Trois-Pistoles
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Trois-Pistoles clear sky chart from 2005-11-06 to 2024-12-06.

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% 10% 3 8% 5% 5% 5% 4 6% 7% 31%	101932
	Night	17% 13% 4 10% 6% 5% 5% 4 5% 6% 26%	97855
Transparency	Day	53% 7% 14% 19% 7% 1	105380
	Night	58% 7% 12% 16% 6%	102497
Seeing	Day	27% 17% 30% 18% 7% 1	15871
	Night	26% 15% 29% 21% 7% 1	23953

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% 18% 6% 11% 9% 7% 7% 5% 6% 7% 9%	2207
	11th to 20th	Day	11% 14% 6% 15% 10% 7% 6% 6% 6% 6% 13%	2520
	21st to end	Day	6% 11% 4 11% 9% 8% 7% 6% 5% 7% 24%	2772
February	1st to 10th	Day	9% 14% 6% 10% 9% 9% 6% 5% 6% 7% 19%	1585
	11th to 20th	Day	15% 12% 6% 14% 7% 5% 5% 5% 5% 5% 21%	1705
	21st to end	Day	11% 11% 4 9% 7% 8% 7% 5% 5% 7% 25%	1570
March	1st to 10th	Day	14% 12% 3 9% 5% 6% 6% 5% 6% 7% 27%	3116
	11th to 20th	Day	18% 22% 4 8% 5% 5% 4 3 4 5% 20%	3445
	21st to end	Day	18% 16% 5% 9% 5% 3 3 3 4 6% 28%	3873
April	1st to 10th	Day	21% 11% 3 8% 5% 4 5% 3 5% 6% 29%	2287
	11th to 20th	Day	18% 11% 2 6% 4 4 4 3 5% 6% 37%	2442
	21st to end	Day	22% 10% 3 6% 4 4 3 4 5% 6% 34%	2470
May	1st to 10th	Day	16% 8% 3 8% 5% 4 4 4 5% 6% 38%	4106
	11th to 20th	Day	17% 9% 3 7% 4 4 4 3 6% 8% 34%	4532
	21st to end	Day	19% 8% 3 8% 5% 5% 5% 4 5% 7% 31%	5185
June	1st to 10th	Day	18% 9% 3 7% 5% 4 5% 4 6% 6% 33%	2850
	11th to 20th	Day	18% 6% 2 6% 5% 4 5% 3 6% 7% 37%	2850
	21st to end	Day	20% 8% 3 8% 6% 4 5% 4 6% 7% 30%	2850
July	1st to 10th	Day	16% 8% 2 8% 5% 4 4 4 7% 9% 34%	4760
	11th to 20th	Day	13% 6% 2 7% 5% 5% 5% 5% 7% 8% 36%	4678
	21st to end	Day	12% 6% 2 6% 4 4 5% 4 5% 8% 43%	4814
August	1st to 10th	Day	13% 5% 2 6% 5% 5% 6% 4 7% 10% 37%	4302
	11th to 20th	Day	17% 7% 3 9% 5% 5% 5% 4 7% 8% 31%	4045
	21st to end	Day	17% 6% 2 7% 4 5% 4 4 5% 9% 38%	4532
September	1st to 10th	Day	17% 6% 2 6% 4 3 4 3 6% 8% 42%	2267
	11th to 20th	Day	17% 6% 2 5% 4 3 3 2 5% 6% 47%	2090
	21st to end	Day	17% 6% 2 7% 4 4 3 3 5% 6% 42%	2090
October	1st to 10th	Day	17% 9% 2 6% 4 4 5% 4 6% 7% 36%	2024
	11th to 20th	Day	24% 8% 3 7% 5% 6% 5% 3 5% 6% 29%	1799
	21st to end	Day	26% 12% 4 7% 4 3 5% 3 4 5% 28%	1881
November	1st to 10th	Day	19% 13% 3 9% 5% 4 4 4 6% 5% 28%	1761
	11th to 20th	Day	21% 13% 4 10% 5% 5% 5% 4 6% 7% 22%	1600
	21st to end	Day	20% 18% 5% 9% 6% 4 4 2 5% 6% 21%	1460
December	1st to 10th	Day	16% 19% 6% 13% 9% 6% 5% 3 4 5% 14%	1365
	11th to 20th	Day	15% 17% 5% 13% 9% 6% 5% 4 4 5% 17%	1668
	21st to end	Day	20% 14% 4 10% 5% 5% 5% 3 6% 7% 21%	2431
January	1st to 10th	Night	12% 18% 7% 17% 10% 8% 6% 3 4 5% 10%	4744
	11th to 20th	Night	12% 17% 7% 15% 7% 6% 5% 4 5% 7% 15%	4440
	21st to end	Night	7% 14% 6% 13% 7% 6% 7% 4 5% 7% 24%	4884
February	1st to 10th	Night	10% 14% 5% 12% 9% 7% 6% 5% 5% 6% 21%	2594
