Morehead State University
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Morehead State University clear sky chart from 2005-11-06 to 2026-01-02.

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	14% 9% 3 8% 5% 4 5% 4 6% 7% 35%	127150
	Night	14% 10% 3 8% 4 4 4 3 5% 7% 36%	124242
Transparency	Day	46% 5% 10% 22% 14% 2	130837
	Night	46% 5% 10% 22% 16% 2	128623
Seeing	Day	22% 13% 26% 21% 13% 5%	16344
	Night	20% 10% 25% 27% 15% 2	26428

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	15% 19% 8% 13% 5% 4 4 3 4 5% 22%	4065
	11th to 20th	Day	13% 16% 8% 13% 5% 4 4 2 3 3 29%	4060
	21st to end	Day	20% 13% 5% 7% 5% 4 4 3 4 6% 28%	4466
February	1st to 10th	Day	20% 12% 5% 11% 4 4 3 3 3 6% 30%	1869
	11th to 20th	Day	20% 11% 5% 10% 4 4 4 3 4 5% 29%	1948
	21st to end	Day	20% 12% 4 8% 4 3 5% 2 4 6% 32%	1650
March	1st to 10th	Day	18% 15% 3 7% 4 4 4 3 5% 5% 33%	4658
	11th to 20th	Day	13% 8% 3 6% 4 4 4 4 6% 8% 41%	4980
	21st to end	Day	17% 8% 3 7% 4 5% 4 4 6% 7% 35%	5465
April	1st to 10th	Day	15% 10% 3 8% 5% 5% 4 3 5% 6% 36%	2257
	11th to 20th	Day	16% 8% 3 6% 5% 5% 4 3 5% 6% 39%	2467
	21st to end	Day	17% 8% 2 7% 5% 5% 4 4 5% 7% 35%	2600
May	1st to 10th	Day	17% 10% 4 8% 5% 5% 6% 4 7% 8% 25%	5862
	11th to 20th	Day	18% 9% 3 8% 5% 5% 5% 4 6% 7% 30%	5861
	21st to end	Day	14% 7% 2 7% 5% 6% 6% 4 8% 10% 30%	6433
June	1st to 10th	Day	11% 6% 2 6% 5% 6% 5% 5% 6% 8% 41%	2600
	11th to 20th	Day	9% 6% 2 7% 5% 6% 6% 4 6% 9% 40%	2600
	21st to end	Day	9% 6% 2 6% 6% 5% 6% 5% 6% 9% 40%	2600
July	1st to 10th	Day	10% 6% 2 7% 5% 4 5% 4 6% 10% 40%	5900
	11th to 20th	Day	11% 6% 3 8% 6% 6% 6% 5% 8% 11% 31%	5900
	21st to end	Day	14% 9% 3 8% 6% 6% 6% 5% 7% 9% 28%	6424
August	1st to 10th	Day	8% 5% 2 6% 5% 5% 5% 4 8% 10% 41%	4234
	11th to 20th	Day	9% 7% 2 6% 5% 5% 6% 5% 7% 10% 38%	4174
	21st to end	Day	5% 3 1 5% 4 4 4 3 6% 9% 55%	4444
September	1st to 10th	Day	13% 5% 3 6% 4 4 4 3 5% 7% 46%	2210
	11th to 20th	Day	10% 6% 2 6% 4 4 4 3 5% 9% 48%	2200
	21st to end	Day	18% 6% 3 6% 4 3 3 3 5% 6% 43%	2200
October	1st to 10th	Day	11% 4 2 5% 4 3 3 2 6% 7% 52%	2189
	11th to 20th	Day	13% 7% 2 5% 3 3 4 3 5% 6% 50%	2000
	21st to end	Day	20% 7% 3 6% 4 3 3 2 4 6% 42%	2154
November	1st to 10th	Day	12% 8% 2 5% 4 3 4 2 4 5% 50%	1852
	11th to 20th	Day	15% 10% 3 6% 5% 4 4 3 4 7% 40%	1890
	21st to end	Day	17% 13% 4 7% 4 4 4 2 4 5% 37%	1890
December	1st to 10th	Day	19% 13% 3 9% 4 3 3 3 4 4 36%	3020
	11th to 20th	Day	23% 13% 5% 9% 4 4 4 3 4 4 26%	3463
	21st to end	Day	18% 17% 5% 11% 5% 5% 4 3 5% 5% 21%	4565
January	1st to 10th	Night	15% 16% 6% 16% 6% 4 4 3 4 5% 20%	5903
	11th to 20th	Night	17% 16% 6% 12% 5% 3 3 2 4 4 28%	5900
	21st to end	Night	19% 10% 5% 8% 5% 4 3 3 5% 5% 34%	6490
February	1st to 10th	Night	20% 13% 5% 9% 4 4 4 4 4 5% 29%	2530
	11th to 20th	Night	21% 12% 4 9% 5% 4 3 3 3 5% 30%	2338
