Prinyer's Cove
Clear Sky Chart
History

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

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% 9% 3 8% 5% 5% 4 4 6% 7% 34%	132486
	Night	16% 10% 4 8% 5% 5% 5% 4 5% 7% 32%	130657
Transparency	Day	32% 37% 8% 15% 8% 1	136016
	Night	35% 37% 7% 13% 8% 1	135214
Seeing	Day	19% 8% 25% 29% 16% 4	16451
	Night	21% 8% 27% 29% 13% 2	25730

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	15% 13% 5% 10% 6% 5% 5% 4 6% 6% 25%	4661
	11th to 20th	Day	11% 19% 7% 17% 8% 6% 4 3 4 4 16%	4650
	21st to end	Day	11% 15% 6% 12% 6% 7% 6% 5% 5% 6% 20%	5697
February	1st to 10th	Day	15% 13% 5% 11% 6% 5% 5% 4 5% 6% 23%	1890
	11th to 20th	Day	15% 11% 6% 10% 6% 5% 5% 4 5% 5% 27%	1843
	21st to end	Day	19% 14% 4 9% 6% 5% 4 4 5% 5% 26%	1704
March	1st to 10th	Day	18% 10% 3 9% 6% 4 3 3 5% 5% 34%	4759
	11th to 20th	Day	10% 10% 3 9% 6% 6% 5% 4 6% 7% 33%	5090
	21st to end	Day	19% 8% 3 7% 5% 4 4 3 5% 5% 38%	5772
April	1st to 10th	Day	19% 10% 3 7% 5% 5% 4 4 4 6% 32%	2520
	11th to 20th	Day	18% 8% 3 7% 5% 4 3 3 4 6% 38%	2494
	21st to end	Day	20% 8% 3 7% 6% 4 4 4 6% 6% 33%	2641
May	1st to 10th	Day	21% 10% 4 9% 5% 4 4 3 5% 6% 28%	6388
	11th to 20th	Day	14% 9% 3 8% 5% 5% 5% 4 5% 6% 36%	6458
	21st to end	Day	18% 7% 3 7% 4 5% 4 4 5% 8% 35%	7103
June	1st to 10th	Day	16% 6% 2 8% 5% 4 5% 4 5% 9% 36%	2800
	11th to 20th	Day	13% 6% 2 6% 4 4 4 5% 7% 9% 40%	2800
	21st to end	Day	14% 7% 3 6% 5% 3 4 4 6% 8% 40%	2800
July	1st to 10th	Day	9% 6% 2 6% 4 4 4 4 7% 9% 43%	6360
	11th to 20th	Day	9% 4 2 6% 4 5% 5% 4 7% 10% 45%	6360
	21st to end	Day	8% 5% 2 6% 4 5% 5% 5% 7% 9% 46%	6926
August	1st to 10th	Day	16% 6% 2 6% 4 4 4 3 5% 7% 43%	4273
	11th to 20th	Day	14% 6% 2 6% 4 3 4 4 6% 10% 41%	4156
	21st to end	Day	13% 5% 2 5% 4 4 4 4 6% 9% 44%	4312
September	1st to 10th	Day	10% 6% 2 5% 4 4 4 4 5% 8% 47%	2400
	11th to 20th	Day	9% 6% 2 5% 4 3 4 4 4 7% 52%	2400
	21st to end	Day	15% 6% 2 8% 4 5% 5% 3 6% 7% 39%	2110
October	1st to 10th	Day	17% 7% 3 6% 5% 4 4 3 5% 7% 39%	2000
	11th to 20th	Day	19% 7% 2 7% 5% 5% 5% 4 7% 8% 33%	2000
	21st to end	Day	24% 9% 3 7% 4 6% 4 4 4 7% 27%	2123
November	1st to 10th	Day	16% 9% 3 6% 5% 5% 5% 4 6% 7% 35%	1842
	11th to 20th	Day	14% 10% 3 9% 6% 5% 5% 4 6% 7% 31%	1680
	21st to end	Day	20% 13% 4 9% 5% 5% 4 4 5% 6% 25%	1680
December	1st to 10th	Day	20% 14% 4 9% 6% 6% 5% 4 5% 7% 21%	2680
	11th to 20th	Day	18% 14% 5% 11% 6% 4 4 3 5% 6% 24%	3066
	21st to end	Day	25% 12% 4 9% 5% 5% 4 3 5% 7% 20%	4048
January	1st to 10th	Night	15% 13% 6% 13% 7% 5% 5% 4 5% 6% 22%	8234
	11th to 20th	Night	13% 17% 6% 17% 7% 7% 5% 4 4 5% 15%	8235
	21st to end	Night	14% 14% 6% 12% 7% 6% 5% 4 5% 5% 22%	8480
February	1st to 10th	Night	16% 13% 5% 11% 6% 5% 5% 4 4 5% 26%	2730
	11th to 20th	Night	15% 13% 5% 10% 4 5% 4 4 5% 6% 28%	2663
