This page made possible by the sponsorship of:

RASC Toronto Centre

.

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 2026-03-18.

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	15% 11% 4 9% 5% 5% 4 4 5% 7% 33%	131531
	Night	15% 10% 4 9% 5% 5% 5% 4 5% 6% 33%	129964
Transparency	Day	48% 7% 13% 20% 11% 1	135117
	Night	48% 7% 13% 20% 12% 1	134464
Seeing	Day	20% 13% 29% 23% 11% 4	16067
	Night	19% 11% 30% 28% 11% 1	25541

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% 13% 5% 11% 6% 5% 5% 4 5% 5% 26%	4661
	11th to 20th	Day	9% 21% 9% 17% 8% 7% 4 3 4 4 14%	4921
	21st to end	Day	13% 16% 6% 16% 7% 5% 5% 3 4 5% 20%	5780
February	1st to 10th	Day	14% 17% 5% 12% 7% 6% 4 4 4 5% 23%	1890
	11th to 20th	Day	13% 16% 6% 13% 7% 5% 4 3 4 5% 24%	1843
	21st to end	Day	17% 15% 5% 11% 6% 4 4 3 4 5% 25%	1609
March	1st to 10th	Day	19% 12% 5% 9% 5% 4 4 3 4 5% 31%	5031
	11th to 20th	Day	12% 14% 4 9% 5% 5% 5% 3 6% 7% 29%	5057
	21st to end	Day	20% 12% 3 7% 4 3 3 3 5% 5% 35%	5465
April	1st to 10th	Day	18% 13% 4 8% 4 4 5% 3 5% 6% 29%	2395
	11th to 20th	Day	20% 11% 3 6% 3 4 4 3 5% 6% 35%	2410
	21st to end	Day	20% 10% 3 7% 6% 4 4 3 5% 5% 33%	2600
May	1st to 10th	Day	21% 10% 3 7% 5% 5% 4 4 5% 7% 31%	5995
	11th to 20th	Day	16% 10% 4 8% 5% 4 4 3 5% 7% 34%	6318
	21st to end	Day	19% 7% 2 6% 4 4 4 3 5% 8% 36%	6949
June	1st to 10th	Day	17% 7% 3 6% 5% 4 5% 4 6% 7% 36%	2800
	11th to 20th	Day	13% 6% 2 7% 6% 4 5% 5% 6% 9% 39%	2800
	21st to end	Day	15% 6% 3 6% 5% 5% 5% 4 6% 8% 37%	2800
July	1st to 10th	Day	10% 6% 3 6% 5% 5% 5% 4 7% 9% 40%	6360
	11th to 20th	Day	10% 5% 2 6% 4 4 5% 4 7% 9% 44%	6360
	21st to end	Day	6% 4 2 6% 5% 5% 5% 4 7% 10% 45%	6656
August	1st to 10th	Day	15% 8% 3 7% 4 5% 5% 4 5% 7% 38%	4234
	11th to 20th	Day	13% 6% 3 7% 4 4 5% 5% 7% 10% 37%	4174
	21st to end	Day	9% 6% 2 6% 4 5% 5% 5% 7% 9% 42%	4449
September	1st to 10th	Day	13% 6% 2 6% 4 5% 5% 4 6% 8% 42%	2400
	11th to 20th	Day	11% 5% 2 5% 4 4 5% 4 6% 8% 47%	2335
	21st to end	Day	14% 8% 2 7% 4 4 5% 4 6% 7% 39%	2126
October	1st to 10th	Day	18% 8% 2 6% 5% 4 4 4 5% 7% 36%	2000
	11th to 20th	Day	20% 10% 4 9% 5% 4 5% 3 4 6% 31%	2000
	21st to end	Day	23% 12% 4 9% 4 5% 4 3 5% 5% 26%	2200
November	1st to 10th	Day	16% 11% 3 8% 4 4 6% 4 5% 5% 34%	1759
	11th to 20th	Day	14% 14% 4 10% 5% 4 5% 4 7% 6% 26%	1680
	21st to end	Day	18% 18% 4 9% 5% 5% 4 3 5% 6% 23%	1680
