Four Corners Madawaska Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Four Corners Madawaska Observatory clear sky chart from 2005-11-06 to 2026-02-01.

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	15% 12% 4 9% 5% 5% 4 3 5% 6% 30%	128272
	Night	14% 13% 5% 10% 6% 5% 4 3 5% 6% 28%	123717
Transparency	Day	53% 6% 10% 20% 10% 1	131814
	Night	55% 7% 11% 18% 9% 1	128262
Seeing	Day	23% 18% 32% 18% 7% 2	16077
	Night	22% 16% 32% 22% 8% 1	25149

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	11% 15% 6% 15% 10% 7% 7% 3 5% 5% 16%	3677
	11th to 20th	Day	9% 18% 7% 17% 9% 7% 5% 3 5% 5% 14%	3650
	21st to end	Day	11% 19% 10% 15% 7% 6% 4 3 3 4 18%	4500
February	1st to 10th	Day	10% 17% 6% 16% 10% 6% 4 4 4 5% 20%	1800
	11th to 20th	Day	10% 15% 6% 14% 7% 6% 5% 4 4 5% 23%	1753
	21st to end	Day	15% 17% 5% 11% 6% 6% 6% 4 5% 4 21%	1547
March	1st to 10th	Day	16% 17% 5% 11% 6% 5% 3 2 5% 6% 24%	4787
	11th to 20th	Day	10% 14% 5% 12% 6% 5% 5% 4 6% 7% 26%	4980
	21st to end	Day	15% 15% 6% 10% 4 4 3 2 3 4 34%	5551
April	1st to 10th	Day	19% 14% 5% 9% 4 5% 4 2 4 5% 28%	2400
	11th to 20th	Day	21% 13% 3 7% 4 4 4 3 3 5% 34%	2404
	21st to end	Day	21% 12% 3 8% 4 4 3 3 5% 4 33%	2600
May	1st to 10th	Day	20% 10% 3 9% 5% 4 4 3 5% 6% 32%	6209
	11th to 20th	Day	15% 11% 3 8% 5% 4 4 3 5% 6% 36%	6318
	21st to end	Day	20% 10% 3 7% 5% 4 4 3 5% 5% 34%	6949
June	1st to 10th	Day	20% 9% 3 7% 6% 5% 5% 3 6% 7% 29%	2800
	11th to 20th	Day	15% 6% 3 6% 5% 4 5% 4 6% 8% 36%	2806
	21st to end	Day	17% 8% 3 6% 6% 5% 5% 5% 5% 8% 33%	3000
July	1st to 10th	Day	14% 7% 2 7% 5% 5% 5% 5% 7% 9% 33%	6499
	11th to 20th	Day	11% 6% 2 6% 5% 4 5% 4 6% 8% 43%	6360
	21st to end	Day	8% 5% 2 6% 4 5% 4 4 7% 9% 45%	6926
August	1st to 10th	Day	14% 7% 3 8% 6% 6% 5% 5% 6% 8% 32%	4246
	11th to 20th	Day	17% 7% 2 6% 5% 5% 5% 5% 7% 7% 33%	4174
	21st to end	Day	10% 5% 2 6% 5% 5% 6% 5% 8% 10% 38%	4429
September	1st to 10th	Day	15% 8% 3 6% 4 4 5% 4 6% 8% 39%	2400
	11th to 20th	Day	14% 7% 2 6% 4 4 3 3 5% 7% 44%	2389
	21st to end	Day	19% 9% 2 7% 5% 5% 4 3 5% 6% 34%	2094
October	1st to 10th	Day	18% 11% 3 7% 5% 5% 4 3 5% 6% 34%	2000
	11th to 20th	Day	21% 16% 3 8% 5% 5% 4 3 5% 5% 25%	2000
	21st to end	Day	25% 16% 5% 10% 5% 4 3 2 3 5% 21%	2149
November	1st to 10th	Day	15% 15% 5% 8% 5% 5% 4 3 6% 6% 29%	1721
	11th to 20th	Day	14% 17% 6% 12% 6% 5% 5% 4 3 5% 22%	1680
	21st to end	Day	18% 19% 8% 13% 7% 6% 4 3 4 4 15%	1680
December	1st to 10th	Day	13% 24% 10% 15% 6% 5% 5% 3 4 4 11%	2680
	11th to 20th	Day	14% 21% 8% 14% 7% 4 4 2 3 3 20%	3066
	21st to end	Day	19% 21% 8% 14% 7% 3 3 2 3 5% 17%	4048
January	1st to 10th	Night	11% 18% 9% 17% 9% 6% 5% 3 4 5% 14%	6489
	11th to 20th	Night	7% 15% 6% 19% 10% 8% 7% 4 5% 5% 14%	6455
	21st to end	Night	10% 17% 9% 16% 6% 7% 5% 4 5% 5% 16%	6680
February	1st to 10th	Night	11% 17% 7% 13% 9% 6% 5% 4 5% 6% 19%	2601
