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 2024-11-05.

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	15% 8% 3 7% 5% 4 4 4 6% 7% 37%	101287
	Night	15% 9% 3 7% 4 4 4 3 5% 7% 39%	97669
Transparency	Day	45% 3 10% 24% 15% 2	105005
	Night	44% 3 9% 24% 17% 3	102089
Seeing	Day	20% 13% 25% 22% 14% 7%	14965
	Night	19% 9% 24% 29% 16% 2	24802

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% 5% 8% 6% 4 4 3 6% 6% 24%	2836
	11th to 20th	Day	17% 14% 5% 15% 5% 5% 3 3 4 3 26%	2840
	21st to end	Day	28% 16% 8% 6% 4 3 3 2 4 4 22%	3124
February	1st to 10th	Day	19% 13% 4 9% 5% 4 4 3 4 6% 30%	1805
	11th to 20th	Day	18% 11% 4 8% 5% 5% 4 3 4 5% 32%	1848
	21st to end	Day	19% 12% 4 8% 5% 4 4 4 5% 6% 31%	1570
March	1st to 10th	Day	24% 13% 3 8% 4 3 4 3 4 5% 30%	3184
	11th to 20th	Day	14% 6% 2 6% 4 4 3 3 6% 7% 43%	3480
	21st to end	Day	16% 9% 3 7% 5% 4 4 3 6% 7% 37%	3815
April	1st to 10th	Day	15% 9% 3 8% 4 4 3 4 5% 7% 37%	2194
	11th to 20th	Day	17% 8% 3 6% 4 4 4 3 5% 7% 38%	2314
	21st to end	Day	17% 7% 3 7% 5% 5% 3 4 5% 7% 36%	2470
May	1st to 10th	Day	20% 9% 3 8% 4 5% 6% 4 5% 7% 29%	4082
	11th to 20th	Day	19% 8% 3 7% 5% 4 4 4 5% 7% 35%	4081
	21st to end	Day	10% 7% 3 7% 5% 5% 6% 5% 8% 10% 35%	4476
June	1st to 10th	Day	12% 4 2 6% 5% 6% 6% 4 6% 8% 41%	2470
	11th to 20th	Day	9% 5% 2 6% 5% 6% 6% 5% 6% 9% 41%	2470
	21st to end	Day	9% 5% 2 6% 6% 6% 5% 5% 8% 8% 41%	2607
July	1st to 10th	Day	12% 6% 2 6% 5% 5% 5% 4 7% 10% 39%	4230
	11th to 20th	Day	7% 5% 2 5% 5% 5% 5% 5% 8% 10% 43%	4120
	21st to end	Day	13% 10% 4 10% 6% 6% 6% 4 6% 8% 26%	4466
August	1st to 10th	Day	8% 5% 2 6% 4 5% 5% 4 7% 11% 43%	4104
	11th to 20th	Day	8% 6% 2 7% 5% 5% 5% 5% 8% 11% 39%	4044
	21st to end	Day	5% 4 2 5% 4 4 4 4 5% 8% 54%	4226
September	1st to 10th	Day	15% 5% 2 4 4 5% 4 3 6% 6% 46%	2133
	11th to 20th	Day	10% 6% 2 5% 3 5% 4 4 5% 7% 49%	2090
	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	11% 6% 2 5% 4 3 4 2 3 6% 54%	1708
	11th to 20th	Day	15% 11% 3 6% 4 3 3 3 5% 5% 41%	1710
	21st to end	Day	18% 10% 3 7% 3 3 3 3 4 6% 39%	1710
December	1st to 10th	Day	22% 13% 4 8% 5% 4 3 4 4 5% 29%	1710
	11th to 20th	Day	16% 13% 4 7% 6% 5% 5% 3 4 5% 32%	2153
	21st to end	Day	19% 18% 5% 9% 5% 4 4 4 5% 6% 21%	3124
January	1st to 10th	Night	16% 16% 5% 11% 6% 4 4 3 5% 5% 25%	4109
	11th to 20th	Night	19% 15% 6% 13% 5% 3 3 2 4 4 26%	4120
	21st to end	Night	25% 15% 5% 7% 4 3 3 2 4 4 27%	4532
February	1st to 10th	Night	23% 11% 4 8% 5% 4 3 4 5% 5% 29%	2371
	11th to 20th	Night	20% 11% 4 8% 5% 4 3 3 5% 5% 32%	2218
	21st to end	Night	23% 13% 3 7% 4 4 4 3 4 5% 29%	1884
March	1st to 10th	Night	21% 13% 3 6% 4 4 4 3 4 5% 33%	3655
	11th to 20th	Night	14% 7% 3 4 4 4 3 3 5% 6% 47%	3480
	21st to end	Night	13% 8% 3 7% 5% 4 5% 4 6% 7% 38%	3817
