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 2024-01-16.

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	22% 13% 5% 9% 6% 3 4 4 5% 6% 23%	74766
	Night	22% 16% 7% 11% 6% 3 4 3 4 5% 19%	75054
Transparency	Day	66% 7% 9% 13% 6% 1	74469
	Night	69% 6% 8% 12% 5% 1	74886
Seeing	Day	28% 20% 29% 17% 5% 1	16507
	Night	28% 20% 28% 18% 5% 1	24036

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	18% 22% 12% 20% 8% 4 4 3 1 2 6%	1516
	11th to 20th	Day	20% 17% 10% 20% 11% 4 3 2 3 3 6%	1481
	21st to end	Day	13% 17% 10% 24% 14% 4 4 3 3 2 7%	1620
February	1st to 10th	Day	17% 14% 9% 18% 13% 5% 6% 4 3 2 8%	1620
	11th to 20th	Day	16% 19% 8% 12% 13% 4 6% 3 4 4 10%	1573
	21st to end	Day	10% 13% 6% 13% 11% 6% 5% 4 5% 6% 20%	1454
March	1st to 10th	Day	12% 14% 8% 12% 10% 5% 4 4 4 5% 21%	1796
	11th to 20th	Day	14% 14% 8% 12% 10% 3 6% 5% 5% 5% 17%	1980
	21st to end	Day	17% 17% 7% 9% 8% 3 4 4 4 5% 21%	2290
April	1st to 10th	Day	20% 13% 5% 11% 7% 3 4 5% 4 6% 22%	2160
	11th to 20th	Day	22% 13% 4 7% 4 3 3 3 4 5% 32%	2134
	21st to end	Day	19% 12% 4 6% 5% 3 6% 5% 5% 5% 30%	2351
May	1st to 10th	Day	28% 12% 3 5% 5% 3 5% 5% 5% 5% 25%	2520
	11th to 20th	Day	23% 10% 3 5% 5% 3 3 5% 6% 7% 31%	2478
	21st to end	Day	24% 10% 3 5% 6% 2 4 4 5% 7% 30%	2724
June	1st to 10th	Day	29% 11% 2 6% 5% 3 4 4 6% 7% 24%	2520
	11th to 20th	Day	19% 8% 3 6% 4 4 5% 4 5% 7% 35%	2520
	21st to end	Day	27% 9% 3 6% 5% 3 5% 4 5% 6% 27%	2520
July	1st to 10th	Day	21% 6% 3 5% 4 3 5% 5% 6% 9% 33%	2520
	11th to 20th	Day	20% 7% 2 6% 5% 3 5% 6% 6% 9% 31%	2520
	21st to end	Day	24% 8% 3 6% 6% 4 5% 4 5% 7% 26%	2745
August	1st to 10th	Day	19% 6% 3 7% 6% 3 5% 5% 7% 8% 31%	2504
	11th to 20th	Day	22% 6% 3 6% 6% 3 5% 5% 5% 7% 32%	2304
	21st to end	Day	21% 7% 3 5% 6% 3 5% 5% 6% 8% 32%	2386
September	1st to 10th	Day	23% 7% 2 5% 4 3 4 4 6% 9% 34%	2160
	11th to 20th	Day	26% 9% 3 5% 6% 3 4 4 5% 6% 29%	2160
	21st to end	Day	24% 10% 3 5% 4 3 4 4 5% 5% 32%	1916
October	1st to 10th	Day	28% 9% 3 5% 5% 3 3 5% 5% 7% 28%	1800
	11th to 20th	Day	28% 12% 4 6% 6% 4 4 4 4 7% 20%	1800
	21st to end	Day	27% 21% 4 7% 6% 2 4 3 5% 6% 15%	1822
November	1st to 10th	Day	27% 22% 4 10% 6% 2 4 4 3 5% 14%	1623
	11th to 20th	Day	23% 29% 8% 7% 5% 3 3 3 3 4 12%	1520
	21st to end	Day	17% 33% 12% 8% 4 3 3 3 4 5% 8%	1520
December	1st to 10th	Day	24% 26% 14% 11% 5% 3 3 3 2 3 5%	1520
	11th to 20th	Day	24% 24% 14% 18% 6% 2 2 2 2 2 3	1906
	21st to end	Day	20% 25% 12% 15% 6% 2 3 2 2 3 10%	2783
January	1st to 10th	Night	20% 23% 13% 19% 8% 3 3 2 2 2 4	2649
	11th to 20th	Night	20% 19% 10% 23% 10% 3 3 2 2 3 5%	2601
	21st to end	Night	14% 18% 12% 21% 12% 3 3 3 3 3 7%	2736
February	1st to 10th	Night	18% 15% 6% 19% 13% 5% 5% 4 3 3 9%	2340