	21st to end	Night	21% 13% 4 9% 4 4 4 3 4 5% 29%	1980
March	1st to 10th	Night	18% 14% 3 6% 4 4 4 3 4 6% 36%	5194
	11th to 20th	Night	12% 7% 3 6% 3 4 3 4 5% 7% 46%	4980
	21st to end	Night	13% 10% 3 8% 6% 5% 5% 4 6% 7% 33%	5467
April	1st to 10th	Night	16% 8% 2 6% 4 4 4 4 6% 8% 39%	2159
	11th to 20th	Night	14% 8% 2 5% 4 4 3 4 5% 8% 43%	1882
	21st to end	Night	17% 7% 2 7% 5% 4 5% 4 5% 7% 38%	1800
May	1st to 10th	Night	20% 10% 4 8% 5% 4 4 4 6% 8% 27%	4033
	11th to 20th	Night	15% 8% 3 7% 4 5% 5% 5% 7% 9% 31%	4032
	21st to end	Night	13% 8% 3 7% 5% 5% 5% 4 7% 9% 35%	4421
June	1st to 10th	Night	9% 6% 2 5% 4 5% 5% 4 8% 9% 45%	1800
	11th to 20th	Night	6% 4 3 5% 5% 4 6% 5% 7% 10% 45%	1800
	21st to end	Night	8% 4 2 6% 4 5% 5% 5% 8% 11% 43%	1800
July	1st to 10th	Night	7% 6% 2 6% 4 5% 5% 4 6% 9% 45%	4058
	11th to 20th	Night	9% 6% 3 8% 5% 5% 5% 5% 7% 10% 38%	4057
	21st to end	Night	11% 8% 3 8% 6% 5% 5% 5% 7% 9% 34%	4427
August	1st to 10th	Night	8% 6% 2 7% 5% 5% 5% 4 8% 10% 41%	2915
	11th to 20th	Night	11% 6% 2 6% 5% 5% 5% 4 6% 8% 42%	2875
	21st to end	Night	4 4 1 4 3 3 4 4 6% 9% 58%	3449
September	1st to 10th	Night	10% 6% 2 5% 4 5% 4 3 5% 8% 48%	2168
	11th to 20th	Night	10% 6% 3 4 4 4 4 3 5% 7% 51%	2200
	21st to end	Night	12% 7% 2 6% 5% 4 4 4 4 7% 45%	2200
October	1st to 10th	Night	10% 4 2 5% 3 3 3 2 5% 7% 54%	2210
	11th to 20th	Night	14% 5% 2 6% 4 3 4 3 4 6% 49%	2400
	21st to end	Night	18% 7% 2 6% 4 4 3 3 4 6% 43%	2683
November	1st to 10th	Night	12% 8% 3 5% 3 4 4 3 4 6% 49%	2666
	11th to 20th	Night	16% 9% 3 6% 4 3 3 3 5% 6% 42%	2730
	21st to end	Night	18% 13% 3 5% 4 3 3 3 5% 5% 38%	2730
December	1st to 10th	Night	18% 13% 4 8% 4 3 3 2 4 4 35%	4380
	11th to 20th	Night	20% 13% 7% 9% 4 3 3 2 4 5% 30%	4952
	21st to end	Night	18% 18% 5% 10% 5% 5% 5% 3 5% 6% 20%	6633

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	65% 4 8% 16% 7%	4066
	11th to 20th	Day	62% 3 5% 17% 11% 2	4060
	21st to end	Day	58% 3 9% 22% 8% 2	4466
February	1st to 10th	Day	58% 3 8% 18% 11% 1	1869
	11th to 20th	Day	58% 3 8% 18% 11% 2	1958
	21st to end	Day	55% 4 8% 20% 11% 3	1650
March	1st to 10th	Day	54% 3 6% 17% 14% 6%	4658
	11th to 20th	Day	40% 4 9% 25% 20% 3	4980
	21st to end	Day	47% 5% 9% 25% 13% 1	5465
April	1st to 10th	Day	48% 4 10% 22% 12% 3	2257
	11th to 20th	Day	46% 5% 8% 21% 16% 4	2467
	21st to end	Day	47% 6% 11% 22% 12% 2	2600
May	1st to 10th	Day	53% 6% 11% 18% 10% 1	5897
	11th to 20th	Day	53% 6% 10% 22% 9% 1	5865
	21st to end	Day	45% 8% 13% 20% 12% 2	6447
June	1st to 10th	Day	39% 8% 11% 25% 17% 1	2600
	11th to 20th	Day	40% 9% 13% 20% 17% 2	2600
	21st to end	Day	39% 8% 13% 21% 16% 3	2600
July	1st to 10th	Day	39% 7% 13% 25% 16% 1	5835
	11th to 20th	Day	44% 8% 14% 25% 8% 1	5831
	21st to end	Day	50% 7% 12% 19% 11% 1	6240
August	1st to 10th	Day	36% 8% 15% 30% 11% 1	4221
