Lake Stars Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Stars Observatory clear sky chart from 2005-11-06 to 2024-11-28.

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	12% 8% 3 6% 4 4 4 3 5% 7% 44%	101330
	Night	12% 8% 3 6% 4 3 4 3 5% 7% 46%	98275
Transparency	Day	38% 5% 11% 25% 17% 3	104978
	Night	38% 5% 11% 25% 18% 3	102767
Seeing	Day	18% 12% 29% 25% 13% 2	15687
	Night	17% 13% 31% 27% 11% 1	25523

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	13% 12% 3 8% 4 4 4 4 4 5% 39%	2792
	11th to 20th	Day	13% 12% 3 10% 4 5% 4 3 4 5% 37%	2850
	21st to end	Day	18% 13% 4 8% 3 3 4 3 4 5% 36%	3135
February	1st to 10th	Day	15% 12% 4 10% 5% 4 4 3 4 5% 35%	1710
	11th to 20th	Day	14% 11% 3 6% 4 4 4 4 4 5% 41%	1683
	21st to end	Day	16% 11% 3 5% 3 5% 3 3 5% 5% 39%	1604
March	1st to 10th	Day	16% 10% 3 6% 3 3 3 2 4 5% 46%	3436
	11th to 20th	Day	14% 8% 2 5% 3 2 3 3 4 6% 50%	3480
	21st to end	Day	17% 13% 3 8% 4 4 3 3 5% 6% 33%	3814
April	1st to 10th	Day	12% 9% 3 6% 5% 4 4 4 5% 6% 43%	2270
	11th to 20th	Day	16% 9% 2 6% 4 4 4 4 6% 6% 41%	2254
	21st to end	Day	22% 8% 2 7% 5% 4 4 3 4 6% 34%	2280
May	1st to 10th	Day	17% 8% 3 7% 5% 4 5% 4 6% 7% 34%	4044
	11th to 20th	Day	15% 8% 3 7% 4 4 4 4 5% 7% 40%	4082
	21st to end	Day	12% 7% 3 6% 5% 5% 5% 4 5% 7% 42%	4820
June	1st to 10th	Day	8% 4 2 5% 4 6% 5% 5% 6% 9% 46%	2660
	11th to 20th	Day	7% 5% 2 7% 5% 5% 5% 5% 6% 10% 45%	2660
	21st to end	Day	5% 3 1 5% 5% 4 5% 4 7% 9% 52%	2660
July	1st to 10th	Day	12% 7% 2 6% 4 4 5% 4 6% 8% 41%	4358
	11th to 20th	Day	4 4 2 6% 4 4 6% 4 6% 10% 49%	4120
	21st to end	Day	7% 4 2 6% 5% 5% 6% 6% 10% 11% 39%	4465
August	1st to 10th	Day	4 4 2 5% 4 4 4 4 7% 11% 51%	4104
	11th to 20th	Day	10% 6% 2 6% 4 4 5% 4 5% 8% 46%	3950
	21st to end	Day	6% 4 2 4 3 4 4 3 6% 9% 55%	4180
September	1st to 10th	Day	10% 5% 2 5% 4 3 4 4 5% 7% 50%	2280
	11th to 20th	Day	11% 6% 2 6% 3 3 4 3 4 7% 51%	2245
	21st to end	Day	7% 6% 2 5% 4 4 4 3 6% 7% 53%	2000
October	1st to 10th	Day	10% 4 2 4 3 3 3 2 5% 5% 56%	1900
	11th to 20th	Day	14% 7% 2 5% 2 3 2 2 3 4 55%	1900
	21st to end	Day	19% 7% 2 6% 3 2 3 2 3 5% 46%	2090
November	1st to 10th	Day	11% 7% 2 5% 3 3 3 2 4 5% 54%	1957
	11th to 20th	Day	15% 8% 2 5% 3 3 3 3 5% 6% 48%	1750
	21st to end	Day	16% 9% 3 6% 2 3 3 3 5% 6% 45%	1576
December	1st to 10th	Day	12% 11% 5% 7% 4 3 4 3 4 6% 43%	1520
	11th to 20th	Day	13% 11% 4 6% 4 4 3 2 4 6% 43%	1918
	21st to end	Day	18% 17% 5% 11% 4 4 3 3 4 6% 26%	2783
January	1st to 10th	Night	11% 11% 5% 13% 5% 4 4 3 3 4 37%	4158
	11th to 20th	Night	12% 9% 3 11% 7% 7% 6% 4 4 4 33%	4120
	21st to end	Night	21% 13% 5% 7% 3 3 3 2 4 5% 34%	4532
February	1st to 10th	Night	14% 12% 4 7% 5% 3 3 4 5% 7% 36%	2470
	11th to 20th	Night	14% 9% 3 7% 4 3 3 3 5% 6% 43%	2383
	21st to end	Night	15% 9% 3 8% 4 3 4 3 4 4 42%	1865
