Observatoire de Lac Creux
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire de Lac Creux clear sky chart from 2005-11-06 to 2024-02-15.

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	19% 12% 5% 8% 6% 3 4 4 5% 6% 27%	78111
	Night	18% 13% 5% 8% 7% 3 4 4 4 5% 27%	80960
Transparency	Day	59% 4 10% 18% 8% 1	77816
	Night	60% 4 10% 17% 8% 1	80789
Seeing	Day	27% 13% 30% 20% 8% 2	13368
	Night	26% 11% 25% 26% 10% 1	22566

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	17% 18% 9% 17% 10% 4 4 3 3 2 13%	2517
	11th to 20th	Day	14% 14% 9% 18% 11% 3 3 3 3 5% 18%	2520
	21st to end	Day	12% 18% 10% 12% 8% 4 6% 5% 5% 5% 17%	2772
February	1st to 10th	Day	11% 17% 8% 13% 11% 4 6% 4 3 5% 18%	1709
	11th to 20th	Day	12% 20% 7% 12% 8% 3 4 3 4 4 23%	1613
	21st to end	Day	18% 17% 6% 8% 8% 4 4 5% 4 4 22%	1480
March	1st to 10th	Day	15% 15% 5% 11% 8% 3 5% 4 4 5% 26%	1797
	11th to 20th	Day	15% 15% 6% 9% 8% 4 4 4 3 4 27%	1940
	21st to end	Day	19% 11% 4 7% 6% 4 4 3 4 5% 33%	2317
April	1st to 10th	Day	23% 14% 5% 8% 5% 3 4 3 3 4 28%	2160
	11th to 20th	Day	23% 10% 4 6% 6% 3 3 4 4 5% 32%	2134
	21st to end	Day	22% 12% 4 7% 6% 3 4 3 4 5% 30%	2348
May	1st to 10th	Day	22% 11% 4 6% 6% 4 4 3 4 7% 31%	2520
	11th to 20th	Day	23% 8% 2 6% 6% 3 4 4 4 6% 34%	2478
	21st to end	Day	19% 8% 3 6% 6% 4 4 4 4 6% 34%	2725
June	1st to 10th	Day	24% 7% 3 6% 6% 4 5% 5% 6% 6% 28%	2520
	11th to 20th	Day	18% 6% 2 6% 6% 3 4 5% 7% 8% 35%	2520
	21st to end	Day	23% 7% 3 6% 6% 4 5% 6% 6% 7% 28%	2520
July	1st to 10th	Day	17% 6% 3 6% 6% 3 6% 5% 7% 10% 34%	2520
	11th to 20th	Day	16% 6% 4 6% 6% 3 6% 6% 6% 7% 33%	2520
	21st to end	Day	15% 7% 3 6% 6% 4 6% 5% 6% 9% 34%	2744
August	1st to 10th	Day	17% 8% 3 7% 6% 4 5% 6% 6% 7% 30%	2506
	11th to 20th	Day	17% 6% 3 7% 5% 4 5% 5% 5% 8% 34%	2321
	21st to end	Day	17% 7% 3 6% 6% 3 5% 5% 6% 7% 34%	2376
September	1st to 10th	Day	19% 7% 2 5% 5% 3 4 4 6% 6% 40%	2160
	11th to 20th	Day	19% 7% 3 6% 5% 3 4 4 5% 7% 38%	2142
	21st to end	Day	23% 7% 3 5% 4 3 4 4 5% 8% 35%	1945
October	1st to 10th	Day	23% 10% 2 6% 5% 3 4 5% 6% 7% 29%	1800
	11th to 20th	Day	29% 14% 3 8% 6% 3 4 3 4 5% 22%	1800
	21st to end	Day	29% 16% 3 6% 5% 3 4 4 4 6% 21%	1788
November	1st to 10th	Day	18% 16% 4 7% 5% 2 4 4 5% 6% 29%	1661
	11th to 20th	Day	21% 17% 8% 9% 7% 4 3 4 4 4 18%	1520
	21st to end	Day	23% 18% 8% 11% 7% 3 4 3 2 4 16%	1520
December	1st to 10th	Day	24% 19% 7% 11% 6% 3 4 4 4 5% 13%	1520
	11th to 20th	Day	21% 17% 7% 12% 8% 3 5% 4 4 5% 15%	1906
	21st to end	Day	21% 19% 7% 11% 8% 3 3 3 3 4 16%	2772
January	1st to 10th	Night	17% 20% 8% 11% 8% 3 3 4 3 4 19%	4429
	11th to 20th	Night	14% 15% 6% 13% 14% 4 4 5% 4 5% 16%	4440
	21st to end	Night	12% 17% 10% 12% 7% 6% 6% 5% 4 4 17%	4884
February	1st to 10th	Night	13% 15% 7% 11% 10% 4 5% 5% 5% 5% 21%	2470
	11th to 20th	Night	13% 15% 7% 12% 8% 5% 6% 5% 4 5% 21%	2326