	11th to 20th	Day	38% 7% 10% 30% 14% 1	4213
	21st to end	Day	25% 6% 14% 32% 21% 2	4443
September	1st to 10th	Day	37% 5% 12% 20% 19% 6%	2210
	11th to 20th	Day	35% 4 11% 25% 23% 2	2200
	21st to end	Day	41% 4 9% 23% 20% 2	2200
October	1st to 10th	Day	23% 4 8% 25% 38% 2	3566
	11th to 20th	Day	27% 3 9% 29% 29% 3	3240
	21st to end	Day	33% 2 10% 28% 22% 5%	3456
November	1st to 10th	Day	37% 4 8% 26% 22% 4	1852
	11th to 20th	Day	45% 3 8% 22% 18% 3	1890
	21st to end	Day	51% 3 9% 19% 17% 1	1890
December	1st to 10th	Day	53% 3 7% 21% 15%	3020
	11th to 20th	Day	62% 2 8% 16% 11% 1	3460
	21st to end	Day	64% 4 11% 16% 5% 1	4565
January	1st to 10th	Night	66% 4 8% 15% 7% 1	5903
	11th to 20th	Night	61% 3 5% 17% 10% 4	5900
	21st to end	Night	53% 3 8% 23% 12% 2	6490
February	1st to 10th	Night	57% 4 10% 17% 11% 1	2530
	11th to 20th	Night	59% 3 7% 18% 12% 1	2339
	21st to end	Night	59% 3 9% 15% 11% 3	1980
March	1st to 10th	Night	50% 4 5% 23% 15% 4	5194
	11th to 20th	Night	37% 4 8% 27% 21% 2	4980
	21st to end	Night	49% 4 8% 22% 15% 1	5467
April	1st to 10th	Night	42% 6% 11% 21% 17% 2	2159
	11th to 20th	Night	40% 5% 10% 21% 18% 6%	1882
	21st to end	Night	45% 6% 11% 22% 14% 2	1800
May	1st to 10th	Night	54% 7% 10% 18% 9% 2	4060
	11th to 20th	Night	48% 8% 13% 21% 9% 1	4033
	21st to end	Night	42% 8% 16% 19% 13% 2	4429
June	1st to 10th	Night	33% 7% 15% 24% 17% 4	1800
	11th to 20th	Night	32% 9% 14% 23% 19% 3	1800
	21st to end	Night	33% 10% 14% 23% 16% 4	1800
July	1st to 10th	Night	35% 8% 11% 24% 19% 2	4015
	11th to 20th	Night	40% 8% 16% 24% 11% 2	4006
	21st to end	Night	45% 7% 11% 23% 13% 1	4297
August	1st to 10th	Night	35% 8% 14% 29% 12% 1	2904
	11th to 20th	Night	39% 6% 11% 27% 17% 1	2902
	21st to end	Night	22% 6% 14% 32% 22% 4	3449
September	1st to 10th	Night	34% 7% 12% 20% 20% 8%	2168
	11th to 20th	Night	33% 5% 11% 22% 26% 4	2200
	21st to end	Night	39% 6% 8% 21% 23% 3	2200
October	1st to 10th	Night	25% 4 7% 25% 36% 3	3613
	11th to 20th	Night	26% 3 7% 26% 31% 7%	3899
	21st to end	Night	31% 3 8% 22% 28% 8%	4331
November	1st to 10th	Night	38% 3 8% 24% 22% 4	2666
	11th to 20th	Night	43% 4 8% 19% 21% 5%	2730
	21st to end	Night	49% 4 9% 23% 14% 2	2730
December	1st to 10th	Night	54% 4 9% 20% 13% 1	4380
	11th to 20th	Night	57% 3 10% 19% 10% 1	4954
	21st to end	Night	64% 4 10% 14% 7%	6633

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	32% 20% 33% 12% 2 1	303
	11th to 20th	Day	40% 22% 29% 9%	300
	21st to end	Day	32% 29% 28% 10% 2	330
February	1st to 10th	Day	33% 23% 31% 11% 3	300
	11th to 20th	Day	41% 26% 27% 4 2	300
	21st to end	Day	36% 19% 37% 6% 2	249
March	1st to 10th	Day	35% 20% 29% 12% 4	374
	11th to 20th	Day	29% 23% 30% 14% 4	500
	21st to end	Day	32% 20% 29% 14% 5%	550
April	1st to 10th	Day	29% 19% 27% 18% 7% 1	500
	11th to 20th	Day	22% 20% 32% 17% 6% 3	492
