CAAS - Parc Ecoforestier Johnville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the CAAS - Parc Ecoforestier Johnville clear sky chart from 2005-11-06 to 2024-07-16.

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	19% 13% 4 9% 5% 5% 4 3 5% 6% 26%	89574
	Night	19% 15% 5% 10% 6% 4 4 3 4 5% 25%	89867
Transparency	Day	58% 7% 11% 16% 7% 1	89293
	Night	61% 7% 11% 15% 7% 1	89702
Seeing	Day	28% 18% 28% 17% 7% 2	14282
	Night	27% 15% 27% 23% 8% 1	23162

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% 22% 8% 18% 7% 5% 5% 3 3 3 12%	2517
	11th to 20th	Day	12% 17% 8% 20% 12% 4 3 3 3 4 14%	2520
	21st to end	Day	13% 20% 9% 14% 5% 8% 4 2 3 4 16%	2772
February	1st to 10th	Day	15% 19% 6% 15% 9% 6% 4 3 3 3 16%	1586
	11th to 20th	Day	13% 21% 9% 15% 9% 4 4 3 3 3 16%	1848
	21st to end	Day	13% 20% 6% 10% 7% 6% 5% 3 4 5% 20%	1570
March	1st to 10th	Day	22% 17% 5% 10% 6% 4 3 3 4 4 22%	3116
	11th to 20th	Day	16% 24% 6% 12% 6% 4 3 2 3 4 21%	3288
	21st to end	Day	18% 16% 6% 10% 4 3 3 2 3 5% 30%	4092
April	1st to 10th	Day	22% 17% 4 9% 4 4 3 3 4 5% 25%	2280
	11th to 20th	Day	20% 14% 3 7% 4 4 4 3 3 5% 33%	2300
	21st to end	Day	24% 15% 4 6% 4 4 4 3 4 6% 27%	2470
May	1st to 10th	Day	25% 9% 3 8% 6% 5% 4 3 5% 5% 26%	4154
	11th to 20th	Day	19% 8% 3 8% 5% 5% 5% 4 5% 7% 29%	4398
	21st to end	Day	15% 7% 3 7% 5% 5% 6% 5% 7% 8% 31%	4837
June	1st to 10th	Day	26% 9% 3 6% 5% 5% 5% 3 6% 7% 25%	2660
	11th to 20th	Day	18% 7% 3 7% 5% 4 5% 4 6% 8% 33%	2660
	21st to end	Day	22% 9% 3 8% 5% 5% 5% 3 5% 7% 28%	2660
July	1st to 10th	Day	17% 7% 2 6% 5% 4 5% 4 6% 8% 34%	2660
	11th to 20th	Day	15% 7% 3 7% 6% 5% 6% 6% 7% 9% 29%	2593
	21st to end	Day	18% 8% 2 7% 5% 5% 6% 4 6% 8% 30%	2744
August	1st to 10th	Day	18% 7% 2 7% 6% 5% 5% 5% 6% 9% 30%	2476
	11th to 20th	Day	16% 8% 2 7% 4 5% 5% 4 8% 10% 30%	2304
	21st to end	Day	18% 6% 2 7% 4 5% 4 4 7% 8% 34%	2404
September	1st to 10th	Day	18% 7% 2 6% 4 5% 4 4 6% 7% 38%	2160
	11th to 20th	Day	20% 7% 2 6% 3 3 4 3 4 7% 41%	2010
	21st to end	Day	20% 8% 2 6% 4 4 5% 4 5% 8% 34%	1980
October	1st to 10th	Day	25% 10% 3 6% 4 4 5% 3 6% 7% 27%	1972
	11th to 20th	Day	20% 13% 4 7% 5% 5% 4 4 6% 6% 27%	1683
	21st to end	Day	26% 20% 4 7% 4 3 4 3 4 4 22%	1782
November	1st to 10th	Day	20% 17% 4 7% 5% 4 4 3 4 4 28%	1671
	11th to 20th	Day	19% 18% 6% 11% 5% 4 4 3 5% 5% 22%	1710
	21st to end	Day	19% 18% 6% 11% 5% 3 5% 4 5% 6% 18%	1563
December	1st to 10th	Day	20% 25% 6% 11% 6% 4 4 3 2 3 15%	1475
	11th to 20th	Day	20% 20% 6% 11% 5% 4 4 3 4 4 19%	1887
	21st to end	Day	25% 19% 6% 14% 4 4 3 2 3 3 16%	2772
January	1st to 10th	Night	15% 21% 9% 18% 8% 5% 4 3 2 3 13%	4429
	11th to 20th	Night	13% 19% 8% 20% 9% 6% 4 3 3 3 12%	4440
	21st to end	Night	14% 22% 8% 14% 7% 6% 3 3 3 3 17%	4884
February	1st to 10th	Night	14% 19% 6% 14% 8% 6% 4 3 4 4 18%	2590
