Champlain Belvédère
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Champlain Belvédère clear sky chart from 2005-11-06 to 2024-03-28.

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	18% 10% 4 7% 6% 3 5% 5% 5% 6% 31%	78597
	Night	18% 11% 4 7% 6% 3 4 4 5% 6% 31%	81391
Transparency	Day	36% 37% 8% 12% 6% 1	78302
	Night	38% 35% 8% 12% 6% 1	81220
Seeing	Day	25% 15% 31% 19% 8% 2	13587
	Night	24% 12% 28% 26% 10% 1	22861

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	16% 17% 7% 11% 8% 3 5% 4 4 4 21%	2517
	11th to 20th	Day	15% 13% 6% 13% 9% 4 5% 4 5% 5% 21%	2520
	21st to end	Day	13% 18% 7% 11% 8% 5% 6% 4 4 5% 18%	2896
February	1st to 10th	Day	14% 15% 6% 12% 8% 4 5% 5% 5% 5% 23%	1710
	11th to 20th	Day	13% 16% 7% 10% 6% 4 4 5% 5% 5% 28%	1663
	21st to end	Day	20% 11% 5% 9% 7% 3 4 5% 5% 5% 25%	1567
March	1st to 10th	Day	17% 12% 4 9% 7% 5% 5% 5% 5% 5% 28%	1901
	11th to 20th	Day	15% 13% 5% 8% 7% 4 5% 4 4 5% 30%	2090
	21st to end	Day	19% 9% 4 7% 6% 3 4 4 4 6% 35%	2370
April	1st to 10th	Day	23% 11% 4 6% 5% 4 3 4 4 6% 31%	2160
	11th to 20th	Day	22% 9% 3 6% 5% 2 4 4 4 5% 36%	2134
	21st to end	Day	23% 10% 4 7% 6% 3 4 4 4 4 31%	2292
May	1st to 10th	Day	21% 8% 3 6% 5% 3 5% 4 4 6% 34%	2520
	11th to 20th	Day	17% 7% 4 7% 6% 3 5% 4 4 6% 39%	2478
	21st to end	Day	17% 7% 3 5% 6% 3 6% 5% 5% 8% 36%	2725
June	1st to 10th	Day	22% 8% 4 6% 5% 4 5% 6% 5% 7% 29%	2520
	11th to 20th	Day	15% 5% 2 6% 6% 3 5% 6% 5% 8% 39%	2520
	21st to end	Day	19% 6% 3 5% 6% 4 6% 6% 8% 6% 32%	2520
July	1st to 10th	Day	12% 5% 2 6% 6% 3 6% 6% 7% 9% 39%	2520
	11th to 20th	Day	12% 6% 2 6% 6% 3 6% 6% 6% 8% 38%	2520
	21st to end	Day	13% 5% 2 5% 5% 3 5% 5% 7% 9% 39%	2744
August	1st to 10th	Day	12% 5% 3 5% 6% 4 6% 5% 6% 8% 39%	2470
	11th to 20th	Day	13% 5% 2 6% 6% 3 5% 5% 6% 9% 38%	2285
	21st to end	Day	14% 6% 3 5% 5% 3 4 5% 6% 8% 40%	2376
September	1st to 10th	Day	15% 5% 2 5% 5% 3 5% 4 6% 8% 42%	2160
	11th to 20th	Day	13% 6% 2 4 6% 3 4 4 6% 6% 45%	2160
	21st to end	Day	19% 6% 3 5% 5% 3 4 4 6% 7% 40%	1918
October	1st to 10th	Day	22% 8% 4 5% 5% 3 5% 4 5% 6% 35%	1800
	11th to 20th	Day	25% 10% 3 6% 5% 4 5% 4 5% 7% 26%	1800
	21st to end	Day	27% 9% 4 6% 6% 4 4 4 4 5% 26%	1836
November	1st to 10th	Day	16% 9% 3 7% 5% 4 5% 4 6% 8% 33%	1667
	11th to 20th	Day	20% 12% 4 6% 7% 4 5% 5% 5% 6% 25%	1520
	21st to end	Day	22% 14% 4 9% 8% 4 4 4 4 6% 20%	1520
December	1st to 10th	Day	22% 17% 7% 10% 6% 4 3 4 5% 6% 16%	1520
	11th to 20th	Day	21% 12% 5% 9% 8% 3 4 5% 4 5% 25%	1906
	21st to end	Day	27% 19% 5% 9% 5% 3 4 3 3 4 19%	2772
January	1st to 10th	Night	17% 18% 7% 10% 8% 3 4 4 4 5% 20%	4429
	11th to 20th	Night	13% 15% 6% 11% 8% 4 5% 5% 4 5% 24%	4440
	21st to end	Night	15% 19% 7% 10% 7% 5% 4 3 3 4 20%	4756
February	1st to 10th	Night	13% 13% 6% 11% 8% 4 5% 5% 5% 5% 24%	2470
