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 2026-07-31.

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% 3 6% 4 4 4 4 6% 7% 44%	137102
	Night	13% 6% 2 6% 4 4 4 3 5% 7% 47%	136130
Transparency	Day	39% 5% 11% 22% 18% 5%	140709
	Night	36% 4 10% 22% 21% 8%	140604
Seeing	Day	14% 7% 20% 25% 23% 12%	17568
	Night	15% 6% 23% 32% 21% 4	27256

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% 11% 4 8% 3 3 3 2 3 5% 41%	5289
	11th to 20th	Day	14% 5% 2 5% 3 3 2 3 4 5% 54%	5310
	21st to end	Day	21% 9% 4 7% 4 3 2 2 3 4 43%	5812
February	1st to 10th	Day	19% 8% 3 5% 4 4 4 3 5% 5% 41%	2020
	11th to 20th	Day	22% 8% 3 7% 4 3 3 2 4 4 39%	2048
	21st to end	Day	21% 8% 3 7% 4 3 3 3 3 6% 38%	1730
March	1st to 10th	Day	19% 10% 4 10% 5% 4 4 3 4 5% 33%	4851
	11th to 20th	Day	12% 6% 3 5% 3 3 4 4 6% 7% 48%	5090
	21st to end	Day	13% 7% 3 9% 6% 4 4 3 5% 6% 40%	5809
April	1st to 10th	Day	13% 6% 2 7% 4 5% 5% 4 6% 7% 43%	2520
	11th to 20th	Day	12% 6% 3 5% 4 3 3 4 6% 6% 46%	2494
	21st to end	Day	10% 7% 2 7% 4 5% 5% 4 5% 8% 44%	2520
May	1st to 10th	Day	16% 8% 3 7% 5% 4 5% 4 6% 6% 36%	7021
	11th to 20th	Day	10% 6% 3 8% 5% 5% 6% 4 6% 8% 39%	7031
	21st to end	Day	13% 8% 3 8% 5% 6% 6% 5% 8% 9% 29%	8644
June	1st to 10th	Day	7% 5% 2 6% 6% 5% 5% 4 6% 10% 42%	2940
	11th to 20th	Day	6% 4 2 6% 4 6% 6% 5% 7% 9% 45%	2940
	21st to end	Day	5% 5% 1 4 5% 5% 5% 5% 7% 10% 48%	2940
July	1st to 10th	Day	4 5% 2 7% 6% 6% 6% 5% 8% 10% 40%	6128
	11th to 20th	Day	7% 4 2 6% 5% 5% 6% 5% 8% 11% 41%	6030
	21st to end	Day	10% 6% 2 6% 5% 4 5% 4 8% 11% 38%	6553
August	1st to 10th	Day	3 2 1 3 4 3 4 3 5% 7% 65%	3947
	11th to 20th	Day	5% 4 2 6% 4 5% 5% 5% 8% 11% 46%	3849
	21st to end	Day	7% 5% 2 5% 4 5% 5% 4 6% 9% 49%	4312
September	1st to 10th	Day	8% 5% 3 6% 5% 5% 6% 4 6% 7% 46%	2400
	11th to 20th	Day	10% 6% 2 7% 4 4 5% 3 5% 7% 46%	2380
	21st to end	Day	10% 4 1 5% 4 3 4 3 5% 7% 54%	2200
October	1st to 10th	Day	6% 4 1 4 3 3 3 3 5% 6% 61%	2005
	11th to 20th	Day	11% 4 2 4 3 3 3 2 4 5% 60%	2000
	21st to end	Day	16% 6% 2 4 3 3 2 2 4 5% 54%	2200
November	1st to 10th	Day	12% 5% 2 5% 4 3 2 2 3 5% 57%	2042
	11th to 20th	Day	10% 5% 1 6% 4 3 4 3 4 7% 54%	1890
	21st to end	Day	16% 8% 3 5% 3 4 3 3 5% 6% 45%	1890
December	1st to 10th	Day	17% 9% 3 6% 4 3 3 3 4 4 44%	2994
	11th to 20th	Day	19% 10% 3 6% 4 3 3 2 4 4 41%	3088
	21st to end	Day	14% 7% 3 7% 4 4 4 3 4 6% 45%	4185
January	1st to 10th	Night	17% 8% 3 6% 4 3 3 3 4 5% 44%	7634
	11th to 20th	Night	13% 5% 2 5% 3 3 3 2 3 5% 57%	7680
	21st to end	Night	25% 7% 2 5% 3 3 3 3 4 5% 40%	8402
February	1st to 10th	Night	19% 8% 2 6% 4 3 3 2 4 5% 43%	2597
	11th to 20th	Night	19% 7% 3 6% 4 3 3 3 4 5% 43%	2458
	21st to end	Night	19% 7% 2 6% 4 3 3 2 3 5% 44%	2076
March	1st to 10th	Night	15% 9% 3 7% 5% 4 3 3 4 6% 42%	5265
