Mont St-Alex
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mont St-Alex clear sky chart from 2005-11-06 to 2024-01-27.

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% 10% 4 7% 6% 3 5% 5% 5% 7% 31%	74883
	Night	20% 11% 4 8% 6% 3 4 4 4 6% 30%	75162
Transparency	Day	54% 3 12% 21% 9% 1	74588
	Night	57% 3 10% 20% 9% 1	74991
Seeing	Day	24% 9% 26% 24% 13% 4	13550
	Night	26% 7% 26% 29% 10% 1	22643

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	21% 21% 6% 10% 7% 3 4 4 3 4 17%	1517
	11th to 20th	Day	20% 18% 7% 11% 6% 3 5% 3 4 5% 19%	1520
	21st to end	Day	12% 14% 6% 9% 7% 5% 5% 5% 6% 6% 23%	1632
February	1st to 10th	Day	18% 15% 6% 10% 6% 4 6% 5% 4 5% 20%	1558
	11th to 20th	Day	16% 15% 7% 9% 7% 2 5% 5% 5% 5% 24%	1699
	21st to end	Day	17% 14% 6% 6% 8% 4 5% 4 5% 6% 23%	1480
March	1st to 10th	Day	15% 13% 5% 9% 6% 3 6% 5% 5% 5% 28%	1797
	11th to 20th	Day	18% 11% 4 7% 6% 4 4 4 4 6% 31%	1851
	21st to end	Day	21% 10% 4 7% 5% 3 4 4 4 6% 33%	2376
April	1st to 10th	Day	23% 11% 3 6% 6% 3 5% 5% 4 5% 29%	2160
	11th to 20th	Day	21% 8% 4 5% 5% 3 4 3 4 6% 36%	2134
	21st to end	Day	24% 9% 3 5% 6% 3 5% 4 4 6% 31%	2326
May	1st to 10th	Day	21% 8% 3 7% 5% 2 4 4 4 7% 35%	2437
	11th to 20th	Day	18% 6% 3 6% 5% 4 5% 5% 5% 7% 36%	2478
	21st to end	Day	17% 7% 3 6% 5% 3 6% 5% 6% 9% 33%	2725
June	1st to 10th	Day	24% 6% 3 6% 6% 3 5% 5% 6% 7% 30%	2520
	11th to 20th	Day	17% 6% 3 5% 5% 3 5% 5% 5% 8% 38%	2520
	21st to end	Day	21% 7% 4 6% 5% 4 4 5% 5% 7% 32%	2520
July	1st to 10th	Day	14% 5% 2 6% 5% 3 5% 5% 6% 9% 39%	2520
	11th to 20th	Day	13% 6% 2 5% 6% 4 5% 6% 8% 9% 36%	2520
	21st to end	Day	15% 6% 3 4 6% 3 5% 6% 8% 9% 37%	2744
August	1st to 10th	Day	13% 5% 3 6% 7% 4 6% 6% 7% 9% 35%	2506
	11th to 20th	Day	12% 7% 2 5% 5% 3 5% 5% 6% 9% 40%	2277
	21st to end	Day	14% 6% 2 5% 5% 4 5% 4 6% 9% 41%	2376
September	1st to 10th	Day	14% 6% 3 5% 5% 3 4 5% 5% 8% 42%	2160
	11th to 20th	Day	17% 5% 2 4 3 2 3 3 5% 7% 47%	2062
	21st to end	Day	16% 7% 3 5% 5% 3 4 5% 5% 9% 39%	1980
October	1st to 10th	Day	22% 8% 3 6% 6% 3 6% 5% 6% 6% 30%	1896
	11th to 20th	Day	21% 9% 3 7% 5% 4 5% 6% 6% 6% 28%	1739
	21st to end	Day	28% 11% 3 6% 5% 4 4 4 4 6% 26%	1782
November	1st to 10th	Day	19% 12% 3 5% 6% 3 5% 4 5% 6% 32%	1671
	11th to 20th	Day	19% 13% 5% 8% 7% 4 4 5% 6% 6% 25%	1682
	21st to end	Day	22% 14% 5% 7% 6% 3 4 5% 5% 6% 22%	1520
December	1st to 10th	Day	24% 16% 7% 9% 7% 3 4 4 4 5% 17%	1520
	11th to 20th	Day	23% 14% 6% 8% 5% 3 4 5% 5% 6% 22%	1906
	21st to end	Day	27% 17% 5% 10% 6% 3 5% 3 3 4 16%	2772
January	1st to 10th	Night	20% 19% 7% 11% 8% 4 5% 4 3 5% 17%	2649
	11th to 20th	Night	18% 17% 7% 11% 7% 4 5% 4 4 4 19%	2660
	21st to end	Night	16% 14% 6% 9% 9% 4 4 4 4 4 26%	2868
February	1st to 10th	Night	18% 15% 7% 13% 7% 4 5% 3 4 5% 18%	2398
	11th to 20th	Night	16% 13% 6% 11% 9% 3 6% 4 4 5% 24%	2147
