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 2025-04-11.

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%	113586
	Night	17% 11% 4 8% 5% 4 4 4 5% 6% 32%	114679
Transparency	Day	50% 6% 12% 21% 11% 1	117164
	Night	51% 6% 12% 20% 11% 1	119265
Seeing	Day	23% 17% 31% 19% 8% 3	14925
	Night	22% 13% 31% 24% 9% 1	24288

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	12% 14% 4 10% 5% 5% 5% 4 6% 6% 30%	3597
	11th to 20th	Day	11% 19% 8% 13% 6% 6% 5% 3 4 5% 21%	3570
	21st to end	Day	14% 17% 7% 16% 6% 5% 4 3 4 4 20%	4392
February	1st to 10th	Day	14% 17% 3 11% 6% 5% 5% 4 6% 5% 24%	1800
	11th to 20th	Day	13% 15% 5% 12% 7% 6% 5% 3 4 5% 27%	1753
	21st to end	Day	19% 14% 4 9% 7% 6% 4 4 4 4 24%	1605
March	1st to 10th	Day	19% 13% 4 10% 5% 4 3 3 4 6% 29%	4678
	11th to 20th	Day	11% 14% 3 9% 5% 5% 5% 4 5% 6% 32%	4980
	21st to end	Day	20% 11% 3 7% 4 3 3 2 3 5% 39%	5638
April	1st to 10th	Day	20% 14% 4 8% 4 3 4 3 3 6% 32%	2400
	11th to 20th	Day	21% 9% 3 6% 4 4 4 2 5% 6% 38%	2254
	21st to end	Day	21% 10% 3 9% 5% 4 4 3 4 6% 32%	2418
May	1st to 10th	Day	20% 8% 2 7% 5% 4 5% 4 5% 6% 33%	4361
	11th to 20th	Day	16% 9% 4 8% 5% 4 4 3 5% 8% 33%	4398
	21st to end	Day	13% 6% 3 6% 4 5% 4 4 5% 8% 42%	4837
June	1st to 10th	Day	19% 8% 3 7% 5% 5% 5% 4 7% 7% 30%	2660
	11th to 20th	Day	16% 5% 2 5% 5% 5% 5% 4 7% 8% 37%	2660
	21st to end	Day	18% 7% 3 7% 5% 5% 5% 4 5% 8% 34%	2660
July	1st to 10th	Day	12% 6% 2 7% 5% 6% 5% 4 7% 10% 36%	4440
	11th to 20th	Day	12% 5% 2 5% 5% 4 5% 4 7% 10% 41%	4440
	21st to end	Day	8% 6% 3 7% 5% 6% 5% 5% 7% 8% 41%	4814
August	1st to 10th	Day	16% 8% 2 7% 4 5% 5% 4 6% 8% 36%	4147
	11th to 20th	Day	17% 7% 3 6% 4 5% 5% 4 6% 9% 35%	4044
	21st to end	Day	13% 6% 2 6% 4 5% 4 4 7% 9% 40%	4195
September	1st to 10th	Day	13% 6% 3 6% 4 4 5% 4 5% 8% 42%	2280
	11th to 20th	Day	11% 6% 2 5% 3 3 4 3 4 8% 49%	2280
	21st to end	Day	19% 6% 3 5% 4 4 4 4 6% 8% 38%	1999
October	1st to 10th	Day	19% 9% 2 7% 4 4 4 3 5% 6% 35%	1900
	11th to 20th	Day	21% 9% 2 9% 4 5% 5% 4 5% 6% 30%	1900
	21st to end	Day	25% 12% 3 7% 5% 4 5% 3 4 5% 26%	2019
November	1st to 10th	Day	16% 9% 3 7% 5% 5% 5% 4 6% 6% 34%	1721
	11th to 20th	Day	17% 13% 4 8% 6% 5% 4 2 5% 6% 30%	1600
	21st to end	Day	22% 14% 5% 8% 5% 4 4 4 4 6% 23%	1600
December	1st to 10th	Day	21% 17% 5% 10% 6% 4 4 3 5% 6% 19%	2600
	11th to 20th	Day	17% 20% 6% 9% 5% 4 4 3 4 4 24%	2986
	21st to end	Day	24% 17% 4 9% 5% 4 3 2 3 5% 24%	3960
January	1st to 10th	Night	15% 14% 6% 12% 6% 5% 5% 3 5% 6% 23%	6349
	11th to 20th	Night	11% 16% 6% 14% 9% 6% 5% 4 5% 5% 18%	6315
	21st to end	Night	15% 16% 7% 14% 6% 4 4 4 5% 5% 22%	6563
February	1st to 10th	Night	14% 15% 5% 10% 7% 4 5% 4 6% 5% 25%	2600
	11th to 20th	Night	13% 14% 6% 9% 6% 6% 4 4 5% 5% 28%	2533
	21st to end	Night	15% 13% 4 8% 5% 5% 4 4 5% 7% 29%	2024
