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 2024-02-15.

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 5% 5% 3 5% 5% 5% 7% 44%	78508
	Night	13% 5% 2 5% 4 3 4 4 5% 7% 49%	80600
Transparency	Day	38% 7% 11% 21% 19% 5%	78232
	Night	35% 6% 10% 21% 21% 7%	80397
Seeing	Day	13% 6% 19% 24% 24% 13%	14169
	Night	15% 6% 22% 32% 22% 4	24104

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% 13% 3 6% 4 2 2 3 3 4 43%	2847
	11th to 20th	Day	22% 6% 3 5% 3 3 2 3 4 5% 43%	2850
	21st to end	Day	21% 8% 4 5% 4 2 3 3 3 4 42%	3135
February	1st to 10th	Day	19% 8% 3 5% 4 2 4 4 5% 5% 40%	1827
	11th to 20th	Day	23% 8% 3 5% 4 2 3 2 4 5% 40%	1788
	21st to end	Day	23% 8% 3 6% 5% 2 4 4 3 6% 36%	1480
March	1st to 10th	Day	16% 8% 3 7% 5% 3 4 4 5% 6% 39%	1898
	11th to 20th	Day	15% 7% 3 7% 5% 4 4 4 5% 6% 39%	1980
	21st to end	Day	12% 6% 3 6% 6% 3 5% 5% 5% 7% 41%	2260
April	1st to 10th	Day	12% 5% 2 6% 5% 4 5% 5% 5% 7% 45%	2160
	11th to 20th	Day	14% 6% 3 4 4 3 3 5% 6% 7% 45%	2134
	21st to end	Day	10% 6% 3 5% 5% 3 6% 4 4 8% 46%	2160
May	1st to 10th	Day	14% 4 3 6% 5% 3 4 5% 5% 6% 44%	2160
	11th to 20th	Day	10% 5% 3 5% 5% 4 6% 5% 7% 8% 40%	2124
	21st to end	Day	7% 4 2 6% 7% 4 6% 6% 8% 10% 39%	2602
June	1st to 10th	Day	7% 5% 2 6% 6% 4 6% 5% 7% 10% 43%	2520
	11th to 20th	Day	5% 3 2 4 4 4 6% 6% 6% 9% 49%	2520
	21st to end	Day	5% 5% 2 3 5% 3 5% 6% 7% 11% 48%	2520
July	1st to 10th	Day	6% 5% 3 5% 7% 5% 8% 7% 8% 12% 35%	2380
	11th to 20th	Day	9% 4 2 5% 5% 4 6% 6% 8% 11% 40%	2340
	21st to end	Day	6% 4 2 5% 6% 3 7% 7% 9% 11% 39%	2546
August	1st to 10th	Day	5% 3 2 4 7% 4 7% 7% 8% 10% 43%	2176
	11th to 20th	Day	8% 5% 2 6% 5% 5% 5% 7% 7% 9% 41%	2125
	21st to end	Day	10% 5% 2 4 5% 3 4 5% 6% 10% 45%	2376
September	1st to 10th	Day	8% 4 3 6% 5% 4 6% 5% 6% 7% 46%	2160
	11th to 20th	Day	10% 6% 2 6% 4 3 5% 4 5% 8% 46%	2142
	21st to end	Day	10% 4 1 4 4 2 4 4 4 6% 55%	1980
October	1st to 10th	Day	6% 4 2 4 4 2 4 4 5% 6% 60%	1805
	11th to 20th	Day	12% 4 2 3 3 2 3 3 4 6% 57%	1800
	21st to end	Day	16% 6% 2 4 4 2 3 3 4 5% 53%	1980
November	1st to 10th	Day	11% 4 2 4 4 2 3 3 3 5% 59%	1844
	11th to 20th	Day	11% 5% 2 5% 4 2 4 4 4 6% 53%	1710
	21st to end	Day	18% 7% 3 4 3 3 3 4 5% 6% 44%	1710
December	1st to 10th	Day	18% 9% 3 6% 5% 2 4 4 4 5% 40%	1698
	11th to 20th	Day	14% 9% 3 6% 5% 3 4 4 4 5% 42%	1918
	21st to end	Day	14% 6% 3 7% 6% 4 5% 5% 5% 6% 40%	2853
January	1st to 10th	Night	18% 8% 3 5% 5% 2 3 3 4 5% 44%	4108
	11th to 20th	Night	19% 6% 3 4 4 2 3 3 3 5% 48%	4120
	21st to end	Night	24% 8% 2 4 4 2 2 2 3 4 45%	4532
February	1st to 10th	Night	21% 7% 3 5% 4 3 3 3 4 6% 42%	2351
	11th to 20th	Night	19% 6% 3 5% 5% 2 3 4 3 5% 45%	2153
	21st to end	Night	21% 7% 2 6% 4 3 4 3 3 5% 41%	1776
March	1st to 10th	Night	14% 6% 3 4 5% 3 4 5% 4 6% 46%	2077
