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 2024-12-06.

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	21% 14% 5% 10% 5% 4 4 3 5% 6% 23%	101891
	Night	21% 16% 6% 13% 6% 4 4 3 4 5% 19%	97938
Transparency	Day	64% 7% 9% 13% 5%	105382
	Night	68% 7% 8% 12% 5% 1	102545
Seeing	Day	28% 20% 29% 16% 5% 1	17780
	Night	28% 20% 28% 18% 5% 1	25207

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% 21% 11% 34% 5% 4 3 1 2 2 4	2526
	11th to 20th	Day	13% 18% 10% 28% 8% 5% 3 2 3 3 6%	2530
	21st to end	Day	13% 16% 9% 28% 10% 5% 3 3 4 3 6%	2845
February	1st to 10th	Day	17% 15% 8% 21% 10% 7% 4 3 4 3 8%	1710
	11th to 20th	Day	16% 21% 8% 15% 11% 5% 4 3 4 4 10%	1663
	21st to end	Day	11% 15% 5% 14% 11% 7% 4 3 5% 6% 20%	1542
March	1st to 10th	Day	20% 13% 5% 10% 6% 6% 3 2 3 4 27%	3114
	11th to 20th	Day	11% 21% 8% 15% 7% 5% 5% 4 6% 5% 13%	3480
	21st to end	Day	17% 19% 8% 13% 6% 4 5% 3 5% 5% 14%	4025
April	1st to 10th	Day	20% 14% 5% 12% 6% 4 4 3 4 6% 22%	2280
	11th to 20th	Day	21% 14% 3 8% 4 3 3 3 5% 5% 31%	2254
	21st to end	Day	18% 14% 4 7% 4 5% 5% 4 5% 5% 30%	2482
May	1st to 10th	Day	25% 18% 4 8% 4 3 4 3 4 5% 21%	4425
	11th to 20th	Day	19% 9% 2 5% 5% 4 4 4 6% 8% 35%	4398
	21st to end	Day	22% 12% 3 7% 5% 4 4 3 6% 8% 26%	4836
June	1st to 10th	Day	28% 11% 2 6% 4 4 4 3 6% 7% 23%	2660
	11th to 20th	Day	18% 9% 3 6% 4 5% 4 4 5% 7% 34%	2660
	21st to end	Day	27% 10% 3 7% 5% 4 4 4 5% 5% 26%	2660
July	1st to 10th	Day	26% 7% 2 6% 4 5% 5% 3 6% 8% 27%	4440
	11th to 20th	Day	27% 7% 2 6% 4 4 4 4 5% 7% 30%	4440
	21st to end	Day	19% 7% 3 7% 5% 5% 5% 4 6% 7% 33%	4815
August	1st to 10th	Day	25% 8% 3 8% 5% 4 5% 4 7% 7% 25%	4408
	11th to 20th	Day	19% 7% 3 8% 5% 5% 5% 4 6% 8% 31%	4045
	21st to end	Day	19% 7% 2 6% 4 4 4 3 6% 7% 37%	4190
September	1st to 10th	Day	23% 7% 2 6% 4 4 4 4 6% 9% 34%	2280
	11th to 20th	Day	24% 9% 3 6% 5% 4 4 3 5% 6% 31%	2280
	21st to end	Day	23% 10% 3 6% 4 5% 4 4 6% 5% 31%	2021
October	1st to 10th	Day	27% 10% 3 6% 4 4 3 4 5% 7% 27%	1900
	11th to 20th	Day	29% 13% 4 7% 5% 5% 4 4 4 6% 20%	1900
	21st to end	Day	27% 21% 3 9% 5% 3 4 3 5% 5% 15%	1923
November	1st to 10th	Day	26% 25% 3 10% 5% 3 3 3 3 5% 14%	1710
	11th to 20th	Day	23% 31% 7% 8% 4 4 3 3 3 4 11%	1600
	21st to end	Day	17% 34% 10% 9% 4 4 3 3 3 4 8%	1600
December	1st to 10th	Day	23% 31% 11% 12% 4 4 3 2 2 3 5%	1560
	11th to 20th	Day	24% 26% 13% 19% 5% 3 2 2 2 1 3	1906
	21st to end	Day	20% 27% 11% 17% 5% 3 3 2 2 3 10%	2783
January	1st to 10th	Night	13% 19% 13% 36% 5% 3 2 2 2 2 3	4429
	11th to 20th	Night	16% 19% 8% 34% 7% 4 2 2 2 2 4	4440
	21st to end	Night	12% 21% 9% 24% 11% 4 3 2 5% 3 8%	4820
February	1st to 10th	Night	18% 17% 5% 21% 11% 6% 4 3 3 3 10%	2470
	11th to 20th	Night	18% 20% 6% 17% 9% 5% 4 2 4 4 12%	2403
