East Point -- Saturna Island
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the East Point -- Saturna Island 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	18% 8% 3 7% 6% 3 5% 5% 5% 7% 34%	74763
	Night	21% 9% 3 6% 5% 3 4 4 5% 6% 32%	75014
Transparency	Day	49% 10% 16% 17% 7% 1	74453
	Night	53% 9% 14% 16% 7% 1	74842
Seeing	Day	19% 5% 13% 26% 27% 11%	14214
	Night	25% 6% 17% 24% 22% 6%	22593

By Month

Percentage Cloud Cover NW (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	37% 11% 4 8% 6% 4 4 4 4 4 14%	1329
	11th to 20th	Day	25% 14% 6% 9% 7% 3 6% 5% 4 5% 15%	1288
	21st to end	Day	29% 13% 5% 9% 8% 4 6% 5% 5% 4 13%	1624
February	1st to 10th	Day	28% 12% 4 8% 7% 4 4 4 6% 6% 17%	1620
	11th to 20th	Day	24% 12% 4 9% 5% 3 5% 4 5% 6% 22%	1575
	21st to end	Day	21% 12% 5% 7% 8% 4 6% 6% 5% 6% 20%	1350
March	1st to 10th	Day	23% 12% 5% 8% 6% 3 5% 5% 5% 8% 21%	1867
	11th to 20th	Day	24% 12% 4 9% 7% 4 4 4 4 5% 23%	1980
	21st to end	Day	21% 11% 4 8% 7% 4 5% 6% 6% 5% 23%	2228
April	1st to 10th	Day	21% 10% 4 7% 6% 4 6% 6% 6% 8% 24%	2160
	11th to 20th	Day	18% 9% 4 7% 5% 4 5% 6% 5% 8% 28%	2214
	21st to end	Day	18% 8% 3 7% 6% 4 6% 6% 6% 7% 30%	2378
May	1st to 10th	Day	12% 6% 3 7% 7% 4 6% 6% 6% 7% 38%	2520
	11th to 20th	Day	13% 7% 3 6% 5% 4 5% 6% 5% 8% 37%	2477
	21st to end	Day	13% 8% 3 6% 6% 3 5% 5% 5% 8% 38%	2747
June	1st to 10th	Day	16% 7% 2 6% 6% 3 5% 5% 6% 8% 36%	2700
	11th to 20th	Day	14% 6% 3 7% 6% 3 5% 6% 5% 7% 36%	2700
	21st to end	Day	10% 5% 2 5% 5% 4 5% 5% 6% 8% 45%	2700
July	1st to 10th	Day	8% 4 2 4 4 3 4 5% 5% 6% 56%	2700
	11th to 20th	Day	7% 3 1 4 4 3 4 4 5% 7% 58%	2700
	21st to end	Day	5% 3 1 2 2 1 3 3 3 6% 70%	2772
August	1st to 10th	Day	7% 4 2 4 3 2 3 4 4 6% 61%	2469
	11th to 20th	Day	7% 3 2 3 3 3 3 4 4 7% 61%	2298
	21st to end	Day	9% 4 2 5% 5% 3 5% 4 6% 9% 49%	2514
September	1st to 10th	Day	9% 5% 3 5% 5% 2 4 4 4 8% 50%	2160
	11th to 20th	Day	13% 7% 3 7% 6% 3 4 4 5% 6% 42%	2155
	21st to end	Day	18% 7% 3 6% 5% 3 3 4 5% 7% 39%	1897
October	1st to 10th	Day	20% 7% 3 7% 5% 3 5% 5% 7% 7% 32%	1800
	11th to 20th	Day	23% 10% 5% 8% 7% 3 4 5% 5% 7% 23%	1800
	21st to end	Day	26% 10% 3 6% 6% 3 4 4 5% 6% 26%	1853
November	1st to 10th	Day	30% 10% 4 6% 7% 4 5% 6% 4 5% 19%	1488
	11th to 20th	Day	29% 11% 4 8% 6% 2 5% 4 4 5% 22%	1520
	21st to end	Day	30% 9% 5% 8% 6% 3 5% 5% 5% 5% 18%	1520
December	1st to 10th	Day	27% 13% 5% 8% 6% 3 4 5% 4 5% 22%	1520
	11th to 20th	Day	29% 14% 6% 12% 7% 4 5% 4 4 5% 11%	1698
	21st to end	Day	26% 16% 6% 10% 7% 4 6% 4 5% 6% 11%	2442
January	1st to 10th	Night	33% 11% 4 9% 6% 3 4 5% 4 4 16%	2836
	11th to 20th	Night	32% 11% 3 7% 6% 3 4 4 4 6% 19%	2748
	21st to end	Night	28% 11% 3 8% 6% 3 5% 5% 5% 6% 22%	2732
February	1st to 10th	Night	29% 12% 3 7% 5% 3 4 4 5% 5% 22%	2340
	11th to 20th	Night	23% 11% 4 8% 6% 3 5% 4 4 6% 27%	2272