March	1st to 10th	Night	17% 11% 2 6% 3 3 3 2 3 4 45%	3419
	11th to 20th	Night	14% 7% 2 4 3 3 3 3 5% 6% 50%	3480
	21st to end	Night	18% 12% 4 8% 4 4 4 4 4 6% 33%	3817
April	1st to 10th	Night	10% 6% 3 5% 3 4 3 3 4 8% 51%	1910
	11th to 20th	Night	14% 8% 2 4 4 3 3 3 5% 8% 45%	1875
	21st to end	Night	18% 7% 2 6% 5% 4 4 4 5% 6% 40%	1900
May	1st to 10th	Night	17% 8% 3 6% 4 3 3 3 5% 8% 40%	2856
	11th to 20th	Night	13% 8% 2 6% 4 4 4 3 6% 8% 42%	2823
	21st to end	Night	11% 6% 2 5% 4 4 4 4 5% 8% 47%	2743
June	1st to 10th	Night	6% 3 2 5% 4 3 5% 4 8% 9% 50%	1520
	11th to 20th	Night	4 5% 1 5% 3 3 5% 4 9% 11% 50%	1520
	21st to end	Night	3 3 1 3 3 3 3 4 7% 9% 61%	1520
July	1st to 10th	Night	11% 5% 2 7% 4 4 4 3 5% 9% 46%	2594
	11th to 20th	Night	3 3 1 5% 3 4 4 3 6% 11% 57%	2850
	21st to end	Night	6% 5% 2 4 3 3 4 4 7% 10% 52%	3098
August	1st to 10th	Night	3 3 1 4 4 3 3 4 6% 9% 63%	2836
	11th to 20th	Night	9% 6% 2 6% 4 4 4 3 5% 6% 51%	2884
	21st to end	Night	4 3 1 4 3 4 4 3 6% 9% 61%	3476
September	1st to 10th	Night	10% 4 2 3 3 3 3 4 3 7% 58%	1900
	11th to 20th	Night	10% 4 1 4 3 3 5% 3 6% 8% 53%	1931
	21st to end	Night	8% 5% 2 5% 3 3 3 2 5% 6% 58%	2161
October	1st to 10th	Night	7% 5% 1 4 3 3 3 3 5% 6% 60%	2280
	11th to 20th	Night	13% 6% 2 4 3 3 3 3 4 6% 53%	2280
	21st to end	Night	16% 6% 2 4 4 3 3 3 3 5% 51%	2508
November	1st to 10th	Night	12% 5% 2 4 3 2 3 3 4 5% 58%	2340
	11th to 20th	Night	13% 8% 2 5% 3 3 3 2 3 6% 51%	2644
	21st to end	Night	16% 9% 3 5% 3 3 3 2 4 5% 48%	2759
December	1st to 10th	Night	13% 11% 4 6% 4 4 4 3 5% 6% 41%	2660
	11th to 20th	Night	14% 12% 4 7% 4 3 3 2 4 5% 41%	3279
	21st to end	Night	20% 18% 6% 8% 4 3 3 3 3 5% 27%	4884

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	46% 4 9% 27% 13%	2793
	11th to 20th	Day	49% 3 11% 25% 11%	2850
	21st to end	Day	52% 3 9% 18% 15% 3	3135
February	1st to 10th	Day	53% 4 10% 20% 12% 1	1710
	11th to 20th	Day	46% 4 12% 20% 15% 3	1692
	21st to end	Day	47% 4 8% 23% 13% 5%	1604
March	1st to 10th	Day	43% 3 8% 22% 20% 4	3436
	11th to 20th	Day	36% 4 11% 28% 16% 5%	3480
	21st to end	Day	51% 5% 16% 20% 7% 1	3814
April	1st to 10th	Day	41% 5% 10% 24% 17% 2	2270
	11th to 20th	Day	43% 5% 12% 23% 15% 2	2254
	21st to end	Day	51% 4 11% 21% 12% 1	2280
May	1st to 10th	Day	48% 7% 12% 20% 13% 1	4082
	11th to 20th	Day	44% 7% 13% 22% 14%	4086
	21st to end	Day	39% 8% 9% 27% 16% 1	4833
June	1st to 10th	Day	33% 8% 15% 27% 16% 2	2660
	11th to 20th	Day	32% 8% 14% 28% 15% 3	2660
	21st to end	Day	26% 7% 16% 30% 16% 4	2660
July	1st to 10th	Day	40% 7% 12% 24% 15% 3	4291
	11th to 20th	Day	29% 7% 13% 31% 18% 2	4051
	21st to end	Day	32% 10% 20% 27% 9% 1	4325
August	1st to 10th	Day	26% 7% 18% 27% 21%	4090
	11th to 20th	Day	36% 6% 14% 28% 15% 1	3989
	21st to end	Day	27% 6% 13% 37% 14% 4	4179
