Oklahoma Christian University Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Oklahoma Christian University Observatory clear sky chart from 2005-11-06 to 2024-11-01.

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	9% 6% 2 5% 4 3 4 3 5% 7% 52%	101156
	Night	9% 5% 2 4 3 3 3 3 5% 7% 57%	97893
Transparency	Day	32% 5% 11% 26% 22% 6%	100970
	Night	28% 4 10% 25% 24% 8%	97750
Seeing	Day	12% 10% 28% 30% 17% 4	15381
	Night	11% 10% 33% 33% 11% 1	25230

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% 8% 3 8% 5% 4 4 3 5% 6% 47%	2847
	11th to 20th	Day	8% 6% 2 4 3 3 3 3 5% 6% 59%	2850
	21st to end	Day	16% 9% 4 5% 3 2 2 3 3 5% 48%	3135
February	1st to 10th	Day	10% 11% 3 7% 3 3 3 3 4 5% 48%	1786
	11th to 20th	Day	10% 8% 2 6% 4 4 3 3 4 5% 51%	1849
	21st to end	Day	11% 9% 3 5% 3 3 2 3 4 6% 51%	1570
March	1st to 10th	Day	10% 6% 2 4 3 3 2 3 4 5% 57%	3371
	11th to 20th	Day	9% 6% 2 5% 3 3 4 3 4 6% 54%	3480
	21st to end	Day	13% 11% 3 7% 5% 3 4 3 5% 6% 39%	3814
April	1st to 10th	Day	8% 5% 2 5% 4 4 4 4 5% 7% 53%	2090
	11th to 20th	Day	12% 5% 3 7% 4 4 5% 3 5% 6% 47%	2252
	21st to end	Day	14% 6% 1 5% 4 3 4 3 5% 6% 47%	2470
May	1st to 10th	Day	17% 8% 3 7% 4 4 3 3 4 6% 42%	4082
	11th to 20th	Day	10% 6% 2 6% 4 4 4 4 6% 6% 49%	4082
	21st to end	Day	12% 7% 2 7% 5% 5% 4 4 6% 7% 42%	4477
June	1st to 10th	Day	5% 5% 2 5% 3 4 4 4 7% 10% 50%	2470
	11th to 20th	Day	6% 3 1 5% 4 4 4 4 6% 10% 54%	2470
	21st to end	Day	4 3 1 3 3 4 4 4 7% 8% 59%	2470
July	1st to 10th	Day	8% 4 2 5% 4 5% 4 4 6% 9% 49%	4120
	11th to 20th	Day	5% 4 2 4 3 4 4 3 6% 9% 56%	4120
	21st to end	Day	4 3 1 4 3 3 4 4 6% 10% 58%	4465
August	1st to 10th	Day	5% 3 1 5% 3 4 4 4 6% 10% 55%	4104
	11th to 20th	Day	6% 4 2 4 3 4 4 4 6% 10% 53%	4041
	21st to end	Day	3 3 1 4 3 3 4 4 5% 7% 62%	4228
September	1st to 10th	Day	10% 4 1 4 4 3 3 4 4 6% 56%	2090
	11th to 20th	Day	10% 5% 2 6% 4 4 5% 3 4 7% 49%	2090
	21st to end	Day	8% 3 1 4 3 3 4 4 5% 6% 59%	2090
October	1st to 10th	Day	8% 4 2 4 3 3 3 3 4 5% 63%	2051
	11th to 20th	Day	10% 3 1 3 2 2 2 2 3 5% 68%	1900
	21st to end	Day	11% 5% 2 5% 3 3 3 2 3 4 59%	2090
November	1st to 10th	Day	7% 4 2 3 3 3 3 3 5% 6% 62%	1776
	11th to 20th	Day	7% 5% 1 3 3 2 2 2 3 5% 66%	1710
	21st to end	Day	11% 6% 2 4 3 3 2 3 4 6% 57%	1710
December	1st to 10th	Day	9% 7% 2 5% 3 3 3 3 4 6% 55%	1710
	11th to 20th	Day	12% 5% 2 6% 4 4 4 3 5% 4 51%	2161
	21st to end	Day	9% 10% 3 8% 4 4 4 4 5% 6% 43%	3135
January	1st to 10th	Night	10% 9% 3 6% 4 3 3 2 4 4 51%	4108
	11th to 20th	Night	6% 4 1 4 3 3 3 3 5% 7% 59%	4120
	21st to end	Night	17% 9% 3 4 2 2 2 2 4 4 52%	4532
February	1st to 10th	Night	13% 8% 2 6% 3 3 2 2 4 5% 51%	2410
	11th to 20th	Night	11% 7% 2 5% 2 3 3 3 4 5% 54%	2218
	21st to end	Night	11% 7% 3 5% 3 3 3 3 4 5% 53%	1884