	11th to 20th	Night	11% 6% 2 5% 4 4 4 3 5% 7% 49%	5090
	21st to end	Night	13% 6% 3 7% 4 4 5% 3 5% 6% 44%	5360
April	1st to 10th	Night	12% 5% 2 6% 4 4 4 4 6% 5% 47%	2100
	11th to 20th	Night	12% 6% 2 5% 3 3 3 3 5% 8% 49%	2075
	21st to end	Night	11% 6% 2 6% 4 4 4 3 4 7% 48%	2100
May	1st to 10th	Night	19% 9% 3 7% 4 3 4 3 5% 8% 34%	5832
	11th to 20th	Night	15% 8% 3 8% 5% 4 5% 3 5% 7% 37%	5829
	21st to end	Night	14% 8% 3 8% 5% 5% 6% 4 7% 9% 32%	5506
June	1st to 10th	Night	5% 4 2 6% 5% 3 6% 5% 7% 11% 47%	1680
	11th to 20th	Night	4 4 1 4 3 4 5% 4 9% 11% 52%	1680
	21st to end	Night	3 3 1 5% 3 4 4 5% 8% 10% 52%	1680
July	1st to 10th	Night	4 4 2 6% 5% 5% 6% 5% 9% 13% 42%	4062
	11th to 20th	Night	6% 4 2 4 3 3 5% 4 7% 13% 49%	4167
	21st to end	Night	8% 6% 2 5% 4 4 4 4 7% 11% 44%	4539
August	1st to 10th	Night	2 1 1 2 3 2 3 3 4 8% 70%	3203
	11th to 20th	Night	4 3 1 5% 4 4 4 4 7% 12% 53%	3200
	21st to end	Night	5% 5% 2 6% 5% 4 4 4 5% 8% 53%	3586
September	1st to 10th	Night	7% 4 2 6% 5% 5% 4 3 5% 6% 53%	2000
	11th to 20th	Night	7% 6% 3 7% 5% 4 4 3 5% 7% 49%	2000
	21st to end	Night	9% 3 2 4 3 3 4 3 6% 8% 55%	2198
October	1st to 10th	Night	7% 3 1 4 2 2 3 2 5% 6% 64%	2390
	11th to 20th	Night	10% 4 1 4 3 3 3 3 4 6% 60%	2400
	21st to end	Night	15% 6% 2 4 3 3 2 2 4 5% 54%	2640
November	1st to 10th	Night	10% 5% 2 5% 3 3 3 4 5% 5% 56%	2471
	11th to 20th	Night	10% 4 2 5% 4 3 3 2 4 6% 56%	2730
	21st to end	Night	15% 5% 2 5% 3 4 4 3 4 5% 49%	2730
December	1st to 10th	Night	18% 7% 3 5% 3 3 3 3 4 5% 47%	4402
	11th to 20th	Night	17% 7% 2 6% 4 3 3 3 3 4 47%	5339
	21st to end	Night	16% 8% 3 6% 4 4 4 3 5% 6% 42%	7029

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	49% 2 6% 27% 15% 2	5290
	11th to 20th	Day	33% 3 7% 23% 31% 4	5310
	21st to end	Day	49% 2 5% 14% 22% 7%	5812
February	1st to 10th	Day	45% 4 7% 21% 17% 6%	2020
	11th to 20th	Day	50% 3 6% 19% 16% 6%	2058
	21st to end	Day	48% 4 6% 15% 18% 9%	1730
March	1st to 10th	Day	54% 4 5% 16% 14% 8%	4851
	11th to 20th	Day	36% 5% 7% 16% 26% 11%	5090
	21st to end	Day	45% 4 7% 22% 19% 3	5811
April	1st to 10th	Day	40% 6% 10% 21% 19% 5%	2520
	11th to 20th	Day	37% 5% 10% 20% 22% 6%	2494
	21st to end	Day	38% 7% 11% 21% 22% 2	2520
May	1st to 10th	Day	47% 5% 9% 23% 13% 3	7056
	11th to 20th	Day	41% 6% 14% 21% 14% 3	7035
	21st to end	Day	48% 7% 16% 19% 10% 1	8658
June	1st to 10th	Day	35% 8% 13% 25% 18% 1	2940
	11th to 20th	Day	33% 7% 15% 25% 17% 4	2940
	21st to end	Day	30% 8% 16% 26% 17% 3	2940
July	1st to 10th	Day	37% 6% 20% 23% 13% 1	6064
	11th to 20th	Day	35% 5% 22% 32% 5% 1	5961
	21st to end	Day	39% 5% 17% 32% 6%	6371
August	1st to 10th	Day	18% 6% 15% 34% 26% 2	3933
	11th to 20th	Day	30% 6% 20% 32% 11% 2	3885
	21st to end	Day	33% 5% 12% 23% 24% 3	4311
September	1st to 10th	Day	35% 8% 12% 20% 18% 6%	2400
