ZEC des Nymphes
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the ZEC des Nymphes clear sky chart from 2005-11-06 to 2025-08-05.

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	16% 11% 4 9% 5% 5% 5% 4 5% 7% 29%	126048
	Night	15% 11% 4 9% 5% 5% 4 4 5% 6% 31%	121997
Transparency	Day	52% 6% 11% 19% 10% 1	129480
	Night	52% 5% 12% 20% 11% 1	126652
Seeing	Day	24% 19% 32% 17% 6% 1	15417
	Night	22% 15% 31% 23% 8% 1	24306

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	10% 19% 7% 13% 5% 5% 5% 4 4 6% 22%	3597
	11th to 20th	Day	8% 15% 8% 15% 9% 6% 3 3 4 4 24%	3570
	21st to end	Day	7% 11% 8% 15% 6% 5% 5% 4 4 6% 28%	3960
February	1st to 10th	Day	9% 18% 5% 12% 8% 6% 4 3 4 5% 24%	1715
	11th to 20th	Day	11% 17% 5% 12% 6% 5% 5% 3 5% 5% 27%	1847
	21st to end	Day	14% 18% 6% 10% 6% 5% 5% 3 4 5% 25%	1650
March	1st to 10th	Day	16% 19% 5% 11% 7% 5% 4 3 3 4 22%	4476
	11th to 20th	Day	11% 14% 5% 11% 5% 4 5% 4 5% 6% 30%	4675
	21st to end	Day	15% 16% 4 8% 4 4 4 3 4 5% 33%	5970
April	1st to 10th	Day	18% 15% 4 9% 5% 4 4 3 4 6% 29%	2400
	11th to 20th	Day	22% 10% 3 7% 5% 4 4 3 5% 5% 33%	2374
	21st to end	Day	20% 12% 4 8% 5% 4 4 4 5% 5% 29%	2590
May	1st to 10th	Day	25% 11% 4 8% 5% 4 5% 3 5% 6% 25%	6316
	11th to 20th	Day	21% 9% 3 8% 5% 4 4 3 6% 7% 30%	6318
	21st to end	Day	22% 10% 3 8% 6% 6% 5% 4 4 6% 27%	6949
June	1st to 10th	Day	20% 9% 3 8% 6% 5% 5% 4 5% 7% 27%	2800
	11th to 20th	Day	15% 7% 3 7% 6% 5% 5% 4 7% 9% 31%	2800
	21st to end	Day	23% 9% 3 8% 7% 5% 5% 4 5% 7% 25%	2800
July	1st to 10th	Day	16% 8% 3 8% 6% 6% 6% 5% 7% 8% 28%	6360
	11th to 20th	Day	13% 6% 2 6% 5% 6% 6% 5% 8% 9% 34%	6360
	21st to end	Day	10% 5% 2 7% 4 5% 6% 4 8% 9% 40%	6926
August	1st to 10th	Day	14% 5% 3 7% 5% 7% 7% 5% 8% 8% 30%	4479
	11th to 20th	Day	16% 7% 3 7% 5% 5% 6% 5% 7% 9% 31%	4089
	21st to end	Day	15% 7% 3 7% 5% 4 5% 4 7% 8% 35%	4180
September	1st to 10th	Day	15% 5% 2 6% 5% 5% 5% 4 5% 9% 40%	2280
	11th to 20th	Day	14% 6% 2 6% 5% 4 5% 4 5% 6% 44%	2195
	21st to end	Day	20% 8% 3 5% 4 4 5% 3 4 7% 38%	2090
October	1st to 10th	Day	22% 9% 3 6% 4 5% 4 4 5% 7% 31%	1965
	11th to 20th	Day	21% 11% 4 9% 5% 5% 5% 3 5% 5% 25%	1837
	21st to end	Day	24% 12% 3 7% 4 5% 4 4 5% 6% 26%	1881
November	1st to 10th	Day	16% 13% 4 8% 6% 5% 4 4 5% 5% 31%	1761
	11th to 20th	Day	18% 13% 4 9% 5% 4 5% 4 5% 6% 26%	1692
	21st to end	Day	19% 17% 5% 8% 5% 5% 6% 3 4 6% 23%	1600
December	1st to 10th	Day	19% 17% 7% 13% 5% 4 4 4 4 4 19%	2600
	11th to 20th	Day	17% 14% 6% 11% 5% 4 4 3 4 6% 26%	2986
	21st to end	Day	17% 16% 5% 11% 6% 4 4 3 4 5% 26%	3960
January	1st to 10th	Night	11% 18% 9% 15% 6% 4 4 3 5% 6% 19%	6349
	11th to 20th	Night	7% 14% 8% 17% 8% 6% 4 3 4 5% 23%	6315
	21st to end	Night	7% 11% 7% 15% 8% 7% 6% 4 5% 6% 25%	6996
February	1st to 10th	Night	10% 13% 5% 11% 6% 7% 5% 4 5% 6% 27%	2680
	11th to 20th	Night	10% 14% 5% 11% 6% 6% 4 4 5% 6% 28%	2439