March	1st to 10th	Night	19% 12% 4 9% 5% 5% 4 3 4 4 30%	5146
	11th to 20th	Night	13% 12% 3 7% 5% 5% 5% 4 7% 8% 30%	4979
	21st to end	Night	20% 9% 3 8% 4 4 3 3 4 6% 36%	5294
April	1st to 10th	Night	20% 11% 4 7% 5% 3 4 4 4 6% 33%	2000
	11th to 20th	Night	19% 8% 2 8% 4 3 5% 3 5% 5% 38%	1882
	21st to end	Night	19% 8% 3 7% 4 5% 4 4 5% 7% 34%	1779
May	1st to 10th	Night	22% 9% 3 6% 4 4 3 4 5% 6% 34%	2578
	11th to 20th	Night	18% 8% 3 6% 4 4 4 4 4 7% 37%	2495
	21st to end	Night	13% 6% 2 6% 4 4 5% 4 4 7% 45%	2738
June	1st to 10th	Night	15% 7% 2 8% 5% 5% 5% 4 6% 8% 35%	1520
	11th to 20th	Night	12% 7% 2 6% 5% 4 4 3 5% 9% 43%	1520
	21st to end	Night	16% 6% 3 5% 6% 4 4 4 5% 8% 39%	1520
July	1st to 10th	Night	9% 5% 2 8% 5% 5% 5% 5% 6% 7% 41%	2520
	11th to 20th	Night	13% 6% 2 5% 4 3 4 3 5% 8% 47%	2520
	21st to end	Night	11% 5% 2 5% 4 4 4 4 6% 7% 48%	2739
August	1st to 10th	Night	12% 6% 2 5% 4 4 4 4 5% 7% 44%	2779
	11th to 20th	Night	14% 6% 2 5% 4 4 4 4 5% 6% 45%	2785
	21st to end	Night	10% 4 2 6% 4 4 5% 5% 6% 10% 43%	3428
September	1st to 10th	Night	12% 6% 2 5% 4 4 4 3 5% 8% 48%	1900
	11th to 20th	Night	12% 5% 2 5% 3 4 3 4 5% 6% 52%	1900
	21st to end	Night	16% 6% 2 6% 4 4 4 4 5% 6% 43%	2178
October	1st to 10th	Night	15% 8% 3 7% 4 4 5% 3 5% 7% 39%	2280
	11th to 20th	Night	21% 8% 3 9% 5% 5% 4 3 5% 6% 32%	2280
	21st to end	Night	22% 11% 3 7% 5% 5% 4 3 5% 6% 30%	2579
November	1st to 10th	Night	18% 10% 3 6% 4 5% 4 4 5% 6% 37%	2572
	11th to 20th	Night	18% 10% 4 7% 5% 5% 5% 4 5% 6% 32%	2800
	21st to end	Night	20% 14% 3 9% 4 5% 5% 4 6% 6% 26%	2800
December	1st to 10th	Night	20% 15% 4 10% 6% 5% 5% 4 6% 6% 19%	4580
	11th to 20th	Night	21% 16% 6% 9% 5% 4 3 3 4 5% 24%	5208
	21st to end	Night	27% 16% 4 10% 5% 4 4 3 4 4 21%	6996

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	53% 7% 11% 20% 8% 1	3598
	11th to 20th	Day	68% 4 10% 11% 7%	3600
	21st to end	Day	69% 3 8% 10% 9% 1	4392
February	1st to 10th	Day	61% 6% 10% 16% 6% 1	1800
	11th to 20th	Day	61% 4 9% 15% 10% 1	1762
	21st to end	Day	63% 6% 8% 11% 10% 1	1605
March	1st to 10th	Day	57% 4 11% 12% 15% 2	4681
	11th to 20th	Day	51% 5% 18% 15% 10% 2	4980
	21st to end	Day	49% 3 7% 21% 17% 3	5638
April	1st to 10th	Day	56% 3 8% 18% 13% 3	2400
	11th to 20th	Day	49% 4 8% 22% 16% 2	2254
	21st to end	Day	53% 6% 8% 16% 14% 3	2418
May	1st to 10th	Day	50% 6% 10% 22% 10% 2	4375
	11th to 20th	Day	48% 8% 13% 20% 10% 2	4402
	21st to end	Day	38% 8% 12% 24% 15% 2	4837
June	1st to 10th	Day	51% 9% 10% 17% 13% 1	2660
	11th to 20th	Day	42% 7% 12% 24% 13% 2	2660
	21st to end	Day	47% 7% 13% 19% 12% 1	2660
July	1st to 10th	Day	41% 7% 13% 25% 13% 1	4370
	11th to 20th	Day	35% 7% 15% 33% 10%	4365
	21st to end	Day	38% 8% 14% 30% 11%	4661
August	1st to 10th	Day	46% 6% 14% 22% 12%	4133
	11th to 20th	Day	43% 7% 14% 26% 9% 1	4083