	11th to 20th	Night	17% 18% 7% 15% 11% 5% 4 3 4 4 12%	2273
	21st to end	Night	10% 16% 8% 14% 11% 4 5% 4 4 5% 19%	1801
March	1st to 10th	Night	14% 14% 7% 13% 9% 3 5% 4 4 5% 22%	2148
	11th to 20th	Night	15% 16% 7% 12% 8% 4 5% 3 4 5% 21%	1979
	21st to end	Night	18% 18% 7% 10% 7% 2 5% 3 3 4 22%	2066
April	1st to 10th	Night	21% 15% 6% 9% 6% 3 5% 4 6% 6% 21%	1800
	11th to 20th	Night	18% 13% 5% 8% 5% 2 4 4 5% 5% 31%	1776
	21st to end	Night	20% 14% 4 7% 6% 3 4 4 4 5% 30%	1605
May	1st to 10th	Night	26% 12% 3 5% 4 2 3 4 4 6% 30%	1440
	11th to 20th	Night	24% 9% 3 5% 4 2 4 3 5% 5% 35%	1416
	21st to end	Night	21% 10% 3 6% 6% 3 5% 6% 6% 7% 28%	1550
June	1st to 10th	Night	29% 10% 4 6% 5% 3 6% 4 4 6% 23%	1440
	11th to 20th	Night	21% 8% 3 7% 4 3 3 4 6% 6% 36%	1440
	21st to end	Night	26% 9% 4 6% 5% 3 4 4 6% 7% 27%	1440
July	1st to 10th	Night	20% 5% 3 6% 5% 3 5% 6% 7% 9% 32%	1440
	11th to 20th	Night	19% 7% 3 6% 4 4 5% 5% 6% 8% 34%	1440
	21st to end	Night	25% 8% 3 5% 6% 3 4 5% 6% 8% 27%	1573
August	1st to 10th	Night	15% 6% 3 7% 5% 4 6% 7% 7% 8% 31%	1433
	11th to 20th	Night	22% 8% 3 6% 6% 3 5% 5% 6% 6% 31%	1596
	21st to end	Night	17% 6% 3 6% 5% 3 5% 4 7% 8% 36%	1970
September	1st to 10th	Night	19% 7% 3 5% 5% 4 5% 4 5% 8% 35%	1800
	11th to 20th	Night	28% 8% 3 5% 5% 2 4 3 5% 6% 32%	1800
	21st to end	Night	23% 7% 3 6% 6% 3 4 4 5% 6% 31%	2040
October	1st to 10th	Night	25% 9% 3 7% 6% 3 4 4 5% 6% 28%	2160
	11th to 20th	Night	30% 13% 3 6% 5% 2 4 3 5% 6% 22%	2160
	21st to end	Night	32% 18% 4 7% 6% 3 3 3 4 5% 15%	2533
November	1st to 10th	Night	23% 23% 5% 8% 5% 3 4 4 4 4 18%	2452
	11th to 20th	Night	25% 24% 7% 8% 5% 3 3 4 4 5% 12%	2660
	21st to end	Night	24% 31% 9% 9% 4 2 3 2 3 3 9%	2660
December	1st to 10th	Night	22% 29% 13% 12% 4 3 3 3 3 3 6%	2660
	11th to 20th	Night	24% 24% 13% 18% 7% 3 3 2 2 1 5%	3293
	21st to end	Night	27% 22% 12% 15% 5% 2 2 2 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	90% 4 2 3 1	1517
	11th to 20th	Day	87% 4 4 4 1	1481
	21st to end	Day	86% 4 3 5% 3	1620
February	1st to 10th	Day	86% 3 4 5% 2	1620
	11th to 20th	Day	82% 5% 5% 5% 2 1	1581
	21st to end	Day	70% 8% 6% 9% 6% 1	1454
March	1st to 10th	Day	67% 9% 5% 11% 7%	1800
	11th to 20th	Day	72% 6% 6% 11% 4	1980
	21st to end	Day	70% 7% 6% 10% 6% 2	2290
April	1st to 10th	Day	68% 9% 6% 10% 6% 1	2160
	11th to 20th	Day	59% 5% 7% 16% 11% 1	2134
	21st to end	Day	58% 9% 9% 15% 9% 1	2351
May	1st to 10th	Day	62% 8% 7% 13% 7% 2	2520
	11th to 20th	Day	56% 7% 9% 19% 8%	2482
	21st to end	Day	56% 8% 10% 17% 9%	2724
June	1st to 10th	Day	62% 6% 10% 16% 5%	2520
	11th to 20th	Day	52% 7% 11% 21% 9%	2520
	21st to end	Day	61% 7% 9% 14% 8% 1	2520
July	1st to 10th	Day	49% 9% 16% 20% 6%	2450
