% 3 3 3 2 3 4 53%	5900
	21st to end	Night	23% 8% 2 5% 3 3 3 3 3 5% 43%	6490
February	1st to 10th	Night	20% 8% 2 6% 4 3 3 2 4 5% 42%	2474
	11th to 20th	Night	19% 7% 2 6% 4 3 3 3 4 5% 44%	2338
	21st to end	Night	19% 7% 2 7% 4 4 3 2 3 5% 43%	1980
March	1st to 10th	Night	16% 10% 3 7% 5% 4 3 3 4 6% 39%	3695
	11th to 20th	Night	13% 7% 2 5% 4 4 4 4 5% 8% 45%	3590
	21st to end	Night	13% 6% 3 7% 4 4 5% 3 5% 6% 43%	3736
April	1st to 10th	Night	12% 5% 2 6% 4 3 4 4 7% 6% 48%	1900
	11th to 20th	Night	13% 6% 2 5% 4 3 3 3 6% 8% 48%	1875
	21st to end	Night	11% 6% 2 6% 4 4 4 3 4 7% 51%	1900
May	1st to 10th	Night	15% 6% 3 6% 3 3 3 3 6% 10% 41%	3130
	11th to 20th	Night	14% 6% 2 5% 4 3 4 3 5% 8% 45%	3129
	21st to end	Night	11% 6% 2 6% 4 5% 6% 4 7% 10% 40%	2937
June	1st to 10th	Night	5% 4 2 6% 4 3 5% 5% 6% 11% 48%	1520
	11th to 20th	Night	3 3 1 3 3 3 4 4 9% 11% 54%	1520
	21st to end	Night	3 4 1 5% 3 4 4 5% 8% 9% 53%	1520
July	1st to 10th	Night	4 4 2 6% 5% 5% 6% 5% 8% 14% 41%	2775
	11th to 20th	Night	8% 4 2 5% 4 4 5% 5% 7% 12% 44%	2850
	21st to end	Night	11% 8% 3 7% 5% 4 4 4 7% 9% 38%	3098
August	1st to 10th	Night	2 1 1 2 2 2 3 3 4 7% 71%	3104
	11th to 20th	Night	4 3 1 5% 4 4 4 4 7% 11% 53%	3100
	21st to end	Night	5% 5% 2 6% 5% 4 4 4 5% 8% 53%	3476
September	1st to 10th	Night	8% 4 2 6% 5% 5% 4 3 5% 6% 52%	1900
	11th to 20th	Night	8% 6% 3 7% 5% 4 4 3 5% 7% 49%	1900
	21st to end	Night	9% 3 2 4 3 3 4 3 6% 8% 56%	2088
October	1st to 10th	Night	7% 3 1 3 2 2 3 2 5% 6% 65%	2270
	11th to 20th	Night	10% 4 1 4 3 3 3 3 4 6% 59%	2280
	21st to end	Night	14% 6% 2 4 3 3 2 2 4 5% 55%	2508
November	1st to 10th	Night	11% 5% 2 5% 3 3 3 4 5% 5% 55%	2350
	11th to 20th	Night	11% 4 2 5% 4 3 3 2 4 6% 55%	2600
	21st to end	Night	14% 5% 2 5% 3 4 4 3 4 5% 50%	2600
December	1st to 10th	Night	19% 7% 2 5% 3 3 3 3 4 5% 47%	4271
	11th to 20th	Night	18% 7% 2 6% 4 3 3 3 3 5% 46%	5199
	21st to end	Night	16% 8% 3 6% 4 4 4 3 5% 6% 42%	6878

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	46% 2 5% 27% 18% 2	4078
	11th to 20th	Day	38% 3 7% 24% 24% 4	4080
	21st to end	Day	45% 2 6% 16% 23% 8%	4488
February	1st to 10th	Day	46% 4 7% 20% 17% 6%	1924
	11th to 20th	Day	49% 4 5% 19% 17% 6%	1958
	21st to end	Day	49% 4 6% 15% 17% 8%	1650
March	1st to 10th	Day	54% 5% 6% 13% 15% 7%	3408
	11th to 20th	Day	40% 7% 9% 20% 18% 6%	3590
	21st to end	Day	44% 5% 7% 20% 21% 3	4031
April	1st to 10th	Day	39% 6% 10% 20% 20% 5%	2280
	11th to 20th	Day	39% 6% 10% 19% 22% 6%	2254
	21st to end	Day	35% 7% 10% 22% 24% 2	2280
May	1st to 10th	Day	37% 8% 11% 28% 13% 2	3800
	11th to 20th	Day	36% 10% 13% 25% 15% 2	3768
	21st to end	Day	38% 10% 15% 25% 10% 2	4630
June	1st to 10th	Day	35% 8% 13% 24% 18% 2	2660
	11th to 20th	Day	30% 7% 15% 27% 18% 4	2660
	21st to end	Day	29% 8% 15% 25% 19% 4	2660
July	1st to 10th	Day	38% 8% 21% 20% 10% 2	4124
	11th to 20th	Day	40% 6% 16% 29% 7% 2	4051
	21st to end	Day	49% 7% 15% 22% 7% 1	4325