	11th to 20th	Day	37% 6% 9% 18% 21% 7%	2380
	21st to end	Day	30% 6% 9% 22% 22% 11%	2200
October	1st to 10th	Day	15% 3 5% 15% 26% 35%	3265
	11th to 20th	Day	17% 2 4 18% 37% 22%	3240
	21st to end	Day	28% 3 4 19% 35% 11%	3538
November	1st to 10th	Day	32% 3 8% 19% 30% 8%	2042
	11th to 20th	Day	31% 4 8% 19% 28% 10%	1890
	21st to end	Day	41% 3 7% 20% 23% 6%	1890
December	1st to 10th	Day	45% 3 4 23% 22% 3	2994
	11th to 20th	Day	48% 3 5% 18% 21% 5%	3085
	21st to end	Day	40% 5% 9% 25% 19% 3	4185
January	1st to 10th	Night	44% 3 7% 27% 18% 2	7635
	11th to 20th	Night	33% 2 4 19% 33% 9%	7680
	21st to end	Night	49% 2 5% 17% 20% 7%	8402
February	1st to 10th	Night	44% 3 6% 20% 22% 5%	2597
	11th to 20th	Night	45% 3 7% 20% 17% 8%	2459
	21st to end	Night	44% 4 6% 15% 20% 11%	2076
March	1st to 10th	Night	45% 4 6% 15% 19% 12%	5265
	11th to 20th	Night	34% 5% 8% 17% 18% 18%	5090
	21st to end	Night	40% 5% 8% 21% 21% 5%	5360
April	1st to 10th	Night	36% 6% 10% 20% 20% 8%	2100
	11th to 20th	Night	33% 5% 10% 21% 23% 9%	2075
	21st to end	Night	36% 4 10% 22% 22% 5%	2100
May	1st to 10th	Night	47% 5% 12% 19% 13% 3	5862
	11th to 20th	Night	47% 5% 10% 22% 12% 4	5830
	21st to end	Night	47% 8% 14% 15% 12% 3	5517
June	1st to 10th	Night	28% 9% 15% 27% 18% 2	1680
	11th to 20th	Night	23% 8% 16% 29% 19% 5%	1680
	21st to end	Night	24% 7% 15% 28% 21% 5%	1680
July	1st to 10th	Night	32% 7% 21% 25% 13% 2	4019
	11th to 20th	Night	27% 5% 24% 34% 8% 2	4116
	21st to end	Night	34% 5% 18% 33% 9% 1	4410
August	1st to 10th	Night	13% 5% 13% 33% 33% 3	3193
	11th to 20th	Night	25% 5% 21% 31% 15% 3	3230
	21st to end	Night	30% 5% 10% 22% 27% 5%	3586
September	1st to 10th	Night	31% 7% 12% 22% 19% 9%	2000
	11th to 20th	Night	34% 7% 9% 19% 24% 7%	2000
	21st to end	Night	27% 4 10% 23% 25% 11%	2198
October	1st to 10th	Night	15% 3 6% 17% 24% 35%	3910
	11th to 20th	Night	18% 2 3 17% 31% 29%	3899
	21st to end	Night	24% 2 5% 17% 35% 17%	4252
November	1st to 10th	Night	30% 4 8% 18% 29% 11%	2471
	11th to 20th	Night	30% 3 7% 21% 25% 13%	2730
	21st to end	Night	37% 4 7% 20% 23% 9%	2730
December	1st to 10th	Night	42% 3 5% 24% 23% 4	4402
	11th to 20th	Night	43% 2 8% 19% 23% 6%	5341
	21st to end	Night	42% 5% 10% 22% 19% 3	7029

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% 16% 38% 18% 6% 1	330
	11th to 20th	Day	23% 17% 33% 20% 4 2	330
	21st to end	Day	21% 15% 40% 19% 5%	363
February	1st to 10th	Day	23% 11% 35% 20% 9% 1	330
	11th to 20th	Day	33% 18% 28% 15% 5%	330
	21st to end	Day	29% 20% 28% 16% 7%	273
March	1st to 10th	Day	23% 15% 35% 19% 8% 1	330
	11th to 20th	Day	19% 17% 40% 20% 4	330
	21st to end	Day	16% 14% 36% 23% 9% 2	460
April	1st to 10th	Day	17% 14% 31% 29% 9% 1	540
	11th to 20th	Day	16% 13% 33% 26% 9% 3	532
	21st to end	Day	16% 9% 28% 27% 17% 3	540
May	1st to 10th	Day	14% 11% 28% 29% 16% 2	543
