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 2024-03-06.

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	16% 8% 3 6% 5% 3 5% 5% 5% 7% 37%	79077
	Night	15% 9% 3 6% 5% 3 4 4 5% 7% 38%	80421
Transparency	Day	48% 3 10% 23% 14% 2	78800
	Night	47% 3 10% 22% 15% 3	80217
Seeing	Day	20% 13% 25% 22% 14% 7%	13990
	Night	19% 9% 24% 29% 16% 2	23976

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	17% 16% 6% 7% 6% 3 5% 4 5% 6% 24%	2836
	11th to 20th	Day	17% 13% 6% 14% 7% 4 3 3 3 4 26%	2840
	21st to end	Day	28% 15% 8% 6% 4 2 3 3 4 4 22%	3124
February	1st to 10th	Day	19% 12% 4 8% 6% 3 4 4 4 6% 30%	1805
	11th to 20th	Day	18% 10% 5% 8% 6% 4 4 4 4 5% 32%	1848
	21st to end	Day	19% 11% 4 7% 5% 2 4 5% 5% 6% 31%	1570
March	1st to 10th	Day	20% 9% 3 5% 5% 2 4 5% 5% 6% 36%	1886
	11th to 20th	Day	20% 8% 4 7% 6% 3 4 5% 6% 4 32%	1980
	21st to end	Day	20% 9% 4 6% 7% 3 4 3 5% 6% 32%	2178
April	1st to 10th	Day	14% 8% 3 7% 6% 3 4 4 5% 7% 39%	2078
	11th to 20th	Day	18% 7% 3 6% 4 3 4 4 5% 7% 38%	2190
	21st to end	Day	18% 7% 3 6% 6% 3 4 5% 5% 7% 35%	2340
May	1st to 10th	Day	20% 6% 3 5% 5% 4 5% 5% 5% 7% 34%	2340
	11th to 20th	Day	19% 7% 3 7% 6% 3 5% 5% 5% 6% 34%	2301
	21st to end	Day	8% 6% 3 6% 5% 4 6% 7% 7% 10% 38%	2531
June	1st to 10th	Day	12% 4 2 5% 6% 4 5% 5% 6% 8% 43%	2340
	11th to 20th	Day	9% 5% 3 4 6% 4 6% 6% 6% 9% 42%	2340
	21st to end	Day	9% 5% 3 6% 6% 4 6% 5% 8% 8% 41%	2469
July	1st to 10th	Day	13% 6% 3 5% 5% 4 6% 5% 7% 10% 36%	2408
	11th to 20th	Day	10% 6% 2 5% 5% 5% 6% 6% 7% 10% 38%	2340
	21st to end	Day	11% 5% 3 6% 6% 4 6% 6% 6% 9% 39%	2547
August	1st to 10th	Day	11% 5% 2 5% 5% 4 5% 5% 7% 10% 40%	2327
	11th to 20th	Day	9% 6% 3 6% 7% 4 6% 5% 7% 10% 37%	2303
	21st to end	Day	8% 5% 2 5% 5% 4 5% 6% 6% 10% 43%	2408
September	1st to 10th	Day	16% 5% 2 4 5% 3 5% 4 6% 7% 45%	2021
	11th to 20th	Day	10% 5% 2 5% 4 4 4 4 6% 7% 49%	1980
	21st to end	Day	15% 5% 2 4 4 2 4 4 5% 8% 47%	1980
October	1st to 10th	Day	12% 4 2 4 5% 3 3 4 5% 8% 50%	1980
	11th to 20th	Day	14% 6% 3 4 4 2 5% 4 4 6% 47%	1816
	21st to end	Day	20% 8% 3 5% 4 3 3 3 4 6% 41%	1892
November	1st to 10th	Day	12% 5% 2 5% 4 2 3 3 3 6% 54%	1672
	11th to 20th	Day	15% 10% 4 6% 4 2 4 3 4 6% 42%	1710
	21st to end	Day	19% 9% 4 6% 4 2 3 4 4 6% 39%	1710
December	1st to 10th	Day	23% 12% 4 7% 6% 3 3 5% 4 5% 29%	1710
	11th to 20th	Day	16% 13% 4 7% 7% 3 6% 4 4 5% 32%	2153
	21st to end	Day	19% 18% 5% 8% 7% 4 4 4 5% 6% 21%	3124
January	1st to 10th	Night	16% 15% 6% 9% 7% 3 4 4 5% 5% 25%	4109
	11th to 20th	Night	19% 15% 6% 11% 7% 2 3 3 4 4 27%	4120
	21st to end	Night	25% 14% 5% 7% 5% 3 3 3 4 4 27%	4532
February	1st to 10th	Night	23% 11% 5% 7% 5% 3 4 4 4 6% 29%	2371
	11th to 20th	Night	20% 11% 4 8% 6% 3 4 4 5% 5% 32%	2218
	21st to end	Night	24% 13% 4 6% 5% 3 4 4 3 5% 30%	1884
