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 2024-01-13.

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	22% 14% 5% 9% 7% 4 5% 4 4 6% 21%	74610
	Night	22% 14% 5% 9% 7% 4 5% 4 4 5% 20%	75119
Transparency	Day	41% 40% 7% 8% 3	74302
	Night	42% 39% 7% 8% 3	74962
Seeing	Day	27% 20% 29% 17% 5% 1	16966
	Night	28% 20% 30% 18% 5%	23676

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	20% 19% 7% 11% 7% 5% 4 5% 3 5% 13%	1326
	11th to 20th	Day	21% 17% 6% 12% 6% 4 5% 5% 5% 4 14%	1427
	21st to end	Day	20% 15% 7% 12% 9% 5% 5% 3 3 5% 15%	1584
February	1st to 10th	Day	20% 13% 6% 10% 10% 4 7% 4 4 5% 16%	1561
	11th to 20th	Day	21% 15% 5% 11% 9% 4 5% 6% 5% 6% 14%	1580
	21st to end	Day	14% 13% 8% 13% 10% 4 7% 5% 4 5% 15%	1480
March	1st to 10th	Day	18% 15% 8% 12% 9% 5% 6% 3 4 4 16%	1808
	11th to 20th	Day	18% 14% 8% 10% 8% 4 5% 5% 4 5% 20%	1980
	21st to end	Day	22% 17% 8% 12% 8% 3 5% 3 3 4 15%	2178
April	1st to 10th	Day	21% 17% 6% 9% 7% 3 5% 4 4 5% 18%	2177
	11th to 20th	Day	25% 17% 5% 8% 6% 2 3 4 4 4 21%	2311
	21st to end	Day	24% 18% 6% 8% 6% 3 3 3 4 5% 19%	2340
May	1st to 10th	Day	21% 20% 6% 7% 6% 3 5% 4 4 6% 19%	2340
	11th to 20th	Day	22% 16% 6% 8% 6% 3 4 4 4 6% 22%	2502
	21st to end	Day	20% 14% 4 8% 6% 4 5% 4 5% 7% 23%	2918
June	1st to 10th	Day	28% 15% 6% 8% 6% 3 4 3 4 5% 16%	2700
	11th to 20th	Day	25% 14% 4 7% 6% 3 4 5% 5% 6% 22%	2700
	21st to end	Day	22% 14% 5% 7% 6% 2 4 4 4 6% 24%	2700
July	1st to 10th	Day	19% 11% 5% 8% 6% 3 5% 4 5% 7% 27%	2700
	11th to 20th	Day	20% 11% 5% 8% 6% 3 5% 4 5% 6% 26%	2694
	21st to end	Day	20% 11% 5% 8% 7% 4 6% 5% 5% 6% 23%	2745
August	1st to 10th	Day	25% 11% 4 6% 7% 3 4 5% 5% 6% 24%	2381
	11th to 20th	Day	24% 10% 4 7% 6% 4 5% 5% 5% 7% 24%	2305
	21st to end	Day	19% 11% 4 8% 7% 3 6% 5% 5% 7% 26%	2574
September	1st to 10th	Day	19% 10% 4 7% 5% 3 5% 4 5% 7% 30%	2157
	11th to 20th	Day	23% 10% 3 7% 5% 3 5% 4 4 6% 30%	1980
	21st to end	Day	18% 8% 3 6% 6% 4 4 4 5% 7% 34%	1980
October	1st to 10th	Day	20% 12% 3 8% 4 4 5% 4 5% 7% 28%	1887
	11th to 20th	Day	24% 14% 4 8% 7% 3 5% 4 4 4 22%	1757
	21st to end	Day	23% 14% 5% 9% 8% 4 5% 4 4 5% 19%	1782
November	1st to 10th	Day	22% 13% 5% 10% 6% 3 5% 3 4 5% 24%	1637
	11th to 20th	Day	23% 15% 6% 8% 6% 3 4 4 5% 7% 18%	1520
	21st to end	Day	25% 18% 6% 8% 7% 3 4 3 3 6% 17%	1459
December	1st to 10th	Day	23% 17% 6% 9% 7% 4 4 4 4 5% 15%	1330
	11th to 20th	Day	26% 15% 7% 9% 7% 4 4 4 4 4 16%	1668
	21st to end	Day	19% 17% 8% 13% 8% 4 5% 5% 4 5% 14%	2442
January	1st to 10th	Night	20% 15% 7% 11% 9% 4 6% 4 5% 4 15%	2839
	11th to 20th	Night	22% 16% 7% 10% 7% 3 6% 6% 4 5% 15%	2577
	21st to end	Night	20% 14% 6% 11% 7% 4 6% 5% 4 6% 17%	2772
