Captains Way
Clear Sky Chart
History

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

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	20% 10% 3 8% 5% 5% 5% 4 5% 7% 28%	131810
	Night	21% 11% 4 9% 5% 4 4 3 5% 6% 28%	129498
Transparency	Day	53% 7% 12% 18% 10% 1	135395
	Night	56% 6% 11% 17% 9% 1	133999
Seeing	Day	24% 11% 30% 24% 9% 1	19069
	Night	25% 12% 30% 24% 9% 1	26746

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	13% 14% 5% 14% 9% 7% 5% 3 4 5% 20%	4690
	11th to 20th	Day	18% 12% 6% 14% 7% 6% 6% 4 6% 6% 14%	4908
	21st to end	Day	14% 9% 3 10% 9% 8% 6% 4 6% 7% 26%	5781
February	1st to 10th	Day	20% 12% 4 10% 7% 6% 5% 5% 5% 7% 20%	1890
	11th to 20th	Day	16% 10% 4 10% 8% 6% 5% 5% 5% 6% 25%	1843
	21st to end	Day	12% 10% 3 8% 7% 6% 5% 4 6% 8% 30%	1588
March	1st to 10th	Day	22% 10% 3 10% 7% 6% 5% 4 4 5% 24%	4952
	11th to 20th	Day	16% 13% 3 7% 5% 5% 4 4 5% 6% 33%	4980
	21st to end	Day	27% 9% 3 9% 6% 5% 5% 4 5% 6% 22%	5466
April	1st to 10th	Day	25% 10% 3 7% 5% 4 4 4 5% 6% 27%	2386
	11th to 20th	Day	19% 9% 3 6% 5% 3 4 3 6% 7% 33%	2440
	21st to end	Day	22% 7% 2 6% 5% 4 4 3 5% 7% 34%	2600
May	1st to 10th	Day	27% 11% 4 10% 6% 5% 4 3 5% 6% 19%	5993
	11th to 20th	Day	25% 9% 3 8% 5% 4 4 3 5% 6% 28%	6318
	21st to end	Day	19% 10% 3 7% 4 4 5% 4 6% 9% 28%	6948
June	1st to 10th	Day	24% 10% 3 8% 4 4 5% 4 6% 7% 26%	2800
	11th to 20th	Day	21% 9% 3 6% 4 4 4 3 5% 7% 34%	2831
	21st to end	Day	27% 10% 3 8% 5% 4 4 4 4 6% 24%	3000
July	1st to 10th	Day	22% 11% 4 9% 6% 4 5% 4 6% 7% 21%	6498
	11th to 20th	Day	14% 12% 5% 10% 6% 5% 5% 4 6% 8% 27%	6360
	21st to end	Day	15% 8% 3 8% 5% 4 4 4 6% 8% 34%	6663
August	1st to 10th	Day	21% 11% 3 8% 5% 5% 4 4 5% 6% 27%	4235
	11th to 20th	Day	16% 9% 3 7% 5% 5% 5% 4 6% 9% 31%	4175
	21st to end	Day	9% 5% 2 6% 3 4 4 4 6% 7% 50%	4483
September	1st to 10th	Day	15% 7% 2 5% 4 3 5% 4 5% 7% 43%	2400
	11th to 20th	Day	17% 7% 1 5% 4 4 5% 3 4 6% 44%	2319
	21st to end	Day	17% 6% 2 6% 4 4 4 4 4 6% 43%	2139
October	1st to 10th	Day	16% 6% 3 6% 4 4 4 3 5% 7% 42%	2000
	11th to 20th	Day	18% 7% 3 7% 4 4 4 4 6% 8% 34%	2000
	21st to end	Day	20% 10% 3 7% 4 4 5% 3 5% 7% 33%	2200
November	1st to 10th	Day	21% 10% 3 8% 5% 4 4 3 5% 7% 31%	1728
	11th to 20th	Day	22% 11% 4 8% 5% 5% 5% 4 5% 7% 25%	1680
	21st to end	Day	21% 11% 4 8% 7% 6% 5% 4 5% 5% 26%	1680
December	1st to 10th	Day	23% 11% 4 11% 5% 5% 5% 4 4 5% 23%	2690
	11th to 20th	Day	30% 9% 2 7% 4 5% 5% 4 4 5% 25%	3076
	21st to end	Day	22% 10% 5% 10% 4 4 4 3 4 7% 27%	4070
January	1st to 10th	Night	15% 13% 5% 17% 8% 6% 4 4 5% 5% 18%	8234
	11th to 20th	Night	22% 12% 5% 14% 6% 5% 5% 4 5% 5% 16%	7978
	21st to end	Night	13% 12% 4 14% 10% 6% 6% 3 5% 6% 21%	8400
February	1st to 10th	Night	20% 13% 4 10% 7% 5% 5% 5% 5% 5% 20%	2730
	11th to 20th	Night	17% 9% 4 10% 7% 6% 5% 5% 7% 6% 24%	2663
