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 2024-01-14.

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 2 4 4 5% 7% 51%	74666
	Night	16% 5% 2 4 4 2 3 3 5% 7% 50%	75094
Transparency	Day	32% 6% 12% 22% 19% 10%	74387
	Night	35% 6% 11% 20% 18% 9%	74895
Seeing	Day	14% 5% 17% 29% 26% 9%	14171
	Night	16% 3 13% 29% 27% 12%	23394

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	29% 9% 3 5% 5% 3 4 5% 5% 5% 26%	1637
	11th to 20th	Day	27% 6% 2 4 3 2 3 4 4 7% 38%	1648
	21st to end	Day	22% 6% 2 6% 5% 2 3 4 4 7% 38%	1782
February	1st to 10th	Day	23% 6% 2 5% 4 2 4 4 4 7% 39%	1620
	11th to 20th	Day	19% 6% 3 5% 5% 2 5% 4 6% 8% 37%	1575
	21st to end	Day	23% 6% 2 4 6% 3 4 4 4 7% 36%	1470
March	1st to 10th	Day	27% 11% 3 5% 3 3 4 4 4 6% 30%	1980
	11th to 20th	Day	24% 6% 2 5% 4 3 4 5% 6% 9% 33%	1980
	21st to end	Day	21% 7% 2 5% 5% 4 5% 4 6% 7% 35%	2178
April	1st to 10th	Day	19% 7% 3 5% 6% 3 5% 6% 7% 7% 32%	2116
	11th to 20th	Day	15% 6% 2 4 5% 3 4 5% 5% 8% 42%	2129
	21st to end	Day	9% 4 2 5% 4 3 3 4 7% 11% 49%	2272
May	1st to 10th	Day	8% 4 2 3 3 2 5% 4 5% 8% 56%	2340
	11th to 20th	Day	9% 4 2 4 4 3 4 4 6% 9% 52%	2308
	21st to end	Day	9% 5% 2 4 3 2 5% 4 5% 8% 54%	2723
June	1st to 10th	Day	11% 4 2 3 3 2 4 5% 5% 7% 52%	2520
	11th to 20th	Day	4 2 1 3 2 1 2 3 5% 7% 70%	2520
	21st to end	Day	4 2 1 2 3 1 2 3 5% 5% 70%	2520
July	1st to 10th	Day	2 2 1 2 2 2 4 3 5% 6% 70%	2511
	11th to 20th	Day	3 1 1 2 2 1 3 4 5% 6% 71%	2340
	21st to end	Day	1 2 1 2 3 2 4 4 7% 9% 66%	2546
August	1st to 10th	Day	1 2 1 2 3 2 3 3 6% 7% 71%	2328
	11th to 20th	Day	2 2 2 2 1 3 5% 8% 10% 66%	2298
	21st to end	Day	2 3 1 2 3 2 2 4 7% 8% 67%	2416
September	1st to 10th	Day	2 2 1 2 1 1 3 3 7% 7% 70%	2160
	11th to 20th	Day	6% 4 1 2 4 2 3 3 5% 9% 60%	2052
	21st to end	Day	5% 2 1 2 2 2 2 3 4 8% 69%	1954
October	1st to 10th	Day	8% 4 1 2 2 1 1 3 3 7% 67%	1800
	11th to 20th	Day	13% 4 1 3 4 3 4 4 6% 7% 52%	1800
	21st to end	Day	13% 6% 2 4 3 1 2 4 5% 7% 53%	1980
November	1st to 10th	Day	18% 6% 3 3 4 2 4 4 6% 8% 41%	1859
	11th to 20th	Day	20% 5% 3 5% 4 3 4 5% 5% 9% 37%	1542
	21st to end	Day	15% 5% 1 5% 5% 4 4 4 5% 8% 44%	1520
December	1st to 10th	Day	22% 7% 2 4 4 3 4 4 5% 6% 40%	1520
	11th to 20th	Day	36% 7% 3 5% 4 3 4 4 5% 6% 24%	1928
	21st to end	Day	31% 9% 3 5% 4 3 4 4 4 6% 26%	2794
January	1st to 10th	Night	27% 7% 3 5% 4 4 4 4 5% 7% 30%	2524
	11th to 20th	Night	25% 7% 3 4 4 2 3 3 5% 8% 35%	2384
	21st to end	Night	21% 7% 3 5% 5% 3 4 4 5% 7% 38%	2574
February	1st to 10th	Night	21% 7% 2 5% 3 2 4 4 4 7% 40%	2340
	11th to 20th	Night	19% 7% 3 6% 6% 3 4 4 5% 6% 38%	2272
	21st to end	Night	19% 7% 3 3 4 2 4 4 6% 8% 40%	1781
