Leaking Light Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Leaking Light Observatory clear sky chart from 2005-11-06 to 2024-11-02.

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% 10% 3 7% 5% 4 4 4 6% 7% 34%	100819
	Night	16% 10% 3 8% 5% 4 4 3 5% 6% 35%	98080
Transparency	Day	48% 5% 10% 22% 13% 2	100631
	Night	49% 5% 10% 21% 13% 2	97938
Seeing	Day	22% 13% 26% 22% 13% 5%	14859
	Night	21% 10% 24% 28% 14% 2	25105

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	20% 19% 8% 10% 5% 3 3 3 4 6% 20%	2836
	11th to 20th	Day	16% 19% 9% 14% 8% 4 3 2 3 3 19%	2840
	21st to end	Day	24% 21% 6% 9% 5% 4 3 3 3 4 16%	3124
February	1st to 10th	Day	22% 14% 3 9% 7% 4 3 3 4 5% 27%	1710
	11th to 20th	Day	19% 15% 4 10% 5% 3 4 3 5% 6% 26%	1748
	21st to end	Day	21% 13% 4 8% 5% 4 3 3 5% 5% 29%	1570
March	1st to 10th	Day	21% 17% 4 7% 4 4 3 3 4 5% 27%	3401
	11th to 20th	Day	14% 8% 3 7% 4 4 4 3 5% 7% 40%	3480
	21st to end	Day	20% 9% 3 7% 4 4 4 4 6% 7% 31%	3815
April	1st to 10th	Day	15% 11% 3 8% 5% 4 5% 4 6% 6% 33%	2114
	11th to 20th	Day	16% 10% 2 7% 4 4 5% 2 5% 7% 38%	2353
	21st to end	Day	20% 8% 2 6% 5% 5% 4 3 6% 7% 33%	2470
May	1st to 10th	Day	21% 10% 4 8% 5% 5% 5% 4 6% 6% 27%	4082
	11th to 20th	Day	18% 9% 3 7% 5% 4 5% 4 5% 7% 32%	4081
	21st to end	Day	11% 6% 2 7% 5% 5% 6% 5% 7% 10% 37%	4476
June	1st to 10th	Day	13% 7% 2 5% 4 6% 5% 5% 7% 9% 38%	2470
	11th to 20th	Day	10% 6% 3 7% 5% 5% 6% 5% 7% 9% 37%	2470
	21st to end	Day	12% 6% 2 6% 5% 4 6% 5% 6% 11% 37%	2470
July	1st to 10th	Day	9% 6% 2 6% 5% 6% 5% 4 7% 9% 40%	4120
	11th to 20th	Day	10% 5% 2 6% 4 4 4 4 6% 10% 43%	4120
	21st to end	Day	15% 8% 3 7% 5% 5% 5% 4 6% 8% 33%	4466
August	1st to 10th	Day	9% 7% 3 8% 5% 6% 6% 4 7% 10% 35%	4104
	11th to 20th	Day	9% 7% 2 7% 5% 5% 6% 4 8% 10% 38%	4044
	21st to end	Day	6% 4 2 5% 4 5% 5% 4 7% 9% 48%	4386
September	1st to 10th	Day	14% 5% 2 5% 4 4 3 3 6% 6% 48%	2162
	11th to 20th	Day	11% 5% 2 6% 4 5% 4 4 6% 7% 46%	2090
	21st to end	Day	19% 9% 3 6% 4 3 4 3 5% 7% 39%	2090
October	1st to 10th	Day	14% 6% 2 5% 4 4 3 4 6% 8% 43%	1967
	11th to 20th	Day	16% 8% 2 6% 5% 3 4 4 5% 6% 41%	1900
	21st to end	Day	22% 7% 3 7% 4 3 3 3 4 5% 39%	2090
November	1st to 10th	Day	12% 6% 3 6% 4 4 4 3 4 6% 49%	1746
	11th to 20th	Day	16% 13% 4 6% 4 4 3 3 5% 6% 36%	1710
	21st to end	Day	17% 12% 4 8% 3 4 4 4 4 6% 34%	1651
December	1st to 10th	Day	24% 16% 5% 10% 5% 3 4 2 5% 5% 23%	1520
	11th to 20th	Day	19% 16% 5% 10% 4 3 3 3 4 6% 25%	2019
	21st to end	Day	23% 19% 5% 10% 5% 5% 5% 4 5% 5% 16%	3124
January	1st to 10th	Night	15% 20% 6% 12% 6% 5% 4 3 4 4 20%	4109
	11th to 20th	Night	19% 17% 6% 13% 6% 5% 4 3 3 4 20%	4120
	21st to end	Night	27% 16% 6% 11% 5% 3 3 2 3 3 20%	4532
February	1st to 10th	Night	20% 14% 4 9% 5% 4 4 3 5% 5% 28%	2470
	11th to 20th	Night	21% 13% 4 8% 6% 4 4 3 4 5% 27%	2315
