Lady Lake Astronomical Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lady Lake Astronomical Observatory clear sky chart from 2005-11-06 to 2024-11-10.

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	21% 15% 5% 10% 6% 4 4 3 4 5% 21%	101688
	Night	21% 14% 5% 11% 6% 5% 5% 3 4 5% 20%	97607
Transparency	Day	34% 49% 7% 8% 2	105176
	Night	33% 50% 7% 8% 2	102235
Seeing	Day	27% 20% 30% 17% 5% 1	18178
	Night	28% 19% 30% 18% 5%	24739

By Month

Percentage Cloud Cover NE (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% 15% 8% 17% 6% 4 3 3 4 6% 18%	2216
	11th to 20th	Day	21% 18% 6% 16% 5% 3 4 3 3 3 17%	2477
	21st to end	Day	14% 17% 7% 18% 6% 4 5% 2 3 5% 17%	2783
February	1st to 10th	Day	20% 15% 6% 12% 8% 5% 7% 3 4 5% 15%	1647
	11th to 20th	Day	20% 16% 5% 13% 8% 5% 5% 4 5% 5% 13%	1670
	21st to end	Day	14% 16% 6% 15% 8% 6% 6% 4 4 5% 15%	1570
March	1st to 10th	Day	23% 15% 6% 14% 6% 5% 3 2 4 3 18%	3140
	11th to 20th	Day	23% 18% 11% 12% 6% 4 4 3 3 4 13%	3480
	21st to end	Day	25% 17% 8% 12% 6% 5% 3 2 3 5% 13%	3817
April	1st to 10th	Day	21% 21% 5% 10% 6% 5% 4 3 4 4 17%	2298
	11th to 20th	Day	25% 18% 5% 10% 5% 3 3 3 4 4 21%	2441
	21st to end	Day	25% 19% 5% 9% 5% 4 3 3 4 5% 19%	2470
May	1st to 10th	Day	25% 25% 6% 7% 4 4 4 3 4 5% 14%	4105
	11th to 20th	Day	29% 17% 5% 8% 5% 4 4 3 4 5% 17%	4457
	21st to end	Day	22% 18% 5% 9% 5% 4 4 3 4 5% 20%	5173
June	1st to 10th	Day	29% 17% 5% 9% 5% 4 4 2 4 4 16%	2850
	11th to 20th	Day	24% 14% 4 8% 6% 4 4 4 5% 6% 22%	2850
	21st to end	Day	23% 14% 4 8% 6% 3 4 4 4 6% 24%	2850
July	1st to 10th	Day	25% 12% 4 9% 5% 4 4 4 5% 5% 22%	4750
	11th to 20th	Day	16% 12% 5% 11% 7% 5% 5% 4 6% 6% 25%	4731
	21st to end	Day	15% 10% 3 7% 5% 4 4 3 5% 7% 36%	4815
August	1st to 10th	Day	20% 13% 5% 10% 6% 5% 5% 4 5% 6% 22%	4202
	11th to 20th	Day	18% 9% 4 9% 5% 6% 5% 4 6% 7% 27%	4046
	21st to end	Day	17% 11% 4 8% 5% 4 5% 3 5% 7% 31%	4532
September	1st to 10th	Day	20% 10% 3 8% 4 4 5% 3 5% 8% 30%	2276
	11th to 20th	Day	22% 10% 3 8% 4 5% 5% 3 4 6% 30%	2090
	21st to end	Day	19% 10% 4 7% 5% 5% 4 3 6% 6% 32%	2090
October	1st to 10th	Day	19% 13% 3 8% 4 6% 4 3 5% 6% 27%	1991
	11th to 20th	Day	23% 14% 4 10% 6% 4 5% 3 4 4 22%	1854
	21st to end	Day	22% 15% 4 10% 7% 5% 5% 3 4 5% 19%	1881
November	1st to 10th	Day	21% 15% 4 11% 4 5% 5% 3 4 4 24%	1717
	11th to 20th	Day	22% 16% 5% 9% 6% 4 4 3 5% 7% 18%	1520
