Cheticamp
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cheticamp 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	20% 14% 5% 12% 6% 4 4 3 5% 5% 22%	131499
	Night	19% 17% 6% 15% 6% 4 3 3 4 4 18%	130239
Transparency	Day	65% 7% 10% 14% 5%	134972
	Night	69% 7% 8% 11% 5%	134863
Seeing	Day	29% 20% 29% 16% 5% 1	19488
	Night	28% 20% 27% 18% 5% 1	27041

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% 26% 11% 25% 8% 4 2 2 2 2 5%	4690
	11th to 20th	Day	17% 22% 13% 23% 6% 4 3 2 3 2 5%	4681
	21st to end	Day	9% 14% 8% 28% 18% 8% 2 2 3 2 5%	5271
February	1st to 10th	Day	16% 16% 8% 21% 11% 7% 4 3 3 2 8%	1890
	11th to 20th	Day	15% 21% 8% 16% 11% 5% 4 3 4 3 9%	1843
	21st to end	Day	11% 15% 5% 15% 10% 7% 4 3 5% 5% 20%	1700
March	1st to 10th	Day	16% 14% 6% 15% 9% 6% 3 2 3 4 22%	4574
	11th to 20th	Day	13% 16% 6% 15% 6% 5% 5% 4 6% 6% 19%	5057
	21st to end	Day	19% 18% 8% 17% 5% 4 4 3 5% 5% 12%	5759
April	1st to 10th	Day	20% 14% 5% 12% 6% 4 4 3 4 6% 22%	2400
	11th to 20th	Day	21% 14% 3 8% 4 3 3 3 5% 5% 30%	2374
	21st to end	Day	19% 14% 4 7% 4 5% 5% 4 5% 5% 30%	2613
May	1st to 10th	Day	24% 17% 4 8% 4 4 4 3 4 5% 23%	6345
	11th to 20th	Day	21% 8% 3 5% 4 4 4 4 6% 8% 33%	6318
	21st to end	Day	19% 10% 3 7% 4 4 4 3 5% 7% 33%	6948
June	1st to 10th	Day	28% 11% 2 6% 4 4 4 3 6% 7% 25%	2800
	11th to 20th	Day	18% 9% 3 6% 4 5% 4 4 5% 7% 35%	2800
	21st to end	Day	27% 10% 3 7% 5% 4 4 4 5% 5% 27%	2800
July	1st to 10th	Day	28% 9% 3 7% 4 5% 4 3 6% 8% 24%	6360
	11th to 20th	Day	23% 6% 2 6% 4 4 4 3 5% 7% 37%	6360
	21st to end	Day	21% 7% 2 7% 5% 5% 5% 4 6% 8% 32%	6927
August	1st to 10th	Day	24% 8% 3 8% 5% 4 4 4 6% 7% 26%	4548
	11th to 20th	Day	18% 7% 3 8% 5% 5% 5% 4 6% 8% 32%	4175
	21st to end	Day	19% 7% 2 6% 4 4 4 3 6% 7% 37%	4322
September	1st to 10th	Day	22% 7% 2 5% 3 4 4 4 6% 9% 36%	2400
	11th to 20th	Day	24% 9% 3 6% 5% 4 4 3 5% 6% 30%	2400
	21st to end	Day	22% 10% 3 6% 4 4 4 4 6% 6% 32%	2127
October	1st to 10th	Day	26% 10% 3 6% 4 4 3 4 5% 7% 28%	2000
	11th to 20th	Day	28% 13% 4 8% 5% 5% 4 3 4 7% 20%	2000
	21st to end	Day	26% 21% 3 9% 5% 3 4 3 5% 6% 16%	2024
November	1st to 10th	Day	27% 25% 3 10% 5% 3 3 3 3 5% 13%	1797
	11th to 20th	Day	22% 32% 7% 8% 4 4 3 3 3 4 11%	1680
	21st to end	Day	18% 35% 10% 9% 4 4 3 3 3 4 8%	1680
December	1st to 10th	Day	16% 32% 13% 16% 5% 4 3 2 2 3 6%	2690
	11th to 20th	Day	20% 21% 12% 22% 5% 3 3 2 2 2 9%	3076
	21st to end	Day	18% 23% 10% 25% 4 3 2 2 1 2 10%	4070
January	1st to 10th	Night	15% 26% 12% 26% 7% 2 2 1 2 2 5%	8234
	11th to 20th	Night	19% 21% 11% 29% 6% 3 2 2 2 2 4	8234
	21st to end	Night	8% 18% 9% 28% 17% 6% 2 1 3 2 5%	8922
February	1st to 10th	Night	17% 18% 5% 22% 11% 6% 4 3 3 3 9%	2730
	11th to 20th	Night	17% 21% 7% 17% 10% 4 4 2 4 3 11%	2663