	21st to end	Night	22% 14% 4 8% 4 4 4 3 4 5% 28%	1884
March	1st to 10th	Night	22% 12% 3 6% 4 4 4 3 4 6% 32%	3451
	11th to 20th	Night	14% 11% 4 7% 5% 4 4 4 5% 6% 37%	3480
	21st to end	Night	18% 9% 3 6% 4 4 3 3 5% 6% 40%	3817
April	1st to 10th	Night	18% 10% 2 7% 4 3 4 4 5% 6% 36%	2065
	11th to 20th	Night	15% 8% 3 6% 4 3 4 3 6% 8% 39%	1792
	21st to end	Night	15% 8% 3 7% 4 4 3 4 5% 7% 40%	1710
May	1st to 10th	Night	25% 11% 3 7% 4 5% 4 3 4 6% 25%	2813
	11th to 20th	Night	17% 9% 3 6% 5% 4 3 3 5% 8% 37%	2812
	21st to end	Night	11% 7% 2 7% 4 4 4 4 6% 9% 42%	3079
June	1st to 10th	Night	10% 5% 2 5% 5% 4 5% 4 5% 9% 45%	1710
	11th to 20th	Night	9% 5% 2 7% 5% 5% 5% 4 7% 9% 43%	1710
	21st to end	Night	12% 5% 2 5% 3 4 4 4 8% 10% 43%	1710
July	1st to 10th	Night	10% 7% 2 7% 5% 5% 5% 4 5% 9% 41%	2840
	11th to 20th	Night	9% 6% 3 6% 5% 4 5% 4 6% 9% 42%	2840
	21st to end	Night	10% 8% 2 8% 5% 5% 6% 5% 6% 8% 38%	3087
August	1st to 10th	Night	10% 7% 3 7% 6% 5% 5% 4 7% 9% 36%	2825
	11th to 20th	Night	11% 7% 3 7% 5% 4 4 4 5% 7% 43%	2785
	21st to end	Night	6% 4 2 6% 4 5% 5% 4 6% 10% 48%	3236
September	1st to 10th	Night	12% 4 1 6% 3 4 4 3 5% 7% 50%	2014
	11th to 20th	Night	9% 5% 1 5% 3 3 5% 3 5% 7% 52%	2090
	21st to end	Night	16% 7% 3 7% 3 4 4 4 5% 6% 42%	2090
October	1st to 10th	Night	13% 5% 2 6% 3 4 4 4 5% 7% 47%	2213
	11th to 20th	Night	15% 7% 1 6% 4 4 4 3 5% 7% 45%	2280
	21st to end	Night	21% 7% 2 6% 4 3 3 3 3 6% 41%	2508
November	1st to 10th	Night	13% 8% 2 5% 4 4 3 3 5% 4 49%	2351
	11th to 20th	Night	17% 10% 3 7% 5% 4 5% 3 5% 7% 36%	2470
	21st to end	Night	19% 11% 3 6% 5% 5% 4 3 4 6% 35%	2522
December	1st to 10th	Night	22% 16% 5% 8% 5% 4 4 3 4 4 25%	2660
	11th to 20th	Night	18% 16% 6% 8% 4 4 4 3 4 5% 27%	3158
	21st to end	Night	21% 18% 5% 10% 5% 5% 4 3 4 5% 20%	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	66% 4 11% 13% 6%	2837
	11th to 20th	Day	70% 4 7% 14% 5%	2840
	21st to end	Day	72% 3 7% 14% 4 1	3124
February	1st to 10th	Day	61% 3 10% 17% 8% 1	1710
	11th to 20th	Day	59% 4 9% 18% 9% 1	1757
	21st to end	Day	57% 4 10% 18% 10% 1	1570
March	1st to 10th	Day	60% 3 8% 20% 7% 1	3401
	11th to 20th	Day	44% 5% 8% 28% 13% 1	3480
	21st to end	Day	50% 5% 8% 23% 13% 1	3815
April	1st to 10th	Day	49% 5% 10% 19% 13% 3	2114
	11th to 20th	Day	45% 4 11% 18% 18% 4	2353
	21st to end	Day	48% 6% 11% 20% 12% 2	2470
May	1st to 10th	Day	56% 6% 9% 20% 8% 1	4120
	11th to 20th	Day	50% 6% 10% 20% 13% 1	4085
	21st to end	Day	39% 8% 14% 20% 14% 4	4489
June	1st to 10th	Day	41% 6% 13% 24% 15% 1	2470
	11th to 20th	Day	41% 7% 14% 21% 15% 1	2470
	21st to end	Day	39% 9% 14% 23% 14% 1	2470
July	1st to 10th	Day	40% 7% 12% 23% 15% 3	4055
	11th to 20th	Day	35% 6% 10% 32% 16% 1	4051
	21st to end	Day	48% 6% 10% 18% 15% 3	4324
August	1st to 10th	Day	41% 8% 13% 28% 10%	4091
	11th to 20th	Day	38% 8% 9% 30% 15% 1	4083
