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 2024-01-14.

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% 7% 3 6% 5% 3 4 4 5% 7% 43%	74658
	Night	13% 8% 3 5% 4 3 4 4 5% 7% 46%	75119
Transparency	Day	40% 6% 12% 24% 15% 3	74378
	Night	39% 5% 11% 25% 18% 3	74919
Seeing	Day	18% 12% 29% 25% 13% 2	14451
	Night	18% 12% 31% 27% 12% 1	24415

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	12% 8% 4 6% 4 3 3 5% 5% 6% 44%	1678
	11th to 20th	Day	16% 11% 4 8% 4 3 4 4 4 6% 37%	1647
	21st to end	Day	14% 9% 5% 6% 4 2 4 5% 5% 6% 41%	1782
February	1st to 10th	Day	16% 11% 4 8% 7% 3 5% 3 4 5% 35%	1620
	11th to 20th	Day	14% 10% 4 6% 5% 3 4 4 4 5% 40%	1592
	21st to end	Day	17% 11% 3 5% 4 3 4 3 5% 6% 38%	1512
March	1st to 10th	Day	14% 10% 4 7% 5% 2 3 3 4 5% 42%	1980
	11th to 20th	Day	22% 10% 4 6% 5% 3 3 4 3 5% 35%	1980
	21st to end	Day	22% 12% 4 7% 4 2 4 4 5% 6% 29%	2178
April	1st to 10th	Day	12% 7% 3 6% 5% 3 4 5% 5% 6% 44%	2150
	11th to 20th	Day	17% 9% 2 6% 5% 3 4 5% 5% 6% 39%	2134
	21st to end	Day	22% 7% 3 6% 6% 3 4 4 4 6% 34%	2160
May	1st to 10th	Day	20% 6% 3 5% 5% 3 5% 5% 5% 8% 35%	2316
	11th to 20th	Day	16% 6% 3 6% 5% 3 5% 4 5% 7% 40%	2302
	21st to end	Day	13% 7% 3 6% 7% 4 6% 5% 7% 8% 34%	2721
June	1st to 10th	Day	8% 4 2 4 5% 4 5% 6% 5% 10% 46%	2520
	11th to 20th	Day	7% 5% 2 6% 5% 4 5% 6% 6% 10% 44%	2520
	21st to end	Day	5% 3 2 4 5% 3 5% 5% 7% 9% 53%	2520
July	1st to 10th	Day	10% 4 2 4 5% 3 6% 7% 7% 10% 41%	2480
	11th to 20th	Day	4 3 2 4 5% 3 6% 6% 7% 10% 51%	2340
	21st to end	Day	9% 5% 2 5% 6% 4 6% 6% 8% 9% 41%	2546
August	1st to 10th	Day	7% 5% 3 5% 5% 4 6% 6% 8% 10% 42%	2328
	11th to 20th	Day	9% 5% 2 5% 5% 3 5% 6% 6% 8% 46%	2252
	21st to end	Day	8% 5% 2 4 4 3 4 4 5% 8% 53%	2376
September	1st to 10th	Day	11% 5% 3 5% 4 3 4 5% 5% 7% 49%	2160
	11th to 20th	Day	11% 5% 2 5% 4 2 3 4 4 7% 52%	2127
	21st to end	Day	7% 5% 2 3 5% 3 4 4 6% 7% 54%	1895
October	1st to 10th	Day	11% 4 3 4 4 3 4 3 5% 5% 54%	1800
	11th to 20th	Day	14% 7% 2 4 3 2 3 3 3 5% 54%	1800
	21st to end	Day	20% 7% 3 5% 4 2 3 3 3 5% 46%	1980
November	1st to 10th	Day	11% 6% 3 4 3 2 3 3 4 5% 56%	1858
	11th to 20th	Day	15% 7% 2 4 4 2 3 3 5% 6% 48%	1663
	21st to end	Day	17% 8% 3 5% 2 2 4 3 4 6% 45%	1520
December	1st to 10th	Day	12% 10% 5% 7% 4 2 3 5% 3 6% 44%	1520
	11th to 20th	Day	14% 10% 5% 5% 5% 3 3 3 3 6% 43%	1918
	21st to end	Day	18% 17% 5% 10% 5% 2 4 4 3 6% 26%	2783
January	1st to 10th	Night	13% 9% 4 7% 5% 2 4 4 4 5% 44%	2482
	11th to 20th	Night	14% 8% 4 8% 6% 3 4 4 4 6% 41%	2392
	21st to end	Night	12% 10% 4 7% 5% 2 5% 4 5% 6% 41%	2574
February	1st to 10th	Night	14% 11% 5% 7% 5% 2 3 4 5% 7% 36%	2340