	21st to end	Night	13% 12% 4 10% 7% 6% 6% 4 6% 6% 28%	2215
March	1st to 10th	Night	25% 11% 4 9% 6% 5% 4 3 4 5% 23%	4933
	11th to 20th	Night	19% 12% 4 9% 5% 4 4 3 5% 6% 27%	4979
	21st to end	Night	31% 10% 4 9% 4 3 3 2 4 4 25%	5466
April	1st to 10th	Night	25% 11% 4 6% 4 4 4 4 4 5% 28%	2013
	11th to 20th	Night	23% 9% 3 6% 5% 4 4 3 5% 7% 33%	1908
	21st to end	Night	25% 10% 3 7% 4 3 4 3 5% 5% 33%	1800
May	1st to 10th	Night	29% 11% 4 9% 5% 4 4 3 4 4 24%	3949
	11th to 20th	Night	28% 10% 2 6% 4 4 4 2 4 6% 29%	3596
	21st to end	Night	18% 15% 4 8% 4 4 4 3 4 5% 31%	3948
June	1st to 10th	Night	28% 11% 2 6% 4 3 4 3 5% 5% 29%	1600
	11th to 20th	Night	22% 9% 3 7% 4 4 4 3 6% 5% 33%	1577
	21st to end	Night	29% 12% 3 7% 5% 4 4 3 4 5% 24%	1400
July	1st to 10th	Night	20% 13% 5% 10% 6% 4 5% 4 5% 6% 24%	3426
	11th to 20th	Night	19% 12% 4 11% 6% 4 4 3 4 6% 27%	3620
	21st to end	Night	18% 9% 3 8% 4 4 4 3 4 7% 37%	4197
August	1st to 10th	Night	20% 10% 4 9% 5% 3 3 3 4 6% 33%	2915
	11th to 20th	Night	16% 8% 4 8% 4 4 4 3 6% 6% 36%	2872
	21st to end	Night	10% 6% 2 6% 2 4 4 3 4 7% 51%	3413
September	1st to 10th	Night	15% 7% 3 5% 3 3 4 4 6% 6% 43%	2000
	11th to 20th	Night	17% 7% 2 5% 3 3 4 3 5% 6% 45%	2079
	21st to end	Night	21% 8% 3 5% 4 3 4 3 4 6% 38%	2260
October	1st to 10th	Night	17% 6% 2 6% 3 4 3 3 5% 7% 43%	2400
	11th to 20th	Night	20% 6% 3 5% 4 4 4 4 5% 7% 37%	2400
	21st to end	Night	24% 9% 2 5% 3 3 4 4 5% 6% 34%	2640
November	1st to 10th	Night	21% 9% 3 6% 5% 4 4 3 5% 6% 35%	2784
	11th to 20th	Night	20% 11% 4 8% 5% 4 4 4 5% 7% 28%	2940
	21st to end	Night	21% 10% 3 8% 5% 5% 5% 4 5% 7% 27%	2940
December	1st to 10th	Night	17% 11% 5% 13% 5% 5% 5% 4 5% 6% 24%	4720
	11th to 20th	Night	26% 11% 3 8% 4 4 5% 3 5% 5% 27%	5353
	21st to end	Night	25% 10% 3 9% 4 4 4 3 4 5% 29%	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	64% 6% 14% 12% 4	4691
	11th to 20th	Day	67% 7% 12% 11% 4	4938
	21st to end	Day	56% 6% 12% 12% 13% 2	5781
February	1st to 10th	Day	63% 5% 12% 12% 7% 1	1890
	11th to 20th	Day	58% 7% 13% 16% 7% 1	1851
	21st to end	Day	49% 8% 12% 18% 10% 2	1588
March	1st to 10th	Day	61% 5% 9% 13% 8% 3	4956
	11th to 20th	Day	48% 9% 15% 20% 8% 1	4980
	21st to end	Day	60% 5% 8% 15% 11% 1	5466
April	1st to 10th	Day	55% 7% 10% 13% 13% 3	2386
	11th to 20th	Day	48% 6% 11% 20% 13% 2	2440
	21st to end	Day	47% 6% 12% 19% 12% 3	2600
May	1st to 10th	Day	64% 9% 10% 12% 5% 1	6004
	11th to 20th	Day	55% 7% 10% 20% 7% 1	6322
	21st to end	Day	48% 9% 15% 18% 9% 1	6948
June	1st to 10th	Day	54% 9% 10% 19% 8% 1	2800
	11th to 20th	Day	48% 8% 13% 18% 12% 2	2831
	21st to end	Day	59% 8% 8% 14% 9% 1	3000
July	1st to 10th	Day	60% 6% 12% 12% 9% 1	6428
	11th to 20th	Day	53% 6% 10% 22% 9%	6284
	21st to end	Day	45% 7% 14% 23% 11% 1	6473
August	1st to 10th	Day	56% 7% 11% 17% 9% 1	4222
