Sandy Cove
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sandy Cove clear sky chart from 2005-11-06 to 2025-04-11.

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	17% 13% 4 9% 5% 4 4 3 5% 6% 29%	113734
	Night	16% 15% 5% 10% 5% 4 4 3 4 5% 27%	114541
Transparency	Day	57% 3 10% 20% 9% 1	117353
	Night	60% 2 10% 18% 9% 1	119086
Seeing	Day	25% 15% 30% 19% 8% 2	15423
	Night	25% 12% 29% 24% 9% 1	24547

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	12% 18% 10% 15% 8% 4 4 3 4 5% 18%	3158
	11th to 20th	Day	10% 22% 9% 19% 6% 6% 5% 3 4 3 13%	3678
	21st to end	Day	13% 22% 8% 16% 7% 6% 4 3 3 4 16%	4466
February	1st to 10th	Day	13% 19% 7% 16% 7% 5% 4 3 3 4 18%	1800
	11th to 20th	Day	13% 18% 8% 13% 6% 4 4 3 4 5% 22%	1753
	21st to end	Day	15% 19% 7% 13% 6% 5% 4 3 4 4 20%	1488
March	1st to 10th	Day	19% 16% 4 11% 5% 5% 3 3 4 5% 24%	4932
	11th to 20th	Day	12% 14% 6% 11% 6% 5% 5% 4 6% 7% 25%	4980
	21st to end	Day	17% 18% 6% 8% 4 4 3 3 3 4 30%	5465
April	1st to 10th	Day	20% 16% 5% 8% 4 3 3 4 4 6% 27%	2382
	11th to 20th	Day	23% 13% 3 5% 4 4 3 3 4 5% 33%	2360
	21st to end	Day	22% 13% 4 8% 4 3 3 2 4 5% 33%	2470
May	1st to 10th	Day	20% 9% 3 8% 4 5% 4 3 5% 7% 31%	4225
	11th to 20th	Day	15% 8% 3 7% 4 4 4 4 5% 8% 37%	4398
	21st to end	Day	19% 6% 2 6% 4 4 3 3 5% 7% 40%	4837
June	1st to 10th	Day	21% 8% 3 7% 5% 4 5% 3 6% 7% 31%	2699
	11th to 20th	Day	16% 7% 3 7% 5% 5% 5% 4 5% 8% 37%	2850
	21st to end	Day	21% 8% 2 7% 5% 4 5% 4 5% 7% 32%	2850
July	1st to 10th	Day	16% 7% 2 7% 5% 5% 5% 4 6% 8% 34%	4760
	11th to 20th	Day	15% 6% 2 6% 5% 5% 5% 4 6% 8% 39%	4578
	21st to end	Day	12% 6% 2 6% 4 4 4 4 6% 8% 46%	4695
August	1st to 10th	Day	14% 7% 3 7% 5% 6% 6% 4 6% 8% 33%	4104
	11th to 20th	Day	18% 7% 3 7% 4 4 4 5% 6% 8% 33%	4044
	21st to end	Day	10% 5% 2 6% 5% 5% 5% 4 6% 8% 43%	4388
September	1st to 10th	Day	17% 8% 2 7% 4 4 4 4 6% 7% 38%	2280
	11th to 20th	Day	17% 7% 2 5% 4 4 3 3 4 6% 43%	2190
	21st to end	Day	23% 8% 3 6% 4 5% 5% 3 4 5% 33%	2040
October	1st to 10th	Day	21% 9% 2 8% 4 3 5% 3 5% 6% 33%	1900
	11th to 20th	Day	26% 14% 4 9% 5% 3 4 2 4 5% 23%	1900
	21st to end	Day	32% 14% 5% 8% 4 3 3 2 3 4 20%	2090
November	1st to 10th	Day	20% 16% 4 9% 4 4 4 3 4 6% 24%	1580
	11th to 20th	Day	20% 19% 6% 10% 5% 5% 4 2 4 5% 21%	1600
	21st to end	Day	24% 22% 7% 11% 6% 4 3 3 3 4 13%	1600
December	1st to 10th	Day	17% 25% 8% 14% 6% 5% 4 3 4 4 11%	2600
	11th to 20th	Day	18% 24% 6% 12% 6% 3 2 2 3 3 20%	2986
	21st to end	Day	20% 24% 8% 15% 4 3 3 2 3 4 15%	3608
January	1st to 10th	Night	12% 20% 8% 16% 8% 6% 4 2 3 4 16%	6792
	11th to 20th	Night	10% 19% 8% 22% 9% 6% 4 3 3 4 12%	6200
	21st to end	Night	12% 20% 10% 16% 7% 7% 4 3 3 3 15%	6490
February	1st to 10th	Night	12% 19% 7% 13% 8% 5% 4 4 4 6% 18%	2600
	11th to 20th	Night	12% 17% 8% 14% 6% 4 4 3 4 5% 24%	2533
