Family Astronomers Of Kentucky
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Family Astronomers Of Kentucky clear sky chart from 2005-11-06 to 2025-09-19.

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 7% 5% 5% 5% 4 6% 7% 36%	126349
	Night	15% 9% 3 7% 5% 4 4 3 5% 7% 37%	122675
Transparency	Day	46% 4 10% 24% 15% 2	130023
	Night	46% 3 10% 23% 16% 2	127069
Seeing	Day	20% 13% 25% 22% 14% 7%	16125
	Night	19% 9% 24% 29% 16% 2	25920

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	16% 17% 6% 10% 5% 3 4 3 5% 5% 25%	4056
	11th to 20th	Day	15% 14% 6% 14% 5% 4 3 2 3 3 31%	4060
	21st to end	Day	22% 12% 6% 7% 6% 5% 4 3 4 5% 27%	4466
February	1st to 10th	Day	19% 12% 4 9% 5% 4 4 3 4 6% 30%	1900
	11th to 20th	Day	19% 12% 4 8% 5% 5% 4 3 4 5% 31%	1948
	21st to end	Day	19% 11% 4 8% 5% 4 4 4 5% 6% 32%	1650
March	1st to 10th	Day	18% 13% 3 8% 4 4 4 3 4 5% 34%	4572
	11th to 20th	Day	13% 7% 3 7% 4 5% 4 4 6% 7% 42%	4980
	21st to end	Day	16% 8% 3 7% 5% 4 4 3 5% 7% 36%	5465
April	1st to 10th	Day	16% 9% 3 8% 4 4 3 4 6% 7% 36%	2310
	11th to 20th	Day	17% 7% 3 7% 4 4 4 3 5% 7% 38%	2437
	21st to end	Day	17% 8% 3 7% 5% 5% 4 4 5% 7% 35%	2600
May	1st to 10th	Day	18% 9% 3 8% 5% 5% 6% 5% 6% 8% 26%	5862
	11th to 20th	Day	19% 8% 3 8% 5% 4 4 4 6% 7% 32%	5861
	21st to end	Day	14% 7% 3 7% 4 5% 6% 5% 7% 10% 32%	6433
June	1st to 10th	Day	11% 4 2 6% 5% 6% 6% 4 6% 8% 41%	2600
	11th to 20th	Day	9% 5% 2 6% 5% 6% 6% 5% 6% 9% 40%	2600
	21st to end	Day	8% 5% 2 6% 6% 6% 5% 5% 8% 8% 41%	2745
July	1st to 10th	Day	10% 6% 3 6% 4 4 5% 4 6% 10% 42%	6066
	11th to 20th	Day	9% 6% 2 7% 6% 6% 6% 6% 8% 10% 33%	5900
	21st to end	Day	11% 9% 3 9% 7% 6% 7% 5% 6% 9% 28%	6424
August	1st to 10th	Day	8% 5% 2 6% 4 5% 5% 4 7% 11% 42%	4234
	11th to 20th	Day	8% 6% 2 7% 5% 5% 5% 5% 8% 11% 38%	4174
	21st to end	Day	5% 4 1 5% 4 4 4 4 5% 8% 54%	4359
September	1st to 10th	Day	15% 5% 2 4 4 4 4 3 5% 6% 46%	2245
	11th to 20th	Day	10% 6% 2 5% 3 5% 4 4 5% 7% 50%	2178
	21st to end	Day	16% 6% 2 5% 3 4 3 3 5% 8% 45%	2090
October	1st to 10th	Day	12% 4 2 4 4 3 4 3 5% 7% 52%	2090
	11th to 20th	Day	13% 6% 3 5% 4 3 5% 3 4 6% 48%	1916
	21st to end	Day	19% 8% 3 6% 4 4 3 2 4 6% 42%	1997
November	1st to 10th	Day	12% 6% 1 5% 4 3 4 2 3 6% 53%	1762
	11th to 20th	Day	15% 11% 4 6% 4 3 3 3 5% 6% 41%	1800
	21st to end	Day	18% 11% 3 7% 3 3 3 3 4 6% 38%	1800
December	1st to 10th	Day	19% 11% 3 8% 4 4 3 3 4 4 39%	2930
	11th to 20th	Day	21% 13% 4 8% 6% 5% 5% 3 4 4 28%	3373
	21st to end	Day	20% 17% 5% 10% 5% 4 4 4 4 5% 21%	4466
January	1st to 10th	Night	15% 15% 6% 15% 6% 5% 4 3 5% 5% 20%	5889
	11th to 20th	Night	18% 14% 6% 12% 6% 3 3 2 4 4 27%	5900
	21st to end	Night	20% 11% 4 7% 4 4 4 3 4 4 34%	6490
February	1st to 10th	Night	23% 12% 4 8% 5% 4 3 3 5% 5% 28%	2495
	11th to 20th	Night	20% 12% 4 9% 5% 4 4 3 5% 4 30%	2338
