Shelter Cove
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Shelter Cove clear sky chart from 2005-11-06 to 2024-11-12.

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	13% 5% 2 4 3 3 3 3 6% 7% 53%	105204
	Night	15% 6% 2 5% 3 3 3 3 5% 6% 50%	102726
Transparency	Day	16% 47% 5% 11% 10% 9%	104965
	Night	20% 47% 5% 10% 9% 8%	102555
Seeing	Day	13% 5% 17% 29% 26% 9%	15339
	Night	16% 4 13% 29% 27% 12%	24432

By Month

Percentage Cloud Cover SW (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	27% 9% 3 5% 5% 5% 5% 4 5% 6% 27%	2735
	11th to 20th	Day	38% 9% 2 5% 3 3 3 3 4 5% 24%	2860
	21st to end	Day	35% 7% 2 7% 3 3 3 3 4 6% 27%	3146
February	1st to 10th	Day	23% 7% 2 5% 3 4 4 3 4 7% 38%	1710
	11th to 20th	Day	20% 7% 3 6% 4 4 4 4 6% 7% 35%	1665
	21st to end	Day	22% 7% 2 5% 5% 4 4 4 5% 7% 35%	1560
March	1st to 10th	Day	30% 17% 2 5% 3 3 3 3 3 4 27%	3442
	11th to 20th	Day	16% 6% 2 5% 4 4 4 3 5% 7% 46%	3490
	21st to end	Day	23% 11% 3 7% 5% 5% 4 4 6% 6% 26%	3825
April	1st to 10th	Day	18% 8% 3 5% 5% 5% 5% 5% 7% 7% 33%	2234
	11th to 20th	Day	15% 7% 2 5% 4 4 4 4 6% 8% 41%	2249
	21st to end	Day	9% 5% 2 5% 3 3 3 3 8% 11% 47%	2399
May	1st to 10th	Day	8% 4 1 4 3 3 4 3 4 6% 60%	4110
	11th to 20th	Day	5% 2 1 3 2 2 3 3 7% 7% 65%	4091
	21st to end	Day	5% 3 1 3 1 2 3 3 4 7% 68%	4813
June	1st to 10th	Day	11% 4 2 3 3 3 4 4 6% 7% 52%	2660
	11th to 20th	Day	3 2 1 3 2 2 3 3 5% 7% 70%	2660
	21st to end	Day	4 3 1 3 2 2 2 3 5% 5% 70%	2660
July	1st to 10th	Day	1 1 2 1 2 2 1 4 5% 81%	4398
	11th to 20th	Day	2 2 2 3 2 2 3 3 6% 5% 70%	4110
	21st to end	Day	1 1 2 1 2 2 3 7% 7% 74%	4455
August	1st to 10th	Day	1 2 1 2 2 2 3 3 7% 7% 70%	4091
	11th to 20th	Day	4 2 1 2 1 1 3 3 6% 7% 70%	4026
	21st to end	Day	4 3 1 3 2 2 3 4 9% 9% 60%	4246
September	1st to 10th	Day	2 2 1 2 1 2 3 3 8% 8% 69%	2280
	11th to 20th	Day	6% 4 1 3 4 3 4 3 5% 9% 60%	2166
	21st to end	Day	5% 2 1 2 2 2 3 2 4 8% 69%	2062
October	1st to 10th	Day	4 3 1 2 2 2 2 2 3 6% 74%	3180
	11th to 20th	Day	11% 4 1 5% 4 4 5% 4 6% 7% 49%	3161
	21st to end	Day	13% 8% 3 6% 3 3 3 4 5% 7% 45%	3448
November	1st to 10th	Day	18% 6% 3 4 3 4 4 3 6% 8% 41%	1959
	11th to 20th	Day	20% 6% 2 6% 3 4 3 4 6% 8% 37%	1551
