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 2024-11-28.

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% 11% 4 9% 5% 5% 5% 4 5% 7% 26%	101819
	Night	21% 11% 4 9% 5% 4 4 3 5% 6% 27%	97843
Transparency	Day	57% 6% 10% 17% 8% 1	105334
	Night	57% 6% 10% 18% 8% 1	102424
Seeing	Day	28% 10% 28% 23% 9% 2	17655
	Night	29% 10% 28% 24% 9% 1	25142

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% 12% 6% 19% 6% 5% 5% 3 5% 4 21%	2526
	11th to 20th	Day	13% 13% 5% 11% 6% 5% 4 4 5% 7% 27%	2530
	21st to end	Day	17% 11% 6% 11% 5% 5% 4 3 5% 6% 26%	2947
February	1st to 10th	Day	20% 11% 4 10% 6% 5% 5% 4 7% 6% 22%	1710
	11th to 20th	Day	18% 10% 4 10% 8% 6% 6% 4 6% 5% 23%	1663
	21st to end	Day	13% 13% 4 8% 6% 6% 5% 4 6% 7% 28%	1551
March	1st to 10th	Day	23% 13% 4 7% 4 4 4 2 4 5% 30%	3167
	11th to 20th	Day	14% 17% 6% 11% 7% 5% 5% 3 6% 6% 21%	3480
	21st to end	Day	31% 14% 4 10% 6% 4 4 3 2 4 19%	3993
April	1st to 10th	Day	23% 11% 4 8% 5% 4 4 4 5% 6% 27%	2280
	11th to 20th	Day	23% 11% 3 7% 4 4 5% 3 4 5% 32%	2254
	21st to end	Day	23% 11% 4 7% 4 4 4 3 4 5% 30%	2410
May	1st to 10th	Day	26% 15% 4 8% 4 4 3 3 4 6% 23%	4425
	11th to 20th	Day	24% 11% 3 7% 5% 4 5% 3 5% 6% 27%	4398
	21st to end	Day	20% 10% 3 8% 5% 5% 5% 4 6% 10% 24%	4836
June	1st to 10th	Day	28% 10% 3 7% 4 5% 5% 4 6% 7% 21%	2660
	11th to 20th	Day	21% 10% 3 7% 6% 4 4 4 5% 7% 30%	2660
	21st to end	Day	27% 14% 3 8% 5% 3 5% 4 6% 6% 19%	2660
July	1st to 10th	Day	20% 9% 4 9% 6% 6% 6% 5% 6% 8% 22%	4440
	11th to 20th	Day	16% 8% 3 9% 6% 7% 7% 6% 7% 9% 23%	4440
	21st to end	Day	17% 9% 3 7% 5% 4 5% 5% 7% 8% 29%	4815
August	1st to 10th	Day	18% 12% 4 9% 6% 5% 5% 4 6% 7% 24%	4297
	11th to 20th	Day	18% 7% 3 8% 5% 5% 5% 5% 7% 9% 27%	4027
	21st to end	Day	11% 7% 2 6% 4 6% 5% 3 5% 7% 43%	4180
September	1st to 10th	Day	18% 7% 3 7% 4 4 4 4 5% 8% 36%	2280
	11th to 20th	Day	19% 8% 3 6% 4 4 5% 4 6% 7% 35%	2280
	21st to end	Day	19% 8% 2 6% 5% 5% 4 4 6% 6% 35%	2018
October	1st to 10th	Day	18% 9% 3 7% 5% 4 5% 4 5% 7% 32%	1900
	11th to 20th	Day	21% 8% 2 7% 4 5% 6% 5% 6% 8% 29%	1900
	21st to end	Day	20% 10% 4 9% 6% 5% 5% 4 6% 6% 25%	1965
November	1st to 10th	Day	23% 10% 3 9% 4 4 5% 3 6% 6% 26%	1742
	11th to 20th	Day	24% 12% 4 9% 6% 4 5% 3 5% 7% 21%	1600
	21st to end	Day	16% 13% 4 10% 5% 5% 5% 5% 8% 6% 25%	1576
December	1st to 10th	Day	21% 17% 5% 9% 6% 5% 4 3 5% 6% 19%	1520
	11th to 20th	Day	30% 13% 3 9% 6% 5% 4 3 5% 6% 16%	1906
	21st to end	Day	23% 12% 6% 11% 6% 4 4 3 4 6% 20%	2783
January	1st to 10th	Night	14% 12% 4 14% 8% 5% 5% 4 5% 7% 22%	4429
	11th to 20th	Night	19% 11% 4 10% 7% 5% 5% 3 5% 6% 25%	4440
	21st to end	Night	16% 11% 5% 15% 6% 5% 4 4 5% 6% 23%	4713
February	1st to 10th	Night	21% 11% 4 11% 6% 5% 5% 4 5% 5% 23%	2470
	11th to 20th	Night	16% 13% 5% 10% 6% 5% 4 5% 5% 7% 24%	2403
