L'Assomption
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the L'Assomption 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	17% 9% 3 7% 5% 5% 5% 4 5% 7% 34%	101950
	Night	18% 10% 3 8% 5% 4 4 3 5% 6% 33%	98183
Transparency	Day	26% 48% 8% 12% 5%	105413
	Night	29% 47% 7% 11% 6% 1	102809
Seeing	Day	21% 11% 27% 25% 12% 3	14678
	Night	23% 9% 29% 29% 10% 1	23683

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	17% 15% 5% 9% 5% 4 5% 3 4 5% 27%	2517
	11th to 20th	Day	14% 13% 5% 8% 5% 4 4 3 5% 6% 31%	2520
	21st to end	Day	13% 15% 5% 11% 6% 5% 5% 4 5% 6% 25%	2772
February	1st to 10th	Day	16% 17% 4 8% 6% 5% 5% 3 4 5% 28%	1643
	11th to 20th	Day	14% 12% 4 11% 6% 5% 4 5% 5% 6% 28%	1769
	21st to end	Day	17% 15% 4 9% 4 4 4 4 4 6% 28%	1570
March	1st to 10th	Day	19% 12% 3 8% 6% 5% 5% 4 5% 5% 28%	3116
	11th to 20th	Day	13% 16% 5% 10% 6% 5% 4 3 5% 5% 28%	3271
	21st to end	Day	14% 8% 4 8% 5% 4 5% 4 5% 6% 38%	4166
April	1st to 10th	Day	21% 10% 3 7% 5% 5% 4 4 4 5% 32%	2280
	11th to 20th	Day	21% 8% 2 6% 5% 3 3 3 5% 6% 37%	2254
	21st to end	Day	22% 8% 3 7% 5% 4 5% 4 4 5% 33%	2452
May	1st to 10th	Day	20% 8% 3 7% 5% 5% 4 4 5% 7% 33%	4354
	11th to 20th	Day	17% 7% 3 8% 5% 5% 5% 3 6% 8% 32%	4398
	21st to end	Day	15% 5% 3 6% 5% 5% 5% 4 6% 9% 36%	4837
June	1st to 10th	Day	21% 8% 2 7% 5% 4 4 4 6% 8% 31%	2660
	11th to 20th	Day	14% 6% 2 7% 5% 4 5% 4 7% 8% 38%	2660
	21st to end	Day	20% 8% 3 7% 5% 5% 5% 4 6% 7% 30%	2660
July	1st to 10th	Day	12% 6% 2 8% 5% 5% 6% 5% 7% 9% 36%	4440
	11th to 20th	Day	13% 5% 2 6% 5% 6% 6% 4 7% 8% 38%	4440
	21st to end	Day	11% 6% 2 5% 4 4 4 4 6% 9% 45%	4814
August	1st to 10th	Day	14% 5% 2 7% 6% 6% 7% 5% 7% 9% 33%	4423
	11th to 20th	Day	14% 6% 3 7% 4 4 5% 4 6% 8% 38%	4028
	21st to end	Day	16% 6% 2 7% 4 4 4 4 6% 8% 40%	4180
September	1st to 10th	Day	11% 5% 2 6% 4 5% 5% 5% 6% 9% 42%	2280
	11th to 20th	Day	13% 6% 2 5% 3 4 4 3 4 6% 50%	2190
	21st to end	Day	17% 6% 3 5% 3 4 5% 3 6% 6% 41%	2090
October	1st to 10th	Day	19% 6% 2 7% 5% 4 4 3 6% 7% 36%	1976
	11th to 20th	Day	19% 8% 3 8% 6% 6% 4 4 6% 6% 31%	1841
	21st to end	Day	24% 9% 3 7% 4 4 4 3 5% 6% 32%	1881
November	1st to 10th	Day	17% 10% 3 7% 4 4 4 4 5% 8% 35%	1761
	11th to 20th	Day	18% 10% 3 8% 4 5% 4 4 6% 6% 33%	1725
	21st to end	Day	23% 12% 3 7% 4 4 5% 4 5% 6% 28%	1600
December	1st to 10th	Day	24% 14% 4 10% 6% 5% 3 2 4 5% 23%	1600
	11th to 20th	Day	22% 14% 3 9% 5% 3 3 3 4 4 29%	1986
	21st to end	Day	27% 16% 4 9% 5% 3 3 2 3 4 23%	2796
January	1st to 10th	Night	17% 16% 5% 9% 5% 5% 5% 4 4 5% 26%	4429
	11th to 20th	Night	12% 12% 5% 11% 8% 6% 6% 4 5% 5% 26%	4440
	21st to end	Night	15% 15% 5% 12% 7% 4 5% 3 5% 5% 25%	4884
February	1st to 10th	Night	14% 15% 6% 12% 7% 6% 4 4 5% 5% 25%	2533
	11th to 20th	Night	14% 12% 4 9% 6% 5% 6% 4 4 5% 30%	2297
