Owasso Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Owasso Observatory clear sky chart from 2005-11-06 to 2025-05-11.

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	11% 6% 2 5% 4 4 4 3 5% 7% 49%	114544
	Night	11% 6% 2 5% 3 3 3 3 5% 6% 54%	114624
Transparency	Day	34% 6% 11% 25% 20% 5%	118236
	Night	30% 5% 10% 25% 23% 7%	119060
Seeing	Day	13% 10% 27% 28% 18% 4	16080
	Night	13% 9% 31% 33% 13% 1	26062

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	14% 10% 4 7% 3 3 3 3 3 5% 44%	4077
	11th to 20th	Day	7% 6% 2 6% 4 4 3 3 5% 5% 55%	4080
	21st to end	Day	18% 10% 3 5% 2 3 3 2 3 4 48%	4488
February	1st to 10th	Day	15% 10% 3 7% 4 3 3 3 4 6% 42%	1800
	11th to 20th	Day	15% 7% 2 6% 4 4 4 2 5% 5% 46%	1884
	21st to end	Day	14% 8% 2 5% 5% 4 4 2 4 6% 46%	1693
March	1st to 10th	Day	11% 7% 2 5% 3 3 3 3 3 5% 54%	4936
	11th to 20th	Day	8% 6% 2 4 3 4 3 3 5% 7% 56%	4980
	21st to end	Day	12% 8% 3 8% 5% 5% 5% 4 6% 8% 38%	5462
April	1st to 10th	Day	12% 6% 2 6% 4 4 4 4 5% 6% 47%	2215
	11th to 20th	Day	15% 6% 2 6% 4 4 3 4 5% 7% 45%	2374
	21st to end	Day	19% 7% 2 6% 4 4 4 3 4 6% 40%	2560
May	1st to 10th	Day	20% 9% 3 6% 4 4 4 3 4 5% 38%	4212
	11th to 20th	Day	11% 7% 3 6% 4 4 5% 4 6% 7% 43%	4083
	21st to end	Day	14% 7% 3 6% 5% 5% 5% 4 7% 8% 36%	4477
June	1st to 10th	Day	6% 4 2 5% 5% 4 5% 4 6% 10% 49%	2470
	11th to 20th	Day	8% 4 2 6% 5% 5% 4 4 6% 8% 50%	2470
	21st to end	Day	6% 2 1 4 3 3 5% 4 6% 8% 59%	2470
July	1st to 10th	Day	9% 5% 2 5% 5% 4 5% 5% 7% 10% 44%	4120
	11th to 20th	Day	5% 4 2 5% 3 4 4 3 6% 9% 55%	4120
	21st to end	Day	5% 4 2 5% 5% 5% 5% 5% 7% 11% 48%	4465
August	1st to 10th	Day	5% 4 2 4 3 3 4 4 6% 9% 57%	4104
	11th to 20th	Day	6% 4 2 5% 4 4 5% 5% 7% 10% 48%	4041
	21st to end	Day	4 4 1 5% 4 4 4 4 6% 9% 56%	4291
September	1st to 10th	Day	11% 5% 1 5% 4 3 4 3 5% 6% 53%	2151
	11th to 20th	Day	12% 4 2 6% 3 4 4 4 5% 8% 49%	2090
	21st to end	Day	9% 3 1 5% 3 4 4 3 5% 7% 56%	2090
October	1st to 10th	Day	9% 4 1 4 3 3 3 3 5% 7% 58%	1959
	11th to 20th	Day	11% 4 1 3 2 2 3 2 4 5% 62%	1900
	21st to end	Day	16% 6% 2 4 2 3 3 2 3 5% 54%	2090
November	1st to 10th	Day	11% 5% 2 4 2 3 3 3 4 6% 58%	1958
	11th to 20th	Day	11% 5% 1 4 2 3 3 2 4 5% 59%	1815
	21st to end	Day	14% 7% 2 4 2 2 3 2 4 6% 54%	1800
December	1st to 10th	Day	10% 8% 2 5% 3 3 2 3 4 5% 54%	2940
	11th to 20th	Day	12% 7% 2 6% 3 3 3 3 4 5% 52%	3391
	21st to end	Day	20% 15% 5% 7% 4 4 4 2 3 4 33%	4488
January	1st to 10th	Night	14% 7% 3 6% 4 2 3 3 5% 6% 47%	5888
	11th to 20th	Night	6% 4 2 5% 4 3 3 3 5% 7% 58%	5900
	21st to end	Night	17% 8% 2 5% 3 3 2 2 3 5% 49%	6490
February	1st to 10th	Night	15% 9% 2 6% 4 3 3 3 5% 5% 46%	2600
	11th to 20th	Night	14% 8% 3 6% 3 2 3 2 4 6% 50%	2421
	21st to end	Night	13% 7% 2 5% 4 4 4 3 4 4 51%	1935
March	1st to 10th	Night	14% 7% 2 6% 3 3 3 2 4 4 52%	4919