	21st to end	Night	12% 12% 6% 10% 5% 5% 4 3 6% 6% 30%	1902
March	1st to 10th	Night	21% 13% 4 8% 5% 4 4 4 5% 5% 26%	3670
	11th to 20th	Night	22% 14% 4 10% 4 4 4 3 4 5% 25%	3479
	21st to end	Night	29% 13% 5% 10% 5% 3 3 2 3 3 23%	3638
April	1st to 10th	Night	24% 13% 3 6% 5% 4 5% 3 5% 6% 26%	1900
	11th to 20th	Night	21% 10% 2 7% 4 4 4 3 6% 7% 31%	1876
	21st to end	Night	26% 10% 4 7% 4 3 4 4 4 5% 30%	1765
May	1st to 10th	Night	28% 10% 3 7% 6% 5% 4 4 5% 7% 21%	2525
	11th to 20th	Night	26% 11% 4 7% 4 3 4 3 5% 5% 29%	2506
	21st to end	Night	20% 14% 5% 8% 5% 5% 4 4 6% 7% 23%	2749
June	1st to 10th	Night	30% 12% 4 7% 4 4 3 3 4 6% 23%	1520
	11th to 20th	Night	24% 11% 3 6% 3 4 4 3 5% 6% 30%	1520
	21st to end	Night	29% 13% 4 7% 5% 5% 3 3 5% 6% 19%	1520
July	1st to 10th	Night	21% 12% 4 10% 7% 6% 6% 4 5% 5% 20%	2530
	11th to 20th	Night	17% 15% 4 10% 6% 5% 5% 5% 5% 6% 22%	2530
	21st to end	Night	19% 12% 2 7% 4 4 5% 4 7% 6% 30%	2750
August	1st to 10th	Night	16% 14% 5% 10% 6% 5% 4 3 4 6% 28%	2636
	11th to 20th	Night	17% 10% 3 9% 6% 4 4 4 6% 7% 29%	2800
	21st to end	Night	13% 6% 2 5% 3 4 5% 3 6% 7% 45%	3476
September	1st to 10th	Night	17% 7% 2 6% 4 4 4 5% 6% 6% 38%	1900
	11th to 20th	Night	19% 7% 2 6% 4 4 4 3 4 7% 41%	1900
	21st to end	Night	20% 10% 3 6% 5% 4 4 3 5% 6% 36%	2156
October	1st to 10th	Night	20% 7% 2 5% 4 3 4 3 6% 7% 38%	2280
	11th to 20th	Night	21% 7% 3 7% 4 4 3 3 5% 7% 36%	2280
	21st to end	Night	24% 10% 3 7% 5% 4 4 3 5% 6% 28%	2631
November	1st to 10th	Night	20% 11% 3 9% 6% 4 4 4 6% 7% 26%	2553
	11th to 20th	Night	22% 12% 3 8% 4 5% 6% 4 6% 6% 26%	2800
	21st to end	Night	20% 13% 4 8% 7% 5% 4 4 5% 6% 24%	2759
December	1st to 10th	Night	25% 14% 5% 8% 4 4 4 3 4 6% 23%	2660
	11th to 20th	Night	30% 11% 4 9% 5% 4 4 3 5% 5% 19%	3293
	21st to end	Night	28% 11% 5% 11% 4 4 3 3 4 5% 21%	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	62% 9% 10% 14% 5%	2527
	11th to 20th	Day	54% 8% 8% 22% 9%	2530
	21st to end	Day	56% 8% 7% 16% 12% 1	2947
February	1st to 10th	Day	61% 5% 9% 13% 11% 1	1710
	11th to 20th	Day	60% 6% 9% 15% 9% 1	1671
	21st to end	Day	52% 7% 8% 19% 11% 3	1551
March	1st to 10th	Day	57% 4 8% 16% 12% 2	3171
	11th to 20th	Day	55% 11% 8% 18% 7% 1	3480
	21st to end	Day	68% 6% 7% 11% 6% 2	3993
April	1st to 10th	Day	57% 5% 7% 15% 13% 3	2280
	11th to 20th	Day	54% 5% 9% 19% 13% 1	2254
	21st to end	Day	55% 5% 10% 16% 12% 1	2410
May	1st to 10th	Day	63% 7% 11% 13% 5% 1	4440
	11th to 20th	Day	58% 7% 10% 18% 7%	4402
	21st to end	Day	60% 8% 11% 15% 5%	4836
June	1st to 10th	Day	64% 5% 10% 15% 5%	2660
	11th to 20th	Day	56% 5% 10% 19% 9% 1	2660
	21st to end	Day	71% 5% 6% 11% 6%	2660
July	1st to 10th	Day	68% 5% 8% 11% 8%	4370
	11th to 20th	Day	68% 6% 8% 11% 7%	4364
	21st to end	Day	55% 6% 13% 17% 8%	4662
August	1st to 10th	Day	64% 5% 10% 15% 5%	4283
