Charlos Cove
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Charlos Cove clear sky chart from 2005-11-06 to 2026-01-17.

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% 11% 4 9% 5% 5% 5% 4 5% 7% 26%	127895
	Night	20% 12% 4 9% 5% 4 4 3 5% 6% 27%	124028
Transparency	Day	57% 6% 10% 17% 9% 1	131392
	Night	57% 6% 10% 18% 9% 1	128626
Seeing	Day	27% 10% 28% 24% 9% 2	19196
	Night	29% 10% 28% 24% 9% 1	26761

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% 17% 7% 19% 7% 6% 5% 3 4 4 16%	3696
	11th to 20th	Day	12% 13% 9% 13% 7% 5% 4 4 5% 6% 23%	3639
	21st to end	Day	13% 11% 5% 10% 5% 5% 5% 4 6% 7% 30%	4224
February	1st to 10th	Day	20% 11% 4 10% 6% 5% 5% 4 7% 6% 22%	1800
	11th to 20th	Day	17% 9% 4 10% 7% 7% 6% 4 6% 5% 24%	1753
	21st to end	Day	13% 13% 4 8% 6% 5% 5% 4 6% 7% 28%	1631
March	1st to 10th	Day	21% 11% 4 11% 7% 5% 4 3 4 5% 25%	4555
	11th to 20th	Day	13% 17% 6% 11% 6% 4 5% 3 5% 7% 24%	4980
	21st to end	Day	27% 14% 4 11% 6% 5% 4 3 4 5% 18%	5727
April	1st to 10th	Day	24% 11% 4 8% 5% 4 4 4 4 6% 26%	2400
	11th to 20th	Day	23% 11% 3 7% 4 4 5% 3 4 5% 31%	2374
	21st to end	Day	23% 11% 4 7% 4 4 4 3 4 5% 29%	2537
May	1st to 10th	Day	25% 15% 4 8% 4 4 4 3 5% 6% 22%	6345
	11th to 20th	Day	23% 11% 3 7% 5% 5% 5% 3 4 6% 28%	6318
	21st to end	Day	19% 12% 3 7% 4 4 4 3 5% 8% 28%	6948
June	1st to 10th	Day	27% 10% 3 7% 4 5% 5% 4 6% 7% 22%	2800
	11th to 20th	Day	20% 9% 3 8% 6% 4 4 4 5% 7% 30%	2800
	21st to end	Day	27% 13% 3 8% 5% 3 4 4 6% 6% 20%	2800
July	1st to 10th	Day	18% 10% 4 11% 7% 6% 6% 5% 6% 8% 20%	6360
	11th to 20th	Day	15% 8% 3 9% 6% 7% 7% 6% 7% 8% 24%	6360
	21st to end	Day	14% 8% 3 7% 5% 4 5% 5% 7% 9% 33%	6927
August	1st to 10th	Day	18% 11% 4 9% 5% 5% 5% 4 6% 7% 26%	4433
	11th to 20th	Day	18% 7% 3 8% 5% 5% 5% 5% 7% 9% 28%	4157
	21st to end	Day	11% 7% 3 6% 4 6% 5% 3 5% 7% 43%	4312
September	1st to 10th	Day	17% 7% 3 8% 4 4 4 4 5% 8% 36%	2400
	11th to 20th	Day	19% 8% 3 6% 4 4 5% 4 5% 7% 35%	2400
	21st to end	Day	19% 8% 2 6% 4 5% 4 4 5% 6% 36%	2124
October	1st to 10th	Day	18% 9% 3 7% 5% 4 5% 4 5% 7% 34%	2000
	11th to 20th	Day	21% 8% 3 7% 5% 5% 6% 5% 6% 8% 28%	2000
	21st to end	Day	21% 10% 4 9% 6% 5% 5% 4 6% 6% 24%	2068
November	1st to 10th	Day	23% 10% 3 9% 4 4 5% 3 6% 6% 26%	1831
	11th to 20th	Day	24% 12% 4 9% 6% 4 5% 3 5% 7% 21%	1680
	21st to end	Day	16% 13% 4 10% 5% 5% 5% 4 7% 6% 25%	1680
December	1st to 10th	Day	16% 14% 4 10% 6% 5% 5% 3 5% 6% 27%	2690
	11th to 20th	Day	26% 12% 4 8% 5% 5% 5% 3 4 5% 22%	3076
	21st to end	Day	20% 11% 6% 12% 6% 5% 4 4 5% 6% 21%	4070
January	1st to 10th	Night	13% 16% 6% 15% 8% 5% 4 4 5% 5% 19%	6489
	11th to 20th	Night	17% 12% 7% 14% 8% 5% 5% 3 4 5% 21%	6399
	21st to end	Night	12% 11% 5% 13% 6% 5% 4 4 5% 6% 28%	6741
February	1st to 10th	Night	20% 11% 4 11% 6% 5% 5% 4 5% 6% 23%	2600
