Lac Chantier
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lac Chantier 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	18% 13% 5% 9% 7% 3 5% 4 5% 6% 25%	74754
	Night	16% 14% 6% 10% 7% 4 5% 4 4 5% 25%	74997
Transparency	Day	60% 3 9% 18% 9% 1	74459
	Night	61% 3 9% 18% 8% 1	74826
Seeing	Day	27% 16% 32% 17% 6% 2	13313
	Night	25% 15% 31% 21% 7% 1	22402

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	11% 22% 10% 15% 9% 3 5% 5% 4 3 12%	1517
	11th to 20th	Day	13% 18% 7% 13% 9% 4 6% 4 6% 5% 16%	1464
	21st to end	Day	10% 12% 7% 13% 9% 5% 7% 5% 6% 6% 20%	1584
February	1st to 10th	Day	8% 16% 8% 13% 10% 6% 6% 5% 5% 6% 15%	1565
	11th to 20th	Day	11% 17% 7% 13% 9% 4 6% 4 4 5% 18%	1611
	21st to end	Day	13% 19% 7% 11% 9% 5% 5% 4 5% 3 20%	1480
March	1st to 10th	Day	12% 17% 7% 10% 9% 4 5% 4 4 5% 22%	1797
	11th to 20th	Day	13% 15% 6% 10% 8% 4 5% 5% 4 5% 25%	1892
	21st to end	Day	15% 13% 6% 8% 8% 3 4 4 5% 6% 29%	2352
April	1st to 10th	Day	21% 17% 6% 9% 6% 3 3 4 4 5% 23%	2160
	11th to 20th	Day	21% 12% 6% 8% 5% 2 3 4 3 5% 31%	2134
	21st to end	Day	20% 14% 5% 7% 7% 3 4 3 4 5% 29%	2353
May	1st to 10th	Day	21% 12% 5% 6% 6% 3 4 4 4 7% 30%	2520
	11th to 20th	Day	21% 10% 3 5% 6% 3 4 4 5% 6% 32%	2478
	21st to end	Day	20% 10% 3 7% 6% 3 4 4 5% 6% 31%	2725
June	1st to 10th	Day	24% 10% 3 7% 7% 3 5% 4 5% 7% 25%	2520
	11th to 20th	Day	17% 8% 3 6% 6% 4 5% 5% 5% 9% 32%	2520
	21st to end	Day	23% 8% 3 8% 8% 4 5% 5% 6% 6% 25%	2520
July	1st to 10th	Day	18% 8% 4 7% 7% 4 5% 6% 5% 8% 29%	2520
	11th to 20th	Day	15% 8% 4 7% 7% 4 6% 6% 6% 8% 27%	2520
	21st to end	Day	14% 8% 4 7% 6% 4 5% 6% 7% 8% 32%	2744
August	1st to 10th	Day	18% 10% 4 8% 6% 4 5% 6% 7% 8% 24%	2506
	11th to 20th	Day	18% 8% 4 8% 5% 3 5% 6% 6% 8% 29%	2352
	21st to end	Day	18% 9% 4 7% 6% 4 5% 5% 5% 8% 28%	2376
September	1st to 10th	Day	20% 8% 3 6% 4 3 4 4 6% 7% 36%	2160
	11th to 20th	Day	18% 10% 4 6% 5% 3 4 4 5% 6% 35%	2111
	21st to end	Day	23% 8% 3 6% 5% 3 5% 4 4 6% 33%	1980
October	1st to 10th	Day	22% 15% 4 7% 5% 3 3 4 4 5% 26%	1814
	11th to 20th	Day	26% 17% 5% 8% 6% 2 4 5% 4 4 19%	1764
	21st to end	Day	26% 19% 5% 8% 5% 3 4 3 3 5% 18%	1782
November	1st to 10th	Day	16% 18% 7% 8% 5% 3 4 4 4 5% 26%	1671
	11th to 20th	Day	18% 17% 9% 14% 7% 3 3 3 4 4 17%	1544
	21st to end	Day	18% 21% 8% 14% 7% 3 4 3 4 4 14%	1520
December	1st to 10th	Day	20% 21% 8% 12% 9% 4 4 4 3 4 12%	1520
	11th to 20th	Day	18% 18% 8% 13% 10% 4 4 4 4 3 14%	1906
	21st to end	Day	18% 17% 9% 14% 10% 3 4 3 4 4 14%	2772
January	1st to 10th	Night	13% 21% 8% 14% 10% 4 5% 5% 4 4 10%	2649
	11th to 20th	Night	13% 18% 7% 13% 9% 4 6% 5% 5% 5% 15%	2569
	21st to end	Night	9% 12% 7% 11% 11% 6% 8% 5% 7% 6% 19%	2772
February	1st to 10th	Night	9% 13% 7% 12% 13% 6% 7% 6% 5% 5% 17%	2394
	11th to 20th	Night	9% 16% 7% 14% 10% 5% 6% 5% 4 5% 18%	2233