	21st to end	Day	25% 18% 32% 18% 6% 2	500
May	1st to 10th	Day	26% 18% 28% 17% 8% 3	503
	11th to 20th	Day	22% 13% 29% 20% 12% 4	527
	21st to end	Day	17% 9% 25% 25% 15% 8%	573
June	1st to 10th	Day	14% 8% 25% 32% 15% 7%	530
	11th to 20th	Day	12% 8% 24% 32% 16% 8%	530
	21st to end	Day	12% 7% 26% 27% 19% 10%	530
July	1st to 10th	Day	15% 6% 17% 24% 20% 18%	525
	11th to 20th	Day	11% 6% 22% 31% 19% 11%	524
	21st to end	Day	14% 4 20% 29% 20% 12%	576
August	1st to 10th	Day	14% 3 21% 27% 23% 13%	526
	11th to 20th	Day	14% 4 17% 32% 23% 10%	519
	21st to end	Day	9% 5% 16% 32% 26% 13%	583
September	1st to 10th	Day	15% 5% 17% 24% 28% 11%	530
	11th to 20th	Day	12% 4 16% 26% 29% 13%	530
	21st to end	Day	21% 8% 22% 24% 22% 4	530
October	1st to 10th	Day	15% 6% 22% 30% 21% 6%	530
	11th to 20th	Day	17% 12% 30% 23% 14% 4	530
	21st to end	Day	26% 13% 31% 22% 7% 1	537
November	1st to 10th	Day	18% 15% 37% 22% 7% 2	330
	11th to 20th	Day	32% 16% 29% 16% 6% 1	330
	21st to end	Day	32% 18% 34% 13% 3 1	330
December	1st to 10th	Day	31% 23% 30% 12% 4	330
	11th to 20th	Day	32% 19% 33% 12% 4	330
	21st to end	Day	34% 21% 33% 12% 1	363
January	1st to 10th	Night	27% 20% 30% 19% 4	805
	11th to 20th	Night	32% 18% 29% 18% 3	800
	21st to end	Night	25% 19% 34% 20% 2	880
February	1st to 10th	Night	29% 14% 34% 21% 2	800
	11th to 20th	Night	31% 20% 31% 17% 1	783
	21st to end	Night	32% 16% 34% 16% 1	660
March	1st to 10th	Night	28% 15% 30% 23% 5%	800
	11th to 20th	Night	26% 18% 30% 20% 6%	800
	21st to end	Night	21% 17% 31% 25% 6%	880
April	1st to 10th	Night	25% 13% 30% 25% 7%	759
	11th to 20th	Night	20% 12% 30% 26% 11% 1	593
	21st to end	Night	20% 9% 34% 29% 7% 1	600
May	1st to 10th	Night	20% 10% 29% 27% 12% 2	600
	11th to 20th	Night	18% 7% 23% 34% 17% 2	591
	21st to end	Night	12% 3 21% 32% 27% 4	650
June	1st to 10th	Night	10% 4 21% 41% 21% 3	600
	11th to 20th	Night	9% 3 16% 41% 27% 4	600
	21st to end	Night	10% 2 20% 36% 28% 4	600
July	1st to 10th	Night	14% 2 15% 28% 32% 9%	585
	11th to 20th	Night	7% 2 13% 38% 36% 5%	582
	21st to end	Night	12% 2 10% 34% 36% 6%	657
August	1st to 10th	Night	11% 2 10% 35% 36% 6%	597
	11th to 20th	Night	11% 2 10% 36% 34% 7%	594
	21st to end	Night	9% 1 13% 33% 36% 8%	660
September	1st to 10th	Night	12% 3 13% 33% 34% 5%	768
	11th to 20th	Night	12% 3 15% 29% 35% 6%	800
	21st to end	Night	15% 6% 21% 31% 26% 2	800
October	1st to 10th	Night	13% 5% 18% 33% 28% 4	800
	11th to 20th	Night	18% 8% 27% 30% 16% 2	800
	21st to end	Night	22% 13% 27% 25% 12% 1	880
November	1st to 10th	Night	17% 9% 28% 29% 15% 1	820
	11th to 20th	Night	22% 14% 30% 25% 10%	840
	21st to end	Night	26% 14% 24% 27% 8% 1	840
December	1st to 10th	Night	29% 16% 27% 24% 4	840
	11th to 20th	Night	26% 13% 32% 23% 5% 1	840
	21st to end	Night	30% 16% 28% 23% 2	924

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