Observatoire de Leclercville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire de Leclercville clear sky chart from 2005-11-06 to 2024-11-28.

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	18% 10% 3 8% 5% 4 5% 4 5% 7% 31%	101519
	Night	19% 12% 4 9% 5% 4 4 3 5% 6% 29%	98023
Transparency	Day	53% 6% 13% 20% 8% 1	104979
	Night	56% 5% 12% 19% 8% 1	102640
Seeing	Day	25% 16% 30% 20% 8% 2	14985
	Night	25% 12% 30% 25% 7% 1	23725

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% 17% 5% 12% 5% 4 4 3 5% 5% 20%	2517
	11th to 20th	Day	11% 16% 7% 15% 6% 4 4 3 4 4 26%	2520
	21st to end	Day	11% 14% 6% 11% 6% 5% 4 4 5% 7% 27%	2772
February	1st to 10th	Day	12% 16% 5% 13% 7% 5% 5% 3 4 6% 24%	1548
	11th to 20th	Day	15% 17% 6% 9% 6% 5% 5% 3 4 5% 24%	1818
	21st to end	Day	15% 15% 4 11% 6% 4 4 4 4 5% 28%	1570
March	1st to 10th	Day	18% 12% 4 9% 6% 4 4 3 5% 5% 28%	3116
	11th to 20th	Day	18% 18% 6% 9% 4 4 4 3 4 5% 25%	3278
	21st to end	Day	16% 13% 4 7% 4 4 4 3 4 5% 35%	4123
April	1st to 10th	Day	23% 13% 4 8% 5% 4 4 3 4 5% 28%	2280
	11th to 20th	Day	20% 9% 3 7% 4 3 4 3 4 5% 37%	2312
	21st to end	Day	24% 9% 3 8% 4 5% 5% 3 4 6% 30%	2470
May	1st to 10th	Day	22% 8% 3 6% 4 4 4 3 6% 6% 33%	4256
	11th to 20th	Day	16% 7% 3 8% 5% 6% 6% 4 7% 9% 30%	4398
	21st to end	Day	16% 8% 3 8% 5% 5% 5% 5% 6% 7% 32%	4837
June	1st to 10th	Day	20% 8% 2 7% 6% 5% 5% 4 6% 8% 28%	2736
	11th to 20th	Day	16% 7% 3 6% 5% 4 5% 4 7% 8% 35%	2850
	21st to end	Day	22% 9% 3 8% 5% 4 5% 4 6% 5% 29%	2735
July	1st to 10th	Day	13% 7% 3 8% 6% 6% 5% 4 7% 9% 32%	4440
	11th to 20th	Day	16% 6% 2 8% 5% 5% 6% 5% 7% 8% 31%	4440
	21st to end	Day	14% 6% 2 5% 4 4 5% 4 6% 8% 41%	4814
August	1st to 10th	Day	16% 6% 3 7% 5% 5% 6% 5% 8% 10% 29%	4423
	11th to 20th	Day	19% 7% 3 8% 5% 5% 5% 4 6% 8% 31%	4058
	21st to end	Day	20% 6% 2 6% 4 4 4 4 5% 7% 39%	4254
September	1st to 10th	Day	16% 6% 2 6% 5% 4 5% 3 6% 7% 40%	2280
	11th to 20th	Day	18% 5% 2 5% 4 3 4 3 5% 8% 45%	2138
	21st to end	Day	22% 7% 2 5% 4 4 4 3 5% 5% 39%	2090
October	1st to 10th	Day	22% 9% 3 7% 4 4 6% 3 5% 7% 31%	2051
	11th to 20th	Day	22% 10% 3 9% 5% 4 5% 4 5% 6% 26%	1771
	21st to end	Day	27% 11% 4 7% 5% 4 4 3 4 6% 25%	1881
November	1st to 10th	Day	19% 12% 3 8% 5% 4 4 3 4 5% 32%	1761
	11th to 20th	Day	21% 13% 5% 10% 5% 4 4 2 5% 4 26%	1775
	21st to end	Day	24% 18% 3 7% 5% 4 5% 3 4 5% 21%	1521
December	1st to 10th	Day	26% 16% 4 11% 5% 4 3 3 3 4 21%	1330
	11th to 20th	Day	22% 14% 4 10% 5% 5% 4 3 4 5% 25%	1668
	21st to end	Day	25% 18% 4 9% 5% 4 5% 3 3 5% 21%	2688
January	1st to 10th	Night	18% 17% 6% 11% 5% 5% 4 4 4 5% 22%	4429
	11th to 20th	Night	13% 17% 5% 13% 7% 6% 5% 3 5% 4 22%	4440
	21st to end	Night	13% 15% 5% 13% 6% 5% 4 3 5% 6% 24%	4884
February	1st to 10th	Night	13% 15% 6% 13% 7% 5% 4 4 5% 4 25%	2627
	11th to 20th	Night	13% 16% 5% 12% 8% 6% 5% 4 4 3 24%	2247