	21st to end	Night	12% 20% 6% 13% 7% 6% 4 3 4 5% 20%	2137
March	1st to 10th	Night	16% 16% 5% 10% 5% 4 4 3 4 5% 28%	4908
	11th to 20th	Night	10% 16% 7% 10% 5% 5% 4 4 5% 7% 26%	4979
	21st to end	Night	21% 12% 5% 8% 5% 5% 3 3 4 4 30%	5467
April	1st to 10th	Night	21% 16% 3 6% 4 4 3 3 5% 6% 28%	2017
	11th to 20th	Night	18% 13% 3 5% 4 4 4 4 4 5% 35%	1793
	21st to end	Night	20% 12% 3 8% 5% 4 3 3 4 6% 31%	1710
May	1st to 10th	Night	16% 9% 3 7% 5% 4 4 4 5% 7% 36%	2715
	11th to 20th	Night	14% 8% 3 7% 4 5% 4 4 6% 8% 37%	2495
	21st to end	Night	12% 9% 2 6% 4 5% 4 3 6% 9% 40%	2738
June	1st to 10th	Night	15% 10% 3 7% 5% 5% 5% 4 5% 6% 36%	1476
	11th to 20th	Night	15% 5% 2 5% 5% 3 4 4 6% 8% 44%	1330
	21st to end	Night	15% 8% 3 7% 4 3 4 4 7% 8% 37%	1330
July	1st to 10th	Night	12% 8% 3 6% 4 3 4 3 5% 7% 44%	2210
	11th to 20th	Night	18% 6% 2 5% 3 3 4 3 4 6% 45%	2384
	21st to end	Night	12% 6% 1 4 3 3 4 5% 5% 7% 48%	2854
August	1st to 10th	Night	12% 6% 2 5% 4 4 4 4 6% 7% 45%	2825
	11th to 20th	Night	18% 7% 2 5% 4 4 4 4 5% 6% 42%	2785
	21st to end	Night	17% 5% 1 5% 3 4 3 3 5% 7% 49%	3235
September	1st to 10th	Night	14% 5% 3 5% 4 4 4 4 6% 7% 45%	1900
	11th to 20th	Night	14% 6% 2 4 4 3 4 4 5% 6% 48%	1987
	21st to end	Night	18% 8% 2 6% 3 4 4 3 5% 7% 40%	2139
October	1st to 10th	Night	19% 10% 3 6% 4 4 5% 3 5% 5% 36%	2280
	11th to 20th	Night	24% 13% 3 8% 5% 4 6% 3 4 5% 25%	2280
	21st to end	Night	27% 18% 4 8% 4 4 4 2 3 4 22%	2508
November	1st to 10th	Night	23% 15% 3 6% 4 4 3 3 4 6% 28%	2715
	11th to 20th	Night	19% 16% 4 8% 6% 4 4 3 5% 6% 25%	2800
	21st to end	Night	23% 20% 6% 10% 6% 5% 3 2 4 5% 16%	2800
December	1st to 10th	Night	18% 25% 7% 14% 6% 4 5% 4 3 4 10%	4580
	11th to 20th	Night	17% 23% 7% 14% 6% 4 3 2 3 4 16%	5208
	21st to end	Night	21% 22% 7% 15% 5% 4 3 3 3 3 15%	7341

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	72% 1 6% 15% 6%	3159
	11th to 20th	Day	78% 1 5% 9% 6% 1	3708
	21st to end	Day	75% 2 4 10% 7% 1	4466
February	1st to 10th	Day	72% 2 6% 14% 5% 1	1800
	11th to 20th	Day	65% 2 10% 13% 8% 1	1762
	21st to end	Day	69% 3 7% 13% 7%	1488
March	1st to 10th	Day	65% 2 10% 8% 14% 2	4935
	11th to 20th	Day	59% 2 14% 16% 7% 2	4980
	21st to end	Day	60% 2 7% 19% 11% 2	5465
April	1st to 10th	Day	59% 2 9% 18% 10% 2	2382
	11th to 20th	Day	55% 3 6% 23% 12% 1	2360
	21st to end	Day	56% 3 8% 17% 14% 3	2470
May	1st to 10th	Day	53% 3 8% 23% 11% 2	4237
	11th to 20th	Day	45% 3 11% 30% 9% 1	4402
	21st to end	Day	45% 3 13% 19% 17% 3	4837
June	1st to 10th	Day	52% 4 10% 21% 12%	2699
	11th to 20th	Day	45% 4 10% 25% 14% 1	2850
	21st to end	Day	51% 4 13% 20% 10% 1	2850
July	1st to 10th	Day	49% 3 15% 24% 9% 1	4686
	11th to 20th	Day	43% 3 14% 31% 9%	4498
	21st to end	Day	38% 3 11% 32% 16%	4545
August	1st to 10th	Day	49% 2 12% 27% 9% 1	4091