	21st to end	Day	30% 6% 13% 29% 19% 2	4386
September	1st to 10th	Day	36% 6% 10% 21% 22% 5%	2162
	11th to 20th	Day	35% 6% 10% 26% 20% 3	2090
	21st to end	Day	46% 5% 8% 22% 19% 1	2090
October	1st to 10th	Day	37% 6% 11% 24% 21% 2	1967
	11th to 20th	Day	43% 4 9% 27% 16% 1	1900
	21st to end	Day	48% 3 9% 23% 17% 1	2090
November	1st to 10th	Day	38% 3 10% 28% 17% 4	1746
	11th to 20th	Day	49% 3 9% 20% 16% 3	1710
	21st to end	Day	51% 3 9% 22% 13% 1	1651
December	1st to 10th	Day	65% 4 9% 18% 4 1	1520
	11th to 20th	Day	61% 4 9% 19% 7%	2016
	21st to end	Day	69% 5% 11% 11% 4	3124
January	1st to 10th	Night	66% 4 9% 15% 7%	4109
	11th to 20th	Night	68% 4 9% 14% 4 1	4120
	21st to end	Night	69% 3 7% 16% 4 1	4532
February	1st to 10th	Night	59% 4 10% 18% 9% 1	2470
	11th to 20th	Night	59% 4 9% 17% 11% 1	2317
	21st to end	Night	60% 4 9% 16% 8% 3	1884
March	1st to 10th	Night	54% 3 6% 23% 13% 1	3451
	11th to 20th	Night	45% 6% 8% 27% 12% 1	3480
	21st to end	Night	45% 4 7% 27% 15% 2	3817
April	1st to 10th	Night	49% 4 9% 20% 16% 3	2065
	11th to 20th	Night	41% 5% 11% 21% 16% 6%	1792
	21st to end	Night	43% 5% 11% 22% 17% 2	1710
May	1st to 10th	Night	58% 6% 9% 15% 9% 2	2840
	11th to 20th	Night	47% 7% 10% 22% 12% 1	2813
	21st to end	Night	36% 8% 13% 25% 13% 5%	3087
June	1st to 10th	Night	35% 8% 10% 27% 17% 3	1710
	11th to 20th	Night	36% 8% 14% 22% 17% 3	1710
	21st to end	Night	34% 8% 15% 23% 18% 2	1710
July	1st to 10th	Night	40% 6% 9% 23% 17% 4	2795
	11th to 20th	Night	36% 7% 12% 28% 15% 2	2786
	21st to end	Night	43% 8% 9% 20% 16% 4	2988
August	1st to 10th	Night	43% 7% 14% 25% 10% 1	2814
	11th to 20th	Night	39% 6% 9% 23% 21% 1	2812
	21st to end	Night	31% 7% 12% 29% 19% 3	3236
September	1st to 10th	Night	33% 6% 11% 21% 22% 7%	2014
	11th to 20th	Night	30% 6% 11% 25% 25% 3	2090
	21st to end	Night	41% 6% 11% 20% 21% 2	2090
October	1st to 10th	Night	35% 6% 11% 26% 20% 3	2213
	11th to 20th	Night	39% 4 9% 25% 20% 3	2280
	21st to end	Night	45% 4 7% 24% 18% 3	2508
November	1st to 10th	Night	38% 4 10% 22% 21% 5%	2351
	11th to 20th	Night	48% 3 9% 20% 16% 3	2470
	21st to end	Night	52% 3 9% 22% 12% 1	2522
December	1st to 10th	Night	63% 3 9% 19% 5% 1	2660
	11th to 20th	Night	59% 4 11% 19% 7% 1	3160
	21st to end	Night	66% 4 9% 16% 5%	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	33% 21% 32% 10% 3 1	270
	11th to 20th	Day	38% 23% 29% 9% 2	270
	21st to end	Day	34% 26% 28% 8% 4	297
February	1st to 10th	Day	37% 21% 29% 10% 3	270
	11th to 20th	Day	42% 25% 27% 4 2	270
	21st to end	Day	37% 22% 35% 5% 1	225
March	1st to 10th	Day	30% 20% 28% 18% 4	437
	11th to 20th	Day	28% 23% 30% 13% 5% 1	460
	21st to end	Day	32% 15% 30% 18% 4	506
April	1st to 10th	Day	27% 20% 29% 16% 7% 1	460
	11th to 20th	Day	28% 17% 27% 18% 8% 3	452
	21st to end	Day	27% 18% 30% 17% 7% 2	460
