Lennox and Addington Dark Sky Viewing Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lennox and Addington Dark Sky Viewing Area clear sky chart from 2005-11-06 to 2026-08-15.

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% 10% 3 8% 5% 5% 4 4 5% 7% 33%	144452
	Night	16% 11% 4 8% 5% 4 4 4 5% 6% 33%	137404
Transparency	Day	49% 5% 12% 21% 11% 1	147983
	Night	51% 5% 12% 20% 11% 1	141961
Seeing	Day	23% 17% 31% 19% 8% 3	16696
	Night	22% 13% 31% 24% 9% 1	25832

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	14% 13% 4 11% 6% 5% 5% 4 5% 6% 26%	4661
	11th to 20th	Day	11% 21% 9% 14% 6% 6% 5% 3 3 4 18%	4650
	21st to end	Day	11% 15% 8% 16% 8% 8% 5% 3 4 4 19%	5678
February	1st to 10th	Day	14% 17% 3 11% 6% 5% 5% 4 6% 5% 24%	1890
	11th to 20th	Day	13% 14% 5% 12% 7% 5% 5% 3 4 5% 27%	1843
	21st to end	Day	19% 15% 5% 9% 7% 6% 4 4 4 4 23%	1683
March	1st to 10th	Day	19% 13% 4 10% 5% 4 3 3 4 6% 29%	4782
	11th to 20th	Day	11% 14% 3 9% 5% 5% 5% 4 5% 6% 32%	5090
	21st to end	Day	20% 11% 3 7% 4 3 3 2 3 5% 38%	5762
April	1st to 10th	Day	20% 14% 4 8% 4 4 3 2 3 6% 31%	2520
	11th to 20th	Day	21% 10% 3 6% 4 4 3 2 4 5% 36%	2494
	21st to end	Day	21% 10% 3 9% 5% 4 4 3 4 6% 32%	2672
May	1st to 10th	Day	21% 9% 3 7% 5% 5% 5% 4 5% 6% 30%	8117
	11th to 20th	Day	16% 8% 3 8% 5% 5% 4 3 5% 7% 35%	8221
	21st to end	Day	19% 7% 3 6% 4 4 4 4 5% 7% 36%	9060
June	1st to 10th	Day	19% 8% 3 7% 5% 5% 5% 4 6% 7% 31%	2940
	11th to 20th	Day	16% 6% 2 5% 5% 5% 5% 4 7% 8% 37%	2940
	21st to end	Day	17% 7% 3 7% 5% 5% 5% 4 6% 8% 34%	2940
July	1st to 10th	Day	11% 6% 3 7% 5% 5% 5% 4 6% 10% 38%	8280
	11th to 20th	Day	9% 4 2 5% 4 4 5% 4 6% 10% 47%	8280
	21st to end	Day	11% 5% 2 6% 4 5% 5% 4 7% 9% 41%	8993
August	1st to 10th	Day	16% 8% 2 7% 4 4 5% 4 6% 8% 37%	4410
	11th to 20th	Day	17% 7% 3 6% 4 4 5% 4 6% 8% 36%	4226
	21st to end	Day	13% 6% 2 6% 4 5% 4 4 7% 9% 40%	4328
September	1st to 10th	Day	12% 6% 3 6% 4 4 5% 4 5% 8% 43%	2400
	11th to 20th	Day	11% 6% 3 5% 3 3 4 3 4 8% 50%	2400
	21st to end	Day	19% 6% 3 5% 4 4 4 4 6% 8% 38%	2104
October	1st to 10th	Day	19% 9% 2 7% 4 4 4 3 5% 6% 37%	2000
	11th to 20th	Day	20% 9% 2 9% 4 5% 5% 4 6% 7% 30%	2000
	21st to end	Day	25% 11% 3 7% 5% 4 5% 3 4 5% 27%	2125
November	1st to 10th	Day	16% 9% 3 7% 5% 5% 4 4 6% 6% 34%	1809
	11th to 20th	Day	17% 13% 4 8% 6% 5% 4 2 5% 6% 30%	1680
	21st to end	Day	21% 15% 5% 8% 5% 4 4 4 4 6% 23%	1680
December	1st to 10th	Day	20% 17% 5% 10% 5% 4 4 3 5% 6% 19%	2680
	11th to 20th	Day	17% 20% 6% 9% 5% 4 4 3 4 4 24%	3066
	21st to end	Day	23% 17% 4 10% 5% 4 3 2 3 5% 24%	4048
January	1st to 10th	Night	14% 14% 7% 13% 6% 5% 5% 3 4 6% 22%	8234
	11th to 20th	Night	12% 19% 6% 14% 8% 6% 5% 3 5% 5% 17%	8235
	21st to end	Night	13% 14% 6% 12% 6% 5% 5% 4 5% 5% 25%	8488
February	1st to 10th	Night	13% 15% 5% 10% 7% 4 5% 4 6% 5% 26%	2730