	21st to end	Night	12% 13% 4 9% 6% 5% 5% 4 5% 6% 31%	1980
March	1st to 10th	Night	19% 16% 5% 11% 5% 4 5% 3 4 5% 23%	5364
	11th to 20th	Night	10% 14% 5% 10% 6% 5% 5% 4 6% 7% 28%	5255
	21st to end	Night	14% 10% 5% 11% 5% 4 5% 4 5% 6% 31%	4962
April	1st to 10th	Night	20% 13% 3 8% 4 5% 5% 3 5% 5% 30%	2000
	11th to 20th	Night	17% 7% 3 8% 5% 4 4 4 5% 7% 36%	1975
	21st to end	Night	20% 10% 3 6% 4 3 4 3 5% 5% 35%	1810
May	1st to 10th	Night	23% 11% 3 7% 6% 5% 5% 3 5% 7% 27%	3654
	11th to 20th	Night	23% 9% 2 6% 4 4 4 3 5% 7% 34%	3575
	21st to end	Night	21% 9% 3 8% 6% 4 4 4 5% 7% 28%	3926
June	1st to 10th	Night	19% 8% 3 6% 5% 4 5% 4 5% 8% 34%	1600
	11th to 20th	Night	17% 8% 3 6% 4 5% 4 5% 6% 7% 36%	1600
	21st to end	Night	19% 8% 3 5% 5% 5% 5% 4 5% 7% 34%	1600
July	1st to 10th	Night	13% 5% 2 7% 5% 5% 7% 5% 8% 9% 34%	3600
	11th to 20th	Night	13% 5% 2 6% 4 4 5% 4 5% 8% 43%	3600
	21st to end	Night	9% 4 2 5% 3 4 4 4 7% 8% 48%	3926
August	1st to 10th	Night	12% 6% 2 7% 5% 5% 5% 5% 6% 8% 38%	2538
	11th to 20th	Night	16% 7% 2 6% 4 4 4 3 5% 7% 41%	2705
	21st to end	Night	17% 8% 3 6% 3 4 4 4 5% 7% 40%	3476
September	1st to 10th	Night	12% 6% 2 6% 4 5% 4 3 5% 7% 46%	1900
	11th to 20th	Night	15% 5% 1 5% 3 3 3 4 6% 6% 49%	1984
	21st to end	Night	17% 7% 2 5% 4 3 3 3 5% 7% 44%	2090
October	1st to 10th	Night	16% 10% 2 6% 5% 4 4 3 5% 5% 40%	2213
	11th to 20th	Night	20% 9% 3 8% 5% 4 4 3 6% 7% 32%	2342
	21st to end	Night	22% 9% 4 8% 5% 5% 4 3 5% 7% 28%	2717
November	1st to 10th	Night	16% 10% 4 7% 5% 4 5% 4 5% 6% 32%	2537
	11th to 20th	Night	17% 11% 4 8% 5% 5% 5% 3 5% 6% 30%	2705
	21st to end	Night	19% 15% 4 9% 5% 4 3 3 4 6% 27%	2800
December	1st to 10th	Night	14% 15% 5% 11% 6% 5% 5% 4 7% 7% 20%	4580
	11th to 20th	Night	21% 14% 4 10% 5% 5% 5% 3 4 4 25%	5208
	21st to end	Night	18% 16% 7% 11% 5% 4 3 2 3 4 27%	6996

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	62% 5% 9% 17% 6%	3598
	11th to 20th	Day	62% 4 8% 15% 8% 2	3600
	21st to end	Day	55% 5% 7% 17% 15% 1	3960
February	1st to 10th	Day	61% 3 6% 17% 10% 3	1715
	11th to 20th	Day	59% 4 10% 14% 12% 1	1856
	21st to end	Day	60% 4 7% 16% 10% 3	1650
March	1st to 10th	Day	65% 5% 5% 10% 11% 4	4479
	11th to 20th	Day	52% 5% 15% 13% 13% 3	4675
	21st to end	Day	53% 3 7% 15% 18% 3	5970
April	1st to 10th	Day	56% 5% 8% 16% 13% 3	2400
	11th to 20th	Day	51% 4 8% 21% 13% 3	2374
	21st to end	Day	55% 6% 8% 16% 13% 3	2590
May	1st to 10th	Day	58% 5% 8% 16% 11% 1	6327
	11th to 20th	Day	50% 7% 15% 18% 8% 2	6322
	21st to end	Day	55% 7% 9% 15% 13% 2	6949
June	1st to 10th	Day	54% 8% 8% 18% 10% 1	2800
	11th to 20th	Day	46% 8% 12% 21% 11% 2	2800
	21st to end	Day	57% 7% 10% 16% 9% 1	2800
July	1st to 10th	Day	50% 7% 12% 24% 7%	6290
	11th to 20th	Day	41% 7% 16% 28% 7%	6285
	21st to end	Day	36% 7% 16% 30% 10%	6728
August	1st to 10th	Day	47% 8% 16% 22% 7%	4465