March	1st to 10th	Night	8% 7% 2 5% 3 3 4 3 4 5% 56%	3484
	11th to 20th	Night	10% 6% 2 3 2 3 2 2 4 5% 61%	3480
	21st to end	Night	10% 6% 2 5% 3 4 4 4 5% 7% 49%	3817
April	1st to 10th	Night	9% 4 1 4 3 3 3 4 4 7% 57%	2090
	11th to 20th	Night	12% 4 2 4 3 3 3 3 5% 7% 53%	1874
	21st to end	Night	12% 6% 2 4 3 3 2 3 4 6% 54%	1710
May	1st to 10th	Night	16% 7% 2 5% 3 3 3 2 5% 6% 48%	2823
	11th to 20th	Night	12% 6% 2 5% 3 5% 4 3 5% 8% 46%	2823
	21st to end	Night	7% 4 2 5% 4 4 4 4 6% 8% 54%	3090
June	1st to 10th	Night	5% 3 1 3 3 3 4 4 6% 10% 59%	1710
	11th to 20th	Night	4 4 1 5% 3 3 4 4 6% 10% 57%	1710
	21st to end	Night	4 2 1 2 2 3 4 3 5% 10% 64%	1710
July	1st to 10th	Night	6% 4 2 5% 4 4 4 3 6% 10% 52%	2850
	11th to 20th	Night	2 2 1 3 3 3 4 4 6% 9% 63%	2850
	21st to end	Night	4 3 1 2 2 3 2 3 5% 9% 65%	3098
August	1st to 10th	Night	1 2 1 3 3 3 4 4 6% 11% 63%	2836
	11th to 20th	Night	5% 3 1 4 4 4 5% 4 6% 10% 55%	2798
	21st to end	Night	2 2 1 3 3 2 3 4 6% 10% 64%	3416
September	1st to 10th	Night	8% 4 1 3 3 3 3 3 4 6% 61%	2090
	11th to 20th	Night	10% 5% 2 6% 3 3 4 2 4 6% 55%	2090
	21st to end	Night	6% 3 2 4 3 2 3 3 5% 6% 62%	2090
October	1st to 10th	Night	6% 3 1 4 3 3 3 3 5% 5% 63%	2109
	11th to 20th	Night	9% 4 2 4 2 2 2 3 3 4 65%	2280
	21st to end	Night	10% 4 1 4 2 2 3 2 4 5% 62%	2508
November	1st to 10th	Night	7% 4 1 2 2 3 2 3 4 5% 66%	2307
	11th to 20th	Night	7% 4 2 5% 3 3 3 3 3 5% 63%	2470
	21st to end	Night	10% 6% 2 4 3 3 3 2 4 6% 56%	2470
December	1st to 10th	Night	10% 5% 2 4 3 3 3 2 5% 7% 58%	2470
	11th to 20th	Night	9% 6% 2 5% 4 4 3 3 4 5% 54%	3036
	21st to end	Night	13% 7% 2 5% 3 3 3 2 5% 6% 50%	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	38% 4 8% 22% 23% 4	2848
	11th to 20th	Day	26% 3 12% 26% 27% 5%	2850
	21st to end	Day	41% 3 6% 23% 23% 4	3135
February	1st to 10th	Day	40% 3 9% 22% 21% 5%	1786
	11th to 20th	Day	36% 3 8% 26% 21% 5%	1859
	21st to end	Day	36% 4 6% 20% 25% 9%	1570
March	1st to 10th	Day	31% 3 7% 19% 26% 15%	3371
	11th to 20th	Day	32% 5% 10% 24% 24% 5%	3480
	21st to end	Day	44% 5% 9% 23% 15% 4	3814
April	1st to 10th	Day	31% 5% 11% 25% 20% 8%	2090
	11th to 20th	Day	37% 6% 10% 20% 20% 8%	2252
	21st to end	Day	38% 6% 9% 26% 20% 3	2470
May	1st to 10th	Day	44% 5% 10% 18% 18% 5%	4120
	11th to 20th	Day	35% 7% 14% 26% 17% 2	4086
	21st to end	Day	41% 7% 11% 19% 16% 6%	4489
June	1st to 10th	Day	27% 9% 18% 27% 15% 4	2470
	11th to 20th	Day	26% 6% 14% 29% 21% 4	2470
	21st to end	Day	23% 6% 15% 27% 24% 6%	2470
July	1st to 10th	Day	31% 5% 14% 27% 18% 4	4056
	11th to 20th	Day	25% 3 10% 33% 26% 3	4051
	21st to end	Day	22% 4 16% 33% 24% 1	4325
August	1st to 10th	Day	25% 4 10% 27% 24% 9%	4090
	11th to 20th	Day	27% 4 16% 33% 17% 3	4080
	21st to end	Day	22% 5% 12% 43% 15% 3	4227