	21st to end	Night	23% 12% 5% 6% 5% 3 5% 5% 5% 6% 25%	1906
March	1st to 10th	Night	24% 11% 4 6% 6% 3 5% 4 6% 6% 26%	2092
	11th to 20th	Night	26% 10% 3 6% 6% 3 6% 4 5% 6% 25%	1979
	21st to end	Night	24% 11% 5% 7% 7% 3 5% 6% 5% 6% 21%	2127
April	1st to 10th	Night	22% 11% 4 7% 7% 4 4 5% 6% 6% 25%	1800
	11th to 20th	Night	17% 9% 4 6% 5% 4 5% 6% 6% 8% 30%	1692
	21st to end	Night	18% 10% 4 7% 7% 4 5% 5% 5% 7% 29%	1580
May	1st to 10th	Night	11% 5% 3 7% 6% 3 5% 5% 5% 7% 43%	1440
	11th to 20th	Night	11% 6% 2 6% 6% 4 5% 5% 6% 8% 40%	1416
	21st to end	Night	14% 8% 3 5% 7% 5% 4 5% 7% 7% 36%	1525
June	1st to 10th	Night	17% 7% 3 6% 6% 3 6% 5% 7% 7% 34%	1260
	11th to 20th	Night	12% 7% 3 7% 7% 3 5% 5% 7% 8% 36%	1260
	21st to end	Night	9% 5% 2 6% 4 3 4 4 7% 10% 45%	1260
July	1st to 10th	Night	8% 4 2 4 3 2 4 3 5% 6% 58%	1260
	11th to 20th	Night	5% 3 2 4 3 2 4 4 4 6% 62%	1260
	21st to end	Night	4 2 1 2 2 2 3 3 4 5% 71%	1545
August	1st to 10th	Night	6% 3 1 4 3 2 3 4 4 7% 63%	1467
	11th to 20th	Night	4 3 1 3 2 2 3 3 5% 8% 66%	1602
	21st to end	Night	7% 5% 1 4 5% 3 4 5% 6% 9% 52%	1840
September	1st to 10th	Night	7% 3 1 3 4 2 4 4 5% 6% 60%	1800
	11th to 20th	Night	14% 5% 3 5% 5% 4 4 4 5% 6% 46%	1804
	21st to end	Night	15% 5% 3 6% 6% 2 3 4 4 6% 44%	2062
October	1st to 10th	Night	16% 6% 3 5% 5% 3 5% 5% 4 6% 41%	2160
	11th to 20th	Night	24% 8% 3 5% 4 2 4 4 5% 6% 34%	2160
	21st to end	Night	25% 8% 3 6% 5% 3 4 4 6% 6% 31%	2500
November	1st to 10th	Night	31% 10% 3 7% 5% 3 5% 4 4 5% 21%	2590
	11th to 20th	Night	30% 10% 3 6% 5% 3 4 4 4 7% 23%	2660
	21st to end	Night	28% 10% 5% 8% 6% 3 5% 5% 4 5% 22%	2660
December	1st to 10th	Night	25% 11% 4 7% 6% 3 4 4 5% 6% 24%	2660
	11th to 20th	Night	32% 14% 5% 9% 6% 3 4 4 4 5% 13%	3505
	21st to end	Night	28% 14% 5% 9% 7% 4 4 4 4 4 18%	5214

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	73% 9% 8% 6% 3 1	1329
	11th to 20th	Day	72% 9% 10% 6% 2 1	1288
	21st to end	Day	71% 11% 8% 8% 2	1624
February	1st to 10th	Day	67% 10% 9% 8% 4 1	1620
	11th to 20th	Day	63% 10% 10% 13% 4 1	1584
	21st to end	Day	60% 11% 13% 11% 4 1	1350
March	1st to 10th	Day	61% 9% 14% 11% 4	1867
	11th to 20th	Day	64% 8% 11% 13% 4 1	1980
	21st to end	Day	61% 9% 15% 12% 2	2228
April	1st to 10th	Day	56% 12% 17% 12% 3	2160
	11th to 20th	Day	53% 10% 13% 15% 8% 1	2214
	21st to end	Day	51% 11% 16% 14% 8% 1	2378
May	1st to 10th	Day	43% 12% 19% 17% 8% 1	2520
	11th to 20th	Day	44% 10% 20% 19% 6% 1	2480
	21st to end	Day	45% 11% 21% 20% 4	2748
June	1st to 10th	Day	45% 9% 20% 17% 6% 2	2700
	11th to 20th	Day	46% 10% 22% 17% 4	2700
	21st to end	Day	37% 9% 23% 21% 8% 2	2700
July	1st to 10th	Day	31% 9% 19% 25% 12% 4	2626
	11th to 20th	Day	25% 9% 23% 29% 12% 2	2619
	21st to end	Day	16% 7% 22% 38% 15% 3	2618
August	1st to 10th	Day	25% 9% 20% 32% 13% 2	2452
	11th to 20th	Day	24% 9% 23% 28% 14% 2	2298