	21st to end	Night	15% 13% 4 10% 6% 4 4 3 5% 5% 31%	1884
March	1st to 10th	Night	22% 12% 4 7% 4 3 4 3 4 4 33%	3724
	11th to 20th	Night	17% 17% 4 10% 5% 4 3 2 5% 4 29%	3686
	21st to end	Night	14% 10% 4 9% 5% 5% 4 3 4 5% 37%	3466
April	1st to 10th	Night	24% 9% 3 7% 4 4 4 4 5% 6% 30%	1900
	11th to 20th	Night	21% 8% 2 7% 4 3 5% 4 5% 5% 35%	1875
	21st to end	Night	23% 8% 3 6% 4 3 3 3 5% 5% 35%	1726
May	1st to 10th	Night	22% 9% 2 8% 5% 4 5% 4 5% 6% 31%	2615
	11th to 20th	Night	22% 7% 2 6% 4 4 5% 3 5% 7% 33%	2495
	21st to end	Night	16% 7% 3 7% 5% 5% 4 4 5% 9% 35%	2738
June	1st to 10th	Night	21% 8% 2 6% 4 5% 4 5% 6% 7% 33%	1520
	11th to 20th	Night	17% 7% 3 6% 4 4 4 3 6% 8% 38%	1520
	21st to end	Night	20% 6% 3 6% 6% 5% 4 5% 6% 7% 33%	1520
July	1st to 10th	Night	12% 7% 3 8% 6% 5% 5% 4 8% 9% 33%	2520
	11th to 20th	Night	15% 6% 2 5% 4 5% 5% 3 7% 7% 41%	2520
	21st to end	Night	11% 4 2 6% 5% 4 5% 4 6% 8% 45%	2739
August	1st to 10th	Night	15% 6% 3 9% 5% 5% 5% 4 6% 6% 37%	2506
	11th to 20th	Night	16% 7% 3 7% 4 5% 4 4 5% 7% 38%	2765
	21st to end	Night	18% 6% 3 8% 5% 4 4 3 5% 6% 38%	3476
September	1st to 10th	Night	12% 5% 2 7% 4 4 5% 3 5% 6% 46%	1900
	11th to 20th	Night	14% 5% 2 6% 4 3 3 3 4 7% 50%	1990
	21st to end	Night	16% 6% 2 5% 4 4 4 3 5% 7% 44%	2090
October	1st to 10th	Night	18% 5% 3 7% 5% 5% 4 3 5% 6% 41%	2200
	11th to 20th	Night	20% 9% 3 7% 4 4 4 3 4 5% 36%	2338
	21st to end	Night	23% 8% 3 7% 4 4 4 3 4 6% 32%	2717
November	1st to 10th	Night	19% 10% 3 7% 5% 5% 4 3 5% 6% 34%	2537
	11th to 20th	Night	19% 10% 3 7% 4 4 4 4 5% 6% 34%	2672
	21st to end	Night	23% 13% 3 8% 5% 4 4 3 3 5% 28%	2800
December	1st to 10th	Night	21% 14% 6% 9% 6% 5% 4 3 5% 5% 22%	2800
	11th to 20th	Night	24% 14% 4 9% 5% 3 3 2 4 4 29%	3428
	21st to end	Night	27% 15% 5% 9% 4 3 3 2 4 4 23%	4933

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	37% 41% 10% 9% 3	2518
	11th to 20th	Day	32% 40% 10% 13% 5%	2520
	21st to end	Day	38% 42% 10% 8% 2	2772
February	1st to 10th	Day	21% 65% 4 7% 2 1	1643
	11th to 20th	Day	19% 65% 3 7% 5%	1778
	21st to end	Day	21% 65% 3 5% 5% 2	1570
March	1st to 10th	Day	36% 43% 6% 11% 4 1	3119
	11th to 20th	Day	37% 42% 6% 5% 7% 3	3271
	21st to end	Day	27% 42% 5% 13% 11% 1	4166
April	1st to 10th	Day	20% 65% 3 6% 5% 1	2280
	11th to 20th	Day	18% 65% 3 9% 4 1	2254
	21st to end	Day	19% 65% 4 7% 5%	2452
May	1st to 10th	Day	31% 44% 7% 15% 3	4368
	11th to 20th	Day	29% 45% 12% 10% 4	4402
	21st to end	Day	25% 43% 8% 16% 7%	4837
June	1st to 10th	Day	17% 66% 4 7% 5% 1	2660
	11th to 20th	Day	15% 66% 5% 7% 6% 1	2660
	21st to end	Day	18% 64% 5% 8% 5% 1	2660
July	1st to 10th	Day	29% 38% 9% 18% 6% 1	4370
	11th to 20th	Day	26% 39% 12% 20% 4	4365
	21st to end	Day	22% 37% 10% 25% 6%	4661
August	1st to 10th	Day	30% 39% 12% 13% 4	4409
	11th to 20th	Day	30% 40% 13% 15% 2	4070
