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 2024-02-20.

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	17% 10% 4 7% 6% 3 5% 5% 5% 7% 33%	78261
	Night	17% 10% 4 7% 6% 3 4 5% 5% 6% 33%	80926
Transparency	Day	51% 7% 11% 19% 11% 1	77966
	Night	51% 7% 12% 19% 10% 1	80755
Seeing	Day	23% 16% 31% 19% 8% 3	13457
	Night	22% 13% 31% 24% 9% 1	22835

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	15% 16% 5% 9% 6% 4 4 5% 4 4 28%	2517
	11th to 20th	Day	13% 17% 8% 11% 7% 4 6% 4 4 5% 22%	2520
	21st to end	Day	19% 18% 8% 12% 7% 4 4 3 3 3 19%	3064
February	1st to 10th	Day	14% 16% 4 9% 8% 4 5% 5% 5% 6% 24%	1710
	11th to 20th	Day	13% 14% 6% 11% 8% 4 6% 4 3 4 28%	1654
	21st to end	Day	20% 13% 6% 8% 7% 4 6% 4 4 4 24%	1440
March	1st to 10th	Day	15% 11% 5% 10% 8% 4 4 5% 4 6% 29%	1873
	11th to 20th	Day	14% 15% 5% 9% 7% 3 5% 4 4 5% 31%	1980
	21st to end	Day	21% 11% 3 7% 4 2 3 4 3 5% 38%	2240
April	1st to 10th	Day	20% 13% 4 7% 5% 2 4 3 3 6% 32%	2160
	11th to 20th	Day	20% 8% 3 5% 5% 3 4 3 4 6% 39%	2134
	21st to end	Day	21% 9% 4 8% 6% 4 3 4 4 6% 32%	2290
May	1st to 10th	Day	19% 8% 3 6% 6% 3 5% 5% 6% 6% 34%	2483
	11th to 20th	Day	15% 7% 4 6% 6% 3 4 4 4 7% 40%	2478
	21st to end	Day	13% 6% 3 6% 5% 4 5% 6% 6% 7% 40%	2725
June	1st to 10th	Day	20% 7% 3 6% 5% 4 5% 5% 6% 7% 31%	2520
	11th to 20th	Day	17% 5% 2 4 5% 4 5% 5% 6% 9% 38%	2520
	21st to end	Day	17% 7% 3 6% 5% 3 6% 5% 5% 8% 34%	2520
July	1st to 10th	Day	12% 5% 3 5% 6% 3 5% 5% 6% 9% 41%	2520
	11th to 20th	Day	12% 6% 2 6% 6% 3 5% 5% 7% 10% 37%	2520
	21st to end	Day	10% 6% 3 6% 6% 4 7% 6% 7% 8% 36%	2744
August	1st to 10th	Day	11% 6% 2 6% 6% 4 6% 6% 6% 9% 38%	2356
	11th to 20th	Day	12% 6% 3 6% 6% 4 6% 6% 6% 9% 37%	2303
	21st to end	Day	14% 7% 2 6% 5% 4 4 5% 6% 8% 39%	2391
September	1st to 10th	Day	13% 5% 4 5% 5% 3 6% 5% 5% 8% 42%	2160
	11th to 20th	Day	12% 5% 3 5% 4 3 4 4 4 8% 48%	2160
	21st to end	Day	18% 6% 3 4 5% 3 4 5% 6% 8% 38%	1895
October	1st to 10th	Day	20% 8% 3 7% 4 3 5% 4 5% 6% 35%	1800
	11th to 20th	Day	22% 8% 3 8% 6% 4 5% 5% 6% 7% 28%	1800
	21st to end	Day	27% 11% 4 6% 6% 3 4 5% 4 5% 26%	1913
November	1st to 10th	Day	16% 8% 4 6% 6% 4 5% 6% 5% 7% 34%	1633
	11th to 20th	Day	18% 11% 4 7% 7% 4 4 3 6% 6% 30%	1520
	21st to end	Day	22% 13% 5% 7% 6% 2 5% 5% 4 6% 24%	1520
December	1st to 10th	Day	21% 15% 5% 8% 6% 4 5% 5% 5% 6% 20%	1520
	11th to 20th	Day	19% 15% 6% 7% 6% 3 4 4 4 5% 27%	1906
	21st to end	Day	28% 16% 5% 9% 6% 3 3 2 3 4 20%	2772
January	1st to 10th	Night	19% 13% 7% 10% 7% 4 5% 5% 5% 6% 21%	4429
	11th to 20th	Night	14% 14% 5% 10% 10% 4 6% 5% 6% 5% 21%	4440
	21st to end	Night	20% 15% 7% 10% 7% 4 4 4 4 4 21%	4591
February	1st to 10th	Night	15% 14% 5% 9% 8% 3 5% 5% 6% 6% 25%	2470
	11th to 20th	Night	14% 13% 7% 8% 7% 4 5% 4 5% 5% 29%	2397
	21st to end	Night	16% 12% 4 8% 6% 3 4 6% 4 7% 30%	1816