August	1st to 10th	Day	18% 6% 15% 33% 27% 2	3812
	11th to 20th	Day	30% 6% 20% 31% 11% 2	3765
	21st to end	Day	33% 5% 12% 23% 24% 3	4179
September	1st to 10th	Day	35% 8% 12% 19% 19% 7%	2280
	11th to 20th	Day	38% 7% 10% 16% 22% 8%	2261
	21st to end	Day	30% 6% 8% 22% 22% 11%	2090
October	1st to 10th	Day	15% 3 5% 15% 25% 36%	3165
	11th to 20th	Day	17% 2 4 18% 37% 23%	3140
	21st to end	Day	27% 3 4 19% 35% 12%	3428
November	1st to 10th	Day	32% 3 8% 19% 29% 9%	1943
	11th to 20th	Day	32% 4 7% 18% 29% 11%	1800
	21st to end	Day	41% 4 7% 20% 23% 6%	1800
December	1st to 10th	Day	44% 3 4 24% 22% 3	2905
	11th to 20th	Day	48% 3 4 18% 21% 5%	3005
	21st to end	Day	40% 5% 9% 25% 19% 3	4094
January	1st to 10th	Night	40% 3 6% 27% 22% 2	5888
	11th to 20th	Night	38% 3 4 21% 28% 7%	5900
	21st to end	Night	46% 2 7% 17% 22% 6%	6490
February	1st to 10th	Night	45% 3 6% 19% 21% 6%	2474
	11th to 20th	Night	44% 3 7% 20% 18% 8%	2339
	21st to end	Night	45% 4 6% 15% 19% 11%	1980
March	1st to 10th	Night	45% 6% 7% 14% 16% 11%	3695
	11th to 20th	Night	36% 7% 10% 19% 17% 11%	3590
	21st to end	Night	38% 7% 8% 19% 24% 3	3736
April	1st to 10th	Night	35% 6% 9% 21% 20% 9%	1900
	11th to 20th	Night	34% 5% 9% 19% 23% 9%	1875
	21st to end	Night	34% 5% 10% 22% 24% 6%	1900
May	1st to 10th	Night	37% 8% 12% 23% 16% 3	3160
	11th to 20th	Night	36% 7% 12% 30% 14% 1	3130
	21st to end	Night	36% 11% 15% 22% 15% 2	2945
June	1st to 10th	Night	28% 10% 16% 27% 18% 2	1520
	11th to 20th	Night	21% 8% 15% 30% 20% 6%	1520
	21st to end	Night	24% 8% 13% 28% 22% 5%	1520
July	1st to 10th	Night	32% 8% 24% 21% 13% 2	2730
	11th to 20th	Night	31% 6% 20% 31% 9% 2	2796
	21st to end	Night	43% 6% 15% 25% 10% 1	2999
August	1st to 10th	Night	13% 5% 13% 33% 33% 3	3094
	11th to 20th	Night	25% 5% 20% 31% 16% 3	3130
	21st to end	Night	30% 6% 10% 22% 27% 6%	3476
September	1st to 10th	Night	31% 7% 12% 21% 19% 9%	1900
	11th to 20th	Night	34% 7% 8% 18% 25% 8%	1900
	21st to end	Night	26% 4 10% 24% 25% 11%	2088
October	1st to 10th	Night	15% 3 6% 17% 24% 36%	3790
	11th to 20th	Night	18% 2 3 17% 31% 30%	3779
	21st to end	Night	23% 2 5% 17% 35% 17%	4120
November	1st to 10th	Night	31% 4 8% 18% 28% 10%	2350
	11th to 20th	Night	31% 3 7% 19% 26% 14%	2600
	21st to end	Night	36% 4 7% 20% 23% 9%	2600
December	1st to 10th	Night	41% 3 5% 24% 23% 4	4271
	11th to 20th	Night	43% 2 8% 19% 22% 6%	5201
	21st to end	Night	42% 5% 10% 22% 19% 3	6878

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	20% 16% 40% 17% 6% 1	300
	11th to 20th	Day	25% 16% 32% 21% 4 2	300
	21st to end	Day	20% 14% 41% 19% 5%	330
February	1st to 10th	Day	25% 12% 33% 19% 10% 1	300
	11th to 20th	Day	33% 18% 29% 14% 5%	300
	21st to end	Day	30% 18% 29% 16% 7%	249
March	1st to 10th	Day	23% 15% 34% 18% 9% 1	300
	11th to 20th	Day	20% 17% 39% 21% 4	300
	21st to end	Day	17% 15% 37% 21% 9% 2	402
April	1st to 10th	Day	16% 15% 30% 29% 9% 1	460