	21st to end	Day	29% 38% 10% 13% 10%	4180
September	1st to 10th	Day	13% 63% 7% 13% 5%	2280
	11th to 20th	Day	13% 61% 6% 14% 4 1	2190
	21st to end	Day	14% 61% 5% 13% 6%	2090
October	1st to 10th	Day	26% 39% 10% 20% 4	3288
	11th to 20th	Day	24% 39% 14% 19% 4	3031
	21st to end	Day	25% 39% 14% 16% 6%	3081
November	1st to 10th	Day	25% 57% 6% 8% 3	1761
	11th to 20th	Day	20% 58% 5% 11% 6%	1725
	21st to end	Day	27% 59% 5% 5% 3	1600
December	1st to 10th	Day	29% 57% 5% 7% 2	1600
	11th to 20th	Day	33% 47% 5% 10% 4	1986
	21st to end	Day	43% 38% 8% 6% 4	2796
January	1st to 10th	Night	37% 40% 13% 7% 3	4429
	11th to 20th	Night	34% 43% 9% 11% 3	4440
	21st to end	Night	40% 42% 8% 7% 2	4884
February	1st to 10th	Night	22% 66% 4 6% 2	2533
	11th to 20th	Night	20% 64% 3 8% 5%	2299
	21st to end	Night	18% 65% 3 6% 7% 1	1884
March	1st to 10th	Night	31% 42% 6% 11% 6% 3	3734
	11th to 20th	Night	37% 41% 4 6% 10% 2	3687
	21st to end	Night	30% 42% 4 15% 8% 2	3466
April	1st to 10th	Night	20% 64% 3 7% 6%	1900
	11th to 20th	Night	20% 65% 2 7% 4 1	1875
	21st to end	Night	19% 65% 3 6% 6% 1	1726
May	1st to 10th	Night	32% 45% 8% 12% 3	2621
	11th to 20th	Night	30% 44% 9% 13% 5%	2496
	21st to end	Night	28% 41% 8% 12% 11% 1	2739
June	1st to 10th	Night	18% 65% 3 7% 6%	1520
	11th to 20th	Night	15% 65% 5% 8% 6% 1	1520
	21st to end	Night	18% 64% 4 7% 6%	1520
July	1st to 10th	Night	32% 37% 10% 12% 8% 1	2480
	11th to 20th	Night	26% 38% 14% 18% 4	2472
	21st to end	Night	23% 38% 14% 16% 9%	2651
August	1st to 10th	Night	33% 39% 7% 17% 4	2496
	11th to 20th	Night	34% 40% 12% 13% 2	2789
	21st to end	Night	31% 38% 8% 13% 10% 1	3476
September	1st to 10th	Night	12% 61% 6% 11% 8% 1	1900
	11th to 20th	Night	14% 60% 7% 13% 5% 1	1990
	21st to end	Night	14% 61% 4 13% 8%	2090
October	1st to 10th	Night	28% 38% 10% 17% 6%	3668
	11th to 20th	Night	25% 38% 8% 23% 6%	3887
	21st to end	Night	29% 37% 11% 12% 9% 1	4467
November	1st to 10th	Night	25% 56% 6% 9% 3 1	2537
	11th to 20th	Night	23% 57% 5% 9% 5% 1	2672
	21st to end	Night	27% 58% 5% 7% 4	2800
December	1st to 10th	Night	28% 58% 6% 6% 2	2800
	11th to 20th	Night	34% 48% 5% 7% 6%	3428
	21st to end	Night	43% 38% 5% 11% 3	4933

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% 13% 29% 18% 12%	180
	11th to 20th	Day	25% 15% 34% 19% 6% 1	180
	21st to end	Day	19% 11% 35% 23% 11% 1	198
February	1st to 10th	Day	29% 16% 34% 18% 3	238
	11th to 20th	Day	21% 15% 33% 25% 4 1	377
	21st to end	Day	28% 12% 31% 24% 4	382
March	1st to 10th	Day	23% 12% 29% 26% 10%	460
	11th to 20th	Day	21% 14% 35% 22% 7% 1	460
	21st to end	Day	27% 11% 32% 21% 8% 1	506
April	1st to 10th	Day	28% 14% 27% 21% 8% 2	460
	11th to 20th	Day	27% 18% 25% 19% 8% 3	452
	21st to end	Day	27% 13% 30% 18% 10% 1	460
May	1st to 10th	Day	23% 11% 33% 20% 11% 2	463