	21st to end	Night	16% 10% 4 9% 5% 5% 5% 4 6% 7% 28%	2101
March	1st to 10th	Night	19% 10% 3 8% 5% 5% 4 3 5% 5% 32%	5298
	11th to 20th	Night	15% 11% 4 7% 5% 4 4 4 6% 7% 34%	5089
	21st to end	Night	20% 9% 3 6% 3 3 4 3 5% 6% 37%	5401
April	1st to 10th	Night	21% 9% 3 7% 4 4 5% 3 5% 7% 33%	2100
	11th to 20th	Night	18% 9% 4 7% 4 4 4 3 5% 6% 36%	2075
	21st to end	Night	18% 9% 3 6% 5% 4 4 4 6% 6% 36%	1997
May	1st to 10th	Night	28% 10% 3 7% 4 4 4 3 5% 5% 27%	3770
	11th to 20th	Night	15% 7% 3 7% 4 4 4 4 5% 7% 39%	3655
	21st to end	Night	18% 7% 3 6% 4 4 5% 4 6% 7% 36%	4014
June	1st to 10th	Night	15% 6% 3 6% 5% 5% 5% 4 8% 8% 35%	1600
	11th to 20th	Night	11% 5% 2 6% 5% 4 4 5% 7% 8% 43%	1600
	21st to end	Night	13% 8% 3 7% 5% 3 5% 3 6% 8% 40%	1600
July	1st to 10th	Night	10% 5% 2 7% 5% 4 5% 4 7% 9% 40%	3600
	11th to 20th	Night	10% 6% 2 6% 4 3 4 4 6% 9% 45%	3600
	21st to end	Night	9% 5% 2 6% 4 4 4 3 6% 9% 49%	3926
August	1st to 10th	Night	10% 6% 3 6% 4 4 5% 3 6% 8% 45%	2872
	11th to 20th	Night	13% 6% 3 6% 3 3 4 3 6% 8% 45%	2875
	21st to end	Night	8% 4 2 5% 5% 5% 5% 4 8% 10% 45%	3571
September	1st to 10th	Night	11% 5% 3 6% 4 3 4 3 6% 7% 48%	2000
	11th to 20th	Night	12% 3 2 4 4 3 3 4 5% 8% 52%	2000
	21st to end	Night	17% 6% 2 6% 4 3 4 4 5% 7% 42%	2286
October	1st to 10th	Night	16% 7% 3 8% 5% 5% 4 3 5% 7% 38%	2400
	11th to 20th	Night	19% 8% 3 8% 5% 5% 4 4 4 7% 34%	2400
	21st to end	Night	21% 8% 3 8% 4 4 5% 4 4 6% 31%	2715
November	1st to 10th	Night	18% 8% 3 6% 4 4 4 4 5% 7% 38%	2672
	11th to 20th	Night	17% 9% 3 7% 5% 4 5% 4 5% 7% 33%	2940
	21st to end	Night	22% 10% 4 7% 5% 5% 5% 4 6% 7% 25%	2940
December	1st to 10th	Night	20% 14% 4 8% 5% 5% 5% 4 6% 7% 22%	4720
	11th to 20th	Night	21% 14% 4 8% 4 3 3 3 5% 6% 28%	5348
	21st to end	Night	27% 13% 3 9% 5% 4 5% 4 6% 5% 19%	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	47% 24% 8% 12% 7% 1	4662
	11th to 20th	Day	61% 23% 3 6% 6% 1	4680
	21st to end	Day	50% 25% 8% 9% 8% 1	5697
February	1st to 10th	Day	25% 59% 4 7% 3 1	1890
	11th to 20th	Day	23% 58% 4 10% 5%	1852
	21st to end	Day	24% 60% 5% 6% 4 1	1704
March	1st to 10th	Day	37% 30% 6% 12% 13% 1	4762
	11th to 20th	Day	33% 30% 17% 10% 9% 1	5090
	21st to end	Day	36% 28% 4 17% 13% 2	5772
April	1st to 10th	Day	25% 59% 4 6% 6% 1	2520
	11th to 20th	Day	22% 60% 2 9% 6% 1	2494
	21st to end	Day	20% 60% 4 9% 6% 1	2641
May	1st to 10th	Day	43% 31% 6% 13% 6% 1	6399
	11th to 20th	Day	38% 31% 8% 12% 10%	6462
	21st to end	Day	37% 29% 9% 17% 7%	7103
June	1st to 10th	Day	17% 62% 4 10% 7% 1	2800
	11th to 20th	Day	15% 63% 6% 10% 6% 1	2800
	21st to end	Day	15% 60% 4 11% 7% 1	2800
July	1st to 10th	Day	29% 26% 12% 22% 10%	6290
	11th to 20th	Day	25% 27% 12% 24% 11%	6285
	21st to end	Day	24% 27% 11% 30% 8%	6728
August	1st to 10th	Day	28% 37% 10% 15% 9% 1	4259
	11th to 20th	Day	27% 37% 11% 20% 5%	4195