	11th to 20th	Night	7% 4 2 3 2 2 3 3 4 7% 62%	4980
	21st to end	Night	11% 5% 2 6% 4 4 4 3 5% 8% 48%	5467
April	1st to 10th	Night	12% 5% 2 4 3 4 3 3 4 6% 54%	2183
	11th to 20th	Night	14% 4 2 5% 4 3 2 3 4 6% 51%	1975
	21st to end	Night	15% 6% 2 6% 4 3 3 2 5% 6% 48%	1836
May	1st to 10th	Night	16% 7% 3 6% 4 3 3 4 5% 7% 43%	2913
	11th to 20th	Night	15% 7% 3 6% 3 4 3 3 4 7% 46%	2828
	21st to end	Night	11% 5% 2 5% 4 3 3 3 6% 10% 47%	3090
June	1st to 10th	Night	5% 4 1 5% 4 4 4 3 7% 7% 56%	1710
	11th to 20th	Night	4 3 1 3 3 3 4 4 8% 10% 56%	1710
	21st to end	Night	3 3 1 3 3 3 4 4 5% 8% 64%	1710
July	1st to 10th	Night	8% 5% 2 4 3 3 4 4 6% 10% 51%	2850
	11th to 20th	Night	3 2 1 4 3 3 4 3 5% 10% 62%	2850
	21st to end	Night	6% 3 1 4 3 3 4 4 6% 8% 58%	3098
August	1st to 10th	Night	2 2 1 4 3 3 4 3 7% 9% 62%	2836
	11th to 20th	Night	5% 4 1 5% 4 5% 5% 4 7% 8% 52%	2798
	21st to end	Night	2 3 1 4 2 3 4 3 6% 9% 63%	3366
September	1st to 10th	Night	8% 4 1 4 3 3 3 3 4 7% 60%	2024
	11th to 20th	Night	9% 5% 2 6% 4 4 4 4 5% 7% 52%	2090
	21st to end	Night	7% 4 2 4 3 3 3 3 4 5% 60%	2090
October	1st to 10th	Night	7% 4 1 3 3 3 3 2 5% 6% 63%	2200
	11th to 20th	Night	11% 5% 1 3 2 2 3 2 3 5% 61%	2280
	21st to end	Night	13% 5% 2 4 3 3 3 2 4 4 57%	2508
November	1st to 10th	Night	11% 5% 1 3 2 2 2 3 4 4 62%	2340
	11th to 20th	Night	10% 5% 2 4 2 2 3 3 4 6% 59%	2583
	21st to end	Night	13% 5% 1 4 3 3 3 2 4 6% 56%	2600
December	1st to 10th	Night	9% 6% 2 5% 2 3 3 2 4 6% 58%	4250
	11th to 20th	Night	15% 6% 2 5% 3 3 3 2 3 4 54%	4816
	21st to end	Night	19% 11% 3 6% 3 3 3 2 3 5% 42%	6490

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	43% 3 11% 25% 16% 2	4078
	11th to 20th	Day	30% 4 12% 25% 23% 5%	4080
	21st to end	Day	42% 2 7% 21% 25% 4	4488
February	1st to 10th	Day	44% 5% 10% 23% 14% 4	1800
	11th to 20th	Day	40% 4 9% 26% 17% 3	1893
	21st to end	Day	40% 3 8% 22% 18% 9%	1693
March	1st to 10th	Day	33% 4 6% 21% 20% 17%	4936
	11th to 20th	Day	29% 5% 9% 20% 21% 16%	4980
	21st to end	Day	43% 7% 10% 29% 10% 1	5464
April	1st to 10th	Day	36% 5% 12% 23% 18% 5%	2215
	11th to 20th	Day	39% 6% 12% 22% 17% 5%	2374
	21st to end	Day	46% 5% 10% 22% 16% 2	2560
May	1st to 10th	Day	47% 6% 9% 21% 15% 3	4250
	11th to 20th	Day	37% 9% 13% 23% 17% 1	4087
	21st to end	Day	43% 9% 13% 19% 12% 3	4489
June	1st to 10th	Day	30% 8% 17% 26% 16% 2	2470
	11th to 20th	Day	32% 7% 15% 27% 17% 3	2470
	21st to end	Day	23% 7% 16% 29% 20% 5%	2470
July	1st to 10th	Day	32% 8% 16% 26% 15% 3	4056
	11th to 20th	Day	24% 7% 12% 33% 22% 3	4051
	21st to end	Day	26% 9% 18% 31% 15% 1	4325
August	1st to 10th	Day	22% 7% 13% 27% 25% 6%	4090
	11th to 20th	Day	29% 8% 20% 24% 17% 2	4080
	21st to end	Day	25% 7% 13% 37% 14% 3	4290
September	1st to 10th	Day	31% 5% 10% 22% 23% 9%	2151