	11th to 20th	Night	14% 8% 4 6% 4 3 3 4 4 6% 43%	2254
	21st to end	Night	16% 9% 3 7% 5% 3 4 4 4 5% 41%	1758
March	1st to 10th	Night	14% 9% 3 6% 4 2 3 4 4 5% 46%	1980
	11th to 20th	Night	19% 9% 3 5% 5% 3 3 4 5% 6% 38%	1980
	21st to end	Night	23% 10% 4 5% 5% 3 5% 4 5% 6% 31%	2178
April	1st to 10th	Night	10% 5% 3 5% 4 3 3 4 4 9% 51%	1810
	11th to 20th	Night	14% 8% 3 4 4 3 3 3 5% 8% 45%	1775
	21st to end	Night	18% 7% 3 5% 6% 3 4 4 4 7% 40%	1800
May	1st to 10th	Night	15% 6% 3 6% 5% 2 4 4 5% 8% 42%	1640
	11th to 20th	Night	14% 6% 2 4 5% 3 4 3 5% 8% 45%	1593
	21st to end	Night	12% 7% 4 5% 5% 3 4 5% 5% 9% 41%	1551
June	1st to 10th	Night	5% 3 2 5% 4 3 5% 5% 8% 9% 51%	1440
	11th to 20th	Night	5% 5% 1 5% 4 2 5% 5% 8% 11% 49%	1440
	21st to end	Night	3 3 1 2 3 2 3 5% 7% 9% 62%	1440
July	1st to 10th	Night	8% 3 2 4 5% 3 4 5% 7% 10% 50%	1476
	11th to 20th	Night	3 2 2 4 4 2 4 4 7% 11% 57%	1620
	21st to end	Night	7% 4 2 4 4 3 4 5% 6% 9% 52%	1772
August	1st to 10th	Night	4 3 1 5% 6% 3 4 5% 7% 9% 52%	1611
	11th to 20th	Night	6% 4 2 5% 4 2 3 4 5% 8% 58%	1647
	21st to end	Night	4 4 1 4 4 3 4 4 5% 9% 58%	1980
September	1st to 10th	Night	11% 5% 2 3 4 2 3 4 4 7% 57%	1800
	11th to 20th	Night	10% 4 2 4 3 2 4 4 6% 8% 54%	1829
	21st to end	Night	8% 4 1 4 4 2 3 3 6% 7% 59%	2047
October	1st to 10th	Night	8% 5% 2 3 3 2 3 3 5% 6% 59%	2160
	11th to 20th	Night	15% 5% 2 4 3 2 3 4 4 6% 52%	2160
	21st to end	Night	17% 6% 3 3 4 3 3 3 3 5% 50%	2376
November	1st to 10th	Night	12% 5% 2 3 3 2 3 3 4 6% 58%	2220
	11th to 20th	Night	13% 7% 2 5% 4 2 3 3 3 6% 51%	2511
	21st to end	Night	17% 8% 3 4 4 2 3 3 4 5% 47%	2660
December	1st to 10th	Night	13% 10% 4 5% 5% 3 4 4 4 6% 41%	2660
	11th to 20th	Night	14% 11% 4 7% 4 3 3 3 4 6% 41%	3279
	21st to end	Night	20% 18% 6% 7% 5% 2 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	40% 5% 11% 27% 17% 1	1679
	11th to 20th	Day	49% 4 11% 24% 12%	1647
	21st to end	Day	44% 5% 13% 26% 10% 3	1782
February	1st to 10th	Day	53% 4 10% 21% 11% 1	1620
	11th to 20th	Day	47% 4 12% 20% 14% 3	1601
	21st to end	Day	48% 3 8% 23% 13% 4	1512
March	1st to 10th	Day	46% 3 9% 21% 16% 4	1980
	11th to 20th	Day	53% 4 9% 19% 12% 3	1980
	21st to end	Day	56% 5% 12% 17% 8% 1	2178
April	1st to 10th	Day	41% 5% 11% 24% 17% 2	2150
	11th to 20th	Day	45% 5% 12% 22% 14% 2	2134
	21st to end	Day	51% 4 11% 21% 12% 1	2160
May	1st to 10th	Day	48% 7% 12% 21% 12% 1	2316
	11th to 20th	Day	44% 6% 13% 22% 14% 1	2306
	21st to end	Day	46% 9% 12% 21% 11% 2	2721
June	1st to 10th	Day	33% 8% 15% 28% 15% 2	2520
	11th to 20th	Day	33% 8% 14% 26% 15% 3	2520
	21st to end	Day	26% 7% 16% 31% 16% 4	2520
July	1st to 10th	Day	35% 9% 15% 25% 13% 4	2413
