Observatoire Alphonse-Tardif à St-Nérée
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire Alphonse-Tardif à St-Nérée clear sky chart from 2005-11-06 to 2024-12-24.

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% 12% 4 8% 5% 5% 4 3 5% 6% 29%	101773
	Night	19% 14% 4 9% 5% 4 4 3 4 5% 28%	98325
Transparency	Day	54% 8% 13% 18% 7% 1	105246
	Night	57% 7% 12% 17% 7% 1	102943
Seeing	Day	26% 16% 30% 19% 7% 1	15503
	Night	26% 14% 30% 23% 7% 1	23992

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	13% 19% 8% 15% 8% 6% 5% 4 4 4 14%	2517
	11th to 20th	Day	12% 15% 7% 18% 11% 5% 3 2 3 3 21%	2520
	21st to end	Day	9% 12% 8% 14% 7% 5% 4 4 5% 6% 26%	2772
February	1st to 10th	Day	13% 17% 6% 12% 7% 6% 5% 3 5% 5% 21%	1549
	11th to 20th	Day	14% 18% 6% 12% 6% 5% 5% 3 3 4 24%	1810
	21st to end	Day	12% 17% 6% 11% 7% 5% 4 3 4 6% 26%	1570
March	1st to 10th	Day	17% 14% 5% 11% 6% 5% 5% 3 5% 5% 25%	3116
	11th to 20th	Day	16% 22% 5% 10% 5% 5% 3 3 4 4 23%	3352
	21st to end	Day	18% 15% 4 8% 4 4 3 3 4 5% 33%	4000
April	1st to 10th	Day	24% 15% 4 8% 4 3 4 2 4 6% 27%	2280
	11th to 20th	Day	19% 14% 3 7% 3 4 3 3 3 5% 37%	2368
	21st to end	Day	23% 12% 3 8% 4 3 4 3 4 6% 30%	2470
May	1st to 10th	Day	22% 9% 3 7% 4 4 4 3 5% 7% 32%	4137
	11th to 20th	Day	19% 9% 3 7% 6% 5% 6% 4 6% 8% 27%	4398
	21st to end	Day	19% 8% 3 8% 6% 5% 6% 4 6% 6% 29%	4983
June	1st to 10th	Day	22% 9% 3 7% 5% 5% 5% 5% 7% 7% 25%	2850
	11th to 20th	Day	20% 8% 2 6% 5% 4 5% 4 6% 7% 33%	2850
	21st to end	Day	25% 10% 3 8% 6% 5% 4 4 5% 6% 25%	2850
July	1st to 10th	Day	16% 9% 3 8% 5% 5% 5% 4 7% 7% 30%	4584
	11th to 20th	Day	19% 8% 3 7% 5% 5% 5% 5% 7% 8% 29%	4440
	21st to end	Day	15% 8% 2 6% 4 4 4 4 5% 7% 40%	4814
August	1st to 10th	Day	18% 7% 3 7% 5% 6% 6% 5% 7% 9% 28%	4343
	11th to 20th	Day	20% 8% 3 8% 6% 5% 5% 4 6% 7% 28%	4045
	21st to end	Day	21% 9% 2 7% 4 4 4 3 4 6% 36%	4386
September	1st to 10th	Day	20% 7% 2 6% 4 4 4 3 6% 7% 37%	2279
	11th to 20th	Day	21% 6% 2 4 3 3 3 3 5% 5% 45%	2090
	21st to end	Day	23% 7% 2 6% 4 4 4 3 5% 6% 37%	2090
October	1st to 10th	Day	22% 9% 3 6% 4 4 4 4 5% 6% 32%	2090
	11th to 20th	Day	24% 13% 4 7% 5% 4 4 4 4 5% 25%	1744
	21st to end	Day	28% 15% 3 7% 4 4 3 3 5% 5% 23%	1881
November	1st to 10th	Day	21% 16% 4 8% 5% 4 4 3 5% 4 27%	1761
	11th to 20th	Day	22% 18% 5% 9% 4 4 4 3 4 4 24%	1790
	21st to end	Day	23% 20% 7% 9% 4 3 3 2 3 5% 20%	1440
December	1st to 10th	Day	22% 21% 5% 11% 5% 4 3 2 5% 4 18%	1400
	11th to 20th	Day	20% 19% 5% 9% 5% 4 3 2 4 4 24%	1738
	21st to end	Day	24% 16% 5% 11% 5% 4 4 2 3 5% 20%	2466
January	1st to 10th	Night	14% 21% 8% 15% 7% 4 4 2 3 3 19%	4429
	11th to 20th	Night	12% 17% 7% 17% 8% 4 4 3 4 4 20%	4440
	21st to end	Night	10% 16% 5% 13% 7% 7% 5% 4 5% 6% 23%	4884
February	1st to 10th	Night	12% 16% 6% 13% 8% 4 5% 3 5% 4 24%	2629