	21st to end	Night	10% 17% 8% 16% 10% 4 4 3 4 5% 19%	2105
March	1st to 10th	Night	17% 16% 6% 17% 11% 4 3 2 3 3 17%	5469
	11th to 20th	Night	14% 16% 5% 15% 6% 5% 5% 3 5% 5% 20%	5057
	21st to end	Night	18% 22% 10% 13% 5% 4 3 3 3 3 16%	5173
April	1st to 10th	Night	21% 17% 5% 10% 5% 5% 4 3 6% 6% 21%	2000
	11th to 20th	Night	18% 15% 4 9% 4 3 4 3 5% 5% 29%	1976
	21st to end	Night	20% 15% 4 8% 4 5% 3 3 4 4 30%	1782
May	1st to 10th	Night	23% 21% 4 8% 4 4 3 3 4 4 22%	3615
	11th to 20th	Night	19% 10% 2 6% 3 4 5% 3 6% 7% 34%	3596
	21st to end	Night	14% 10% 3 7% 5% 5% 5% 5% 6% 8% 33%	3948
June	1st to 10th	Night	27% 11% 3 7% 5% 5% 4 4 4 6% 25%	1600
	11th to 20th	Night	20% 7% 3 7% 4 4 3 4 6% 6% 38%	1600
	21st to end	Night	25% 9% 3 8% 4 4 4 4 6% 7% 26%	1600
July	1st to 10th	Night	25% 8% 3 8% 5% 5% 5% 4 7% 7% 22%	3619
	11th to 20th	Night	20% 8% 3 6% 3 4 4 3 5% 7% 37%	3620
	21st to end	Night	22% 7% 3 7% 5% 4 4 4 6% 8% 31%	3948
August	1st to 10th	Night	20% 9% 3 8% 5% 5% 6% 5% 6% 7% 25%	2596
	11th to 20th	Night	23% 7% 3 6% 6% 4 4 3 6% 6% 31%	2872
	21st to end	Night	17% 6% 2 7% 3 4 4 3 6% 7% 40%	3576
September	1st to 10th	Night	18% 8% 2 6% 4 5% 4 3 5% 7% 36%	2000
	11th to 20th	Night	26% 8% 3 6% 4 3 4 2 5% 6% 32%	2000
	21st to end	Night	23% 8% 3 7% 5% 4 4 4 5% 6% 32%	2268
October	1st to 10th	Night	25% 9% 3 8% 5% 4 4 3 6% 6% 28%	2400
	11th to 20th	Night	29% 13% 3 7% 4 3 4 3 5% 7% 23%	2400
	21st to end	Night	30% 18% 3 8% 5% 4 3 3 4 6% 16%	2815
November	1st to 10th	Night	23% 25% 4 9% 4 4 4 3 4 4 16%	2718
	11th to 20th	Night	26% 27% 6% 9% 4 3 3 3 3 5% 11%	2940
	21st to end	Night	23% 32% 8% 10% 4 3 3 2 3 3 8%	2940
December	1st to 10th	Night	15% 29% 14% 19% 4 3 3 2 2 3 5%	4720
	11th to 20th	Night	22% 24% 12% 22% 4 3 2 1 2 2 7%	5353
	21st to end	Night	22% 21% 10% 24% 4 3 2 1 2 3 9%	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	87% 4 4 4 1	4691
	11th to 20th	Day	86% 5% 5% 3 1	4710
	21st to end	Day	83% 6% 3 5% 2	5271
February	1st to 10th	Day	85% 3 4 5% 2	1890
	11th to 20th	Day	83% 5% 5% 4 2 1	1851
	21st to end	Day	70% 7% 6% 10% 6% 1	1700
March	1st to 10th	Day	70% 5% 6% 10% 8% 1	4578
	11th to 20th	Day	68% 8% 10% 11% 3	5057
	21st to end	Day	77% 7% 5% 7% 4 1	5759
April	1st to 10th	Day	69% 9% 6% 10% 6% 1	2400
	11th to 20th	Day	60% 5% 7% 16% 11% 1	2374
	21st to end	Day	58% 9% 8% 14% 9% 2	2613
May	1st to 10th	Day	66% 8% 8% 12% 5% 1	6357
	11th to 20th	Day	49% 9% 15% 21% 7%	6322
	21st to end	Day	51% 9% 12% 21% 7%	6948
June	1st to 10th	Day	61% 6% 10% 16% 6%	2800
	11th to 20th	Day	51% 7% 12% 21% 9%	2800
	21st to end	Day	62% 6% 9% 14% 9% 1	2800
July	1st to 10th	Day	59% 7% 13% 14% 6%	6290
	11th to 20th	Day	49% 7% 15% 25% 4	6284
	21st to end	Day	50% 9% 17% 19% 5%	6730
August	1st to 10th	Day	58% 8% 13% 17% 5%	4534