	21st to end	Night	16% 14% 4 10% 5% 4 4 4 4 5% 29%	1884
March	1st to 10th	Night	24% 12% 3 7% 4 4 5% 2 4 5% 28%	3724
	11th to 20th	Night	17% 18% 6% 11% 6% 4 4 3 4 4 23%	3681
	21st to end	Night	15% 15% 4 9% 5% 3 3 3 4 4 33%	3508
April	1st to 10th	Night	24% 13% 4 7% 3 4 3 4 5% 5% 28%	1900
	11th to 20th	Night	23% 9% 2 7% 4 5% 3 3 4 6% 33%	1816
	21st to end	Night	23% 11% 3 7% 3 3 4 3 5% 6% 33%	1710
May	1st to 10th	Night	23% 9% 2 7% 5% 4 4 3 6% 6% 30%	2711
	11th to 20th	Night	22% 8% 2 6% 4 4 5% 3 5% 7% 33%	2495
	21st to end	Night	19% 7% 2 6% 4 5% 4 4 6% 9% 34%	2738
June	1st to 10th	Night	21% 9% 3 6% 4 3 4 3 7% 8% 31%	1439
	11th to 20th	Night	19% 8% 2 5% 5% 4 5% 4 6% 8% 35%	1330
	21st to end	Night	21% 9% 3 8% 4 5% 5% 5% 5% 6% 29%	1435
July	1st to 10th	Night	13% 6% 3 9% 6% 6% 5% 5% 7% 8% 30%	2520
	11th to 20th	Night	19% 6% 2 8% 4 4 4 5% 5% 8% 36%	2520
	21st to end	Night	13% 5% 3 6% 5% 5% 5% 4 5% 8% 41%	2739
August	1st to 10th	Night	17% 8% 3 8% 5% 5% 5% 4 6% 8% 31%	2506
	11th to 20th	Night	18% 8% 2 8% 5% 5% 5% 5% 6% 7% 30%	2739
	21st to end	Night	18% 7% 3 8% 5% 4 5% 4 5% 6% 36%	3401
September	1st to 10th	Night	17% 6% 3 6% 5% 4 3 3 5% 7% 42%	1900
	11th to 20th	Night	16% 6% 2 5% 4 3 4 3 4 8% 46%	2042
	21st to end	Night	19% 7% 2 6% 4 4 3 2 4 7% 41%	2090
October	1st to 10th	Night	19% 8% 3 6% 5% 4 5% 3 5% 6% 37%	2127
	11th to 20th	Night	23% 10% 3 7% 5% 5% 4 3 4 5% 31%	2408
	21st to end	Night	27% 10% 3 7% 4 4 4 3 5% 6% 29%	2717
November	1st to 10th	Night	19% 12% 3 8% 6% 4 4 2 5% 5% 31%	2537
	11th to 20th	Night	21% 12% 4 9% 4 4 4 3 4 6% 29%	2622
	21st to end	Night	23% 17% 4 9% 5% 4 4 3 4 5% 23%	2810
December	1st to 10th	Night	24% 16% 5% 10% 6% 4 4 4 4 4 19%	2850
	11th to 20th	Night	21% 17% 5% 11% 5% 4 4 3 4 4 22%	3531
	21st to end	Night	26% 19% 4 8% 4 3 3 2 3 4 23%	4966

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	68% 5% 9% 14% 4	2518
	11th to 20th	Day	64% 5% 8% 18% 5% 1	2520
	21st to end	Day	56% 6% 10% 20% 7% 1	2772
February	1st to 10th	Day	65% 4 8% 15% 7% 2	1548
	11th to 20th	Day	64% 5% 9% 13% 7% 1	1827
	21st to end	Day	60% 5% 9% 17% 7% 2	1570
March	1st to 10th	Day	59% 5% 9% 17% 8% 2	3119
	11th to 20th	Day	62% 6% 9% 14% 8% 1	3278
	21st to end	Day	52% 5% 7% 19% 13% 4	4123
April	1st to 10th	Day	60% 4 9% 15% 9% 3	2280
	11th to 20th	Day	51% 4 8% 24% 11% 2	2312
	21st to end	Day	57% 4 8% 17% 12% 2	2470
May	1st to 10th	Day	50% 5% 11% 19% 14% 1	4270
	11th to 20th	Day	49% 8% 18% 16% 8% 1	4402
	21st to end	Day	50% 7% 9% 20% 14% 1	4837
June	1st to 10th	Day	53% 6% 11% 20% 8% 1	2736
	11th to 20th	Day	46% 6% 14% 22% 12% 1	2850
	21st to end	Day	57% 6% 11% 17% 9%	2735
July	1st to 10th	Day	47% 7% 16% 24% 6%	4370
	11th to 20th	Day	46% 7% 20% 22% 5%	4365
	21st to end	Day	41% 7% 16% 28% 8%	4661
August	1st to 10th	Day	47% 8% 20% 20% 5%	4409