April	1st to 10th	Night	13% 7% 3 6% 5% 4 5% 4 6% 8% 38%	2000
	11th to 20th	Night	14% 7% 2 6% 5% 4 3 4 4 7% 43%	1813
	21st to end	Night	16% 8% 3 6% 4 4 5% 4 6% 7% 38%	1710
May	1st to 10th	Night	20% 10% 3 9% 5% 4 6% 3 5% 6% 28%	2813
	11th to 20th	Night	19% 8% 2 5% 4 3 5% 4 6% 8% 38%	2812
	21st to end	Night	9% 5% 2 6% 4 4 5% 4 6% 10% 44%	3079
June	1st to 10th	Night	7% 5% 2 4 5% 4 5% 4 8% 9% 46%	1710
	11th to 20th	Night	5% 4 2 6% 5% 4 5% 5% 7% 11% 46%	1710
	21st to end	Night	8% 4 2 4 4 4 5% 5% 8% 11% 45%	1555
July	1st to 10th	Night	7% 6% 2 6% 4 6% 5% 4 6% 10% 44%	2706
	11th to 20th	Night	6% 5% 2 6% 4 5% 4 4 7% 10% 46%	2840
	21st to end	Night	13% 9% 3 8% 4 5% 5% 4 6% 7% 35%	3087
August	1st to 10th	Night	8% 6% 2 6% 4 5% 4 3 7% 10% 46%	2825
	11th to 20th	Night	7% 7% 2 7% 4 5% 4 5% 7% 9% 43%	2785
	21st to end	Night	4 4 1 4 3 3 4 3 5% 9% 60%	3427
September	1st to 10th	Night	12% 5% 2 5% 3 4 3 3 5% 7% 50%	2027
	11th to 20th	Night	10% 6% 2 5% 4 3 3 3 5% 7% 53%	2090
	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	13% 6% 2 5% 4 3 4 4 4 5% 50%	2470
	11th to 20th	Night	16% 9% 3 6% 4 4 3 3 4 5% 42%	2470
	21st to end	Night	19% 11% 2 6% 4 3 3 3 5% 5% 38%	2470
December	1st to 10th	Night	23% 11% 4 7% 4 4 4 4 5% 5% 31%	2470
	11th to 20th	Night	18% 10% 5% 10% 5% 4 4 3 4 5% 33%	3042
	21st to end	Night	18% 18% 5% 10% 6% 5% 5% 3 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	58% 2 6% 20% 10% 4	3184
	11th to 20th	Day	42% 2 10% 28% 17% 1	3480
	21st to end	Day	48% 2 9% 27% 13% 1	3815
April	1st to 10th	Day	46% 3 10% 26% 13% 3	2194
	11th to 20th	Day	46% 3 8% 23% 16% 4	2314
	21st to end	Day	47% 4 11% 24% 11% 2	2470
May	1st to 10th	Day	54% 3 11% 21% 9% 1	4120
	11th to 20th	Day	51% 2 11% 23% 13% 1	4085
	21st to end	Day	42% 4 14% 21% 17% 2	4489
June	1st to 10th	Day	40% 5% 11% 26% 17% 1	2470
	11th to 20th	Day	38% 5% 13% 25% 17% 2	2470
	21st to end	Day	39% 5% 13% 24% 15% 3	2607
July	1st to 10th	Day	41% 4 13% 23% 17% 1	4165
	11th to 20th	Day	34% 5% 12% 33% 15% 1	4051
	21st to end	Day	56% 5% 10% 16% 11% 2	4324
August	1st to 10th	Day	35% 5% 13% 35% 11% 1	4091
	11th to 20th	Day	38% 5% 11% 31% 14% 1	4083
	21st to end	Day	28% 4 14% 32% 20% 3	4225
September	1st to 10th	Day	39% 4 10% 21% 20% 6%	2133
	11th to 20th	Day	35% 4 10% 25% 23% 3	2090
	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	34% 3 8% 29% 22% 4	1708
	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	55% 2 5% 25% 12% 2	3655
	11th to 20th	Night	40% 2 9% 29% 18% 2	3480
	21st to end	Night	45% 3 8% 28% 15% 1	3817
April	1st to 10th	Night	42% 4 11% 24% 17% 2	2000
	11th to 20th	Night	42% 2 9% 21% 19% 7%	1813
	21st to end	Night	45% 4 12% 23% 13% 3	1710
May	1st to 10th	Night	57% 4 9% 20% 8% 2	2840
	11th to 20th	Night	46% 4 13% 26% 11% 1	2813
	21st to end	Night	36% 4 12% 26% 18% 4	3087