September	1st to 10th	Day	29% 4 10% 24% 24% 10%	2090
	11th to 20th	Day	34% 6% 9% 22% 24% 6%	2090
	21st to end	Day	26% 5% 8% 24% 30% 7%	2090
October	1st to 10th	Day	25% 5% 10% 22% 30% 9%	2051
	11th to 20th	Day	22% 3 7% 21% 34% 13%	1900
	21st to end	Day	31% 3 7% 24% 23% 11%	2090
November	1st to 10th	Day	24% 4 8% 26% 28% 10%	1776
	11th to 20th	Day	23% 2 8% 29% 27% 10%	1710
	21st to end	Day	29% 3 7% 25% 25% 10%	1710
December	1st to 10th	Day	32% 4 10% 27% 24% 3	1710
	11th to 20th	Day	36% 3 8% 20% 27% 6%	2159
	21st to end	Day	41% 4 8% 22% 22% 3	3135
January	1st to 10th	Night	36% 5% 6% 23% 25% 5%	4108
	11th to 20th	Night	24% 5% 16% 23% 27% 6%	4120
	21st to end	Night	38% 3 7% 20% 26% 6%	4532
February	1st to 10th	Night	37% 4 8% 22% 23% 6%	2410
	11th to 20th	Night	33% 4 8% 26% 22% 8%	2218
	21st to end	Night	35% 4 5% 19% 24% 13%	1884
March	1st to 10th	Night	32% 4 7% 18% 23% 17%	3484
	11th to 20th	Night	26% 4 8% 32% 23% 7%	3480
	21st to end	Night	35% 6% 11% 28% 18% 3	3817
April	1st to 10th	Night	27% 5% 10% 22% 23% 13%	2090
	11th to 20th	Night	30% 5% 11% 24% 19% 11%	1874
	21st to end	Night	33% 5% 10% 26% 23% 4	1710
May	1st to 10th	Night	38% 6% 9% 20% 21% 6%	2850
	11th to 20th	Night	37% 6% 12% 27% 17% 2	2824
	21st to end	Night	28% 7% 14% 23% 20% 9%	3099
June	1st to 10th	Night	20% 7% 22% 30% 18% 3	1710
	11th to 20th	Night	22% 6% 15% 29% 22% 6%	1710
	21st to end	Night	16% 5% 13% 32% 25% 8%	1710
July	1st to 10th	Night	29% 4 13% 32% 18% 3	2805
	11th to 20th	Night	17% 4 9% 36% 29% 4	2796
	21st to end	Night	18% 4 14% 34% 28% 3	2999
August	1st to 10th	Night	16% 4 13% 27% 31% 8%	2826
	11th to 20th	Night	25% 4 12% 31% 24% 4	2825
	21st to end	Night	16% 4 15% 40% 21% 4	3416
September	1st to 10th	Night	26% 3 9% 25% 26% 12%	2090
	11th to 20th	Night	31% 5% 9% 20% 26% 9%	2090
	21st to end	Night	23% 4 8% 25% 31% 9%	2090
October	1st to 10th	Night	23% 4 11% 21% 28% 13%	2109
	11th to 20th	Night	24% 3 6% 18% 34% 16%	2280
	21st to end	Night	27% 3 7% 24% 28% 12%	2508
November	1st to 10th	Night	22% 3 9% 22% 31% 13%	2307
	11th to 20th	Night	26% 3 7% 24% 30% 10%	2470
	21st to end	Night	31% 3 6% 21% 28% 11%	2470
December	1st to 10th	Night	28% 4 10% 27% 25% 7%	2470
	11th to 20th	Night	34% 3 7% 22% 28% 7%	3037
	21st to end	Night	35% 4 8% 23% 22% 8%	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	16% 17% 38% 21% 8%	270
	11th to 20th	Day	20% 20% 39% 19% 2 1	270
	21st to end	Day	14% 19% 41% 21% 4 1	297
February	1st to 10th	Day	20% 19% 41% 17% 4	270
	11th to 20th	Day	17% 23% 43% 15% 2	270
	21st to end	Day	24% 25% 37% 12% 2	225
March	1st to 10th	Day	17% 22% 36% 19% 5%	270
	11th to 20th	Day	24% 23% 34% 16% 3	270
	21st to end	Day	21% 22% 37% 17% 3 1	297
April	1st to 10th	Day	19% 20% 37% 20% 4	270
	11th to 20th	Day	18% 21% 40% 17% 3	450