February	1st to 10th	Night	20% 14% 7% 12% 9% 4 5% 4 3 6% 16%	2398
	11th to 20th	Night	22% 13% 5% 11% 8% 4 7% 6% 4 5% 16%	2264
	21st to end	Night	13% 14% 8% 12% 8% 5% 7% 5% 5% 6% 18%	1776
March	1st to 10th	Night	17% 14% 8% 10% 8% 4 6% 4 4 5% 20%	2138
	11th to 20th	Night	15% 13% 6% 11% 8% 5% 6% 5% 5% 6% 21%	1979
	21st to end	Night	24% 16% 7% 11% 7% 4 5% 4 4 3 15%	2178
April	1st to 10th	Night	24% 16% 6% 8% 6% 3 5% 3 3 5% 20%	1780
	11th to 20th	Night	24% 14% 5% 9% 5% 3 4 4 4 5% 23%	1598
	21st to end	Night	26% 21% 5% 8% 5% 2 4 3 3 3 22%	1620
May	1st to 10th	Night	24% 14% 6% 8% 7% 4 5% 4 5% 6% 17%	1620
	11th to 20th	Night	23% 13% 5% 6% 7% 3 5% 4 5% 7% 22%	1386
	21st to end	Night	25% 10% 5% 7% 8% 5% 5% 5% 4 5% 21%	1356
June	1st to 10th	Night	26% 15% 4 9% 7% 3 5% 4 4 5% 19%	1260
	11th to 20th	Night	23% 12% 5% 8% 6% 3 5% 4 5% 6% 22%	1260
	21st to end	Night	23% 15% 5% 8% 5% 3 3 5% 5% 7% 21%	1260
July	1st to 10th	Night	20% 13% 4 8% 8% 4 5% 4 5% 7% 21%	1260
	11th to 20th	Night	19% 14% 6% 8% 7% 3 5% 5% 5% 5% 22%	1263
	21st to end	Night	23% 12% 4 9% 7% 3 6% 3 5% 6% 22%	1573
August	1st to 10th	Night	23% 13% 4 6% 6% 3 4 5% 5% 8% 23%	1557
	11th to 20th	Night	25% 12% 4 9% 6% 3 4 4 4 6% 25%	1595
	21st to end	Night	21% 11% 3 6% 6% 3 4 4 6% 7% 28%	1782
September	1st to 10th	Night	19% 11% 4 7% 5% 3 5% 4 5% 7% 30%	1799
	11th to 20th	Night	23% 11% 3 7% 6% 3 4 4 4 6% 29%	1980
	21st to end	Night	20% 10% 4 8% 5% 3 3 3 6% 6% 32%	1980
October	1st to 10th	Night	21% 10% 4 7% 7% 3 5% 4 5% 6% 27%	2072
	11th to 20th	Night	23% 14% 4 7% 6% 4 5% 4 6% 6% 23%	2200
	21st to end	Night	23% 16% 5% 8% 6% 4 5% 4 4 5% 21%	2574
November	1st to 10th	Night	23% 11% 4 8% 7% 4 5% 5% 4 6% 23%	2440
	11th to 20th	Night	23% 14% 7% 8% 6% 4 4 4 4 5% 20%	2660
	21st to end	Night	20% 15% 5% 9% 6% 4 6% 5% 5% 6% 20%	2717
December	1st to 10th	Night	22% 17% 7% 9% 8% 4 4 4 4 5% 17%	2850
	11th to 20th	Night	30% 14% 6% 10% 7% 4 5% 5% 4 4 12%	3531
	21st to end	Night	21% 14% 5% 10% 8% 4 5% 5% 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	47% 42% 5% 4 2	1327
	11th to 20th	Day	44% 45% 4 4 3 1	1427
	21st to end	Day	46% 40% 5% 5% 5%	1584
February	1st to 10th	Day	47% 39% 5% 5% 3	1561
	11th to 20th	Day	44% 41% 6% 7% 2	1587
	21st to end	Day	46% 38% 8% 5% 2 1	1480
March	1st to 10th	Day	48% 38% 6% 6% 2 1	1813
	11th to 20th	Day	43% 39% 7% 8% 3	1980
	21st to end	Day	50% 37% 5% 5% 2 1	2178
April	1st to 10th	Day	45% 38% 6% 8% 3	2177
	11th to 20th	Day	44% 36% 4 9% 6% 1	2311
	21st to end	Day	42% 38% 6% 7% 7%	2340
May	1st to 10th	Day	42% 39% 7% 8% 4	2340
	11th to 20th	Day	42% 41% 7% 7% 3	2506
	21st to end	Day	35% 40% 10% 11% 5%	2918