	11th to 20th	Day	26% 9% 16% 26% 20% 3	2271
	21st to end	Day	36% 9% 12% 30% 12% 1	2405
August	1st to 10th	Day	34% 10% 19% 23% 14% 1	2314
	11th to 20th	Day	34% 8% 12% 30% 15% 1	2252
	21st to end	Day	29% 7% 11% 25% 22% 6%	2376
September	1st to 10th	Day	33% 7% 12% 27% 17% 5%	2160
	11th to 20th	Day	33% 5% 8% 25% 27% 2	2127
	21st to end	Day	29% 6% 11% 27% 24% 4	1895
October	1st to 10th	Day	32% 4 10% 26% 24% 4	1800
	11th to 20th	Day	35% 3 7% 28% 22% 5%	1800
	21st to end	Day	43% 4 7% 22% 19% 5%	1980
November	1st to 10th	Day	32% 3 13% 26% 22% 5%	1858
	11th to 20th	Day	38% 4 10% 22% 23% 4	1663
	21st to end	Day	42% 4 8% 28% 16% 2	1520
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	43% 4 12% 23% 17% 1	2482
	11th to 20th	Night	46% 3 12% 25% 12% 1	2392
	21st to end	Night	45% 5% 12% 23% 13% 2	2574
February	1st to 10th	Night	48% 4 11% 22% 13% 2	2340
	11th to 20th	Night	43% 4 11% 22% 16% 3	2255
	21st to end	Night	47% 4 9% 22% 15% 4	1758
March	1st to 10th	Night	41% 4 9% 22% 20% 5%	1980
	11th to 20th	Night	49% 5% 9% 22% 14% 3	1980
	21st to end	Night	54% 6% 11% 20% 8% 1	2178
April	1st to 10th	Night	34% 5% 11% 26% 20% 4	1810
	11th to 20th	Night	39% 5% 10% 25% 17% 5%	1775
	21st to end	Night	45% 5% 10% 24% 15% 1	1800
May	1st to 10th	Night	42% 7% 10% 24% 16% 1	1640
	11th to 20th	Night	38% 7% 13% 24% 16% 2	1594
	21st to end	Night	40% 7% 15% 25% 12% 2	1552
June	1st to 10th	Night	26% 7% 17% 30% 17% 3	1440
	11th to 20th	Night	26% 9% 13% 26% 21% 5%	1440
	21st to end	Night	17% 6% 18% 32% 22% 5%	1440
July	1st to 10th	Night	29% 6% 17% 30% 15% 4	1434
	11th to 20th	Night	21% 7% 15% 30% 25% 3	1566
	21st to end	Night	26% 7% 13% 37% 16% 1	1673
August	1st to 10th	Night	26% 9% 15% 34% 14% 2	1601
	11th to 20th	Night	26% 5% 9% 36% 21% 2	1647
	21st to end	Night	24% 6% 12% 26% 24% 7%	1980
September	1st to 10th	Night	29% 5% 10% 27% 22% 6%	1800
	11th to 20th	Night	28% 6% 10% 23% 27% 5%	1829
	21st to end	Night	26% 4 9% 29% 29% 3	2047
October	1st to 10th	Night	26% 4 10% 28% 26% 6%	2160
	11th to 20th	Night	35% 4 8% 26% 22% 6%	2160
	21st to end	Night	39% 3 8% 23% 23% 5%	2376
November	1st to 10th	Night	29% 3 12% 28% 21% 6%	2220
	11th to 20th	Night	36% 3 6% 25% 24% 5%	2511
	21st to end	Night	41% 3 9% 26% 18% 3	2660
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	37% 19% 37% 7%	249
	21st to end	Day	19% 28% 40% 12% 2	264
February	1st to 10th	Day	31% 23% 35% 10%	240
	11th to 20th	Day	30% 24% 35% 9% 3	240
	21st to end	Day	37% 21% 32% 8% 3	198
March	1st to 10th	Day	23% 30% 35% 10% 1	240
	11th to 20th	Day	40% 14% 30% 14% 2	240
	21st to end	Day	39% 25% 27% 8% 1	264
April	1st to 10th	Day	25% 18% 35% 17% 5%	410