June	1st to 10th	Night	32% 5% 15% 28% 16% 4	1710
	11th to 20th	Night	31% 5% 16% 25% 20% 4	1710
	21st to end	Night	31% 7% 16% 25% 17% 4	1555
July	1st to 10th	Night	36% 6% 14% 22% 18% 4	2661
	11th to 20th	Night	32% 6% 13% 29% 18% 2	2786
	21st to end	Night	48% 4 12% 20% 14% 2	2988
August	1st to 10th	Night	33% 6% 14% 33% 13% 1	2814
	11th to 20th	Night	37% 6% 10% 29% 18% 1	2812
	21st to end	Night	22% 4 14% 34% 22% 4	3427
September	1st to 10th	Night	33% 4 13% 24% 19% 7%	2027
	11th to 20th	Night	33% 3 10% 25% 26% 4	2090
	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	37% 2 8% 24% 24% 4	2470
	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	26% 28% 30% 13% 3	308
	11th to 20th	Day	24% 25% 31% 15% 4 1	460
	21st to end	Day	31% 16% 31% 15% 7%	506
April	1st to 10th	Day	25% 19% 28% 19% 8% 1	460
	11th to 20th	Day	22% 21% 26% 18% 9% 4	452
	21st to end	Day	23% 18% 33% 16% 8% 2	460
May	1st to 10th	Day	22% 18% 30% 19% 8% 4	463
	11th to 20th	Day	20% 10% 28% 24% 13% 6%	487
	21st to end	Day	14% 8% 24% 26% 19% 9%	529
June	1st to 10th	Day	13% 6% 24% 29% 20% 9%	490
	11th to 20th	Day	12% 6% 21% 32% 21% 9%	490
	21st to end	Day	11% 6% 25% 30% 19% 10%	627
July	1st to 10th	Day	16% 3 18% 23% 21% 19%	556
	11th to 20th	Day	10% 6% 17% 29% 24% 14%	484
	21st to end	Day	14% 4 16% 31% 22% 14%	532
August	1st to 10th	Day	14% 4 17% 23% 27% 15%	486
	11th to 20th	Day	15% 4 18% 31% 20% 12%	479
	21st to end	Day	9% 4 13% 31% 26% 17%	539
September	1st to 10th	Day	14% 4 15% 26% 26% 15%	490
	11th to 20th	Day	11% 4 15% 31% 26% 13%	490
	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	16% 17% 33% 25% 7% 3	282
	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% 30% 23% 6%	760
	11th to 20th	Night	26% 12% 33% 22% 7% 1	760
	21st to end	Night	22% 13% 31% 27% 7%	836
April	1st to 10th	Night	19% 12% 32% 29% 8%	670
	11th to 20th	Night	18% 12% 29% 28% 13% 1	563
	21st to end	Night	19% 7% 36% 29% 8% 1	570
May	1st to 10th	Night	21% 7% 30% 29% 11% 2	570
	11th to 20th	Night	18% 6% 21% 35% 18% 2	561
	21st to end	Night	11% 4 19% 33% 28% 5%	617
June	1st to 10th	Night	9% 2 18% 43% 25% 4	570
	11th to 20th	Night	8% 2 14% 43% 30% 3	570
	21st to end	Night	10% 3 18% 38% 27% 4	570
July	1st to 10th	Night	12% 2 12% 33% 32% 9%	555
	11th to 20th	Night	6% 3 12% 38% 38% 4	552
	21st to end	Night	12% 3 10% 36% 35% 5%	624
August	1st to 10th	Night	11% 2 7% 36% 37% 7%	567
	11th to 20th	Night	9% 3 8% 39% 34% 6%	564
	21st to end	Night	8% 2 10% 33% 41% 7%	627
September	1st to 10th	Night	13% 3 11% 32% 35% 5%	697
	11th to 20th	Night	12% 3 13% 32% 34% 6%	760
	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	17% 8% 25% 32% 16% 2	760
	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 2024-11-03 02:11:19. Version ac07

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