Long Sault Conservation Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Long Sault Conservation Area clear sky chart from 2005-11-06 to 2024-01-16.

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	16% 9% 4 7% 6% 3 5% 5% 5% 7% 33%	74696
	Night	16% 10% 4 7% 6% 3 5% 4 5% 7% 34%	75089
Transparency	Day	48% 7% 13% 20% 11% 1	74407
	Night	49% 7% 13% 19% 11% 1	74912
Seeing	Day	19% 12% 29% 24% 12% 4	13319
	Night	19% 9% 30% 28% 12% 1	22786

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% 15% 5% 8% 8% 3 5% 4 4 7% 26%	1517
	11th to 20th	Day	17% 18% 6% 9% 7% 4 5% 4 4 5% 21%	1557
	21st to end	Day	13% 14% 7% 11% 9% 3 5% 4 4 5% 24%	1782
February	1st to 10th	Day	15% 16% 6% 11% 8% 4 5% 5% 4 5% 20%	1620
	11th to 20th	Day	13% 15% 7% 11% 6% 4 4 4 4 6% 26%	1573
	21st to end	Day	18% 14% 6% 9% 7% 3 4 3 3 5% 26%	1376
March	1st to 10th	Day	15% 11% 4 10% 8% 4 5% 4 5% 6% 30%	1967
	11th to 20th	Day	14% 14% 5% 6% 6% 3 4 3 5% 5% 34%	1980
	21st to end	Day	20% 10% 4 6% 5% 3 4 4 4 4 35%	2178
April	1st to 10th	Day	19% 12% 5% 7% 5% 3 5% 3 5% 6% 29%	2155
	11th to 20th	Day	20% 9% 3 5% 4 3 5% 4 4 6% 36%	2166
	21st to end	Day	21% 9% 3 6% 7% 3 4 4 5% 5% 34%	2340
May	1st to 10th	Day	18% 8% 4 7% 7% 3 4 5% 5% 7% 33%	2377
	11th to 20th	Day	16% 6% 3 6% 5% 3 4 4 5% 8% 40%	2478
	21st to end	Day	13% 5% 3 5% 5% 3 5% 5% 5% 8% 42%	2725
June	1st to 10th	Day	17% 6% 3 5% 5% 3 5% 6% 6% 8% 37%	2520
	11th to 20th	Day	13% 5% 2 6% 6% 3 5% 5% 6% 9% 40%	2520
	21st to end	Day	14% 6% 3 5% 5% 4 6% 5% 6% 8% 38%	2520
July	1st to 10th	Day	9% 5% 2 4 5% 3 5% 5% 8% 9% 44%	2520
	11th to 20th	Day	12% 5% 2 5% 6% 3 6% 6% 7% 10% 38%	2520
	21st to end	Day	9% 5% 3 6% 6% 4 7% 7% 7% 10% 36%	2639
August	1st to 10th	Day	9% 5% 2 7% 6% 5% 6% 6% 7% 8% 40%	2327
	11th to 20th	Day	10% 5% 3 5% 6% 3 5% 7% 7% 10% 40%	2303
	21st to end	Day	12% 7% 3 5% 5% 3 5% 5% 7% 9% 39%	2453
September	1st to 10th	Day	14% 5% 2 6% 5% 4 6% 5% 5% 8% 41%	2160
	11th to 20th	Day	12% 5% 2 5% 5% 3 5% 5% 6% 8% 45%	2102
	21st to end	Day	13% 7% 2 6% 5% 3 4 5% 6% 7% 40%	1914
October	1st to 10th	Day	20% 8% 3 6% 6% 3 5% 5% 6% 7% 32%	1800
	11th to 20th	Day	21% 9% 5% 8% 7% 3 4 4 4 6% 29%	1800
	21st to end	Day	25% 12% 4 8% 5% 3 4 4 5% 5% 24%	1980
November	1st to 10th	Day	16% 10% 4 6% 5% 3 6% 5% 6% 6% 34%	1589
	11th to 20th	Day	15% 12% 5% 8% 6% 3 5% 5% 7% 7% 26%	1520
	21st to end	Day	19% 16% 4 7% 6% 4 4 4 5% 6% 24%	1520
December	1st to 10th	Day	17% 15% 7% 10% 7% 3 6% 5% 5% 6% 19%	1520
	11th to 20th	Day	17% 14% 5% 9% 5% 3 4 4 5% 6% 26%	1906
	21st to end	Day	27% 17% 5% 10% 6% 3 5% 4 4 4 15%	2772
January	1st to 10th	Night	17% 13% 6% 8% 8% 4 4 4 5% 5% 25%	2649
	11th to 20th	Night	18% 16% 6% 9% 7% 3 6% 4 5% 5% 20%	2510
	21st to end	Night	12% 13% 5% 9% 7% 5% 5% 5% 5% 5% 28%	2574
February	1st to 10th	Night	14% 15% 5% 10% 7% 4 7% 5% 5% 6% 22%	2340
