Lilly Bluff Overlook
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lilly Bluff Overlook clear sky chart from 2005-11-06 to 2024-12-09.

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	13% 8% 3 7% 5% 5% 5% 4 6% 7% 37%	101251
	Night	13% 8% 3 7% 5% 4 4 4 5% 7% 41%	98503
Transparency	Day	43% 7% 11% 21% 15% 3	105021
	Night	40% 6% 11% 22% 16% 4	102871
Seeing	Day	18% 14% 24% 22% 15% 7%	14848
	Night	16% 12% 23% 28% 18% 3	24898

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% 13% 5% 9% 4 4 5% 4 5% 6% 28%	2836
	11th to 20th	Day	18% 10% 4 13% 4 5% 5% 3 3 5% 30%	2840
	21st to end	Day	21% 14% 6% 6% 4 3 3 3 4 5% 31%	3168
February	1st to 10th	Day	18% 12% 4 8% 5% 4 3 3 4 5% 33%	1900
	11th to 20th	Day	21% 10% 4 8% 5% 4 4 3 5% 5% 32%	1848
	21st to end	Day	21% 9% 4 7% 5% 4 4 3 4 5% 34%	1570
March	1st to 10th	Day	22% 13% 3 8% 5% 3 4 2 5% 5% 29%	3148
	11th to 20th	Day	15% 8% 2 6% 4 4 3 3 4 5% 47%	3480
	21st to end	Day	15% 9% 3 7% 5% 5% 5% 4 4 6% 39%	3815
April	1st to 10th	Day	13% 9% 2 7% 5% 5% 4 3 5% 6% 41%	2222
	11th to 20th	Day	14% 8% 3 6% 5% 3 3 3 5% 6% 43%	2254
	21st to end	Day	14% 8% 2 6% 5% 4 4 4 5% 7% 41%	2448
May	1st to 10th	Day	18% 9% 3 7% 4 4 5% 4 6% 7% 33%	4082
	11th to 20th	Day	17% 9% 3 8% 5% 4 4 3 6% 6% 35%	4081
	21st to end	Day	11% 7% 2 7% 5% 4 4 5% 7% 9% 39%	4476
June	1st to 10th	Day	10% 7% 3 7% 4 6% 6% 5% 7% 9% 35%	2470
	11th to 20th	Day	5% 5% 2 7% 6% 6% 6% 5% 7% 10% 41%	2470
	21st to end	Day	7% 6% 2 7% 6% 6% 6% 5% 8% 11% 37%	2470
July	1st to 10th	Day	6% 4 2 7% 7% 7% 8% 6% 9% 11% 33%	4120
	11th to 20th	Day	10% 7% 3 8% 6% 6% 6% 6% 7% 9% 33%	4120
	21st to end	Day	15% 12% 5% 12% 7% 7% 6% 5% 7% 7% 18%	4466
August	1st to 10th	Day	6% 5% 3 7% 5% 6% 6% 5% 8% 12% 38%	4104
	11th to 20th	Day	7% 5% 2 7% 5% 6% 6% 6% 9% 12% 36%	3856
	21st to end	Day	6% 4 2 6% 4 5% 6% 4 7% 9% 47%	4180
September	1st to 10th	Day	13% 6% 2 7% 5% 5% 5% 4 6% 7% 39%	2144
	11th to 20th	Day	14% 6% 2 7% 4 5% 6% 3 6% 8% 39%	2090
	21st to end	Day	15% 5% 2 5% 4 4 5% 3 5% 7% 44%	2090
October	1st to 10th	Day	11% 5% 1 6% 4 3 3 4 5% 6% 52%	2090
	11th to 20th	Day	13% 6% 2 5% 3 3 3 2 5% 6% 53%	1983
	21st to end	Day	14% 6% 2 5% 3 3 3 3 5% 7% 48%	2009
November	1st to 10th	Day	10% 6% 3 5% 4 3 4 4 6% 5% 53%	1762
	11th to 20th	Day	13% 7% 2 7% 4 3 4 3 5% 5% 46%	1800
	21st to end	Day	15% 8% 4 6% 4 5% 4 3 5% 5% 43%	1800
December	1st to 10th	Day	18% 11% 3 9% 5% 4 4 2 4 5% 34%	1782
	11th to 20th	Day	14% 12% 4 7% 5% 4 4 4 6% 6% 34%	2153
	21st to end	Day	17% 14% 3 7% 4 4 5% 3 5% 7% 30%	3124
January	1st to 10th	Night	15% 13% 5% 8% 5% 4 4 3 5% 6% 32%	4109
	11th to 20th	Night	19% 11% 4 7% 5% 5% 3 3 4 4 35%	4120
	21st to end	Night	19% 15% 4 6% 4 4 4 4 4 4 33%	4486
February	1st to 10th	Night	17% 8% 3 8% 5% 4 5% 4 5% 7% 35%	2280
	11th to 20th	Night	22% 9% 4 8% 5% 4 4 3 4 5% 33%	2218
	21st to end	Night	21% 10% 4 8% 5% 5% 5% 4 4 5% 31%	1884