	21st to end	Night	10% 17% 8% 15% 10% 4 4 3 4 5% 19%	1911
March	1st to 10th	Night	19% 14% 5% 13% 9% 3 3 3 3 4 24%	3709
	11th to 20th	Night	15% 20% 6% 14% 7% 6% 5% 3 4 5% 16%	3479
	21st to end	Night	18% 20% 8% 13% 6% 4 4 3 3 4 17%	3607
April	1st to 10th	Night	20% 16% 5% 9% 5% 5% 4 3 6% 6% 22%	1900
	11th to 20th	Night	17% 14% 4 9% 4 3 4 3 5% 5% 30%	1876
	21st to end	Night	19% 14% 4 8% 4 5% 3 3 4 4 30%	1693
May	1st to 10th	Night	23% 22% 4 7% 4 3 3 3 5% 6% 21%	2525
	11th to 20th	Night	18% 10% 3 5% 3 3 4 3 6% 6% 37%	2506
	21st to end	Night	17% 13% 3 7% 6% 5% 5% 5% 7% 8% 24%	2749
June	1st to 10th	Night	28% 11% 3 7% 5% 5% 4 4 4 6% 23%	1520
	11th to 20th	Night	20% 8% 3 7% 4 3 3 4 6% 6% 37%	1520
	21st to end	Night	25% 9% 3 7% 4 4 4 4 6% 7% 26%	1520
July	1st to 10th	Night	26% 8% 2 7% 4 5% 5% 4 7% 7% 24%	2530
	11th to 20th	Night	27% 7% 2 6% 4 4 4 3 6% 7% 30%	2530
	21st to end	Night	18% 8% 3 7% 5% 4 4 4 5% 8% 34%	2750
August	1st to 10th	Night	20% 9% 3 9% 5% 5% 6% 5% 6% 8% 24%	2516
	11th to 20th	Night	23% 7% 3 6% 6% 4 4 3 6% 7% 30%	2782
	21st to end	Night	17% 6% 2 7% 3 4 4 3 6% 7% 40%	3466
September	1st to 10th	Night	19% 8% 2 6% 5% 5% 4 3 6% 8% 35%	1900
	11th to 20th	Night	27% 8% 2 6% 4 3 4 3 5% 6% 32%	1900
	21st to end	Night	23% 8% 3 7% 5% 4 4 4 5% 6% 32%	2154
October	1st to 10th	Night	25% 9% 3 8% 5% 4 4 4 6% 6% 28%	2280
	11th to 20th	Night	30% 13% 3 7% 4 3 4 2 5% 6% 22%	2280
	21st to end	Night	31% 18% 3 8% 5% 4 3 3 4 5% 16%	2674
November	1st to 10th	Night	23% 25% 4 9% 4 4 4 3 4 4 17%	2585
	11th to 20th	Night	26% 26% 6% 9% 4 3 3 3 4 5% 11%	2800
	21st to end	Night	23% 32% 8% 10% 4 3 3 2 3 3 8%	2800
December	1st to 10th	Night	21% 32% 11% 12% 3 4 2 2 3 3 6%	2737
	11th to 20th	Night	23% 26% 11% 20% 5% 3 2 1 2 1 5%	3293
	21st to end	Night	27% 23% 10% 16% 4 3 2 1 2 3 8%	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	89% 3 4 3 1	2527
	11th to 20th	Day	85% 6% 4 4 1	2530
	21st to end	Day	79% 7% 4 7% 4 1	2845
February	1st to 10th	Day	85% 4 4 5% 2	1710
	11th to 20th	Day	82% 5% 5% 5% 2 1	1671
	21st to end	Day	69% 8% 6% 10% 6% 1	1542
March	1st to 10th	Day	63% 5% 7% 12% 11% 1	3118
	11th to 20th	Day	75% 9% 6% 8% 2	3480
	21st to end	Day	73% 8% 6% 7% 4 1	4025
April	1st to 10th	Day	68% 9% 6% 10% 5% 1	2280
	11th to 20th	Day	59% 5% 7% 17% 11% 1	2254
	21st to end	Day	57% 9% 8% 14% 10% 2	2482
May	1st to 10th	Day	66% 9% 10% 10% 4 1	4440
	11th to 20th	Day	48% 9% 14% 22% 7%	4402
	21st to end	Day	57% 10% 11% 15% 7%	4836
June	1st to 10th	Day	62% 6% 11% 15% 5%	2660
	11th to 20th	Day	51% 7% 12% 21% 8%	2660
	21st to end	Day	62% 6% 9% 14% 8% 1	2660
July	1st to 10th	Day	56% 7% 13% 15% 8%	4370
	11th to 20th	Day	56% 7% 13% 19% 5%	4364
	21st to end	Day	50% 9% 17% 19% 6%	4662
August	1st to 10th	Day	60% 8% 13% 16% 3	4394