	11th to 20th	Night	15% 11% 6% 9% 8% 3 5% 4 5% 5% 28%	2273
	21st to end	Night	15% 12% 5% 9% 6% 4 4 5% 5% 6% 29%	1880
March	1st to 10th	Night	14% 9% 5% 8% 7% 4 4 4 4 6% 35%	1977
	11th to 20th	Night	17% 10% 5% 7% 5% 3 5% 4 4 5% 35%	1979
	21st to end	Night	16% 7% 4 6% 5% 3 5% 4 4 6% 39%	2178
April	1st to 10th	Night	20% 10% 3 6% 5% 3 4 4 4 6% 33%	1803
	11th to 20th	Night	16% 8% 3 5% 5% 4 5% 5% 4 6% 38%	1758
	21st to end	Night	16% 10% 3 7% 5% 3 5% 5% 5% 6% 35%	1620
May	1st to 10th	Night	18% 7% 2 5% 5% 4 5% 4 5% 7% 38%	1580
	11th to 20th	Night	13% 5% 2 6% 4 3 4 5% 5% 7% 45%	1415
	21st to end	Night	10% 4 2 4 4 3 3 4 5% 10% 49%	1550
June	1st to 10th	Night	12% 5% 3 5% 5% 3 7% 6% 6% 9% 39%	1440
	11th to 20th	Night	10% 5% 2 5% 7% 3 5% 5% 6% 8% 45%	1440
	21st to end	Night	11% 6% 3 6% 5% 3 5% 5% 6% 8% 43%	1440
July	1st to 10th	Night	6% 4 3 4 4 3 5% 5% 6% 8% 52%	1440
	11th to 20th	Night	10% 4 2 5% 5% 3 4 4 6% 9% 48%	1440
	21st to end	Night	8% 4 2 4 5% 3 4 5% 7% 8% 49%	1675
August	1st to 10th	Night	8% 5% 2 5% 6% 3 5% 4 6% 9% 49%	1611
	11th to 20th	Night	7% 5% 2 5% 4 3 5% 5% 6% 8% 50%	1598
	21st to end	Night	9% 6% 3 5% 5% 3 5% 4 5% 8% 47%	1885
September	1st to 10th	Night	11% 5% 2 5% 5% 3 4 5% 7% 7% 45%	1800
	11th to 20th	Night	12% 4 2 4 4 3 3 4 5% 7% 52%	1854
	21st to end	Night	15% 7% 3 6% 5% 3 3 4 4 7% 45%	2045
October	1st to 10th	Night	16% 6% 3 6% 6% 4 5% 4 6% 7% 38%	2160
	11th to 20th	Night	21% 8% 4 6% 6% 3 5% 4 5% 7% 31%	2160
	21st to end	Night	21% 10% 4 6% 5% 3 6% 5% 5% 6% 29%	2376
November	1st to 10th	Night	19% 8% 3 5% 5% 3 5% 4 5% 8% 35%	2487
	11th to 20th	Night	18% 10% 4 7% 6% 3 6% 5% 5% 8% 28%	2660
	21st to end	Night	19% 12% 4 8% 6% 4 6% 5% 5% 7% 24%	2660
December	1st to 10th	Night	19% 14% 6% 9% 7% 3 5% 4 5% 6% 22%	2660
	11th to 20th	Night	16% 17% 4 8% 7% 4 5% 5% 5% 6% 23%	3288
	21st to end	Night	28% 16% 5% 8% 6% 3 5% 4 4 5% 15%	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	57% 9% 14% 14% 7%	1518
	11th to 20th	Day	66% 7% 9% 11% 7% 1	1557
	21st to end	Day	62% 6% 10% 12% 8% 1	1782
February	1st to 10th	Day	66% 6% 10% 14% 4 1	1620
	11th to 20th	Day	59% 6% 9% 15% 9% 1	1582
	21st to end	Day	60% 5% 9% 17% 7% 1	1376
March	1st to 10th	Day	53% 5% 17% 14% 10% 1	1970
	11th to 20th	Day	52% 6% 10% 18% 13% 2	1980
	21st to end	Day	51% 5% 9% 17% 16% 3	2178
April	1st to 10th	Day	54% 5% 12% 18% 10% 2	2155
	11th to 20th	Day	48% 6% 10% 21% 15% 1	2166
	21st to end	Day	51% 6% 11% 18% 13% 2	2340
May	1st to 10th	Day	49% 7% 10% 18% 13% 3	2377
	11th to 20th	Day	42% 6% 12% 24% 14% 1	2482
	21st to end	Day	38% 8% 15% 24% 12% 2	2725
June	1st to 10th	Day	43% 8% 13% 21% 14% 1	2520
	11th to 20th	Day	39% 7% 14% 24% 14% 2	2520
	21st to end	Day	40% 8% 16% 22% 13% 1	2520
July	1st to 10th	Day	32% 8% 14% 26% 19% 2	2450
	11th to 20th	Day	37% 8% 16% 28% 10% 1	2445
	21st to end	Day	38% 12% 14% 24% 11% 1	2491