December	1st to 10th	Day	17% 20% 6% 12% 6% 5% 5% 3 5% 5% 15%	2680
	11th to 20th	Day	17% 19% 6% 11% 4 4 4 3 4 5% 24%	3066
	21st to end	Day	23% 18% 5% 13% 5% 4 4 3 4 4 17%	4048
January	1st to 10th	Night	14% 14% 6% 12% 6% 5% 5% 3 6% 5% 24%	8234
	11th to 20th	Night	12% 17% 6% 14% 9% 6% 5% 4 5% 5% 17%	7960
	21st to end	Night	12% 13% 5% 12% 6% 5% 5% 4 5% 6% 26%	8401
February	1st to 10th	Night	13% 15% 4 11% 6% 6% 6% 4 5% 6% 25%	2730
	11th to 20th	Night	14% 12% 5% 12% 7% 4 5% 3 5% 5% 27%	2663
	21st to end	Night	14% 13% 5% 10% 5% 5% 5% 4 5% 6% 28%	2197
March	1st to 10th	Night	16% 11% 3 10% 5% 5% 4 3 4 5% 32%	5025
	11th to 20th	Night	11% 8% 3 8% 5% 6% 5% 4 6% 8% 35%	5057
	21st to end	Night	20% 8% 3 6% 4 4 4 3 4 6% 38%	5467
April	1st to 10th	Night	19% 11% 3 8% 5% 4 4 4 5% 6% 32%	2003
	11th to 20th	Night	17% 9% 3 6% 4 5% 4 4 5% 6% 37%	1956
	21st to end	Night	16% 9% 3 8% 5% 5% 5% 4 5% 6% 35%	1800
May	1st to 10th	Night	24% 8% 2 6% 4 4 4 3 5% 5% 34%	3943
	11th to 20th	Night	12% 8% 3 7% 4 5% 4 4 6% 7% 40%	3575
	21st to end	Night	18% 6% 2 6% 4 4 4 3 5% 8% 40%	3926
June	1st to 10th	Night	12% 6% 2 7% 5% 5% 6% 5% 6% 8% 39%	1600
	11th to 20th	Night	9% 6% 2 6% 6% 4 4 4 7% 8% 44%	1600
	21st to end	Night	11% 7% 2 6% 5% 4 4 4 7% 8% 42%	1600
July	1st to 10th	Night	8% 5% 2 6% 4 4 5% 4 7% 9% 45%	3600
	11th to 20th	Night	10% 5% 2 5% 4 4 4 4 6% 8% 49%	3600
	21st to end	Night	9% 5% 2 5% 3 3 4 3 6% 8% 53%	4192
August	1st to 10th	Night	9% 5% 2 6% 4 5% 4 3 5% 8% 49%	2915
	11th to 20th	Night	12% 5% 2 5% 3 3 4 3 5% 7% 50%	2875
	21st to end	Night	9% 5% 2 5% 4 4 4 3 6% 8% 49%	3416
September	1st to 10th	Night	11% 5% 2 6% 4 4 4 4 7% 7% 47%	2000
	11th to 20th	Night	10% 4 2 5% 4 3 3 4 5% 7% 55%	2061
	21st to end	Night	16% 7% 3 6% 4 4 3 3 4 6% 43%	2273
October	1st to 10th	Night	15% 6% 2 7% 5% 4 4 3 6% 7% 41%	2400
	11th to 20th	Night	20% 9% 3 6% 5% 4 4 3 5% 7% 32%	2400
	21st to end	Night	19% 10% 3 7% 4 4 5% 4 5% 6% 31%	2640
November	1st to 10th	Night	18% 9% 3 6% 5% 5% 4 4 6% 7% 35%	2757
	11th to 20th	Night	16% 12% 3 9% 6% 5% 6% 4 5% 7% 28%	2940
	21st to end	Night	19% 14% 3 9% 6% 5% 5% 5% 5% 6% 23%	2940
December	1st to 10th	Night	17% 15% 5% 11% 6% 5% 5% 4 6% 7% 19%	4720
	11th to 20th	Night	15% 18% 5% 10% 5% 6% 4 4 5% 6% 22%	5348
	21st to end	Night	24% 16% 5% 13% 5% 5% 5% 3 5% 4 16%	7150