	11th to 20th	Night	13% 19% 7% 15% 8% 6% 4 2 3 4 18%	2218
	21st to end	Night	14% 20% 5% 10% 7% 6% 4 4 3 4 24%	1884
March	1st to 10th	Night	23% 18% 4 7% 4 4 3 3 3 4 26%	3724
	11th to 20th	Night	18% 24% 6% 11% 5% 4 4 2 3 3 21%	3657
	21st to end	Night	18% 20% 5% 10% 6% 3 3 2 3 3 27%	3537
April	1st to 10th	Night	23% 15% 4 8% 4 3 4 3 4 4 26%	1900
	11th to 20th	Night	23% 12% 3 6% 5% 4 4 3 4 4 33%	1828
	21st to end	Night	23% 13% 3 7% 5% 3 3 3 4 6% 29%	1710
May	1st to 10th	Night	27% 9% 3 8% 4 4 4 4 5% 6% 26%	2816
	11th to 20th	Night	22% 9% 3 8% 6% 5% 4 3 6% 5% 29%	2495
	21st to end	Night	18% 7% 2 7% 4 5% 4 4 6% 9% 35%	2738
June	1st to 10th	Night	28% 7% 2 6% 4 3 4 3 7% 7% 28%	1520
	11th to 20th	Night	20% 7% 3 5% 4 4 4 5% 6% 8% 35%	1520
	21st to end	Night	20% 8% 4 7% 5% 5% 5% 5% 6% 6% 30%	1520
July	1st to 10th	Night	15% 7% 3 6% 5% 5% 4 5% 6% 8% 36%	1520
	11th to 20th	Night	14% 7% 2 7% 6% 5% 6% 4 7% 9% 35%	1488
	21st to end	Night	15% 7% 2 7% 5% 5% 5% 4 7% 7% 35%	1574
August	1st to 10th	Night	18% 5% 2 6% 4 5% 6% 4 7% 9% 36%	1444
	11th to 20th	Night	15% 7% 3 8% 4 5% 5% 4 5% 7% 36%	1596
	21st to end	Night	17% 7% 2 6% 3 4 4 4 5% 8% 39%	1949
September	1st to 10th	Night	18% 8% 2 7% 4 4 4 3 5% 6% 38%	1800
	11th to 20th	Night	18% 7% 2 5% 3 4 3 4 4 6% 45%	1949
	21st to end	Night	22% 7% 2 4 3 3 3 3 5% 7% 40%	1980
October	1st to 10th	Night	21% 9% 3 6% 5% 4 4 3 5% 6% 33%	1986
	11th to 20th	Night	23% 11% 4 8% 4 5% 4 4 5% 5% 27%	2276
	21st to end	Night	28% 13% 4 7% 4 3 4 4 5% 4 25%	2574
November	1st to 10th	Night	22% 15% 4 8% 5% 4 4 3 4 6% 26%	2407
	11th to 20th	Night	19% 16% 5% 11% 6% 4 3 2 4 5% 25%	2470
	21st to end	Night	21% 18% 5% 13% 6% 3 3 2 3 5% 22%	2612
December	1st to 10th	Night	22% 23% 8% 11% 7% 4 3 2 3 4 13%	2660
	11th to 20th	Night	20% 22% 7% 14% 7% 4 4 3 3 3 14%	3288
	21st to end	Night	24% 22% 5% 11% 5% 4 4 2 3 3 16%	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	76% 7% 9% 6% 1	2518
	11th to 20th	Day	74% 7% 5% 10% 3	2520
	21st to end	Day	73% 4 8% 9% 4 1	2772
February	1st to 10th	Day	75% 4 6% 10% 4 1	1586
	11th to 20th	Day	74% 4 8% 8% 4 1	1857
	21st to end	Day	67% 5% 9% 12% 6% 2	1570
March	1st to 10th	Day	65% 6% 8% 12% 8% 2	3119
	11th to 20th	Day	67% 5% 9% 11% 7% 1	3288
	21st to end	Day	58% 4 7% 16% 13% 1	4092
April	1st to 10th	Day	62% 5% 8% 16% 7% 2	2280
	11th to 20th	Day	55% 5% 8% 20% 12% 1	2300
	21st to end	Day	59% 6% 8% 16% 9% 3	2470
May	1st to 10th	Day	57% 8% 11% 17% 8% 1	4168
	11th to 20th	Day	52% 10% 17% 14% 6% 1	4402
	21st to end	Day	45% 11% 13% 21% 10%	4837
June	1st to 10th	Day	56% 8% 11% 17% 6% 1	2660
	11th to 20th	Day	47% 7% 13% 22% 10% 1	2660
	21st to end	Day	56% 8% 12% 18% 7%	2660
July	1st to 10th	Day	46% 8% 14% 23% 8%	2590
	11th to 20th	Day	47% 9% 16% 22% 6%	2518
	21st to end	Day	50% 10% 14% 20% 5%	2591
August	1st to 10th	Day	50% 9% 17% 20% 4	2462