September	1st to 10th	Day	33% 6% 11% 25% 19% 6%	2280
	11th to 20th	Day	34% 4 8% 25% 26% 2	2245
	21st to end	Day	30% 6% 10% 27% 24% 4	2000
October	1st to 10th	Day	18% 2 6% 20% 40% 14%	3160
	11th to 20th	Day	23% 2 4 23% 39% 9%	3140
	21st to end	Day	35% 3 7% 26% 26% 3	3428
November	1st to 10th	Day	33% 3 12% 25% 22% 4	1957
	11th to 20th	Day	38% 3 9% 22% 23% 5%	1750
	21st to end	Day	41% 4 8% 29% 16% 2	1576
December	1st to 10th	Day	43% 4 10% 29% 13% 1	1520
	11th to 20th	Day	45% 4 8% 26% 15% 2	1915
	21st to end	Day	60% 4 10% 17% 8% 1	2783
January	1st to 10th	Night	51% 3 12% 21% 12% 1	4158
	11th to 20th	Night	55% 4 10% 22% 9% 1	4120
	21st to end	Night	54% 4 10% 20% 11% 1	4532
February	1st to 10th	Night	48% 5% 11% 22% 13% 2	2470
	11th to 20th	Night	43% 4 11% 22% 16% 3	2384
	21st to end	Night	45% 4 8% 21% 16% 5%	1865
March	1st to 10th	Night	44% 3 8% 20% 19% 5%	3419
	11th to 20th	Night	35% 4 10% 25% 23% 3	3480
	21st to end	Night	52% 6% 12% 21% 8% 1	3817
April	1st to 10th	Night	34% 5% 11% 26% 21% 4	1910
	11th to 20th	Night	39% 5% 9% 24% 18% 5%	1875
	21st to end	Night	45% 5% 10% 24% 14% 1	1900
May	1st to 10th	Night	43% 6% 14% 21% 15% 2	2883
	11th to 20th	Night	41% 6% 12% 28% 12% 1	2824
	21st to end	Night	33% 8% 13% 27% 17% 1	2751
June	1st to 10th	Night	28% 7% 17% 29% 16% 4	1520
	11th to 20th	Night	25% 9% 13% 27% 22% 5%	1520
	21st to end	Night	18% 6% 18% 32% 22% 6%	1520
July	1st to 10th	Night	36% 5% 13% 26% 17% 3	2552
	11th to 20th	Night	22% 6% 11% 38% 21% 2	2796
	21st to end	Night	25% 7% 21% 35% 12% 1	2999
August	1st to 10th	Night	18% 6% 19% 31% 24% 2	2826
	11th to 20th	Night	34% 5% 12% 30% 18% 2	2911
	21st to end	Night	21% 5% 14% 39% 17% 4	3476
September	1st to 10th	Night	29% 4 10% 26% 24% 7%	1900
	11th to 20th	Night	28% 6% 10% 23% 27% 5%	1931
	21st to end	Night	27% 4 9% 28% 28% 3	2161
October	1st to 10th	Night	15% 2 6% 22% 43% 12%	3800
	11th to 20th	Night	23% 3 7% 21% 30% 16%	3779
	21st to end	Night	33% 3 6% 30% 25% 3	4120
November	1st to 10th	Night	30% 3 11% 27% 21% 6%	2340
	11th to 20th	Night	36% 3 6% 25% 24% 5%	2644
	21st to end	Night	41% 3 9% 27% 18% 2	2759
December	1st to 10th	Night	44% 5% 11% 23% 15% 1	2660
	11th to 20th	Night	46% 4 9% 26% 14% 1	3281
	21st to end	Night	61% 4 9% 15% 8% 2	4884

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	25% 24% 36% 13% 2	270
	11th to 20th	Day	35% 20% 37% 7% 1	270
	21st to end	Day	21% 26% 38% 14% 1	297
February	1st to 10th	Day	30% 24% 33% 13%	270
	11th to 20th	Day	29% 24% 34% 11% 3	270
	21st to end	Day	36% 22% 33% 7% 2	225
March	1st to 10th	Day	23% 29% 36% 11% 1	270
	11th to 20th	Day	38% 14% 34% 13% 2	270
	21st to end	Day	37% 25% 28% 8% 1	297
April	1st to 10th	Day	27% 18% 34% 16% 5%	450
	11th to 20th	Day	29% 19% 31% 17% 4	452