	11th to 20th	Night	15% 6% 3 5% 5% 3 4 5% 5% 9% 41%	1980
	21st to end	Night	16% 5% 3 5% 4 2 4 3 5% 6% 48%	2094
April	1st to 10th	Night	11% 4 3 5% 4 3 4 5% 7% 6% 49%	1800
	11th to 20th	Night	13% 5% 2 4 4 2 4 4 6% 8% 49%	1775
	21st to end	Night	11% 5% 2 5% 5% 3 4 4 4 7% 51%	1800
May	1st to 10th	Night	11% 4 3 4 3 2 3 4 5% 10% 51%	1800
	11th to 20th	Night	11% 5% 2 4 5% 3 5% 5% 6% 8% 46%	1769
	21st to end	Night	6% 3 2 4 5% 4 5% 5% 7% 11% 48%	1665
June	1st to 10th	Night	5% 3 2 5% 5% 3 5% 6% 6% 11% 48%	1440
	11th to 20th	Night	3 3 1 3 3 3 4 5% 8% 12% 55%	1440
	21st to end	Night	3 3 1 4 3 3 4 6% 8% 10% 54%	1440
July	1st to 10th	Night	4 3 2 5% 5% 4 7% 6% 8% 14% 43%	1573
	11th to 20th	Night	6% 3 2 4 4 2 6% 6% 7% 11% 49%	1620
	21st to end	Night	3 3 1 3 4 3 5% 6% 8% 13% 51%	1772
August	1st to 10th	Night	4 2 1 3 5% 3 5% 6% 6% 12% 53%	1762
	11th to 20th	Night	6% 4 2 5% 6% 4 4 5% 7% 10% 48%	1776
	21st to end	Night	7% 4 2 5% 5% 3 4 5% 5% 10% 50%	1980
September	1st to 10th	Night	7% 3 2 5% 5% 4 4 5% 5% 7% 53%	1800
	11th to 20th	Night	7% 5% 2 6% 5% 4 5% 4 6% 7% 50%	1800
	21st to end	Night	9% 3 2 3 3 2 4 4 5% 8% 56%	1978
October	1st to 10th	Night	8% 3 1 3 3 2 3 3 5% 6% 64%	2150
	11th to 20th	Night	11% 4 2 4 3 2 3 4 4 6% 57%	2160
	21st to end	Night	15% 6% 2 4 3 2 2 3 4 5% 54%	2376
November	1st to 10th	Night	10% 4 2 4 4 2 3 4 5% 6% 58%	2229
	11th to 20th	Night	11% 4 2 4 5% 2 3 3 4 6% 55%	2470
	21st to end	Night	15% 5% 2 4 4 3 4 4 4 6% 49%	2470
December	1st to 10th	Night	17% 8% 3 5% 4 2 4 4 4 6% 44%	2477
	11th to 20th	Night	16% 6% 2 5% 5% 2 4 3 3 5% 48%	3279
	21st to end	Night	15% 8% 3 6% 5% 3 5% 5% 5% 6% 39%	4808

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% 3 4 20% 23% 3	2848
	11th to 20th	Day	43% 5% 10% 21% 19% 2	2850
	21st to end	Day	47% 3 6% 19% 21% 4	3135
February	1st to 10th	Day	46% 4 7% 21% 16% 6%	1827
	11th to 20th	Day	49% 4 5% 20% 17% 6%	1798
	21st to end	Day	51% 4 6% 15% 17% 7%	1480
March	1st to 10th	Day	45% 5% 8% 16% 17% 9%	1898
	11th to 20th	Day	45% 6% 10% 18% 18% 3	1980
	21st to end	Day	42% 6% 10% 22% 19% 2	2260
April	1st to 10th	Day	38% 6% 10% 21% 20% 4	2160
	11th to 20th	Day	38% 6% 9% 20% 22% 5%	2134
	21st to end	Day	36% 7% 10% 22% 24% 2	2160
May	1st to 10th	Day	40% 7% 10% 20% 19% 4	2160
	11th to 20th	Day	38% 8% 14% 23% 15% 2	2128
	21st to end	Day	36% 10% 17% 24% 13% 1	2602
June	1st to 10th	Day	36% 8% 13% 24% 17% 1	2520
	11th to 20th	Day	29% 7% 15% 28% 17% 4	2520
	21st to end	Day	29% 8% 15% 24% 19% 4	2520
July	1st to 10th	Day	35% 13% 21% 19% 9% 3	2316
	11th to 20th	Day	32% 11% 19% 24% 11% 3	2271
	21st to end	Day	32% 11% 20% 26% 10% 1	2405
August	1st to 10th	Day	30% 11% 21% 28% 10% 1	2162
	11th to 20th	Day	36% 10% 16% 21% 13% 4	2125
	21st to end	Day	34% 8% 17% 24% 13% 4	2376
September	1st to 10th	Day	34% 9% 12% 20% 19% 6%	2160