	11th to 20th	Day	45% 10% 16% 24% 5%	4131
	21st to end	Day	44% 7% 13% 21% 14% 1	4180
September	1st to 10th	Day	40% 6% 16% 26% 12% 1	2280
	11th to 20th	Day	38% 7% 13% 29% 11% 1	2195
	21st to end	Day	45% 5% 12% 26% 11%	2090
October	1st to 10th	Day	48% 6% 13% 26% 7% 1	3264
	11th to 20th	Day	48% 7% 13% 25% 7% 1	3027
	21st to end	Day	45% 5% 21% 19% 9% 1	3081
November	1st to 10th	Day	51% 6% 13% 20% 9% 1	1761
	11th to 20th	Day	55% 5% 10% 17% 12% 1	1692
	21st to end	Day	61% 6% 11% 15% 6% 1	1600
December	1st to 10th	Day	67% 4 8% 16% 5%	2600
	11th to 20th	Day	58% 3 6% 19% 14%	2986
	21st to end	Day	61% 4 7% 15% 13%	3960
January	1st to 10th	Night	64% 5% 10% 15% 6%	6349
	11th to 20th	Night	63% 4 10% 17% 5% 1	6360
	21st to end	Night	57% 5% 8% 14% 16% 1	6996
February	1st to 10th	Night	56% 5% 9% 18% 11% 2	2680
	11th to 20th	Night	55% 5% 9% 17% 12% 1	2441
	21st to end	Night	52% 5% 8% 19% 13% 2	1980
March	1st to 10th	Night	63% 5% 8% 10% 11% 3	5374
	11th to 20th	Night	52% 5% 12% 15% 12% 3	5256
	21st to end	Night	52% 4 7% 22% 13% 3	4962
April	1st to 10th	Night	54% 5% 7% 16% 15% 2	2000
	11th to 20th	Night	46% 6% 10% 22% 14% 2	1975
	21st to end	Night	50% 4 8% 21% 15% 2	1810
May	1st to 10th	Night	56% 6% 11% 16% 9% 2	3660
	11th to 20th	Night	49% 7% 13% 20% 9% 2	3576
	21st to end	Night	54% 6% 12% 16% 12% 1	3927
June	1st to 10th	Night	46% 7% 12% 21% 13% 1	1600
	11th to 20th	Night	45% 7% 12% 20% 13% 3	1600
	21st to end	Night	48% 8% 12% 19% 13% 1	1600
July	1st to 10th	Night	42% 7% 22% 22% 7% 1	3560
	11th to 20th	Night	38% 7% 19% 30% 7%	3552
	21st to end	Night	33% 7% 17% 32% 11%	3809
August	1st to 10th	Night	41% 7% 17% 26% 8%	2528
	11th to 20th	Night	41% 6% 21% 25% 7%	2729
	21st to end	Night	43% 6% 15% 24% 12%	3476
September	1st to 10th	Night	35% 6% 16% 28% 14% 1	1900
	11th to 20th	Night	35% 4 17% 32% 11% 1	1984
	21st to end	Night	40% 6% 11% 30% 13%	2090
October	1st to 10th	Night	46% 5% 13% 26% 10%	3694
	11th to 20th	Night	42% 6% 12% 31% 9%	3891
	21st to end	Night	46% 4 17% 19% 12% 2	4467
November	1st to 10th	Night	50% 5% 13% 22% 9% 1	2537
	11th to 20th	Night	52% 6% 11% 19% 11% 1	2705
	21st to end	Night	59% 5% 10% 17% 9% 1	2800
December	1st to 10th	Night	60% 5% 14% 16% 5%	4580
	11th to 20th	Night	61% 4 6% 17% 12% 1	5208
	21st to end	Night	61% 4 5% 15% 14% 1	6996

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	24% 19% 41% 13% 4	200
	11th to 20th	Day	27% 18% 40% 11% 5% 1	200
	21st to end	Day	17% 23% 42% 14% 3 1	220
February	1st to 10th	Day	32% 26% 34% 6% 2	257
	11th to 20th	Day	24% 30% 35% 10% 1	394
	21st to end	Day	27% 25% 31% 13% 3	414
March	1st to 10th	Day	25% 24% 32% 15% 3	500
	11th to 20th	Day	26% 26% 33% 12% 3	500
	21st to end	Day	29% 26% 25% 13% 6% 1	550
April	1st to 10th	Day	32% 20% 29% 13% 5%	500
	11th to 20th	Day	36% 20% 24% 12% 8% 1	492
	21st to end	Day	33% 21% 32% 10% 4 1	500