	11th to 20th	Night	13% 19% 6% 13% 6% 5% 5% 2 4 4 22%	2255
	21st to end	Night	14% 17% 5% 10% 6% 4 3 3 3 5% 28%	1884
March	1st to 10th	Night	21% 15% 4 8% 4 3 6% 2 4 5% 27%	3724
	11th to 20th	Night	15% 19% 5% 12% 7% 5% 5% 3 5% 5% 22%	3593
	21st to end	Night	18% 17% 4 10% 4 3 3 3 3 5% 30%	3630
April	1st to 10th	Night	22% 17% 4 8% 4 3 3 3 3 4 28%	1900
	11th to 20th	Night	21% 12% 3 6% 4 4 5% 3 5% 7% 31%	1760
	21st to end	Night	24% 12% 4 8% 4 4 3 3 4 5% 31%	1710
May	1st to 10th	Night	24% 9% 3 6% 5% 4 4 4 5% 6% 31%	2820
	11th to 20th	Night	20% 9% 3 7% 5% 5% 5% 3 5% 7% 31%	2495
	21st to end	Night	18% 7% 2 5% 5% 4 6% 5% 6% 8% 34%	2597
June	1st to 10th	Night	22% 11% 2 7% 6% 5% 5% 4 6% 5% 26%	1330
	11th to 20th	Night	18% 9% 3 6% 4 4 4 5% 5% 7% 35%	1330
	21st to end	Night	22% 10% 3 7% 6% 4 5% 4 4 6% 29%	1330
July	1st to 10th	Night	15% 9% 4 8% 5% 5% 5% 4 6% 8% 31%	2363
	11th to 20th	Night	24% 7% 2 7% 5% 4 4 4 5% 7% 31%	2520
	21st to end	Night	15% 7% 2 6% 5% 5% 5% 4 5% 8% 38%	2739
August	1st to 10th	Night	22% 7% 2 6% 4 5% 5% 4 5% 7% 31%	2556
	11th to 20th	Night	20% 9% 3 8% 6% 6% 6% 4 6% 7% 27%	2782
	21st to end	Night	19% 9% 3 6% 4 4 4 4 5% 6% 36%	3268
September	1st to 10th	Night	20% 7% 2 7% 5% 4 4 3 5% 6% 37%	1900
	11th to 20th	Night	19% 7% 3 5% 5% 3 3 3 5% 5% 42%	2090
	21st to end	Night	21% 7% 3 6% 3 4 4 4 4 5% 39%	2090
October	1st to 10th	Night	22% 9% 3 6% 4 3 4 3 4 5% 36%	2090
	11th to 20th	Night	25% 12% 3 8% 4 4 3 3 4 5% 29%	2430
	21st to end	Night	25% 14% 3 6% 4 4 4 3 4 6% 26%	2717
November	1st to 10th	Night	21% 15% 3 9% 5% 4 4 3 4 5% 27%	2537
	11th to 20th	Night	20% 13% 5% 10% 5% 4 3 3 4 5% 28%	2609
	21st to end	Night	21% 22% 6% 9% 4 3 3 3 4 4 21%	2955
December	1st to 10th	Night	22% 20% 6% 11% 5% 4 3 2 4 4 17%	3000
	11th to 20th	Night	18% 19% 6% 11% 6% 4 3 2 4 4 22%	3681
	21st to end	Night	23% 21% 5% 9% 4 3 3 2 3 3 24%	5258

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	66% 10% 10% 11% 3	2518
	11th to 20th	Day	63% 9% 7% 15% 4 1	2520
	21st to end	Day	55% 10% 10% 17% 8%	2772
February	1st to 10th	Day	64% 5% 9% 13% 7% 1	1549
	11th to 20th	Day	64% 5% 10% 14% 7% 1	1819
	21st to end	Day	60% 5% 9% 18% 7% 2	1570
March	1st to 10th	Day	56% 9% 10% 15% 8% 2	3119
	11th to 20th	Day	60% 9% 10% 14% 6%	3352
	21st to end	Day	54% 5% 8% 19% 11% 3	4000
April	1st to 10th	Day	61% 4 10% 14% 9% 2	2280
	11th to 20th	Day	51% 5% 9% 22% 11% 2	2368
	21st to end	Day	56% 5% 9% 17% 11% 2	2470
May	1st to 10th	Day	49% 8% 12% 19% 10% 1	4151
	11th to 20th	Day	49% 12% 17% 16% 6%	4402
	21st to end	Day	50% 10% 11% 20% 10%	4983
June	1st to 10th	Day	54% 9% 13% 17% 6% 1	2850
	11th to 20th	Day	47% 9% 15% 19% 9% 1	2850
	21st to end	Day	59% 7% 11% 16% 7%	2850
July	1st to 10th	Day	50% 8% 15% 21% 6%	4514
	11th to 20th	Day	49% 8% 19% 20% 4	4365
	21st to end	Day	43% 7% 18% 24% 7%	4661
