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 2024-02-10.

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	13% 9% 4 7% 6% 3 5% 5% 5% 7% 36%	78219
	Night	13% 10% 4 8% 6% 3 5% 5% 5% 6% 37%	80725
Transparency	Day	47% 7% 13% 23% 9% 1	77919
	Night	48% 6% 12% 22% 10% 1	80545
Seeing	Day	17% 10% 30% 26% 14% 4	14950
	Night	16% 8% 32% 32% 11% 1	25034

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	13% 14% 6% 15% 8% 3 5% 5% 4 5% 22%	2527
	11th to 20th	Day	6% 9% 6% 13% 12% 8% 9% 8% 5% 5% 19%	2530
	21st to end	Day	8% 19% 8% 12% 6% 3 5% 5% 5% 6% 23%	3070
February	1st to 10th	Day	8% 12% 5% 9% 6% 4 6% 6% 6% 6% 33%	1701
	11th to 20th	Day	8% 13% 5% 9% 7% 4 5% 4 5% 6% 35%	1574
	21st to end	Day	11% 11% 5% 10% 7% 4 5% 4 5% 8% 30%	1399
March	1st to 10th	Day	12% 12% 5% 8% 7% 4 4 4 5% 8% 31%	1899
	11th to 20th	Day	14% 10% 4 6% 6% 4 4 4 4 8% 37%	1980
	21st to end	Day	18% 11% 5% 7% 5% 3 5% 5% 6% 6% 29%	2222
April	1st to 10th	Day	17% 11% 4 6% 6% 4 4 5% 4 6% 34%	2160
	11th to 20th	Day	21% 13% 4 7% 5% 3 4 3 4 6% 31%	2134
	21st to end	Day	21% 10% 4 6% 6% 4 4 4 5% 5% 31%	2335
May	1st to 10th	Day	17% 9% 3 7% 6% 4 5% 5% 5% 6% 33%	2481
	11th to 20th	Day	18% 6% 3 6% 5% 4 4 5% 5% 7% 36%	2479
	21st to end	Day	14% 7% 3 7% 7% 3 5% 5% 6% 8% 37%	2725
June	1st to 10th	Day	12% 5% 2 5% 4 3 5% 5% 6% 7% 45%	2520
	11th to 20th	Day	12% 7% 3 5% 5% 3 5% 5% 7% 9% 38%	2520
	21st to end	Day	11% 4 2 4 6% 3 6% 7% 7% 10% 40%	2520
July	1st to 10th	Day	7% 3 1 4 4 3 5% 5% 7% 10% 50%	2520
	11th to 20th	Day	9% 4 2 5% 5% 3 4 4 6% 9% 50%	2520
	21st to end	Day	7% 4 2 4 4 3 5% 6% 7% 10% 49%	2743
August	1st to 10th	Day	9% 5% 2 5% 5% 4 6% 6% 7% 9% 42%	2360
	11th to 20th	Day	13% 4 2 5% 5% 3 5% 4 6% 7% 44%	2301
	21st to end	Day	10% 5% 2 5% 4 2 3 4 6% 8% 51%	2453
September	1st to 10th	Day	11% 5% 3 6% 5% 3 5% 4 5% 7% 45%	2160
	11th to 20th	Day	12% 6% 2 4 4 4 5% 4 5% 8% 46%	2160
	21st to end	Day	17% 6% 3 5% 5% 2 5% 4 5% 8% 41%	1878
October	1st to 10th	Day	17% 7% 2 5% 4 3 4 5% 6% 8% 39%	1800
	11th to 20th	Day	18% 12% 3 6% 5% 4 4 4 5% 5% 34%	1800
	21st to end	Day	18% 11% 4 8% 6% 3 3 3 5% 5% 35%	1918
November	1st to 10th	Day	11% 14% 5% 8% 6% 4 4 4 5% 6% 34%	1569
	11th to 20th	Day	13% 14% 8% 10% 7% 4 4 4 4 5% 26%	1520
	21st to end	Day	14% 12% 4 7% 5% 3 5% 4 5% 6% 33%	1520
December	1st to 10th	Day	10% 14% 6% 12% 9% 4 5% 5% 5% 5% 24%	1520
	11th to 20th	Day	12% 14% 8% 9% 7% 3 6% 4 4 6% 26%	1918
	21st to end	Day	22% 18% 6% 14% 7% 3 4 3 3 3 18%	2783
January	1st to 10th	Night	12% 12% 8% 13% 7% 3 4 4 5% 4 27%	4428
	11th to 20th	Night	8% 10% 6% 12% 10% 6% 8% 8% 6% 6% 21%	4440
	21st to end	Night	10% 20% 9% 11% 6% 3 4 4 4 5% 23%	4596
February	1st to 10th	Night	6% 10% 6% 9% 8% 4 5% 4 5% 6% 36%	2464
	11th to 20th	Night	6% 10% 4 9% 6% 4 6% 5% 5% 6% 39%	2273
	21st to end	Night	14% 12% 4 7% 6% 4 6% 4 4 5% 33%	1857