	11th to 20th	Day	29% 17% 31% 19% 4	412
	21st to end	Day	29% 16% 30% 19% 5%	420
May	1st to 10th	Day	23% 17% 37% 18% 5%	579
	11th to 20th	Day	22% 14% 30% 24% 8% 2	625
	21st to end	Day	17% 11% 34% 23% 12% 3	679
June	1st to 10th	Day	9% 6% 26% 33% 23% 3	630
	11th to 20th	Day	10% 6% 29% 37% 17% 2	630
	21st to end	Day	6% 9% 36% 33% 14% 2	630
July	1st to 10th	Day	11% 5% 18% 30% 30% 7%	621
	11th to 20th	Day	5% 3 26% 37% 26% 3	618
	21st to end	Day	8% 3 21% 38% 26% 4	684
August	1st to 10th	Day	10% 3 20% 43% 20% 4	626
	11th to 20th	Day	11% 3 21% 35% 25% 4	566
	21st to end	Day	12% 2 16% 34% 28% 9%	495
September	1st to 10th	Day	14% 3 18% 35% 25% 5%	450
	11th to 20th	Day	9% 5% 23% 36% 19% 9%	417
	21st to end	Day	11% 10% 30% 34% 13% 2	270
October	1st to 10th	Day	16% 11% 30% 27% 13% 3	270
	11th to 20th	Day	20% 21% 36% 20% 3	270
	21st to end	Day	33% 19% 31% 14% 2 1	297
November	1st to 10th	Day	17% 14% 43% 19% 7% 1	270
	11th to 20th	Day	26% 19% 32% 17% 5% 1	270
	21st to end	Day	33% 16% 27% 21% 2	270
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% 23% 33% 18% 4	920
	21st to end	Night	18% 23% 38% 19% 2	990
February	1st to 10th	Night	23% 20% 38% 16% 3	900
	11th to 20th	Night	23% 20% 38% 17% 2	860
	21st to end	Night	29% 19% 33% 16% 3	574
March	1st to 10th	Night	21% 18% 38% 21% 2	540
	11th to 20th	Night	26% 14% 34% 23% 3	540
	21st to end	Night	32% 14% 31% 19% 4	594
April	1st to 10th	Night	17% 17% 37% 24% 4	540
	11th to 20th	Night	23% 13% 34% 24% 6%	533
	21st to end	Night	20% 13% 38% 21% 7%	540
May	1st to 10th	Night	18% 10% 32% 31% 8%	540
	11th to 20th	Night	16% 9% 31% 31% 12% 1	531
	21st to end	Night	14% 9% 27% 29% 18% 2	584
June	1st to 10th	Night	8% 2 22% 38% 28% 2	540
	11th to 20th	Night	7% 3 30% 39% 19% 2	540
	21st to end	Night	3 4 31% 42% 18% 2	540
July	1st to 10th	Night	10% 2 13% 42% 28% 6%	525
	11th to 20th	Night	5% 1 21% 40% 30% 3	522
	21st to end	Night	7% 3 16% 39% 34% 2	591
August	1st to 10th	Night	5% 1 18% 43% 30% 2	537
	11th to 20th	Night	7% 2 17% 42% 28% 3	534
	21st to end	Night	6% 1 17% 37% 35% 5%	594
September	1st to 10th	Night	13% 2 19% 37% 26% 3	540
	11th to 20th	Night	12% 2 19% 34% 28% 5%	540
	21st to end	Night	10% 4 26% 36% 20% 3	607
October	1st to 10th	Night	10% 9% 28% 31% 20% 3	720
	11th to 20th	Night	18% 12% 35% 27% 6%	720
	21st to end	Night	23% 13% 33% 23% 7%	792
November	1st to 10th	Night	14% 14% 36% 27% 10%	740
	11th to 20th	Night	20% 18% 31% 24% 7%	802
	21st to end	Night	23% 15% 34% 22% 5%	950
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 2024-01-11 12:32:04. Version ac07

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