	11th to 20th	Night	13% 17% 7% 13% 7% 6% 6% 4 5% 5% 19%	2357
	21st to end	Night	12% 16% 5% 11% 7% 5% 4 3 5% 5% 26%	1884
March	1st to 10th	Night	16% 14% 4 10% 7% 6% 6% 4 4 6% 23%	3724
	11th to 20th	Night	20% 26% 4 9% 5% 3 4 2 4 4 17%	3512
	21st to end	Night	21% 17% 4 7% 3 3 3 3 3 5% 28%	3754
April	1st to 10th	Night	23% 15% 4 9% 5% 4 3 3 3 3 27%	1892
	11th to 20th	Night	20% 11% 2 6% 5% 5% 4 3 5% 6% 31%	1688
	21st to end	Night	24% 12% 4 7% 4 3 3 3 4 5% 32%	1710
May	1st to 10th	Night	21% 7% 3 6% 4 4 5% 4 6% 6% 34%	2834
	11th to 20th	Night	19% 9% 3 7% 4 4 4 4 7% 7% 31%	2393
	21st to end	Night	19% 8% 3 7% 4 5% 6% 5% 8% 8% 29%	2401
June	1st to 10th	Night	20% 9% 3 7% 7% 4 5% 4 5% 6% 29%	1330
	11th to 20th	Night	17% 8% 2 7% 5% 4 4 5% 6% 7% 34%	1330
	21st to end	Night	21% 9% 3 8% 5% 6% 4 4 5% 6% 28%	1330
July	1st to 10th	Night	17% 6% 3 8% 5% 5% 6% 4 6% 7% 32%	2210
	11th to 20th	Night	15% 6% 3 8% 6% 5% 5% 4 7% 9% 32%	2287
	21st to end	Night	11% 7% 2 8% 4 4 4 4 5% 8% 42%	2739
August	1st to 10th	Night	17% 6% 3 7% 6% 6% 5% 4 6% 8% 33%	2597
	11th to 20th	Night	16% 8% 4 10% 6% 5% 6% 5% 6% 7% 26%	2782
	21st to end	Night	20% 6% 3 6% 3 4 4 3 4 6% 41%	3124
September	1st to 10th	Night	16% 7% 2 8% 4 5% 5% 3 5% 7% 37%	1909
	11th to 20th	Night	20% 6% 3 7% 4 4 4 4 4 5% 39%	2090
	21st to end	Night	18% 7% 2 7% 4 5% 4 3 4 6% 41%	2090
October	1st to 10th	Night	19% 8% 2 6% 4 4 4 3 4 6% 40%	2156
	11th to 20th	Night	25% 10% 3 8% 4 4 5% 3 4 5% 29%	2380
	21st to end	Night	24% 11% 4 8% 4 4 4 3 5% 6% 27%	2717
November	1st to 10th	Night	21% 13% 3 8% 5% 4 4 3 5% 5% 28%	2537
	11th to 20th	Night	21% 15% 5% 8% 5% 5% 4 3 4 5% 25%	2798
	21st to end	Night	20% 18% 6% 11% 6% 4 4 3 5% 4 19%	2939
December	1st to 10th	Night	19% 17% 6% 12% 7% 5% 5% 4 4 5% 16%	2932
	11th to 20th	Night	17% 17% 5% 13% 9% 7% 5% 4 4 5% 14%	3531
	21st to end	Night	16% 18% 5% 11% 6% 5% 5% 3 5% 5% 20%	5236

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	79% 6% 8% 6% 1	2208
	11th to 20th	Day	67% 7% 14% 8% 4	2520
	21st to end	Day	55% 8% 12% 18% 7%	2772
February	1st to 10th	Day	64% 6% 12% 11% 6% 1	1585
	11th to 20th	Day	65% 7% 10% 13% 5%	1713
	21st to end	Day	59% 6% 8% 18% 8% 1	1570
March	1st to 10th	Day	55% 8% 15% 15% 5% 2	3119
	11th to 20th	Day	67% 5% 11% 12% 5%	3445
	21st to end	Day	59% 4 8% 20% 7% 2	3873
April	1st to 10th	Day	57% 4 11% 17% 8% 2	2287
	11th to 20th	Day	50% 5% 11% 22% 11% 1	2442
	21st to end	Day	53% 5% 7% 20% 13% 2	2470
May	1st to 10th	Day	48% 7% 13% 21% 10% 1	4120
	11th to 20th	Day	49% 7% 13% 22% 8%	4536
	21st to end	Day	48% 8% 11% 24% 9%	5185
June	1st to 10th	Day	50% 6% 11% 20% 11% 1	2850
	11th to 20th	Day	46% 7% 14% 20% 11% 1	2850
	21st to end	Day	54% 6% 12% 20% 8%	2850
July	1st to 10th	Day	46% 7% 15% 25% 6%	4685
	11th to 20th	Day	43% 8% 22% 21% 5%	4597
	21st to end	Day	39% 8% 20% 25% 8%	4661
August	1st to 10th	Day	41% 9% 21% 23% 6%	4288