March	1st to 10th	Night	12% 10% 4 7% 7% 4 5% 4 5% 5% 36%	2075
	11th to 20th	Night	13% 10% 4 6% 5% 2 4 4 4 5% 41%	1980
	21st to end	Night	18% 8% 4 7% 6% 3 4 4 5% 5% 37%	2134
April	1st to 10th	Night	17% 10% 4 7% 5% 3 5% 4 4 6% 35%	1800
	11th to 20th	Night	23% 10% 4 5% 4 2 3 4 4 5% 35%	1775
	21st to end	Night	19% 10% 3 6% 5% 3 5% 5% 5% 6% 34%	1621
May	1st to 10th	Night	19% 7% 3 6% 6% 4 4 4 6% 5% 37%	1477
	11th to 20th	Night	15% 6% 2 6% 4 3 4 4 6% 7% 43%	1416
	21st to end	Night	11% 6% 2 5% 6% 3 6% 5% 6% 9% 41%	1551
June	1st to 10th	Night	11% 5% 2 4 5% 3 4 5% 6% 8% 46%	1440
	11th to 20th	Night	10% 5% 2 5% 5% 3 5% 5% 5% 7% 48%	1440
	21st to end	Night	7% 4 1 4 5% 3 5% 6% 8% 8% 48%	1357
July	1st to 10th	Night	5% 4 1 3 4 2 4 6% 6% 10% 56%	1440
	11th to 20th	Night	7% 3 2 4 5% 3 4 5% 6% 10% 52%	1440
	21st to end	Night	5% 3 1 2 4 3 4 5% 6% 8% 60%	1575
August	1st to 10th	Night	7% 4 2 5% 5% 3 4 4 5% 8% 51%	1576
	11th to 20th	Night	13% 4 2 5% 3 2 4 5% 5% 8% 50%	1600
	21st to end	Night	10% 4 2 5% 5% 3 4 4 4 5% 54%	1903
September	1st to 10th	Night	10% 4 2 4 5% 3 4 5% 5% 8% 52%	1800
	11th to 20th	Night	10% 4 2 5% 3 3 4 4 5% 7% 54%	1800
	21st to end	Night	15% 5% 2 5% 4 3 4 4 4 7% 48%	2059
October	1st to 10th	Night	15% 7% 2 4 4 2 4 3 4 6% 47%	2160
	11th to 20th	Night	18% 10% 2 6% 4 3 4 4 4 6% 40%	2160
	21st to end	Night	18% 11% 4 6% 4 2 5% 4 5% 6% 36%	2436
November	1st to 10th	Night	15% 10% 3 6% 5% 3 4 5% 5% 6% 38%	2509
	11th to 20th	Night	14% 12% 6% 11% 7% 3 4 3 3 5% 32%	2660
	21st to end	Night	13% 10% 5% 8% 7% 3 3 4 5% 7% 36%	2660
December	1st to 10th	Night	9% 14% 6% 11% 8% 4 5% 4 4 7% 28%	2660
	11th to 20th	Night	12% 15% 5% 11% 8% 3 6% 6% 5% 5% 25%	3279
	21st to end	Night	22% 16% 6% 10% 6% 3 4 4 4 4 22%	4884

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	63% 6% 10% 16% 4	2528
	11th to 20th	Day	65% 7% 10% 14% 5%	2530
	21st to end	Day	61% 7% 12% 15% 5%	3070
February	1st to 10th	Day	49% 6% 13% 22% 9% 1	1701
	11th to 20th	Day	50% 6% 13% 23% 8% 1	1583
	21st to end	Day	53% 5% 10% 19% 11% 1	1399
March	1st to 10th	Day	53% 5% 14% 19% 7% 1	1899
	11th to 20th	Day	48% 5% 15% 23% 9% 1	1980
	21st to end	Day	55% 5% 11% 21% 8% 1	2222
April	1st to 10th	Day	51% 5% 11% 19% 13% 1	2160
	11th to 20th	Day	56% 4 10% 18% 11% 2	2134
	21st to end	Day	56% 5% 11% 19% 9%	2335
May	1st to 10th	Day	50% 6% 12% 21% 9% 1	2481
	11th to 20th	Day	46% 7% 13% 22% 11% 1	2483
	21st to end	Day	45% 7% 10% 25% 11% 1	2725
June	1st to 10th	Day	36% 7% 16% 29% 11% 1	2520
	11th to 20th	Day	41% 8% 14% 24% 13% 1	2520
	21st to end	Day	35% 9% 18% 28% 9% 1	2520
July	1st to 10th	Day	27% 9% 16% 31% 15% 1	2451
	11th to 20th	Day	30% 7% 16% 28% 16% 2	2445
	21st to end	Day	29% 9% 17% 28% 17% 1	2591
August	1st to 10th	Day	35% 9% 15% 29% 9% 2	2345
	11th to 20th	Day	38% 7% 15% 29% 11%	2301