	21st to end	Day	23% 37% 10% 23% 6%	4312
September	1st to 10th	Day	14% 58% 8% 14% 6%	2400
	11th to 20th	Day	11% 58% 6% 15% 11%	2400
	21st to end	Day	19% 57% 6% 12% 6%	2110
October	1st to 10th	Day	22% 38% 9% 23% 8%	3260
	11th to 20th	Day	24% 37% 12% 22% 6%	3240
	21st to end	Day	28% 37% 9% 19% 6%	3413
November	1st to 10th	Day	26% 55% 6% 8% 5%	1842
	11th to 20th	Day	22% 56% 6% 11% 5%	1680
	21st to end	Day	28% 56% 6% 6% 5%	1680
December	1st to 10th	Day	43% 36% 12% 6% 4	2680
	11th to 20th	Day	44% 34% 7% 9% 6%	3066
	21st to end	Day	47% 29% 9% 12% 4	4048
January	1st to 10th	Night	51% 25% 7% 11% 5%	8234
	11th to 20th	Night	60% 23% 5% 7% 5%	8280
	21st to end	Night	52% 24% 4 9% 9%	8480
February	1st to 10th	Night	25% 60% 4 8% 3 1	2730
	11th to 20th	Night	24% 58% 5% 8% 5%	2665
	21st to end	Night	23% 60% 5% 8% 5%	2101
March	1st to 10th	Night	40% 30% 4 12% 10% 4	5308
	11th to 20th	Night	35% 29% 14% 13% 7% 2	5090
	21st to end	Night	36% 29% 4 17% 13% 1	5401
April	1st to 10th	Night	22% 59% 4 8% 5%	2100
	11th to 20th	Night	20% 60% 4 8% 9% 1	2075
	21st to end	Night	20% 59% 4 9% 7% 1	1997
May	1st to 10th	Night	47% 29% 6% 10% 5% 2	3776
	11th to 20th	Night	35% 31% 11% 14% 9%	3656
	21st to end	Night	36% 30% 9% 14% 11%	4015
June	1st to 10th	Night	17% 62% 4 9% 7% 1	1600
	11th to 20th	Night	17% 62% 4 8% 9% 1	1600
	21st to end	Night	18% 60% 3 10% 8% 1	1600
July	1st to 10th	Night	32% 26% 13% 16% 13% 1	3560
	11th to 20th	Night	27% 26% 9% 26% 11% 1	3552
	21st to end	Night	25% 26% 10% 26% 12% 1	3809
August	1st to 10th	Night	24% 37% 9% 19% 9% 1	2862
	11th to 20th	Night	25% 37% 10% 21% 6%	2902
	21st to end	Night	21% 38% 10% 25% 7%	3571
September	1st to 10th	Night	13% 58% 7% 16% 6% 1	2000
	11th to 20th	Night	13% 57% 4 15% 10% 1	2000
	21st to end	Night	18% 57% 5% 12% 8%	2286
October	1st to 10th	Night	21% 36% 7% 21% 15% 1	3920
	11th to 20th	Night	24% 37% 10% 22% 7%	3899
	21st to end	Night	28% 36% 9% 21% 6%	4375
November	1st to 10th	Night	24% 54% 7% 10% 5%	2672
	11th to 20th	Night	23% 55% 5% 11% 5% 1	2940
	21st to end	Night	27% 56% 6% 8% 3	2940
December	1st to 10th	Night	42% 36% 8% 11% 3	4720
	11th to 20th	Night	41% 33% 8% 9% 9% 1	5348
	21st to end	Night	50% 28% 7% 9% 7%	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	24% 13% 30% 25% 7% 2	220
	11th to 20th	Day	31% 14% 29% 19% 6% 1	220
	21st to end	Day	20% 14% 32% 24% 7% 2	347
February	1st to 10th	Day	25% 12% 35% 21% 6%	330
	11th to 20th	Day	22% 13% 35% 26% 5%	330
	21st to end	Day	27% 14% 32% 24% 3	420
March	1st to 10th	Day	22% 9% 28% 33% 7% 1	540
	11th to 20th	Day	23% 12% 30% 27% 8%	540
	21st to end	Day	27% 9% 32% 21% 10% 2	594
April	1st to 10th	Day	24% 10% 29% 26% 9% 1	540
	11th to 20th	Day	25% 9% 29% 22% 11% 4	532
	21st to end	Day	25% 7% 26% 29% 11% 1	540
May	1st to 10th	Day	22% 6% 25% 30% 15% 3	543
