Cushing Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cushing Observatory clear sky chart from 2005-11-06 to 2026-07-16.

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% 9% 3 8% 5% 4 4 4 5% 7% 38%	138752
	Night	12% 10% 4 9% 5% 4 4 4 5% 6% 37%	134202
Transparency	Day	45% 6% 13% 25% 11% 1	142291
	Night	47% 5% 12% 23% 12% 1	138741
Seeing	Day	17% 11% 31% 26% 13% 4	18410
	Night	16% 9% 32% 31% 10% 1	28279

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	9% 13% 6% 19% 9% 5% 4 3 4 5% 23%	4691
	11th to 20th	Day	6% 12% 7% 14% 8% 7% 7% 7% 7% 5% 20%	4710
	21st to end	Day	4 14% 6% 11% 4 4 6% 4 6% 7% 32%	5691
February	1st to 10th	Day	8% 14% 5% 10% 6% 5% 5% 5% 6% 6% 31%	1890
	11th to 20th	Day	7% 12% 4 10% 5% 6% 4 4 5% 6% 37%	1844
	21st to end	Day	9% 11% 5% 10% 6% 5% 4 4 5% 8% 34%	1636
March	1st to 10th	Day	12% 9% 3 6% 4 4 3 3 4 8% 44%	4853
	11th to 20th	Day	10% 10% 3 7% 5% 5% 4 3 5% 8% 39%	5090
	21st to end	Day	20% 11% 3 9% 5% 5% 4 3 5% 6% 28%	5712
April	1st to 10th	Day	17% 12% 3 7% 5% 5% 4 4 5% 6% 33%	2520
	11th to 20th	Day	20% 13% 3 7% 5% 4 4 2 4 6% 31%	2494
	21st to end	Day	21% 11% 3 7% 5% 4 4 3 4 5% 32%	2725
May	1st to 10th	Day	11% 6% 2 6% 4 4 4 3 5% 6% 49%	8090
	11th to 20th	Day	17% 7% 2 6% 4 4 3 3 4 6% 44%	8222
	21st to end	Day	15% 7% 2 7% 5% 4 5% 4 6% 7% 39%	9047
June	1st to 10th	Day	12% 6% 2 6% 4 4 5% 4 6% 8% 44%	2940
	11th to 20th	Day	14% 7% 3 6% 5% 5% 5% 4 6% 9% 36%	2940
	21st to end	Day	13% 5% 2 5% 5% 4 6% 5% 8% 10% 38%	2940
July	1st to 10th	Day	10% 4 1 5% 4 4 5% 4 7% 10% 46%	6500
	11th to 20th	Day	9% 4 2 4 3 3 3 3 5% 9% 55%	6431
	21st to end	Day	9% 5% 2 5% 4 4 4 4 6% 9% 48%	6924
August	1st to 10th	Day	13% 6% 2 6% 3 5% 5% 4 6% 9% 43%	4281
	11th to 20th	Day	13% 5% 2 6% 4 5% 5% 4 6% 8% 43%	4171
	21st to end	Day	11% 6% 3 7% 4 4 5% 4 6% 7% 44%	4449
September	1st to 10th	Day	10% 6% 2 7% 4 4 5% 4 6% 7% 46%	2400
	11th to 20th	Day	12% 6% 2 5% 4 5% 5% 3 6% 8% 45%	2400
	21st to end	Day	15% 6% 2 5% 4 3 5% 3 5% 7% 44%	2086
October	1st to 10th	Day	16% 7% 2 6% 3 4 4 4 6% 8% 41%	2000
	11th to 20th	Day	17% 13% 3 7% 4 4 4 3 5% 5% 36%	2000
	21st to end	Day	17% 12% 3 8% 5% 3 3 3 4 6% 35%	2130
November	1st to 10th	Day	11% 14% 4 9% 6% 5% 4 3 5% 6% 33%	1737
	11th to 20th	Day	12% 16% 7% 10% 6% 5% 5% 3 4 5% 28%	1680
	21st to end	Day	14% 13% 4 9% 5% 5% 5% 4 5% 6% 31%	1680
December	1st to 10th	Day	8% 14% 5% 16% 13% 6% 5% 3 4 5% 20%	2690
	11th to 20th	Day	12% 16% 7% 10% 6% 4 5% 4 4 6% 27%	3088
	21st to end	Day	18% 21% 7% 19% 6% 4 3 2 3 3 13%	4070
January	1st to 10th	Night	9% 12% 7% 14% 8% 5% 4 3 5% 5% 28%	8232
	11th to 20th	Night	6% 13% 6% 13% 8% 7% 9% 8% 7% 5% 20%	8280
	21st to end	Night	6% 15% 6% 10% 6% 5% 5% 4 5% 6% 33%	8522
February	1st to 10th	Night	7% 11% 6% 10% 7% 6% 5% 3 5% 6% 34%	2730
	11th to 20th	Night	6% 10% 4 10% 6% 6% 5% 4 5% 6% 38%	2663