	11th to 20th	Night	16% 13% 5% 10% 6% 5% 4 5% 5% 6% 24%	2533
	21st to end	Night	12% 12% 6% 10% 5% 5% 4 4 6% 6% 30%	1998
March	1st to 10th	Night	23% 13% 4 9% 5% 4 4 4 5% 5% 24%	5282
	11th to 20th	Night	20% 13% 5% 10% 4 4 3 3 4 5% 29%	4979
	21st to end	Night	30% 14% 5% 11% 5% 3 3 2 3 3 21%	5204
April	1st to 10th	Night	24% 13% 3 6% 5% 4 5% 3 5% 6% 26%	2000
	11th to 20th	Night	21% 11% 2 7% 4 4 4 3 6% 7% 31%	1976
	21st to end	Night	26% 10% 3 7% 4 3 4 4 4 6% 30%	1858
May	1st to 10th	Night	27% 11% 4 9% 5% 4 4 4 5% 6% 20%	3615
	11th to 20th	Night	25% 12% 4 8% 4 3 3 3 5% 6% 27%	3596
	21st to end	Night	17% 15% 5% 8% 5% 5% 4 4 5% 7% 26%	3948
June	1st to 10th	Night	30% 12% 4 6% 4 4 3 3 4 6% 24%	1600
	11th to 20th	Night	23% 11% 4 6% 3 4 4 3 5% 6% 31%	1600
	21st to end	Night	29% 13% 4 7% 5% 5% 3 3 5% 6% 20%	1600
July	1st to 10th	Night	19% 12% 5% 11% 7% 6% 6% 4 6% 6% 18%	3619
	11th to 20th	Night	17% 16% 4 8% 5% 4 5% 4 5% 6% 27%	3620
	21st to end	Night	17% 11% 3 8% 4 5% 5% 4 6% 7% 30%	3948
August	1st to 10th	Night	16% 14% 4 9% 6% 5% 4 3 4 6% 29%	2720
	11th to 20th	Night	17% 11% 3 9% 6% 4 4 4 6% 7% 30%	2890
	21st to end	Night	13% 6% 2 5% 3 4 5% 4 6% 8% 45%	3586
September	1st to 10th	Night	18% 7% 2 6% 4 4 4 4 6% 6% 38%	2000
	11th to 20th	Night	19% 6% 2 6% 4 4 4 4 4 7% 40%	2000
	21st to end	Night	19% 9% 3 6% 5% 4 4 3 5% 6% 37%	2270
October	1st to 10th	Night	20% 6% 2 5% 3 3 4 3 6% 7% 39%	2400
	11th to 20th	Night	20% 8% 3 7% 4 4 4 3 5% 7% 35%	2400
	21st to end	Night	24% 10% 3 7% 5% 4 4 3 5% 6% 28%	2770
November	1st to 10th	Night	20% 11% 3 9% 6% 5% 4 4 6% 7% 25%	2684
	11th to 20th	Night	22% 12% 3 8% 4 5% 5% 4 5% 6% 25%	2940
	21st to end	Night	19% 12% 4 8% 7% 5% 5% 4 6% 5% 24%	2940
December	1st to 10th	Night	18% 11% 5% 8% 4 4 4 3 4 5% 33%	4720
	11th to 20th	Night	25% 10% 4 9% 5% 5% 5% 3 4 5% 25%	5353
	21st to end	Night	24% 12% 5% 11% 4 4 4 3 4 5% 24%	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	66% 10% 8% 12% 4	3697
	11th to 20th	Day	56% 7% 11% 19% 7%	3668
	21st to end	Day	50% 7% 7% 17% 15% 4	4224
February	1st to 10th	Day	60% 5% 9% 13% 12% 1	1800
	11th to 20th	Day	59% 6% 10% 15% 9% 1	1761
	21st to end	Day	53% 6% 7% 19% 11% 3	1631
March	1st to 10th	Day	58% 5% 8% 14% 13% 3	4559
	11th to 20th	Day	55% 9% 12% 18% 6% 1	4980
	21st to end	Day	66% 6% 8% 13% 6% 1	5727
April	1st to 10th	Day	57% 5% 7% 15% 13% 3	2400
	11th to 20th	Day	54% 5% 9% 19% 12% 1	2374
	21st to end	Day	56% 5% 10% 17% 11% 1	2537
May	1st to 10th	Day	65% 6% 8% 14% 6%	6357
	11th to 20th	Day	57% 6% 12% 17% 8%	6322
	21st to end	Day	58% 6% 9% 20% 6%	6948
June	1st to 10th	Day	63% 5% 10% 15% 6%	2800
	11th to 20th	Day	56% 5% 10% 20% 9% 1	2800
	21st to end	Day	70% 5% 6% 11% 7% 1	2800
July	1st to 10th	Day	69% 6% 9% 10% 7%	6290
	11th to 20th	Day	65% 7% 8% 15% 6%	6284
	21st to end	Day	50% 5% 15% 21% 8%	6730
August	1st to 10th	Day	62% 5% 10% 16% 6%	4419