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	56% 8% 13% 13% 9%	4662
	11th to 20th	Day	73% 5% 7% 9% 4	4953
	21st to end	Day	64% 6% 10% 11% 8%	5780
February	1st to 10th	Day	63% 5% 10% 16% 5% 1	1890
	11th to 20th	Day	61% 6% 9% 15% 8% 1	1852
	21st to end	Day	60% 6% 10% 17% 7% 1	1609
March	1st to 10th	Day	53% 5% 14% 14% 14%	5034
	11th to 20th	Day	51% 7% 17% 16% 7% 2	5057
	21st to end	Day	49% 6% 9% 19% 16% 2	5465
April	1st to 10th	Day	54% 5% 12% 17% 10% 2	2395
	11th to 20th	Day	49% 5% 9% 21% 14% 1	2410
	21st to end	Day	51% 6% 11% 17% 13% 2	2600
May	1st to 10th	Day	50% 8% 11% 16% 11% 4	6004
	11th to 20th	Day	48% 8% 11% 16% 16% 1	6322
	21st to end	Day	45% 6% 13% 22% 11% 3	6949
June	1st to 10th	Day	44% 8% 13% 21% 14% 1	2800
	11th to 20th	Day	39% 8% 14% 24% 14% 2	2800
	21st to end	Day	41% 8% 15% 22% 13% 1	2800
July	1st to 10th	Day	37% 7% 16% 25% 15% 1	6290
	11th to 20th	Day	32% 7% 14% 31% 14% 1	6285
	21st to end	Day	31% 9% 15% 32% 14%	6465
August	1st to 10th	Day	43% 7% 15% 22% 12% 1	4221
	11th to 20th	Day	39% 7% 16% 28% 9%	4213
	21st to end	Day	34% 7% 15% 34% 9% 1	4449
September	1st to 10th	Day	38% 7% 14% 29% 10% 1	2400
	11th to 20th	Day	33% 7% 15% 31% 14%	2335
	21st to end	Day	43% 8% 15% 24% 10%	2126
October	1st to 10th	Day	37% 7% 15% 27% 13% 1	3260
	11th to 20th	Day	40% 6% 17% 21% 15% 1	3240
	21st to end	Day	50% 7% 15% 20% 7% 1	3538
November	1st to 10th	Day	49% 8% 14% 19% 9% 1	1759
	11th to 20th	Day	54% 8% 15% 13% 8% 1	1680
	21st to end	Day	61% 7% 13% 15% 4	1680
December	1st to 10th	Day	67% 8% 14% 10% 2	2680
	11th to 20th	Day	61% 7% 10% 13% 8%	3066
	21st to end	Day	69% 8% 7% 9% 6% 1	4048
January	1st to 10th	Night	58% 7% 14% 14% 7%	8234
	11th to 20th	Night	65% 7% 11% 12% 5%	8003
	21st to end	Night	55% 7% 11% 13% 13% 1	8401
February	1st to 10th	Night	58% 7% 11% 18% 6% 1	2730
	11th to 20th	Night	56% 6% 11% 18% 8%	2665
	21st to end	Night	54% 5% 14% 19% 7% 1	2197
March	1st to 10th	Night	52% 6% 10% 18% 12% 3	5035
	11th to 20th	Night	43% 6% 19% 21% 10% 2	5058
	21st to end	Night	45% 5% 11% 19% 18% 2	5467
April	1st to 10th	Night	51% 6% 10% 19% 13% 1	2003
	11th to 20th	Night	47% 6% 10% 19% 17% 2	1956
	21st to end	Night	47% 6% 12% 18% 15% 2	1800
May	1st to 10th	Night	51% 6% 10% 13% 13% 5%	3950
	11th to 20th	Night	41% 9% 13% 21% 14% 2	3576
	21st to end	Night	41% 7% 13% 22% 15% 2	3927
June	1st to 10th	Night	39% 9% 11% 22% 16% 2	1600
	11th to 20th	Night	35% 8% 12% 22% 21% 2	1600
	21st to end	Night	39% 7% 13% 24% 16% 1	1600
July	1st to 10th	Night	32% 8% 16% 24% 19% 1	3560
	11th to 20th	Night	31% 7% 14% 31% 17% 1	3552
	21st to end	Night	28% 8% 12% 31% 21% 1	4068
August	1st to 10th	Night	34% 6% 14% 28% 16% 2	2904
	11th to 20th	Night	33% 6% 16% 31% 13% 1	2902
	21st to end	Night	32% 7% 13% 33% 15% 1	3416
September	1st to 10th	Night	33% 7% 15% 30% 13% 1	2000
	11th to 20th	Night	30% 6% 12% 34% 18% 1	2061
	21st to end	Night	41% 6% 12% 27% 12% 1	2273
October	1st to 10th	Night	32% 6% 12% 28% 23% 1	3920
	11th to 20th	Night	41% 6% 14% 28% 10%	3899
	21st to end	Night	40% 8% 15% 28% 9% 1	4252
November	1st to 10th	Night	46% 8% 13% 21% 12% 1	2757
	11th to 20th	Night	52% 7% 14% 16% 9% 1	2940
	21st to end	Night	57% 9% 16% 14% 4	2940
December	1st to 10th	Night	60% 8% 16% 12% 3	4720
	11th to 20th	Night	60% 9% 10% 13% 7%	5348
	21st to end	Night	69% 8% 10% 8% 5%	7150