	21st to end	Night	23% 13% 3 7% 4 4 4 3 4 5% 31%	1980
March	1st to 10th	Night	18% 13% 2 6% 4 4 4 3 4 6% 37%	5267
	11th to 20th	Night	13% 7% 2 5% 4 4 4 3 6% 6% 46%	4980
	21st to end	Night	15% 8% 4 8% 5% 5% 5% 4 6% 7% 33%	5467
April	1st to 10th	Night	14% 7% 3 6% 5% 4 5% 4 6% 8% 37%	2105
	11th to 20th	Night	14% 7% 2 6% 6% 4 3 4 5% 7% 43%	1909
	21st to end	Night	15% 8% 3 6% 4 4 5% 4 6% 8% 37%	1800
May	1st to 10th	Night	19% 10% 3 9% 5% 4 5% 3 5% 7% 28%	4033
	11th to 20th	Night	16% 8% 3 7% 5% 4 6% 5% 7% 9% 31%	4032
	21st to end	Night	12% 7% 3 7% 5% 5% 6% 4 7% 9% 37%	4421
June	1st to 10th	Night	7% 5% 2 5% 4 4 5% 4 8% 9% 47%	1800
	11th to 20th	Night	6% 4 2 6% 5% 4 5% 5% 7% 11% 45%	1800
	21st to end	Night	8% 4 2 4 4 4 5% 5% 8% 11% 46%	1637
July	1st to 10th	Night	7% 6% 2 6% 5% 6% 5% 4 5% 9% 46%	3872
	11th to 20th	Night	7% 6% 3 8% 5% 6% 5% 4 7% 11% 38%	4057
	21st to end	Night	10% 8% 3 8% 5% 6% 5% 4 6% 8% 36%	4427
August	1st to 10th	Night	7% 6% 2 7% 4 5% 4 3 7% 10% 46%	2915
	11th to 20th	Night	7% 7% 2 7% 4 5% 4 5% 7% 9% 43%	2875
	21st to end	Night	4 4 1 3 3 3 4 3 5% 9% 60%	3535
September	1st to 10th	Night	11% 5% 2 5% 3 4 3 3 5% 7% 51%	2134
	11th to 20th	Night	10% 6% 2 5% 3 3 3 3 5% 7% 54%	2179
	21st to end	Night	13% 6% 3 6% 4 4 4 3 4 5% 49%	2090
October	1st to 10th	Night	10% 4 2 5% 3 3 3 3 5% 7% 55%	2090
	11th to 20th	Night	14% 5% 2 5% 4 3 5% 3 5% 7% 47%	2262
	21st to end	Night	16% 8% 3 5% 4 4 3 3 4 5% 44%	2598
November	1st to 10th	Night	14% 6% 2 5% 4 3 4 3 4 6% 49%	2536
	11th to 20th	Night	16% 9% 3 6% 4 4 4 3 4 6% 41%	2600
	21st to end	Night	19% 12% 3 6% 4 3 3 3 5% 5% 37%	2600
December	1st to 10th	Night	20% 11% 3 7% 4 3 3 3 4 4 38%	4250
	11th to 20th	Night	20% 11% 5% 9% 4 4 3 3 4 5% 32%	4822
	21st to end	Night	19% 18% 6% 10% 6% 5% 4 3 4 5% 19%	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	62% 2 8% 20% 8% 1	4057
	11th to 20th	Day	60% 2 5% 18% 13% 2	4060
	21st to end	Day	61% 1 7% 22% 7% 2	4466
February	1st to 10th	Day	58% 3 8% 19% 11% 2	1900
	11th to 20th	Day	57% 3 7% 20% 11% 2	1958
	21st to end	Day	54% 2 8% 22% 12% 2	1650
March	1st to 10th	Day	54% 2 5% 19% 14% 6%	4572
	11th to 20th	Day	42% 2 9% 28% 17% 2	4980
	21st to end	Day	48% 2 10% 25% 13% 1	5465
April	1st to 10th	Day	47% 3 10% 25% 13% 3	2310
	11th to 20th	Day	46% 3 8% 24% 15% 4	2437
	21st to end	Day	48% 4 11% 23% 12% 2	2600
May	1st to 10th	Day	54% 5% 12% 19% 10% 1	5897
	11th to 20th	Day	53% 3 11% 23% 10% 1	5865
	21st to end	Day	45% 4 14% 22% 13% 1	6447
June	1st to 10th	Day	39% 5% 11% 25% 18% 1	2600
	11th to 20th	Day	39% 5% 13% 24% 17% 2	2600
	21st to end	Day	38% 5% 13% 24% 16% 3	2745
July	1st to 10th	Day	38% 5% 12% 24% 19% 1	6001
	11th to 20th	Day	42% 8% 14% 25% 11% 1	5831
	21st to end	Day	51% 6% 12% 18% 11% 1	6240
August	1st to 10th	Day	35% 5% 13% 35% 11% 1	4221
	11th to 20th	Day	37% 5% 12% 31% 14% 1	4213