	11th to 20th	Day	47% 7% 15% 23% 7%	4214
	21st to end	Day	32% 7% 11% 30% 19% 1	4483
September	1st to 10th	Day	38% 7% 14% 24% 16% 2	2400
	11th to 20th	Day	40% 7% 10% 25% 17% 2	2319
	21st to end	Day	41% 7% 10% 24% 18% 1	2139
October	1st to 10th	Day	41% 6% 12% 28% 13% 1	3260
	11th to 20th	Day	38% 5% 11% 25% 20% 1	3240
	21st to end	Day	44% 5% 15% 21% 12% 3	3538
November	1st to 10th	Day	53% 6% 11% 20% 9% 1	1728
	11th to 20th	Day	57% 7% 14% 15% 6% 1	1680
	21st to end	Day	60% 5% 13% 16% 6% 1	1680
December	1st to 10th	Day	61% 6% 11% 18% 3	2690
	11th to 20th	Day	61% 5% 11% 14% 9%	3075
	21st to end	Day	58% 6% 16% 13% 7% 1	4070
January	1st to 10th	Night	65% 6% 11% 14% 4	8234
	11th to 20th	Night	67% 7% 11% 11% 4	8022
	21st to end	Night	61% 6% 12% 12% 9% 1	8400
February	1st to 10th	Night	66% 6% 10% 10% 7% 1	2730
	11th to 20th	Night	59% 5% 12% 16% 7% 1	2666
	21st to end	Night	54% 7% 12% 18% 8% 1	2215
March	1st to 10th	Night	63% 4 8% 11% 12% 2	4942
	11th to 20th	Night	55% 7% 12% 18% 7% 1	4980
	21st to end	Night	62% 4 7% 17% 10% 1	5466
April	1st to 10th	Night	56% 6% 9% 14% 12% 3	2013
	11th to 20th	Night	51% 5% 10% 19% 14% 2	1908
	21st to end	Night	53% 4 11% 18% 11% 3	1800
May	1st to 10th	Night	63% 7% 10% 12% 8% 1	3955
	11th to 20th	Night	56% 7% 8% 20% 7% 2	3597
	21st to end	Night	55% 6% 11% 19% 8% 1	3949
June	1st to 10th	Night	56% 7% 9% 20% 8%	1600
	11th to 20th	Night	51% 6% 10% 21% 11% 1	1577
	21st to end	Night	61% 6% 9% 13% 9% 1	1400
July	1st to 10th	Night	61% 5% 11% 14% 8% 1	3387
	11th to 20th	Night	58% 5% 8% 16% 12% 1	3572
	21st to end	Night	48% 6% 10% 22% 13% 1	4073
August	1st to 10th	Night	54% 6% 12% 20% 9%	2903
	11th to 20th	Night	46% 8% 15% 23% 7%	2899
	21st to end	Night	32% 5% 14% 27% 21%	3412
September	1st to 10th	Night	39% 8% 10% 25% 16% 2	2000
	11th to 20th	Night	40% 5% 8% 29% 16% 1	2079
	21st to end	Night	47% 4 8% 25% 15% 1	2260
October	1st to 10th	Night	44% 5% 12% 25% 13% 1	3920
	11th to 20th	Night	37% 5% 12% 27% 19%	3899
	21st to end	Night	43% 4 12% 24% 16% 1	4252
November	1st to 10th	Night	50% 7% 13% 18% 11% 1	2784
	11th to 20th	Night	56% 7% 13% 16% 8%	2940
	21st to end	Night	57% 7% 15% 15% 5%	2940
December	1st to 10th	Night	60% 6% 11% 19% 4	4720
	11th to 20th	Night	60% 4 12% 15% 9% 1	5355
	21st to end	Night	58% 6% 12% 16% 8%	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	26% 20% 38% 12% 4	430
	11th to 20th	Day	28% 18% 33% 15% 5%	430
	21st to end	Day	20% 18% 41% 19% 3	473
February	1st to 10th	Day	27% 16% 34% 17% 5%	430
	11th to 20th	Day	23% 23% 33% 18% 3	426
	21st to end	Day	17% 18% 37% 24% 4 1	355
March	1st to 10th	Day	24% 19% 35% 20% 2	508
	11th to 20th	Day	19% 21% 35% 19% 5% 1	500
	21st to end	Day	27% 15% 35% 17% 5% 1	550
April	1st to 10th	Day	30% 16% 32% 18% 4	500
	11th to 20th	Day	23% 11% 42% 19% 5% 1	492