March	1st to 10th	Night	27% 11% 3 6% 4 2 3 4 4 6% 30%	1980
	11th to 20th	Night	26% 6% 2 4 5% 3 4 4 5% 8% 33%	1980
	21st to end	Night	22% 6% 3 5% 4 2 4 4 4 8% 38%	2178
April	1st to 10th	Night	21% 7% 2 5% 4 2 4 5% 5% 6% 39%	1842
	11th to 20th	Night	13% 6% 3 4 4 3 3 4 6% 8% 45%	1779
	21st to end	Night	10% 4 2 3 5% 2 4 5% 6% 9% 52%	1684
May	1st to 10th	Night	8% 4 1 3 3 2 3 4 5% 6% 61%	1620
	11th to 20th	Night	7% 4 2 4 5% 2 4 4 6% 8% 54%	1580
	21st to end	Night	8% 5% 2 4 3 2 3 5% 5% 9% 54%	1552
June	1st to 10th	Night	8% 6% 3 5% 3 2 4 4 4 10% 51%	1440
	11th to 20th	Night	4 2 1 1 2 1 2 3 4 5% 74%	1440
	21st to end	Night	4 2 1 2 3 1 2 2 4 4 74%	1440
July	1st to 10th	Night	1 2 1 2 2 1 2 3 4 4 78%	1445
	11th to 20th	Night	1 2 1 2 2 1 1 2 3 4 81%	1620
	21st to end	Night	1 1 2 2 1 2 3 6% 4 78%	1773
August	1st to 10th	Night	1 2 2 2 2 1 2 2 4 4 78%	1611
	11th to 20th	Night	1 1 1 1 2 1 2 2 5% 5% 78%	1602
	21st to end	Night	1 2 1 3 2 1 2 2 3 4 78%	1939
September	1st to 10th	Night	1 1 1 2 1 1 2 4 5% 81%	1800
	11th to 20th	Night	5% 4 1 4 3 2 2 3 4 7% 65%	1903
	21st to end	Night	6% 3 1 3 3 2 2 2 3 6% 68%	2006
October	1st to 10th	Night	7% 3 1 3 2 2 3 2 4 6% 67%	2160
	11th to 20th	Night	11% 4 2 3 4 2 3 3 5% 6% 57%	2160
	21st to end	Night	14% 4 2 3 3 2 3 3 4 6% 56%	2376
November	1st to 10th	Night	17% 6% 2 5% 4 3 4 4 5% 9% 41%	2220
	11th to 20th	Night	21% 6% 2 6% 5% 3 4 4 6% 8% 35%	2631
	21st to end	Night	18% 5% 2 3 3 2 3 4 5% 8% 45%	2660
December	1st to 10th	Night	24% 6% 2 4 3 2 3 4 5% 9% 37%	2660
	11th to 20th	Night	37% 7% 2 4 3 2 4 3 5% 6% 27%	3276
	21st to end	Night	31% 8% 2 5% 5% 3 4 3 3 5% 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	59% 7% 10% 13% 6% 5%	1637
	11th to 20th	Day	47% 6% 11% 12% 14% 10%	1648
	21st to end	Day	48% 5% 7% 15% 16% 8%	1782
February	1st to 10th	Day	47% 5% 10% 16% 16% 6%	1620
	11th to 20th	Day	45% 7% 11% 18% 16% 3	1584
	21st to end	Day	49% 7% 13% 17% 11% 3	1470
March	1st to 10th	Day	57% 6% 9% 14% 12% 2	1980
	11th to 20th	Day	49% 6% 13% 16% 13% 3	1980
	21st to end	Day	50% 9% 13% 18% 9% 2	2178
April	1st to 10th	Day	49% 8% 15% 17% 10% 1	2116
	11th to 20th	Day	42% 9% 13% 22% 11% 4	2132
	21st to end	Day	31% 9% 18% 23% 16% 3	2272
May	1st to 10th	Day	25% 8% 16% 29% 18% 5%	2340
	11th to 20th	Day	29% 7% 15% 27% 16% 4	2311
	21st to end	Day	29% 8% 17% 33% 12% 1	2724
June	1st to 10th	Day	30% 6% 16% 29% 15% 4	2520
	11th to 20th	Day	14% 6% 15% 27% 30% 9%	2520
	21st to end	Day	14% 3 9% 29% 33% 12%	2520
July	1st to 10th	Day	11% 4 8% 25% 29% 23%	2442
	11th to 20th	Day	10% 3 8% 22% 30% 27%	2271
	21st to end	Day	8% 2 8% 22% 33% 26%	2405
August	1st to 10th	Day	9% 3 9% 29% 35% 14%	2312
	11th to 20th	Day	8% 2 9% 30% 32% 19%	2298