June	1st to 10th	Day	48% 39% 5% 5% 3	2700
	11th to 20th	Day	41% 40% 8% 7% 4	2700
	21st to end	Day	39% 41% 8% 9% 3	2700
July	1st to 10th	Day	33% 42% 8% 12% 4	2625
	11th to 20th	Day	34% 42% 10% 10% 3	2612
	21st to end	Day	37% 43% 9% 8% 2	2592
August	1st to 10th	Day	39% 38% 8% 12% 4	2367
	11th to 20th	Day	38% 40% 9% 9% 4	2305
	21st to end	Day	33% 42% 11% 11% 3	2574
September	1st to 10th	Day	34% 39% 9% 13% 4	2157
	11th to 20th	Day	33% 39% 7% 12% 8%	1980
	21st to end	Day	29% 41% 12% 14% 4	1980
October	1st to 10th	Day	40% 38% 7% 9% 4 1	1887
	11th to 20th	Day	42% 38% 7% 10% 3	1757
	21st to end	Day	43% 40% 4 9% 3 1	1782
November	1st to 10th	Day	37% 44% 9% 7% 3	1637
	11th to 20th	Day	39% 43% 7% 8% 2	1520
	21st to end	Day	42% 41% 8% 6% 3	1459
December	1st to 10th	Day	43% 42% 5% 8% 2	1330
	11th to 20th	Day	50% 34% 8% 6% 1	1667
	21st to end	Day	56% 29% 8% 7% 1	2442
January	1st to 10th	Night	47% 42% 4 5% 1	2839
	11th to 20th	Night	44% 44% 5% 5% 3	2577
	21st to end	Night	44% 41% 6% 7% 2	2772
February	1st to 10th	Night	48% 38% 6% 6% 2	2398
	11th to 20th	Night	45% 42% 6% 6% 1	2268
	21st to end	Night	46% 38% 7% 6% 3	1776
March	1st to 10th	Night	45% 39% 5% 7% 3	2146
	11th to 20th	Night	42% 39% 9% 8% 3 1	1980
	21st to end	Night	50% 39% 4 5% 2	2178
April	1st to 10th	Night	44% 38% 6% 8% 4	1780
	11th to 20th	Night	41% 38% 7% 9% 5%	1598
	21st to end	Night	43% 37% 5% 8% 6%	1620
May	1st to 10th	Night	45% 38% 7% 7% 3	1620
	11th to 20th	Night	40% 39% 6% 10% 4	1387
	21st to end	Night	38% 41% 8% 9% 4	1357
June	1st to 10th	Night	46% 39% 5% 6% 3	1260
	11th to 20th	Night	42% 39% 8% 8% 2	1260
	21st to end	Night	39% 40% 8% 9% 3	1260
July	1st to 10th	Night	38% 41% 9% 11% 2	1226
	11th to 20th	Night	36% 42% 9% 9% 4	1221
	21st to end	Night	39% 43% 8% 9% 1	1486
August	1st to 10th	Night	38% 40% 11% 8% 3	1546
	11th to 20th	Night	39% 39% 9% 8% 4	1595
	21st to end	Night	33% 41% 11% 13% 2	1782
September	1st to 10th	Night	34% 41% 8% 13% 3 1	1799
	11th to 20th	Night	35% 38% 9% 11% 6%	1980
	21st to end	Night	34% 39% 10% 13% 5%	1980
October	1st to 10th	Night	40% 39% 8% 10% 3	2072
	11th to 20th	Night	41% 38% 9% 9% 3	2200
	21st to end	Night	43% 39% 7% 7% 3 1	2574
November	1st to 10th	Night	36% 45% 9% 7% 3	2440
	11th to 20th	Night	41% 42% 8% 8% 2	2660
	21st to end	Night	37% 43% 9% 7% 3	2717
December	1st to 10th	Night	44% 43% 5% 7% 2	2850
	11th to 20th	Night	54% 35% 5% 4 2	3533
	21st to end	Night	48% 32% 9% 10% 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% 27% 29% 11% 3 1	346
	21st to end	Day	28% 26% 32% 11% 3	374
February	1st to 10th	Day	27% 29% 27% 14% 2	340
	11th to 20th	Day	28% 32% 28% 9% 2	336