	11th to 20th	Day	37% 7% 10% 16% 22% 8%	2142
	21st to end	Day	29% 6% 8% 22% 23% 12%	1980
October	1st to 10th	Day	25% 5% 9% 26% 23% 11%	1805
	11th to 20th	Day	29% 3 7% 21% 30% 10%	1800
	21st to end	Day	34% 5% 5% 20% 27% 9%	1980
November	1st to 10th	Day	30% 3 7% 20% 31% 9%	1844
	11th to 20th	Day	32% 4 7% 18% 28% 10%	1710
	21st to end	Day	42% 4 7% 19% 22% 6%	1710
December	1st to 10th	Day	47% 5% 6% 17% 18% 6%	1698
	11th to 20th	Day	44% 4 7% 16% 24% 5%	1915
	21st to end	Day	41% 7% 9% 18% 21% 4	2853
January	1st to 10th	Night	42% 4 6% 19% 26% 4	4108
	11th to 20th	Night	41% 4 6% 22% 21% 6%	4120
	21st to end	Night	44% 3 7% 20% 21% 5%	4532
February	1st to 10th	Night	45% 3 7% 18% 21% 6%	2351
	11th to 20th	Night	43% 3 7% 20% 19% 8%	2154
	21st to end	Night	47% 4 6% 14% 18% 10%	1776
March	1st to 10th	Night	38% 5% 7% 18% 19% 12%	2077
	11th to 20th	Night	39% 8% 11% 18% 17% 7%	1980
	21st to end	Night	37% 6% 8% 22% 23% 5%	2094
April	1st to 10th	Night	34% 6% 10% 22% 20% 8%	1800
	11th to 20th	Night	33% 5% 9% 20% 24% 9%	1775
	21st to end	Night	34% 5% 10% 22% 24% 5%	1800
May	1st to 10th	Night	30% 6% 12% 25% 23% 5%	1800
	11th to 20th	Night	34% 8% 14% 25% 17% 2	1770
	21st to end	Night	28% 9% 16% 27% 18% 2	1666
June	1st to 10th	Night	28% 9% 15% 27% 18% 3	1440
	11th to 20th	Night	19% 8% 16% 31% 20% 5%	1440
	21st to end	Night	23% 9% 14% 27% 22% 6%	1440
July	1st to 10th	Night	28% 11% 22% 24% 11% 4	1528
	11th to 20th	Night	24% 11% 24% 25% 12% 4	1566
	21st to end	Night	22% 10% 22% 30% 15% 1	1673
August	1st to 10th	Night	22% 9% 23% 33% 13% 1	1752
	11th to 20th	Night	30% 9% 18% 23% 15% 4	1776
	21st to end	Night	29% 8% 15% 25% 17% 5%	1980
September	1st to 10th	Night	30% 7% 12% 23% 20% 8%	1800
	11th to 20th	Night	33% 8% 8% 18% 25% 8%	1800
	21st to end	Night	26% 4 9% 23% 25% 11%	1978
October	1st to 10th	Night	21% 4 10% 24% 26% 14%	2150
	11th to 20th	Night	29% 4 6% 20% 28% 13%	2160
	21st to end	Night	34% 3 5% 19% 28% 11%	2376
November	1st to 10th	Night	28% 4 8% 19% 30% 11%	2229
	11th to 20th	Night	31% 4 7% 19% 26% 13%	2470
	21st to end	Night	37% 4 7% 19% 23% 9%	2470
December	1st to 10th	Night	42% 5% 8% 19% 20% 6%	2477
	11th to 20th	Night	40% 3 6% 18% 26% 7%	3281
	21st to end	Night	43% 7% 9% 18% 19% 4	4808

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% 15% 37% 19% 7% 1	270
	11th to 20th	Day	26% 15% 31% 21% 4 3	270
	21st to end	Day	20% 14% 39% 21% 6%	297
February	1st to 10th	Day	23% 12% 33% 21% 9% 1	270
	11th to 20th	Day	35% 15% 29% 16% 6%	252
	21st to end	Day	32% 15% 29% 17% 7%	198
March	1st to 10th	Day	23% 14% 34% 20% 9% 1	240
	11th to 20th	Day	20% 16% 38% 21% 5%	240
	21st to end	Day	17% 16% 34% 21% 11% 2	346
April	1st to 10th	Day	14% 13% 30% 31% 10% 1	420
	11th to 20th	Day	18% 11% 29% 28% 11% 3	412