	11th to 20th	Day	48% 10% 21% 18% 4	4084
	21st to end	Day	45% 7% 18% 19% 12%	4532
September	1st to 10th	Day	41% 6% 16% 27% 10%	2267
	11th to 20th	Day	39% 6% 17% 27% 10% 1	2090
	21st to end	Day	45% 5% 15% 25% 9%	2090
October	1st to 10th	Day	55% 6% 13% 19% 7%	3362
	11th to 20th	Day	55% 6% 16% 21% 3	2963
	21st to end	Day	54% 5% 17% 18% 6%	3081
November	1st to 10th	Day	58% 7% 12% 18% 4	1761
	11th to 20th	Day	64% 7% 11% 14% 4	1600
	21st to end	Day	68% 6% 12% 12% 3	1460
December	1st to 10th	Day	76% 5% 10% 8% 2	1365
	11th to 20th	Day	72% 6% 8% 11% 3	1668
	21st to end	Day	66% 8% 12% 10% 4 1	2431
January	1st to 10th	Night	78% 6% 8% 6% 1	4744
	11th to 20th	Night	66% 7% 12% 11% 4	4440
	21st to end	Night	58% 7% 11% 17% 7%	4884
February	1st to 10th	Night	62% 6% 10% 13% 8% 1	2594
	11th to 20th	Night	67% 6% 9% 13% 5%	2360
	21st to end	Night	60% 5% 10% 18% 7%	1884
March	1st to 10th	Night	61% 7% 10% 16% 7%	3734
	11th to 20th	Night	71% 5% 9% 10% 5%	3513
	21st to end	Night	61% 4 7% 21% 7% 1	3754
April	1st to 10th	Night	63% 4 7% 13% 11% 2	1892
	11th to 20th	Night	52% 7% 9% 17% 13% 1	1688
	21st to end	Night	55% 5% 7% 20% 12% 2	1710
May	1st to 10th	Night	48% 8% 12% 18% 12% 1	2840
	11th to 20th	Night	49% 8% 11% 21% 10% 1	2394
	21st to end	Night	49% 8% 10% 22% 10% 1	2402
June	1st to 10th	Night	53% 8% 9% 19% 9% 1	1330
	11th to 20th	Night	47% 6% 12% 18% 14% 2	1330
	21st to end	Night	55% 7% 12% 16% 9%	1330
July	1st to 10th	Night	48% 9% 14% 25% 5%	2175
	11th to 20th	Night	46% 9% 23% 18% 4	2245
	21st to end	Night	40% 8% 22% 22% 7%	2651
August	1st to 10th	Night	48% 8% 17% 21% 5%	2587
	11th to 20th	Night	53% 12% 18% 12% 4	2809
	21st to end	Night	44% 6% 15% 24% 11%	3124
September	1st to 10th	Night	45% 7% 13% 24% 10% 1	1909
	11th to 20th	Night	47% 6% 16% 22% 9% 1	2090
	21st to end	Night	45% 6% 12% 24% 11% 1	2090
October	1st to 10th	Night	48% 6% 12% 26% 9% 1	3598
	11th to 20th	Night	56% 5% 13% 23% 3	3955
	21st to end	Night	56% 7% 16% 17% 4	4467
November	1st to 10th	Night	59% 7% 11% 16% 6%	2537
	11th to 20th	Night	64% 5% 11% 14% 6%	2798
	21st to end	Night	71% 6% 11% 9% 3	2939
December	1st to 10th	Night	73% 7% 9% 8% 2	2932
	11th to 20th	Night	72% 8% 9% 9% 2	3532
	21st to end	Night	69% 6% 11% 11% 4	5236

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	28% 28% 29% 11% 4 1	180
	11th to 20th	Day	29% 23% 33% 11% 3	180
	21st to end	Day	19% 24% 32% 18% 6% 1	198
February	1st to 10th	Day	27% 22% 34% 13% 4 1	245
	11th to 20th	Day	25% 25% 35% 13% 2 1	386
	21st to end	Day	25% 26% 29% 13% 5% 2	382
March	1st to 10th	Day	25% 22% 30% 20% 2 1	460
	11th to 20th	Day	30% 20% 27% 14% 8% 1	460
	21st to end	Day	33% 19% 30% 13% 4 1	506
April	1st to 10th	Day	34% 19% 27% 15% 5% 1	460
	11th to 20th	Day	30% 16% 31% 15% 6% 1	452
	21st to end	Day	28% 18% 35% 13% 4 2	460