	11th to 20th	Night	13% 13% 6% 10% 8% 3 5% 4 4 6% 28%	2403
	21st to end	Night	16% 13% 4 8% 7% 4 5% 4 5% 5% 29%	1885
March	1st to 10th	Night	17% 13% 5% 7% 7% 4 5% 4 4 5% 29%	2265
	11th to 20th	Night	16% 13% 5% 8% 6% 3 5% 4 4 5% 32%	2089
	21st to end	Night	17% 9% 4 6% 6% 3 3 3 4 5% 40%	2141
April	1st to 10th	Night	21% 9% 5% 7% 5% 3 3 4 4 5% 33%	1800
	11th to 20th	Night	18% 8% 4 6% 6% 3 4 4 5% 5% 36%	1775
	21st to end	Night	21% 10% 3 6% 5% 3 4 4 4 6% 33%	1681
May	1st to 10th	Night	21% 7% 2 5% 4 3 3 4 5% 7% 38%	1440
	11th to 20th	Night	18% 8% 3 6% 4 3 4 4 4 6% 40%	1415
	21st to end	Night	13% 5% 2 5% 5% 4 4 5% 5% 7% 43%	1550
June	1st to 10th	Night	17% 6% 2 6% 6% 3 5% 6% 6% 9% 34%	1440
	11th to 20th	Night	15% 5% 2 6% 5% 3 4 4 7% 7% 42%	1440
	21st to end	Night	17% 6% 2 5% 5% 4 5% 5% 5% 9% 36%	1440
July	1st to 10th	Night	11% 5% 2 5% 6% 3 5% 5% 5% 8% 47%	1440
	11th to 20th	Night	13% 6% 2 5% 5% 2 4 5% 6% 8% 44%	1440
	21st to end	Night	9% 5% 2 5% 6% 4 5% 6% 7% 8% 44%	1574
August	1st to 10th	Night	10% 6% 2 6% 6% 3 4 5% 6% 9% 43%	1466
	11th to 20th	Night	11% 5% 2 5% 5% 3 4 6% 7% 8% 44%	1598
	21st to end	Night	12% 5% 2 7% 5% 3 5% 5% 5% 7% 44%	1980
September	1st to 10th	Night	12% 6% 2 5% 5% 3 4 5% 5% 6% 46%	1800
	11th to 20th	Night	16% 5% 2 4 4 2 4 5% 5% 6% 48%	1800
	21st to end	Night	19% 5% 3 6% 5% 3 4 3 4 6% 43%	2036
October	1st to 10th	Night	20% 7% 2 5% 5% 3 4 4 5% 6% 38%	2160
	11th to 20th	Night	22% 8% 2 6% 7% 4 5% 5% 5% 6% 30%	2160
	21st to end	Night	25% 9% 3 7% 7% 4 5% 5% 4 6% 28%	2519
November	1st to 10th	Night	20% 10% 4 6% 5% 4 4 5% 5% 7% 33%	2407
	11th to 20th	Night	20% 11% 4 8% 6% 4 5% 4 5% 5% 28%	2660
	21st to end	Night	22% 12% 5% 9% 6% 3 6% 3 4 6% 24%	2660
December	1st to 10th	Night	22% 15% 6% 10% 7% 3 5% 5% 4 5% 18%	2660
	11th to 20th	Night	23% 13% 6% 9% 7% 2 3 3 3 4 27%	3288
	21st to end	Night	29% 18% 5% 9% 5% 3 4 3 3 4 18%	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	48% 31% 9% 7% 4 1	2518
	11th to 20th	Day	50% 26% 11% 9% 4	2520
	21st to end	Day	57% 26% 7% 6% 4	2896
February	1st to 10th	Day	40% 35% 8% 13% 3 1	1710
	11th to 20th	Day	39% 36% 9% 9% 5% 1	1672
	21st to end	Day	40% 36% 8% 10% 6% 1	1567
March	1st to 10th	Day	39% 36% 7% 12% 5%	1904
	11th to 20th	Day	39% 36% 9% 10% 5%	2090
	21st to end	Day	33% 36% 6% 13% 8% 3	2370
April	1st to 10th	Day	35% 36% 5% 14% 7% 2	2160
	11th to 20th	Day	34% 35% 6% 13% 11% 1	2134
	21st to end	Day	37% 37% 5% 9% 8% 4	2292
May	1st to 10th	Day	32% 38% 6% 12% 10% 3	2520
	11th to 20th	Day	31% 37% 6% 13% 11% 3	2482
	21st to end	Day	28% 38% 7% 14% 11% 2	2725
June	1st to 10th	Day	36% 39% 7% 10% 7%	2520
	11th to 20th	Day	27% 39% 8% 17% 8% 1	2520
	21st to end	Day	34% 40% 9% 10% 6%	2520
July	1st to 10th	Day	27% 41% 8% 18% 6%	2450
	11th to 20th	Day	27% 40% 10% 14% 8%	2445
	21st to end	Day	27% 41% 10% 16% 7%	2591
August	1st to 10th	Day	28% 40% 9% 18% 6%	2456