	11th to 20th	Day	49% 3 13% 27% 8%	4083
	21st to end	Day	40% 3 11% 35% 10%	4388
September	1st to 10th	Day	45% 4 12% 27% 12% 1	2280
	11th to 20th	Day	43% 3 14% 29% 11% 1	2190
	21st to end	Day	53% 4 10% 25% 8%	2040
October	1st to 10th	Day	54% 3 11% 24% 9% 1	3160
	11th to 20th	Day	56% 4 11% 23% 6%	3140
	21st to end	Day	68% 2 11% 15% 4	3428
November	1st to 10th	Day	62% 3 12% 18% 5%	1580
	11th to 20th	Day	67% 4 10% 13% 5% 1	1600
	21st to end	Day	76% 3 8% 9% 3 1	1600
December	1st to 10th	Day	79% 2 10% 8% 2	2600
	11th to 20th	Day	73% 1 5% 13% 7%	2986
	21st to end	Day	76% 1 3 13% 6%	3608
January	1st to 10th	Night	75% 1 5% 14% 5%	6792
	11th to 20th	Night	79% 1 6% 7% 6%	6245
	21st to end	Night	77% 1 5% 8% 8% 1	6490
February	1st to 10th	Night	68% 3 8% 14% 6% 1	2600
	11th to 20th	Night	65% 2 8% 17% 7% 1	2535
	21st to end	Night	68% 3 8% 14% 6% 1	2137
March	1st to 10th	Night	60% 1 9% 13% 13% 4	4918
	11th to 20th	Night	59% 2 14% 16% 8% 1	4980
	21st to end	Night	59% 2 5% 20% 12% 2	5467
April	1st to 10th	Night	58% 3 7% 19% 11% 2	2017
	11th to 20th	Night	51% 4 7% 22% 15% 2	1793
	21st to end	Night	55% 5% 7% 14% 16% 3	1710
May	1st to 10th	Night	48% 3 11% 26% 10% 1	2722
	11th to 20th	Night	44% 4 10% 27% 14% 1	2496
	21st to end	Night	41% 3 12% 26% 16% 2	2739
June	1st to 10th	Night	48% 4 12% 21% 12% 3	1476
	11th to 20th	Night	38% 4 11% 27% 19%	1330
	21st to end	Night	44% 4 16% 22% 12% 1	1330
July	1st to 10th	Night	41% 2 15% 26% 14% 1	2175
	11th to 20th	Night	41% 3 12% 34% 9% 1	2341
	21st to end	Night	36% 4 10% 33% 17% 1	2763
August	1st to 10th	Night	38% 3 17% 25% 15% 2	2814
	11th to 20th	Night	43% 3 19% 25% 10% 1	2812
	21st to end	Night	37% 3 11% 35% 13% 1	3235
September	1st to 10th	Night	37% 5% 15% 28% 13% 1	1900
	11th to 20th	Night	37% 3 16% 32% 12%	1987
	21st to end	Night	45% 3 13% 28% 11%	2139
October	1st to 10th	Night	44% 3 9% 29% 15%	3800
	11th to 20th	Night	55% 2 14% 21% 8%	3779
	21st to end	Night	63% 2 16% 13% 5%	4120
November	1st to 10th	Night	58% 3 13% 20% 6%	2715
	11th to 20th	Night	61% 4 12% 17% 6% 1	2800
	21st to end	Night	72% 3 9% 11% 4	2800
December	1st to 10th	Night	80% 2 8% 7% 2	4580
	11th to 20th	Night	74% 2 5% 10% 8%	5208
	21st to end	Night	77% 1 5% 11% 5%	7341

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% 25% 35% 14% 4 1	200
	11th to 20th	Day	27% 18% 34% 17% 4	224
	21st to end	Day	28% 17% 34% 16% 5%	330
February	1st to 10th	Day	29% 31% 31% 6% 2 1	300
	11th to 20th	Day	28% 27% 33% 11% 1	300
	21st to end	Day	36% 23% 33% 8%	251
March	1st to 10th	Day	27% 20% 36% 14% 3 1	500
	11th to 20th	Day	23% 23% 36% 13% 4 1	500
	21st to end	Day	31% 18% 28% 17% 4 1	550
April	1st to 10th	Day	30% 20% 31% 14% 5% 1	500
	11th to 20th	Day	37% 17% 23% 15% 6% 4	452
	21st to end	Day	32% 14% 33% 13% 6% 2	460
May	1st to 10th	Day	30% 13% 27% 18% 9% 2	463