March	1st to 10th	Night	17% 9% 3 6% 5% 3 4 4 4 6% 40%	2191
	11th to 20th	Night	19% 9% 4 4 6% 3 4 4 5% 7% 35%	1980
	21st to end	Night	16% 9% 4 7% 6% 3 4 4 6% 7% 34%	2178
April	1st to 10th	Night	13% 6% 3 5% 6% 3 5% 5% 6% 8% 40%	1895
	11th to 20th	Night	15% 6% 3 5% 6% 4 3 4 4 7% 43%	1717
	21st to end	Night	16% 7% 3 6% 5% 3 5% 5% 6% 7% 38%	1620
May	1st to 10th	Night	16% 6% 3 7% 6% 3 5% 5% 5% 7% 35%	1620
	11th to 20th	Night	14% 8% 3 5% 5% 3 6% 5% 5% 8% 37%	1592
	21st to end	Night	8% 5% 2 5% 6% 4 6% 6% 6% 11% 41%	1744
June	1st to 10th	Night	6% 5% 2 4 5% 3 5% 6% 7% 10% 47%	1620
	11th to 20th	Night	6% 4 2 5% 5% 3 5% 5% 7% 11% 47%	1620
	21st to end	Night	9% 3 2 4 4 3 6% 6% 7% 11% 46%	1474
July	1st to 10th	Night	9% 6% 2 5% 5% 5% 5% 5% 5% 10% 43%	1538
	11th to 20th	Night	5% 4 3 4 5% 4 4 6% 7% 10% 47%	1620
	21st to end	Night	9% 5% 2 4 4 4 6% 6% 6% 7% 47%	1771
August	1st to 10th	Night	8% 5% 1 4 5% 3 5% 4 7% 11% 47%	1611
	11th to 20th	Night	8% 6% 2 5% 4 4 4 7% 8% 9% 44%	1598
	21st to end	Night	7% 5% 2 4 4 3 4 4 5% 9% 53%	1945
September	1st to 10th	Night	12% 5% 2 4 4 3 4 4 5% 8% 50%	1920
	11th to 20th	Night	10% 5% 2 4 4 2 3 4 5% 7% 53%	1980
	21st to end	Night	11% 5% 3 5% 4 4 4 4 4 5% 51%	1980
October	1st to 10th	Night	10% 4 2 4 4 2 3 4 6% 7% 55%	1980
	11th to 20th	Night	15% 5% 2 5% 4 2 5% 5% 5% 7% 46%	2142
	21st to end	Night	18% 8% 3 4 5% 3 3 4 4 5% 42%	2461
November	1st to 10th	Night	13% 6% 2 5% 4 2 4 4 4 5% 51%	2406
	11th to 20th	Night	16% 9% 3 5% 5% 3 3 4 4 6% 42%	2470
	21st to end	Night	19% 10% 3 5% 4 2 4 3 4 6% 38%	2470
December	1st to 10th	Night	23% 10% 4 6% 4 3 4 4 5% 5% 31%	2470
	11th to 20th	Night	18% 9% 5% 9% 5% 3 4 3 4 5% 34%	3042
	21st to end	Night	19% 18% 5% 8% 7% 4 5% 4 5% 6% 19%	4532

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	61% 2 10% 18% 9% 1	2837
	11th to 20th	Day	65% 2 6% 20% 7% 1	2840
	21st to end	Day	67% 1 6% 21% 4 1	3124
February	1st to 10th	Day	58% 2 8% 19% 11% 2	1805
	11th to 20th	Day	56% 2 7% 21% 11% 3	1858
	21st to end	Day	55% 2 8% 21% 11% 3	1570
March	1st to 10th	Day	51% 2 8% 24% 14% 1	1886
	11th to 20th	Day	55% 4 8% 19% 12% 2	1980
	21st to end	Day	54% 3 9% 23% 10% 2	2178
April	1st to 10th	Day	45% 3 10% 26% 13% 3	2078
	11th to 20th	Day	46% 3 8% 22% 16% 4	2190
	21st to end	Day	49% 4 11% 23% 11% 2	2340
May	1st to 10th	Day	49% 4 12% 23% 9% 2	2340
	11th to 20th	Day	52% 2 13% 20% 12% 1	2305
	21st to end	Day	40% 6% 17% 23% 13% 1	2531
June	1st to 10th	Day	39% 5% 11% 26% 17% 1	2340
	11th to 20th	Day	39% 5% 14% 25% 17% 2	2340
	21st to end	Day	39% 5% 13% 24% 15% 3	2469
July	1st to 10th	Day	44% 5% 14% 19% 17% 2	2343
	11th to 20th	Day	40% 6% 13% 23% 15% 2	2271
	21st to end	Day	42% 5% 13% 25% 13% 3	2405
August	1st to 10th	Day	39% 4 14% 27% 14% 1	2314
	11th to 20th	Day	42% 5% 13% 26% 14% 1	2303
	21st to end	Day	36% 5% 15% 25% 16% 4	2408