	21st to end	Day	11% 4 13% 22% 31% 19%	2416
September	1st to 10th	Day	10% 3 9% 24% 30% 24%	2160
	11th to 20th	Day	21% 5% 13% 28% 27% 6%	2052
	21st to end	Day	15% 4 13% 25% 23% 20%	1954
October	1st to 10th	Day	21% 4 10% 28% 21% 17%	1800
	11th to 20th	Day	30% 6% 10% 21% 22% 12%	1800
	21st to end	Day	32% 6% 10% 21% 17% 14%	1980
November	1st to 10th	Day	41% 8% 14% 19% 12% 6%	1859
	11th to 20th	Day	44% 8% 12% 16% 13% 7%	1542
	21st to end	Day	40% 7% 12% 14% 16% 11%	1520
December	1st to 10th	Day	44% 7% 12% 17% 13% 9%	1520
	11th to 20th	Day	62% 5% 9% 10% 11% 3	1928
	21st to end	Day	59% 8% 9% 13% 9% 3	2794
January	1st to 10th	Night	55% 8% 12% 13% 8% 4	2524
	11th to 20th	Night	50% 7% 10% 12% 11% 10%	2384
	21st to end	Night	48% 6% 8% 16% 16% 7%	2574
February	1st to 10th	Night	45% 7% 11% 17% 15% 5%	2340
	11th to 20th	Night	48% 8% 9% 17% 14% 4	2274
	21st to end	Night	42% 9% 16% 20% 11% 3	1781
March	1st to 10th	Night	56% 7% 10% 15% 12% 1	1980
	11th to 20th	Night	50% 7% 12% 17% 11% 2	1980
	21st to end	Night	48% 8% 16% 17% 8% 2	2178
April	1st to 10th	Night	46% 8% 15% 18% 11% 2	1842
	11th to 20th	Night	36% 8% 17% 25% 11% 3	1779
	21st to end	Night	29% 8% 18% 28% 15% 1	1684
May	1st to 10th	Night	23% 8% 13% 32% 20% 4	1620
	11th to 20th	Night	27% 7% 17% 27% 17% 4	1581
	21st to end	Night	26% 8% 20% 34% 12% 1	1552
June	1st to 10th	Night	30% 6% 15% 29% 17% 3	1440
	11th to 20th	Night	13% 4 13% 29% 32% 9%	1440
	21st to end	Night	14% 3 7% 25% 37% 15%	1440
July	1st to 10th	Night	9% 2 6% 23% 34% 26%	1405
	11th to 20th	Night	9% 3 5% 19% 34% 32%	1566
	21st to end	Night	6% 1 6% 17% 37% 32%	1674
August	1st to 10th	Night	8% 3 8% 26% 36% 18%	1602
	11th to 20th	Night	8% 2 10% 21% 34% 25%	1602
	21st to end	Night	9% 3 8% 22% 33% 24%	1939
September	1st to 10th	Night	6% 3 6% 21% 31% 32%	1800
	11th to 20th	Night	19% 4 11% 31% 26% 8%	1903
	21st to end	Night	18% 5% 11% 23% 23% 20%	2006
October	1st to 10th	Night	20% 5% 9% 25% 22% 19%	2160
	11th to 20th	Night	28% 6% 9% 21% 26% 10%	2160
	21st to end	Night	31% 5% 11% 24% 17% 13%	2376
November	1st to 10th	Night	41% 9% 14% 16% 14% 6%	2220
	11th to 20th	Night	47% 8% 13% 16% 11% 5%	2631
	21st to end	Night	39% 6% 13% 16% 16% 10%	2660
December	1st to 10th	Night	44% 7% 12% 15% 15% 6%	2660
	11th to 20th	Night	59% 5% 9% 13% 11% 2	3276
	21st to end	Night	55% 9% 13% 15% 7% 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% 4 15% 27% 16% 7%	350
	21st to end	Day	24% 3 16% 29% 23% 6%	374
February	1st to 10th	Day	23% 5% 17% 29% 21% 6%	340
	11th to 20th	Day	23% 9% 25% 20% 18% 5%	335
	21st to end	Day	21% 11% 24% 28% 14% 3	318
March	1st to 10th	Day	33% 10% 18% 24% 12% 4	420
	11th to 20th	Day	27% 5% 16% 30% 17% 4	420
