Lac Lovering
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lac Lovering clear sky chart from 2005-11-06 to 2024-01-27.

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	18% 11% 4 8% 7% 3 5% 5% 5% 6% 28%	74895
	Night	17% 12% 5% 9% 7% 4 5% 4 5% 6% 27%	75145
Transparency	Day	57% 4 11% 18% 8% 1	74600
	Night	59% 4 11% 18% 8% 1	74974
Seeing	Day	27% 16% 28% 18% 8% 2	13616
	Night	26% 14% 26% 25% 9% 1	22652

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	15% 18% 9% 15% 9% 5% 6% 3 4 4 12%	1517
	11th to 20th	Day	16% 17% 6% 13% 10% 5% 4 4 4 5% 16%	1520
	21st to end	Day	10% 15% 8% 11% 10% 4 7% 4 5% 5% 20%	1632
February	1st to 10th	Day	13% 18% 7% 13% 11% 6% 6% 4 4 3 15%	1512
	11th to 20th	Day	12% 17% 8% 15% 8% 4 5% 5% 4 4 18%	1747
	21st to end	Day	13% 17% 7% 11% 8% 5% 5% 4 5% 5% 21%	1480
March	1st to 10th	Day	14% 16% 7% 10% 9% 4 5% 4 4 4 25%	1797
	11th to 20th	Day	17% 14% 7% 8% 7% 3 4 4 4 5% 28%	1858
	21st to end	Day	18% 16% 5% 10% 6% 3 4 3 3 4 29%	2353
April	1st to 10th	Day	21% 14% 6% 9% 6% 2 4 4 4 5% 25%	2160
	11th to 20th	Day	19% 12% 4 6% 6% 3 4 4 4 5% 34%	2160
	21st to end	Day	23% 12% 3 7% 5% 3 4 5% 4 6% 26%	2340
May	1st to 10th	Day	22% 10% 3 6% 7% 3 4 3 4 6% 32%	2376
	11th to 20th	Day	19% 8% 3 6% 6% 3 5% 5% 5% 6% 33%	2478
	21st to end	Day	17% 7% 3 6% 6% 4 6% 6% 7% 7% 32%	2725
June	1st to 10th	Day	26% 7% 3 5% 5% 3 5% 5% 6% 7% 27%	2520
	11th to 20th	Day	18% 6% 2 6% 6% 3 5% 5% 6% 8% 35%	2520
	21st to end	Day	21% 8% 3 6% 6% 3 5% 5% 6% 7% 29%	2520
July	1st to 10th	Day	17% 6% 3 6% 6% 3 4 5% 6% 9% 35%	2520
	11th to 20th	Day	15% 6% 3 5% 6% 4 6% 6% 7% 9% 32%	2520
	21st to end	Day	17% 6% 3 5% 6% 4 6% 7% 5% 9% 32%	2744
August	1st to 10th	Day	17% 6% 3 6% 7% 3 6% 6% 6% 8% 32%	2489
	11th to 20th	Day	15% 6% 3 6% 6% 4 6% 6% 6% 10% 33%	2303
	21st to end	Day	16% 7% 3 5% 6% 4 6% 5% 6% 8% 36%	2376
September	1st to 10th	Day	16% 6% 3 6% 6% 3 4 5% 5% 8% 39%	2160
	11th to 20th	Day	18% 6% 3 5% 4 3 4 4 4 7% 43%	2025
	21st to end	Day	18% 7% 3 5% 5% 3 5% 4 6% 9% 35%	1980
October	1st to 10th	Day	22% 11% 3 5% 6% 4 5% 6% 5% 6% 27%	1951
	11th to 20th	Day	19% 12% 3 7% 6% 4 5% 5% 6% 6% 27%	1702
	21st to end	Day	25% 18% 5% 7% 5% 3 4 3 3 3 23%	1782
November	1st to 10th	Day	18% 14% 5% 7% 6% 3 4 5% 4 6% 28%	1671
	11th to 20th	Day	17% 16% 7% 10% 6% 3 5% 5% 4 4 23%	1710
	21st to end	Day	18% 17% 6% 10% 7% 4 4 4 5% 7% 18%	1549
December	1st to 10th	Day	20% 20% 8% 12% 8% 3 3 3 3 3 15%	1520
	11th to 20th	Day	19% 17% 7% 10% 7% 4 4 3 4 5% 20%	1906
	21st to end	Day	23% 15% 7% 13% 7% 3 5% 4 4 3 16%	2772
January	1st to 10th	Night	15% 18% 8% 13% 10% 5% 5% 4 5% 4 13%	2649
	11th to 20th	Night	14% 15% 8% 13% 10% 5% 7% 3 4 4 16%	2660
	21st to end	Night	10% 14% 7% 13% 10% 5% 6% 5% 4 5% 20%	2868
February	1st to 10th	Night	12% 15% 6% 16% 11% 3 6% 4 4 4 17%	2444