	21st to end	Day	24% 20% 5% 9% 6% 4 4 2 3 6% 17%	1459
December	1st to 10th	Day	23% 18% 6% 9% 7% 5% 4 3 4 5% 15%	1330
	11th to 20th	Day	26% 16% 6% 10% 6% 5% 4 3 4 4 16%	1668
	21st to end	Day	18% 17% 7% 15% 7% 5% 5% 4 4 4 14%	2442
January	1st to 10th	Night	16% 17% 9% 12% 8% 6% 5% 3 4 4 17%	4739
	11th to 20th	Night	18% 14% 6% 17% 7% 4 5% 4 4 5% 17%	4492
	21st to end	Night	14% 13% 7% 16% 7% 5% 6% 4 4 5% 18%	4884
February	1st to 10th	Night	20% 15% 7% 14% 7% 6% 4 3 4 5% 16%	2532
	11th to 20th	Night	22% 14% 5% 12% 7% 6% 6% 4 4 4 15%	2394
	21st to end	Night	13% 15% 6% 13% 7% 6% 6% 4 5% 6% 19%	1884
March	1st to 10th	Night	23% 12% 6% 12% 6% 4 4 3 4 5% 21%	3699
	11th to 20th	Night	16% 14% 9% 15% 8% 6% 5% 3 5% 4 14%	3479
	21st to end	Night	28% 16% 7% 10% 5% 4 4 3 4 4 14%	3815
April	1st to 10th	Night	25% 18% 6% 9% 5% 4 4 3 3 4 19%	1878
	11th to 20th	Night	23% 15% 4 10% 5% 4 4 3 4 4 23%	1688
	21st to end	Night	25% 21% 5% 8% 4 4 3 3 3 3 21%	1710
May	1st to 10th	Night	27% 18% 7% 9% 5% 4 4 3 3 5% 14%	2845
	11th to 20th	Night	30% 18% 6% 10% 4 3 4 2 4 4 15%	2441
	21st to end	Night	24% 16% 6% 11% 5% 5% 4 3 4 4 17%	2412
June	1st to 10th	Night	26% 18% 3 10% 6% 4 4 4 4 4 18%	1330
	11th to 20th	Night	22% 13% 5% 9% 5% 5% 4 4 5% 7% 21%	1330
	21st to end	Night	22% 16% 5% 9% 5% 4 3 4 5% 7% 21%	1330
July	1st to 10th	Night	30% 14% 3 9% 5% 4 4 3 4 6% 17%	2220
	11th to 20th	Night	14% 15% 6% 13% 7% 8% 7% 4 5% 5% 16%	2236
	21st to end	Night	14% 9% 3 10% 5% 5% 5% 3 6% 6% 34%	2750
August	1st to 10th	Night	17% 11% 4 12% 5% 5% 5% 5% 6% 8% 22%	2737
	11th to 20th	Night	25% 9% 2 8% 4 3 4 3 5% 7% 30%	2791
	21st to end	Night	24% 11% 4 7% 4 3 4 3 6% 7% 27%	3135
September	1st to 10th	Night	20% 11% 4 7% 5% 5% 4 3 5% 7% 30%	1900
	11th to 20th	Night	23% 11% 3 8% 5% 4 4 4 4 6% 28%	2090
	21st to end	Night	20% 11% 4 9% 4 4 3 3 6% 6% 30%	2090
October	1st to 10th	Night	21% 10% 4 9% 6% 4 5% 3 5% 6% 27%	2188
	11th to 20th	Night	22% 14% 4 8% 5% 5% 5% 3 6% 6% 23%	2323
	21st to end	Night	23% 16% 5% 9% 5% 5% 4 3 4 5% 22%	2717
November	1st to 10th	Night	23% 13% 4 10% 6% 5% 5% 4 4 6% 22%	2565
	11th to 20th	Night	22% 16% 6% 9% 5% 5% 4 3 4 5% 20%	2660
	21st to end	Night	20% 16% 5% 10% 5% 6% 5% 4 5% 6% 20%	2717
December	1st to 10th	Night	22% 18% 6% 10% 7% 5% 4 3 4 4 17%	2850
	11th to 20th	Night	30% 15% 5% 11% 6% 5% 5% 3 4 4 12%	3531
	21st to end	Night	21% 14% 5% 12% 6% 5% 5% 4 4 5% 19%	5225