September	1st to 10th	Day	40% 4 11% 21% 18% 6%	2021
	11th to 20th	Day	35% 4 10% 25% 23% 3	1980
	21st to end	Day	37% 3 7% 28% 22% 3	1980
October	1st to 10th	Day	34% 4 10% 26% 24% 3	1980
	11th to 20th	Day	39% 2 8% 27% 20% 4	1816
	21st to end	Day	46% 2 9% 24% 16% 2	1892
November	1st to 10th	Day	35% 3 7% 29% 22% 4	1672
	11th to 20th	Day	45% 2 7% 24% 18% 4	1710
	21st to end	Day	47% 2 9% 22% 18% 2	1710
December	1st to 10th	Day	59% 2 10% 19% 9% 1	1710
	11th to 20th	Day	56% 3 7% 19% 15% 1	2150
	21st to end	Day	66% 3 8% 15% 7% 1	3124
January	1st to 10th	Night	61% 2 7% 18% 11% 1	4109
	11th to 20th	Night	63% 2 6% 19% 8% 1	4120
	21st to end	Night	63% 1 7% 19% 8% 1	4532
February	1st to 10th	Night	58% 3 9% 21% 9% 1	2371
	11th to 20th	Night	56% 2 7% 22% 12% 1	2219
	21st to end	Night	59% 2 10% 16% 10% 3	1884
March	1st to 10th	Night	49% 3 6% 23% 17% 3	2191
	11th to 20th	Night	50% 2 10% 22% 13% 2	1980
	21st to end	Night	49% 4 11% 24% 11% 2	2178
April	1st to 10th	Night	41% 4 11% 25% 17% 2	1895
	11th to 20th	Night	42% 2 10% 20% 20% 7%	1717
	21st to end	Night	46% 4 11% 23% 13% 3	1620
May	1st to 10th	Night	48% 5% 11% 22% 10% 3	1620
	11th to 20th	Night	45% 6% 14% 21% 12% 2	1593
	21st to end	Night	36% 6% 17% 21% 17% 3	1745
June	1st to 10th	Night	31% 5% 16% 28% 16% 4	1620
	11th to 20th	Night	32% 5% 15% 24% 20% 4	1620
	21st to end	Night	31% 7% 16% 26% 16% 4	1474
July	1st to 10th	Night	39% 6% 14% 20% 17% 4	1493
	11th to 20th	Night	31% 5% 15% 25% 20% 4	1566
	21st to end	Night	34% 5% 15% 29% 15% 2	1672
August	1st to 10th	Night	32% 5% 15% 29% 18% 2	1600
	11th to 20th	Night	34% 7% 13% 28% 17% 1	1598
	21st to end	Night	29% 5% 14% 28% 19% 5%	1945
September	1st to 10th	Night	33% 4 14% 25% 17% 7%	1920
	11th to 20th	Night	33% 3 10% 25% 25% 3	1980
	21st to end	Night	37% 3 7% 23% 26% 3	1980
October	1st to 10th	Night	30% 3 11% 28% 23% 5%	1980
	11th to 20th	Night	39% 3 8% 25% 22% 3	2142
	21st to end	Night	45% 2 6% 25% 18% 3	2461
November	1st to 10th	Night	37% 2 8% 24% 24% 4	2406
	11th to 20th	Night	45% 2 7% 20% 21% 5%	2470
	21st to end	Night	49% 2 9% 25% 14% 2	2470
December	1st to 10th	Night	56% 3 10% 20% 11% 1	2470
	11th to 20th	Night	54% 2 8% 23% 12% 1	3044
	21st to end	Night	67% 2 7% 16% 7%	4532

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% 23% 31% 13% 4 1	270
	11th to 20th	Day	37% 24% 30% 9% 1	270
	21st to end	Day	31% 28% 29% 9% 3	297
February	1st to 10th	Day	31% 21% 33% 14% 2	270
	11th to 20th	Day	35% 27% 27% 8% 2	270
	21st to end	Day	35% 21% 33% 8% 2	225
March	1st to 10th	Day	25% 28% 32% 12% 3	291
	11th to 20th	Day	25% 24% 31% 15% 5% 1	420
	21st to end	Day	31% 16% 30% 15% 7%	462
April	1st to 10th	Day	22% 19% 29% 20% 9% 1	420
	11th to 20th	Day	23% 19% 25% 18% 10% 5%	412
	21st to end	Day	24% 18% 32% 15% 8% 2	420
May	1st to 10th	Day	23% 16% 30% 19% 8% 4	423