	21st to end	Day	31% 10% 23% 28% 7% 1	2514
September	1st to 10th	Day	34% 10% 19% 22% 12% 3	2160
	11th to 20th	Day	42% 9% 16% 18% 13% 2	2155
	21st to end	Day	45% 11% 15% 19% 9% 1	1897
October	1st to 10th	Day	48% 11% 17% 16% 7%	1800
	11th to 20th	Day	59% 11% 14% 12% 3 1	1800
	21st to end	Day	59% 11% 12% 11% 7%	1853
November	1st to 10th	Day	65% 10% 12% 8% 4 1	1488
	11th to 20th	Day	65% 8% 10% 11% 4 2	1520
	21st to end	Day	66% 11% 10% 8% 4 1	1520
December	1st to 10th	Day	65% 8% 8% 12% 7%	1520
	11th to 20th	Day	71% 11% 11% 4 3 1	1701
	21st to end	Day	71% 12% 9% 6% 1	2442
January	1st to 10th	Night	71% 8% 9% 8% 3 1	2836
	11th to 20th	Night	66% 10% 11% 9% 3 1	2748
	21st to end	Night	64% 9% 10% 13% 3 1	2732
February	1st to 10th	Night	65% 8% 12% 9% 4 2	2340
	11th to 20th	Night	61% 9% 11% 13% 7% 1	2274
	21st to end	Night	58% 8% 12% 14% 6% 2	1906
March	1st to 10th	Night	59% 9% 14% 14% 5%	2092
	11th to 20th	Night	60% 9% 11% 14% 5% 1	1980
	21st to end	Night	64% 10% 12% 12% 2	2127
April	1st to 10th	Night	58% 9% 14% 15% 3	1800
	11th to 20th	Night	51% 11% 13% 17% 6% 2	1692
	21st to end	Night	55% 10% 13% 12% 9%	1580
May	1st to 10th	Night	41% 10% 18% 20% 11% 1	1440
	11th to 20th	Night	39% 10% 21% 21% 8% 1	1416
	21st to end	Night	45% 10% 19% 19% 6%	1525
June	1st to 10th	Night	48% 8% 18% 18% 5% 3	1260
	11th to 20th	Night	44% 12% 21% 19% 3	1260
	21st to end	Night	35% 8% 22% 22% 9% 3	1260
July	1st to 10th	Night	30% 8% 16% 28% 15% 4	1225
	11th to 20th	Night	25% 7% 20% 30% 16% 3	1218
	21st to end	Night	14% 7% 15% 33% 26% 5%	1459
August	1st to 10th	Night	23% 7% 17% 29% 19% 4	1459
	11th to 20th	Night	18% 8% 22% 30% 16% 6%	1602
	21st to end	Night	29% 9% 20% 30% 12% 1	1840
September	1st to 10th	Night	24% 9% 18% 29% 15% 5%	1800
	11th to 20th	Night	40% 7% 14% 17% 18% 4	1804
	21st to end	Night	42% 8% 17% 22% 10% 2	2062
October	1st to 10th	Night	44% 8% 16% 21% 10%	2160
	11th to 20th	Night	50% 9% 17% 17% 7%	2160
	21st to end	Night	54% 10% 12% 15% 9%	2500
November	1st to 10th	Night	65% 9% 11% 11% 3 1	2590
	11th to 20th	Night	62% 9% 13% 9% 5% 2	2660
	21st to end	Night	65% 10% 10% 9% 5% 1	2660
December	1st to 10th	Night	61% 10% 11% 12% 6% 1	2660
	11th to 20th	Night	74% 9% 9% 4 3	3501
	21st to end	Night	69% 9% 9% 10% 3 1	5214

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	33% 11% 23% 16% 13% 4	180
	11th to 20th	Day	33% 14% 22% 15% 14% 2	166
	21st to end	Day	40% 4 19% 23% 11% 4	216
February	1st to 10th	Day	34% 11% 19% 19% 16% 1	340
	11th to 20th	Day	33% 5% 19% 25% 14% 3	335
	21st to end	Day	26% 9% 19% 28% 14% 5%	288
March	1st to 10th	Day	28% 7% 18% 24% 19% 5%	420
	11th to 20th	Day	25% 8% 19% 21% 20% 7%	420
	21st to end	Day	26% 7% 16% 28% 19% 4	462
April	1st to 10th	Day	25% 7% 17% 26% 18% 6%	420
	11th to 20th	Day	22% 4 16% 32% 18% 9%	412
	21st to end	Day	18% 4 16% 32% 23% 7%	420
May	1st to 10th	Day	12% 5% 9% 36% 31% 7%	423