March	1st to 10th	Night	15% 11% 4 7% 6% 3 5% 5% 5% 5% 34%	2072
	11th to 20th	Night	18% 12% 5% 6% 6% 3 3 4 5% 6% 34%	1979
	21st to end	Night	17% 8% 4 7% 5% 3 4 3 5% 4 39%	2116
April	1st to 10th	Night	20% 10% 4 7% 5% 2 4 4 4 6% 35%	1800
	11th to 20th	Night	18% 7% 2 7% 5% 3 5% 4 5% 5% 38%	1775
	21st to end	Night	19% 8% 3 6% 5% 4 5% 5% 5% 7% 33%	1686
May	1st to 10th	Night	21% 7% 3 4 5% 3 3 5% 5% 8% 37%	1476
	11th to 20th	Night	14% 6% 3 5% 4 3 4 5% 5% 8% 44%	1415
	21st to end	Night	11% 5% 2 5% 5% 3 6% 4 4 8% 47%	1550
June	1st to 10th	Night	16% 6% 3 5% 6% 3 6% 5% 6% 8% 36%	1440
	11th to 20th	Night	12% 6% 2 6% 5% 3 4 4 5% 9% 44%	1440
	21st to end	Night	14% 5% 3 5% 7% 3 4 5% 5% 9% 41%	1440
July	1st to 10th	Night	8% 5% 3 6% 5% 2 5% 5% 5% 8% 48%	1440
	11th to 20th	Night	11% 5% 2 5% 4 2 5% 6% 6% 9% 45%	1440
	21st to end	Night	11% 4 2 4 5% 2 4 5% 6% 8% 49%	1574
August	1st to 10th	Night	9% 6% 2 4 5% 3 5% 5% 5% 8% 47%	1579
	11th to 20th	Night	8% 6% 2 6% 6% 4 4 6% 7% 7% 45%	1598
	21st to end	Night	11% 5% 3 5% 5% 3 4 5% 5% 9% 46%	1946
September	1st to 10th	Night	12% 6% 2 4 4 3 4 4 5% 8% 47%	1800
	11th to 20th	Night	13% 4 2 4 4 3 4 4 5% 6% 52%	1800
	21st to end	Night	16% 6% 2 5% 5% 3 5% 4 5% 6% 44%	2062
October	1st to 10th	Night	16% 8% 4 6% 5% 3 4 5% 5% 7% 38%	2160
	11th to 20th	Night	21% 8% 3 8% 6% 3 5% 4 5% 5% 31%	2160
	21st to end	Night	23% 11% 3 6% 6% 4 4 5% 5% 6% 29%	2443
November	1st to 10th	Night	18% 9% 4 5% 4 4 4 5% 4 6% 37%	2440
	11th to 20th	Night	18% 9% 4 7% 5% 4 5% 4 5% 7% 32%	2660
	21st to end	Night	20% 13% 4 8% 5% 3 5% 5% 5% 6% 26%	2660
December	1st to 10th	Night	21% 14% 5% 8% 7% 4 5% 4 5% 6% 20%	2660
	11th to 20th	Night	20% 14% 5% 8% 6% 3 4 3 4 5% 28%	3288
	21st to end	Night	30% 16% 4 8% 6% 3 4 4 4 5% 17%	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% 13% 6% 2	2518
	11th to 20th	Day	66% 5% 11% 11% 7%	2520
	21st to end	Day	71% 4 8% 10% 5% 1	3064
February	1st to 10th	Day	62% 6% 10% 16% 5% 1	1710
	11th to 20th	Day	60% 5% 10% 14% 11% 1	1663
	21st to end	Day	63% 5% 8% 11% 11% 1	1440
March	1st to 10th	Day	57% 4 13% 14% 9% 2	1876
	11th to 20th	Day	56% 6% 10% 16% 11% 2	1980
	21st to end	Day	51% 4 7% 19% 14% 5%	2240
April	1st to 10th	Day	56% 3 7% 18% 13% 3	2160
	11th to 20th	Day	47% 5% 8% 23% 16% 2	2134
	21st to end	Day	53% 5% 8% 16% 14% 4	2290
May	1st to 10th	Day	50% 5% 10% 17% 14% 4	2483
	11th to 20th	Day	45% 6% 10% 22% 15% 3	2482
	21st to end	Day	41% 8% 14% 20% 14% 3	2725
June	1st to 10th	Day	50% 8% 10% 17% 13% 1	2520
	11th to 20th	Day	42% 7% 11% 24% 14% 2	2520
	21st to end	Day	47% 7% 14% 18% 13% 1	2520
July	1st to 10th	Day	37% 9% 11% 26% 15% 1	2450
	11th to 20th	Day	38% 9% 16% 26% 10%	2445
	21st to end	Day	42% 9% 14% 24% 10% 1	2591
August	1st to 10th	Day	41% 8% 16% 24% 11% 1	2342