	21st to end	Night	18% 13% 5% 9% 7% 3 5% 3 3 5% 29%	1776
March	1st to 10th	Night	18% 15% 4 8% 7% 3 3 4 5% 5% 27%	2150
	11th to 20th	Night	22% 11% 4 7% 7% 3 4 3 3 5% 30%	2105
	21st to end	Night	21% 12% 4 5% 5% 3 5% 3 4 4 35%	1980
April	1st to 10th	Night	24% 10% 5% 6% 6% 3 4 4 5% 5% 28%	1800
	11th to 20th	Night	24% 10% 3 6% 5% 2 3 4 3 6% 33%	1775
	21st to end	Night	22% 10% 3 6% 5% 2 5% 4 4 5% 34%	1634
May	1st to 10th	Night	23% 9% 4 6% 5% 3 4 3 5% 6% 33%	1539
	11th to 20th	Night	18% 9% 2 7% 5% 3 4 4 5% 7% 37%	1415
	21st to end	Night	18% 5% 3 4 6% 4 3 5% 6% 7% 39%	1550
June	1st to 10th	Night	26% 6% 2 5% 5% 2 6% 5% 5% 7% 31%	1440
	11th to 20th	Night	18% 6% 3 5% 6% 3 4 5% 6% 9% 36%	1440
	21st to end	Night	18% 8% 3 6% 5% 3 4 5% 5% 8% 34%	1440
July	1st to 10th	Night	12% 6% 2 6% 6% 4 5% 5% 7% 8% 40%	1440
	11th to 20th	Night	11% 5% 2 6% 5% 4 7% 5% 7% 9% 39%	1440
	21st to end	Night	13% 5% 2 7% 6% 4 6% 5% 6% 8% 38%	1574
August	1st to 10th	Night	14% 4 1 5% 6% 4 5% 4 6% 10% 40%	1432
	11th to 20th	Night	14% 7% 2 5% 6% 3 4 5% 6% 7% 40%	1603
	21st to end	Night	13% 7% 3 6% 5% 3 4 5% 5% 7% 42%	1980
September	1st to 10th	Night	14% 7% 2 6% 6% 3 4 5% 5% 7% 41%	1800
	11th to 20th	Night	15% 6% 2 5% 5% 2 3 4 5% 6% 47%	1898
	21st to end	Night	19% 6% 3 5% 4 2 4 4 5% 7% 41%	1980
October	1st to 10th	Night	20% 6% 3 6% 6% 3 4 5% 6% 6% 35%	2060
	11th to 20th	Night	22% 10% 3 7% 5% 3 4 4 5% 6% 30%	2219
	21st to end	Night	26% 11% 3 7% 5% 3 4 4 4 5% 27%	2574
November	1st to 10th	Night	20% 11% 4 6% 5% 3 5% 5% 4 6% 30%	2407
	11th to 20th	Night	21% 10% 4 9% 5% 3 4 4 4 5% 29%	2497
	21st to end	Night	23% 14% 5% 9% 5% 3 4 4 4 5% 24%	2660
December	1st to 10th	Night	24% 18% 6% 9% 7% 3 5% 4 4 5% 16%	2660
	11th to 20th	Night	25% 15% 6% 10% 6% 3 4 3 4 4 21%	3288
	21st to end	Night	27% 17% 5% 10% 6% 3 3 3 3 4 19%	4884

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	72% 2 9% 15% 2	1518
	11th to 20th	Day	70% 2 9% 13% 6%	1520
	21st to end	Day	61% 3 12% 17% 6% 1	1632
February	1st to 10th	Day	68% 3 10% 15% 4 1	1558
	11th to 20th	Day	64% 2 12% 17% 5% 1	1708
	21st to end	Day	63% 2 12% 15% 8% 1	1480
March	1st to 10th	Day	60% 3 10% 19% 7% 2	1800
	11th to 20th	Day	56% 3 12% 18% 11% 1	1851
	21st to end	Day	55% 2 8% 22% 10% 2	2376
April	1st to 10th	Day	59% 3 8% 20% 9% 1	2160
	11th to 20th	Day	51% 2 9% 23% 13% 2	2134
	21st to end	Day	56% 3 11% 18% 10% 3	2326
May	1st to 10th	Day	51% 2 10% 21% 14% 2	2437
	11th to 20th	Day	49% 3 10% 21% 14% 2	2482
	21st to end	Day	49% 4 14% 20% 12% 1	2725
June	1st to 10th	Day	53% 3 12% 21% 9% 1	2520
	11th to 20th	Day	44% 5% 11% 25% 13% 2	2520
	21st to end	Day	52% 4 12% 21% 9% 1	2520
July	1st to 10th	Day	40% 4 15% 29% 11%	2450
	11th to 20th	Day	43% 4 15% 31% 7%	2445
	21st to end	Day	44% 4 19% 26% 7% 1	2591
August	1st to 10th	Day	45% 4 19% 25% 7%	2492