	21st to end	Night	11% 12% 4 9% 5% 5% 6% 3 5% 5% 35%	2170
March	1st to 10th	Night	10% 8% 2 7% 4 4 4 3 4 6% 47%	5263
	11th to 20th	Night	10% 8% 3 9% 6% 4 5% 4 7% 8% 35%	5090
	21st to end	Night	22% 12% 4 9% 5% 4 3 3 4 5% 29%	5459
April	1st to 10th	Night	18% 11% 4 7% 5% 4 4 3 4 6% 35%	2100
	11th to 20th	Night	21% 11% 3 6% 3 3 3 3 5% 5% 37%	2075
	21st to end	Night	19% 11% 3 6% 4 4 5% 4 5% 6% 33%	1891
May	1st to 10th	Night	11% 7% 3 6% 4 4 4 3 5% 6% 48%	4791
	11th to 20th	Night	17% 6% 2 5% 2 3 3 3 4 6% 49%	4670
	21st to end	Night	14% 7% 2 7% 5% 5% 4 4 6% 7% 39%	5139
June	1st to 10th	Night	12% 6% 2 5% 4 3 5% 4 6% 8% 45%	1680
	11th to 20th	Night	11% 6% 2 5% 5% 5% 4 4 6% 7% 46%	1680
	21st to end	Night	9% 5% 1 5% 4 5% 4 5% 7% 8% 46%	1582
July	1st to 10th	Night	9% 4 2 4 4 4 4 4 7% 9% 51%	3698
	11th to 20th	Night	7% 3 1 4 4 3 4 4 6% 9% 55%	3657
	21st to end	Night	9% 5% 2 5% 4 4 4 4 6% 7% 51%	3947
August	1st to 10th	Night	13% 5% 2 6% 4 4 4 3 5% 6% 48%	2875
	11th to 20th	Night	14% 5% 2 6% 3 3 5% 4 5% 7% 46%	2888
	21st to end	Night	12% 7% 2 6% 4 4 4 3 5% 6% 45%	3453
September	1st to 10th	Night	10% 4 2 5% 4 4 4 4 5% 7% 52%	2000
	11th to 20th	Night	9% 4 1 6% 3 4 4 3 6% 7% 53%	2000
	21st to end	Night	14% 5% 1 5% 3 4 4 3 4 6% 50%	2289
October	1st to 10th	Night	14% 7% 2 5% 4 3 4 2 5% 6% 49%	2400
	11th to 20th	Night	17% 10% 2 6% 4 4 4 3 4 6% 40%	2400
	21st to end	Night	18% 11% 3 7% 4 4 5% 3 5% 5% 35%	2708
November	1st to 10th	Night	14% 11% 3 7% 4 4 4 4 6% 6% 38%	2781
	11th to 20th	Night	13% 13% 5% 11% 6% 4 3 3 4 5% 33%	2940
	21st to end	Night	13% 11% 4 10% 6% 4 3 3 5% 6% 34%	2940
December	1st to 10th	Night	6% 12% 5% 14% 9% 8% 5% 4 4 6% 26%	4720
	11th to 20th	Night	11% 17% 6% 14% 6% 4 6% 6% 5% 4 21%	5339
	21st to end	Night	21% 17% 7% 16% 5% 4 3 3 3 3 18%	7150

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	64% 4 8% 16% 8%	4692
	11th to 20th	Day	62% 5% 9% 15% 9%	4710
	21st to end	Day	50% 5% 13% 22% 9%	5691
February	1st to 10th	Day	51% 6% 13% 21% 9% 1	1890
	11th to 20th	Day	48% 5% 13% 25% 8% 1	1853
	21st to end	Day	50% 5% 13% 21% 10% 1	1636
March	1st to 10th	Day	40% 5% 17% 24% 12% 3	4853
	11th to 20th	Day	43% 4 15% 27% 10% 1	5090
	21st to end	Day	56% 5% 9% 20% 9% 1	5714
April	1st to 10th	Day	52% 5% 11% 19% 13% 1	2520
	11th to 20th	Day	55% 4 10% 17% 11% 2	2494
	21st to end	Day	55% 5% 10% 20% 10%	2725
May	1st to 10th	Day	35% 5% 11% 28% 19% 1	8129
	11th to 20th	Day	41% 5% 10% 23% 16% 4	8226
	21st to end	Day	42% 6% 9% 29% 12% 1	9061
June	1st to 10th	Day	36% 7% 15% 30% 11% 1	2940
	11th to 20th	Day	43% 7% 14% 23% 12% 1	2940
	21st to end	Day	37% 8% 17% 27% 9% 1	2940
July	1st to 10th	Day	32% 7% 18% 33% 9%	6431
	11th to 20th	Day	27% 5% 17% 37% 13% 1	6356
	21st to end	Day	31% 6% 16% 30% 16%	6728
August	1st to 10th	Day	37% 7% 15% 28% 12% 1	4266
	11th to 20th	Day	38% 7% 14% 33% 8%	4210