	21st to end	Day	18% 8% 25% 29% 16% 3	462
April	1st to 10th	Day	24% 7% 25% 25% 15% 5%	420
	11th to 20th	Day	15% 8% 26% 28% 18% 5%	412
	21st to end	Day	10% 5% 33% 29% 16% 7%	420
May	1st to 10th	Day	9% 7% 23% 34% 21% 6%	423
	11th to 20th	Day	13% 5% 23% 28% 22% 8%	448
	21st to end	Day	11% 9% 22% 31% 20% 7%	485
June	1st to 10th	Day	12% 5% 19% 35% 23% 6%	450
	11th to 20th	Day	5% 8% 24% 37% 21% 4	450
	21st to end	Day	4 2 14% 41% 30% 10%	450
July	1st to 10th	Day	6% 2 16% 38% 28% 9%	446
	11th to 20th	Day	3 2 13% 41% 34% 8%	444
	21st to end	Day	2 3 8% 28% 40% 19%	487
August	1st to 10th	Day	5% 2 8% 37% 35% 14%	447
	11th to 20th	Day	3 11% 29% 46% 11%	437
	21st to end	Day	5% 3 9% 27% 40% 16%	495
September	1st to 10th	Day	3 2 14% 28% 38% 15%	450
	11th to 20th	Day	7% 2 13% 25% 39% 14%	450
	21st to end	Day	6% 4 13% 30% 33% 14%	450
October	1st to 10th	Day	8% 3 18% 23% 31% 17%	450
	11th to 20th	Day	13% 4 13% 23% 30% 18%	450
	21st to end	Day	15% 3 13% 25% 31% 13%	495
November	1st to 10th	Day	17% 5% 19% 27% 22% 11%	455
	11th to 20th	Day	14% 5% 10% 29% 31% 10%	202
	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% 21% 9%	734
	21st to end	Night	23% 3 12% 28% 25% 8%	792
February	1st to 10th	Night	24% 4 14% 32% 21% 5%	720
	11th to 20th	Night	22% 5% 18% 27% 19% 9%	704
	21st to end	Night	22% 7% 19% 31% 19% 2	592
March	1st to 10th	Night	31% 6% 17% 25% 15% 6%	720
	11th to 20th	Night	26% 5% 12% 28% 25% 4	720
	21st to end	Night	23% 5% 19% 30% 19% 4	792
April	1st to 10th	Night	22% 5% 19% 29% 18% 7%	720
	11th to 20th	Night	16% 5% 20% 30% 20% 9%	711
	21st to end	Night	11% 4 19% 38% 20% 9%	604
May	1st to 10th	Night	9% 3 19% 35% 26% 8%	540
	11th to 20th	Night	9% 3 13% 35% 26% 14%	518
	21st to end	Night	10% 5% 18% 35% 22% 10%	389
June	1st to 10th	Night	10% 4 16% 34% 30% 6%	360
	11th to 20th	Night	4 2 19% 47% 24% 6%	360
	21st to end	Night	5% 1 6% 38% 44% 7%	360
July	1st to 10th	Night	2 2 9% 34% 37% 16%	355
	11th to 20th	Night	2 1 3 39% 36% 18%	522
	21st to end	Night	2 1 4 25% 41% 28%	591
August	1st to 10th	Night	3 2 1 28% 45% 20%	537
	11th to 20th	Night	3 3 26% 45% 23%	534
	21st to end	Night	4 1 6% 21% 46% 22%	751
September	1st to 10th	Night	2 1 6% 23% 48% 20%	720
	11th to 20th	Night	8% 3 8% 24% 36% 21%	720
	21st to end	Night	8% 1 10% 24% 35% 23%	720
October	1st to 10th	Night	8% 2 15% 25% 28% 21%	720
	11th to 20th	Night	12% 4 8% 26% 32% 19%	720
	21st to end	Night	15% 3 10% 26% 30% 16%	792
November	1st to 10th	Night	16% 4 14% 28% 26% 12%	740
	11th to 20th	Night	22% 3 11% 29% 27% 7%	760
	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 2024-01-11 01:22:42. Version ac07

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