	21st to end	Day	21% 33% 30% 13% 2	280
March	1st to 10th	Day	27% 30% 31% 9% 2	340
	11th to 20th	Day	26% 23% 30% 15% 4 2	340
	21st to end	Day	28% 25% 30% 10% 4 1	374
April	1st to 10th	Day	30% 25% 27% 13% 4	447
	11th to 20th	Day	32% 20% 29% 13% 5% 1	589
	21st to end	Day	31% 21% 29% 16% 3	600
May	1st to 10th	Day	28% 23% 28% 13% 6% 2	603
	11th to 20th	Day	24% 17% 35% 17% 7% 1	624
	21st to end	Day	27% 19% 29% 20% 3 1	680
June	1st to 10th	Day	37% 16% 26% 16% 5%	630
	11th to 20th	Day	31% 14% 29% 17% 7% 1	630
	21st to end	Day	24% 12% 34% 23% 5% 2	630
July	1st to 10th	Day	24% 14% 35% 19% 7% 2	620
	11th to 20th	Day	21% 12% 34% 24% 7% 1	618
	21st to end	Day	24% 14% 29% 24% 8% 1	685
August	1st to 10th	Day	26% 10% 30% 23% 9% 2	625
	11th to 20th	Day	22% 14% 28% 27% 7% 1	617
	21st to end	Day	22% 15% 28% 25% 9% 1	693
September	1st to 10th	Day	19% 14% 30% 27% 9% 2	487
	11th to 20th	Day	29% 21% 26% 20% 4 1	360
	21st to end	Day	21% 21% 32% 20% 6%	360
October	1st to 10th	Day	23% 19% 33% 19% 5%	360
	11th to 20th	Day	31% 18% 28% 16% 6% 1	360
	21st to end	Day	29% 28% 24% 13% 4 2	396
November	1st to 10th	Day	27% 28% 26% 15% 3 1	365
	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% 31% 12% 4	811
	21st to end	Night	26% 25% 32% 15% 2	880
February	1st to 10th	Night	28% 30% 31% 11% 1	800
	11th to 20th	Night	31% 27% 31% 10% 2	779
	21st to end	Night	23% 26% 32% 15% 4	592
March	1st to 10th	Night	23% 28% 32% 14% 3	706
	11th to 20th	Night	23% 20% 27% 24% 6%	540
	21st to end	Night	33% 20% 29% 15% 3	594
April	1st to 10th	Night	29% 21% 28% 17% 5% 1	540
	11th to 20th	Night	29% 20% 30% 17% 4	534
	21st to end	Night	34% 17% 27% 18% 4 1	540
May	1st to 10th	Night	30% 14% 31% 19% 5% 1	540
	11th to 20th	Night	29% 11% 30% 21% 8%	532
	21st to end	Night	30% 14% 31% 21% 4	583
June	1st to 10th	Night	33% 13% 28% 20% 6%	540
	11th to 20th	Night	30% 11% 27% 25% 7%	540
	21st to end	Night	26% 11% 35% 21% 7% 1	540
July	1st to 10th	Night	22% 12% 37% 23% 5% 1	526
	11th to 20th	Night	24% 9% 39% 24% 4	522
	21st to end	Night	24% 11% 35% 23% 7%	590
August	1st to 10th	Night	30% 7% 28% 26% 9% 1	538
	11th to 20th	Night	24% 11% 30% 30% 6%	532
	21st to end	Night	24% 11% 32% 26% 7%	594
September	1st to 10th	Night	21% 12% 30% 29% 7%	540
	11th to 20th	Night	28% 14% 31% 21% 6%	540
	21st to end	Night	25% 15% 31% 23% 6%	540
October	1st to 10th	Night	25% 16% 33% 21% 5%	587
	11th to 20th	Night	30% 19% 26% 19% 6% 1	670
	21st to end	Night	31% 21% 24% 18% 4 1	891
November	1st to 10th	Night	29% 24% 28% 16% 3	830
	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 2024-01-10 02:24:59. Version ac07

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