Mingan
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mingan clear sky chart from 2005-11-06 to 2026-03-18.

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 4 3 5% 6% 32%	131116
	Night	17% 12% 4 9% 5% 4 4 3 5% 6% 31%	130628
Transparency	Day	53% 3 12% 22% 9% 1	134513
	Night	55% 3 11% 20% 10% 1	135325
Seeing	Day	26% 8% 27% 25% 11% 3	18349
	Night	26% 7% 26% 29% 11% 1	25904

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	14% 21% 6% 9% 4 4 3 2 3 5% 30%	4093
	11th to 20th	Day	10% 19% 6% 15% 6% 6% 5% 3 4 6% 20%	4084
	21st to end	Day	5% 9% 3 10% 7% 6% 6% 4 8% 11% 32%	4845
February	1st to 10th	Day	8% 13% 5% 11% 5% 6% 5% 4 5% 5% 34%	1890
	11th to 20th	Day	10% 17% 5% 10% 5% 6% 4 3 5% 6% 30%	1843
	21st to end	Day	9% 13% 4 9% 6% 5% 4 3 4 6% 35%	1557
March	1st to 10th	Day	16% 13% 4 9% 6% 4 5% 3 4 5% 31%	4766
	11th to 20th	Day	19% 19% 4 9% 5% 4 4 3 4 4 23%	5057
	21st to end	Day	20% 18% 5% 9% 5% 4 4 3 4 4 25%	5543
April	1st to 10th	Day	21% 14% 4 7% 5% 4 4 3 4 6% 27%	2400
	11th to 20th	Day	16% 11% 3 7% 5% 4 3 3 4 6% 37%	2567
	21st to end	Day	24% 10% 3 5% 4 4 3 3 4 5% 35%	2640
May	1st to 10th	Day	29% 9% 3 8% 5% 4 4 3 4 6% 27%	6345
	11th to 20th	Day	21% 7% 3 7% 5% 5% 4 3 5% 6% 34%	6318
	21st to end	Day	25% 9% 3 7% 4 3 3 3 4 5% 33%	7449
June	1st to 10th	Day	24% 9% 3 7% 4 4 4 3 5% 6% 31%	3000
	11th to 20th	Day	21% 6% 3 6% 4 4 5% 4 6% 7% 33%	3000
	21st to end	Day	25% 7% 2 6% 5% 4 4 4 6% 7% 30%	3000
July	1st to 10th	Day	15% 7% 3 7% 5% 5% 5% 4 5% 6% 37%	6820
	11th to 20th	Day	17% 8% 3 8% 4 4 5% 4 7% 8% 32%	6820
	21st to end	Day	14% 6% 2 6% 5% 5% 4 4 6% 7% 42%	7298
August	1st to 10th	Day	14% 6% 2 6% 5% 5% 5% 4 6% 8% 40%	4506
	11th to 20th	Day	22% 10% 4 8% 4 4 5% 3 5% 6% 28%	4175
	21st to end	Day	15% 6% 3 6% 4 4 5% 4 6% 7% 42%	4625
September	1st to 10th	Day	20% 5% 2 6% 4 5% 4 4 6% 6% 38%	2400
	11th to 20th	Day	23% 7% 3 5% 4 3 3 3 4 6% 39%	2350
	21st to end	Day	20% 7% 2 6% 5% 4 3 4 5% 5% 39%	2123
October	1st to 10th	Day	19% 6% 3 7% 4 4 4 3 5% 6% 38%	2000
	11th to 20th	Day	24% 9% 3 6% 4 4 3 3 5% 7% 32%	2000
	21st to end	Day	24% 11% 3 6% 5% 5% 3 2 4 5% 32%	1962
November	1st to 10th	Day	22% 10% 3 7% 5% 4 4 3 4 6% 31%	1645
	11th to 20th	Day	24% 14% 4 8% 4 3 4 3 4 6% 28%	1680
	21st to end	Day	22% 16% 4 8% 4 4 4 4 4 5% 25%	1680
December	1st to 10th	Day	10% 15% 7% 11% 6% 6% 4 5% 5% 6% 26%	2394
	11th to 20th	Day	21% 11% 5% 9% 5% 3 4 3 5% 6% 26%	2688
	21st to end	Day	15% 13% 4 8% 4 4 4 3 5% 6% 35%	3553
January	1st to 10th	Night	15% 21% 5% 11% 5% 3 3 2 5% 5% 25%	8831
	11th to 20th	Night	11% 15% 6% 12% 6% 4 4 3 5% 6% 26%	8831
	21st to end	Night	4 10% 4 12% 7% 5% 5% 3 5% 9% 35%	9343
February	1st to 10th	Night	8% 15% 5% 10% 5% 5% 4 4 5% 6% 33%	2730
	11th to 20th	Night	13% 17% 5% 9% 6% 4 5% 3 5% 5% 30%	2663
	21st to end	Night	9% 14% 5% 9% 6% 5% 4 4 4 5% 34%	2249