	21st to end	Night	10% 14% 7% 13% 9% 5% 6% 4 5% 5% 23%	1776
March	1st to 10th	Night	14% 15% 6% 9% 10% 5% 7% 5% 4 4 22%	2150
	11th to 20th	Night	16% 16% 7% 9% 7% 4 6% 5% 4 5% 23%	2065
	21st to end	Night	14% 13% 5% 9% 7% 4 4 3 4 5% 32%	2003
April	1st to 10th	Night	21% 14% 6% 9% 5% 3 4 4 4 6% 24%	1800
	11th to 20th	Night	17% 11% 4 7% 5% 3 4 5% 4 6% 34%	1775
	21st to end	Night	19% 12% 4 8% 5% 3 3 3 4 6% 33%	1620
May	1st to 10th	Night	21% 10% 4 7% 5% 2 4 4 5% 5% 34%	1440
	11th to 20th	Night	19% 11% 4 5% 5% 3 4 4 4 6% 35%	1415
	21st to end	Night	19% 9% 4 5% 6% 3 4 4 4 7% 36%	1550
June	1st to 10th	Night	20% 10% 3 5% 5% 4 5% 5% 7% 7% 30%	1440
	11th to 20th	Night	16% 8% 3 7% 6% 3 5% 4 5% 8% 35%	1440
	21st to end	Night	19% 6% 3 6% 6% 3 5% 5% 6% 7% 32%	1440
July	1st to 10th	Night	15% 6% 3 6% 7% 3 5% 5% 6% 8% 35%	1440
	11th to 20th	Night	12% 7% 4 6% 6% 4 7% 4 6% 9% 37%	1440
	21st to end	Night	12% 7% 3 6% 5% 3 4 5% 7% 10% 36%	1574
August	1st to 10th	Night	13% 7% 3 7% 5% 3 5% 5% 6% 10% 37%	1432
	11th to 20th	Night	13% 8% 3 8% 6% 3 4 5% 6% 8% 37%	1528
	21st to end	Night	18% 8% 2 6% 6% 3 5% 5% 5% 7% 36%	1980
September	1st to 10th	Night	18% 9% 3 5% 5% 4 5% 4 4 7% 38%	1800
	11th to 20th	Night	18% 9% 3 5% 4 2 4 3 4 6% 41%	1849
	21st to end	Night	18% 10% 3 7% 5% 3 4 3 4 5% 38%	1980
October	1st to 10th	Night	20% 11% 4 6% 6% 3 4 4 4 5% 34%	2142
	11th to 20th	Night	23% 18% 4 7% 6% 3 4 3 5% 5% 23%	2196
	21st to end	Night	25% 18% 6% 9% 6% 3 3 3 3 5% 19%	2574
November	1st to 10th	Night	16% 16% 7% 10% 6% 4 4 4 4 5% 24%	2407
	11th to 20th	Night	16% 15% 8% 12% 8% 4 5% 4 4 4 20%	2632
	21st to end	Night	20% 18% 9% 13% 9% 3 4 4 3 3 14%	2660
December	1st to 10th	Night	15% 20% 10% 14% 11% 5% 4 3 3 3 12%	2660
	11th to 20th	Night	19% 18% 6% 13% 9% 4 5% 3 4 3 16%	3288
	21st to end	Night	16% 20% 9% 14% 11% 4 4 3 3 3 14%	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	77% 2 4 11% 5%	1518
	11th to 20th	Day	70% 3 5% 14% 7% 2	1464
	21st to end	Day	63% 3 5% 15% 13% 2	1584
February	1st to 10th	Day	70% 3 5% 13% 8% 2	1565
	11th to 20th	Day	68% 3 6% 11% 11% 1	1620
	21st to end	Day	69% 2 5% 14% 8% 2	1480
March	1st to 10th	Day	66% 3 5% 15% 9% 3	1800
	11th to 20th	Day	62% 4 7% 13% 12% 2	1892
	21st to end	Day	57% 3 7% 17% 13% 3	2352
April	1st to 10th	Day	64% 3 8% 13% 10% 2	2160
	11th to 20th	Day	57% 3 7% 20% 11% 2	2134
	21st to end	Day	60% 2 8% 14% 13% 2	2353
May	1st to 10th	Day	56% 3 8% 19% 12% 2	2520
	11th to 20th	Day	53% 3 9% 20% 13% 2	2482
	21st to end	Day	53% 4 10% 20% 12% 1	2725
June	1st to 10th	Day	59% 4 7% 19% 9% 1	2520
	11th to 20th	Day	49% 3 12% 23% 11% 1	2520
	21st to end	Day	59% 3 12% 18% 8%	2520
July	1st to 10th	Day	52% 4 12% 24% 8%	2450
	11th to 20th	Day	52% 5% 14% 21% 7%	2445
	21st to end	Day	50% 4 15% 24% 6%	2591