	11th to 20th	Day	25% 38% 12% 18% 6% 1	2285
	21st to end	Day	27% 39% 9% 16% 9% 1	2376
September	1st to 10th	Day	25% 39% 8% 20% 7%	2160
	11th to 20th	Day	27% 38% 9% 17% 8%	2160
	21st to end	Day	31% 39% 8% 18% 4	1918
October	1st to 10th	Day	34% 38% 8% 13% 6% 1	1800
	11th to 20th	Day	38% 39% 9% 9% 4	1800
	21st to end	Day	39% 38% 8% 9% 5%	1836
November	1st to 10th	Day	26% 43% 9% 17% 5%	1667
	11th to 20th	Day	36% 41% 8% 7% 7%	1520
	21st to end	Day	41% 42% 8% 6% 3	1520
December	1st to 10th	Day	45% 41% 7% 5% 1	1520
	11th to 20th	Day	43% 34% 11% 9% 3	1906
	21st to end	Day	57% 25% 5% 11% 2	2772
January	1st to 10th	Night	51% 28% 11% 8% 2	4429
	11th to 20th	Night	48% 28% 11% 10% 3	4440
	21st to end	Night	57% 24% 8% 7% 4	4756
February	1st to 10th	Night	41% 36% 7% 10% 5% 1	2470
	11th to 20th	Night	40% 36% 8% 11% 4 1	2405
	21st to end	Night	40% 35% 7% 13% 5% 1	1885
March	1st to 10th	Night	40% 35% 7% 12% 5% 1	2275
	11th to 20th	Night	39% 35% 8% 12% 5% 1	2090
	21st to end	Night	32% 35% 7% 13% 10% 3	2141
April	1st to 10th	Night	35% 37% 7% 10% 9% 2	1800
	11th to 20th	Night	34% 37% 6% 13% 10% 1	1775
	21st to end	Night	35% 36% 5% 11% 9% 3	1681
May	1st to 10th	Night	30% 37% 5% 12% 10% 5%	1440
	11th to 20th	Night	28% 37% 6% 15% 12% 2	1416
	21st to end	Night	25% 39% 8% 13% 14% 2	1551
June	1st to 10th	Night	31% 39% 10% 15% 5% 1	1440
	11th to 20th	Night	26% 39% 8% 16% 8% 2	1440
	21st to end	Night	30% 41% 8% 12% 8%	1440
July	1st to 10th	Night	25% 41% 9% 18% 7% 1	1400
	11th to 20th	Night	27% 39% 8% 18% 8%	1392
	21st to end	Night	25% 41% 9% 15% 10%	1486
August	1st to 10th	Night	28% 39% 10% 15% 8%	1456
	11th to 20th	Night	22% 37% 11% 20% 9%	1598
	21st to end	Night	26% 40% 10% 17% 8%	1980
September	1st to 10th	Night	26% 38% 7% 19% 10%	1800
	11th to 20th	Night	25% 38% 9% 21% 6% 1	1800
	21st to end	Night	30% 38% 8% 19% 6%	2036
October	1st to 10th	Night	32% 39% 8% 14% 8%	2160
	11th to 20th	Night	38% 38% 8% 11% 5%	2160
	21st to end	Night	37% 39% 9% 9% 5%	2519
November	1st to 10th	Night	30% 41% 9% 14% 5%	2407
	11th to 20th	Night	35% 41% 8% 9% 6% 1	2660
	21st to end	Night	39% 42% 7% 9% 2	2660
December	1st to 10th	Night	44% 41% 7% 6% 1	2660
	11th to 20th	Night	44% 33% 7% 12% 4 1	3288
	21st to end	Night	57% 26% 5% 10% 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	28% 17% 33% 18% 3	180
	11th to 20th	Day	31% 15% 38% 13% 2 1	180
	21st to end	Day	23% 18% 35% 19% 5%	232
February	1st to 10th	Day	34% 22% 32% 9% 3	270
	11th to 20th	Day	29% 28% 36% 6% 1	270
	21st to end	Day	35% 20% 30% 14% 1	379
March	1st to 10th	Day	29% 18% 32% 15% 5%	460
	11th to 20th	Day	28% 20% 33% 14% 4 1	460
	21st to end	Day	32% 18% 30% 15% 4 1	490
April	1st to 10th	Day	32% 22% 26% 13% 6%	420
	11th to 20th	Day	34% 17% 23% 15% 8% 1	412
	21st to end	Day	32% 19% 29% 13% 6% 1	420