	11th to 20th	Day	42% 9% 15% 24% 10% 1	2303
	21st to end	Day	41% 7% 14% 27% 11% 1	2391
September	1st to 10th	Day	39% 9% 13% 26% 13% 1	2160
	11th to 20th	Day	34% 7% 13% 30% 15% 1	2160
	21st to end	Day	43% 8% 12% 27% 9%	1895
October	1st to 10th	Day	50% 7% 11% 20% 12% 1	1800
	11th to 20th	Day	54% 7% 15% 17% 6% 1	1800
	21st to end	Day	60% 6% 10% 16% 7%	1913
November	1st to 10th	Day	47% 8% 14% 20% 9% 1	1633
	11th to 20th	Day	56% 5% 13% 16% 10% 1	1520
	21st to end	Day	60% 8% 12% 12% 8%	1520
December	1st to 10th	Day	65% 8% 10% 12% 5%	1520
	11th to 20th	Day	61% 7% 14% 12% 7%	1906
	21st to end	Day	70% 4 7% 14% 5%	2772
January	1st to 10th	Night	62% 9% 12% 12% 4	4429
	11th to 20th	Night	63% 9% 12% 11% 5% 1	4440
	21st to end	Night	66% 7% 10% 11% 6% 1	4591
February	1st to 10th	Night	59% 7% 11% 17% 6%	2470
	11th to 20th	Night	56% 5% 10% 19% 9% 1	2399
	21st to end	Night	54% 6% 11% 19% 10% 1	1816
March	1st to 10th	Night	51% 5% 11% 19% 12% 2	2082
	11th to 20th	Night	51% 5% 11% 20% 11% 1	1980
	21st to end	Night	48% 4 8% 20% 17% 3	2116
April	1st to 10th	Night	50% 4 7% 21% 14% 3	1800
	11th to 20th	Night	47% 6% 9% 20% 17% 2	1775
	21st to end	Night	50% 6% 9% 16% 16% 3	1686
May	1st to 10th	Night	46% 5% 8% 19% 17% 5%	1476
	11th to 20th	Night	39% 5% 12% 26% 16% 3	1416
	21st to end	Night	35% 7% 16% 20% 19% 3	1551
June	1st to 10th	Night	45% 7% 13% 22% 12% 1	1440
	11th to 20th	Night	37% 6% 14% 21% 19% 2	1440
	21st to end	Night	40% 8% 15% 23% 13% 1	1440
July	1st to 10th	Night	31% 8% 13% 25% 20% 3	1400
	11th to 20th	Night	36% 8% 13% 30% 14%	1392
	21st to end	Night	32% 8% 15% 31% 13% 1	1486
August	1st to 10th	Night	34% 8% 17% 29% 12% 1	1569
	11th to 20th	Night	35% 9% 14% 28% 13% 1	1598
	21st to end	Night	34% 9% 13% 30% 13%	1946
September	1st to 10th	Night	36% 7% 15% 27% 14% 1	1800
	11th to 20th	Night	31% 8% 14% 33% 14% 1	1800
	21st to end	Night	41% 8% 10% 30% 11% 1	2062
October	1st to 10th	Night	46% 8% 11% 21% 14% 1	2160
	11th to 20th	Night	53% 7% 13% 19% 8%	2160
	21st to end	Night	56% 6% 13% 15% 10%	2443
November	1st to 10th	Night	47% 5% 15% 22% 10% 1	2440
	11th to 20th	Night	52% 6% 12% 19% 10% 2	2660
	21st to end	Night	57% 8% 13% 16% 6%	2660
December	1st to 10th	Night	64% 7% 12% 13% 4	2660
	11th to 20th	Night	60% 5% 11% 16% 7% 1	3288
	21st to end	Night	70% 5% 9% 11% 4	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	26% 22% 30% 19% 3 1	180
	11th to 20th	Day	28% 22% 32% 14% 4	180
	21st to end	Day	26% 20% 36% 15% 3	281
February	1st to 10th	Day	30% 29% 30% 10% 1	270
	11th to 20th	Day	28% 27% 39% 6%	267
	21st to end	Day	37% 20% 32% 9% 2	306
March	1st to 10th	Day	25% 20% 35% 15% 4	420
	11th to 20th	Day	29% 21% 31% 15% 4	420
	21st to end	Day	33% 19% 27% 14% 6% 1	462
April	1st to 10th	Day	28% 22% 32% 13% 5%	420
	11th to 20th	Day	30% 23% 20% 17% 7% 3	412