	21st to end	Day	15% 5% 1 5% 4 4 4 4 5% 7% 44%	1520
December	1st to 10th	Day	22% 7% 2 5% 3 4 3 3 5% 6% 39%	1520
	11th to 20th	Day	36% 7% 3 5% 4 4 4 3 5% 5% 24%	1928
	21st to end	Day	31% 9% 3 6% 4 4 4 3 4 6% 26%	2794
January	1st to 10th	Night	27% 9% 2 6% 4 4 4 4 6% 8% 26%	4212
	11th to 20th	Night	30% 10% 4 8% 4 4 4 3 5% 5% 23%	4110
	21st to end	Night	36% 10% 3 6% 4 3 3 2 3 5% 24%	4521
February	1st to 10th	Night	22% 8% 2 5% 3 3 4 3 4 7% 39%	2470
	11th to 20th	Night	20% 8% 3 7% 5% 4 4 3 5% 5% 35%	2402
	21st to end	Night	19% 8% 3 4 3 3 4 3 6% 8% 40%	1889
March	1st to 10th	Night	28% 19% 3 5% 3 3 2 2 3 4 26%	3432
	11th to 20th	Night	18% 6% 2 7% 3 3 3 3 4 6% 43%	3490
	21st to end	Night	22% 14% 4 7% 5% 4 4 4 4 6% 27%	3828
April	1st to 10th	Night	19% 8% 2 6% 3 3 4 4 4 6% 40%	1944
	11th to 20th	Night	13% 7% 2 5% 4 4 3 3 6% 8% 45%	1879
	21st to end	Night	10% 4 1 4 4 2 4 4 6% 9% 52%	1777
May	1st to 10th	Night	9% 3 1 2 2 2 3 2 4 6% 68%	2860
	11th to 20th	Night	4 3 1 3 2 2 2 2 5% 5% 71%	2806
	21st to end	Night	4 3 1 2 2 2 2 2 4 7% 71%	2762
June	1st to 10th	Night	8% 6% 2 6% 3 3 4 3 5% 9% 52%	1520
	11th to 20th	Night	3 2 1 1 2 1 2 2 5% 5% 75%	1520
	21st to end	Night	4 2 1 3 2 2 1 2 4 4 75%	1520
July	1st to 10th	Night	1 1 1 1 1 1 1 2 2 87%	2559
	11th to 20th	Night	1 1 1 6% 3 2 3 2 4 3 73%	2860
	21st to end	Night	1 1 1 1 1 2 8% 3 81%	3109
August	1st to 10th	Night	1 1 1 2 2 2 3 3 8% 5% 73%	2848
	11th to 20th	Night	2 2 1 2 1 1 2 2 4 4 79%	2812
	21st to end	Night	4 2 1 2 2 2 2 2 4 4 75%	3429
September	1st to 10th	Night	1 1 1 1 1 1 2 5% 5% 80%	1900
	11th to 20th	Night	5% 4 1 4 2 2 2 2 4 8% 65%	2009
	21st to end	Night	6% 4 1 3 2 2 2 2 3 5% 69%	2118
October	1st to 10th	Night	4 2 1 3 2 2 2 1 2 4 76%	3800
	11th to 20th	Night	10% 7% 3 5% 4 3 3 2 4 6% 52%	3777
	21st to end	Night	14% 5% 2 6% 3 4 4 3 5% 7% 46%	4121
November	1st to 10th	Night	16% 6% 2 5% 3 4 3 4 5% 9% 42%	2340
	11th to 20th	Night	21% 6% 2 7% 4 5% 4 3 6% 8% 35%	2644
	21st to end	Night	18% 6% 2 4 3 3 4 3 5% 8% 45%	2660
December	1st to 10th	Night	24% 6% 2 5% 3 3 3 3 6% 9% 37%	2660
	11th to 20th	Night	37% 8% 2 5% 3 3 3 2 5% 6% 27%	3276
	21st to end	Night	31% 8% 2 6% 4 4 3 3 3 6% 30%	4862