	21st to end	Day	39% 6% 17% 26% 12% 1	4448
September	1st to 10th	Day	36% 7% 13% 33% 10%	2400
	11th to 20th	Day	37% 8% 18% 30% 7%	2400
	21st to end	Day	39% 5% 13% 32% 10% 1	2086
October	1st to 10th	Day	31% 5% 11% 36% 18% 1	3260
	11th to 20th	Day	42% 4 10% 26% 16% 2	3240
	21st to end	Day	47% 4 16% 25% 8%	3420
November	1st to 10th	Day	51% 7% 12% 18% 12% 1	1737
	11th to 20th	Day	59% 5% 12% 16% 7% 1	1680
	21st to end	Day	53% 6% 15% 19% 5% 2	1680
December	1st to 10th	Day	67% 5% 10% 13% 4	2690
	11th to 20th	Day	58% 5% 10% 19% 7%	3085
	21st to end	Day	77% 5% 6% 7% 5%	4070
January	1st to 10th	Night	59% 4 13% 15% 9%	8233
	11th to 20th	Night	62% 5% 9% 14% 8%	8280
	21st to end	Night	51% 5% 11% 23% 9%	8522
February	1st to 10th	Night	49% 6% 13% 21% 10% 1	2730
	11th to 20th	Night	47% 6% 14% 24% 9% 1	2664
	21st to end	Night	50% 5% 13% 20% 10% 1	2170
March	1st to 10th	Night	39% 5% 14% 21% 17% 3	5263
	11th to 20th	Night	45% 5% 15% 22% 13%	5090
	21st to end	Night	58% 4 10% 15% 13%	5459
April	1st to 10th	Night	50% 5% 7% 20% 16% 1	2100
	11th to 20th	Night	50% 5% 9% 20% 14% 2	2075
	21st to end	Night	49% 7% 9% 19% 14% 1	1891
May	1st to 10th	Night	36% 5% 10% 28% 19% 1	4816
	11th to 20th	Night	37% 5% 9% 22% 20% 7%	4671
	21st to end	Night	41% 6% 11% 26% 14% 1	5149
June	1st to 10th	Night	36% 7% 14% 28% 13% 2	1680
	11th to 20th	Night	36% 6% 15% 23% 18% 2	1680
	21st to end	Night	33% 9% 15% 28% 13% 3	1582
July	1st to 10th	Night	28% 7% 19% 33% 11% 1	3660
	11th to 20th	Night	26% 6% 14% 38% 15% 1	3612
	21st to end	Night	33% 6% 14% 29% 16% 2	3832
August	1st to 10th	Night	35% 6% 13% 28% 16% 3	2866
	11th to 20th	Night	36% 6% 13% 32% 11% 1	2915
	21st to end	Night	39% 7% 15% 27% 11% 1	3453
September	1st to 10th	Night	30% 7% 14% 34% 14% 1	2000
	11th to 20th	Night	30% 7% 17% 33% 13%	2000
	21st to end	Night	36% 6% 12% 32% 13% 1	2289
October	1st to 10th	Night	25% 4 7% 36% 24% 4	3920
	11th to 20th	Night	38% 5% 12% 23% 21% 1	3899
	21st to end	Night	48% 4 12% 24% 11%	4368
November	1st to 10th	Night	46% 6% 13% 24% 11% 1	2781
	11th to 20th	Night	54% 5% 12% 18% 10% 1	2940
	21st to end	Night	51% 6% 15% 21% 6% 1	2940
December	1st to 10th	Night	59% 7% 15% 16% 3	4720
	11th to 20th	Night	63% 5% 9% 16% 6%	5341
	21st to end	Night	71% 4 8% 12% 4	7150

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	15% 10% 39% 23% 10% 3	330
	11th to 20th	Day	14% 13% 40% 26% 6%	330
	21st to end	Day	14% 12% 40% 22% 10% 1	363
February	1st to 10th	Day	15% 18% 42% 19% 6% 1	330
	11th to 20th	Day	14% 15% 42% 21% 7% 2	330
	21st to end	Day	15% 17% 42% 23% 3	273
March	1st to 10th	Day	16% 17% 41% 19% 5% 2	330
	11th to 20th	Day	21% 12% 38% 23% 4 2	330
	21st to end	Day	25% 15% 31% 20% 8% 2	415
April	1st to 10th	Day	24% 16% 33% 22% 5% 1	540
	11th to 20th	Day	26% 14% 27% 23% 9% 1	532
	21st to end	Day	27% 13% 31% 19% 9% 2	745