	11th to 20th	Day	19% 11% 29% 23% 13% 5%	447
	21st to end	Day	14% 7% 23% 26% 20% 10%	485
June	1st to 10th	Day	13% 6% 23% 29% 21% 9%	450
	11th to 20th	Day	12% 6% 21% 32% 20% 9%	450
	21st to end	Day	11% 6% 23% 30% 19% 10%	579
July	1st to 10th	Day	16% 3 17% 23% 21% 20%	513
	11th to 20th	Day	11% 6% 15% 28% 25% 14%	444
	21st to end	Day	14% 3 16% 30% 23% 15%	488
August	1st to 10th	Day	15% 4 16% 24% 27% 15%	446
	11th to 20th	Day	15% 4 16% 31% 21% 13%	439
	21st to end	Day	9% 5% 14% 31% 25% 17%	495
September	1st to 10th	Day	15% 4 15% 26% 26% 15%	450
	11th to 20th	Day	11% 4 13% 31% 27% 14%	450
	21st to end	Day	18% 8% 20% 25% 23% 6%	450
October	1st to 10th	Day	14% 7% 25% 29% 18% 7%	450
	11th to 20th	Day	18% 14% 32% 21% 13% 2	450
	21st to end	Day	23% 12% 35% 21% 8% 1	407
November	1st to 10th	Day	16% 17% 31% 25% 7% 3	270
	11th to 20th	Day	27% 18% 30% 19% 6% 1	270
	21st to end	Day	26% 12% 41% 16% 4 1	270
December	1st to 10th	Day	29% 22% 29% 14% 6%	270
	11th to 20th	Day	26% 18% 39% 13% 4	270
	21st to end	Day	31% 22% 34% 11% 1	297
January	1st to 10th	Night	25% 18% 32% 21% 5%	760
	11th to 20th	Night	31% 17% 30% 19% 3	760
	21st to end	Night	26% 15% 33% 24% 2	836
February	1st to 10th	Night	30% 13% 32% 23% 2	760
	11th to 20th	Night	28% 16% 34% 20% 1	743
	21st to end	Night	33% 14% 34% 18% 1	628
March	1st to 10th	Night	24% 16% 31% 24% 6%	743
	11th to 20th	Night	27% 11% 32% 22% 7% 1	720
	21st to end	Night	22% 13% 30% 28% 7%	792
April	1st to 10th	Night	18% 11% 31% 30% 8%	635
	11th to 20th	Night	19% 11% 28% 28% 14% 1	533
	21st to end	Night	20% 6% 35% 29% 9% 1	540
May	1st to 10th	Night	20% 7% 31% 29% 11% 2	540
	11th to 20th	Night	18% 6% 22% 35% 17% 2	531
	21st to end	Night	11% 4 18% 33% 29% 5%	584
June	1st to 10th	Night	9% 2 17% 43% 26% 4	540
	11th to 20th	Night	8% 2 14% 42% 30% 3	540
	21st to end	Night	10% 3 19% 37% 27% 4	540
July	1st to 10th	Night	11% 2 11% 32% 34% 10%	525
	11th to 20th	Night	6% 2 12% 37% 39% 4	522
	21st to end	Night	11% 2 9% 35% 36% 6%	591
August	1st to 10th	Night	10% 2 6% 37% 37% 7%	537
	11th to 20th	Night	10% 3 8% 36% 36% 7%	534
	21st to end	Night	9% 2 10% 34% 39% 7%	594
September	1st to 10th	Night	13% 3 11% 32% 36% 6%	660
	11th to 20th	Night	11% 3 13% 30% 35% 7%	720
	21st to end	Night	14% 3 20% 33% 27% 3	720
October	1st to 10th	Night	12% 5% 20% 32% 26% 4	720
	11th to 20th	Night	19% 5% 26% 33% 16% 1	720
	21st to end	Night	23% 10% 29% 25% 11% 2	792
November	1st to 10th	Night	17% 8% 25% 32% 16% 2	740
	11th to 20th	Night	21% 12% 30% 26% 10% 1	760
	21st to end	Night	23% 11% 27% 27% 10% 1	760
December	1st to 10th	Night	29% 13% 27% 25% 5%	760
	11th to 20th	Night	25% 11% 32% 25% 6% 1	760
	21st to end	Night	28% 15% 29% 23% 4	836

Page generated at 2024-03-03 06:28:57. Version ac07

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