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 2026-01-17.

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	16% 8% 3 7% 5% 4 4 4 5% 6% 37%	131461
	Night	20% 9% 3 8% 5% 4 4 3 5% 6% 33%	128932
Transparency	Day	28% 41% 12% 13% 5% 1	131169
	Night	33% 40% 10% 12% 5% 1	128801
Seeing	Day	18% 5% 13% 25% 27% 12%	16816
	Night	25% 6% 16% 24% 22% 6%	25135

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	31% 14% 4 10% 6% 5% 5% 3 4 4 12%	3249
	11th to 20th	Day	17% 13% 4 8% 5% 4 5% 5% 6% 8% 26%	3222
	21st to end	Day	30% 13% 4 11% 5% 5% 5% 3 4 4 15%	4114
February	1st to 10th	Day	25% 13% 4 9% 7% 5% 4 4 6% 5% 17%	1800
	11th to 20th	Day	24% 13% 4 10% 5% 4 4 3 5% 5% 22%	1755
	21st to end	Day	21% 14% 4 9% 7% 6% 5% 4 5% 6% 18%	1505
March	1st to 10th	Day	20% 12% 4 10% 6% 6% 5% 5% 6% 7% 19%	4689
	11th to 20th	Day	17% 12% 4 9% 5% 4 5% 4 5% 7% 28%	5000
	21st to end	Day	21% 12% 4 9% 6% 5% 6% 4 6% 5% 20%	5613
April	1st to 10th	Day	20% 11% 3 7% 6% 6% 6% 5% 7% 7% 23%	2400
	11th to 20th	Day	16% 10% 3 8% 5% 5% 5% 5% 6% 8% 30%	2464
	21st to end	Day	18% 9% 3 7% 5% 5% 5% 5% 6% 7% 32%	2643
May	1st to 10th	Day	11% 7% 3 7% 5% 4 4 3 5% 5% 47%	6320
	11th to 20th	Day	12% 8% 3 7% 5% 5% 5% 4 6% 9% 36%	6277
	21st to end	Day	15% 8% 3 7% 5% 5% 5% 4 6% 8% 35%	6983
June	1st to 10th	Day	15% 7% 2 7% 5% 4 5% 4 6% 8% 38%	3000
	11th to 20th	Day	14% 7% 3 8% 5% 5% 5% 5% 6% 7% 35%	3000
	21st to end	Day	10% 5% 2 6% 5% 5% 5% 4 6% 8% 43%	3000
July	1st to 10th	Day	6% 3 1 3 2 3 3 3 4 5% 67%	6780
	11th to 20th	Day	3 2 1 2 2 2 2 2 3 5% 74%	6780
	21st to end	Day	7% 3 1 3 2 2 3 3 4 6% 65%	6933
August	1st to 10th	Day	4 3 1 3 2 2 3 2 4 5% 71%	4462
	11th to 20th	Day	9% 4 2 6% 4 5% 5% 4 5% 7% 49%	4156
	21st to end	Day	12% 6% 2 7% 5% 4 4 3 5% 7% 46%	4548
September	1st to 10th	Day	8% 5% 3 5% 4 4 4 3 4 8% 51%	2400
	11th to 20th	Day	12% 7% 3 8% 5% 4 4 3 5% 6% 42%	2393
	21st to end	Day	17% 8% 3 6% 5% 4 3 3 5% 7% 39%	2107
October	1st to 10th	Day	17% 5% 2 8% 5% 5% 6% 5% 7% 8% 30%	3280
	11th to 20th	Day	29% 8% 3 8% 5% 4 4 4 5% 6% 24%	3261
	21st to end	Day	22% 11% 3 10% 5% 6% 4 4 6% 6% 23%	3316
November	1st to 10th	Day	29% 11% 3 7% 6% 5% 5% 5% 5% 5% 18%	1648
	11th to 20th	Day	29% 12% 3 9% 5% 4 5% 3 5% 5% 21%	1680