August	1st to 10th	Day	37% 11% 17% 23% 12% 1	2314
	11th to 20th	Day	36% 9% 17% 26% 11%	2303
	21st to end	Day	38% 7% 16% 26% 12% 1	2453
September	1st to 10th	Day	39% 8% 13% 28% 10% 1	2160
	11th to 20th	Day	34% 7% 16% 29% 14% 1	2102
	21st to end	Day	42% 8% 16% 25% 9%	1914
October	1st to 10th	Day	48% 8% 14% 18% 11% 1	1800
	11th to 20th	Day	54% 7% 15% 18% 6% 1	1800
	21st to end	Day	60% 7% 13% 14% 6% 1	1980
November	1st to 10th	Day	49% 8% 15% 18% 9% 1	1589
	11th to 20th	Day	54% 8% 16% 13% 8% 1	1520
	21st to end	Day	59% 8% 13% 16% 4	1520
December	1st to 10th	Day	63% 8% 14% 12% 3	1520
	11th to 20th	Day	57% 10% 13% 14% 7%	1906
	21st to end	Day	71% 9% 8% 9% 3	2772
January	1st to 10th	Night	60% 6% 11% 16% 6%	2649
	11th to 20th	Night	65% 8% 9% 11% 6% 1	2510
	21st to end	Night	57% 7% 10% 16% 9% 1	2574
February	1st to 10th	Night	61% 7% 11% 16% 5% 1	2340
	11th to 20th	Night	56% 7% 11% 17% 9%	2275
	21st to end	Night	54% 5% 13% 19% 7% 1	1880
March	1st to 10th	Night	50% 6% 13% 19% 10% 2	1987
	11th to 20th	Night	51% 4 11% 21% 11% 2	1980
	21st to end	Night	45% 6% 11% 20% 16% 3	2178
April	1st to 10th	Night	50% 6% 10% 19% 14% 1	1803
	11th to 20th	Night	46% 6% 11% 18% 17% 2	1758
	21st to end	Night	48% 6% 13% 17% 15% 2	1620
May	1st to 10th	Night	45% 7% 10% 19% 16% 3	1580
	11th to 20th	Night	37% 6% 11% 24% 18% 4	1416
	21st to end	Night	31% 7% 16% 24% 19% 4	1551
June	1st to 10th	Night	39% 9% 12% 22% 16% 2	1440
	11th to 20th	Night	35% 8% 12% 21% 22% 2	1440
	21st to end	Night	38% 7% 14% 24% 16% 1	1440
July	1st to 10th	Night	26% 9% 13% 26% 23% 3	1400
	11th to 20th	Night	32% 6% 13% 30% 18% 1	1392
	21st to end	Night	30% 8% 14% 31% 16% 2	1582
August	1st to 10th	Night	31% 8% 19% 28% 14% 1	1600
	11th to 20th	Night	30% 8% 17% 31% 14% 1	1598
	21st to end	Night	34% 8% 13% 28% 15% 1	1885
September	1st to 10th	Night	35% 8% 15% 27% 14% 2	1800
	11th to 20th	Night	31% 6% 12% 33% 17% 1	1854
	21st to end	Night	40% 6% 12% 29% 12%	2045
October	1st to 10th	Night	44% 7% 14% 19% 14% 1	2160
	11th to 20th	Night	51% 8% 13% 21% 7%	2160
	21st to end	Night	54% 8% 12% 15% 10% 1	2376
November	1st to 10th	Night	45% 7% 13% 22% 12% 1	2487
	11th to 20th	Night	52% 7% 15% 16% 9% 1	2660
	21st to end	Night	56% 9% 17% 14% 4	2660
December	1st to 10th	Night	61% 8% 14% 13% 4	2660
	11th to 20th	Night	59% 9% 13% 14% 4	3288
	21st to end	Night	69% 8% 11% 9% 3	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	24% 19% 30% 18% 7% 1	180
	11th to 20th	Day	26% 25% 29% 13% 5% 1	205
	21st to end	Day	25% 19% 33% 20% 2	264
February	1st to 10th	Day	25% 31% 31% 10% 3	240
	11th to 20th	Day	23% 23% 41% 11% 2	240
	21st to end	Day	31% 26% 31% 12% 1	242
March	1st to 10th	Day	22% 17% 37% 19% 5%	420
	11th to 20th	Day	22% 20% 33% 20% 4	420
	21st to end	Day	31% 11% 32% 19% 6% 1	462
April	1st to 10th	Day	23% 15% 34% 20% 6% 1	420
	11th to 20th	Day	27% 14% 27% 18% 10% 4	412