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	40% 41% 6% 7% 4 1	2217
	11th to 20th	Day	41% 43% 4 8% 4	2477
	21st to end	Day	42% 43% 4 7% 4	2783
February	1st to 10th	Day	24% 66% 4 3 2	1647
	11th to 20th	Day	26% 66% 4 3 1	1677
	21st to end	Day	22% 68% 4 3 3 1	1570
March	1st to 10th	Day	38% 44% 6% 8% 3 1	3145
	11th to 20th	Day	46% 44% 5% 3 1	3480
	21st to end	Day	42% 44% 6% 7% 1 1	3817
April	1st to 10th	Day	23% 66% 3 4 3 1	2298
	11th to 20th	Day	23% 67% 4 4 2	2441
	21st to end	Day	25% 66% 3 4 2	2470
May	1st to 10th	Day	45% 44% 5% 4 2	4120
	11th to 20th	Day	44% 44% 6% 5% 1	4461
	21st to end	Day	42% 44% 4 8% 2	5173
June	1st to 10th	Day	26% 66% 2 5% 1	2850
	11th to 20th	Day	21% 67% 5% 5% 2	2850
	21st to end	Day	23% 65% 4 6% 3	2850
July	1st to 10th	Day	44% 38% 8% 7% 2	4675
	11th to 20th	Day	36% 39% 14% 8% 3	4649
	21st to end	Day	23% 38% 17% 18% 4	4662
August	1st to 10th	Day	38% 38% 11% 10% 2	4188
	11th to 20th	Day	28% 39% 14% 17% 2	4085
	21st to end	Day	30% 38% 12% 18% 2	4532
September	1st to 10th	Day	20% 62% 4 10% 4	2276
	11th to 20th	Day	23% 61% 7% 7% 2	2090
	21st to end	Day	22% 62% 6% 6% 3	2090
October	1st to 10th	Day	38% 41% 8% 10% 2	3309
	11th to 20th	Day	27% 39% 10% 15% 8%	3067
	21st to end	Day	35% 41% 9% 11% 4	3092
November	1st to 10th	Day	27% 58% 6% 5% 3	1717
	11th to 20th	Day	28% 62% 4 4 2	1520
	21st to end	Day	30% 61% 4 4 2	1459
December	1st to 10th	Day	29% 62% 4 3 1	1330
	11th to 20th	Day	34% 50% 7% 6% 2	1667
	21st to end	Day	47% 40% 6% 5% 1	2442
January	1st to 10th	Night	43% 41% 6% 5% 3 1	4739
	11th to 20th	Night	36% 46% 8% 8% 2	4492
	21st to end	Night	38% 45% 7% 7% 2	4884
February	1st to 10th	Night	25% 66% 3 4 2 1	2532
	11th to 20th	Night	24% 67% 4 4 1	2398
	21st to end	Night	21% 67% 4 6% 3	1884
March	1st to 10th	Night	36% 45% 7% 9% 2 1	3707
	11th to 20th	Night	41% 48% 6% 4 1	3480
	21st to end	Night	41% 44% 6% 8% 1	3815
April	1st to 10th	Night	23% 66% 3 4 3 1	1878
	11th to 20th	Night	23% 67% 2 5% 3 1	1688
	21st to end	Night	25% 66% 3 4 2	1710
May	1st to 10th	Night	42% 45% 6% 5% 1	2850
	11th to 20th	Night	48% 42% 3 5% 2	2442
	21st to end	Night	42% 44% 6% 5% 3	2413
June	1st to 10th	Night	24% 66% 5% 4 1	1330
	11th to 20th	Night	19% 67% 7% 4 3	1330
	21st to end	Night	22% 66% 5% 6% 2	1330
July	1st to 10th	Night	47% 39% 4 8% 2	2186
	11th to 20th	Night	37% 42% 15% 5% 1	2194
	21st to end	Night	23% 37% 19% 19% 3	2663
August	1st to 10th	Night	31% 41% 16% 11% 1	2726
	11th to 20th	Night	29% 38% 15% 17% 1	2818
	21st to end	Night	33% 39% 9% 16% 2	3134
September	1st to 10th	Night	20% 62% 4 7% 5% 1	1900
	11th to 20th	Night	27% 61% 5% 5% 2	2090
	21st to end	Night	22% 62% 6% 7% 3	2090
October	1st to 10th	Night	40% 39% 11% 8% 2	3656
	11th to 20th	Night	26% 40% 12% 15% 7%	3859
	21st to end	Night	33% 40% 10% 14% 4	4467
November	1st to 10th	Night	28% 58% 5% 7% 2	2565
	11th to 20th	Night	27% 62% 5% 4 2	2660
	21st to end	Night	26% 62% 5% 5% 2	2717
December	1st to 10th	Night	28% 62% 3 5% 3	2850
	11th to 20th	Night	39% 52% 4 4 2	3533
	21st to end	Night	38% 43% 8% 9% 1	5225