	21st to end	Day	39% 6% 14% 31% 10% 1	4195
September	1st to 10th	Day	39% 9% 12% 27% 13% 1	2280
	11th to 20th	Day	33% 7% 13% 32% 15% 1	2280
	21st to end	Day	44% 8% 12% 26% 10%	1999
October	1st to 10th	Day	43% 6% 12% 30% 9% 1	3160
	11th to 20th	Day	46% 5% 15% 24% 9% 1	3140
	21st to end	Day	52% 5% 14% 21% 8%	3309
November	1st to 10th	Day	47% 8% 14% 21% 9% 1	1721
	11th to 20th	Day	55% 5% 12% 16% 11% 1	1600
	21st to end	Day	61% 8% 12% 12% 8%	1600
December	1st to 10th	Day	66% 6% 15% 9% 4	2600
	11th to 20th	Day	65% 5% 10% 13% 7%	2986
	21st to end	Day	64% 4 8% 16% 7%	3960
January	1st to 10th	Night	60% 7% 10% 16% 7%	6349
	11th to 20th	Night	66% 7% 11% 11% 5%	6360
	21st to end	Night	64% 5% 9% 9% 12% 1	6563
February	1st to 10th	Night	58% 7% 11% 18% 6% 1	2600
	11th to 20th	Night	57% 5% 11% 18% 8% 1	2535
	21st to end	Night	53% 6% 11% 20% 9% 1	2024
March	1st to 10th	Night	56% 4 7% 17% 11% 5%	5156
	11th to 20th	Night	48% 6% 18% 18% 8% 2	4980
	21st to end	Night	48% 3 10% 21% 15% 2	5294
April	1st to 10th	Night	52% 4 7% 20% 14% 2	2000
	11th to 20th	Night	48% 6% 9% 20% 16% 1	1882
	21st to end	Night	49% 6% 9% 17% 16% 3	1779
May	1st to 10th	Night	50% 6% 11% 18% 13% 3	2584
	11th to 20th	Night	44% 8% 12% 24% 9% 2	2496
	21st to end	Night	37% 7% 14% 21% 19% 2	2739
June	1st to 10th	Night	45% 7% 13% 21% 12% 1	1520
	11th to 20th	Night	37% 6% 14% 22% 19% 2	1520
	21st to end	Night	42% 8% 14% 22% 13% 1	1520
July	1st to 10th	Night	39% 6% 14% 22% 16% 2	2480
	11th to 20th	Night	36% 6% 12% 33% 12%	2472
	21st to end	Night	35% 7% 16% 29% 12% 1	2651
August	1st to 10th	Night	38% 7% 14% 27% 14% 1	2769
	11th to 20th	Night	38% 6% 14% 31% 10% 1	2812
	21st to end	Night	35% 8% 14% 32% 11% 1	3428
September	1st to 10th	Night	35% 7% 15% 28% 14% 1	1900
	11th to 20th	Night	31% 8% 14% 33% 14% 1	1900
	21st to end	Night	42% 7% 10% 28% 12% 1	2178
October	1st to 10th	Night	37% 5% 12% 27% 18%	3800
	11th to 20th	Night	44% 5% 15% 27% 9%	3779
	21st to end	Night	49% 5% 13% 24% 9%	4239
November	1st to 10th	Night	47% 5% 15% 23% 10% 1	2572
	11th to 20th	Night	52% 6% 11% 20% 10% 2	2800
	21st to end	Night	57% 8% 13% 17% 5%	2800
December	1st to 10th	Night	64% 6% 13% 13% 3	4580
	11th to 20th	Night	63% 5% 10% 13% 8%	5208
	21st to end	Night	67% 5% 8% 11% 9%	6996

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% 22% 34% 18% 3 1	200
	11th to 20th	Day	27% 21% 33% 15% 4 1	200
	21st to end	Day	25% 22% 37% 13% 3	313
February	1st to 10th	Day	31% 28% 29% 10% 1	300
	11th to 20th	Day	30% 28% 36% 6%	300
	21st to end	Day	36% 19% 33% 11% 1	369
March	1st to 10th	Day	27% 20% 34% 15% 4	500
	11th to 20th	Day	28% 22% 31% 15% 4	500
	21st to end	Day	33% 20% 27% 13% 5% 1	550
April	1st to 10th	Day	28% 23% 31% 12% 4	500
	11th to 20th	Day	33% 23% 19% 16% 7% 3	452
	21st to end	Day	29% 21% 32% 10% 6% 2	460
May	1st to 10th	Day	25% 16% 30% 18% 7% 3	463