August	1st to 10th	Day	57% 4 13% 21% 4	2492
	11th to 20th	Day	52% 4 15% 21% 7%	2352
	21st to end	Day	53% 4 11% 22% 9%	2376
September	1st to 10th	Day	48% 3 14% 24% 10% 1	2160
	11th to 20th	Day	50% 3 14% 23% 9%	2111
	21st to end	Day	52% 4 12% 24% 8%	1980
October	1st to 10th	Day	59% 3 11% 17% 9%	1814
	11th to 20th	Day	68% 4 10% 14% 3 1	1764
	21st to end	Day	70% 2 9% 14% 5% 1	1782
November	1st to 10th	Day	61% 3 9% 19% 7%	1671
	11th to 20th	Day	71% 3 7% 12% 6%	1544
	21st to end	Day	75% 3 7% 10% 5%	1520
December	1st to 10th	Day	77% 2 5% 10% 5%	1520
	11th to 20th	Day	74% 3 4 11% 7% 1	1906
	21st to end	Day	76% 2 4 13% 5%	2772
January	1st to 10th	Night	78% 3 5% 11% 3	2649
	11th to 20th	Night	70% 3 6% 12% 7% 2	2569
	21st to end	Night	63% 4 5% 13% 13% 2	2772
February	1st to 10th	Night	67% 4 5% 15% 8% 1	2394
	11th to 20th	Night	68% 3 5% 14% 8% 1	2235
	21st to end	Night	63% 3 5% 16% 11% 2	1776
March	1st to 10th	Night	66% 3 7% 14% 9% 2	2160
	11th to 20th	Night	63% 4 6% 16% 10% 2	2066
	21st to end	Night	54% 4 7% 20% 12% 3	2003
April	1st to 10th	Night	62% 3 7% 16% 11% 2	1800
	11th to 20th	Night	51% 4 9% 22% 12% 2	1775
	21st to end	Night	54% 2 8% 21% 13% 2	1620
May	1st to 10th	Night	53% 3 8% 20% 12% 4	1440
	11th to 20th	Night	52% 3 9% 20% 14% 2	1416
	21st to end	Night	49% 4 11% 23% 12% 1	1551
June	1st to 10th	Night	52% 4 11% 22% 10% 1	1440
	11th to 20th	Night	48% 4 13% 23% 10% 3	1440
	21st to end	Night	49% 4 14% 23% 9% 1	1440
July	1st to 10th	Night	46% 5% 16% 25% 8% 1	1400
	11th to 20th	Night	44% 4 16% 28% 8% 1	1392
	21st to end	Night	43% 5% 19% 26% 8%	1486
August	1st to 10th	Night	42% 5% 21% 26% 6%	1422
	11th to 20th	Night	43% 5% 20% 24% 7%	1528
	21st to end	Night	47% 4 15% 26% 8%	1980
September	1st to 10th	Night	46% 4 15% 24% 11%	1800
	11th to 20th	Night	46% 3 15% 28% 7% 1	1849
	21st to end	Night	49% 4 11% 28% 8%	1980
October	1st to 10th	Night	53% 3 10% 22% 11% 1	2142
	11th to 20th	Night	64% 3 11% 17% 5% 1	2196
	21st to end	Night	70% 3 7% 15% 5% 1	2574
November	1st to 10th	Night	64% 3 10% 17% 6%	2407
	11th to 20th	Night	67% 4 8% 15% 6% 1	2632
	21st to end	Night	75% 4 6% 12% 4	2660
December	1st to 10th	Night	80% 2 5% 9% 4	2660
	11th to 20th	Night	73% 3 3 13% 7% 1	3288
	21st to end	Night	76% 3 5% 10% 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	23% 23% 41% 11% 2	180
	11th to 20th	Day	24% 17% 37% 17% 3 2	166
	21st to end	Day	20% 22% 34% 20% 4	176
February	1st to 10th	Day	32% 32% 33% 2	216
	11th to 20th	Day	26% 33% 34% 6%	278
	21st to end	Day	28% 25% 32% 12% 1	346
March	1st to 10th	Day	25% 20% 37% 15% 3	420
	11th to 20th	Day	29% 23% 32% 12% 4	420
	21st to end	Day	30% 19% 32% 14% 4 2	462
April	1st to 10th	Day	33% 15% 34% 12% 5% 1	420
	11th to 20th	Day	36% 18% 24% 14% 7% 1	412
	21st to end	Day	34% 16% 34% 12% 4	420