	11th to 20th	Day	51% 11% 14% 20% 4	4214
	21st to end	Day	46% 7% 13% 24% 9%	4322
September	1st to 10th	Day	49% 7% 12% 22% 9% 1	2400
	11th to 20th	Day	55% 7% 11% 20% 6% 1	2400
	21st to end	Day	53% 7% 10% 20% 10% 1	2127
October	1st to 10th	Day	59% 8% 9% 14% 10%	3260
	11th to 20th	Day	63% 7% 11% 14% 5%	3240
	21st to end	Day	68% 6% 8% 16% 2	3258
November	1st to 10th	Day	76% 5% 8% 8% 2	1797
	11th to 20th	Day	81% 4 6% 6% 2	1680
	21st to end	Day	82% 5% 7% 5% 1	1680
December	1st to 10th	Day	86% 7% 4 3	2690
	11th to 20th	Day	86% 4 3 6% 1	3075
	21st to end	Day	83% 5% 6% 3 2	4070
January	1st to 10th	Night	89% 4 4 3 1	8234
	11th to 20th	Night	89% 5% 3 2 1	8280
	21st to end	Night	86% 5% 3 4 2	8922
February	1st to 10th	Night	84% 4 5% 5% 2 1	2730
	11th to 20th	Night	80% 5% 5% 8% 2	2666
	21st to end	Night	71% 7% 6% 8% 6% 1	2105
March	1st to 10th	Night	72% 7% 5% 8% 8% 1	5478
	11th to 20th	Night	66% 8% 10% 10% 6%	5058
	21st to end	Night	74% 6% 4 10% 4 1	5173
April	1st to 10th	Night	66% 8% 8% 11% 8% 1	2000
	11th to 20th	Night	58% 6% 7% 17% 10% 1	1976
	21st to end	Night	59% 7% 7% 14% 11% 2	1782
May	1st to 10th	Night	65% 6% 9% 13% 7% 1	3620
	11th to 20th	Night	47% 8% 13% 23% 9% 1	3597
	21st to end	Night	45% 9% 14% 24% 8%	3949
June	1st to 10th	Night	61% 6% 9% 16% 7% 1	1600
	11th to 20th	Night	48% 6% 11% 22% 11% 1	1600
	21st to end	Night	58% 9% 10% 15% 9%	1600
July	1st to 10th	Night	59% 7% 13% 13% 6% 2	3581
	11th to 20th	Night	46% 7% 15% 23% 8% 1	3572
	21st to end	Night	50% 9% 16% 18% 6%	3831
August	1st to 10th	Night	57% 10% 12% 16% 5%	2585
	11th to 20th	Night	48% 11% 18% 19% 3	2899
	21st to end	Night	42% 8% 17% 26% 7%	3575
September	1st to 10th	Night	48% 8% 11% 22% 10%	2000
	11th to 20th	Night	52% 6% 11% 21% 8% 1	2000
	21st to end	Night	52% 8% 9% 22% 8% 1	2268
October	1st to 10th	Night	53% 10% 12% 15% 9% 1	3920
	11th to 20th	Night	64% 6% 9% 17% 4	3899
	21st to end	Night	67% 7% 8% 16% 3	4540
November	1st to 10th	Night	74% 7% 9% 7% 3	2718
	11th to 20th	Night	79% 6% 7% 7% 2	2940
	21st to end	Night	83% 5% 7% 4 1	2940
December	1st to 10th	Night	84% 6% 5% 4 1	4720
	11th to 20th	Night	87% 4 3 5% 1	5355
	21st to end	Night	81% 5% 5% 6% 2	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% 34% 31% 8% 2	430
	11th to 20th	Day	31% 27% 26% 12% 3	430
	21st to end	Day	25% 30% 33% 9% 2 1	473
February	1st to 10th	Day	26% 36% 26% 7% 3 1	430
	11th to 20th	Day	31% 35% 25% 9%	426
	21st to end	Day	21% 30% 32% 15% 3	355
March	1st to 10th	Day	26% 28% 31% 11% 3 1	430
	11th to 20th	Day	23% 31% 27% 14% 4 1	528
	21st to end	Day	27% 27% 30% 12% 4 1	550
April	1st to 10th	Day	30% 31% 28% 9% 2	500
	11th to 20th	Day	31% 25% 26% 14% 3 1	492
	21st to end	Day	27% 22% 29% 17% 5% 1	575
May	1st to 10th	Day	33% 18% 27% 15% 5% 2	703