	21st to end	Day	25% 13% 34% 17% 9% 1	420
May	1st to 10th	Day	23% 10% 29% 23% 10% 5%	423
	11th to 20th	Day	19% 7% 30% 27% 13% 4	447
	21st to end	Day	14% 7% 25% 31% 17% 6%	485
June	1st to 10th	Day	16% 7% 32% 30% 12% 2	450
	11th to 20th	Day	15% 8% 25% 30% 18% 3	450
	21st to end	Day	17% 5% 28% 31% 14% 4	450
July	1st to 10th	Day	10% 3 21% 36% 24% 6%	445
	11th to 20th	Day	15% 3 21% 31% 21% 9%	444
	21st to end	Day	8% 3 30% 37% 15% 6%	488
August	1st to 10th	Day	10% 4 22% 35% 20% 9%	446
	11th to 20th	Day	11% 3 21% 31% 23% 10%	439
	21st to end	Day	13% 6% 24% 29% 19% 9%	495
September	1st to 10th	Day	12% 6% 26% 26% 20% 10%	450
	11th to 20th	Day	12% 5% 23% 28% 18% 14%	450
	21st to end	Day	13% 10% 27% 27% 16% 7%	450
October	1st to 10th	Day	20% 11% 26% 22% 16% 5%	450
	11th to 20th	Day	22% 16% 32% 23% 6% 2	450
	21st to end	Day	28% 16% 28% 21% 6%	495
November	1st to 10th	Day	21% 16% 28% 24% 10% 1	269
	11th to 20th	Day	22% 21% 36% 15% 4 1	180
	21st to end	Day	27% 19% 36% 14% 4	180
December	1st to 10th	Day	21% 19% 38% 15% 6% 1	180
	11th to 20th	Day	24% 25% 30% 17% 3 1	180
	21st to end	Day	28% 20% 36% 15% 1	198
January	1st to 10th	Night	22% 16% 38% 18% 6%	760
	11th to 20th	Night	28% 12% 34% 21% 4 1	741
	21st to end	Night	19% 12% 36% 26% 7%	792
February	1st to 10th	Night	21% 15% 41% 20% 2	720
	11th to 20th	Night	20% 14% 40% 21% 4	703
	21st to end	Night	21% 14% 41% 21% 4	592
March	1st to 10th	Night	20% 14% 36% 26% 4 1	720
	11th to 20th	Night	21% 13% 35% 26% 4 1	720
	21st to end	Night	19% 10% 34% 27% 10%	792
April	1st to 10th	Night	23% 12% 33% 27% 5%	720
	11th to 20th	Night	18% 12% 33% 26% 10% 1	694
	21st to end	Night	21% 8% 32% 28% 11%	540
May	1st to 10th	Night	20% 5% 27% 31% 14% 3	500
	11th to 20th	Night	14% 7% 29% 36% 14%	354
	21st to end	Night	11% 4 22% 40% 21% 1	389
June	1st to 10th	Night	13% 3 29% 39% 15% 1	360
	11th to 20th	Night	11% 5% 25% 41% 18% 1	360
	21st to end	Night	12% 4 24% 41% 18% 1	360
July	1st to 10th	Night	7% 3 19% 48% 23% 1	350
	11th to 20th	Night	10% 4 19% 42% 24% 1	348
	21st to end	Night	10% 2 20% 45% 22% 2	495
August	1st to 10th	Night	10% 2 15% 40% 30% 3	537
	11th to 20th	Night	9% 1 16% 39% 31% 5%	534
	21st to end	Night	11% 4 22% 36% 25% 2	697
September	1st to 10th	Night	13% 4 21% 35% 22% 5%	720
	11th to 20th	Night	13% 4 19% 33% 25% 6%	720
	21st to end	Night	18% 8% 19% 29% 22% 5%	720
October	1st to 10th	Night	20% 5% 29% 27% 18% 2	720
	11th to 20th	Night	23% 12% 30% 26% 9% 1	720
	21st to end	Night	27% 8% 31% 28% 5% 1	792
November	1st to 10th	Night	22% 11% 25% 30% 11% 1	740
	11th to 20th	Night	21% 15% 30% 24% 7% 2	760
	21st to end	Night	24% 13% 33% 24% 7%	760
December	1st to 10th	Night	27% 15% 34% 20% 3	760
	11th to 20th	Night	23% 12% 38% 23% 4 1	760
	21st to end	Night	30% 13% 36% 19% 3	836

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