	11th to 20th	Day	18% 12% 30% 27% 10% 3	452
	21st to end	Day	14% 10% 28% 27% 18% 3	460
May	1st to 10th	Day	13% 11% 25% 31% 18% 2	463
	11th to 20th	Day	12% 3 24% 29% 22% 10%	487
	21st to end	Day	8% 4 18% 31% 25% 14%	655
June	1st to 10th	Day	11% 3 11% 29% 32% 16%	680
	11th to 20th	Day	6% 1 11% 31% 35% 17%	680
	21st to end	Day	7% 2 10% 28% 34% 19%	680
July	1st to 10th	Day	6% 1 8% 23% 38% 24%	671
	11th to 20th	Day	9% 2 6% 21% 33% 29%	668
	21st to end	Day	8% 1 5% 22% 35% 28%	739
August	1st to 10th	Day	7% 1 6% 20% 39% 27%	515
	11th to 20th	Day	8% 2 5% 20% 42% 22%	479
	21st to end	Day	15% 1 4 16% 33% 31%	539
September	1st to 10th	Day	9% 1 7% 26% 36% 21%	490
	11th to 20th	Day	11% 2 8% 22% 33% 23%	490
	21st to end	Day	13% 3 9% 28% 31% 15%	490
October	1st to 10th	Day	7% 3 21% 29% 24% 17%	305
	11th to 20th	Day	10% 5% 29% 30% 22% 5%	300
	21st to end	Day	18% 6% 25% 30% 16% 5%	330
November	1st to 10th	Day	20% 6% 22% 27% 21% 4	300
	11th to 20th	Day	11% 9% 35% 31% 12% 2	300
	21st to end	Day	20% 14% 28% 21% 13% 4	300
December	1st to 10th	Day	19% 13% 35% 23% 8% 1	300
	11th to 20th	Day	22% 12% 33% 20% 10% 2	300
	21st to end	Day	21% 17% 32% 22% 7% 1	330
January	1st to 10th	Night	21% 11% 33% 30% 6%	1000
	11th to 20th	Night	23% 11% 32% 28% 6%	1000
	21st to end	Night	23% 9% 36% 29% 3	1100
February	1st to 10th	Night	24% 10% 32% 30% 5%	874
	11th to 20th	Night	23% 11% 34% 27% 3	783
	21st to end	Night	23% 13% 34% 27% 3	660
March	1st to 10th	Night	17% 10% 32% 35% 7%	707
	11th to 20th	Night	17% 13% 32% 31% 7% 1	600
	21st to end	Night	18% 7% 32% 29% 12% 1	647
April	1st to 10th	Night	14% 8% 35% 33% 9% 1	570
	11th to 20th	Night	16% 7% 32% 32% 12% 1	563
	21st to end	Night	12% 8% 32% 34% 14% 1	570
May	1st to 10th	Night	13% 4 22% 45% 14% 2	570
	11th to 20th	Night	12% 4 22% 37% 22% 2	561
	21st to end	Night	9% 2 15% 35% 33% 6%	617
June	1st to 10th	Night	6% 1 11% 39% 37% 6%	570
	11th to 20th	Night	4 1 9% 35% 45% 6%	570
	21st to end	Night	5% 1 6% 34% 41% 13%	570
July	1st to 10th	Night	4 1 7% 26% 51% 11%	555
	11th to 20th	Night	6% 6% 25% 50% 13%	552
	21st to end	Night	5% 1 4 30% 45% 15%	624
August	1st to 10th	Night	5% 1 4 24% 53% 15%	567
	11th to 20th	Night	7% 2 3 29% 49% 11%	564
	21st to end	Night	7% 2 6% 24% 47% 14%	627
September	1st to 10th	Night	9% 1 6% 35% 41% 8%	570
	11th to 20th	Night	10% 2 9% 30% 42% 7%	570
	21st to end	Night	11% 2 11% 33% 39% 5%	758
October	1st to 10th	Night	8% 3 13% 33% 37% 6%	760
	11th to 20th	Night	12% 4 21% 41% 20% 2	760
	21st to end	Night	16% 6% 21% 36% 20% 1	836
November	1st to 10th	Night	13% 5% 22% 38% 20% 3	780
	11th to 20th	Night	13% 7% 30% 35% 14% 1	800
	21st to end	Night	17% 7% 28% 32% 14% 2	800
December	1st to 10th	Night	20% 9% 30% 32% 8%	808
	11th to 20th	Night	21% 8% 31% 32% 9%	1000
	21st to end	Night	23% 10% 30% 30% 7%	1100

Page generated at 2025-03-24 08:04:28. Version ac07

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