	11th to 20th	Day	50% 8% 19% 19% 5%	4097
	21st to end	Day	46% 6% 14% 20% 13% 1	4254
September	1st to 10th	Day	43% 5% 15% 25% 10% 1	2280
	11th to 20th	Day	39% 5% 15% 29% 11%	2138
	21st to end	Day	47% 5% 14% 26% 9%	2090
October	1st to 10th	Day	52% 6% 14% 24% 4	3402
	11th to 20th	Day	54% 6% 18% 21% 2	2922
	21st to end	Day	54% 5% 17% 18% 6%	3081
November	1st to 10th	Day	55% 4 12% 20% 8%	1761
	11th to 20th	Day	62% 4 10% 17% 7%	1775
	21st to end	Day	66% 6% 11% 13% 3	1521
December	1st to 10th	Day	69% 4 9% 14% 4	1330
	11th to 20th	Day	63% 5% 7% 18% 6%	1668
	21st to end	Day	68% 5% 9% 10% 7% 1	2688
January	1st to 10th	Night	66% 5% 12% 12% 4	4429
	11th to 20th	Night	66% 6% 9% 16% 4	4440
	21st to end	Night	62% 5% 10% 15% 7%	4884
February	1st to 10th	Night	63% 4 8% 16% 7% 1	2627
	11th to 20th	Night	64% 6% 8% 14% 8% 1	2249
	21st to end	Night	57% 5% 8% 17% 12% 2	1884
March	1st to 10th	Night	59% 3 12% 15% 8% 2	3734
	11th to 20th	Night	66% 3 7% 14% 8% 1	3682
	21st to end	Night	56% 4 7% 21% 10% 2	3508
April	1st to 10th	Night	58% 3 9% 17% 11% 2	1900
	11th to 20th	Night	53% 4 7% 22% 12% 2	1816
	21st to end	Night	53% 5% 8% 17% 14% 2	1710
May	1st to 10th	Night	54% 5% 12% 19% 9% 1	2717
	11th to 20th	Night	50% 6% 11% 20% 11% 1	2496
	21st to end	Night	46% 5% 12% 18% 18% 1	2739
June	1st to 10th	Night	50% 5% 12% 22% 10% 1	1439
	11th to 20th	Night	45% 6% 12% 21% 13% 3	1330
	21st to end	Night	54% 6% 13% 17% 10% 1	1435
July	1st to 10th	Night	48% 6% 18% 20% 7%	2480
	11th to 20th	Night	47% 6% 19% 22% 6%	2472
	21st to end	Night	40% 8% 18% 25% 9%	2651
August	1st to 10th	Night	49% 7% 16% 22% 5%	2496
	11th to 20th	Night	51% 7% 18% 18% 5%	2766
	21st to end	Night	48% 5% 12% 23% 13%	3401
September	1st to 10th	Night	43% 6% 14% 25% 12% 1	1900
	11th to 20th	Night	39% 4 18% 29% 9% 1	2042
	21st to end	Night	44% 5% 11% 27% 13%	2090
October	1st to 10th	Night	50% 5% 13% 24% 7%	3543
	11th to 20th	Night	52% 5% 15% 26% 3	3996
	21st to end	Night	50% 4 18% 18% 10%	4467
November	1st to 10th	Night	56% 5% 12% 20% 7% 1	2537
	11th to 20th	Night	58% 5% 11% 17% 8%	2622
	21st to end	Night	65% 4 10% 15% 5%	2810
December	1st to 10th	Night	70% 4 10% 13% 4	2850
	11th to 20th	Night	66% 5% 7% 15% 6%	3532
	21st to end	Night	68% 3 7% 16% 5% 1	4966

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% 19% 29% 17% 2 1	180
	11th to 20th	Day	28% 23% 34% 9% 4 1	180
	21st to end	Day	24% 22% 33% 15% 6% 1	198
February	1st to 10th	Day	25% 26% 38% 7% 3 1	193
	11th to 20th	Day	25% 23% 38% 12% 2	426
	21st to end	Day	26% 25% 28% 18% 3	382
March	1st to 10th	Day	28% 19% 29% 19% 5%	460
	11th to 20th	Day	27% 21% 30% 16% 4 2	460
	21st to end	Day	27% 20% 27% 17% 8% 2	506
April	1st to 10th	Day	30% 19% 29% 17% 5% 1	460
	11th to 20th	Day	29% 18% 27% 20% 5% 1	452
	21st to end	Day	30% 19% 32% 13% 5% 1	460