March	1st to 10th	Night	21% 13% 3 6% 5% 5% 4 4 5% 5% 30%	3702
	11th to 20th	Night	10% 8% 2 6% 4 4 4 4 5% 6% 47%	3480
	21st to end	Night	15% 8% 2 7% 4 5% 5% 4 5% 6% 40%	3817
April	1st to 10th	Night	13% 5% 2 5% 4 5% 4 4 5% 8% 45%	1973
	11th to 20th	Night	13% 6% 2 6% 4 4 3 3 5% 6% 48%	1875
	21st to end	Night	12% 6% 2 6% 5% 5% 4 3 5% 7% 45%	1730
May	1st to 10th	Night	14% 10% 2 7% 5% 4 4 3 5% 8% 36%	2813
	11th to 20th	Night	15% 10% 3 6% 4 3 4 4 6% 7% 38%	2812
	21st to end	Night	6% 6% 2 7% 6% 4 5% 4 7% 9% 43%	3079
June	1st to 10th	Night	6% 6% 3 6% 5% 5% 5% 6% 7% 8% 43%	1710
	11th to 20th	Night	4 2 2 5% 4 5% 4 5% 7% 12% 51%	1710
	21st to end	Night	6% 5% 2 6% 6% 5% 5% 4 7% 12% 43%	1710
July	1st to 10th	Night	7% 5% 2 6% 5% 5% 5% 5% 9% 11% 39%	2840
	11th to 20th	Night	9% 5% 2 5% 4 4 5% 5% 5% 11% 46%	2840
	21st to end	Night	11% 11% 4 11% 6% 6% 7% 5% 6% 9% 23%	3087
August	1st to 10th	Night	5% 5% 2 6% 4 5% 5% 4 7% 10% 47%	2825
	11th to 20th	Night	6% 6% 2 6% 5% 5% 3 4 7% 9% 47%	2969
	21st to end	Night	6% 3 1 4 3 3 4 4 6% 8% 59%	3476
September	1st to 10th	Night	10% 6% 2 7% 5% 5% 5% 3 5% 7% 45%	2015
	11th to 20th	Night	11% 6% 2 7% 4 4 4 4 5% 8% 46%	2090
	21st to end	Night	12% 5% 2 6% 4 3 3 3 5% 6% 51%	2090
October	1st to 10th	Night	10% 5% 1 5% 3 3 2 2 4 7% 58%	2090
	11th to 20th	Night	13% 5% 2 5% 3 3 3 3 4 6% 52%	2195
	21st to end	Night	12% 7% 2 6% 4 3 3 2 3 6% 50%	2587
November	1st to 10th	Night	10% 6% 3 6% 4 3 4 3 5% 6% 51%	2536
	11th to 20th	Night	12% 8% 2 5% 4 3 5% 3 5% 7% 46%	2600
	21st to end	Night	14% 10% 4 6% 4 3 4 4 4 6% 43%	2600
December	1st to 10th	Night	18% 11% 4 8% 5% 4 4 3 5% 5% 33%	2581
	11th to 20th	Night	15% 11% 5% 9% 4 4 4 3 4 5% 37%	3042
	21st to end	Night	17% 11% 5% 8% 6% 6% 6% 4 6% 6% 25%	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	54% 4 9% 19% 13% 2	2837
	11th to 20th	Day	57% 4 6% 16% 15% 1	2840
	21st to end	Day	55% 4 8% 20% 12% 1	3168
February	1st to 10th	Day	53% 5% 7% 18% 16% 2	1900
	11th to 20th	Day	54% 5% 7% 18% 13% 3	1858
	21st to end	Day	52% 5% 8% 14% 15% 5%	1570
March	1st to 10th	Day	57% 5% 7% 15% 11% 6%	3148
	11th to 20th	Day	40% 4 8% 27% 16% 6%	3480
	21st to end	Day	46% 5% 8% 26% 13% 2	3815
April	1st to 10th	Day	43% 5% 12% 22% 16% 3	2222
	11th to 20th	Day	42% 4 9% 18% 24% 3	2254
	21st to end	Day	42% 6% 11% 25% 14% 1	2448
May	1st to 10th	Day	49% 7% 10% 22% 10% 1	4120
	11th to 20th	Day	47% 9% 10% 24% 8%	4085
	21st to end	Day	40% 8% 13% 21% 16% 2	4489
June	1st to 10th	Day	42% 9% 15% 19% 12% 2	2470
	11th to 20th	Day	35% 10% 17% 21% 14% 2	2470
	21st to end	Day	37% 10% 17% 19% 13% 4	2470
July	1st to 10th	Day	38% 14% 19% 19% 10% 1	4055
	11th to 20th	Day	43% 10% 16% 23% 6% 2	4051
	21st to end	Day	63% 9% 10% 13% 5% 1	4324
August	1st to 10th	Day	34% 12% 16% 29% 9%	4091
	11th to 20th	Day	34% 11% 18% 23% 13% 1	3895