	11th to 20th	Night	12% 14% 7% 14% 9% 6% 5% 5% 4 4 20%	2098
	21st to end	Night	13% 16% 6% 9% 7% 5% 6% 4 3 5% 26%	1776
March	1st to 10th	Night	15% 15% 7% 9% 8% 4 5% 4 4 5% 25%	2150
	11th to 20th	Night	18% 13% 5% 8% 7% 3 5% 4 4 5% 28%	2101
	21st to end	Night	18% 12% 5% 9% 6% 3 4 4 3 4 30%	2000
April	1st to 10th	Night	21% 12% 5% 7% 7% 3 5% 4 4 4 27%	1800
	11th to 20th	Night	20% 12% 3 6% 5% 2 5% 5% 4 6% 34%	1749
	21st to end	Night	22% 10% 3 7% 6% 3 5% 4 4 6% 30%	1620
May	1st to 10th	Night	21% 9% 4 6% 6% 3 4 5% 4 6% 32%	1598
	11th to 20th	Night	18% 8% 3 6% 7% 3 5% 4 5% 5% 36%	1415
	21st to end	Night	17% 6% 3 6% 6% 4 5% 5% 5% 7% 36%	1550
June	1st to 10th	Night	25% 8% 2 5% 4 3 4 4 6% 8% 32%	1440
	11th to 20th	Night	18% 6% 4 5% 4 2 5% 6% 6% 8% 37%	1440
	21st to end	Night	19% 7% 3 5% 5% 3 5% 5% 7% 9% 32%	1440
July	1st to 10th	Night	13% 6% 4 6% 5% 3 6% 5% 7% 8% 36%	1440
	11th to 20th	Night	11% 6% 2 4 5% 4 6% 6% 5% 12% 39%	1440
	21st to end	Night	13% 6% 2 6% 5% 4 4 6% 7% 7% 40%	1574
August	1st to 10th	Night	15% 5% 2 5% 4 3 4 5% 7% 11% 39%	1432
	11th to 20th	Night	13% 6% 2 7% 5% 4 6% 6% 5% 8% 38%	1594
	21st to end	Night	14% 6% 2 6% 5% 3 5% 5% 5% 8% 41%	1979
September	1st to 10th	Night	16% 5% 2 6% 5% 4 5% 4 5% 8% 40%	1800
	11th to 20th	Night	16% 5% 2 4 4 2 4 5% 5% 7% 45%	1934
	21st to end	Night	20% 6% 2 4 5% 3 3 4 5% 7% 41%	1980
October	1st to 10th	Night	21% 8% 3 6% 5% 3 4 4 5% 7% 33%	2006
	11th to 20th	Night	20% 11% 3 7% 7% 4 4 5% 5% 5% 28%	2258
	21st to end	Night	24% 12% 4 7% 6% 3 4 5% 4 6% 25%	2574
November	1st to 10th	Night	19% 12% 4 6% 7% 4 5% 4 5% 6% 28%	2407
	11th to 20th	Night	17% 12% 6% 9% 6% 4 4 3 4 5% 28%	2470
	21st to end	Night	17% 15% 8% 11% 7% 3 4 4 4 5% 23%	2627
December	1st to 10th	Night	19% 21% 7% 11% 8% 3 5% 4 3 5% 13%	2660
	11th to 20th	Night	20% 17% 7% 14% 8% 3 5% 4 3 3 15%	3288
	21st to end	Night	23% 17% 6% 11% 7% 4 4 4 3 4 17%	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	78% 2 8% 11% 2	1518
	11th to 20th	Day	73% 5% 7% 10% 5% 1	1520
	21st to end	Day	67% 3 9% 14% 6% 1	1632
February	1st to 10th	Day	75% 3 5% 11% 5% 1	1512
	11th to 20th	Day	72% 3 9% 10% 5% 1	1756
	21st to end	Day	66% 3 9% 12% 7% 2	1480
March	1st to 10th	Day	65% 3 9% 15% 6% 2	1800
	11th to 20th	Day	61% 3 10% 13% 11% 2	1858
	21st to end	Day	62% 3 6% 19% 9% 2	2353
April	1st to 10th	Day	63% 3 8% 16% 9% 2	2160
	11th to 20th	Day	55% 3 7% 21% 13% 1	2160
	21st to end	Day	60% 4 8% 17% 8% 3	2340
May	1st to 10th	Day	55% 3 7% 21% 13% 1	2376
	11th to 20th	Day	52% 4 10% 21% 12% 1	2482
	21st to end	Day	50% 6% 14% 19% 11% 1	2725
June	1st to 10th	Day	56% 5% 13% 18% 8% 1	2520
	11th to 20th	Day	47% 5% 11% 25% 11% 1	2520
	21st to end	Day	54% 7% 12% 19% 8%	2520
July	1st to 10th	Day	45% 6% 14% 25% 10%	2450
	11th to 20th	Day	46% 6% 15% 27% 6%	2445
	21st to end	Day	48% 6% 16% 23% 6% 1	2591