	11th to 20th	Night	13% 14% 6% 9% 6% 6% 4 4 6% 5% 28%	2663
	21st to end	Night	15% 14% 4 8% 5% 5% 4 4 5% 7% 28%	2122
March	1st to 10th	Night	19% 12% 4 9% 5% 5% 4 3 4 4 30%	5262
	11th to 20th	Night	13% 12% 3 7% 5% 5% 5% 4 7% 8% 30%	5089
	21st to end	Night	20% 9% 3 8% 4 4 3 3 4 6% 36%	5411
April	1st to 10th	Night	20% 11% 4 7% 4 3 4 4 4 6% 33%	2100
	11th to 20th	Night	19% 9% 2 8% 4 3 5% 3 5% 5% 37%	2075
	21st to end	Night	19% 8% 3 7% 4 5% 4 4 5% 7% 34%	1966
May	1st to 10th	Night	23% 9% 3 7% 4 4 4 4 5% 7% 30%	4780
	11th to 20th	Night	15% 8% 3 6% 4 4 4 4 5% 7% 41%	4639
	21st to end	Night	18% 6% 2 6% 4 4 5% 4 5% 8% 38%	5114
June	1st to 10th	Night	15% 7% 2 8% 5% 5% 5% 3 5% 8% 36%	1680
	11th to 20th	Night	12% 7% 2 6% 5% 4 4 4 5% 9% 43%	1680
	21st to end	Night	15% 6% 3 6% 6% 4 4 4 5% 8% 39%	1680
July	1st to 10th	Night	9% 6% 2 7% 5% 4 5% 4 6% 9% 41%	4680
	11th to 20th	Night	9% 5% 2 5% 3 4 4 3 5% 8% 51%	4680
	21st to end	Night	11% 5% 2 5% 4 4 4 4 5% 7% 48%	5084
August	1st to 10th	Night	12% 6% 2 6% 4 4 5% 4 6% 7% 44%	2955
	11th to 20th	Night	14% 6% 2 5% 4 4 4 4 5% 6% 46%	2911
	21st to end	Night	10% 5% 2 6% 4 4 5% 5% 7% 10% 43%	3536
September	1st to 10th	Night	12% 6% 2 5% 4 3 4 3 5% 8% 48%	2000
	11th to 20th	Night	11% 4 2 5% 3 4 3 4 5% 6% 52%	2000
	21st to end	Night	17% 6% 2 6% 4 4 4 3 5% 6% 42%	2293
October	1st to 10th	Night	15% 7% 3 7% 4 4 5% 3 5% 7% 41%	2400
	11th to 20th	Night	20% 8% 3 9% 5% 5% 4 3 5% 6% 32%	2400
	21st to end	Night	22% 11% 3 7% 5% 5% 4 3 5% 6% 31%	2715
November	1st to 10th	Night	18% 10% 3 6% 4 5% 4 4 5% 6% 36%	2704
	11th to 20th	Night	17% 10% 4 7% 5% 5% 5% 4 5% 7% 32%	2940
	21st to end	Night	19% 14% 3 9% 5% 5% 5% 4 5% 6% 25%	2940
December	1st to 10th	Night	20% 15% 4 10% 6% 5% 5% 4 6% 6% 19%	4720
	11th to 20th	Night	21% 16% 5% 9% 5% 4 3 3 4 5% 25%	5348
	21st to end	Night	27% 16% 4 10% 5% 4 4 3 4 4 21%	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	57% 6% 11% 18% 7% 1	4662
	11th to 20th	Day	72% 3 8% 9% 7%	4680
	21st to end	Day	69% 3 8% 10% 9% 1	5678
February	1st to 10th	Day	61% 5% 10% 17% 6% 1	1890
	11th to 20th	Day	60% 4 9% 15% 10% 1	1852
	21st to end	Day	63% 6% 8% 12% 10% 1	1683
March	1st to 10th	Day	57% 4 11% 12% 14% 2	4785
	11th to 20th	Day	52% 5% 17% 15% 10% 2	5090
	21st to end	Day	50% 3 7% 21% 17% 3	5762
April	1st to 10th	Day	56% 3 8% 17% 13% 2	2520
	11th to 20th	Day	50% 4 8% 21% 15% 2	2494
	21st to end	Day	53% 5% 8% 17% 14% 3	2672
May	1st to 10th	Day	54% 5% 9% 19% 11% 2	8128
	11th to 20th	Day	48% 6% 11% 20% 14% 1	8225
	21st to end	Day	46% 6% 10% 24% 12% 1	9061
June	1st to 10th	Day	50% 8% 9% 17% 14% 1	2940
	11th to 20th	Day	42% 7% 12% 24% 13% 2	2940
	21st to end	Day	46% 7% 14% 20% 12% 1	2940
July	1st to 10th	Day	40% 6% 15% 26% 12%	8210
	11th to 20th	Day	32% 5% 13% 33% 16% 1	8205
	21st to end	Day	37% 7% 15% 33% 9%	8795
August	1st to 10th	Day	45% 6% 15% 22% 12% 1	4396