	11th to 20th	Day	13% 4 27% 27% 20% 8%	567
	21st to end	Day	10% 4 18% 32% 24% 12%	757
June	1st to 10th	Day	10% 3 13% 30% 30% 14%	780
	11th to 20th	Day	8% 1 13% 31% 32% 15%	780
	21st to end	Day	7% 2 9% 27% 35% 19%	780
July	1st to 10th	Day	5% 1 7% 23% 38% 25%	771
	11th to 20th	Day	9% 2 5% 22% 34% 28%	768
	21st to end	Day	7% 1 5% 23% 37% 27%	845
August	1st to 10th	Day	6% 1 6% 22% 39% 26%	556
	11th to 20th	Day	8% 2 5% 20% 41% 24%	519
	21st to end	Day	15% 1 5% 18% 32% 29%	583
September	1st to 10th	Day	9% 1 7% 27% 35% 19%	530
	11th to 20th	Day	11% 2 8% 22% 34% 24%	530
	21st to end	Day	13% 3 10% 29% 30% 15%	530
October	1st to 10th	Day	7% 2 21% 30% 24% 16%	335
	11th to 20th	Day	9% 5% 28% 31% 22% 5%	330
	21st to end	Day	20% 6% 24% 30% 16% 4	363
November	1st to 10th	Day	19% 7% 22% 27% 21% 4	330
	11th to 20th	Day	11% 9% 35% 32% 12% 2	330
	21st to end	Day	18% 15% 30% 21% 12% 4	330
December	1st to 10th	Day	19% 14% 35% 23% 8% 1	330
	11th to 20th	Day	20% 12% 34% 22% 10% 2	330
	21st to end	Day	20% 17% 33% 22% 7% 1	363
January	1st to 10th	Night	21% 11% 32% 30% 5%	1050
	11th to 20th	Night	22% 11% 34% 28% 5%	1050
	21st to end	Night	24% 9% 36% 28% 3	1155
February	1st to 10th	Night	23% 10% 33% 30% 5%	917
	11th to 20th	Night	24% 11% 34% 27% 3	823
	21st to end	Night	23% 14% 34% 27% 3	692
March	1st to 10th	Night	16% 10% 33% 35% 6%	742
	11th to 20th	Night	17% 13% 33% 30% 7%	630
	21st to end	Night	18% 8% 32% 30% 11% 1	693
April	1st to 10th	Night	15% 8% 35% 32% 9% 1	630
	11th to 20th	Night	15% 7% 33% 32% 11% 1	623
	21st to end	Night	13% 8% 30% 35% 14% 1	630
May	1st to 10th	Night	15% 5% 22% 44% 13% 2	630
	11th to 20th	Night	14% 5% 23% 35% 21% 2	621
	21st to end	Night	11% 2 15% 36% 30% 6%	683
June	1st to 10th	Night	7% 1 11% 41% 35% 5%	630
	11th to 20th	Night	5% 1 10% 37% 42% 6%	630
	21st to end	Night	5% 1 7% 33% 41% 12%	630
July	1st to 10th	Night	4 1 7% 26% 52% 11%	615
	11th to 20th	Night	7% 5% 25% 51% 12%	612
	21st to end	Night	5% 1 4 29% 46% 14%	687
August	1st to 10th	Night	4 1 4 26% 52% 14%	597
	11th to 20th	Night	6% 2 3 27% 50% 12%	594
	21st to end	Night	7% 2 6% 26% 46% 13%	660
September	1st to 10th	Night	9% 1 6% 36% 40% 7%	600
	11th to 20th	Night	10% 2 9% 30% 43% 7%	600
	21st to end	Night	10% 2 12% 34% 38% 5%	798
October	1st to 10th	Night	8% 3 14% 34% 36% 6%	800
	11th to 20th	Night	12% 4 21% 41% 22% 2	800
	21st to end	Night	17% 6% 21% 36% 19% 1	880
November	1st to 10th	Night	13% 5% 21% 38% 21% 2	820
	11th to 20th	Night	13% 6% 31% 35% 14% 1	840
	21st to end	Night	18% 7% 28% 32% 13% 2	840
December	1st to 10th	Night	20% 9% 30% 32% 8%	849
	11th to 20th	Night	20% 8% 31% 33% 8%	1050
	21st to end	Night	23% 10% 30% 30% 7%	1155

Page generated at 2026-07-28 02:25:26. Version ac07

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