August	1st to 10th	Day	49% 7% 17% 23% 5%	2475
	11th to 20th	Day	46% 6% 19% 20% 9%	2303
	21st to end	Day	45% 6% 14% 24% 12%	2376
September	1st to 10th	Day	44% 5% 14% 27% 10% 1	2160
	11th to 20th	Day	43% 3 12% 28% 14% 1	2025
	21st to end	Day	45% 6% 15% 23% 10% 1	1980
October	1st to 10th	Day	57% 4 11% 19% 8%	1951
	11th to 20th	Day	56% 5% 15% 18% 6%	1702
	21st to end	Day	67% 3 9% 14% 6% 1	1782
November	1st to 10th	Day	58% 5% 11% 18% 7% 1	1671
	11th to 20th	Day	65% 4 11% 12% 7% 2	1710
	21st to end	Day	67% 4 14% 12% 2	1549
December	1st to 10th	Day	75% 3 9% 9% 3	1520
	11th to 20th	Day	68% 4 7% 15% 5%	1906
	21st to end	Day	75% 3 8% 10% 4	2772
January	1st to 10th	Night	76% 3 9% 9% 3	2649
	11th to 20th	Night	75% 4 8% 10% 3	2660
	21st to end	Night	68% 3 8% 14% 6% 1	2868
February	1st to 10th	Night	72% 4 8% 11% 5%	2444
	11th to 20th	Night	70% 3 8% 14% 6%	2100
	21st to end	Night	64% 4 8% 14% 9% 1	1776
March	1st to 10th	Night	64% 3 8% 16% 7% 2	2160
	11th to 20th	Night	60% 4 9% 15% 10% 2	2102
	21st to end	Night	59% 2 7% 20% 10% 2	2000
April	1st to 10th	Night	61% 3 8% 17% 11% 1	1800
	11th to 20th	Night	53% 3 8% 22% 13% 1	1749
	21st to end	Night	57% 3 9% 17% 11% 2	1620
May	1st to 10th	Night	54% 4 6% 19% 14% 2	1598
	11th to 20th	Night	51% 4 9% 18% 15% 2	1416
	21st to end	Night	48% 6% 13% 21% 11% 1	1551
June	1st to 10th	Night	52% 5% 12% 22% 9% 1	1440
	11th to 20th	Night	45% 7% 12% 24% 10% 3	1440
	21st to end	Night	49% 7% 15% 20% 8%	1440
July	1st to 10th	Night	43% 8% 15% 22% 13% 1	1400
	11th to 20th	Night	38% 7% 18% 30% 7%	1392
	21st to end	Night	44% 5% 17% 25% 8%	1486
August	1st to 10th	Night	38% 7% 20% 28% 6%	1422
	11th to 20th	Night	43% 6% 19% 21% 10%	1594
	21st to end	Night	42% 5% 16% 26% 10%	1979
September	1st to 10th	Night	43% 6% 14% 25% 11% 1	1800
	11th to 20th	Night	39% 4 16% 29% 11% 1	1934
	21st to end	Night	42% 6% 14% 26% 11% 2	1980
October	1st to 10th	Night	50% 5% 11% 22% 10% 1	2006
	11th to 20th	Night	57% 5% 12% 20% 5%	2258
	21st to end	Night	61% 5% 11% 15% 7% 1	2574
November	1st to 10th	Night	59% 4 12% 17% 7% 1	2407
	11th to 20th	Night	61% 4 10% 16% 7% 2	2470
	21st to end	Night	67% 4 12% 14% 4	2627
December	1st to 10th	Night	77% 3 9% 9% 2	2660
	11th to 20th	Night	76% 3 6% 10% 5%	3288
	21st to end	Night	75% 3 8% 13% 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	26% 21% 31% 18% 5%	180
	11th to 20th	Day	31% 21% 33% 10% 5% 1	180
	21st to end	Day	26% 23% 29% 15% 6% 1	188
February	1st to 10th	Day	41% 26% 23% 8% 2	192
	11th to 20th	Day	27% 28% 30% 11% 3	415
	21st to end	Day	30% 22% 30% 15% 3	346
March	1st to 10th	Day	33% 18% 28% 16% 4	420
	11th to 20th	Day	31% 24% 26% 14% 6%	420
	21st to end	Day	34% 18% 25% 15% 7% 2	462
April	1st to 10th	Day	35% 17% 25% 15% 6% 1	420
	11th to 20th	Day	35% 19% 24% 13% 6% 3	412
	21st to end	Day	33% 16% 31% 13% 5% 2	420