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	33% 46% 8% 10% 2 2	2735
	11th to 20th	Day	48% 41% 5% 3 2 1	2860
	21st to end	Day	42% 41% 6% 7% 4 1	3146
February	1st to 10th	Day	22% 66% 3 6% 4 1	1710
	11th to 20th	Day	22% 65% 4 5% 5% 1	1674
	21st to end	Day	17% 66% 7% 6% 3 2	1560
March	1st to 10th	Day	40% 44% 2 10% 4	3442
	11th to 20th	Day	17% 42% 11% 10% 14% 6%	3490
	21st to end	Day	36% 46% 7% 8% 2 1	3825
April	1st to 10th	Day	17% 66% 6% 7% 4	2234
	11th to 20th	Day	13% 67% 7% 9% 4	2252
	21st to end	Day	12% 66% 6% 9% 5% 1	2399
May	1st to 10th	Day	13% 46% 8% 15% 11% 7%	4110
	11th to 20th	Day	7% 39% 5% 12% 31% 6%	4094
	21st to end	Day	6% 40% 11% 35% 8%	4814
June	1st to 10th	Day	7% 65% 6% 11% 7% 4	2660
	11th to 20th	Day	4 65% 5% 9% 14% 4	2660
	21st to end	Day	5% 62% 3 8% 14% 7%	2660
July	1st to 10th	Day	4 35% 3 5% 5% 48%	4329
	11th to 20th	Day	7% 36% 3 7% 14% 32%	4041
	21st to end	Day	3 34% 4 13% 20% 26%	4315
August	1st to 10th	Day	6% 37% 3 10% 23% 22%	4076
	11th to 20th	Day	8% 36% 6% 25% 15% 9%	4065
	21st to end	Day	12% 37% 6% 19% 14% 13%	4245
September	1st to 10th	Day	4 61% 4 9% 14% 7%	2280
	11th to 20th	Day	8% 60% 6% 12% 12% 2	2166
	21st to end	Day	8% 60% 4 11% 11% 6%	2062
October	1st to 10th	Day	8% 36% 2 11% 9% 34%	3180
	11th to 20th	Day	22% 38% 7% 15% 15% 3	3161
	21st to end	Day	28% 38% 4 12% 12% 5%	3448
November	1st to 10th	Day	15% 57% 8% 10% 8% 2	1959
	11th to 20th	Day	19% 62% 5% 7% 5% 3	1551
	21st to end	Day	19% 61% 3 6% 5% 6%	1520
December	1st to 10th	Day	24% 61% 4 5% 2 4	1520
	11th to 20th	Day	34% 49% 4 4 6% 3	1928
	21st to end	Day	35% 40% 6% 11% 6% 2	2794
January	1st to 10th	Night	35% 43% 10% 7% 3 2	4212
	11th to 20th	Night	48% 41% 4 4 2 1	4110
	21st to end	Night	47% 41% 3 5% 2 1	4521
February	1st to 10th	Night	22% 65% 3 5% 4 1	2470
	11th to 20th	Night	22% 65% 3 4 5% 1	2404
	21st to end	Night	14% 66% 6% 8% 4 2	1889
March	1st to 10th	Night	39% 45% 4 8% 3	3432
	11th to 20th	Night	18% 44% 9% 13% 7% 9%	3490
	21st to end	Night	37% 46% 6% 7% 3	3828
April	1st to 10th	Night	16% 66% 5% 9% 4	1944
	11th to 20th	Night	11% 67% 6% 12% 4	1879
	21st to end	Night	11% 67% 7% 10% 5%	1777
May	1st to 10th	Night	9% 43% 12% 15% 14% 7%	2860
	11th to 20th	Night	6% 39% 4 11% 32% 8%	2807
	21st to end	Night	6% 39% 12% 34% 9%	2762
June	1st to 10th	Night	9% 64% 5% 12% 8% 2	1520
	11th to 20th	Night	3 64% 5% 8% 14% 5%	1520
	21st to end	Night	4 62% 2 8% 16% 8%	1520
July	1st to 10th	Night	3 34% 2 5% 7% 49%	2519
	11th to 20th	Night	7% 37% 3 6% 12% 34%	2806
	21st to end	Night	1 34% 6% 7% 22% 31%	3011
August	1st to 10th	Night	7% 36% 2 9% 20% 26%	2839
	11th to 20th	Night	7% 36% 4 19% 24% 11%	2839
	21st to end	Night	9% 36% 4 19% 16% 15%	3429
September	1st to 10th	Night	4 60% 4 11% 12% 9%	1900
	11th to 20th	Night	7% 60% 4 13% 14% 2	2009
	21st to end	Night	9% 60% 5% 11% 10% 6%	2118
October	1st to 10th	Night	7% 35% 2 7% 13% 36%	3800
	11th to 20th	Night	24% 38% 6% 14% 15% 2	3777
	21st to end	Night	30% 37% 4 14% 10% 6%	4121
November	1st to 10th	Night	16% 57% 8% 9% 8% 2	2340
	11th to 20th	Night	21% 62% 5% 6% 4 1	2644
	21st to end	Night	18% 61% 4 6% 5% 6%	2660
December	1st to 10th	Night	23% 61% 5% 5% 4 2	2660
	11th to 20th	Night	33% 50% 3 6% 6% 2	3276
	21st to end	Night	32% 42% 9% 11% 4 2	4862