	11th to 20th	Day	50% 8% 16% 22% 5%	4066
	21st to end	Day	40% 6% 13% 29% 13%	4180
September	1st to 10th	Day	47% 6% 11% 23% 11% 1	2280
	11th to 20th	Day	46% 6% 11% 25% 11% 1	2280
	21st to end	Day	48% 5% 9% 26% 11% 1	2018
October	1st to 10th	Day	49% 7% 13% 21% 9% 1	3160
	11th to 20th	Day	39% 6% 12% 28% 15%	3140
	21st to end	Day	49% 6% 14% 19% 10% 2	3223
November	1st to 10th	Day	56% 7% 12% 18% 7%	1742
	11th to 20th	Day	60% 7% 10% 13% 8% 1	1600
	21st to end	Day	57% 8% 13% 14% 7% 1	1576
December	1st to 10th	Day	64% 7% 9% 15% 4 1	1520
	11th to 20th	Day	68% 6% 9% 11% 6%	1905
	21st to end	Day	63% 7% 17% 8% 4 1	2783
January	1st to 10th	Night	57% 11% 15% 14% 3	4429
	11th to 20th	Night	58% 7% 9% 19% 6%	4440
	21st to end	Night	59% 10% 9% 13% 8%	4713
February	1st to 10th	Night	63% 5% 9% 13% 9% 1	2470
	11th to 20th	Night	61% 5% 9% 16% 8% 1	2406
	21st to end	Night	57% 5% 8% 18% 11% 1	1902
March	1st to 10th	Night	59% 5% 7% 17% 10% 2	3679
	11th to 20th	Night	60% 8% 8% 17% 6% 1	3480
	21st to end	Night	66% 4 5% 16% 7% 2	3638
April	1st to 10th	Night	59% 4 9% 15% 10% 2	1900
	11th to 20th	Night	52% 5% 8% 21% 11% 3	1876
	21st to end	Night	56% 4 8% 18% 12% 1	1765
May	1st to 10th	Night	63% 7% 10% 15% 5%	2530
	11th to 20th	Night	57% 6% 10% 21% 6%	2507
	21st to end	Night	62% 6% 10% 16% 5%	2750
June	1st to 10th	Night	66% 5% 8% 16% 5%	1520
	11th to 20th	Night	57% 5% 8% 18% 11% 1	1520
	21st to end	Night	69% 3 7% 14% 6%	1520
July	1st to 10th	Night	70% 4 8% 10% 8% 1	2491
	11th to 20th	Night	68% 5% 8% 12% 7%	2482
	21st to end	Night	55% 4 14% 19% 7%	2663
August	1st to 10th	Night	62% 4 11% 18% 5%	2625
	11th to 20th	Night	53% 6% 17% 20% 4	2827
	21st to end	Night	37% 5% 16% 29% 13%	3475
September	1st to 10th	Night	47% 5% 12% 23% 12%	1900
	11th to 20th	Night	45% 4 12% 24% 14% 1	1900
	21st to end	Night	50% 5% 8% 25% 11% 1	2156
October	1st to 10th	Night	47% 6% 13% 22% 12%	3800
	11th to 20th	Night	36% 5% 12% 30% 16%	3779
	21st to end	Night	51% 5% 13% 20% 10%	4330
November	1st to 10th	Night	56% 7% 12% 17% 7%	2553
	11th to 20th	Night	58% 6% 11% 15% 9% 1	2800
	21st to end	Night	60% 7% 12% 15% 6%	2759
December	1st to 10th	Night	64% 5% 10% 14% 6%	2660
	11th to 20th	Night	67% 5% 8% 13% 6% 1	3295
	21st to end	Night	66% 5% 13% 11% 4	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	26% 21% 32% 17% 4	370
	11th to 20th	Day	29% 15% 36% 14% 5% 1	370
	21st to end	Day	24% 16% 34% 21% 4	407
February	1st to 10th	Day	28% 16% 34% 20% 2	370
	11th to 20th	Day	27% 19% 31% 19% 4	366
	21st to end	Day	23% 15% 38% 18% 5% 1	307
March	1st to 10th	Day	25% 10% 43% 19% 3	384
	11th to 20th	Day	21% 15% 34% 22% 7% 1	460
	21st to end	Day	28% 16% 33% 17% 6% 1	506
April	1st to 10th	Day	31% 13% 36% 15% 4	460
	11th to 20th	Day	29% 15% 31% 19% 6% 1	452