	11th to 20th	Day	23% 15% 31% 17% 10% 3	487
	21st to end	Day	21% 17% 31% 18% 10% 2	529
June	1st to 10th	Day	24% 14% 30% 25% 6% 1	529
	11th to 20th	Day	20% 14% 33% 23% 9% 2	680
	21st to end	Day	26% 13% 32% 20% 8% 1	680
July	1st to 10th	Day	15% 11% 33% 29% 10% 2	671
	11th to 20th	Day	17% 11% 29% 27% 12% 3	565
	21st to end	Day	14% 10% 30% 30% 12% 4	532
August	1st to 10th	Day	19% 8% 28% 28% 13% 5%	486
	11th to 20th	Day	18% 7% 26% 25% 16% 9%	479
	21st to end	Day	18% 11% 30% 23% 13% 5%	539
September	1st to 10th	Day	20% 10% 30% 23% 12% 6%	490
	11th to 20th	Day	18% 7% 24% 26% 17% 7%	490
	21st to end	Day	26% 11% 23% 22% 14% 3	490
October	1st to 10th	Day	27% 14% 25% 20% 11% 3	490
	11th to 20th	Day	31% 17% 33% 14% 4 2	490
	21st to end	Day	41% 15% 27% 15% 2 1	539
November	1st to 10th	Day	36% 17% 31% 14% 1	207
	11th to 20th	Day	31% 22% 35% 9% 4	200
	21st to end	Day	34% 16% 40% 8% 2 1	200
December	1st to 10th	Day	29% 18% 38% 13% 3	200
	11th to 20th	Day	39% 18% 30% 11% 3 1	200
	21st to end	Day	34% 21% 25% 17% 1 1	220
January	1st to 10th	Night	29% 16% 33% 17% 5%	997
	11th to 20th	Night	30% 16% 31% 18% 5%	800
	21st to end	Night	21% 12% 35% 23% 7% 1	880
February	1st to 10th	Night	25% 18% 35% 18% 4	800
	11th to 20th	Night	22% 20% 33% 21% 5%	783
	21st to end	Night	25% 21% 28% 23% 3	660
March	1st to 10th	Night	23% 19% 34% 20% 4	800
	11th to 20th	Night	22% 18% 36% 20% 4 1	800
	21st to end	Night	24% 14% 29% 25% 8%	880
April	1st to 10th	Night	31% 12% 32% 20% 5%	800
	11th to 20th	Night	27% 12% 28% 23% 9% 1	665
	21st to end	Night	26% 12% 26% 24% 11% 1	570
May	1st to 10th	Night	23% 7% 27% 32% 10% 1	504
	11th to 20th	Night	21% 8% 30% 33% 8%	374
	21st to end	Night	12% 10% 35% 34% 9%	411
June	1st to 10th	Night	16% 9% 33% 32% 10%	380
	11th to 20th	Night	16% 9% 24% 40% 11%	380
	21st to end	Night	19% 8% 24% 35% 12% 1	380
July	1st to 10th	Night	14% 3 26% 41% 15% 1	370
	11th to 20th	Night	14% 5% 27% 35% 18%	368
	21st to end	Night	13% 5% 23% 39% 19% 1	482
August	1st to 10th	Night	17% 3 18% 38% 22% 2	567
	11th to 20th	Night	15% 4 17% 40% 22% 3	564
	21st to end	Night	19% 6% 24% 30% 18% 3	686
September	1st to 10th	Night	16% 7% 25% 32% 17% 2	760
	11th to 20th	Night	16% 7% 25% 28% 20% 4	760
	21st to end	Night	23% 8% 22% 28% 17% 3	760
October	1st to 10th	Night	26% 10% 26% 25% 12% 1	760
	11th to 20th	Night	30% 11% 29% 22% 7% 1	760
	21st to end	Night	38% 13% 28% 17% 3	836
November	1st to 10th	Night	36% 10% 25% 22% 6% 1	780
	11th to 20th	Night	30% 17% 27% 20% 6%	800
	21st to end	Night	36% 14% 27% 19% 4 1	800
December	1st to 10th	Night	33% 16% 30% 16% 5%	800
	11th to 20th	Night	30% 18% 33% 15% 4 1	800
	21st to end	Night	35% 15% 29% 18% 3	1030

Page generated at 2025-04-08 09:17:29. Version ac07

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