	21st to end	Day	20% 17% 34% 21% 6% 1	650
May	1st to 10th	Day	14% 14% 43% 23% 5% 1	653
	11th to 20th	Day	15% 11% 31% 27% 14% 2	675
	21st to end	Day	11% 10% 31% 28% 16% 3	734
June	1st to 10th	Day	7% 6% 21% 40% 22% 5%	680
	11th to 20th	Day	6% 2 31% 41% 16% 4	680
	21st to end	Day	3 2 27% 44% 20% 4	680
July	1st to 10th	Day	6% 2 13% 37% 33% 8%	671
	11th to 20th	Day	4 1 15% 44% 31% 5%	668
	21st to end	Day	7% 1 7% 39% 35% 11%	739
August	1st to 10th	Day	6% 1 12% 43% 32% 5%	676
	11th to 20th	Day	8% 2 15% 39% 29% 7%	665
	21st to end	Day	4 2 12% 38% 36% 8%	574
September	1st to 10th	Day	8% 3 11% 36% 32% 10%	300
	11th to 20th	Day	7% 3 15% 38% 30% 7%	300
	21st to end	Day	11% 5% 18% 39% 21% 6%	300
October	1st to 10th	Day	8% 6% 29% 32% 17% 8%	300
	11th to 20th	Day	10% 13% 35% 32% 9% 1	300
	21st to end	Day	20% 12% 33% 23% 8% 3	330
November	1st to 10th	Day	13% 15% 36% 27% 7% 2	270
	11th to 20th	Day	16% 14% 37% 23% 9% 2	270
	21st to end	Day	17% 21% 36% 21% 4	270
December	1st to 10th	Day	13% 16% 41% 21% 9%	270
	11th to 20th	Day	19% 16% 39% 17% 9%	270
	21st to end	Day	18% 23% 36% 20% 3	297
January	1st to 10th	Night	11% 13% 40% 29% 6% 1	950
	11th to 20th	Night	14% 14% 39% 29% 5%	950
	21st to end	Night	13% 14% 38% 31% 5%	1045
February	1st to 10th	Night	17% 15% 39% 25% 4	890
	11th to 20th	Night	16% 16% 40% 24% 3	744
	21st to end	Night	17% 16% 40% 25% 3	628
March	1st to 10th	Night	11% 14% 40% 31% 3	613
	11th to 20th	Night	19% 12% 39% 27% 3	570
	21st to end	Night	16% 16% 40% 23% 5%	627
April	1st to 10th	Night	12% 17% 43% 22% 6%	570
	11th to 20th	Night	15% 15% 45% 21% 4	563
	21st to end	Night	16% 14% 37% 27% 6%	570
May	1st to 10th	Night	11% 12% 46% 25% 6%	570
	11th to 20th	Night	13% 7% 38% 27% 14% 1	561
	21st to end	Night	8% 7% 34% 34% 15% 1	617
June	1st to 10th	Night	6% 4 25% 45% 17% 2	570
	11th to 20th	Night	5% 5% 34% 45% 11% 1	570
	21st to end	Night	3 2 31% 44% 18% 2	570
July	1st to 10th	Night	6% 1 18% 46% 27% 3	555
	11th to 20th	Night	3 1 16% 53% 25% 2	552
	21st to end	Night	5% 1 11% 53% 27% 2	624
August	1st to 10th	Night	2 1 16% 51% 27% 2	567
	11th to 20th	Night	7% 1 18% 46% 27% 1	564
	21st to end	Night	3 12% 46% 34% 3	627
September	1st to 10th	Night	9% 2 19% 45% 23% 2	570
	11th to 20th	Night	11% 2 24% 38% 22% 2	570
	21st to end	Night	8% 4 25% 43% 17% 4	570
October	1st to 10th	Night	8% 4 31% 34% 20% 3	589
	11th to 20th	Night	12% 8% 38% 31% 10% 1	760
	21st to end	Night	14% 13% 33% 29% 10% 1	836
November	1st to 10th	Night	10% 9% 40% 29% 11% 1	823
	11th to 20th	Night	10% 13% 38% 30% 9%	950
	21st to end	Night	14% 14% 35% 30% 7%	950
December	1st to 10th	Night	13% 11% 36% 31% 7%	950
	11th to 20th	Night	16% 12% 39% 26% 6%	950
	21st to end	Night	15% 14% 37% 29% 5%	1045

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