	21st to end	Day	27% 4 13% 32% 20% 3	4358
September	1st to 10th	Day	39% 4 11% 22% 20% 6%	2245
	11th to 20th	Day	34% 4 9% 26% 24% 3	2178
	21st to end	Day	40% 3 8% 27% 21% 3	2090
October	1st to 10th	Day	22% 3 7% 28% 37% 2	3480
	11th to 20th	Day	27% 2 9% 30% 30% 2	3156
	21st to end	Day	33% 2 9% 29% 23% 4	3273
November	1st to 10th	Day	35% 3 7% 29% 22% 4	1762
	11th to 20th	Day	46% 2 7% 23% 18% 4	1800
	21st to end	Day	48% 2 9% 22% 17% 2	1800
December	1st to 10th	Day	51% 2 8% 23% 17%	2930
	11th to 20th	Day	61% 3 7% 18% 11% 1	3370
	21st to end	Day	66% 3 10% 15% 6% 1	4466
January	1st to 10th	Night	66% 2 7% 16% 9% 1	5889
	11th to 20th	Night	62% 2 6% 17% 10% 4	5900
	21st to end	Night	55% 1 7% 23% 12% 2	6490
February	1st to 10th	Night	58% 3 10% 20% 9% 1	2495
	11th to 20th	Night	58% 2 7% 21% 12% 1	2339
	21st to end	Night	57% 2 9% 17% 11% 3	1980
March	1st to 10th	Night	51% 2 4 26% 14% 3	5267
	11th to 20th	Night	39% 2 9% 29% 20% 1	4980
	21st to end	Night	51% 2 7% 24% 14% 1	5467
April	1st to 10th	Night	44% 4 10% 23% 16% 2	2105
	11th to 20th	Night	42% 2 10% 22% 19% 6%	1909
	21st to end	Night	45% 4 11% 23% 14% 3	1800
May	1st to 10th	Night	55% 4 10% 20% 8% 2	4060
	11th to 20th	Night	49% 5% 13% 23% 9% 1	4033
	21st to end	Night	43% 5% 15% 22% 13% 3	4429
June	1st to 10th	Night	32% 5% 15% 27% 17% 4	1800
	11th to 20th	Night	32% 5% 15% 24% 20% 3	1800
	21st to end	Night	30% 7% 16% 25% 18% 4	1637
July	1st to 10th	Night	36% 6% 13% 22% 21% 3	3829
	11th to 20th	Night	39% 7% 16% 24% 12% 1	4006
	21st to end	Night	44% 6% 13% 22% 14% 2	4297
August	1st to 10th	Night	33% 6% 14% 33% 13% 1	2904
	11th to 20th	Night	37% 6% 11% 29% 18% 1	2902
	21st to end	Night	21% 4 13% 34% 23% 4	3535
September	1st to 10th	Night	33% 4 13% 24% 19% 7%	2134
	11th to 20th	Night	32% 3 10% 25% 26% 3	2179
	21st to end	Night	39% 4 8% 22% 25% 3	2090
October	1st to 10th	Night	24% 3 7% 25% 38% 3	3480
	11th to 20th	Night	27% 2 7% 27% 34% 3	3761
	21st to end	Night	32% 2 7% 24% 28% 8%	4272
November	1st to 10th	Night	38% 3 8% 24% 24% 4	2536
	11th to 20th	Night	46% 2 7% 21% 20% 5%	2600
	21st to end	Night	49% 2 8% 24% 14% 2	2600
December	1st to 10th	Night	51% 2 10% 23% 13% 1	4250
	11th to 20th	Night	55% 2 11% 20% 11% 1	4824
	21st to end	Night	68% 2 8% 16% 6%	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	28% 24% 30% 12% 4 1	300
	11th to 20th	Day	36% 25% 30% 9% 1	300
	21st to end	Day	30% 28% 30% 10% 3	330
February	1st to 10th	Day	31% 22% 33% 12% 2	300
	11th to 20th	Day	36% 29% 26% 7% 2	300
	21st to end	Day	34% 21% 33% 10% 2	249
March	1st to 10th	Day	26% 29% 29% 13% 3	340
	11th to 20th	Day	25% 24% 31% 15% 5% 1	500
	21st to end	Day	32% 17% 31% 14% 6%	550
April	1st to 10th	Day	26% 19% 28% 18% 7% 1	500
	11th to 20th	Day	21% 21% 27% 18% 8% 4	492
	21st to end	Day	22% 18% 33% 17% 8% 2	500