	11th to 20th	Day	46% 11% 18% 18% 7%	2304
	21st to end	Day	45% 9% 15% 21% 11%	2404
September	1st to 10th	Day	44% 9% 14% 24% 9% 1	2160
	11th to 20th	Day	44% 5% 12% 26% 12%	2010
	21st to end	Day	47% 8% 13% 22% 9% 1	1980
October	1st to 10th	Day	55% 7% 13% 18% 7%	1972
	11th to 20th	Day	56% 8% 15% 17% 5%	1683
	21st to end	Day	66% 5% 9% 13% 5% 1	1782
November	1st to 10th	Day	59% 7% 10% 15% 7% 1	1671
	11th to 20th	Day	66% 5% 9% 11% 7% 1	1710
	21st to end	Day	67% 7% 13% 11% 2	1563
December	1st to 10th	Day	76% 4 9% 7% 3	1475
	11th to 20th	Day	70% 4 7% 13% 5%	1887
	21st to end	Day	74% 6% 7% 9% 5%	2772
January	1st to 10th	Night	76% 6% 11% 5% 2	4429
	11th to 20th	Night	75% 7% 8% 7% 2	4440
	21st to end	Night	73% 4 10% 9% 4 1	4884
February	1st to 10th	Night	70% 5% 8% 11% 5%	2590
	11th to 20th	Night	71% 4 8% 11% 5%	2220
	21st to end	Night	65% 5% 8% 13% 8% 1	1884
March	1st to 10th	Night	62% 4 10% 15% 6% 2	3734
	11th to 20th	Night	67% 6% 8% 11% 7% 1	3658
	21st to end	Night	63% 4 6% 16% 9% 1	3537
April	1st to 10th	Night	60% 6% 8% 16% 10% 1	1900
	11th to 20th	Night	53% 6% 10% 19% 11% 1	1828
	21st to end	Night	57% 6% 9% 16% 10% 2	1710
May	1st to 10th	Night	55% 9% 11% 16% 8% 1	2822
	11th to 20th	Night	50% 10% 15% 17% 7% 1	2496
	21st to end	Night	44% 10% 13% 17% 15% 1	2739
June	1st to 10th	Night	53% 7% 10% 21% 8%	1520
	11th to 20th	Night	46% 8% 12% 22% 10% 2	1520
	21st to end	Night	52% 9% 12% 18% 8%	1520
July	1st to 10th	Night	43% 10% 15% 21% 11% 1	1480
	11th to 20th	Night	42% 11% 15% 24% 8%	1440
	21st to end	Night	44% 10% 17% 22% 8%	1486
August	1st to 10th	Night	41% 9% 19% 25% 6%	1434
	11th to 20th	Night	45% 9% 16% 21% 9%	1596
	21st to end	Night	43% 7% 16% 24% 10%	1949
September	1st to 10th	Night	46% 7% 12% 24% 11%	1800
	11th to 20th	Night	40% 7% 15% 28% 10% 1	1949
	21st to end	Night	43% 7% 14% 24% 11% 2	1980
October	1st to 10th	Night	52% 5% 11% 21% 11%	1986
	11th to 20th	Night	59% 7% 12% 18% 4	2276
	21st to end	Night	61% 7% 10% 14% 7% 1	2574
November	1st to 10th	Night	60% 5% 13% 14% 6% 1	2407
	11th to 20th	Night	62% 6% 10% 13% 7% 2	2470
	21st to end	Night	67% 6% 12% 12% 4	2612
December	1st to 10th	Night	77% 5% 8% 8% 2	2660
	11th to 20th	Night	77% 5% 6% 9% 4	3288
	21st to end	Night	72% 7% 7% 12% 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	32% 21% 30% 17% 1	180
	11th to 20th	Day	36% 23% 27% 10% 3 1	180
	21st to end	Day	29% 21% 32% 13% 5% 1	198
February	1st to 10th	Day	39% 28% 22% 10% 1	218
	11th to 20th	Day	32% 25% 32% 8% 2	456
	21st to end	Day	30% 25% 27% 17% 1	382
March	1st to 10th	Day	33% 19% 31% 14% 3	460
	11th to 20th	Day	31% 26% 23% 15% 4	460
	21st to end	Day	36% 20% 23% 13% 7% 1	506
April	1st to 10th	Day	37% 20% 23% 12% 6% 1	460
	11th to 20th	Day	35% 20% 25% 11% 7% 2	452
	21st to end	Day	35% 19% 28% 13% 3 1	460