May	1st to 10th	Day	28% 20% 31% 16% 5% 1	463
	11th to 20th	Day	20% 14% 32% 23% 9% 2	487
	21st to end	Day	21% 20% 33% 17% 7% 1	529
June	1st to 10th	Day	23% 14% 33% 20% 8% 1	566
	11th to 20th	Day	21% 11% 30% 26% 11% 1	680
	21st to end	Day	25% 11% 28% 25% 9% 2	565
July	1st to 10th	Day	16% 12% 32% 28% 11% 1	485
	11th to 20th	Day	17% 13% 35% 25% 10% 1	484
	21st to end	Day	18% 9% 32% 30% 10% 1	532
August	1st to 10th	Day	20% 10% 27% 27% 12% 3	486
	11th to 20th	Day	20% 7% 25% 29% 14% 5%	479
	21st to end	Day	21% 13% 27% 18% 14% 6%	539
September	1st to 10th	Day	19% 10% 29% 27% 11% 4	490
	11th to 20th	Day	19% 10% 26% 24% 16% 5%	490
	21st to end	Day	20% 13% 26% 23% 12% 5%	490
October	1st to 10th	Day	23% 12% 29% 24% 9% 3	490
	11th to 20th	Day	29% 14% 30% 17% 9% 1	422
	21st to end	Day	33% 17% 26% 18% 5%	429
November	1st to 10th	Day	33% 14% 30% 19% 4 1	395
	11th to 20th	Day	29% 20% 27% 16% 7% 1	375
	21st to end	Day	35% 21% 28% 13% 2 1	194
December	1st to 10th	Day	36% 16% 24% 19% 4 2	180
	11th to 20th	Day	32% 22% 32% 9% 4 1	180
	21st to end	Day	35% 21% 26% 14% 5%	198
January	1st to 10th	Night	28% 14% 35% 18% 3	760
	11th to 20th	Night	28% 16% 32% 20% 4	760
	21st to end	Night	18% 12% 36% 28% 5%	836
February	1st to 10th	Night	21% 14% 36% 26% 4	760
	11th to 20th	Night	21% 19% 39% 16% 5%	743
	21st to end	Night	26% 14% 33% 22% 4	628
March	1st to 10th	Night	25% 13% 36% 22% 3	760
	11th to 20th	Night	26% 15% 34% 19% 5% 1	760
	21st to end	Night	23% 15% 31% 24% 6% 1	836
April	1st to 10th	Night	30% 14% 30% 21% 4	760
	11th to 20th	Night	27% 14% 33% 21% 4	692
	21st to end	Night	29% 16% 29% 21% 6%	570
May	1st to 10th	Night	26% 12% 29% 27% 6%	499
	11th to 20th	Night	26% 8% 31% 29% 6%	374
	21st to end	Night	25% 10% 34% 25% 6%	411
June	1st to 10th	Night	26% 6% 31% 32% 6%	380
	11th to 20th	Night	22% 7% 27% 33% 11%	380
	21st to end	Night	22% 9% 26% 31% 11%	380
July	1st to 10th	Night	16% 6% 30% 37% 11%	370
	11th to 20th	Night	17% 5% 28% 37% 12% 1	368
	21st to end	Night	16% 6% 25% 44% 10%	416
August	1st to 10th	Night	17% 3 24% 38% 17% 1	378
	11th to 20th	Night	17% 6% 24% 37% 15% 1	531
	21st to end	Night	17% 7% 29% 29% 17% 2	787
September	1st to 10th	Night	19% 7% 28% 34% 11% 2	760
	11th to 20th	Night	19% 6% 26% 30% 17% 2	760
	21st to end	Night	19% 8% 29% 28% 14% 1	760
October	1st to 10th	Night	22% 10% 29% 30% 9% 1	760
	11th to 20th	Night	26% 12% 28% 25% 7% 1	760
	21st to end	Night	32% 12% 31% 21% 5%	836
November	1st to 10th	Night	29% 14% 28% 22% 6%	780
	11th to 20th	Night	27% 15% 30% 20% 9% 1	800
	21st to end	Night	32% 15% 26% 21% 5% 1	813
December	1st to 10th	Night	32% 15% 27% 20% 6%	850
	11th to 20th	Night	27% 20% 28% 19% 6%	850
	21st to end	Night	36% 14% 29% 17% 3 1	857

Page generated at 2024-11-25 00:22:18. Version ac07

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