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	35% 9% 21% 21% 12% 2	298
	11th to 20th	Day	32% 5% 15% 27% 15% 7%	370
	21st to end	Day	25% 3 15% 29% 22% 6%	407
February	1st to 10th	Day	22% 6% 18% 27% 19% 6%	370
	11th to 20th	Day	24% 9% 25% 19% 18% 5%	365
	21st to end	Day	20% 11% 22% 29% 15% 3	350
March	1st to 10th	Day	34% 10% 18% 23% 11% 4	460
	11th to 20th	Day	25% 5% 18% 30% 17% 5%	460
	21st to end	Day	19% 8% 25% 29% 15% 3	506
April	1st to 10th	Day	22% 7% 24% 26% 15% 5%	460
	11th to 20th	Day	15% 7% 25% 28% 19% 6%	452
	21st to end	Day	10% 5% 32% 29% 17% 7%	460
May	1st to 10th	Day	9% 7% 23% 35% 20% 6%	463
	11th to 20th	Day	12% 5% 23% 27% 23% 9%	488
	21st to end	Day	10% 9% 23% 32% 20% 7%	529
June	1st to 10th	Day	11% 5% 19% 36% 23% 5%	490
	11th to 20th	Day	4 8% 23% 38% 21% 4	490
	21st to end	Day	3 2 13% 40% 32% 10%	490
July	1st to 10th	Day	5% 2 15% 37% 28% 13%	486
	11th to 20th	Day	3 2 13% 40% 35% 8%	484
	21st to end	Day	2 2 8% 27% 41% 20%	531
August	1st to 10th	Day	4 2 7% 36% 38% 14%	487
	11th to 20th	Day	4 10% 31% 44% 10%	477
	21st to end	Day	6% 3 9% 27% 39% 17%	539
September	1st to 10th	Day	3 1 12% 28% 40% 16%	490
	11th to 20th	Day	7% 2 12% 26% 39% 14%	490
	21st to end	Day	6% 3 12% 29% 34% 16%	490
October	1st to 10th	Day	8% 3 16% 23% 32% 19%	490
	11th to 20th	Day	13% 4 13% 23% 30% 18%	490
	21st to end	Day	15% 4 13% 27% 29% 12%	539
November	1st to 10th	Day	17% 5% 18% 27% 22% 11%	495
	11th to 20th	Day	15% 5% 11% 29% 30% 10%	205
	21st to end	Day	14% 5% 12% 32% 27% 9%	180
December	1st to 10th	Day	26% 6% 16% 27% 13% 12%	180
	11th to 20th	Day	31% 4 15% 23% 19% 8%	180
	21st to end	Day	28% 7% 16% 27% 18% 4	198
January	1st to 10th	Night	28% 5% 14% 28% 19% 7%	760
	11th to 20th	Night	27% 4 13% 26% 20% 9%	760
	21st to end	Night	25% 4 12% 28% 24% 8%	836
February	1st to 10th	Night	25% 4 15% 32% 20% 5%	760
	11th to 20th	Night	23% 6% 17% 26% 19% 8%	744
	21st to end	Night	21% 7% 18% 31% 20% 3	628
March	1st to 10th	Night	31% 7% 17% 25% 14% 6%	760
	11th to 20th	Night	25% 5% 13% 28% 24% 6%	760
	21st to end	Night	22% 5% 20% 30% 18% 4	836
April	1st to 10th	Night	21% 5% 19% 30% 18% 7%	760
	11th to 20th	Night	16% 5% 20% 30% 20% 9%	751
	21st to end	Night	11% 3 18% 38% 21% 9%	637
May	1st to 10th	Night	9% 3 19% 36% 26% 8%	570
	11th to 20th	Night	8% 3 13% 35% 26% 15%	547
	21st to end	Night	9% 5% 18% 36% 22% 9%	411
June	1st to 10th	Night	9% 4 16% 35% 30% 6%	380
	11th to 20th	Night	3 2 18% 48% 23% 6%	380
	21st to end	Night	4 1 6% 38% 44% 7%	380
July	1st to 10th	Night	2 2 8% 34% 38% 17%	376
	11th to 20th	Night	2 1 3 39% 36% 19%	552
	21st to end	Night	2 4 24% 42% 28%	624
August	1st to 10th	Night	3 2 1 28% 46% 21%	567
	11th to 20th	Night	3 1 3 27% 45% 22%	564
	21st to end	Night	4 1 6% 21% 46% 23%	793
September	1st to 10th	Night	2 1 6% 23% 49% 20%	760
	11th to 20th	Night	8% 3 8% 26% 36% 20%	760
	21st to end	Night	7% 1 9% 24% 35% 23%	760
October	1st to 10th	Night	8% 2 14% 25% 29% 22%	760
	11th to 20th	Night	12% 3 8% 25% 32% 19%	760
	21st to end	Night	15% 3 10% 28% 29% 15%	836
November	1st to 10th	Night	16% 4 14% 29% 26% 12%	780
	11th to 20th	Night	23% 3 11% 29% 27% 7%	764
	21st to end	Night	19% 3 14% 30% 26% 8%	760
December	1st to 10th	Night	24% 4 14% 31% 18% 9%	760
	11th to 20th	Night	31% 4 15% 26% 19% 6%	760
	21st to end	Night	29% 8% 19% 25% 16% 4	836

Page generated at 2024-11-08 19:45:40. Version ac07

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