	11th to 20th	Day	43% 7% 14% 26% 9% 1	4265
	21st to end	Day	39% 6% 14% 31% 10% 1	4328
September	1st to 10th	Day	39% 8% 13% 28% 12% 1	2400
	11th to 20th	Day	33% 6% 13% 32% 15% 1	2400
	21st to end	Day	44% 8% 12% 26% 10%	2104
October	1st to 10th	Day	42% 5% 12% 31% 10%	3260
	11th to 20th	Day	46% 5% 15% 24% 10% 1	3240
	21st to end	Day	52% 5% 14% 21% 8%	3415
November	1st to 10th	Day	48% 8% 13% 21% 9% 1	1809
	11th to 20th	Day	55% 5% 13% 16% 11% 1	1680
	21st to end	Day	61% 8% 12% 12% 8%	1680
December	1st to 10th	Day	66% 6% 15% 9% 4	2680
	11th to 20th	Day	65% 5% 11% 13% 7%	3066
	21st to end	Day	65% 4 8% 16% 7%	4048
January	1st to 10th	Night	63% 6% 10% 14% 7%	8234
	11th to 20th	Night	69% 5% 9% 10% 7%	8280
	21st to end	Night	60% 5% 9% 12% 13% 1	8488
February	1st to 10th	Night	58% 7% 11% 18% 6% 1	2730
	11th to 20th	Night	57% 5% 11% 19% 8% 1	2665
	21st to end	Night	54% 6% 11% 19% 9% 1	2122
March	1st to 10th	Night	56% 4 7% 17% 11% 5%	5272
	11th to 20th	Night	49% 6% 18% 17% 8% 2	5090
	21st to end	Night	48% 3 10% 21% 15% 2	5411
April	1st to 10th	Night	52% 4 8% 20% 13% 2	2100
	11th to 20th	Night	48% 6% 9% 20% 16% 1	2075
	21st to end	Night	49% 6% 9% 18% 15% 3	1966
May	1st to 10th	Night	53% 5% 10% 19% 11% 3	4786
	11th to 20th	Night	42% 6% 13% 23% 14% 1	4640
	21st to end	Night	44% 5% 12% 21% 16% 1	5115
June	1st to 10th	Night	45% 7% 12% 21% 15% 1	1680
	11th to 20th	Night	38% 6% 14% 22% 18% 2	1680
	21st to end	Night	42% 7% 14% 23% 12% 1	1680
July	1st to 10th	Night	38% 6% 18% 23% 14% 1	4640
	11th to 20th	Night	31% 5% 13% 34% 16% 1	4632
	21st to end	Night	36% 6% 12% 32% 14% 1	4967
August	1st to 10th	Night	38% 7% 14% 26% 14% 1	2945
	11th to 20th	Night	37% 6% 13% 31% 11% 1	2938
	21st to end	Night	35% 8% 14% 32% 11% 1	3536
September	1st to 10th	Night	34% 7% 15% 29% 14% 1	2000
	11th to 20th	Night	30% 7% 13% 34% 15% 1	2000
	21st to end	Night	42% 7% 10% 27% 12% 1	2293
October	1st to 10th	Night	37% 5% 12% 27% 19%	3920
	11th to 20th	Night	44% 5% 15% 26% 9%	3899
	21st to end	Night	48% 5% 13% 24% 9%	4375
November	1st to 10th	Night	47% 5% 15% 22% 10% 1	2704
	11th to 20th	Night	52% 6% 12% 20% 10% 2	2940
	21st to end	Night	58% 8% 12% 17% 5%	2940
December	1st to 10th	Night	64% 6% 13% 13% 3	4720
	11th to 20th	Night	63% 5% 10% 13% 8%	5348
	21st to end	Night	67% 4 8% 11% 9%	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	24% 21% 35% 17% 2	220
	11th to 20th	Day	30% 21% 32% 14% 4	220
	21st to end	Day	25% 21% 37% 13% 3	344
February	1st to 10th	Day	30% 26% 30% 11% 2	330
	11th to 20th	Day	28% 27% 37% 7%	330
	21st to end	Day	36% 19% 33% 11% 1	399
March	1st to 10th	Day	27% 21% 34% 14% 4	540
	11th to 20th	Day	31% 22% 29% 14% 4	540
	21st to end	Day	34% 21% 27% 13% 5% 1	594
April	1st to 10th	Day	30% 24% 30% 11% 4	540
	11th to 20th	Day	35% 22% 20% 15% 6% 2	532
	21st to end	Day	29% 21% 32% 11% 6% 1	540