	21st to end	Day	32% 6% 15% 30% 15% 2	2453
September	1st to 10th	Day	37% 7% 12% 33% 11%	2160
	11th to 20th	Day	36% 8% 17% 31% 7%	2160
	21st to end	Day	42% 6% 13% 31% 8%	1878
October	1st to 10th	Day	42% 7% 14% 27% 9% 1	1800
	11th to 20th	Day	52% 5% 12% 19% 11% 1	1800
	21st to end	Day	52% 5% 13% 21% 8%	1918
November	1st to 10th	Day	50% 7% 11% 19% 12% 1	1569
	11th to 20th	Day	61% 5% 12% 14% 7% 1	1520
	21st to end	Day	51% 7% 16% 19% 5% 2	1520
December	1st to 10th	Day	62% 7% 13% 14% 4	1520
	11th to 20th	Day	59% 7% 14% 15% 4 1	1915
	21st to end	Day	71% 5% 7% 9% 7%	2783
January	1st to 10th	Night	57% 6% 11% 18% 6% 1	4428
	11th to 20th	Night	61% 7% 13% 13% 6%	4440
	21st to end	Night	63% 6% 9% 17% 5% 1	4596
February	1st to 10th	Night	48% 6% 13% 22% 10% 1	2464
	11th to 20th	Night	47% 6% 14% 23% 9% 2	2274
	21st to end	Night	52% 6% 12% 19% 10% 1	1857
March	1st to 10th	Night	49% 7% 12% 22% 9% 1	2075
	11th to 20th	Night	45% 5% 12% 21% 15% 1	1980
	21st to end	Night	49% 5% 11% 23% 11% 1	2134
April	1st to 10th	Night	50% 6% 7% 20% 16% 2	1800
	11th to 20th	Night	52% 5% 8% 19% 13% 2	1775
	21st to end	Night	49% 7% 10% 19% 14% 2	1621
May	1st to 10th	Night	48% 6% 12% 18% 15% 1	1477
	11th to 20th	Night	40% 8% 12% 25% 14% 2	1417
	21st to end	Night	38% 8% 14% 23% 15% 2	1552
June	1st to 10th	Night	35% 7% 15% 29% 12% 2	1440
	11th to 20th	Night	35% 7% 15% 23% 19% 2	1440
	21st to end	Night	30% 10% 16% 29% 13% 3	1357
July	1st to 10th	Night	22% 9% 15% 34% 18% 2	1400
	11th to 20th	Night	28% 8% 13% 31% 17% 4	1392
	21st to end	Night	21% 8% 17% 32% 19% 4	1487
August	1st to 10th	Night	29% 7% 14% 31% 14% 5%	1567
	11th to 20th	Night	33% 7% 14% 30% 14% 2	1600
	21st to end	Night	32% 7% 12% 29% 17% 3	1903
September	1st to 10th	Night	30% 7% 14% 34% 14% 1	1800
	11th to 20th	Night	30% 7% 16% 33% 14%	1800
	21st to end	Night	38% 6% 13% 31% 11%	2059
October	1st to 10th	Night	38% 6% 11% 31% 12% 2	2160
	11th to 20th	Night	46% 6% 12% 22% 12% 1	2160
	21st to end	Night	50% 6% 13% 21% 10% 1	2436
November	1st to 10th	Night	45% 6% 13% 23% 12% 1	2509
	11th to 20th	Night	55% 5% 12% 16% 11% 1	2660
	21st to end	Night	48% 7% 15% 22% 6% 1	2660
December	1st to 10th	Night	57% 6% 14% 17% 5%	2660
	11th to 20th	Night	59% 7% 12% 17% 5% 1	3281
	21st to end	Night	66% 5% 10% 14% 5%	4884

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% 38% 23% 11% 4	270
	11th to 20th	Day	15% 12% 40% 26% 8%	270
	21st to end	Day	15% 9% 38% 24% 12% 2	297
February	1st to 10th	Day	16% 14% 42% 21% 6%	267
	11th to 20th	Day	16% 16% 40% 20% 6% 2	240
	21st to end	Day	18% 15% 41% 24% 2	198
March	1st to 10th	Day	15% 15% 40% 20% 7% 3	240
	11th to 20th	Day	20% 9% 37% 27% 5% 3	240
	21st to end	Day	24% 14% 28% 20% 11% 2	308
April	1st to 10th	Day	23% 15% 33% 23% 6% 1	420
	11th to 20th	Day	27% 11% 25% 26% 10% 1	412
	21st to end	Day	26% 12% 30% 19% 10% 2	595