	11th to 20th	Day	52% 8% 13% 19% 8% 1	2444
	21st to end	Day	59% 7% 13% 15% 6%	2592
August	1st to 10th	Day	53% 9% 13% 20% 5%	2490
	11th to 20th	Day	54% 9% 13% 19% 4 1	2304
	21st to end	Day	53% 8% 13% 21% 6%	2386
September	1st to 10th	Day	50% 8% 12% 21% 9% 1	2160
	11th to 20th	Day	57% 6% 9% 20% 7% 1	2160
	21st to end	Day	54% 7% 10% 19% 9% 1	1916
October	1st to 10th	Day	58% 7% 10% 17% 9%	1800
	11th to 20th	Day	67% 6% 11% 12% 4	1800
	21st to end	Day	73% 6% 7% 10% 3	1822
November	1st to 10th	Day	74% 5% 9% 9% 2	1623
	11th to 20th	Day	80% 4 7% 6% 3	1520
	21st to end	Day	82% 5% 7% 5% 1	1520
December	1st to 10th	Day	88% 4 4 2 1	1520
	11th to 20th	Day	90% 5% 2 2	1905
	21st to end	Day	84% 5% 7% 2 2	2783
January	1st to 10th	Night	90% 4 3 2	2649
	11th to 20th	Night	89% 4 3 3 1	2601
	21st to end	Night	85% 3 4 6% 2	2736
February	1st to 10th	Night	84% 4 5% 5% 2	2340
	11th to 20th	Night	80% 5% 5% 8% 2	2276
	21st to end	Night	70% 7% 7% 9% 6% 1	1801
March	1st to 10th	Night	65% 9% 7% 14% 6% 1	2157
	11th to 20th	Night	68% 5% 6% 14% 6%	1980
	21st to end	Night	68% 7% 7% 11% 6% 2	2066
April	1st to 10th	Night	66% 8% 8% 10% 7% 1	1800
	11th to 20th	Night	58% 6% 7% 17% 11% 2	1776
	21st to end	Night	59% 8% 7% 15% 11% 1	1605
May	1st to 10th	Night	56% 7% 9% 17% 9% 1	1440
	11th to 20th	Night	52% 6% 8% 20% 11% 3	1417
	21st to end	Night	54% 8% 10% 19% 8% 1	1551
June	1st to 10th	Night	63% 6% 9% 15% 6% 1	1440
	11th to 20th	Night	50% 6% 11% 21% 11% 1	1440
	21st to end	Night	58% 9% 10% 15% 8%	1440
July	1st to 10th	Night	47% 10% 18% 20% 5%	1401
	11th to 20th	Night	49% 8% 13% 21% 8% 1	1392
	21st to end	Night	56% 8% 13% 17% 5%	1486
August	1st to 10th	Night	48% 10% 14% 21% 6%	1422
	11th to 20th	Night	52% 10% 16% 18% 5%	1596
	21st to end	Night	46% 9% 16% 22% 7%	1970
September	1st to 10th	Night	49% 9% 12% 21% 10%	1800
	11th to 20th	Night	54% 6% 10% 20% 9% 2	1800
	21st to end	Night	54% 7% 9% 21% 8% 1	2040
October	1st to 10th	Night	57% 7% 10% 16% 9% 1	2160
	11th to 20th	Night	64% 6% 11% 15% 4	2160
	21st to end	Night	73% 6% 6% 11% 4	2533
November	1st to 10th	Night	72% 7% 10% 8% 3	2452
	11th to 20th	Night	77% 6% 7% 8% 2	2660
	21st to end	Night	83% 5% 7% 4 1	2660
December	1st to 10th	Night	86% 5% 5% 4 1	2660
	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	27% 31% 28% 11% 3	356
	21st to end	Day	22% 31% 34% 10% 2	374
February	1st to 10th	Day	26% 40% 25% 7% 2	340
	11th to 20th	Day	30% 35% 25% 9%	336
	21st to end	Day	18% 31% 31% 16% 4	280
March	1st to 10th	Day	20% 27% 36% 12% 3 1	340
	11th to 20th	Day	20% 30% 30% 15% 5% 1	420
	21st to end	Day	25% 27% 30% 14% 4 1	462
April	1st to 10th	Day	27% 31% 30% 10% 2	420
	11th to 20th	Day	30% 25% 26% 15% 4 1	412
	21st to end	Day	26% 20% 29% 19% 6% 1	487