	11th to 20th	Day	52% 11% 14% 20% 3	4084
	21st to end	Day	46% 7% 13% 24% 9%	4190
September	1st to 10th	Day	50% 8% 12% 21% 9% 1	2280
	11th to 20th	Day	55% 7% 11% 20% 6% 1	2280
	21st to end	Day	54% 7% 10% 19% 9% 1	2021
October	1st to 10th	Day	60% 8% 8% 14% 10%	3160
	11th to 20th	Day	63% 7% 11% 14% 5%	3140
	21st to end	Day	69% 6% 8% 15% 2	3157
November	1st to 10th	Day	75% 5% 9% 9% 2	1710
	11th to 20th	Day	81% 4 7% 6% 2	1600
	21st to end	Day	82% 5% 7% 5% 1	1600
December	1st to 10th	Day	88% 5% 4 2 1	1560
	11th to 20th	Day	90% 5% 2 2	1905
	21st to end	Day	84% 5% 7% 2 2	2783
January	1st to 10th	Night	92% 3 3 2	4429
	11th to 20th	Night	89% 4 3 2 1	4440
	21st to end	Night	80% 6% 3 6% 4	4820
February	1st to 10th	Night	83% 4 5% 5% 2 1	2470
	11th to 20th	Night	80% 5% 5% 8% 2	2406
	21st to end	Night	70% 7% 7% 8% 6% 1	1911
March	1st to 10th	Night	63% 8% 6% 10% 11% 1	3718
	11th to 20th	Night	72% 8% 6% 10% 4	3480
	21st to end	Night	73% 7% 5% 10% 4 2	3607
April	1st to 10th	Night	65% 8% 8% 11% 8% 1	1900
	11th to 20th	Night	57% 6% 7% 17% 11% 2	1876
	21st to end	Night	58% 7% 7% 14% 11% 2	1693
May	1st to 10th	Night	64% 6% 10% 14% 6% 1	2530
	11th to 20th	Night	47% 6% 11% 26% 8% 1	2507
	21st to end	Night	52% 10% 15% 17% 6%	2750
June	1st to 10th	Night	63% 6% 9% 15% 6% 1	1520
	11th to 20th	Night	49% 6% 11% 22% 11% 1	1520
	21st to end	Night	58% 9% 10% 15% 8%	1520
July	1st to 10th	Night	58% 8% 13% 14% 5% 2	2491
	11th to 20th	Night	55% 7% 12% 17% 8% 1	2482
	21st to end	Night	48% 10% 15% 18% 9%	2663
August	1st to 10th	Night	58% 10% 12% 16% 4	2505
	11th to 20th	Night	49% 11% 18% 18% 3	2809
	21st to end	Night	42% 9% 17% 26% 7%	3465
September	1st to 10th	Night	49% 9% 11% 21% 10%	1900
	11th to 20th	Night	52% 6% 11% 20% 9% 1	1900
	21st to end	Night	53% 8% 10% 21% 8% 1	2154
October	1st to 10th	Night	54% 10% 11% 15% 10% 1	3800
	11th to 20th	Night	65% 6% 9% 17% 4	3779
	21st to end	Night	67% 6% 7% 16% 3	4399
November	1st to 10th	Night	73% 7% 10% 7% 3	2585
	11th to 20th	Night	78% 6% 7% 7% 2	2800
	21st to end	Night	82% 5% 7% 4 1	2800
December	1st to 10th	Night	85% 5% 5% 4 1	2737
	11th to 20th	Night	90% 4 3 3	3295
	21st to end	Night	85% 4 4 5% 2	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	25% 34% 31% 8% 2	370
	11th to 20th	Day	29% 30% 28% 11% 3	370
	21st to end	Day	22% 29% 34% 11% 3 1	407
February	1st to 10th	Day	27% 37% 25% 8% 3 1	370
	11th to 20th	Day	30% 36% 25% 8%	366
	21st to end	Day	20% 30% 32% 16% 4	307
March	1st to 10th	Day	22% 27% 35% 12% 3 1	370
	11th to 20th	Day	20% 30% 29% 16% 5% 1	460
	21st to end	Day	26% 26% 30% 13% 4 1	506
April	1st to 10th	Day	27% 32% 29% 10% 2	460
	11th to 20th	Day	29% 25% 27% 15% 3 1	452
	21st to end	Day	25% 21% 29% 18% 5% 1	531
May	1st to 10th	Day	33% 19% 26% 16% 5% 2	653