May	1st to 10th	Day	19% 15% 30% 24% 10% 2	603
	11th to 20th	Day	20% 12% 27% 26% 12% 4	625
	21st to end	Day	18% 10% 26% 27% 15% 4	679
June	1st to 10th	Day	12% 5% 27% 33% 19% 5%	630
	11th to 20th	Day	13% 8% 33% 31% 12% 2	630
	21st to end	Day	13% 7% 29% 29% 16% 6%	630
July	1st to 10th	Day	9% 5% 20% 30% 25% 10%	621
	11th to 20th	Day	10% 6% 27% 28% 21% 9%	618
	21st to end	Day	7% 4 25% 36% 19% 9%	684
August	1st to 10th	Day	10% 3 24% 32% 25% 6%	626
	11th to 20th	Day	14% 6% 20% 30% 23% 8%	615
	21st to end	Day	12% 6% 24% 32% 21% 5%	572
September	1st to 10th	Day	14% 6% 28% 31% 16% 5%	450
	11th to 20th	Day	13% 6% 28% 31% 18% 4	450
	21st to end	Day	22% 12% 28% 22% 11% 5%	276
October	1st to 10th	Day	19% 11% 30% 19% 15% 6%	270
	11th to 20th	Day	19% 20% 28% 26% 6% 1	270
	21st to end	Day	23% 18% 36% 14% 7% 1	297
November	1st to 10th	Day	19% 17% 34% 21% 7% 2	270
	11th to 20th	Day	23% 14% 39% 18% 7%	270
	21st to end	Day	23% 13% 39% 20% 5%	270
December	1st to 10th	Day	18% 11% 41% 20% 10%	270
	11th to 20th	Day	22% 17% 34% 23% 4	270
	21st to end	Day	32% 10% 36% 20% 2	297
January	1st to 10th	Night	14% 10% 37% 31% 9% 1	950
	11th to 20th	Night	16% 8% 39% 28% 8% 1	950
	21st to end	Night	18% 9% 36% 30% 7% 1	1045
February	1st to 10th	Night	11% 11% 41% 28% 8% 1	948
	11th to 20th	Night	10% 11% 42% 27% 9% 1	879
	21st to end	Night	18% 11% 34% 26% 9% 1	673
March	1st to 10th	Night	17% 13% 35% 27% 8% 1	635
	11th to 20th	Night	17% 8% 40% 27% 7%	540
	21st to end	Night	22% 11% 29% 26% 10% 3	594
April	1st to 10th	Night	20% 12% 36% 25% 7%	540
	11th to 20th	Night	27% 10% 28% 27% 8% 1	533
	21st to end	Night	24% 8% 29% 31% 8% 1	540
May	1st to 10th	Night	19% 11% 31% 32% 6% 1	540
	11th to 20th	Night	17% 6% 32% 31% 12% 2	531
	21st to end	Night	13% 8% 26% 37% 14% 1	584
June	1st to 10th	Night	13% 5% 28% 41% 12% 1	540
	11th to 20th	Night	10% 6% 32% 43% 9%	540
	21st to end	Night	9% 5% 23% 43% 18% 2	540
July	1st to 10th	Night	5% 3 22% 42% 27% 2	525
	11th to 20th	Night	7% 3 26% 43% 20% 1	522
	21st to end	Night	6% 2 21% 47% 21% 3	591
August	1st to 10th	Night	8% 2 14% 54% 20% 2	537
	11th to 20th	Night	14% 3 19% 36% 25% 3	534
	21st to end	Night	12% 3 24% 37% 23% 2	594
September	1st to 10th	Night	10% 4 23% 43% 16% 3	540
	11th to 20th	Night	10% 5% 29% 36% 18% 2	540
	21st to end	Night	16% 8% 34% 28% 13% 1	629
October	1st to 10th	Night	20% 7% 28% 30% 13% 2	720
	11th to 20th	Night	21% 12% 31% 29% 6% 1	720
	21st to end	Night	24% 10% 29% 29% 8%	792
November	1st to 10th	Night	20% 11% 32% 30% 7% 1	843
	11th to 20th	Night	20% 11% 35% 27% 7% 1	950
	21st to end	Night	18% 13% 38% 24% 7%	950
December	1st to 10th	Night	16% 13% 31% 31% 8% 1	950
	11th to 20th	Night	21% 9% 37% 25% 8% 1	950
	21st to end	Night	25% 9% 34% 25% 6%	1045

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