May	1st to 10th	Day	17% 15% 29% 25% 11% 2	753
	11th to 20th	Day	20% 13% 27% 26% 12% 3	775
	21st to end	Day	18% 10% 27% 27% 15% 4	844
June	1st to 10th	Day	13% 7% 28% 31% 17% 4	780
	11th to 20th	Day	16% 10% 33% 28% 10% 2	780
	21st to end	Day	16% 7% 30% 28% 14% 5%	780
July	1st to 10th	Day	9% 5% 19% 31% 25% 10%	771
	11th to 20th	Day	9% 7% 27% 28% 21% 9%	744
	21st to end	Day	7% 3 27% 35% 19% 9%	794
August	1st to 10th	Day	11% 5% 24% 31% 23% 6%	726
	11th to 20th	Day	14% 5% 21% 30% 23% 7%	715
	21st to end	Day	12% 7% 24% 32% 21% 5%	668
September	1st to 10th	Day	14% 7% 28% 30% 16% 5%	530
	11th to 20th	Day	13% 6% 28% 32% 18% 3	530
	21st to end	Day	18% 11% 27% 23% 15% 6%	336
October	1st to 10th	Day	17% 12% 32% 19% 14% 5%	330
	11th to 20th	Day	21% 20% 30% 23% 5% 1	330
	21st to end	Day	25% 17% 36% 15% 7% 1	363
November	1st to 10th	Day	20% 19% 32% 21% 6% 2	330
	11th to 20th	Day	22% 16% 37% 18% 7%	330
	21st to end	Day	23% 14% 37% 21% 5%	330
December	1st to 10th	Day	18% 12% 42% 19% 9%	330
	11th to 20th	Day	22% 16% 35% 23% 4	330
	21st to end	Day	30% 12% 36% 18% 3 1	363
January	1st to 10th	Night	14% 10% 36% 30% 9%	1050
	11th to 20th	Night	16% 9% 39% 28% 7% 1	1050
	21st to end	Night	17% 9% 38% 30% 6% 1	1155
February	1st to 10th	Night	12% 12% 41% 27% 8% 1	1050
	11th to 20th	Night	10% 12% 42% 27% 8% 1	1029
	21st to end	Night	17% 12% 35% 27% 8% 1	786
March	1st to 10th	Night	16% 13% 37% 26% 7% 1	740
	11th to 20th	Night	18% 10% 41% 26% 6%	630
	21st to end	Night	22% 12% 29% 26% 9% 2	693
April	1st to 10th	Night	22% 12% 34% 25% 6%	630
	11th to 20th	Night	25% 11% 29% 26% 7%	623
	21st to end	Night	23% 8% 30% 31% 7% 1	630
May	1st to 10th	Night	18% 11% 32% 31% 7% 1	630
	11th to 20th	Night	17% 7% 32% 32% 10% 2	621
	21st to end	Night	13% 8% 27% 38% 13% 1	683
June	1st to 10th	Night	15% 5% 28% 40% 11% 1	630
	11th to 20th	Night	11% 6% 33% 42% 8%	630
	21st to end	Night	12% 5% 23% 43% 16% 1	630
July	1st to 10th	Night	6% 3 22% 42% 25% 2	615
	11th to 20th	Night	7% 3 25% 43% 21% 1	597
	21st to end	Night	7% 2 21% 45% 21% 3	657
August	1st to 10th	Night	9% 3 15% 52% 20% 2	597
	11th to 20th	Night	14% 3 20% 37% 24% 3	594
	21st to end	Night	12% 3 23% 37% 22% 2	660
September	1st to 10th	Night	11% 5% 23% 42% 17% 3	600
	11th to 20th	Night	10% 5% 30% 38% 17% 2	600
	21st to end	Night	15% 8% 32% 30% 15% 1	699
October	1st to 10th	Night	19% 8% 29% 31% 12% 1	800
	11th to 20th	Night	20% 13% 32% 28% 6% 1	800
	21st to end	Night	24% 10% 30% 29% 7%	880
November	1st to 10th	Night	19% 11% 33% 30% 7% 1	935
	11th to 20th	Night	21% 12% 34% 27% 6% 1	1050
	21st to end	Night	19% 14% 37% 24% 6%	1050
December	1st to 10th	Night	16% 12% 32% 30% 8% 1	1050
	11th to 20th	Night	21% 10% 36% 24% 8% 1	1050
	21st to end	Night	26% 10% 34% 25% 6% 1	1155

Page generated at 2026-07-13 02:14:49. Version ac07

Copyright © 2026 Attilla Danko.