	11th to 20th	Day	17% 11% 28% 26% 14% 4	487
	21st to end	Day	19% 13% 30% 26% 10% 2	529
June	1st to 10th	Day	22% 11% 25% 29% 10% 2	490
	11th to 20th	Day	16% 10% 26% 32% 14% 2	490
	21st to end	Day	23% 11% 23% 26% 14% 3	490
July	1st to 10th	Day	13% 8% 24% 31% 19% 5%	485
	11th to 20th	Day	14% 8% 26% 33% 16% 4	484
	21st to end	Day	14% 7% 24% 33% 18% 3	532
August	1st to 10th	Day	15% 5% 23% 30% 21% 6%	486
	11th to 20th	Day	12% 6% 20% 30% 22% 9%	479
	21st to end	Day	16% 8% 22% 26% 18% 10%	539
September	1st to 10th	Day	12% 9% 27% 29% 16% 7%	490
	11th to 20th	Day	14% 8% 20% 27% 19% 13%	490
	21st to end	Day	18% 8% 26% 24% 18% 6%	490
October	1st to 10th	Day	20% 13% 26% 23% 14% 4	490
	11th to 20th	Day	23% 12% 29% 23% 11% 2	458
	21st to end	Day	30% 11% 27% 24% 8%	429
November	1st to 10th	Day	26% 13% 30% 21% 9%	395
	11th to 20th	Day	23% 15% 31% 21% 8% 2	325
	21st to end	Day	33% 13% 30% 16% 9% 1	200
December	1st to 10th	Day	30% 10% 25% 21% 12% 3	200
	11th to 20th	Day	26% 22% 32% 16% 4 1	200
	21st to end	Day	33% 17% 26% 20% 3 1	204
January	1st to 10th	Night	28% 10% 30% 27% 5%	760
	11th to 20th	Night	25% 10% 34% 25% 6%	760
	21st to end	Night	20% 9% 33% 31% 6% 1	836
February	1st to 10th	Night	22% 10% 36% 27% 5% 1	760
	11th to 20th	Night	19% 11% 38% 26% 5% 1	743
	21st to end	Night	22% 10% 33% 30% 5%	628
March	1st to 10th	Night	26% 8% 31% 30% 6%	760
	11th to 20th	Night	26% 10% 30% 26% 7%	760
	21st to end	Night	22% 9% 31% 29% 8%	836
April	1st to 10th	Night	28% 11% 26% 28% 6%	760
	11th to 20th	Night	25% 13% 29% 26% 6% 1	751
	21st to end	Night	28% 11% 30% 24% 7% 1	586
May	1st to 10th	Night	25% 7% 32% 27% 8% 1	442
	11th to 20th	Night	23% 9% 28% 30% 9% 1	374
	21st to end	Night	18% 9% 36% 29% 9%	411
June	1st to 10th	Night	23% 6% 26% 35% 9% 1	380
	11th to 20th	Night	19% 3 29% 36% 13%	380
	21st to end	Night	18% 7% 27% 33% 14% 1	380
July	1st to 10th	Night	12% 5% 29% 38% 15% 1	370
	11th to 20th	Night	12% 2 24% 46% 14% 1	368
	21st to end	Night	13% 4 21% 45% 16%	416
August	1st to 10th	Night	14% 5% 17% 44% 19% 2	378
	11th to 20th	Night	14% 4 19% 38% 23% 2	541
	21st to end	Night	16% 4 21% 36% 20% 2	836
September	1st to 10th	Night	15% 5% 23% 41% 15% 1	760
	11th to 20th	Night	17% 5% 21% 34% 21% 2	760
	21st to end	Night	18% 6% 26% 31% 15% 3	760
October	1st to 10th	Night	21% 7% 27% 31% 13% 1	760
	11th to 20th	Night	26% 8% 27% 29% 9% 1	760
	21st to end	Night	27% 10% 31% 25% 7%	836
November	1st to 10th	Night	24% 12% 31% 25% 8%	780
	11th to 20th	Night	25% 10% 33% 23% 9% 1	800
	21st to end	Night	30% 12% 30% 21% 7%	800
December	1st to 10th	Night	29% 11% 29% 25% 7%	800
	11th to 20th	Night	28% 12% 31% 21% 6% 1	800
	21st to end	Night	31% 11% 30% 21% 6%	851

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

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