	21st to end	Night	13% 16% 6% 9% 7% 4 5% 5% 4 6% 24%	1776
March	1st to 10th	Night	16% 14% 5% 10% 7% 5% 6% 5% 4 5% 24%	2150
	11th to 20th	Night	17% 15% 6% 8% 6% 3 4 4 4 4 27%	2015
	21st to end	Night	16% 12% 4 7% 5% 2 4 4 4 5% 37%	2038
April	1st to 10th	Night	23% 12% 5% 6% 6% 3 3 4 4 5% 29%	1800
	11th to 20th	Night	19% 9% 3 5% 5% 2 4 4 5% 5% 38%	1775
	21st to end	Night	21% 10% 4 8% 5% 2 4 4 4 6% 32%	1626
May	1st to 10th	Night	21% 10% 3 5% 4 3 3 3 5% 7% 35%	1440
	11th to 20th	Night	20% 8% 3 5% 5% 4 4 5% 5% 5% 37%	1415
	21st to end	Night	18% 6% 3 6% 6% 3 4 4 4 7% 39%	1550
June	1st to 10th	Night	19% 8% 2 6% 5% 4 4 5% 6% 8% 32%	1440
	11th to 20th	Night	17% 6% 3 5% 6% 3 4 5% 6% 7% 38%	1440
	21st to end	Night	19% 7% 3 6% 5% 4 4 4 5% 8% 35%	1440
July	1st to 10th	Night	15% 5% 2 4 5% 3 5% 6% 7% 8% 38%	1440
	11th to 20th	Night	13% 6% 2 5% 4 3 4 5% 6% 8% 43%	1440
	21st to end	Night	12% 6% 3 5% 5% 4 4 6% 6% 9% 40%	1574
August	1st to 10th	Night	13% 6% 3 6% 6% 3 5% 6% 7% 8% 38%	1432
	11th to 20th	Night	14% 7% 3 5% 4 2 4 5% 7% 7% 42%	1558
	21st to end	Night	17% 6% 3 4 5% 3 4 5% 5% 7% 40%	1980
September	1st to 10th	Night	18% 6% 2 6% 4 3 4 4 4 6% 43%	1800
	11th to 20th	Night	19% 6% 2 5% 4 2 4 4 5% 7% 43%	1817
	21st to end	Night	20% 7% 3 5% 5% 3 3 3 4 6% 40%	2011
October	1st to 10th	Night	21% 9% 3 6% 5% 3 4 4 5% 6% 36%	2160
	11th to 20th	Night	27% 12% 3 6% 5% 3 4 4 5% 4 25%	2160
	21st to end	Night	27% 14% 4 6% 6% 3 4 4 4 5% 22%	2566
November	1st to 10th	Night	20% 15% 5% 7% 5% 2 4 3 5% 6% 27%	2416
	11th to 20th	Night	20% 15% 6% 9% 8% 3 4 4 4 5% 22%	2660
	21st to end	Night	24% 18% 6% 11% 7% 3 4 3 4 4 16%	2660
December	1st to 10th	Night	21% 21% 8% 12% 6% 3 4 3 3 4 14%	2660
	11th to 20th	Night	23% 16% 7% 10% 7% 3 3 3 4 4 20%	3288
	21st to end	Night	22% 22% 6% 11% 8% 3 4 3 3 3 16%	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	79% 3 6% 8% 3	2518
	11th to 20th	Day	73% 2 6% 14% 5%	2520
	21st to end	Day	69% 5% 8% 12% 6% 1	2772
February	1st to 10th	Day	70% 3 6% 13% 7% 1	1709
	11th to 20th	Day	66% 3 8% 12% 10% 1	1622
	21st to end	Day	66% 4 7% 14% 9% 1	1480
March	1st to 10th	Day	62% 3 8% 16% 9% 2	1800
	11th to 20th	Day	61% 3 8% 14% 11% 2	1940
	21st to end	Day	55% 3 8% 19% 12% 3	2317
April	1st to 10th	Day	61% 4 7% 15% 10% 3	2160
	11th to 20th	Day	56% 3 7% 20% 11% 2	2134
	21st to end	Day	58% 3 9% 15% 12% 3	2348
May	1st to 10th	Day	54% 4 7% 21% 13% 2	2520
	11th to 20th	Day	52% 3 7% 20% 15% 2	2482
	21st to end	Day	52% 5% 10% 18% 14% 1	2725
June	1st to 10th	Day	55% 6% 10% 18% 10% 1	2520
	11th to 20th	Day	47% 5% 11% 23% 12% 2	2520
	21st to end	Day	55% 5% 13% 19% 9%	2520
July	1st to 10th	Day	45% 6% 14% 26% 9%	2450
	11th to 20th	Day	47% 6% 15% 23% 8%	2445
	21st to end	Day	48% 6% 15% 24% 6%	2591
August	1st to 10th	Day	52% 6% 16% 21% 6%	2492