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	33% 24% 28% 12% 2 1	370
	11th to 20th	Day	29% 28% 29% 11% 3 1	370
	21st to end	Day	28% 26% 32% 11% 3	407
February	1st to 10th	Day	27% 28% 27% 14% 3	370
	11th to 20th	Day	29% 33% 27% 8% 3	366
	21st to end	Day	23% 33% 30% 12% 2	307
March	1st to 10th	Day	30% 29% 29% 9% 2	370
	11th to 20th	Day	27% 22% 29% 16% 3 2	370
	21st to end	Day	29% 26% 30% 10% 4 1	407
April	1st to 10th	Day	33% 25% 25% 13% 4	488
	11th to 20th	Day	32% 21% 29% 13% 5%	639
	21st to end	Day	31% 23% 27% 15% 3	650
May	1st to 10th	Day	29% 22% 28% 13% 6% 2	653
	11th to 20th	Day	25% 17% 34% 17% 7% 1	674
	21st to end	Day	27% 18% 30% 20% 3 1	735
June	1st to 10th	Day	37% 17% 26% 15% 5%	680
	11th to 20th	Day	30% 15% 30% 18% 7% 1	680
	21st to end	Day	25% 12% 34% 23% 5% 2	680
July	1st to 10th	Day	25% 13% 34% 19% 7% 1	670
	11th to 20th	Day	20% 12% 34% 24% 8% 1	668
	21st to end	Day	22% 14% 31% 25% 8% 1	740
August	1st to 10th	Day	25% 11% 31% 23% 9% 2	675
	11th to 20th	Day	22% 13% 28% 28% 7% 1	667
	21st to end	Day	22% 14% 29% 25% 9% 1	748
September	1st to 10th	Day	20% 13% 30% 26% 9% 2	526
	11th to 20th	Day	28% 19% 27% 19% 5% 1	390
	21st to end	Day	22% 21% 31% 19% 6%	390
October	1st to 10th	Day	23% 18% 33% 20% 6%	390
	11th to 20th	Day	29% 18% 30% 15% 6% 1	390
	21st to end	Day	28% 29% 24% 13% 3 2	429
November	1st to 10th	Day	27% 28% 27% 15% 3 1	392
	11th to 20th	Day	30% 26% 26% 14% 4 1	370
	21st to end	Day	32% 29% 27% 10% 2	370
December	1st to 10th	Day	29% 23% 31% 13% 4	370
	11th to 20th	Day	32% 30% 26% 11% 1	370
	21st to end	Day	25% 26% 32% 14% 3 1	407
January	1st to 10th	Night	29% 26% 30% 12% 3	850
	11th to 20th	Night	28% 25% 30% 12% 4	850
	21st to end	Night	26% 25% 31% 15% 2	935
February	1st to 10th	Night	28% 28% 30% 12% 2	850
	11th to 20th	Night	31% 27% 30% 10% 2	829
	21st to end	Night	23% 25% 32% 16% 4	628
March	1st to 10th	Night	24% 28% 32% 13% 3	745
	11th to 20th	Night	23% 19% 26% 25% 6%	570
	21st to end	Night	32% 21% 29% 15% 3	627
April	1st to 10th	Night	31% 20% 29% 16% 4 1	570
	11th to 20th	Night	29% 20% 30% 16% 4	564
	21st to end	Night	32% 19% 27% 18% 4 1	570
May	1st to 10th	Night	30% 15% 31% 18% 5% 1	570
	11th to 20th	Night	30% 12% 30% 21% 7%	562
	21st to end	Night	29% 15% 31% 20% 4	616
June	1st to 10th	Night	33% 14% 27% 20% 5%	570
	11th to 20th	Night	29% 11% 28% 25% 7%	570
	21st to end	Night	25% 10% 36% 21% 6% 1	570
July	1st to 10th	Night	23% 12% 36% 23% 5% 1	556
	11th to 20th	Night	23% 9% 39% 24% 5%	552
	21st to end	Night	23% 10% 36% 24% 8%	623
August	1st to 10th	Night	29% 7% 29% 27% 8% 1	568
	11th to 20th	Night	24% 10% 30% 29% 6%	562
	21st to end	Night	24% 11% 32% 26% 7%	627
September	1st to 10th	Night	22% 12% 30% 28% 8%	570
	11th to 20th	Night	28% 14% 31% 21% 6%	570
	21st to end	Night	26% 15% 31% 22% 6%	570
October	1st to 10th	Night	26% 15% 32% 21% 6%	623
	11th to 20th	Night	29% 20% 27% 18% 6% 1	713
	21st to end	Night	31% 22% 25% 18% 4 1	946
November	1st to 10th	Night	29% 23% 28% 16% 3	878
	11th to 20th	Night	31% 21% 25% 18% 4	850
	21st to end	Night	28% 26% 31% 12% 4	850
December	1st to 10th	Night	28% 23% 29% 15% 5%	850
	11th to 20th	Night	35% 27% 25% 10% 2	850
	21st to end	Night	26% 25% 29% 16% 4 1	935

Page generated at 2024-11-07 07:55:49. Version ac07

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