May	1st to 10th	Day	29% 16% 27% 17% 9% 3	463
	11th to 20th	Day	22% 11% 30% 21% 12% 4	487
	21st to end	Day	13% 10% 26% 28% 17% 6%	529
June	1st to 10th	Day	16% 7% 25% 29% 17% 5%	490
	11th to 20th	Day	14% 10% 22% 30% 17% 7%	490
	21st to end	Day	13% 9% 30% 24% 18% 5%	490
July	1st to 10th	Day	13% 6% 20% 25% 20% 15%	485
	11th to 20th	Day	9% 6% 23% 33% 19% 9%	484
	21st to end	Day	17% 5% 19% 29% 20% 10%	532
August	1st to 10th	Day	11% 6% 18% 33% 22% 10%	486
	11th to 20th	Day	13% 6% 19% 32% 19% 11%	479
	21st to end	Day	12% 4 20% 27% 26% 11%	539
September	1st to 10th	Day	15% 6% 19% 27% 23% 10%	490
	11th to 20th	Day	11% 3 16% 28% 30% 11%	490
	21st to end	Day	26% 9% 22% 22% 17% 3	490
October	1st to 10th	Day	14% 8% 26% 28% 18% 4	490
	11th to 20th	Day	21% 12% 28% 23% 13% 3	490
	21st to end	Day	25% 14% 30% 21% 9% 1	539
November	1st to 10th	Day	18% 14% 35% 21% 9% 3	338
	11th to 20th	Day	27% 18% 26% 20% 7% 1	270
	21st to end	Day	23% 20% 36% 18% 2 1	241
December	1st to 10th	Day	29% 18% 36% 12% 3 1	180
	11th to 20th	Day	30% 21% 30% 16% 3	213
	21st to end	Day	36% 19% 27% 14% 5%	297
January	1st to 10th	Night	27% 20% 29% 20% 4	760
	11th to 20th	Night	34% 15% 28% 21% 3	760
	21st to end	Night	28% 17% 31% 21% 3	836
February	1st to 10th	Night	27% 14% 29% 28% 1	760
	11th to 20th	Night	32% 19% 29% 18% 1	743
	21st to end	Night	32% 17% 31% 19% 2	628
March	1st to 10th	Night	28% 14% 30% 24% 5%	760
	11th to 20th	Night	27% 17% 28% 20% 7% 1	760
	21st to end	Night	27% 16% 29% 22% 6%	836
April	1st to 10th	Night	25% 17% 32% 20% 6%	760
	11th to 20th	Night	20% 14% 33% 23% 10% 1	668
	21st to end	Night	18% 9% 35% 32% 6% 1	570
May	1st to 10th	Night	20% 9% 29% 28% 13% 1	570
	11th to 20th	Night	18% 7% 27% 32% 15% 1	561
	21st to end	Night	13% 5% 21% 33% 24% 5%	617
June	1st to 10th	Night	11% 3 25% 37% 23% 1	570
	11th to 20th	Night	11% 4 19% 38% 25% 3	570
	21st to end	Night	13% 4 19% 37% 25% 1	570
July	1st to 10th	Night	13% 2 14% 36% 29% 6%	555
	11th to 20th	Night	9% 4 16% 34% 33% 5%	552
	21st to end	Night	13% 3 15% 35% 30% 4	624
August	1st to 10th	Night	9% 3 10% 41% 34% 2	567
	11th to 20th	Night	11% 3 14% 36% 31% 5%	564
	21st to end	Night	12% 3 13% 34% 33% 6%	687
September	1st to 10th	Night	13% 3 15% 35% 29% 6%	760
	11th to 20th	Night	11% 3 15% 34% 33% 4	760
	21st to end	Night	19% 7% 19% 33% 20% 4	760
October	1st to 10th	Night	16% 5% 21% 33% 23% 3	760
	11th to 20th	Night	19% 8% 28% 28% 16% 1	760
	21st to end	Night	25% 10% 22% 31% 12% 1	836
November	1st to 10th	Night	17% 9% 26% 33% 14% 1	745
	11th to 20th	Night	24% 14% 26% 26% 9% 1	760
	21st to end	Night	25% 12% 26% 28% 7% 1	760
December	1st to 10th	Night	34% 13% 25% 23% 5%	760
	11th to 20th	Night	25% 15% 29% 25% 6%	760
	21st to end	Night	29% 14% 29% 26% 2	836

Page generated at 2024-10-30 01:22:59. Version ac07

Copyright © 2024 Attilla Danko.