	21st to end	Day	23% 12% 30% 26% 9% 1	500
May	1st to 10th	Day	27% 12% 32% 23% 5% 1	545
	11th to 20th	Day	22% 7% 32% 29% 8% 2	724
	21st to end	Day	27% 7% 29% 28% 7% 1	790
June	1st to 10th	Day	28% 8% 26% 27% 11% 1	730
	11th to 20th	Day	23% 6% 29% 28% 12% 1	730
	21st to end	Day	33% 4 22% 27% 13% 1	730
July	1st to 10th	Day	25% 4 24% 32% 14% 1	720
	11th to 20th	Day	23% 6% 21% 33% 16% 2	718
	21st to end	Day	23% 4 23% 35% 14% 1	684
August	1st to 10th	Day	18% 4 23% 38% 15% 3	526
	11th to 20th	Day	19% 6% 24% 27% 19% 5%	519
	21st to end	Day	16% 5% 23% 32% 19% 4	583
September	1st to 10th	Day	17% 4 28% 34% 15% 2	530
	11th to 20th	Day	20% 8% 27% 24% 15% 6%	530
	21st to end	Day	20% 6% 29% 27% 16% 2	496
October	1st to 10th	Day	17% 9% 30% 27% 14% 3	420
	11th to 20th	Day	19% 13% 33% 22% 10% 3	420
	21st to end	Day	24% 14% 33% 21% 7% 1	462
November	1st to 10th	Day	23% 15% 32% 23% 7% 1	425
	11th to 20th	Day	28% 23% 27% 16% 6%	430
	21st to end	Day	28% 17% 36% 14% 3 1	430
December	1st to 10th	Day	30% 18% 30% 18% 3	430
	11th to 20th	Day	28% 27% 28% 14% 2	430
	21st to end	Day	26% 21% 33% 16% 4	473
January	1st to 10th	Night	25% 20% 35% 16% 3	950
	11th to 20th	Night	27% 18% 33% 17% 5%	903
	21st to end	Night	22% 22% 37% 16% 3	924
February	1st to 10th	Night	28% 17% 32% 20% 2	840
	11th to 20th	Night	22% 22% 37% 16% 3	823
	21st to end	Night	18% 16% 38% 22% 5%	692
March	1st to 10th	Night	24% 16% 39% 17% 4	809
	11th to 20th	Night	23% 15% 31% 24% 8% 1	800
	21st to end	Night	25% 15% 32% 21% 6%	880
April	1st to 10th	Night	33% 11% 31% 21% 5%	613
	11th to 20th	Night	26% 7% 40% 20% 6% 1	594
	21st to end	Night	29% 9% 28% 25% 9% 1	600
May	1st to 10th	Night	31% 7% 29% 25% 7% 1	600
	11th to 20th	Night	29% 6% 25% 29% 10% 2	592
	21st to end	Night	22% 6% 28% 32% 10% 2	649
June	1st to 10th	Night	32% 6% 22% 30% 10%	600
	11th to 20th	Night	24% 5% 23% 36% 11% 1	577
	21st to end	Night	33% 4 16% 35% 11% 2	400
July	1st to 10th	Night	22% 4 21% 38% 15% 1	496
	11th to 20th	Night	23% 4 19% 33% 18% 3	582
	21st to end	Night	21% 4 18% 36% 20%	656
August	1st to 10th	Night	18% 3 19% 34% 24% 3	598
	11th to 20th	Night	20% 3 21% 31% 22% 3	592
	21st to end	Night	17% 4 23% 34% 19% 3	660
September	1st to 10th	Night	18% 5% 26% 33% 17% 2	600
	11th to 20th	Night	20% 7% 23% 29% 18% 3	679
	21st to end	Night	24% 6% 25% 30% 13% 2	800
October	1st to 10th	Night	21% 8% 28% 31% 11% 1	800
	11th to 20th	Night	21% 11% 33% 23% 11% 2	800
	21st to end	Night	27% 12% 32% 23% 6%	880
November	1st to 10th	Night	25% 13% 33% 22% 5% 1	912
	11th to 20th	Night	26% 20% 29% 19% 6%	950
	21st to end	Night	26% 19% 31% 17% 6%	950
December	1st to 10th	Night	30% 17% 33% 16% 4	950
	11th to 20th	Night	28% 23% 32% 14% 3	950
	21st to end	Night	28% 17% 34% 18% 3	1045

Page generated at 2026-02-28 02:40:20. Version ac07

Copyright © 2026 Attilla Danko.