	11th to 20th	Day	33% 6% 12% 21% 21% 5%	2090
	21st to end	Day	28% 5% 10% 23% 28% 7%	2090
October	1st to 10th	Day	17% 5% 8% 16% 42% 13%	3258
	11th to 20th	Day	16% 2 5% 22% 40% 15%	3140
	21st to end	Day	27% 3 7% 28% 28% 6%	3428
November	1st to 10th	Day	29% 3 8% 27% 25% 7%	1958
	11th to 20th	Day	29% 3 10% 27% 24% 8%	1815
	21st to end	Day	33% 4 8% 25% 25% 5%	1800
December	1st to 10th	Day	33% 3 8% 35% 19% 1	2940
	11th to 20th	Day	35% 4 6% 26% 27% 3	3389
	21st to end	Day	55% 4 7% 21% 10% 2	4488
January	1st to 10th	Night	38% 5% 12% 27% 15% 3	5888
	11th to 20th	Night	25% 5% 14% 21% 30% 5%	5900
	21st to end	Night	40% 3 8% 19% 27% 4	6490
February	1st to 10th	Night	41% 4 12% 22% 17% 4	2600
	11th to 20th	Night	38% 4 9% 26% 19% 5%	2421
	21st to end	Night	37% 4 7% 19% 24% 9%	1935
March	1st to 10th	Night	37% 4 6% 20% 21% 12%	4919
	11th to 20th	Night	23% 3 8% 23% 27% 15%	4980
	21st to end	Night	34% 5% 12% 32% 15% 2	5467
April	1st to 10th	Night	32% 5% 10% 22% 21% 9%	2183
	11th to 20th	Night	34% 5% 11% 23% 20% 8%	1975
	21st to end	Night	38% 5% 11% 24% 20% 3	1836
May	1st to 10th	Night	40% 7% 12% 18% 19% 4	2940
	11th to 20th	Night	38% 7% 12% 25% 16% 1	2829
	21st to end	Night	30% 8% 17% 26% 17% 1	3099
June	1st to 10th	Night	25% 8% 16% 29% 19% 3	1710
	11th to 20th	Night	21% 7% 15% 32% 22% 3	1710
	21st to end	Night	18% 6% 14% 30% 25% 6%	1710
July	1st to 10th	Night	27% 7% 18% 27% 17% 5%	2805
	11th to 20th	Night	18% 5% 11% 36% 27% 3	2796
	21st to end	Night	22% 7% 15% 35% 20% 1	2999
August	1st to 10th	Night	16% 6% 15% 31% 25% 7%	2826
	11th to 20th	Night	27% 7% 17% 25% 19% 4	2825
	21st to end	Night	17% 6% 12% 40% 19% 5%	3366
September	1st to 10th	Night	26% 4 10% 26% 24% 11%	2024
	11th to 20th	Night	31% 7% 10% 20% 25% 6%	2090
	21st to end	Night	25% 5% 9% 24% 30% 7%	2090
October	1st to 10th	Night	14% 3 7% 14% 38% 24%	3668
	11th to 20th	Night	19% 3 5% 18% 36% 18%	3779
	21st to end	Night	27% 4 7% 26% 27% 9%	4120
November	1st to 10th	Night	26% 4 8% 24% 29% 8%	2340
	11th to 20th	Night	27% 4 7% 26% 27% 9%	2583
	21st to end	Night	32% 4 8% 24% 27% 6%	2600
December	1st to 10th	Night	29% 4 10% 38% 17% 3	4250
	11th to 20th	Night	36% 3 6% 23% 26% 6%	4817
	21st to end	Night	46% 5% 7% 25% 13% 4	6490

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% 13% 36% 25% 5%	300
	11th to 20th	Day	22% 18% 39% 17% 5%	300
	21st to end	Day	17% 18% 38% 20% 7%	330
February	1st to 10th	Day	26% 14% 37% 19% 5%	300
	11th to 20th	Day	21% 21% 39% 16% 2	300
	21st to end	Day	24% 19% 37% 16% 5%	249
March	1st to 10th	Day	18% 23% 34% 20% 4 1	300
	11th to 20th	Day	22% 20% 39% 16% 3	300
	21st to end	Day	21% 22% 35% 18% 4 1	330
April	1st to 10th	Day	16% 23% 39% 17% 5%	315
	11th to 20th	Day	21% 18% 36% 21% 4	492
	21st to end	Day	22% 19% 30% 20% 8% 1	660