	11th to 20th	Day	47% 6% 18% 22% 6%	2321
	21st to end	Day	48% 6% 13% 23% 10%	2376
September	1st to 10th	Day	46% 4 14% 24% 11% 1	2160
	11th to 20th	Day	46% 4 15% 25% 9% 1	2142
	21st to end	Day	49% 5% 12% 25% 7% 1	1945
October	1st to 10th	Day	54% 5% 13% 19% 8%	1800
	11th to 20th	Day	66% 4 10% 15% 3 1	1800
	21st to end	Day	67% 4 9% 14% 5% 1	1788
November	1st to 10th	Day	57% 5% 12% 20% 7%	1661
	11th to 20th	Day	70% 4 9% 11% 5%	1520
	21st to end	Day	76% 4 7% 9% 4	1520
December	1st to 10th	Day	75% 3 8% 10% 3	1520
	11th to 20th	Day	74% 4 5% 11% 5%	1906
	21st to end	Day	75% 2 6% 13% 4	2772
January	1st to 10th	Night	72% 3 12% 10% 2	4429
	11th to 20th	Night	71% 4 9% 11% 4 1	4440
	21st to end	Night	72% 3 8% 10% 6% 1	4884
February	1st to 10th	Night	66% 3 9% 15% 6% 1	2470
	11th to 20th	Night	68% 5% 7% 14% 7% 1	2328
	21st to end	Night	62% 4 8% 17% 9% 1	1776
March	1st to 10th	Night	64% 4 7% 15% 8% 1	2160
	11th to 20th	Night	61% 4 8% 16% 10% 1	2016
	21st to end	Night	51% 5% 7% 22% 12% 4	2038
April	1st to 10th	Night	59% 4 7% 16% 12% 2	1800
	11th to 20th	Night	49% 4 8% 23% 14% 2	1775
	21st to end	Night	54% 4 8% 18% 14% 3	1626
May	1st to 10th	Night	49% 4 8% 19% 16% 3	1440
	11th to 20th	Night	51% 4 7% 19% 15% 4	1416
	21st to end	Night	48% 4 10% 22% 14% 2	1551
June	1st to 10th	Night	49% 6% 12% 22% 10%	1440
	11th to 20th	Night	45% 5% 12% 24% 11% 3	1440
	21st to end	Night	49% 5% 14% 21% 10% 1	1440
July	1st to 10th	Night	41% 7% 16% 24% 11% 1	1400
	11th to 20th	Night	41% 5% 16% 28% 10% 1	1392
	21st to end	Night	42% 7% 18% 26% 8%	1486
August	1st to 10th	Night	44% 6% 18% 26% 6%	1422
	11th to 20th	Night	41% 7% 20% 25% 8%	1558
	21st to end	Night	44% 5% 16% 27% 8%	1980
September	1st to 10th	Night	43% 5% 15% 26% 12%	1800
	11th to 20th	Night	42% 5% 17% 29% 7%	1817
	21st to end	Night	46% 5% 13% 27% 8%	2011
October	1st to 10th	Night	51% 4 10% 24% 10% 1	2160
	11th to 20th	Night	62% 5% 11% 17% 5%	2160
	21st to end	Night	65% 4 9% 16% 5% 1	2566
November	1st to 10th	Night	60% 4 12% 18% 6%	2416
	11th to 20th	Night	67% 4 10% 12% 5% 1	2660
	21st to end	Night	74% 4 7% 12% 3	2660
December	1st to 10th	Night	76% 4 7% 10% 3	2660
	11th to 20th	Night	71% 4 6% 14% 5% 1	3288
	21st to end	Night	75% 3 5% 12% 5%	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	21% 17% 44% 14% 3	180
	11th to 20th	Day	23% 16% 38% 15% 6% 2	180
	21st to end	Day	24% 15% 34% 19% 8%	198
February	1st to 10th	Day	27% 25% 36% 10% 3	270
	11th to 20th	Day	27% 19% 43% 10% 1	256
	21st to end	Day	33% 20% 29% 14% 4	346
March	1st to 10th	Day	27% 15% 32% 19% 6%	420
	11th to 20th	Day	27% 18% 33% 17% 4 1	420
	21st to end	Day	29% 18% 27% 17% 6% 2	462
April	1st to 10th	Day	33% 14% 26% 18% 8% 1	420
	11th to 20th	Day	33% 14% 24% 16% 9% 4	412
	21st to end	Day	32% 15% 28% 17% 7%	420
May	1st to 10th	Day	31% 14% 26% 21% 5% 2	423