	11th to 20th	Day	40% 4 20% 25% 10%	2277
	21st to end	Day	41% 4 15% 28% 11%	2376
September	1st to 10th	Day	42% 4 14% 28% 11% 1	2160
	11th to 20th	Day	38% 3 12% 34% 13%	2062
	21st to end	Day	43% 5% 15% 27% 10% 1	1980
October	1st to 10th	Day	54% 4 11% 22% 8%	1896
	11th to 20th	Day	55% 4 16% 19% 6%	1739
	21st to end	Day	62% 2 12% 18% 5% 1	1782
November	1st to 10th	Day	55% 3 13% 21% 8% 1	1671
	11th to 20th	Day	61% 4 12% 15% 9%	1682
	21st to end	Day	64% 4 15% 14% 3	1520
December	1st to 10th	Day	73% 3 11% 11% 2	1520
	11th to 20th	Day	65% 3 11% 17% 4	1906
	21st to end	Day	74% 3 11% 11% 3	2772
January	1st to 10th	Night	72% 2 8% 14% 3	2649
	11th to 20th	Night	70% 3 8% 14% 5%	2660
	21st to end	Night	64% 3 9% 15% 9% 1	2868
February	1st to 10th	Night	70% 2 8% 14% 5% 1	2398
	11th to 20th	Night	64% 3 9% 18% 6%	2149
	21st to end	Night	61% 2 9% 16% 11% 2	1776
March	1st to 10th	Night	61% 2 9% 18% 8% 2	2160
	11th to 20th	Night	60% 3 7% 18% 10% 2	2106
	21st to end	Night	55% 2 6% 22% 12% 3	1980
April	1st to 10th	Night	60% 2 7% 19% 11% 1	1800
	11th to 20th	Night	55% 2 6% 22% 13% 2	1775
	21st to end	Night	54% 3 8% 19% 13% 3	1634
May	1st to 10th	Night	53% 3 6% 19% 15% 4	1539
	11th to 20th	Night	49% 2 8% 21% 17% 3	1416
	21st to end	Night	45% 5% 11% 21% 15% 2	1551
June	1st to 10th	Night	52% 4 11% 22% 10% 1	1440
	11th to 20th	Night	45% 4 11% 23% 14% 3	1440
	21st to end	Night	48% 5% 13% 22% 11%	1440
July	1st to 10th	Night	40% 5% 14% 26% 15% 1	1400
	11th to 20th	Night	39% 5% 14% 30% 11%	1392
	21st to end	Night	43% 5% 15% 26% 10%	1486
August	1st to 10th	Night	40% 5% 18% 27% 10%	1422
	11th to 20th	Night	43% 4 15% 25% 12% 1	1603
	21st to end	Night	43% 4 13% 26% 12% 1	1980
September	1st to 10th	Night	42% 4 12% 28% 13% 1	1800
	11th to 20th	Night	38% 3 14% 32% 12% 1	1898
	21st to end	Night	44% 4 11% 27% 13% 1	1980
October	1st to 10th	Night	48% 3 12% 23% 12% 1	2060
	11th to 20th	Night	56% 3 10% 24% 7%	2219
	21st to end	Night	61% 3 10% 16% 9% 1	2574
November	1st to 10th	Night	56% 3 11% 22% 7% 1	2407
	11th to 20th	Night	58% 3 11% 19% 8% 2	2497
	21st to end	Night	65% 2 12% 17% 5%	2660
December	1st to 10th	Night	73% 3 10% 12% 2	2660
	11th to 20th	Night	70% 2 8% 16% 4	3288
	21st to end	Night	72% 2 10% 14% 3	4884

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	31% 8% 25% 24% 10% 2	180
	11th to 20th	Day	32% 11% 32% 18% 6% 1	180
	21st to end	Day	21% 12% 37% 19% 9% 2	188
February	1st to 10th	Day	34% 19% 31% 13% 3	213
	11th to 20th	Day	27% 12% 35% 20% 6%	367
	21st to end	Day	27% 12% 29% 27% 5%	346
March	1st to 10th	Day	28% 9% 27% 29% 7%	420
	11th to 20th	Day	27% 9% 34% 21% 7% 2	420
	21st to end	Day	31% 11% 26% 22% 9% 1	462
April	1st to 10th	Day	31% 11% 26% 20% 10% 2	420
	11th to 20th	Day	31% 14% 24% 18% 9% 5%	412
	21st to end	Day	31% 7% 29% 19% 11% 3	420