	11th to 20th	Day	14% 5% 25% 34% 19% 4	567
	21st to end	Day	17% 4 22% 32% 18% 7%	617
June	1st to 10th	Day	16% 5% 21% 35% 20% 2	530
	11th to 20th	Day	13% 3 24% 33% 22% 4	530
	21st to end	Day	18% 4 22% 34% 19% 4	530
July	1st to 10th	Day	11% 2 17% 35% 29% 6%	525
	11th to 20th	Day	12% 2 18% 34% 28% 6%	524
	21st to end	Day	11% 3 18% 39% 23% 5%	576
August	1st to 10th	Day	12% 2 12% 36% 31% 7%	526
	11th to 20th	Day	13% 3 14% 34% 26% 10%	519
	21st to end	Day	12% 4 19% 36% 20% 9%	583
September	1st to 10th	Day	12% 6% 18% 32% 24% 9%	530
	11th to 20th	Day	10% 3 14% 30% 26% 17%	530
	21st to end	Day	16% 5% 22% 30% 21% 6%	530
October	1st to 10th	Day	20% 7% 29% 21% 16% 8%	530
	11th to 20th	Day	21% 10% 31% 23% 12% 3	530
	21st to end	Day	28% 11% 26% 26% 9% 1	540
November	1st to 10th	Day	22% 12% 28% 25% 11% 1	416
	11th to 20th	Day	17% 15% 35% 22% 8% 3	220
	21st to end	Day	25% 13% 38% 16% 7% 1	220
December	1st to 10th	Day	25% 18% 26% 23% 6% 1	220
	11th to 20th	Day	25% 20% 34% 16% 5%	220
	21st to end	Day	31% 14% 31% 19% 4	242
January	1st to 10th	Night	26% 13% 35% 20% 5% 1	840
	11th to 20th	Night	29% 12% 30% 22% 6%	840
	21st to end	Night	23% 9% 32% 27% 8%	924
February	1st to 10th	Night	22% 11% 36% 27% 5%	840
	11th to 20th	Night	21% 11% 35% 28% 5%	823
	21st to end	Night	22% 8% 38% 27% 5%	692
March	1st to 10th	Night	22% 8% 30% 34% 6%	840
	11th to 20th	Night	25% 9% 29% 29% 7% 1	840
	21st to end	Night	22% 7% 31% 29% 10% 1	924
April	1st to 10th	Night	24% 8% 30% 31% 7%	840
	11th to 20th	Night	22% 6% 33% 26% 10% 2	831
	21st to end	Night	22% 7% 24% 32% 14% 1	737
May	1st to 10th	Night	26% 3 19% 34% 15% 3	464
	11th to 20th	Night	14% 3 21% 43% 17% 2	414
	21st to end	Night	13% 2 25% 37% 18% 4	455
June	1st to 10th	Night	17% 2 20% 39% 20% 2	400
	11th to 20th	Night	13% 3 20% 39% 23% 3	400
	21st to end	Night	16% 4 21% 37% 22% 2	400
July	1st to 10th	Night	8% 3 18% 39% 29% 2	390
	11th to 20th	Night	12% 3 15% 37% 29% 4	388
	21st to end	Night	11% 2 14% 47% 22% 3	438
August	1st to 10th	Night	10% 2 15% 39% 29% 5%	567
	11th to 20th	Night	14% 2 14% 34% 30% 7%	594
	21st to end	Night	10% 4 18% 39% 26% 4	865
September	1st to 10th	Night	14% 3 20% 34% 24% 6%	800
	11th to 20th	Night	13% 4 15% 27% 31% 10%	800
	21st to end	Night	20% 5% 21% 27% 22% 5%	800
October	1st to 10th	Night	20% 7% 25% 23% 19% 5%	800
	11th to 20th	Night	24% 10% 27% 26% 11% 1	800
	21st to end	Night	25% 12% 29% 26% 8%	880
November	1st to 10th	Night	24% 11% 27% 26% 12% 1	820
	11th to 20th	Night	23% 13% 33% 23% 8% 1	840
	21st to end	Night	28% 13% 29% 21% 7%	840
December	1st to 10th	Night	30% 14% 30% 20% 6%	840
	11th to 20th	Night	26% 15% 35% 19% 4 1	840
	21st to end	Night	33% 12% 32% 19% 4	924

Page generated at 2026-05-29 01:53:28. Version ac07

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