	21st to end	Day	15% 9% 27% 28% 19% 2	420
May	1st to 10th	Day	13% 9% 26% 31% 19% 2	423
	11th to 20th	Day	13% 3 23% 28% 23% 11%	447
	21st to end	Day	8% 4 16% 31% 26% 15%	604
June	1st to 10th	Day	11% 2 10% 28% 32% 17%	630
	11th to 20th	Day	5% 1 11% 30% 36% 17%	630
	21st to end	Day	7% 3 10% 28% 33% 19%	630
July	1st to 10th	Day	6% 1 8% 22% 38% 25%	621
	11th to 20th	Day	8% 2 6% 20% 33% 31%	618
	21st to end	Day	6% 1 5% 22% 37% 30%	684
August	1st to 10th	Day	7% 1 6% 16% 40% 29%	474
	11th to 20th	Day	9% 2 4 20% 43% 23%	439
	21st to end	Day	15% 1 4 15% 34% 32%	495
September	1st to 10th	Day	9% 1 5% 24% 38% 22%	450
	11th to 20th	Day	10% 2 8% 22% 33% 25%	450
	21st to end	Day	13% 3 8% 28% 32% 16%	450
October	1st to 10th	Day	7% 3 20% 27% 24% 19%	275
	11th to 20th	Day	11% 5% 28% 31% 21% 4	270
	21st to end	Day	19% 7% 27% 28% 16% 4	297
November	1st to 10th	Day	17% 6% 23% 27% 23% 4	270
	11th to 20th	Day	11% 9% 36% 29% 13% 1	270
	21st to end	Day	21% 13% 27% 21% 13% 4	270
December	1st to 10th	Day	18% 13% 34% 24% 9% 1	270
	11th to 20th	Day	19% 12% 35% 21% 10% 2	270
	21st to end	Day	21% 16% 33% 23% 7% 1	297
January	1st to 10th	Night	21% 11% 32% 29% 6%	950
	11th to 20th	Night	23% 11% 32% 27% 6%	950
	21st to end	Night	23% 9% 36% 29% 3	1045
February	1st to 10th	Night	24% 10% 31% 29% 5%	831
	11th to 20th	Night	22% 11% 34% 29% 3	722
	21st to end	Night	24% 13% 34% 27% 3	592
March	1st to 10th	Night	17% 9% 31% 36% 7%	637
	11th to 20th	Night	16% 12% 30% 32% 8% 1	540
	21st to end	Night	20% 7% 31% 29% 12% 1	594
April	1st to 10th	Night	13% 7% 35% 34% 10% 1	540
	11th to 20th	Night	16% 7% 31% 33% 13% 2	533
	21st to end	Night	12% 7% 31% 34% 14% 1	540
May	1st to 10th	Night	13% 4 22% 45% 14% 2	540
	11th to 20th	Night	12% 4 22% 37% 24% 2	531
	21st to end	Night	9% 2 13% 35% 34% 7%	584
June	1st to 10th	Night	6% 1 10% 39% 38% 6%	540
	11th to 20th	Night	3 1 9% 35% 46% 6%	540
	21st to end	Night	5% 1 7% 34% 40% 13%	540
July	1st to 10th	Night	3 1 6% 27% 52% 11%	525
	11th to 20th	Night	6% 6% 24% 51% 13%	522
	21st to end	Night	3 1 5% 30% 46% 15%	591
August	1st to 10th	Night	5% 1 4 23% 52% 16%	537
	11th to 20th	Night	7% 2 3 27% 49% 12%	534
	21st to end	Night	7% 2 5% 24% 47% 15%	594
September	1st to 10th	Night	9% 1 5% 35% 42% 8%	540
	11th to 20th	Night	9% 1 9% 29% 43% 8%	540
	21st to end	Night	11% 1 10% 34% 39% 5%	718
October	1st to 10th	Night	8% 3 14% 32% 37% 6%	720
	11th to 20th	Night	13% 3 22% 40% 21% 2	720
	21st to end	Night	17% 6% 21% 35% 20% 1	792
November	1st to 10th	Night	11% 5% 21% 38% 21% 3	740
	11th to 20th	Night	13% 7% 31% 34% 14% 1	760
	21st to end	Night	18% 7% 28% 32% 14% 2	760
December	1st to 10th	Night	20% 9% 29% 33% 9%	767
	11th to 20th	Night	21% 8% 30% 32% 9%	950
	21st to end	Night	23% 10% 30% 30% 7%	1045

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