May	1st to 10th	Day	37% 16% 27% 15% 6% 1	463
	11th to 20th	Day	25% 17% 31% 19% 6% 1	487
	21st to end	Day	23% 20% 30% 21% 5% 1	529
June	1st to 10th	Day	30% 17% 31% 16% 5% 1	490
	11th to 20th	Day	20% 20% 28% 24% 7% 1	490
	21st to end	Day	24% 17% 34% 15% 9% 1	490
July	1st to 10th	Day	21% 12% 30% 27% 9% 1	485
	11th to 20th	Day	16% 12% 40% 23% 7% 2	465
	21st to end	Day	20% 11% 34% 26% 7% 1	488
August	1st to 10th	Day	19% 13% 28% 27% 13% 1	446
	11th to 20th	Day	21% 10% 27% 24% 15% 3	439
	21st to end	Day	25% 15% 21% 23% 12% 5%	495
September	1st to 10th	Day	20% 12% 29% 21% 12% 5%	450
	11th to 20th	Day	22% 13% 22% 19% 16% 8%	450
	21st to end	Day	20% 13% 25% 24% 13% 5%	450
October	1st to 10th	Day	27% 16% 24% 17% 12% 4	450
	11th to 20th	Day	29% 19% 25% 16% 9% 2	391
	21st to end	Day	43% 15% 21% 15% 5%	396
November	1st to 10th	Day	36% 16% 25% 17% 5%	365
	11th to 20th	Day	29% 22% 27% 14% 6% 1	370
	21st to end	Day	30% 21% 32% 12% 4	223
December	1st to 10th	Day	35% 19% 26% 16% 3 1	180
	11th to 20th	Day	34% 27% 28% 8% 3 1	180
	21st to end	Day	41% 20% 27% 10% 2 1	198
January	1st to 10th	Night	30% 22% 29% 16% 2	760
	11th to 20th	Night	29% 21% 30% 16% 4	760
	21st to end	Night	22% 19% 31% 22% 5%	836
February	1st to 10th	Night	24% 21% 31% 21% 3	760
	11th to 20th	Night	24% 23% 33% 16% 3 1	743
	21st to end	Night	28% 17% 32% 20% 2	628
March	1st to 10th	Night	29% 17% 30% 20% 3	760
	11th to 20th	Night	30% 18% 28% 19% 5%	760
	21st to end	Night	29% 17% 27% 20% 7% 1	836
April	1st to 10th	Night	32% 17% 27% 19% 5%	760
	11th to 20th	Night	31% 16% 26% 20% 7%	704
	21st to end	Night	31% 18% 26% 20% 5%	570
May	1st to 10th	Night	32% 10% 28% 24% 6% 1	565
	11th to 20th	Night	23% 12% 29% 29% 6% 1	374
	21st to end	Night	22% 9% 32% 30% 6% 1	411
June	1st to 10th	Night	33% 7% 23% 30% 7% 1	380
	11th to 20th	Night	22% 8% 23% 34% 13%	380
	21st to end	Night	19% 8% 29% 34% 9%	380
July	1st to 10th	Night	15% 7% 26% 39% 12% 1	370
	11th to 20th	Night	16% 4 27% 38% 14% 1	360
	21st to end	Night	16% 5% 25% 37% 16% 1	394
August	1st to 10th	Night	18% 4 18% 41% 19% 1	370
	11th to 20th	Night	17% 6% 21% 37% 17% 1	532
	21st to end	Night	20% 7% 21% 33% 17% 2	761
September	1st to 10th	Night	22% 7% 23% 34% 13% 1	720
	11th to 20th	Night	21% 8% 22% 29% 19% 2	720
	21st to end	Night	25% 10% 24% 24% 15% 2	720
October	1st to 10th	Night	28% 10% 24% 24% 13% 1	720
	11th to 20th	Night	29% 14% 23% 24% 8% 2	720
	21st to end	Night	35% 15% 26% 21% 4	792
November	1st to 10th	Night	34% 13% 28% 18% 7%	740
	11th to 20th	Night	28% 18% 28% 17% 8% 2	760
	21st to end	Night	34% 18% 25% 17% 5% 1	760
December	1st to 10th	Night	35% 20% 26% 15% 4	760
	11th to 20th	Night	32% 20% 26% 17% 5%	760
	21st to end	Night	36% 21% 25% 14% 3	836

Page generated at 2024-07-13 10:19:53. Version ac07

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