	21st to end	Day	30% 9% 28% 24% 9% 1	481
May	1st to 10th	Day	34% 10% 28% 21% 5% 3	653
	11th to 20th	Day	25% 7% 28% 26% 10% 3	674
	21st to end	Day	28% 7% 29% 27% 8% 1	735
June	1st to 10th	Day	36% 7% 24% 21% 10% 1	680
	11th to 20th	Day	26% 8% 25% 29% 11% 1	680
	21st to end	Day	42% 4 18% 26% 10% 1	680
July	1st to 10th	Day	30% 4 20% 30% 14% 2	670
	11th to 20th	Day	33% 4 19% 29% 12% 2	668
	21st to end	Day	32% 4 17% 29% 15% 2	740
August	1st to 10th	Day	23% 3 24% 31% 15% 4	600
	11th to 20th	Day	24% 5% 20% 30% 18% 4	479
	21st to end	Day	21% 4 23% 29% 18% 4	539
September	1st to 10th	Day	19% 8% 28% 28% 15% 2	490
	11th to 20th	Day	23% 8% 26% 27% 13% 3	490
	21st to end	Day	25% 6% 26% 27% 13% 3	402
October	1st to 10th	Day	20% 9% 24% 32% 11% 4	390
	11th to 20th	Day	23% 8% 34% 22% 12% 2	390
	21st to end	Day	26% 12% 36% 18% 7% 1	429
November	1st to 10th	Day	25% 14% 30% 23% 7% 2	395
	11th to 20th	Day	32% 19% 27% 17% 5% 1	400
	21st to end	Day	26% 16% 35% 17% 5% 1	391
December	1st to 10th	Day	31% 14% 31% 19% 4	370
	11th to 20th	Day	32% 21% 30% 15% 2	370
	21st to end	Day	23% 16% 38% 17% 4 1	407
January	1st to 10th	Night	28% 16% 33% 19% 4	850
	11th to 20th	Night	29% 14% 36% 16% 4	850
	21st to end	Night	23% 15% 39% 18% 5%	884
February	1st to 10th	Night	29% 13% 34% 19% 6%	760
	11th to 20th	Night	27% 21% 34% 16% 3	743
	21st to end	Night	20% 14% 36% 24% 5% 1	628
March	1st to 10th	Night	24% 16% 35% 21% 4 1	760
	11th to 20th	Night	25% 12% 31% 22% 10% 1	760
	21st to end	Night	28% 11% 31% 23% 7%	735
April	1st to 10th	Night	32% 8% 29% 24% 6%	570
	11th to 20th	Night	28% 7% 30% 26% 8% 1	564
	21st to end	Night	32% 7% 24% 26% 9% 1	570
May	1st to 10th	Night	35% 4 28% 21% 10% 2	570
	11th to 20th	Night	31% 4 22% 28% 11% 3	562
	21st to end	Night	28% 4 31% 27% 9% 1	616
June	1st to 10th	Night	38% 4 21% 27% 9% 1	570
	11th to 20th	Night	31% 4 20% 33% 10% 2	570
	21st to end	Night	41% 3 19% 26% 11%	570
July	1st to 10th	Night	33% 3 17% 32% 15% 1	556
	11th to 20th	Night	34% 4 15% 29% 17%	552
	21st to end	Night	36% 4 15% 29% 15% 1	623
August	1st to 10th	Night	28% 3 16% 33% 18% 3	568
	11th to 20th	Night	25% 5% 14% 34% 19% 2	562
	21st to end	Night	22% 3 18% 34% 22% 2	627
September	1st to 10th	Night	25% 5% 20% 31% 15% 3	570
	11th to 20th	Night	24% 5% 23% 29% 16% 2	570
	21st to end	Night	29% 5% 25% 28% 12% 2	660
October	1st to 10th	Night	24% 6% 27% 30% 11% 1	760
	11th to 20th	Night	24% 10% 29% 25% 11% 1	760
	21st to end	Night	30% 11% 30% 22% 6%	901
November	1st to 10th	Night	27% 13% 32% 22% 5% 2	880
	11th to 20th	Night	30% 16% 28% 20% 6% 1	900
	21st to end	Night	30% 14% 34% 18% 4 1	886
December	1st to 10th	Night	32% 14% 31% 17% 5% 1	850
	11th to 20th	Night	33% 17% 32% 14% 3	850
	21st to end	Night	30% 16% 33% 17% 4 1	935

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