	11th to 20th	Day	23% 15% 30% 20% 11% 1	674
	21st to end	Day	29% 16% 32% 18% 4 1	735
June	1st to 10th	Day	33% 13% 27% 20% 7% 1	680
	11th to 20th	Day	22% 15% 33% 23% 6% 2	680
	21st to end	Day	33% 11% 28% 20% 8% 1	680
July	1st to 10th	Day	26% 11% 31% 24% 7% 1	670
	11th to 20th	Day	25% 7% 32% 25% 9% 1	668
	21st to end	Day	28% 10% 29% 24% 9%	740
August	1st to 10th	Day	25% 8% 31% 24% 11% 1	672
	11th to 20th	Day	23% 12% 31% 23% 9% 3	479
	21st to end	Day	24% 10% 32% 24% 9% 1	539
September	1st to 10th	Day	25% 13% 35% 19% 6% 1	490
	11th to 20th	Day	31% 12% 34% 16% 5% 1	490
	21st to end	Day	28% 20% 30% 16% 6% 1	395
October	1st to 10th	Day	34% 14% 31% 15% 5% 1	390
	11th to 20th	Day	35% 21% 22% 14% 6% 2	390
	21st to end	Day	41% 23% 23% 8% 4 1	429
November	1st to 10th	Day	40% 21% 26% 9% 3 1	395
	11th to 20th	Day	38% 25% 24% 9% 3 1	400
	21st to end	Day	33% 30% 26% 11%	400
December	1st to 10th	Day	33% 31% 25% 8% 2	385
	11th to 20th	Day	32% 34% 23% 11% 1	370
	21st to end	Day	25% 37% 23% 13% 2	407
January	1st to 10th	Night	26% 33% 28% 11% 3	850
	11th to 20th	Night	30% 32% 27% 9% 2	850
	21st to end	Night	21% 33% 29% 13% 4	917
February	1st to 10th	Night	26% 29% 29% 13% 2	760
	11th to 20th	Night	24% 34% 30% 9% 3	743
	21st to end	Night	21% 26% 33% 15% 5%	628
March	1st to 10th	Night	19% 28% 35% 15% 3	760
	11th to 20th	Night	19% 26% 29% 19% 6% 1	760
	21st to end	Night	26% 22% 31% 14% 5% 1	717
April	1st to 10th	Night	26% 22% 29% 19% 3	570
	11th to 20th	Night	23% 17% 33% 21% 4 1	564
	21st to end	Night	25% 17% 30% 19% 8% 1	570
May	1st to 10th	Night	29% 15% 26% 19% 8% 3	570
	11th to 20th	Night	26% 9% 25% 27% 11% 2	562
	21st to end	Night	23% 12% 36% 23% 6%	616
June	1st to 10th	Night	30% 10% 29% 24% 6% 1	570
	11th to 20th	Night	24% 10% 30% 26% 10% 1	570
	21st to end	Night	29% 10% 30% 25% 6% 1	570
July	1st to 10th	Night	21% 7% 30% 30% 11% 1	556
	11th to 20th	Night	23% 5% 28% 36% 8%	552
	21st to end	Night	27% 7% 24% 30% 11%	623
August	1st to 10th	Night	20% 7% 28% 33% 11% 1	568
	11th to 20th	Night	25% 6% 23% 32% 12% 2	562
	21st to end	Night	21% 8% 24% 37% 11%	627
September	1st to 10th	Night	25% 8% 27% 31% 8% 1	570
	11th to 20th	Night	31% 11% 25% 24% 9%	570
	21st to end	Night	29% 11% 34% 18% 6% 1	646
October	1st to 10th	Night	31% 13% 25% 24% 6%	760
	11th to 20th	Night	39% 14% 23% 16% 7% 1	760
	21st to end	Night	41% 21% 22% 13% 3	923
November	1st to 10th	Night	37% 23% 26% 11% 2	880
	11th to 20th	Night	36% 25% 25% 9% 4 1	900
	21st to end	Night	35% 27% 27% 9% 2	900
December	1st to 10th	Night	32% 29% 27% 9% 3	878
	11th to 20th	Night	32% 34% 25% 7% 1	850
	21st to end	Night	31% 30% 27% 9% 2 1	935

Page generated at 2024-12-03 07:45:13. Version ac07

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