May	1st to 10th	Day	17% 11% 39% 25% 8% 1	703
	11th to 20th	Day	17% 12% 27% 28% 13% 3	676
	21st to end	Day	16% 9% 30% 23% 15% 7%	734
June	1st to 10th	Day	6% 4 24% 35% 25% 5%	680
	11th to 20th	Day	9% 2 25% 38% 22% 5%	680
	21st to end	Day	4 2 22% 43% 23% 5%	680
July	1st to 10th	Day	8% 2 15% 32% 31% 12%	671
	11th to 20th	Day	4 2 12% 41% 33% 8%	668
	21st to end	Day	7% 1 9% 34% 36% 13%	739
August	1st to 10th	Day	6% 1 13% 41% 33% 6%	676
	11th to 20th	Day	8% 2 14% 36% 32% 7%	665
	21st to end	Day	7% 2 10% 33% 38% 11%	611
September	1st to 10th	Day	11% 1 12% 29% 34% 13%	361
	11th to 20th	Day	5% 3 15% 38% 31% 9%	300
	21st to end	Day	13% 4 20% 34% 22% 7%	300
October	1st to 10th	Day	7% 5% 30% 29% 22% 6%	300
	11th to 20th	Day	8% 13% 37% 30% 11% 1	300
	21st to end	Day	24% 11% 30% 25% 9% 2	330
November	1st to 10th	Day	16% 10% 38% 25% 10% 2	300
	11th to 20th	Day	15% 12% 39% 22% 10% 2	300
	21st to end	Day	20% 16% 37% 20% 7%	300
December	1st to 10th	Day	15% 17% 38% 19% 10% 1	300
	11th to 20th	Day	18% 15% 39% 20% 7%	300
	21st to end	Day	18% 23% 34% 20% 4	330
January	1st to 10th	Night	14% 13% 39% 28% 6%	1000
	11th to 20th	Night	15% 14% 38% 27% 5%	1000
	21st to end	Night	14% 13% 38% 30% 4	1100
February	1st to 10th	Night	20% 14% 38% 25% 4	1000
	11th to 20th	Night	18% 16% 36% 26% 3	866
	21st to end	Night	17% 13% 39% 27% 4	615
March	1st to 10th	Night	16% 13% 37% 31% 4	600
	11th to 20th	Night	18% 13% 39% 26% 4	600
	21st to end	Night	19% 14% 40% 22% 5%	660
April	1st to 10th	Night	16% 14% 41% 25% 4	600
	11th to 20th	Night	17% 12% 39% 26% 7%	593
	21st to end	Night	18% 11% 39% 25% 6% 1	600
May	1st to 10th	Night	15% 9% 40% 30% 6%	600
	11th to 20th	Night	16% 7% 28% 35% 13% 1	563
	21st to end	Night	10% 5% 30% 36% 17% 2	617
June	1st to 10th	Night	6% 3 22% 44% 24% 1	570
	11th to 20th	Night	4 3 27% 45% 20% 1	570
	21st to end	Night	4 3 22% 50% 20% 1	570
July	1st to 10th	Night	5% 1 15% 46% 30% 2	555
	11th to 20th	Night	3 16% 47% 31% 3	552
	21st to end	Night	5% 1 11% 45% 36% 2	624
August	1st to 10th	Night	3 1 14% 49% 30% 2	567
	11th to 20th	Night	7% 1 14% 43% 34% 2	564
	21st to end	Night	4 13% 37% 41% 4	627
September	1st to 10th	Night	10% 1 12% 45% 31% 1	570
	11th to 20th	Night	12% 2 18% 41% 24% 4	570
	21st to end	Night	10% 3 20% 39% 24% 4	570
October	1st to 10th	Night	8% 3 29% 36% 21% 3	680
	11th to 20th	Night	13% 8% 36% 32% 10% 1	760
	21st to end	Night	15% 13% 31% 30% 11% 1	836
November	1st to 10th	Night	13% 9% 37% 29% 11% 1	780
	11th to 20th	Night	13% 12% 35% 31% 9% 1	983
	21st to end	Night	17% 12% 33% 29% 9%	1000
December	1st to 10th	Night	15% 14% 34% 31% 6% 1	1000
	11th to 20th	Night	19% 12% 35% 28% 7%	1000
	21st to end	Night	19% 13% 35% 28% 5%	1100

Page generated at 2025-05-08 08:33:57. Version ac07

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