	11th to 20th	Day	50% 8% 16% 22% 5%	4196
	21st to end	Day	40% 6% 13% 29% 13%	4312
September	1st to 10th	Day	47% 6% 11% 24% 11% 1	2400
	11th to 20th	Day	46% 6% 11% 25% 11% 1	2400
	21st to end	Day	47% 5% 9% 26% 13% 1	2124
October	1st to 10th	Day	48% 7% 13% 22% 9% 1	3260
	11th to 20th	Day	39% 7% 12% 28% 14%	3240
	21st to end	Day	49% 6% 14% 20% 10% 2	3326
November	1st to 10th	Day	56% 7% 12% 18% 7%	1831
	11th to 20th	Day	61% 7% 10% 13% 8% 1	1680
	21st to end	Day	58% 8% 13% 14% 7% 1	1680
December	1st to 10th	Day	55% 6% 10% 20% 8%	2690
	11th to 20th	Day	60% 6% 11% 9% 14%	3075
	21st to end	Day	59% 7% 15% 11% 7% 1	4070
January	1st to 10th	Night	63% 10% 11% 12% 4	6489
	11th to 20th	Night	62% 7% 9% 17% 5%	6445
	21st to end	Night	52% 8% 9% 14% 14% 3	6741
February	1st to 10th	Night	62% 5% 9% 13% 10% 2	2600
	11th to 20th	Night	61% 5% 9% 16% 8% 1	2536
	21st to end	Night	57% 5% 8% 18% 11% 1	1998
March	1st to 10th	Night	60% 5% 6% 14% 11% 3	5291
	11th to 20th	Night	57% 6% 10% 17% 8% 1	4980
	21st to end	Night	67% 4 5% 16% 7% 1	5204
April	1st to 10th	Night	60% 4 9% 15% 10% 2	2000
	11th to 20th	Night	53% 5% 8% 21% 11% 2	1976
	21st to end	Night	55% 4 9% 19% 12% 1	1858
May	1st to 10th	Night	65% 5% 8% 14% 7% 1	3620
	11th to 20th	Night	59% 5% 9% 20% 7%	3597
	21st to end	Night	60% 6% 9% 20% 6%	3949
June	1st to 10th	Night	64% 5% 8% 16% 6%	1600
	11th to 20th	Night	56% 5% 8% 18% 12% 1	1600
	21st to end	Night	68% 3 7% 14% 6% 1	1600
July	1st to 10th	Night	69% 4 8% 12% 6% 1	3581
	11th to 20th	Night	63% 5% 8% 15% 8% 1	3572
	21st to end	Night	54% 4 14% 22% 6%	3831
August	1st to 10th	Night	61% 4 11% 18% 6%	2709
	11th to 20th	Night	53% 6% 17% 20% 4	2917
	21st to end	Night	37% 5% 16% 29% 13%	3585
September	1st to 10th	Night	46% 6% 11% 24% 13%	2000
	11th to 20th	Night	45% 4 12% 25% 13% 1	2000
	21st to end	Night	49% 5% 8% 26% 11% 1	2270
October	1st to 10th	Night	46% 6% 13% 22% 13%	3920
	11th to 20th	Night	37% 5% 12% 29% 16%	3899
	21st to end	Night	51% 5% 13% 20% 10%	4469
November	1st to 10th	Night	56% 7% 12% 17% 7%	2684
	11th to 20th	Night	58% 6% 11% 15% 9% 1	2940
	21st to end	Night	60% 7% 12% 15% 7%	2940
December	1st to 10th	Night	52% 6% 11% 20% 11%	4720
	11th to 20th	Night	59% 6% 10% 14% 10% 2	5355
	21st to end	Night	61% 5% 13% 15% 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	25% 22% 31% 18% 4	430
	11th to 20th	Day	30% 14% 33% 14% 7% 1	418
	21st to end	Day	23% 16% 36% 20% 4	440
February	1st to 10th	Day	28% 16% 34% 20% 2	400
	11th to 20th	Day	26% 20% 32% 19% 4	396
	21st to end	Day	23% 15% 37% 19% 5% 1	331
March	1st to 10th	Day	24% 11% 42% 19% 4	416
	11th to 20th	Day	22% 14% 34% 23% 6% 1	500
	21st to end	Day	27% 16% 33% 18% 5% 1	550
April	1st to 10th	Day	32% 14% 35% 16% 4	500
	11th to 20th	Day	29% 15% 32% 19% 5% 1	492
	21st to end	Day	30% 8% 27% 26% 8% 1	522