	21st to end	Day	28% 20% 34% 10% 6% 2	420
May	1st to 10th	Day	26% 17% 29% 18% 7% 4	423
	11th to 20th	Day	18% 17% 36% 19% 7% 3	447
	21st to end	Day	17% 16% 35% 19% 9% 4	485
June	1st to 10th	Day	24% 12% 34% 21% 7% 2	450
	11th to 20th	Day	16% 17% 31% 23% 12% 2	450
	21st to end	Day	20% 13% 33% 20% 11% 3	450
July	1st to 10th	Day	11% 10% 29% 33% 15% 3	445
	11th to 20th	Day	15% 9% 30% 29% 13% 4	444
	21st to end	Day	14% 9% 37% 27% 11% 3	488
August	1st to 10th	Day	12% 9% 29% 31% 14% 6%	446
	11th to 20th	Day	12% 7% 28% 31% 17% 5%	439
	21st to end	Day	14% 11% 33% 22% 12% 8%	495
September	1st to 10th	Day	15% 11% 31% 23% 12% 7%	450
	11th to 20th	Day	14% 10% 26% 23% 16% 11%	450
	21st to end	Day	18% 13% 30% 22% 11% 6%	450
October	1st to 10th	Day	25% 18% 24% 18% 11% 5%	450
	11th to 20th	Day	26% 20% 30% 18% 5% 1	450
	21st to end	Day	32% 20% 26% 19% 3	462
November	1st to 10th	Day	28% 16% 27% 20% 8% 1	327
	11th to 20th	Day	28% 22% 34% 11% 4 1	180
	21st to end	Day	27% 21% 34% 14% 4 1	180
December	1st to 10th	Day	31% 17% 36% 13% 3 1	180
	11th to 20th	Day	35% 23% 29% 9% 3 1	180
	21st to end	Day	34% 22% 32% 9% 2 1	198
January	1st to 10th	Night	28% 18% 31% 19% 3	760
	11th to 20th	Night	26% 17% 32% 19% 5%	760
	21st to end	Night	21% 15% 35% 25% 3 1	836
February	1st to 10th	Night	22% 19% 37% 19% 2	760
	11th to 20th	Night	22% 18% 39% 17% 4	742
	21st to end	Night	25% 18% 35% 19% 3	592
March	1st to 10th	Night	22% 18% 36% 21% 3	720
	11th to 20th	Night	25% 19% 29% 23% 3 1	720
	21st to end	Night	23% 14% 34% 20% 7% 1	792
April	1st to 10th	Night	25% 16% 34% 21% 4	720
	11th to 20th	Night	23% 21% 28% 20% 7% 1	711
	21st to end	Night	24% 12% 30% 23% 11%	606
May	1st to 10th	Night	24% 9% 27% 27% 10% 2	396
	11th to 20th	Night	17% 9% 32% 34% 8%	354
	21st to end	Night	12% 8% 38% 28% 12% 1	389
June	1st to 10th	Night	16% 8% 37% 29% 10%	360
	11th to 20th	Night	14% 7% 35% 31% 12% 1	360
	21st to end	Night	16% 5% 27% 39% 12%	360
July	1st to 10th	Night	7% 9% 29% 38% 17% 1	350
	11th to 20th	Night	13% 3 28% 37% 19% 1	348
	21st to end	Night	12% 5% 27% 42% 13% 1	394
August	1st to 10th	Night	11% 5% 26% 34% 23% 1	505
	11th to 20th	Night	9% 5% 22% 35% 25% 3	534
	21st to end	Night	13% 6% 30% 31% 18% 2	758
September	1st to 10th	Night	15% 5% 32% 30% 16% 2	720
	11th to 20th	Night	14% 6% 24% 28% 23% 4	720
	21st to end	Night	19% 10% 23% 28% 18% 3	720
October	1st to 10th	Night	21% 13% 26% 23% 16% 1	720
	11th to 20th	Night	26% 13% 30% 23% 8% 1	720
	21st to end	Night	29% 13% 29% 23% 5%	792
November	1st to 10th	Night	25% 11% 29% 26% 8%	740
	11th to 20th	Night	24% 16% 34% 18% 7% 1	760
	21st to end	Night	30% 15% 29% 19% 6%	760
December	1st to 10th	Night	31% 17% 30% 18% 3	760
	11th to 20th	Night	27% 18% 35% 17% 2 1	760
	21st to end	Night	36% 15% 31% 17% 2	836

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