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	25% 22% 30% 16% 5% 1	220
	11th to 20th	Day	26% 27% 29% 12% 5% 1	269
	21st to end	Day	29% 20% 31% 19% 2	363
February	1st to 10th	Day	25% 28% 31% 13% 3	330
	11th to 20th	Day	27% 24% 38% 10% 2	330
	21st to end	Day	30% 24% 34% 11% 1	325
March	1st to 10th	Day	24% 19% 35% 19% 4	540
	11th to 20th	Day	26% 21% 30% 18% 4	528
	21st to end	Day	31% 12% 32% 17% 6% 1	550
April	1st to 10th	Day	26% 16% 33% 19% 5% 1	500
	11th to 20th	Day	29% 16% 27% 16% 8% 3	492
	21st to end	Day	25% 15% 35% 16% 9% 1	500
May	1st to 10th	Day	22% 12% 30% 23% 9% 4	503
	11th to 20th	Day	18% 9% 29% 26% 14% 3	527
	21st to end	Day	16% 9% 25% 29% 16% 5%	573
June	1st to 10th	Day	18% 9% 33% 28% 12% 2	530
	11th to 20th	Day	14% 9% 28% 29% 16% 3	530
	21st to end	Day	19% 8% 28% 28% 13% 4	530
July	1st to 10th	Day	10% 5% 24% 34% 21% 5%	525
	11th to 20th	Day	14% 6% 24% 30% 19% 8%	524
	21st to end	Day	8% 4 32% 35% 14% 6%	576
August	1st to 10th	Day	12% 4 23% 34% 19% 8%	526
	11th to 20th	Day	13% 4 22% 31% 22% 9%	519
	21st to end	Day	13% 7% 27% 28% 17% 8%	583
September	1st to 10th	Day	13% 7% 25% 26% 18% 10%	530
	11th to 20th	Day	10% 5% 21% 29% 20% 15%	530
	21st to end	Day	15% 10% 28% 27% 14% 6%	530
October	1st to 10th	Day	18% 12% 27% 23% 15% 5%	530
	11th to 20th	Day	22% 16% 33% 21% 7% 2	530
	21st to end	Day	27% 17% 31% 20% 6%	583
November	1st to 10th	Day	24% 17% 29% 21% 8% 1	319
	11th to 20th	Day	23% 22% 35% 14% 5% 1	220
	21st to end	Day	30% 21% 33% 13% 4	220
December	1st to 10th	Day	26% 18% 36% 13% 6% 1	220
	11th to 20th	Day	28% 24% 30% 14% 3	220
	21st to end	Day	30% 19% 35% 14% 2	242
January	1st to 10th	Night	21% 18% 38% 17% 6%	840
	11th to 20th	Night	29% 14% 34% 20% 3	840
	21st to end	Night	20% 14% 35% 25% 6%	924
February	1st to 10th	Night	21% 16% 40% 21% 2	840
	11th to 20th	Night	21% 16% 38% 21% 3	823
	21st to end	Night	21% 16% 39% 20% 4	692
March	1st to 10th	Night	21% 15% 35% 25% 3	840
	11th to 20th	Night	22% 14% 35% 25% 4 1	829
	21st to end	Night	20% 12% 34% 25% 9%	880
April	1st to 10th	Night	24% 13% 33% 26% 5%	800
	11th to 20th	Night	19% 12% 33% 25% 9% 1	772
	21st to end	Night	21% 8% 32% 28% 11%	600
May	1st to 10th	Night	21% 6% 27% 31% 13% 3	555
	11th to 20th	Night	14% 8% 28% 36% 14%	394
	21st to end	Night	12% 6% 22% 39% 20% 1	433
June	1st to 10th	Night	13% 3 30% 39% 14% 1	400
	11th to 20th	Night	11% 6% 25% 41% 17% 1	400
	21st to end	Night	12% 6% 25% 40% 17% 1	400
July	1st to 10th	Night	7% 3 20% 47% 23% 1	390
	11th to 20th	Night	9% 5% 19% 41% 24% 1	388
	21st to end	Night	11% 2 21% 43% 21% 2	551
August	1st to 10th	Night	10% 2 16% 39% 30% 3	597
	11th to 20th	Night	10% 2 16% 38% 30% 4	594
	21st to end	Night	11% 4 23% 37% 24% 2	775
September	1st to 10th	Night	12% 5% 21% 35% 23% 4	800
	11th to 20th	Night	11% 4 19% 33% 27% 7%	800
	21st to end	Night	19% 7% 19% 30% 20% 4	800
October	1st to 10th	Night	18% 5% 28% 28% 19% 2	800
	11th to 20th	Night	22% 13% 29% 26% 9% 1	800
	21st to end	Night	26% 9% 32% 28% 5%	880
November	1st to 10th	Night	22% 12% 26% 29% 10% 1	820
	11th to 20th	Night	21% 17% 31% 24% 6% 2	840
	21st to end	Night	26% 14% 32% 22% 6%	840
December	1st to 10th	Night	27% 15% 34% 20% 3	840
	11th to 20th	Night	23% 14% 37% 21% 4 1	840
	21st to end	Night	29% 14% 36% 18% 3	924

Page generated at 2026-03-15 02:23:53. Version ac07

Copyright © 2026 Attilla Danko.