March	1st to 10th	Night	14% 14% 4 10% 5% 4 4 3 4 5% 33%	5276
	11th to 20th	Night	22% 19% 5% 9% 5% 4 3 3 4 4 22%	5057
	21st to end	Night	20% 18% 5% 9% 4 4 4 3 4 4 25%	5388
April	1st to 10th	Night	21% 13% 4 7% 5% 4 4 4 5% 6% 27%	2000
	11th to 20th	Night	19% 11% 3 7% 4 3 4 3 6% 5% 35%	1781
	21st to end	Night	26% 9% 3 6% 5% 4 4 3 4 4 33%	1760
May	1st to 10th	Night	29% 11% 3 7% 4 3 3 3 4 4 30%	3615
	11th to 20th	Night	20% 7% 3 8% 4 4 4 3 5% 7% 35%	3596
	21st to end	Night	23% 9% 3 6% 4 5% 4 3 5% 6% 31%	3491
June	1st to 10th	Night	27% 6% 2 6% 4 4 3 4 6% 5% 32%	1400
	11th to 20th	Night	23% 8% 2 6% 5% 4 4 4 6% 8% 31%	1400
	21st to end	Night	26% 8% 2 7% 5% 5% 5% 3 6% 6% 28%	1400
July	1st to 10th	Night	18% 9% 3 6% 4 4 4 4 5% 7% 35%	3160
	11th to 20th	Night	16% 9% 3 8% 5% 4 4 5% 6% 9% 31%	3160
	21st to end	Night	14% 7% 3 8% 5% 4 4 4 6% 8% 38%	3530
August	1st to 10th	Night	14% 9% 3 8% 5% 4 5% 4 6% 8% 34%	2649
	11th to 20th	Night	20% 7% 3 8% 5% 4 5% 4 4 6% 33%	2872
	21st to end	Night	18% 7% 3 8% 5% 4 4 3 5% 7% 37%	3272
September	1st to 10th	Night	22% 7% 2 5% 4 3 3 3 5% 6% 39%	2000
	11th to 20th	Night	23% 5% 2 7% 4 4 4 3 5% 6% 38%	2049
	21st to end	Night	22% 7% 3 6% 3 3 4 3 5% 6% 39%	2276
October	1st to 10th	Night	22% 9% 2 7% 5% 3 3 3 6% 5% 35%	2400
	11th to 20th	Night	28% 8% 3 7% 4 4 4 3 5% 5% 30%	2400
	21st to end	Night	24% 10% 3 7% 4 4 4 3 4 6% 32%	2875
November	1st to 10th	Night	24% 11% 3 7% 4 4 4 3 5% 6% 31%	2873
	11th to 20th	Night	26% 14% 4 7% 5% 3 3 3 4 5% 26%	2940
	21st to end	Night	24% 17% 4 8% 4 4 3 3 4 5% 25%	2940
December	1st to 10th	Night	14% 16% 5% 11% 6% 4 4 3 4 4 28%	5013
	11th to 20th	Night	20% 12% 5% 9% 5% 4 4 4 5% 6% 27%	5741
	21st to end	Night	14% 15% 4 7% 4 4 4 3 5% 7% 34%	7667

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	59% 2 8% 18% 11% 2	4094
	11th to 20th	Day	65% 2 11% 16% 5% 1	4110
	21st to end	Day	44% 2 13% 18% 19% 4	4845
February	1st to 10th	Day	52% 2 10% 20% 14% 2	1890
	11th to 20th	Day	57% 2 10% 18% 12% 1	1851
	21st to end	Day	52% 2 9% 22% 14% 1	1557
March	1st to 10th	Day	56% 2 9% 15% 16% 2	4770
	11th to 20th	Day	66% 2 6% 15% 9% 2	5057
	21st to end	Day	66% 1 5% 17% 9% 2	5543
April	1st to 10th	Day	61% 2 7% 14% 13% 3	2400
	11th to 20th	Day	50% 3 10% 22% 13% 3	2567
	21st to end	Day	55% 2 10% 19% 12% 1	2640
May	1st to 10th	Day	62% 1 8% 20% 8% 1	6357
	11th to 20th	Day	53% 3 11% 25% 8% 1	6322
	21st to end	Day	56% 2 10% 23% 9% 1	7449
June	1st to 10th	Day	56% 3 11% 19% 10% 1	3000
	11th to 20th	Day	50% 4 13% 23% 10% 1	3000
	21st to end	Day	54% 3 12% 21% 10%	3000
July	1st to 10th	Day	46% 4 12% 30% 8%	6745
	11th to 20th	Day	48% 5% 19% 22% 6%	6739
	21st to end	Day	38% 5% 18% 29% 10%	7088
August	1st to 10th	Day	39% 6% 22% 29% 4	4492
	11th to 20th	Day	57% 4 16% 18% 5%	4214