May	1st to 10th	Day	35% 17% 24% 14% 8% 1	423
	11th to 20th	Day	26% 17% 31% 18% 6% 3	447
	21st to end	Day	19% 20% 31% 22% 6% 2	485
June	1st to 10th	Day	34% 14% 29% 17% 6% 1	450
	11th to 20th	Day	22% 14% 30% 22% 10% 2	450
	21st to end	Day	22% 13% 35% 20% 8% 2	450
July	1st to 10th	Day	19% 11% 30% 27% 10% 3	445
	11th to 20th	Day	18% 9% 35% 26% 9% 3	444
	21st to end	Day	20% 10% 35% 25% 10% 1	488
August	1st to 10th	Day	17% 10% 29% 26% 15% 2	446
	11th to 20th	Day	17% 8% 31% 24% 16% 5%	439
	21st to end	Day	21% 13% 24% 24% 13% 6%	495
September	1st to 10th	Day	19% 11% 29% 22% 13% 6%	450
	11th to 20th	Day	20% 11% 24% 21% 18% 7%	450
	21st to end	Day	18% 13% 26% 23% 14% 5%	450
October	1st to 10th	Day	27% 18% 22% 17% 12% 6%	450
	11th to 20th	Day	29% 18% 24% 17% 11% 1	401
	21st to end	Day	39% 16% 23% 16% 6%	396
November	1st to 10th	Day	33% 16% 28% 18% 5%	365
	11th to 20th	Day	29% 21% 28% 15% 6% 2	370
	21st to end	Day	32% 20% 31% 14% 3	209
December	1st to 10th	Day	31% 22% 26% 13% 7% 1	180
	11th to 20th	Day	35% 24% 28% 11% 1 1	180
	21st to end	Day	36% 23% 25% 13% 3	198
January	1st to 10th	Night	28% 20% 30% 19% 3	760
	11th to 20th	Night	26% 21% 32% 18% 4	760
	21st to end	Night	21% 19% 33% 23% 5%	820
February	1st to 10th	Night	25% 20% 29% 22% 4	720
	11th to 20th	Night	22% 22% 31% 21% 3	703
	21st to end	Night	27% 16% 31% 23% 2	592
March	1st to 10th	Night	28% 17% 29% 23% 4	720
	11th to 20th	Night	29% 18% 26% 21% 6%	720
	21st to end	Night	28% 17% 25% 21% 7% 1	792
April	1st to 10th	Night	31% 14% 27% 22% 5%	720
	11th to 20th	Night	28% 15% 26% 23% 8%	685
	21st to end	Night	31% 13% 26% 22% 6%	540
May	1st to 10th	Night	27% 12% 28% 25% 7% 1	518
	11th to 20th	Night	24% 8% 30% 30% 7% 1	354
	21st to end	Night	19% 10% 29% 32% 10%	389
June	1st to 10th	Night	29% 7% 25% 29% 10% 1	360
	11th to 20th	Night	21% 6% 26% 34% 13% 1	360
	21st to end	Night	18% 9% 24% 38% 11%	360
July	1st to 10th	Night	17% 4 29% 35% 15% 1	350
	11th to 20th	Night	13% 3 25% 40% 18% 1	348
	21st to end	Night	15% 4 20% 42% 18% 1	394
August	1st to 10th	Night	17% 4 15% 41% 22% 1	358
	11th to 20th	Night	18% 4 20% 37% 19% 2	530
	21st to end	Night	17% 6% 20% 35% 20% 2	791
September	1st to 10th	Night	19% 6% 23% 37% 14% 1	720
	11th to 20th	Night	20% 8% 20% 29% 20% 2	720
	21st to end	Night	22% 9% 27% 24% 16% 2	720
October	1st to 10th	Night	29% 11% 20% 26% 13% 1	720
	11th to 20th	Night	28% 13% 25% 23% 10% 1	720
	21st to end	Night	32% 15% 26% 22% 4	792
November	1st to 10th	Night	28% 15% 30% 21% 6% 1	740
	11th to 20th	Night	27% 18% 28% 17% 9% 1	760
	21st to end	Night	29% 21% 27% 17% 6% 1	760
December	1st to 10th	Night	33% 20% 26% 17% 4	760
	11th to 20th	Night	30% 19% 28% 18% 5%	760
	21st to end	Night	33% 19% 26% 18% 3	836

Page generated at 2024-01-24 09:37:26. Version ac07

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