May	1st to 10th	Day	27% 17% 32% 17% 5% 1	423
	11th to 20th	Day	30% 15% 32% 17% 5% 2	447
	21st to end	Day	29% 19% 30% 17% 4 1	485
June	1st to 10th	Day	31% 12% 39% 14% 4 1	450
	11th to 20th	Day	25% 15% 33% 17% 8% 1	450
	21st to end	Day	27% 12% 33% 20% 8% 1	450
July	1st to 10th	Day	20% 9% 38% 24% 8% 2	445
	11th to 20th	Day	20% 11% 35% 24% 8% 1	444
	21st to end	Day	18% 10% 33% 28% 9% 1	488
August	1st to 10th	Day	21% 8% 31% 27% 9% 2	446
	11th to 20th	Day	20% 7% 29% 28% 10% 5%	439
	21st to end	Day	24% 13% 28% 20% 8% 6%	495
September	1st to 10th	Day	25% 13% 29% 20% 10% 4	450
	11th to 20th	Day	24% 9% 33% 21% 11% 3	450
	21st to end	Day	25% 14% 27% 20% 10% 4	450
October	1st to 10th	Day	29% 14% 30% 16% 9% 2	450
	11th to 20th	Day	33% 17% 31% 13% 6% 1	432
	21st to end	Day	37% 13% 33% 15% 3	396
November	1st to 10th	Day	32% 21% 32% 11% 5%	365
	11th to 20th	Day	31% 23% 34% 8% 4	204
	21st to end	Day	33% 24% 32% 7% 4	180
December	1st to 10th	Day	33% 18% 30% 13% 6%	180
	11th to 20th	Day	34% 26% 29% 7% 3 1	180
	21st to end	Day	34% 19% 33% 9% 4 2	198
January	1st to 10th	Night	27% 19% 38% 12% 3 1	760
	11th to 20th	Night	23% 22% 33% 16% 5%	735
	21st to end	Night	15% 19% 40% 21% 5% 1	792
February	1st to 10th	Night	19% 23% 38% 16% 5%	720
	11th to 20th	Night	21% 22% 39% 14% 4 1	703
	21st to end	Night	23% 20% 35% 18% 3	592
March	1st to 10th	Night	25% 20% 32% 19% 4	720
	11th to 20th	Night	27% 21% 31% 15% 5% 1	720
	21st to end	Night	23% 15% 34% 22% 5% 1	792
April	1st to 10th	Night	31% 15% 27% 23% 4	720
	11th to 20th	Night	26% 17% 29% 20% 8%	711
	21st to end	Night	28% 16% 30% 19% 7%	540
May	1st to 10th	Night	26% 11% 29% 24% 9% 1	360
	11th to 20th	Night	27% 8% 31% 27% 6% 1	354
	21st to end	Night	22% 11% 38% 22% 6% 1	389
June	1st to 10th	Night	25% 8% 33% 26% 8%	360
	11th to 20th	Night	20% 9% 28% 29% 13% 1	360
	21st to end	Night	22% 6% 27% 31% 12% 3	360
July	1st to 10th	Night	16% 7% 33% 36% 8% 1	350
	11th to 20th	Night	15% 4 31% 33% 16% 1	348
	21st to end	Night	16% 6% 28% 37% 10% 2	394
August	1st to 10th	Night	15% 6% 25% 38% 16% 1	358
	11th to 20th	Night	15% 5% 27% 35% 18% 2	464
	21st to end	Night	22% 8% 27% 26% 15% 3	792
September	1st to 10th	Night	24% 7% 26% 32% 11% 1	720
	11th to 20th	Night	23% 8% 27% 27% 14% 1	720
	21st to end	Night	24% 11% 27% 22% 13% 2	720
October	1st to 10th	Night	25% 13% 29% 23% 8% 1	720
	11th to 20th	Night	34% 13% 30% 17% 6% 1	720
	21st to end	Night	34% 16% 28% 16% 5%	792
November	1st to 10th	Night	27% 19% 31% 16% 5% 2	740
	11th to 20th	Night	27% 19% 30% 15% 8% 1	760
	21st to end	Night	31% 21% 27% 17% 3 1	760
December	1st to 10th	Night	28% 19% 32% 16% 4 1	760
	11th to 20th	Night	28% 20% 34% 13% 5% 1	760
	21st to end	Night	33% 21% 28% 14% 4 1	836

Page generated at 2024-01-11 04:22:42. Version ac07

Copyright 2024 Attilla Danko