May	1st to 10th	Day	30% 20% 33% 12% 3 1	503
	11th to 20th	Day	24% 20% 33% 17% 5% 1	527
	21st to end	Day	26% 22% 32% 14% 4 1	573
June	1st to 10th	Day	24% 17% 41% 13% 6%	530
	11th to 20th	Day	21% 20% 32% 17% 9% 1	530
	21st to end	Day	28% 15% 32% 17% 6% 1	530
July	1st to 10th	Day	16% 13% 39% 24% 7% 2	525
	11th to 20th	Day	15% 15% 39% 26% 4 1	524
	21st to end	Day	14% 12% 35% 27% 9% 2	576
August	1st to 10th	Day	16% 12% 35% 26% 10% 2	502
	11th to 20th	Day	16% 10% 32% 25% 12% 5%	479
	21st to end	Day	17% 18% 27% 20% 14% 4	539
September	1st to 10th	Day	19% 12% 33% 21% 10% 4	490
	11th to 20th	Day	16% 11% 30% 24% 13% 6%	490
	21st to end	Day	22% 17% 28% 18% 11% 4	490
October	1st to 10th	Day	27% 17% 24% 20% 9% 2	490
	11th to 20th	Day	27% 22% 27% 16% 7% 1	456
	21st to end	Day	32% 19% 29% 16% 3	429
November	1st to 10th	Day	30% 20% 27% 18% 5% 1	395
	11th to 20th	Day	28% 20% 34% 15% 3	292
	21st to end	Day	29% 27% 32% 11% 2 1	200
December	1st to 10th	Day	30% 18% 32% 14% 7% 1	200
	11th to 20th	Day	32% 26% 30% 11% 3	200
	21st to end	Day	30% 22% 30% 11% 5% 1	220
January	1st to 10th	Night	24% 18% 37% 17% 4	800
	11th to 20th	Night	21% 20% 34% 20% 5%	800
	21st to end	Night	15% 18% 38% 24% 5%	880
February	1st to 10th	Night	18% 21% 36% 21% 5%	800
	11th to 20th	Night	20% 23% 36% 18% 3 1	783
	21st to end	Night	21% 20% 34% 22% 3	660
March	1st to 10th	Night	26% 17% 33% 20% 4	800
	11th to 20th	Night	24% 23% 30% 17% 5% 1	800
	21st to end	Night	22% 18% 31% 23% 5% 1	880
April	1st to 10th	Night	30% 16% 28% 22% 5%	800
	11th to 20th	Night	24% 17% 32% 21% 6%	791
	21st to end	Night	28% 19% 29% 19% 5%	610
May	1st to 10th	Night	27% 16% 29% 20% 7% 1	434
	11th to 20th	Night	24% 12% 30% 26% 8%	394
	21st to end	Night	21% 12% 39% 20% 7%	433
June	1st to 10th	Night	22% 10% 33% 28% 7%	400
	11th to 20th	Night	19% 12% 27% 32% 10% 1	400
	21st to end	Night	23% 7% 29% 31% 10% 1	400
July	1st to 10th	Night	14% 6% 35% 35% 11% 1	390
	11th to 20th	Night	14% 5% 27% 40% 13% 1	388
	21st to end	Night	13% 8% 29% 37% 13%	438
August	1st to 10th	Night	11% 5% 23% 43% 17% 1	386
	11th to 20th	Night	15% 5% 24% 34% 19% 2	507
	21st to end	Night	16% 10% 28% 29% 15% 2	836
September	1st to 10th	Night	15% 10% 30% 34% 11% 1	760
	11th to 20th	Night	18% 8% 28% 27% 18% 2	760
	21st to end	Night	22% 10% 29% 23% 14% 2	760
October	1st to 10th	Night	21% 15% 28% 24% 10% 1	760
	11th to 20th	Night	28% 14% 29% 22% 8%	760
	21st to end	Night	28% 17% 29% 21% 5%	836
November	1st to 10th	Night	23% 19% 27% 23% 6% 1	780
	11th to 20th	Night	25% 17% 30% 19% 8% 1	800
	21st to end	Night	28% 21% 25% 20% 5% 1	800
December	1st to 10th	Night	27% 17% 30% 21% 5%	800
	11th to 20th	Night	28% 18% 32% 16% 6% 1	800
	21st to end	Night	30% 19% 28% 19% 4	880

Page generated at 2025-08-02 01:32:29. Version ac07

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