	11th to 20th	Night	10% 16% 5% 13% 7% 6% 5% 3 5% 5% 25%	2533
	21st to end	Night	10% 17% 4 12% 7% 6% 5% 4 5% 6% 24%	2082
March	1st to 10th	Night	15% 14% 4 12% 6% 5% 4 3 4 5% 27%	5052
	11th to 20th	Night	9% 13% 5% 10% 6% 5% 6% 5% 7% 8% 26%	4979
	21st to end	Night	15% 12% 4 11% 5% 4 4 4 5% 6% 30%	5380
April	1st to 10th	Night	18% 16% 4 9% 4 4 4 3 4 5% 30%	2000
	11th to 20th	Night	18% 10% 4 7% 5% 4 3 3 5% 6% 36%	1962
	21st to end	Night	17% 12% 4 9% 6% 5% 5% 3 5% 6% 31%	1800
May	1st to 10th	Night	20% 10% 2 6% 4 4 4 4 5% 7% 32%	3732
	11th to 20th	Night	15% 8% 3 6% 4 3 4 3 5% 7% 43%	3575
	21st to end	Night	18% 8% 3 8% 4 5% 5% 4 4 6% 35%	3926
June	1st to 10th	Night	16% 8% 3 7% 5% 4 5% 4 6% 9% 34%	1600
	11th to 20th	Night	14% 6% 2 6% 3 5% 3 4 5% 8% 43%	1583
	21st to end	Night	16% 8% 3 6% 5% 4 4 5% 6% 6% 37%	1400
July	1st to 10th	Night	13% 7% 3 7% 6% 5% 5% 4 7% 7% 38%	3457
	11th to 20th	Night	12% 7% 2 6% 4 5% 4 3 6% 6% 46%	3600
	21st to end	Night	8% 5% 2 5% 4 3 5% 3 5% 8% 50%	3926
August	1st to 10th	Night	11% 5% 2 6% 4 4 4 4 7% 10% 44%	2899
	11th to 20th	Night	15% 7% 2 6% 4 4 4 4 5% 7% 42%	2875
	21st to end	Night	13% 5% 2 4 4 4 4 4 7% 9% 45%	3435
September	1st to 10th	Night	11% 6% 2 5% 4 4 4 4 6% 8% 47%	2000
	11th to 20th	Night	13% 7% 3 5% 4 3 3 3 4 7% 50%	2009
	21st to end	Night	16% 9% 3 7% 4 4 4 3 4 6% 40%	2305
October	1st to 10th	Night	18% 9% 3 6% 4 3 4 3 5% 7% 40%	2400
	11th to 20th	Night	19% 14% 3 8% 5% 4 5% 3 4 6% 29%	2400
	21st to end	Night	22% 15% 4 9% 5% 5% 4 3 4 5% 24%	2690
November	1st to 10th	Night	15% 15% 4 8% 6% 4 4 4 5% 5% 29%	2794
	11th to 20th	Night	15% 14% 5% 11% 7% 5% 5% 3 5% 6% 24%	2940
	21st to end	Night	18% 19% 6% 12% 8% 5% 4 3 4 5% 16%	2940
December	1st to 10th	Night	15% 21% 8% 14% 8% 6% 5% 3 4 5% 11%	4720
	11th to 20th	Night	14% 20% 7% 13% 6% 5% 4 3 4 5% 19%	5348
	21st to end	Night	20% 20% 6% 14% 7% 4 4 2 3 4 14%	7150

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	69% 7% 8% 10% 6%	3678
	11th to 20th	Day	71% 6% 8% 8% 7% 1	3680
	21st to end	Day	70% 4 5% 11% 8% 2	4500
February	1st to 10th	Day	67% 6% 8% 13% 6% 1	1800
	11th to 20th	Day	63% 5% 9% 12% 9% 1	1762
	21st to end	Day	63% 5% 8% 12% 10% 1	1547
March	1st to 10th	Day	61% 5% 10% 9% 14% 2	4790
	11th to 20th	Day	55% 7% 14% 15% 7% 2	4980
	21st to end	Day	54% 4 7% 19% 14% 3	5551
April	1st to 10th	Day	58% 4 8% 18% 10% 3	2400
	11th to 20th	Day	53% 5% 7% 21% 13% 1	2404
	21st to end	Day	54% 5% 7% 17% 13% 3	2600
May	1st to 10th	Day	51% 7% 9% 19% 9% 5%	6219
	11th to 20th	Day	47% 7% 10% 21% 15% 1	6322
	21st to end	Day	51% 7% 9% 18% 12% 2	6949
June	1st to 10th	Day	52% 8% 10% 19% 11% 1	2800
	11th to 20th	Day	44% 7% 11% 23% 13% 2	2806
	21st to end	Day	48% 7% 12% 20% 11% 1	3000
July	1st to 10th	Day	43% 7% 14% 25% 9%	6430
	11th to 20th	Day	36% 7% 12% 33% 12%	6285
	21st to end	Day	33% 7% 15% 34% 12%	6728