	11th to 20th	Day	15% 3 6% 27% 33% 16%	448
	21st to end	Day	13% 3 10% 29% 32% 14%	509
June	1st to 10th	Day	15% 4 12% 31% 30% 9%	630
	11th to 20th	Day	14% 2 15% 34% 27% 8%	630
	21st to end	Day	10% 1 10% 28% 37% 13%	630
July	1st to 10th	Day	10% 1 7% 26% 38% 18%	621
	11th to 20th	Day	6% 1 8% 28% 41% 16%	618
	21st to end	Day	4 1 4 19% 45% 26%	518
August	1st to 10th	Day	6% 1 6% 20% 39% 28%	447
	11th to 20th	Day	4 2 4 26% 41% 23%	437
	21st to end	Day	10% 1 9% 26% 38% 16%	495
September	1st to 10th	Day	11% 2 11% 30% 36% 10%	450
	11th to 20th	Day	15% 2 13% 27% 30% 13%	450
	21st to end	Day	17% 5% 15% 26% 27% 10%	450
October	1st to 10th	Day	22% 4 16% 21% 26% 10%	450
	11th to 20th	Day	28% 6% 13% 22% 21% 9%	450
	21st to end	Day	28% 8% 22% 23% 14% 5%	381
November	1st to 10th	Day	29% 11% 21% 26% 12% 1	180
	11th to 20th	Day	29% 8% 21% 16% 18% 8%	180
	21st to end	Day	33% 7% 20% 19% 12% 9%	180
December	1st to 10th	Day	37% 9% 19% 16% 15% 4	180
	11th to 20th	Day	36% 14% 17% 24% 9% 1	180
	21st to end	Day	34% 14% 23% 19% 9% 1	198
January	1st to 10th	Night	39% 11% 20% 17% 10% 2	850
	11th to 20th	Night	37% 8% 15% 20% 18% 1	815
	21st to end	Night	33% 6% 19% 22% 16% 3	792
February	1st to 10th	Night	35% 10% 18% 23% 11% 3	720
	11th to 20th	Night	28% 8% 22% 26% 14% 2	704
	21st to end	Night	28% 11% 22% 22% 14% 4	592
March	1st to 10th	Night	27% 7% 24% 22% 15% 5%	720
	11th to 20th	Night	29% 9% 21% 21% 17% 3	720
	21st to end	Night	30% 7% 17% 26% 15% 5%	792
April	1st to 10th	Night	25% 7% 17% 28% 18% 6%	720
	11th to 20th	Night	23% 4 20% 29% 18% 6%	624
	21st to end	Night	22% 5% 16% 32% 19% 6%	500
May	1st to 10th	Night	14% 4 15% 30% 30% 7%	360
	11th to 20th	Night	15% 2 8% 26% 39% 10%	354
	21st to end	Night	16% 2 10% 28% 37% 8%	389
June	1st to 10th	Night	19% 3 13% 30% 29% 6%	360
	11th to 20th	Night	14% 3 19% 33% 24% 7%	360
	21st to end	Night	11% 3 11% 29% 37% 9%	360
July	1st to 10th	Night	11% 6% 27% 45% 11%	350
	11th to 20th	Night	5% 2 11% 30% 42% 11%	348
	21st to end	Night	4 7% 27% 48% 15%	394
August	1st to 10th	Night	8% 2 7% 17% 44% 23%	393
	11th to 20th	Night	6% 1 4 23% 50% 17%	534
	21st to end	Night	10% 1 8% 25% 45% 12%	652
September	1st to 10th	Night	10% 1 8% 32% 36% 14%	720
	11th to 20th	Night	17% 3 12% 19% 31% 18%	720
	21st to end	Night	19% 3 14% 25% 30% 8%	720
October	1st to 10th	Night	19% 3 16% 23% 26% 13%	720
	11th to 20th	Night	27% 5% 16% 22% 20% 9%	720
	21st to end	Night	28% 7% 20% 25% 15% 4	792
November	1st to 10th	Night	35% 8% 21% 24% 12% 1	740
	11th to 20th	Night	35% 9% 19% 21% 13% 3	760
	21st to end	Night	34% 8% 18% 22% 14% 4	760
December	1st to 10th	Night	31% 8% 18% 26% 15% 2	760
	11th to 20th	Night	39% 10% 23% 19% 8% 1	843
	21st to end	Night	40% 10% 25% 17% 7% 1	935

Page generated at 2024-01-11 10:31:59. Version ac07

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