May	1st to 10th	Day	28% 15% 31% 17% 7% 2	423
	11th to 20th	Day	20% 18% 33% 19% 8% 2	447
	21st to end	Day	22% 14% 34% 19% 10% 2	485
June	1st to 10th	Day	27% 11% 34% 19% 8% 1	450
	11th to 20th	Day	19% 13% 29% 24% 11% 4	450
	21st to end	Day	23% 10% 31% 23% 10% 2	450
July	1st to 10th	Day	13% 8% 31% 32% 13% 3	445
	11th to 20th	Day	14% 9% 35% 25% 14% 3	444
	21st to end	Day	14% 6% 35% 29% 12% 4	488
August	1st to 10th	Day	15% 8% 28% 30% 16% 4	446
	11th to 20th	Day	18% 3 26% 31% 15% 8%	439
	21st to end	Day	15% 12% 29% 25% 12% 6%	495
September	1st to 10th	Day	18% 10% 29% 23% 13% 7%	450
	11th to 20th	Day	16% 10% 26% 21% 17% 9%	450
	21st to end	Day	20% 13% 28% 21% 14% 4	450
October	1st to 10th	Day	26% 14% 23% 23% 10% 4	450
	11th to 20th	Day	29% 17% 30% 17% 7% 1	450
	21st to end	Day	34% 14% 27% 21% 4	423
November	1st to 10th	Day	26% 16% 31% 19% 7% 1	361
	11th to 20th	Day	29% 27% 28% 13% 3 1	180
	21st to end	Day	27% 22% 33% 13% 3 2	180
December	1st to 10th	Day	36% 12% 38% 12% 2	180
	11th to 20th	Day	28% 23% 37% 11% 2	180
	21st to end	Day	35% 19% 33% 10% 2 1	198
January	1st to 10th	Night	28% 16% 31% 21% 4	760
	11th to 20th	Night	29% 16% 28% 21% 6%	760
	21st to end	Night	20% 13% 35% 26% 5%	836
February	1st to 10th	Night	22% 19% 31% 24% 3	760
	11th to 20th	Night	22% 18% 37% 18% 4	743
	21st to end	Night	25% 17% 30% 23% 4	628
March	1st to 10th	Night	25% 16% 33% 22% 5%	760
	11th to 20th	Night	26% 17% 32% 19% 6%	760
	21st to end	Night	25% 16% 29% 22% 7%	821
April	1st to 10th	Night	28% 16% 27% 24% 4	720
	11th to 20th	Night	24% 18% 28% 21% 8% 1	711
	21st to end	Night	26% 14% 27% 23% 9%	601
May	1st to 10th	Night	24% 9% 25% 30% 10% 2	360
	11th to 20th	Night	22% 10% 28% 30% 11%	354
	21st to end	Night	17% 8% 37% 26% 12% 1	389
June	1st to 10th	Night	21% 6% 28% 35% 10%	360
	11th to 20th	Night	18% 8% 24% 34% 15% 2	360
	21st to end	Night	20% 6% 23% 35% 16% 1	360
July	1st to 10th	Night	12% 3 28% 37% 20%	350
	11th to 20th	Night	14% 2 20% 44% 18% 1	348
	21st to end	Night	9% 4 24% 44% 17% 2	394
August	1st to 10th	Night	12% 4 18% 41% 23% 1	392
	11th to 20th	Night	15% 3 16% 38% 25% 3	534
	21st to end	Night	15% 5% 23% 36% 19% 3	792
September	1st to 10th	Night	16% 5% 29% 29% 20% 2	720
	11th to 20th	Night	18% 7% 20% 31% 21% 3	720
	21st to end	Night	21% 8% 25% 26% 19% 2	720
October	1st to 10th	Night	24% 11% 24% 25% 15% 1	720
	11th to 20th	Night	28% 10% 28% 25% 8% 1	720
	21st to end	Night	30% 12% 28% 24% 5%	792
November	1st to 10th	Night	29% 11% 24% 27% 9% 1	740
	11th to 20th	Night	25% 17% 32% 16% 9% 1	760
	21st to end	Night	30% 17% 24% 22% 6%	760
December	1st to 10th	Night	31% 14% 31% 20% 4	760
	11th to 20th	Night	29% 17% 27% 21% 5% 1	760
	21st to end	Night	35% 14% 31% 16% 4	836

Page generated at 2024-03-24 23:37:01. Version ac07

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