August	1st to 10th	Day	47% 8% 13% 24% 8%	4232
	11th to 20th	Day	45% 9% 15% 25% 6% 1	4213
	21st to end	Day	37% 7% 14% 32% 10%	4429
September	1st to 10th	Day	41% 8% 15% 26% 10% 1	2400
	11th to 20th	Day	39% 6% 13% 28% 14%	2389
	21st to end	Day	50% 7% 11% 23% 9%	2094
October	1st to 10th	Day	49% 7% 10% 25% 8%	3260
	11th to 20th	Day	55% 5% 9% 19% 10% 1	3240
	21st to end	Day	63% 6% 11% 16% 4 1	3451
November	1st to 10th	Day	55% 7% 13% 19% 6% 1	1721
	11th to 20th	Day	63% 7% 10% 12% 7% 1	1680
	21st to end	Day	73% 6% 8% 9% 4 1	1680
December	1st to 10th	Day	76% 6% 7% 8% 2	2680
	11th to 20th	Day	70% 5% 5% 11% 8% 1	3066
	21st to end	Day	72% 4 5% 13% 6%	4048
January	1st to 10th	Night	72% 6% 8% 9% 5%	6489
	11th to 20th	Night	68% 10% 7% 8% 6% 1	6500
	21st to end	Night	68% 7% 6% 9% 10% 1	6680
February	1st to 10th	Night	65% 5% 11% 12% 6% 1	2601
	11th to 20th	Night	61% 5% 9% 16% 8% 1	2535
	21st to end	Night	59% 6% 9% 18% 7% 1	2082
March	1st to 10th	Night	58% 5% 9% 13% 10% 4	5062
	11th to 20th	Night	51% 9% 16% 15% 7% 1	4980
	21st to end	Night	52% 6% 9% 18% 13% 2	5380
April	1st to 10th	Night	57% 4 8% 18% 12% 2	2000
	11th to 20th	Night	50% 5% 8% 23% 14% 1	1962
	21st to end	Night	55% 4 8% 16% 15% 2	1800
May	1st to 10th	Night	49% 8% 9% 20% 10% 4	3738
	11th to 20th	Night	39% 9% 13% 22% 15% 2	3576
	21st to end	Night	47% 9% 10% 21% 12% 1	3927
June	1st to 10th	Night	46% 8% 12% 21% 13% 1	1600
	11th to 20th	Night	38% 7% 13% 26% 15% 1	1583
	21st to end	Night	45% 8% 15% 20% 12%	1400
July	1st to 10th	Night	42% 9% 16% 21% 12%	3417
	11th to 20th	Night	36% 7% 12% 33% 11%	3552
	21st to end	Night	32% 6% 11% 37% 13%	3809
August	1st to 10th	Night	35% 8% 17% 27% 13% 1	2889
	11th to 20th	Night	39% 9% 18% 26% 8% 1	2902
	21st to end	Night	35% 7% 15% 31% 10% 2	3435
September	1st to 10th	Night	35% 7% 17% 28% 12% 1	2000
	11th to 20th	Night	36% 5% 13% 32% 13%	2009
	21st to end	Night	45% 6% 13% 25% 10%	2305
October	1st to 10th	Night	39% 5% 13% 28% 14%	3920
	11th to 20th	Night	51% 5% 13% 19% 11% 1	3899
	21st to end	Night	55% 6% 18% 16% 5%	4338
November	1st to 10th	Night	56% 6% 13% 17% 7%	2794
	11th to 20th	Night	60% 7% 11% 15% 6% 1	2940
	21st to end	Night	70% 6% 9% 11% 3	2940
December	1st to 10th	Night	74% 6% 10% 7% 2	4720
	11th to 20th	Night	68% 5% 6% 11% 9%	5348
	21st to end	Night	75% 4 5% 10% 6%	7150

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	20% 24% 40% 12% 3 1	220
	11th to 20th	Day	29% 16% 36% 15% 2 2	220
	21st to end	Day	24% 23% 32% 17% 4	349
February	1st to 10th	Day	30% 28% 32% 8% 2 1	300
	11th to 20th	Day	28% 31% 34% 6% 1	300
	21st to end	Day	34% 22% 34% 9% 1	311
March	1st to 10th	Day	26% 23% 36% 14% 2	500
	11th to 20th	Day	25% 21% 36% 14% 3 1	500
	21st to end	Day	29% 25% 29% 13% 4	550
April	1st to 10th	Day	28% 22% 32% 13% 5% 1	500
	11th to 20th	Day	35% 22% 21% 13% 6% 2	492
	21st to end	Day	30% 19% 33% 12% 5% 1	500