May	1st to 10th	Day	28% 10% 28% 19% 12% 3	423
	11th to 20th	Day	19% 9% 29% 28% 10% 5%	447
	21st to end	Day	19% 7% 33% 25% 13% 3	485
June	1st to 10th	Day	26% 8% 25% 28% 11% 2	450
	11th to 20th	Day	20% 7% 23% 30% 16% 3	450
	21st to end	Day	21% 7% 30% 24% 14% 4	450
July	1st to 10th	Day	15% 3 23% 36% 17% 5%	445
	11th to 20th	Day	18% 4 26% 30% 17% 5%	444
	21st to end	Day	20% 4 20% 33% 20% 3	488
August	1st to 10th	Day	17% 3 22% 29% 23% 6%	446
	11th to 20th	Day	18% 3 19% 33% 20% 8%	439
	21st to end	Day	17% 7% 23% 24% 19% 9%	495
September	1st to 10th	Day	16% 5% 25% 26% 18% 9%	450
	11th to 20th	Day	17% 6% 21% 24% 20% 12%	450
	21st to end	Day	18% 5% 27% 23% 20% 7%	450
October	1st to 10th	Day	23% 8% 29% 18% 17% 5%	450
	11th to 20th	Day	29% 11% 26% 21% 12% 2	419
	21st to end	Day	37% 11% 22% 23% 8%	396
November	1st to 10th	Day	30% 13% 27% 22% 8%	365
	11th to 20th	Day	30% 15% 25% 18% 10% 2	342
	21st to end	Day	31% 15% 25% 22% 7% 1	180
December	1st to 10th	Day	38% 10% 22% 21% 8% 2	180
	11th to 20th	Day	27% 17% 36% 14% 7%	180
	21st to end	Day	36% 14% 26% 18% 5% 2	198
January	1st to 10th	Night	30% 10% 30% 24% 5% 1	760
	11th to 20th	Night	27% 11% 32% 23% 7%	760
	21st to end	Night	25% 8% 29% 29% 8% 1	820
February	1st to 10th	Night	27% 9% 32% 27% 6%	720
	11th to 20th	Night	24% 10% 32% 29% 5% 1	703
	21st to end	Night	26% 9% 31% 28% 5%	592
March	1st to 10th	Night	27% 10% 27% 31% 5%	720
	11th to 20th	Night	29% 10% 27% 25% 8%	720
	21st to end	Night	29% 9% 27% 26% 8% 1	792
April	1st to 10th	Night	30% 9% 26% 28% 7%	720
	11th to 20th	Night	29% 11% 27% 24% 9%	711
	21st to end	Night	28% 9% 27% 28% 7% 1	554
May	1st to 10th	Night	26% 5% 31% 25% 12% 1	459
	11th to 20th	Night	25% 5% 27% 32% 10% 1	354
	21st to end	Night	20% 5% 28% 37% 10% 1	389
June	1st to 10th	Night	29% 4 23% 31% 11% 1	360
	11th to 20th	Night	21% 3 26% 34% 16% 1	360
	21st to end	Night	20% 4 24% 38% 14% 1	360
July	1st to 10th	Night	13% 3 26% 43% 15% 1	350
	11th to 20th	Night	11% 1 18% 50% 18% 1	348
	21st to end	Night	15% 2 20% 48% 15% 1	394
August	1st to 10th	Night	16% 2 16% 40% 25% 2	358
	11th to 20th	Night	18% 2 16% 38% 24% 2	539
	21st to end	Night	19% 3 16% 37% 22% 2	792
September	1st to 10th	Night	17% 5% 18% 41% 17% 2	720
	11th to 20th	Night	18% 5% 18% 34% 21% 4	720
	21st to end	Night	22% 5% 25% 28% 17% 3	720
October	1st to 10th	Night	24% 4 25% 30% 16% 1	720
	11th to 20th	Night	29% 6% 26% 29% 9% 1	720
	21st to end	Night	33% 6% 29% 24% 7%	792
November	1st to 10th	Night	29% 10% 29% 24% 7% 1	740
	11th to 20th	Night	27% 12% 27% 24% 9% 1	760
	21st to end	Night	33% 9% 30% 21% 7%	760
December	1st to 10th	Night	36% 10% 27% 21% 6% 1	760
	11th to 20th	Night	33% 9% 29% 22% 6% 1	760
	21st to end	Night	36% 9% 29% 21% 5%	836

Page generated at 2024-01-24 09:37:30. Version ac07

Copyright 2024 Attilla Danko