	21st to end	Day	29% 16% 31% 18% 5%	460
May	1st to 10th	Day	23% 18% 37% 17% 5%	628
	11th to 20th	Day	21% 14% 30% 24% 9% 2	675
	21st to end	Day	16% 11% 36% 23% 11% 3	734
June	1st to 10th	Day	9% 6% 28% 33% 21% 3	680
	11th to 20th	Day	9% 5% 30% 38% 16% 1	680
	21st to end	Day	7% 9% 37% 33% 13% 2	680
July	1st to 10th	Day	11% 5% 20% 30% 28% 6%	671
	11th to 20th	Day	5% 3 26% 37% 25% 3	668
	21st to end	Day	8% 3 22% 37% 25% 5%	739
August	1st to 10th	Day	9% 3 22% 42% 21% 4	676
	11th to 20th	Day	11% 4 22% 36% 23% 4	613
	21st to end	Day	11% 2 15% 34% 29% 9%	539
September	1st to 10th	Day	13% 3 18% 36% 26% 5%	490
	11th to 20th	Day	9% 5% 23% 35% 19% 8%	455
	21st to end	Day	12% 10% 30% 32% 12% 3	300
October	1st to 10th	Day	14% 10% 30% 29% 14% 4	300
	11th to 20th	Day	18% 20% 34% 22% 5%	300
	21st to end	Day	31% 20% 32% 16% 2 1	330
November	1st to 10th	Day	18% 15% 43% 17% 6% 1	300
	11th to 20th	Day	27% 18% 32% 17% 5% 1	300
	21st to end	Day	33% 15% 29% 21% 2	291
December	1st to 10th	Day	18% 24% 34% 17% 5% 1	270
	11th to 20th	Day	26% 21% 35% 16% 3	270
	21st to end	Day	27% 30% 32% 10%	297
January	1st to 10th	Night	22% 19% 35% 20% 4	950
	11th to 20th	Night	22% 24% 33% 17% 4	950
	21st to end	Night	19% 22% 37% 19% 2	1045
February	1st to 10th	Night	23% 20% 37% 17% 3	950
	11th to 20th	Night	22% 20% 38% 18% 2	909
	21st to end	Night	29% 20% 33% 15% 3	609
March	1st to 10th	Night	21% 18% 38% 21% 2	570
	11th to 20th	Night	25% 14% 34% 24% 3	570
	21st to end	Night	31% 14% 32% 19% 4	627
April	1st to 10th	Night	18% 18% 36% 23% 4	570
	11th to 20th	Night	24% 13% 34% 24% 6%	563
	21st to end	Night	21% 14% 38% 21% 7%	570
May	1st to 10th	Night	18% 10% 34% 31% 7%	570
	11th to 20th	Night	15% 9% 30% 32% 12% 1	561
	21st to end	Night	14% 9% 28% 29% 18% 2	617
June	1st to 10th	Night	9% 3 22% 38% 27% 2	570
	11th to 20th	Night	7% 3 31% 39% 19% 2	570
	21st to end	Night	4 4 31% 42% 17% 2	570
July	1st to 10th	Night	11% 2 14% 42% 26% 5%	555
	11th to 20th	Night	5% 1 21% 41% 29% 3	552
	21st to end	Night	7% 3 16% 38% 34% 2	624
August	1st to 10th	Night	5% 1 18% 43% 30% 2	567
	11th to 20th	Night	7% 2 18% 43% 27% 3	564
	21st to end	Night	6% 1 17% 37% 35% 4	627
September	1st to 10th	Night	12% 2 19% 37% 27% 3	570
	11th to 20th	Night	12% 2 19% 35% 28% 4	570
	21st to end	Night	10% 5% 26% 36% 20% 3	641
October	1st to 10th	Night	9% 8% 27% 31% 21% 3	760
	11th to 20th	Night	18% 12% 35% 28% 8%	760
	21st to end	Night	22% 13% 34% 24% 7%	836
November	1st to 10th	Night	14% 14% 36% 27% 9%	780
	11th to 20th	Night	20% 18% 31% 23% 7%	845
	21st to end	Night	23% 16% 34% 22% 5%	986
December	1st to 10th	Night	20% 19% 35% 21% 5%	950
	11th to 20th	Night	26% 14% 34% 23% 3	950
	21st to end	Night	26% 19% 34% 18% 2	1045

Page generated at 2024-11-24 23:22:20. Version ac07

Copyright © 2024 Attilla Danko.