May	1st to 10th	Day	33% 14% 29% 16% 7% 1	463
	11th to 20th	Day	27% 16% 29% 20% 7% 2	566
	21st to end	Day	29% 17% 32% 16% 6% 1	735
June	1st to 10th	Day	26% 14% 30% 22% 7% 1	680
	11th to 20th	Day	25% 14% 29% 21% 10% 1	680
	21st to end	Day	24% 12% 32% 23% 8% 1	680
July	1st to 10th	Day	21% 12% 31% 26% 9%	670
	11th to 20th	Day	15% 12% 36% 26% 9% 2	625
	21st to end	Day	19% 12% 34% 27% 7% 1	532
August	1st to 10th	Day	19% 13% 32% 25% 9% 2	486
	11th to 20th	Day	19% 8% 32% 30% 9% 1	479
	21st to end	Day	21% 14% 30% 21% 12% 2	539
September	1st to 10th	Day	24% 13% 31% 20% 10% 3	490
	11th to 20th	Day	23% 12% 32% 21% 10% 2	490
	21st to end	Day	25% 14% 29% 20% 9% 3	490
October	1st to 10th	Day	25% 17% 29% 19% 8% 3	455
	11th to 20th	Day	36% 18% 23% 14% 8% 1	390
	21st to end	Day	35% 20% 25% 11% 7% 1	429
November	1st to 10th	Day	36% 22% 25% 14% 2 1	395
	11th to 20th	Day	35% 18% 26% 14% 6% 1	400
	21st to end	Day	33% 25% 28% 10% 3	260
December	1st to 10th	Day	32% 19% 28% 15% 4 2	190
	11th to 20th	Day	31% 26% 34% 7% 2	180
	21st to end	Day	33% 28% 25% 11% 3	198
January	1st to 10th	Night	26% 22% 33% 15% 4	848
	11th to 20th	Night	27% 25% 28% 17% 3 1	760
	21st to end	Night	16% 19% 38% 21% 6%	836
February	1st to 10th	Night	18% 25% 35% 15% 6% 1	760
	11th to 20th	Night	24% 24% 31% 17% 4	743
	21st to end	Night	24% 18% 35% 17% 6% 1	628
March	1st to 10th	Night	24% 18% 34% 19% 5% 1	760
	11th to 20th	Night	27% 17% 31% 14% 9% 1	760
	21st to end	Night	28% 18% 29% 19% 5% 1	836
April	1st to 10th	Night	33% 14% 28% 17% 7% 1	752
	11th to 20th	Night	29% 12% 29% 22% 8%	564
	21st to end	Night	31% 12% 29% 21% 7% 1	570
May	1st to 10th	Night	30% 8% 27% 27% 7% 1	570
	11th to 20th	Night	26% 9% 29% 25% 11%	401
	21st to end	Night	28% 12% 27% 24% 7% 1	411
June	1st to 10th	Night	21% 6% 30% 34% 9% 1	380
	11th to 20th	Night	22% 9% 23% 33% 11% 2	380
	21st to end	Night	23% 8% 31% 27% 10% 1	380
July	1st to 10th	Night	18% 9% 32% 31% 8% 2	370
	11th to 20th	Night	14% 11% 30% 35% 10% 1	368
	21st to end	Night	18% 4 29% 35% 13% 1	416
August	1st to 10th	Night	17% 6% 28% 33% 15%	430
	11th to 20th	Night	19% 7% 29% 32% 13% 1	562
	21st to end	Night	20% 9% 28% 29% 12% 2	627
September	1st to 10th	Night	21% 10% 30% 28% 10% 1	722
	11th to 20th	Night	25% 8% 31% 25% 10% 2	760
	21st to end	Night	23% 10% 31% 27% 10% 1	760
October	1st to 10th	Night	26% 14% 28% 23% 8% 1	760
	11th to 20th	Night	34% 14% 25% 20% 7% 1	760
	21st to end	Night	33% 16% 26% 19% 6% 1	836
November	1st to 10th	Night	33% 16% 29% 17% 4	780
	11th to 20th	Night	33% 20% 25% 16% 5% 1	900
	21st to end	Night	32% 17% 32% 14% 5%	900
December	1st to 10th	Night	30% 20% 28% 16% 5% 1	878
	11th to 20th	Night	30% 23% 28% 15% 4	850
	21st to end	Night	30% 23% 26% 16% 5% 1	935

Page generated at 2024-12-03 06:45:08. Version ac07

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