	21st to end	Day	39% 3 17% 30% 10%	4625
September	1st to 10th	Day	46% 4 16% 26% 8%	2400
	11th to 20th	Day	49% 4 16% 22% 8%	2350
	21st to end	Day	49% 4 12% 25% 10%	2123
October	1st to 10th	Day	52% 3 13% 26% 5% 1	3260
	11th to 20th	Day	51% 3 14% 24% 7%	3240
	21st to end	Day	51% 3 13% 18% 14%	3145
November	1st to 10th	Day	55% 4 11% 18% 11% 1	1645
	11th to 20th	Day	60% 3 11% 19% 7%	1680
	21st to end	Day	63% 3 9% 17% 8%	1680
December	1st to 10th	Day	58% 4 10% 20% 8% 1	2394
	11th to 20th	Day	60% 2 12% 20% 6% 1	2688
	21st to end	Day	52% 2 11% 23% 10% 3	3553
January	1st to 10th	Night	62% 2 6% 17% 11% 1	8831
	11th to 20th	Night	59% 3 10% 19% 8% 1	8880
	21st to end	Night	46% 2 7% 25% 19% 1	9343
February	1st to 10th	Night	52% 2 9% 19% 14% 4	2730
	11th to 20th	Night	57% 3 9% 17% 13% 1	2666
	21st to end	Night	54% 2 8% 19% 15% 2	2249
March	1st to 10th	Night	55% 1 6% 17% 17% 3	5285
	11th to 20th	Night	67% 2 5% 13% 12% 1	5058
	21st to end	Night	65% 2 5% 14% 10% 4	5388
April	1st to 10th	Night	60% 2 7% 15% 14% 3	2000
	11th to 20th	Night	53% 2 8% 21% 13% 3	1781
	21st to end	Night	55% 1 10% 16% 16% 1	1760
May	1st to 10th	Night	60% 2 7% 22% 7% 3	3620
	11th to 20th	Night	50% 2 12% 26% 9%	3597
	21st to end	Night	55% 2 11% 22% 9% 1	3492
June	1st to 10th	Night	56% 2 11% 22% 9% 1	1400
	11th to 20th	Night	52% 4 13% 20% 10% 1	1400
	21st to end	Night	57% 4 11% 19% 8% 1	1400
July	1st to 10th	Night	48% 4 13% 23% 10% 2	3125
	11th to 20th	Night	51% 4 16% 23% 5%	3118
	21st to end	Night	42% 4 18% 29% 7%	3426
August	1st to 10th	Night	48% 5% 18% 23% 6%	2638
	11th to 20th	Night	50% 5% 19% 20% 5%	2899
	21st to end	Night	47% 4 15% 24% 9%	3271
September	1st to 10th	Night	46% 3 15% 25% 10%	2000
	11th to 20th	Night	49% 3 15% 24% 8%	2049
	21st to end	Night	48% 3 12% 25% 12%	2276
October	1st to 10th	Night	52% 3 11% 26% 7% 1	3920
	11th to 20th	Night	53% 2 14% 23% 8%	3899
	21st to end	Night	52% 3 9% 24% 11% 1	4649
November	1st to 10th	Night	55% 3 12% 18% 11% 1	2873
	11th to 20th	Night	62% 2 13% 16% 7%	2940
	21st to end	Night	64% 2 11% 15% 8%	2940
December	1st to 10th	Night	56% 4 12% 19% 10%	5013
	11th to 20th	Night	58% 3 9% 21% 8% 1	5742
	21st to end	Night	52% 2 15% 21% 9% 1	7667

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	23% 10% 31% 22% 11% 3	220
	11th to 20th	Day	25% 10% 28% 20% 12% 4	220
	21st to end	Day	17% 10% 30% 28% 13% 2	310
February	1st to 10th	Day	16% 6% 37% 27% 10% 4	430
	11th to 20th	Day	18% 9% 30% 29% 12% 2	426
	21st to end	Day	20% 7% 30% 28% 11% 3	355
March	1st to 10th	Day	19% 10% 33% 28% 8% 2	496
	11th to 20th	Day	26% 8% 28% 25% 10% 4	528
	21st to end	Day	27% 12% 27% 22% 10% 2	550
April	1st to 10th	Day	30% 13% 29% 23% 5% 1	500
	11th to 20th	Day	25% 7% 30% 25% 10% 3	492
	21st to end	Day	31% 7% 26% 21% 11% 4	540
May	1st to 10th	Day	32% 5% 24% 25% 11% 3	703