	21st to end	Day	29% 10% 14% 34% 11% 2	4179
September	1st to 10th	Day	42% 8% 12% 18% 16% 5%	2144
	11th to 20th	Day	40% 8% 13% 20% 17% 2	2090
	21st to end	Day	38% 6% 10% 22% 18% 5%	2090
October	1st to 10th	Day	22% 6% 8% 20% 33% 11%	3480
	11th to 20th	Day	23% 3 8% 23% 30% 11%	3275
	21st to end	Day	28% 4 11% 25% 22% 10%	3285
November	1st to 10th	Day	33% 5% 8% 23% 26% 5%	1762
	11th to 20th	Day	39% 4 6% 22% 23% 6%	1800
	21st to end	Day	43% 4 9% 21% 20% 3	1800
December	1st to 10th	Day	53% 4 5% 21% 14% 2	1782
	11th to 20th	Day	49% 5% 10% 17% 16% 2	2150
	21st to end	Day	52% 5% 11% 20% 11% 2	3124
January	1st to 10th	Night	50% 3 12% 19% 14% 2	4109
	11th to 20th	Night	52% 4 8% 15% 17% 4	4120
	21st to end	Night	55% 3 8% 16% 17% 1	4486
February	1st to 10th	Night	49% 5% 10% 19% 15% 2	2280
	11th to 20th	Night	53% 4 7% 18% 13% 5%	2219
	21st to end	Night	54% 6% 6% 15% 15% 4	1884
March	1st to 10th	Night	54% 5% 12% 12% 14% 4	3702
	11th to 20th	Night	37% 5% 8% 27% 15% 9%	3480
	21st to end	Night	44% 5% 9% 25% 15% 2	3817
April	1st to 10th	Night	36% 6% 12% 24% 19% 3	1973
	11th to 20th	Night	37% 5% 10% 20% 22% 6%	1875
	21st to end	Night	38% 6% 12% 29% 14% 1	1730
May	1st to 10th	Night	45% 9% 11% 24% 9% 1	2840
	11th to 20th	Night	42% 9% 14% 21% 13% 1	2813
	21st to end	Night	34% 11% 14% 24% 16% 1	3087
June	1st to 10th	Night	35% 10% 15% 25% 13% 2	1710
	11th to 20th	Night	24% 9% 22% 28% 15% 2	1710
	21st to end	Night	33% 11% 15% 24% 13% 4	1710
July	1st to 10th	Night	34% 13% 21% 22% 9% 1	2795
	11th to 20th	Night	31% 9% 20% 29% 8% 3	2786
	21st to end	Night	54% 11% 13% 14% 6% 1	2988
August	1st to 10th	Night	28% 10% 16% 33% 12% 1	2814
	11th to 20th	Night	29% 11% 20% 26% 13% 1	2996
	21st to end	Night	22% 7% 14% 42% 14% 1	3476
September	1st to 10th	Night	37% 7% 13% 20% 17% 6%	2015
	11th to 20th	Night	36% 9% 11% 20% 21% 2	2090
	21st to end	Night	34% 7% 9% 23% 22% 5%	2090
October	1st to 10th	Night	22% 7% 10% 21% 29% 12%	3480
	11th to 20th	Night	22% 4 7% 25% 28% 15%	3642
	21st to end	Night	25% 3 9% 25% 26% 11%	4261
November	1st to 10th	Night	34% 5% 8% 21% 24% 7%	2536
	11th to 20th	Night	37% 4 7% 20% 24% 7%	2600
	21st to end	Night	43% 3 7% 24% 19% 4	2600
December	1st to 10th	Night	52% 5% 8% 18% 14% 3	2581
	11th to 20th	Night	49% 3 9% 19% 18% 3	3044
	21st to end	Night	55% 6% 12% 16% 11% 1	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% 29% 30% 12% 1	270
	11th to 20th	Day	35% 29% 22% 11% 2 1	270
	21st to end	Day	25% 31% 33% 8% 2	297
February	1st to 10th	Day	31% 25% 30% 11% 1	270
	11th to 20th	Day	41% 27% 26% 4 1 1	270
	21st to end	Day	42% 25% 28% 4 1	225
March	1st to 10th	Day	30% 23% 34% 13% 1	285
	11th to 20th	Day	25% 27% 27% 16% 4	460
	21st to end	Day	25% 23% 31% 16% 5%	506
April	1st to 10th	Day	26% 20% 25% 20% 9% 1	460
	11th to 20th	Day	20% 19% 32% 18% 9% 1	452
	21st to end	Day	21% 15% 33% 18% 12% 1	460