	11th to 20th	Day	27% 14% 29% 19% 10% 3	447
	21st to end	Day	25% 16% 31% 19% 7% 1	485
June	1st to 10th	Day	31% 8% 37% 16% 7% 1	450
	11th to 20th	Day	24% 12% 30% 21% 11% 3	450
	21st to end	Day	27% 8% 28% 24% 11% 2	450
July	1st to 10th	Day	18% 6% 33% 31% 10% 2	445
	11th to 20th	Day	18% 10% 31% 28% 10% 3	444
	21st to end	Day	16% 7% 30% 32% 13% 2	488
August	1st to 10th	Day	21% 6% 26% 31% 11% 4	446
	11th to 20th	Day	21% 5% 26% 27% 14% 7%	439
	21st to end	Day	20% 11% 29% 19% 14% 7%	495
September	1st to 10th	Day	24% 10% 26% 22% 11% 7%	450
	11th to 20th	Day	24% 9% 26% 21% 15% 6%	450
	21st to end	Day	25% 10% 26% 20% 14% 6%	450
October	1st to 10th	Day	30% 12% 24% 19% 12% 3	450
	11th to 20th	Day	36% 13% 26% 17% 6% 2	450
	21st to end	Day	40% 8% 26% 19% 6% 1	399
November	1st to 10th	Day	35% 12% 29% 18% 5% 1	355
	11th to 20th	Day	31% 17% 36% 9% 6% 1	180
	21st to end	Day	30% 23% 35% 8% 4 1	180
December	1st to 10th	Day	34% 11% 31% 17% 7%	180
	11th to 20th	Day	31% 22% 31% 13% 2 2	180
	21st to end	Day	33% 15% 31% 15% 3 3	198
January	1st to 10th	Night	31% 12% 30% 21% 5% 1	760
	11th to 20th	Night	30% 13% 27% 23% 7%	760
	21st to end	Night	20% 10% 30% 30% 9% 1	836
February	1st to 10th	Night	20% 15% 30% 28% 6% 1	760
	11th to 20th	Night	23% 14% 34% 22% 5% 1	722
	21st to end	Night	23% 17% 28% 27% 4	592
March	1st to 10th	Night	24% 13% 29% 26% 7%	720
	11th to 20th	Night	26% 16% 26% 25% 7% 1	720
	21st to end	Night	22% 14% 29% 24% 9% 1	792
April	1st to 10th	Night	32% 12% 21% 29% 6%	720
	11th to 20th	Night	26% 11% 28% 23% 11% 1	711
	21st to end	Night	28% 12% 24% 26% 10%	546
May	1st to 10th	Night	27% 6% 28% 27% 11% 1	360
	11th to 20th	Night	25% 7% 28% 29% 11%	354
	21st to end	Night	23% 7% 30% 31% 7% 1	389
June	1st to 10th	Night	24% 5% 30% 32% 8% 1	360
	11th to 20th	Night	20% 6% 21% 37% 15% 1	360
	21st to end	Night	22% 5% 23% 35% 15%	360
July	1st to 10th	Night	15% 4 24% 42% 14%	350
	11th to 20th	Night	17% 2 19% 41% 20% 1	348
	21st to end	Night	13% 4 22% 43% 16% 2	394
August	1st to 10th	Night	16% 4 17% 39% 23% 1	358
	11th to 20th	Night	18% 3 16% 34% 28% 2	494
	21st to end	Night	22% 5% 21% 30% 20% 3	792
September	1st to 10th	Night	23% 5% 22% 32% 17% 1	720
	11th to 20th	Night	24% 4 21% 30% 19% 1	720
	21st to end	Night	26% 7% 22% 26% 17% 2	720
October	1st to 10th	Night	27% 8% 26% 25% 12% 1	720
	11th to 20th	Night	37% 10% 23% 21% 8% 1	720
	21st to end	Night	36% 10% 23% 24% 6%	792
November	1st to 10th	Night	31% 12% 27% 21% 8% 1	740
	11th to 20th	Night	30% 15% 27% 17% 10% 1	760
	21st to end	Night	37% 16% 20% 20% 6%	760
December	1st to 10th	Night	34% 14% 25% 20% 7% 1	760
	11th to 20th	Night	28% 16% 26% 22% 7% 1	760
	21st to end	Night	36% 14% 23% 21% 5% 1	836

Page generated at 2024-02-12 06:35:33. Version ac07

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