	11th to 20th	Day	26% 7% 28% 25% 10% 4	724
	21st to end	Day	30% 8% 28% 23% 8% 2	790
June	1st to 10th	Day	29% 7% 25% 27% 11% 1	730
	11th to 20th	Day	28% 5% 26% 24% 13% 4	730
	21st to end	Day	29% 7% 25% 24% 12% 3	730
July	1st to 10th	Day	23% 6% 24% 30% 14% 3	720
	11th to 20th	Day	25% 4 22% 31% 16% 2	718
	21st to end	Day	28% 5% 21% 26% 17% 4	795
August	1st to 10th	Day	20% 3 20% 32% 19% 5%	693
	11th to 20th	Day	23% 7% 20% 30% 17% 3	519
	21st to end	Day	22% 5% 28% 27% 13% 5%	583
September	1st to 10th	Day	23% 10% 26% 26% 12% 3	530
	11th to 20th	Day	28% 9% 25% 24% 12% 2	530
	21st to end	Day	26% 8% 33% 20% 11% 2	487
October	1st to 10th	Day	24% 8% 33% 23% 9% 4	420
	11th to 20th	Day	31% 9% 27% 17% 12% 4	420
	21st to end	Day	32% 10% 23% 21% 10% 4	462
November	1st to 10th	Day	31% 13% 26% 24% 6% 1	425
	11th to 20th	Day	37% 9% 24% 23% 6% 2	430
	21st to end	Day	30% 11% 27% 23% 8% 1	430
December	1st to 10th	Day	21% 11% 26% 25% 13% 4	251
	11th to 20th	Day	25% 15% 32% 20% 6% 1	220
	21st to end	Day	24% 8% 34% 23% 9% 2	242
January	1st to 10th	Night	24% 7% 30% 29% 9% 1	950
	11th to 20th	Night	24% 11% 27% 27% 9% 1	950
	21st to end	Night	18% 10% 36% 27% 9%	1017
February	1st to 10th	Night	15% 10% 35% 27% 11% 1	840
	11th to 20th	Night	21% 9% 29% 30% 10% 1	823
	21st to end	Night	17% 9% 29% 28% 15% 2	692
March	1st to 10th	Night	18% 11% 32% 28% 11% 1	840
	11th to 20th	Night	22% 8% 32% 26% 10% 1	829
	21st to end	Night	23% 12% 27% 27% 9% 2	853
April	1st to 10th	Night	28% 8% 28% 26% 10%	600
	11th to 20th	Night	25% 6% 29% 28% 11% 1	594
	21st to end	Night	29% 5% 25% 29% 10% 2	600
May	1st to 10th	Night	29% 2 21% 33% 14% 2	600
	11th to 20th	Night	23% 4 24% 31% 16% 2	592
	21st to end	Night	27% 5% 22% 32% 13% 1	452
June	1st to 10th	Night	30% 4 18% 38% 11% 1	400
	11th to 20th	Night	28% 3 16% 32% 20% 1	400
	21st to end	Night	31% 2 15% 35% 17% 1	400
July	1st to 10th	Night	23% 4 16% 38% 17% 2	390
	11th to 20th	Night	22% 3 14% 44% 16% 1	388
	21st to end	Night	26% 2 13% 36% 21% 2	472
August	1st to 10th	Night	22% 2 13% 38% 22% 3	598
	11th to 20th	Night	23% 3 15% 36% 22% 1	592
	21st to end	Night	22% 3 18% 36% 20% 2	660
September	1st to 10th	Night	27% 5% 22% 30% 14% 2	600
	11th to 20th	Night	27% 6% 22% 33% 11% 2	649
	21st to end	Night	26% 7% 24% 32% 10%	800
October	1st to 10th	Night	29% 6% 27% 28% 9% 1	800
	11th to 20th	Night	35% 5% 21% 27% 13% 1	800
	21st to end	Night	31% 7% 23% 29% 9% 1	948
November	1st to 10th	Night	32% 9% 31% 22% 6% 1	930
	11th to 20th	Night	36% 10% 23% 24% 6% 1	950
	21st to end	Night	34% 9% 24% 27% 5% 1	950
December	1st to 10th	Night	27% 10% 30% 24% 7% 1	950
	11th to 20th	Night	27% 12% 34% 21% 6% 1	950
	21st to end	Night	26% 12% 28% 25% 8% 1	1045

Page generated at 2026-03-15 02:23:54. Version ac07

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