May	1st to 10th	Day	24% 20% 30% 18% 7% 2	503
	11th to 20th	Day	21% 19% 31% 20% 8% 2	527
	21st to end	Day	20% 19% 30% 20% 9% 2	573
June	1st to 10th	Day	23% 14% 38% 19% 5% 1	530
	11th to 20th	Day	18% 15% 36% 20% 10% 2	536
	21st to end	Day	21% 15% 36% 21% 7% 1	730
July	1st to 10th	Day	15% 10% 37% 28% 8% 2	587
	11th to 20th	Day	13% 14% 35% 26% 10% 2	524
	21st to end	Day	12% 14% 34% 28% 10% 2	576
August	1st to 10th	Day	14% 11% 29% 30% 11% 5%	526
	11th to 20th	Day	15% 9% 28% 30% 13% 5%	519
	21st to end	Day	15% 12% 34% 23% 11% 4	583
September	1st to 10th	Day	18% 12% 32% 21% 12% 5%	530
	11th to 20th	Day	15% 9% 25% 25% 17% 9%	530
	21st to end	Day	21% 16% 26% 21% 12% 4	530
October	1st to 10th	Day	23% 18% 25% 20% 10% 3	530
	11th to 20th	Day	29% 25% 27% 14% 4 1	530
	21st to end	Day	34% 19% 28% 15% 3	554
November	1st to 10th	Day	31% 22% 31% 12% 4	295
	11th to 20th	Day	30% 22% 33% 11% 4	220
	21st to end	Day	31% 23% 38% 5% 3	220
December	1st to 10th	Day	28% 23% 33% 15% 1	220
	11th to 20th	Day	34% 26% 28% 10% 1 1	220
	21st to end	Day	32% 23% 26% 15% 3 1	242
January	1st to 10th	Night	23% 22% 36% 16% 3 1	840
	11th to 20th	Night	25% 20% 32% 18% 5% 1	840
	21st to end	Night	17% 18% 36% 22% 6% 1	924
February	1st to 10th	Night	20% 22% 39% 15% 3	801
	11th to 20th	Night	20% 21% 39% 16% 3	783
	21st to end	Night	22% 23% 33% 20% 2	660
March	1st to 10th	Night	21% 23% 35% 18% 3	800
	11th to 20th	Night	20% 20% 37% 17% 5% 1	800
	21st to end	Night	20% 18% 35% 21% 6%	880
April	1st to 10th	Night	27% 17% 33% 19% 4	800
	11th to 20th	Night	24% 20% 28% 18% 9%	778
	21st to end	Night	22% 15% 30% 22% 11%	600
May	1st to 10th	Night	23% 10% 28% 29% 9% 1	460
	11th to 20th	Night	21% 12% 32% 27% 8%	394
	21st to end	Night	16% 12% 34% 28% 10%	433
June	1st to 10th	Night	18% 10% 36% 29% 6% 1	400
	11th to 20th	Night	18% 11% 30% 31% 11%	400
	21st to end	Night	20% 10% 29% 32% 10% 1	400
July	1st to 10th	Night	11% 7% 33% 35% 13% 1	390
	11th to 20th	Night	15% 7% 30% 33% 15% 1	388
	21st to end	Night	9% 8% 37% 33% 12% 1	438
August	1st to 10th	Night	11% 5% 26% 36% 19% 2	581
	11th to 20th	Night	11% 5% 25% 36% 21% 3	594
	21st to end	Night	15% 8% 29% 31% 14% 2	781
September	1st to 10th	Night	14% 10% 31% 29% 16% 2	800
	11th to 20th	Night	16% 9% 26% 27% 18% 4	800
	21st to end	Night	21% 11% 24% 25% 17% 2	800
October	1st to 10th	Night	24% 13% 28% 23% 11% 2	800
	11th to 20th	Night	26% 18% 32% 17% 7% 1	800
	21st to end	Night	30% 17% 29% 20% 4	880
November	1st to 10th	Night	27% 18% 31% 19% 5%	820
	11th to 20th	Night	24% 23% 31% 15% 7%	840
	21st to end	Night	31% 19% 29% 17% 3	840
December	1st to 10th	Night	28% 21% 34% 12% 5%	840
	11th to 20th	Night	25% 23% 33% 16% 3 1	840
	21st to end	Night	33% 19% 29% 15% 3 1	924

Page generated at 2026-01-29 01:21:41. Version ac07

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