May	1st to 10th	Day	34% 10% 28% 20% 6% 2	703
	11th to 20th	Day	25% 7% 28% 27% 10% 3	724
	21st to end	Day	27% 7% 28% 28% 8% 1	790
June	1st to 10th	Day	35% 7% 24% 22% 10% 2	730
	11th to 20th	Day	26% 8% 25% 30% 12% 1	730
	21st to end	Day	40% 4 19% 26% 11% 1	730
July	1st to 10th	Day	29% 3 21% 30% 15% 2	720
	11th to 20th	Day	32% 4 19% 30% 13% 2	718
	21st to end	Day	31% 5% 17% 30% 15% 2	795
August	1st to 10th	Day	22% 3 22% 33% 15% 4	646
	11th to 20th	Day	23% 5% 20% 29% 19% 3	519
	21st to end	Day	21% 4 23% 30% 17% 4	583
September	1st to 10th	Day	19% 8% 27% 29% 16% 2	530
	11th to 20th	Day	22% 8% 26% 27% 14% 3	530
	21st to end	Day	24% 5% 27% 28% 13% 3	433
October	1st to 10th	Day	19% 10% 25% 32% 11% 3	420
	11th to 20th	Day	22% 8% 33% 22% 12% 2	420
	21st to end	Day	26% 11% 36% 18% 7% 1	462
November	1st to 10th	Day	25% 15% 29% 22% 7% 2	425
	11th to 20th	Day	32% 18% 28% 16% 5% 1	430
	21st to end	Day	25% 15% 36% 17% 6% 1	430
December	1st to 10th	Day	30% 14% 30% 20% 4	430
	11th to 20th	Day	32% 20% 30% 15% 2	430
	21st to end	Day	23% 16% 38% 16% 5% 1	473
January	1st to 10th	Night	27% 16% 34% 18% 4	950
	11th to 20th	Night	29% 14% 35% 17% 5%	931
	21st to end	Night	22% 17% 39% 17% 5%	933
February	1st to 10th	Night	29% 13% 34% 19% 5%	800
	11th to 20th	Night	27% 21% 33% 16% 3	783
	21st to end	Night	20% 14% 37% 24% 5% 1	660
March	1st to 10th	Night	25% 16% 35% 20% 4 1	800
	11th to 20th	Night	25% 11% 31% 23% 9% 1	800
	21st to end	Night	29% 11% 31% 22% 7%	773
April	1st to 10th	Night	33% 8% 30% 23% 5%	600
	11th to 20th	Night	28% 7% 30% 26% 8% 1	594
	21st to end	Night	32% 7% 24% 27% 9% 1	600
May	1st to 10th	Night	35% 5% 28% 21% 10% 2	600
	11th to 20th	Night	31% 5% 22% 29% 11% 3	592
	21st to end	Night	27% 4 31% 27% 10% 1	649
June	1st to 10th	Night	37% 4 21% 28% 10% 1	600
	11th to 20th	Night	30% 4 20% 34% 10% 2	600
	21st to end	Night	40% 3 19% 27% 10%	600
July	1st to 10th	Night	32% 3 17% 32% 16% 1	586
	11th to 20th	Night	34% 4 15% 30% 17%	582
	21st to end	Night	35% 4 15% 29% 15% 1	656
August	1st to 10th	Night	27% 3 15% 33% 19% 3	598
	11th to 20th	Night	25% 5% 14% 33% 20% 3	592
	21st to end	Night	22% 3 18% 34% 22% 2	660
September	1st to 10th	Night	25% 5% 20% 31% 16% 3	600
	11th to 20th	Night	23% 6% 23% 31% 16% 2	600
	21st to end	Night	28% 5% 25% 29% 12% 2	695
October	1st to 10th	Night	24% 7% 28% 29% 12% 1	800
	11th to 20th	Night	24% 10% 29% 25% 12% 1	800
	21st to end	Night	30% 12% 30% 22% 6%	952
November	1st to 10th	Night	27% 14% 32% 22% 5% 2	930
	11th to 20th	Night	30% 16% 27% 19% 6% 1	950
	21st to end	Night	29% 14% 34% 19% 4 1	950
December	1st to 10th	Night	31% 14% 31% 18% 5% 1	950
	11th to 20th	Night	32% 17% 33% 15% 3	950
	21st to end	Night	29% 17% 32% 17% 4 1	1045

Page generated at 2026-01-14 02:14:30. Version ac07

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