May	1st to 10th	Day	22% 17% 31% 18% 7% 4	503
	11th to 20th	Day	20% 11% 28% 23% 12% 6%	527
	21st to end	Day	16% 9% 25% 24% 17% 9%	573
June	1st to 10th	Day	12% 6% 25% 29% 20% 8%	530
	11th to 20th	Day	12% 6% 21% 32% 20% 9%	530
	21st to end	Day	10% 6% 24% 30% 20% 10%	675
July	1st to 10th	Day	15% 3 18% 23% 23% 18%	600
	11th to 20th	Day	11% 6% 16% 30% 24% 14%	524
	21st to end	Day	13% 4 15% 30% 23% 14%	576
August	1st to 10th	Day	13% 4 18% 23% 27% 16%	526
	11th to 20th	Day	14% 4 18% 31% 21% 13%	519
	21st to end	Day	8% 4 14% 31% 27% 16%	583
September	1st to 10th	Day	13% 5% 15% 27% 25% 15%	530
	11th to 20th	Day	10% 3 14% 30% 28% 14%	522
	21st to end	Day	21% 9% 19% 24% 21% 6%	490
October	1st to 10th	Day	13% 7% 24% 29% 20% 7%	490
	11th to 20th	Day	17% 14% 31% 20% 14% 4	490
	21st to end	Day	22% 12% 35% 22% 9% 1	446
November	1st to 10th	Day	17% 16% 33% 24% 6% 3	300
	11th to 20th	Day	27% 18% 31% 18% 5% 1	300
	21st to end	Day	28% 13% 39% 16% 3 1	300
December	1st to 10th	Day	27% 24% 30% 14% 5%	300
	11th to 20th	Day	27% 17% 38% 14% 4	300
	21st to end	Day	31% 22% 33% 13% 1	330
January	1st to 10th	Night	25% 18% 32% 21% 5%	800
	11th to 20th	Night	31% 17% 31% 19% 3	800
	21st to end	Night	25% 15% 34% 24% 2	880
February	1st to 10th	Night	30% 13% 32% 22% 2	800
	11th to 20th	Night	29% 16% 34% 20% 1	783
	21st to end	Night	32% 13% 34% 19% 1	660
March	1st to 10th	Night	24% 16% 30% 24% 6%	800
	11th to 20th	Night	26% 12% 33% 22% 7% 1	800
	21st to end	Night	22% 13% 32% 26% 7%	880
April	1st to 10th	Night	20% 12% 32% 27% 8%	705
	11th to 20th	Night	18% 11% 29% 28% 12% 1	593
	21st to end	Night	19% 7% 36% 30% 9% 1	600
May	1st to 10th	Night	21% 8% 30% 29% 11% 2	600
	11th to 20th	Night	18% 6% 21% 35% 17% 2	591
	21st to end	Night	12% 5% 19% 32% 27% 5%	650
June	1st to 10th	Night	9% 2 17% 44% 24% 3	600
	11th to 20th	Night	9% 2 14% 43% 29% 3	600
	21st to end	Night	10% 3 18% 37% 29% 4	600
July	1st to 10th	Night	11% 2 12% 33% 33% 9%	585
	11th to 20th	Night	6% 3 12% 37% 38% 4	582
	21st to end	Night	12% 2 9% 34% 36% 6%	657
August	1st to 10th	Night	10% 2 8% 36% 37% 7%	597
	11th to 20th	Night	9% 3 8% 38% 35% 6%	594
	21st to end	Night	8% 2 10% 34% 40% 7%	660
September	1st to 10th	Night	13% 3 12% 32% 35% 5%	734
	11th to 20th	Night	11% 3 13% 32% 35% 6%	793
	21st to end	Night	15% 4 20% 32% 26% 3	760
October	1st to 10th	Night	12% 5% 19% 33% 26% 5%	760
	11th to 20th	Night	18% 6% 26% 32% 17% 2	760
	21st to end	Night	22% 10% 29% 26% 12% 1	836
November	1st to 10th	Night	18% 9% 25% 31% 16% 2	780
	11th to 20th	Night	21% 12% 30% 26% 10% 1	800
	21st to end	Night	24% 12% 27% 27% 10% 1	800
December	1st to 10th	Night	30% 13% 28% 25% 5%	800
	11th to 20th	Night	26% 12% 31% 25% 6% 1	800
	21st to end	Night	28% 15% 29% 24% 4	880

Page generated at 2025-09-16 01:49:16. Version ac07

Copyright © 2025 Attilla Danko.