August	1st to 10th	Day	49% 9% 19% 19% 4	4329
	11th to 20th	Day	52% 10% 21% 13% 4	4084
	21st to end	Day	49% 6% 16% 18% 10% 1	4386
September	1st to 10th	Day	45% 7% 15% 22% 10% 1	2279
	11th to 20th	Day	41% 5% 16% 27% 10%	2090
	21st to end	Day	47% 6% 13% 25% 9%	2090
October	1st to 10th	Day	53% 6% 11% 24% 5%	3480
	11th to 20th	Day	55% 7% 15% 22% 1	2869
	21st to end	Day	54% 5% 16% 18% 6%	3081
November	1st to 10th	Day	59% 6% 12% 17% 6%	1761
	11th to 20th	Day	64% 5% 9% 15% 6% 1	1790
	21st to end	Day	69% 5% 11% 13% 3	1440
December	1st to 10th	Day	69% 6% 11% 11% 4	1400
	11th to 20th	Day	65% 5% 8% 17% 6%	1738
	21st to end	Day	65% 9% 9% 11% 5% 2	2466
January	1st to 10th	Night	69% 8% 8% 11% 4	4429
	11th to 20th	Night	64% 9% 9% 15% 4	4440
	21st to end	Night	59% 8% 10% 13% 9% 1	4884
February	1st to 10th	Night	62% 5% 10% 14% 8% 1	2629
	11th to 20th	Night	65% 6% 8% 14% 7% 1	2257
	21st to end	Night	59% 4 8% 16% 11% 1	1884
March	1st to 10th	Night	60% 5% 10% 15% 8% 1	3734
	11th to 20th	Night	63% 8% 12% 11% 6% 1	3594
	21st to end	Night	58% 6% 7% 19% 8% 2	3630
April	1st to 10th	Night	60% 4 9% 13% 12% 2	1900
	11th to 20th	Night	52% 6% 10% 19% 11% 2	1760
	21st to end	Night	56% 6% 7% 16% 13% 2	1710
May	1st to 10th	Night	50% 8% 13% 19% 10% 1	2826
	11th to 20th	Night	49% 10% 14% 17% 10%	2496
	21st to end	Night	43% 10% 14% 18% 13% 1	2598
June	1st to 10th	Night	55% 8% 13% 17% 7%	1330
	11th to 20th	Night	46% 9% 13% 20% 10% 3	1330
	21st to end	Night	56% 8% 11% 15% 9%	1330
July	1st to 10th	Night	50% 8% 18% 19% 6%	2324
	11th to 20th	Night	52% 7% 19% 18% 4	2472
	21st to end	Night	42% 10% 21% 20% 7%	2651
August	1st to 10th	Night	50% 7% 17% 22% 3	2546
	11th to 20th	Night	54% 10% 18% 14% 4	2809
	21st to end	Night	47% 7% 15% 19% 11% 1	3268
September	1st to 10th	Night	47% 7% 13% 22% 10% 1	1900
	11th to 20th	Night	43% 7% 17% 25% 8%	2090
	21st to end	Night	46% 7% 12% 24% 11%	2090
October	1st to 10th	Night	48% 6% 11% 27% 7%	3480
	11th to 20th	Night	57% 5% 13% 22% 3	4044
	21st to end	Night	53% 5% 17% 16% 8%	4467
November	1st to 10th	Night	59% 6% 13% 17% 5%	2537
	11th to 20th	Night	58% 7% 11% 14% 9%	2609
	21st to end	Night	67% 5% 11% 13% 5%	2955
December	1st to 10th	Night	71% 6% 10% 11% 2	3000
	11th to 20th	Night	66% 5% 8% 16% 5%	3682
	21st to end	Night	66% 5% 9% 14% 6%	5258

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	27% 24% 29% 16% 3 1	180
	11th to 20th	Day	29% 27% 33% 7% 4	180
	21st to end	Day	16% 26% 38% 16% 4 1	198
February	1st to 10th	Day	27% 25% 33% 12% 3	209
	11th to 20th	Day	24% 28% 35% 12% 1	438
	21st to end	Day	26% 22% 32% 17% 2	382
March	1st to 10th	Day	27% 22% 29% 18% 3 1	460
	11th to 20th	Day	26% 20% 32% 15% 7% 1	460
	21st to end	Day	26% 22% 26% 17% 7% 1	506
April	1st to 10th	Day	33% 19% 27% 16% 5%	460
	11th to 20th	Day	29% 20% 27% 18% 6% 1	452
	21st to end	Day	30% 20% 29% 15% 4 2	460