May	1st to 10th	Day	26% 18% 30% 16% 6% 3	543
	11th to 20th	Day	18% 18% 36% 19% 7% 2	567
	21st to end	Day	20% 17% 33% 18% 8% 3	617
June	1st to 10th	Day	24% 12% 34% 21% 7% 2	570
	11th to 20th	Day	16% 16% 35% 20% 11% 1	570
	21st to end	Day	20% 15% 34% 19% 10% 2	570
July	1st to 10th	Day	12% 10% 32% 32% 12% 2	565
	11th to 20th	Day	14% 10% 31% 27% 14% 4	564
	21st to end	Day	13% 9% 36% 27% 11% 3	620
August	1st to 10th	Day	14% 9% 29% 30% 14% 5%	566
	11th to 20th	Day	14% 7% 28% 30% 16% 5%	535
	21st to end	Day	15% 10% 33% 23% 11% 7%	583
September	1st to 10th	Day	15% 12% 29% 24% 12% 7%	530
	11th to 20th	Day	12% 8% 24% 24% 19% 13%	530
	21st to end	Day	19% 12% 29% 23% 12% 5%	530
October	1st to 10th	Day	23% 17% 25% 19% 12% 5%	530
	11th to 20th	Day	24% 21% 31% 18% 5% 1	530
	21st to end	Day	30% 20% 27% 19% 3	542
November	1st to 10th	Day	31% 16% 28% 18% 7% 1	383
	11th to 20th	Day	27% 21% 36% 10% 5% 1	220
	21st to end	Day	30% 20% 34% 12% 3 1	220
December	1st to 10th	Day	30% 17% 37% 13% 3	220
	11th to 20th	Day	37% 22% 27% 10% 2 1	220
	21st to end	Day	35% 19% 33% 10% 2 1	242
January	1st to 10th	Night	27% 18% 33% 19% 3	840
	11th to 20th	Night	27% 17% 32% 19% 5%	840
	21st to end	Night	21% 16% 35% 24% 3 1	924
February	1st to 10th	Night	22% 19% 37% 20% 2	840
	11th to 20th	Night	23% 18% 38% 17% 4	823
	21st to end	Night	24% 19% 34% 20% 2	692
March	1st to 10th	Night	23% 18% 35% 21% 3	840
	11th to 20th	Night	25% 21% 28% 22% 3 1	840
	21st to end	Night	23% 16% 35% 18% 6% 1	924
April	1st to 10th	Night	26% 17% 33% 20% 4	840
	11th to 20th	Night	24% 22% 27% 20% 6% 1	831
	21st to end	Night	24% 12% 31% 24% 10%	706
May	1st to 10th	Night	24% 10% 29% 27% 9% 2	462
	11th to 20th	Night	16% 10% 33% 34% 7%	414
	21st to end	Night	14% 8% 38% 29% 11% 1	455
June	1st to 10th	Night	16% 8% 35% 31% 10%	420
	11th to 20th	Night	15% 8% 35% 31% 10% 1	420
	21st to end	Night	17% 5% 27% 39% 11%	420
July	1st to 10th	Night	7% 8% 31% 39% 15%	410
	11th to 20th	Night	12% 5% 27% 38% 18% 1	408
	21st to end	Night	12% 5% 27% 42% 13% 1	460
August	1st to 10th	Night	12% 4 25% 34% 23% 1	590
	11th to 20th	Night	10% 5% 22% 35% 25% 2	606
	21st to end	Night	13% 6% 29% 32% 18% 2	843
September	1st to 10th	Night	14% 5% 32% 31% 16% 2	800
	11th to 20th	Night	13% 6% 23% 29% 26% 4	800
	21st to end	Night	20% 9% 22% 29% 17% 3	800
October	1st to 10th	Night	20% 13% 26% 24% 17% 1	800
	11th to 20th	Night	25% 13% 29% 24% 8% 1	800
	21st to end	Night	28% 13% 30% 24% 5%	880
November	1st to 10th	Night	25% 13% 29% 25% 8%	820
	11th to 20th	Night	24% 15% 34% 19% 7% 1	840
	21st to end	Night	31% 15% 29% 19% 6%	840
December	1st to 10th	Night	30% 17% 30% 19% 3	840
	11th to 20th	Night	27% 18% 36% 16% 2 1	840
	21st to end	Night	35% 15% 30% 17% 3	924

Page generated at 2026-08-12 03:37:13. Version ac07

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