May	1st to 10th	Day	33% 18% 27% 15% 5% 2	603
	11th to 20th	Day	24% 15% 30% 19% 10% 1	624
	21st to end	Day	30% 15% 31% 18% 5% 1	680
June	1st to 10th	Day	34% 11% 27% 19% 7% 1	630
	11th to 20th	Day	21% 14% 33% 24% 7% 2	630
	21st to end	Day	32% 10% 28% 21% 8% 1	630
July	1st to 10th	Day	25% 10% 32% 25% 7% 1	620
	11th to 20th	Day	24% 7% 32% 26% 9% 1	618
	21st to end	Day	30% 9% 29% 23% 9%	685
August	1st to 10th	Day	24% 7% 31% 25% 12% 1	623
	11th to 20th	Day	24% 11% 29% 23% 9% 3	439
	21st to end	Day	25% 9% 32% 24% 9% 1	495
September	1st to 10th	Day	24% 12% 36% 19% 6% 1	450
	11th to 20th	Day	34% 12% 32% 15% 5% 1	450
	21st to end	Day	28% 21% 30% 14% 5% 1	365
October	1st to 10th	Day	34% 14% 31% 15% 5% 1	360
	11th to 20th	Day	34% 21% 22% 15% 7% 2	360
	21st to end	Day	42% 22% 23% 8% 4 1	396
November	1st to 10th	Day	39% 20% 26% 10% 3 1	365
	11th to 20th	Day	37% 24% 25% 9% 3 1	370
	21st to end	Day	32% 29% 26% 11%	370
December	1st to 10th	Day	34% 30% 26% 8% 2	370
	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	29% 33% 27% 9% 2	829
	21st to end	Night	21% 33% 30% 13% 3	864
February	1st to 10th	Night	26% 31% 30% 13% 1	720
	11th to 20th	Night	24% 34% 30% 9% 3	703
	21st to end	Night	20% 26% 33% 16% 5%	592
March	1st to 10th	Night	18% 28% 36% 15% 3	720
	11th to 20th	Night	19% 26% 29% 19% 6% 1	720
	21st to end	Night	26% 22% 32% 14% 6% 1	680
April	1st to 10th	Night	26% 22% 28% 20% 3	540
	11th to 20th	Night	24% 18% 32% 22% 4 1	534
	21st to end	Night	25% 17% 30% 19% 9%	540
May	1st to 10th	Night	30% 14% 25% 19% 8% 3	540
	11th to 20th	Night	27% 10% 25% 26% 10% 2	532
	21st to end	Night	24% 12% 35% 23% 6%	583
June	1st to 10th	Night	31% 9% 29% 24% 6% 1	540
	11th to 20th	Night	24% 10% 29% 26% 11% 1	540
	21st to end	Night	29% 9% 29% 26% 6% 1	540
July	1st to 10th	Night	20% 6% 31% 31% 11% 1	526
	11th to 20th	Night	22% 5% 28% 36% 8%	522
	21st to end	Night	28% 6% 24% 31% 11% 1	590
August	1st to 10th	Night	20% 6% 28% 34% 11% 1	538
	11th to 20th	Night	25% 6% 22% 32% 12% 2	532
	21st to end	Night	20% 8% 24% 37% 11%	594
September	1st to 10th	Night	25% 8% 27% 31% 8% 1	540
	11th to 20th	Night	33% 11% 24% 23% 9%	540
	21st to end	Night	30% 11% 35% 17% 6% 1	612
October	1st to 10th	Night	32% 13% 26% 24% 6%	720
	11th to 20th	Night	38% 14% 23% 16% 7% 1	720
	21st to end	Night	42% 19% 22% 14% 3	870
November	1st to 10th	Night	36% 23% 26% 12% 2	830
	11th to 20th	Night	36% 24% 26% 10% 4 1	850
	21st to end	Night	35% 27% 27% 9% 2	850
December	1st to 10th	Night	33% 30% 26% 8% 3	850
	11th to 20th	Night	32% 34% 25% 7% 1	850
	21st to end	Night	31% 30% 27% 9% 2 1	935

Page generated at 2024-01-13 10:37:51. Version ac07

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