May	1st to 10th	Day	19% 17% 33% 18% 9% 4	463
	11th to 20th	Day	15% 12% 26% 26% 13% 7%	487
	21st to end	Day	14% 9% 22% 28% 16% 11%	529
June	1st to 10th	Day	12% 9% 23% 28% 17% 12%	490
	11th to 20th	Day	5% 5% 18% 31% 28% 13%	490
	21st to end	Day	8% 5% 24% 30% 21% 12%	490
July	1st to 10th	Day	9% 4 16% 28% 24% 19%	485
	11th to 20th	Day	9% 7% 15% 26% 25% 18%	484
	21st to end	Day	12% 7% 13% 25% 29% 14%	532
August	1st to 10th	Day	13% 4 19% 27% 22% 15%	486
	11th to 20th	Day	10% 4 19% 32% 25% 10%	479
	21st to end	Day	11% 5% 10% 26% 31% 18%	539
September	1st to 10th	Day	10% 5% 15% 27% 30% 12%	490
	11th to 20th	Day	14% 4 14% 28% 28% 11%	490
	21st to end	Day	18% 5% 18% 28% 24% 8%	490
October	1st to 10th	Day	11% 9% 22% 27% 23% 8%	490
	11th to 20th	Day	16% 14% 28% 23% 17% 3	490
	21st to end	Day	19% 13% 29% 24% 12% 2	458
November	1st to 10th	Day	16% 14% 37% 24% 7% 2	300
	11th to 20th	Day	20% 18% 39% 20% 3	300
	21st to end	Day	19% 21% 36% 17% 6% 1	300
December	1st to 10th	Day	30% 21% 33% 12% 3	294
	11th to 20th	Day	25% 24% 27% 17% 6%	270
	21st to end	Day	31% 23% 33% 11% 2 1	297
January	1st to 10th	Night	21% 24% 31% 20% 4	760
	11th to 20th	Night	27% 23% 27% 18% 4	760
	21st to end	Night	21% 19% 37% 21% 2	836
February	1st to 10th	Night	22% 17% 35% 23% 3	760
	11th to 20th	Night	28% 20% 32% 18% 1	743
	21st to end	Night	28% 24% 29% 18% 1	628
March	1st to 10th	Night	21% 17% 33% 25% 4	760
	11th to 20th	Night	20% 20% 31% 23% 5% 1	760
	21st to end	Night	23% 15% 29% 25% 8%	836
April	1st to 10th	Night	16% 18% 28% 27% 10%	643
	11th to 20th	Night	17% 12% 30% 29% 12% 1	563
	21st to end	Night	13% 10% 32% 34% 10% 1	570
May	1st to 10th	Night	13% 10% 28% 31% 16% 2	570
	11th to 20th	Night	11% 9% 20% 35% 21% 4	561
	21st to end	Night	7% 4 18% 34% 32% 6%	617
June	1st to 10th	Night	7% 6% 15% 38% 29% 5%	570
	11th to 20th	Night	3 2 15% 36% 37% 7%	570
	21st to end	Night	6% 3 12% 39% 32% 8%	570
July	1st to 10th	Night	11% 2 7% 31% 40% 9%	555
	11th to 20th	Night	7% 4 8% 27% 44% 10%	552
	21st to end	Night	8% 2 9% 31% 41% 9%	624
August	1st to 10th	Night	8% 3 8% 29% 44% 8%	567
	11th to 20th	Night	7% 3 11% 34% 40% 5%	564
	21st to end	Night	10% 2 7% 28% 41% 12%	627
September	1st to 10th	Night	9% 3 12% 32% 37% 8%	685
	11th to 20th	Night	13% 3 12% 32% 34% 7%	760
	21st to end	Night	14% 4 17% 30% 31% 4	760
October	1st to 10th	Night	12% 7% 18% 27% 30% 7%	760
	11th to 20th	Night	15% 9% 24% 31% 18% 2	760
	21st to end	Night	14% 12% 26% 31% 15% 2	836
November	1st to 10th	Night	13% 12% 21% 35% 17% 3	780
	11th to 20th	Night	14% 18% 29% 27% 11% 1	800
	21st to end	Night	19% 17% 26% 28% 10%	800
December	1st to 10th	Night	23% 20% 28% 24% 5%	795
	11th to 20th	Night	20% 17% 28% 28% 6% 1	760
	21st to end	Night	27% 17% 27% 25% 4	836

Page generated at 2024-12-06 03:54:51. Version ac07

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