	11th to 20th	Day	18% 18% 34% 21% 7% 3	487
	21st to end	Day	17% 17% 34% 20% 9% 3	529
June	1st to 10th	Day	24% 12% 34% 22% 7% 2	490
	11th to 20th	Day	15% 17% 33% 22% 12% 2	490
	21st to end	Day	22% 14% 33% 19% 10% 2	490
July	1st to 10th	Day	12% 10% 30% 32% 14% 3	485
	11th to 20th	Day	15% 10% 31% 28% 14% 4	484
	21st to end	Day	13% 8% 36% 28% 12% 3	532
August	1st to 10th	Day	14% 9% 28% 30% 14% 5%	486
	11th to 20th	Day	13% 7% 28% 30% 17% 5%	479
	21st to end	Day	14% 11% 32% 24% 11% 8%	539
September	1st to 10th	Day	16% 12% 31% 23% 12% 7%	490
	11th to 20th	Day	13% 9% 24% 23% 18% 13%	490
	21st to end	Day	19% 12% 28% 23% 12% 6%	490
October	1st to 10th	Day	24% 18% 25% 18% 11% 4	490
	11th to 20th	Day	25% 20% 30% 18% 6% 1	490
	21st to end	Day	30% 21% 27% 19% 3	502
November	1st to 10th	Day	30% 15% 28% 19% 7% 1	355
	11th to 20th	Day	28% 21% 36% 10% 5% 1	200
	21st to end	Day	28% 21% 33% 14% 4 1	200
December	1st to 10th	Day	31% 18% 35% 13% 3 1	200
	11th to 20th	Day	36% 23% 28% 10% 3 1	200
	21st to end	Day	33% 20% 32% 11% 3 1	220
January	1st to 10th	Night	28% 18% 33% 19% 3	800
	11th to 20th	Night	26% 17% 32% 19% 5%	800
	21st to end	Night	20% 16% 35% 24% 3 1	880
February	1st to 10th	Night	22% 20% 37% 19% 2	800
	11th to 20th	Night	23% 19% 38% 17% 3	783
	21st to end	Night	24% 19% 34% 20% 2	660
March	1st to 10th	Night	23% 18% 36% 21% 3	800
	11th to 20th	Night	24% 20% 29% 22% 3 1	800
	21st to end	Night	23% 16% 34% 19% 7% 1	880
April	1st to 10th	Night	26% 17% 33% 20% 4	800
	11th to 20th	Night	23% 22% 28% 19% 7% 1	754
	21st to end	Night	24% 12% 30% 23% 10%	639
May	1st to 10th	Night	24% 10% 28% 27% 10% 2	418
	11th to 20th	Night	16% 10% 32% 34% 8%	374
	21st to end	Night	12% 9% 38% 29% 12% 1	411
June	1st to 10th	Night	16% 7% 36% 29% 11%	380
	11th to 20th	Night	14% 7% 34% 33% 11% 1	380
	21st to end	Night	18% 5% 27% 38% 12%	380
July	1st to 10th	Night	7% 8% 29% 39% 16% 1	370
	11th to 20th	Night	13% 4 27% 37% 19% 1	368
	21st to end	Night	12% 5% 27% 43% 13%	416
August	1st to 10th	Night	12% 5% 26% 34% 22% 1	534
	11th to 20th	Night	11% 5% 22% 35% 25% 3	564
	21st to end	Night	13% 6% 29% 31% 18% 2	801
September	1st to 10th	Night	14% 5% 32% 31% 16% 2	760
	11th to 20th	Night	13% 6% 23% 27% 26% 4	760
	21st to end	Night	20% 9% 22% 29% 18% 3	760
October	1st to 10th	Night	20% 13% 26% 24% 16% 1	760
	11th to 20th	Night	26% 13% 29% 24% 8% 1	760
	21st to end	Night	29% 13% 30% 23% 5%	836
November	1st to 10th	Night	25% 13% 29% 25% 8%	780
	11th to 20th	Night	24% 15% 34% 19% 7% 1	800
	21st to end	Night	31% 15% 29% 19% 6%	800
December	1st to 10th	Night	31% 17% 31% 18% 3	800
	11th to 20th	Night	27% 18% 36% 16% 2 1	800
	21st to end	Night	35% 14% 30% 17% 3	880

Page generated at 2025-04-08 09:17:24. Version ac07

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