	11th to 20th	Day	24% 15% 29% 20% 10% 1	724
	21st to end	Day	28% 16% 33% 17% 5% 1	790
June	1st to 10th	Day	32% 13% 27% 20% 6% 1	730
	11th to 20th	Day	22% 15% 33% 22% 6% 2	730
	21st to end	Day	33% 12% 27% 19% 7% 1	730
July	1st to 10th	Day	27% 12% 31% 23% 6% 1	720
	11th to 20th	Day	24% 8% 32% 26% 9% 1	718
	21st to end	Day	29% 11% 29% 23% 8%	795
August	1st to 10th	Day	24% 8% 32% 24% 11% 1	722
	11th to 20th	Day	22% 12% 31% 24% 8% 3	519
	21st to end	Day	24% 12% 32% 23% 8% 1	583
September	1st to 10th	Day	24% 13% 36% 20% 6% 1	530
	11th to 20th	Day	32% 12% 34% 16% 5% 1	530
	21st to end	Day	28% 20% 29% 15% 6% 1	425
October	1st to 10th	Day	33% 15% 32% 15% 5% 1	420
	11th to 20th	Day	34% 20% 23% 15% 6% 2	420
	21st to end	Day	41% 22% 24% 9% 4 1	462
November	1st to 10th	Day	43% 20% 24% 9% 3 1	425
	11th to 20th	Day	38% 25% 24% 9% 3 1	430
	21st to end	Day	34% 30% 25% 11%	430
December	1st to 10th	Day	35% 30% 25% 8% 2	430
	11th to 20th	Day	34% 34% 22% 10%	430
	21st to end	Day	27% 35% 23% 12% 2	473
January	1st to 10th	Night	27% 33% 27% 11% 2	950
	11th to 20th	Night	31% 31% 25% 10% 3 1	950
	21st to end	Night	25% 33% 27% 12% 3	1022
February	1st to 10th	Night	26% 30% 29% 12% 2	840
	11th to 20th	Night	25% 32% 30% 9% 3	823
	21st to end	Night	21% 27% 33% 15% 5%	692
March	1st to 10th	Night	22% 28% 33% 14% 3	840
	11th to 20th	Night	20% 26% 29% 18% 5% 1	829
	21st to end	Night	26% 23% 31% 13% 5% 1	755
April	1st to 10th	Night	28% 22% 28% 19% 3	600
	11th to 20th	Night	25% 18% 32% 21% 4 1	594
	21st to end	Night	26% 17% 30% 19% 8% 1	600
May	1st to 10th	Night	30% 14% 26% 19% 8% 3	600
	11th to 20th	Night	26% 10% 26% 26% 10% 2	592
	21st to end	Night	23% 11% 36% 23% 6%	649
June	1st to 10th	Night	30% 10% 30% 24% 6% 1	600
	11th to 20th	Night	23% 10% 31% 26% 10% 1	600
	21st to end	Night	28% 11% 29% 25% 6% 1	600
July	1st to 10th	Night	21% 7% 30% 31% 11% 1	586
	11th to 20th	Night	22% 5% 28% 36% 8%	582
	21st to end	Night	27% 7% 24% 30% 10%	656
August	1st to 10th	Night	20% 7% 28% 34% 11% 1	598
	11th to 20th	Night	25% 6% 22% 32% 13% 2	592
	21st to end	Night	21% 8% 25% 36% 10%	660
September	1st to 10th	Night	25% 9% 27% 31% 8% 1	600
	11th to 20th	Night	30% 12% 24% 25% 9%	600
	21st to end	Night	30% 12% 33% 19% 6% 1	680
October	1st to 10th	Night	31% 14% 25% 25% 6%	800
	11th to 20th	Night	38% 14% 23% 17% 7% 1	800
	21st to end	Night	40% 20% 22% 14% 3	976
November	1st to 10th	Night	39% 23% 25% 11% 2	930
	11th to 20th	Night	37% 25% 24% 9% 3 1	950
	21st to end	Night	35% 28% 26% 9% 2	950
December	1st to 10th	Night	33% 30% 25% 9% 3	950
	11th to 20th	Night	34% 33% 25% 7% 1	950
	21st to end	Night	31% 29% 28% 9% 2 1	1045

Page generated at 2026-03-15 03:23:50. Version ac07

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