May	1st to 10th	Day	29% 16% 32% 16% 5% 1	463
	11th to 20th	Day	24% 12% 32% 22% 9% 1	487
	21st to end	Day	25% 15% 35% 18% 7%	610
June	1st to 10th	Day	25% 14% 32% 21% 7%	680
	11th to 20th	Day	22% 12% 29% 28% 8%	680
	21st to end	Day	29% 9% 28% 23% 10% 1	680
July	1st to 10th	Day	21% 12% 31% 26% 9%	577
	11th to 20th	Day	20% 15% 35% 20% 8% 1	484
	21st to end	Day	22% 8% 36% 24% 9% 1	532
August	1st to 10th	Day	23% 12% 28% 24% 10% 2	486
	11th to 20th	Day	20% 10% 27% 27% 13% 2	479
	21st to end	Day	22% 16% 22% 24% 12% 5%	539
September	1st to 10th	Day	23% 13% 27% 23% 10% 3	490
	11th to 20th	Day	22% 11% 29% 24% 13% 2	490
	21st to end	Day	22% 13% 29% 20% 10% 5%	490
October	1st to 10th	Day	23% 17% 28% 20% 9% 3	490
	11th to 20th	Day	33% 17% 26% 17% 7% 1	393
	21st to end	Day	37% 17% 30% 11% 4	429
November	1st to 10th	Day	33% 17% 31% 14% 3 1	395
	11th to 20th	Day	30% 19% 27% 18% 5% 1	400
	21st to end	Day	36% 19% 30% 14%	240
December	1st to 10th	Day	32% 18% 28% 18% 4 1	200
	11th to 20th	Day	32% 24% 30% 10% 3 1	200
	21st to end	Day	36% 23% 26% 13% 1	204
January	1st to 10th	Night	26% 21% 33% 18% 2	760
	11th to 20th	Night	26% 22% 32% 18% 2	760
	21st to end	Night	18% 20% 35% 23% 5%	836
February	1st to 10th	Night	19% 19% 38% 18% 5%	760
	11th to 20th	Night	24% 21% 39% 12% 4	743
	21st to end	Night	24% 20% 32% 20% 4	628
March	1st to 10th	Night	25% 15% 36% 20% 4	760
	11th to 20th	Night	24% 17% 35% 18% 5% 1	760
	21st to end	Night	25% 14% 33% 22% 7% 1	836
April	1st to 10th	Night	29% 17% 27% 21% 5%	760
	11th to 20th	Night	28% 12% 32% 22% 5% 1	636
	21st to end	Night	30% 12% 27% 23% 7%	570
May	1st to 10th	Night	28% 10% 31% 25% 7%	569
	11th to 20th	Night	25% 6% 29% 29% 9% 1	374
	21st to end	Night	25% 10% 33% 26% 6%	411
June	1st to 10th	Night	27% 6% 28% 31% 7%	380
	11th to 20th	Night	21% 5% 27% 36% 11%	380
	21st to end	Night	25% 8% 29% 30% 8%	380
July	1st to 10th	Night	19% 6% 35% 29% 10%	370
	11th to 20th	Night	19% 5% 30% 34% 11% 1	368
	21st to end	Night	16% 7% 26% 40% 10%	416
August	1st to 10th	Night	19% 4 25% 36% 15%	402
	11th to 20th	Night	21% 6% 23% 36% 12% 1	562
	21st to end	Night	20% 7% 28% 32% 12% 2	706
September	1st to 10th	Night	24% 6% 29% 28% 11% 1	760
	11th to 20th	Night	23% 7% 27% 29% 13% 1	760
	21st to end	Night	22% 11% 26% 27% 13% 1	760
October	1st to 10th	Night	25% 10% 30% 26% 8% 1	760
	11th to 20th	Night	31% 14% 27% 21% 6% 1	760
	21st to end	Night	35% 13% 30% 16% 6%	836
November	1st to 10th	Night	33% 14% 29% 20% 4	780
	11th to 20th	Night	27% 18% 27% 20% 7% 1	805
	21st to end	Night	34% 16% 31% 15% 4 1	900
December	1st to 10th	Night	32% 16% 31% 15% 6%	900
	11th to 20th	Night	26% 24% 28% 17% 5%	900
	21st to end	Night	33% 19% 28% 16% 3	944

Page generated at 2024-12-21 04:13:51. Version ac07

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