	21st to end	Day	31% 11% 4 9% 5% 4 5% 4 5% 5% 17%	1680
December	1st to 10th	Day	21% 12% 3 12% 8% 5% 6% 4 5% 7% 18%	2700
	11th to 20th	Day	32% 13% 5% 11% 5% 4 5% 3 5% 4 12%	2728
	21st to end	Day	28% 17% 5% 11% 6% 5% 5% 3 5% 5% 10%	3575
January	1st to 10th	Night	30% 16% 5% 11% 6% 5% 5% 3 4 4 12%	6916
	11th to 20th	Night	20% 8% 3 8% 5% 4 4 5% 6% 8% 30%	6806
	21st to end	Night	30% 11% 3 9% 5% 4 4 4 4 6% 20%	6847
February	1st to 10th	Night	27% 14% 3 8% 5% 4 4 3 5% 5% 22%	2600
	11th to 20th	Night	23% 12% 4 9% 5% 4 4 3 4 5% 27%	2532
	21st to end	Night	24% 13% 4 7% 5% 4 4 4 5% 6% 24%	2125
March	1st to 10th	Night	16% 11% 4 9% 6% 6% 6% 4 6% 8% 24%	5204
	11th to 20th	Night	18% 11% 3 7% 5% 5% 5% 4 5% 6% 32%	4999
	21st to end	Night	25% 14% 5% 9% 5% 5% 5% 3 5% 5% 19%	5361
April	1st to 10th	Night	20% 11% 4 8% 6% 5% 4 4 6% 6% 25%	2000
	11th to 20th	Night	15% 10% 3 6% 5% 5% 4 5% 6% 7% 32%	1882
	21st to end	Night	17% 10% 3 8% 6% 5% 4 4 6% 7% 30%	1755
May	1st to 10th	Night	13% 7% 3 7% 4 3 3 3 4 5% 49%	3640
	11th to 20th	Night	13% 7% 3 8% 4 4 4 3 5% 7% 40%	3616
	21st to end	Night	13% 9% 3 8% 6% 6% 6% 5% 6% 7% 31%	3889
June	1st to 10th	Night	16% 8% 3 6% 4 4 5% 4 6% 7% 36%	1400
	11th to 20th	Night	12% 8% 3 7% 6% 4 5% 4 7% 7% 36%	1400
	21st to end	Night	9% 7% 1 7% 4 4 4 3 7% 10% 44%	1400
July	1st to 10th	Night	7% 3 1 4 2 3 3 2 4 6% 65%	3180
	11th to 20th	Night	3 2 1 2 1 2 2 2 3 4 78%	3180
	21st to end	Night	6% 3 1 3 2 3 3 2 4 5% 66%	3896
August	1st to 10th	Night	4 2 1 3 2 2 2 3 4 7% 72%	2674
	11th to 20th	Night	11% 5% 2 5% 3 3 4 3 4 7% 53%	2902
	21st to end	Night	10% 4 1 4 4 4 4 4 6% 9% 51%	3363
September	1st to 10th	Night	6% 3 1 4 3 3 4 3 5% 7% 61%	2000
	11th to 20th	Night	13% 6% 3 6% 4 4 3 3 5% 6% 46%	2005
	21st to end	Night	16% 6% 3 6% 5% 3 4 3 5% 7% 43%	2292
October	1st to 10th	Night	14% 6% 2 6% 5% 4 5% 4 5% 7% 42%	3920
	11th to 20th	Night	25% 8% 3 6% 3 4 5% 3 5% 6% 32%	3897
	21st to end	Night	24% 10% 4 8% 4 4 4 3 5% 6% 29%	4484
November	1st to 10th	Night	31% 10% 4 8% 5% 5% 5% 3 4 5% 20%	2870
	11th to 20th	Night	30% 11% 3 8% 4 4 4 3 5% 6% 22%	2940
	21st to end	Night	28% 11% 4 9% 6% 4 5% 3 4 5% 20%	2940
December	1st to 10th	Night	21% 11% 4 11% 6% 5% 5% 4 6% 6% 21%	4700
	11th to 20th	Night	35% 15% 5% 10% 5% 4 4 3 3 4 12%	5694
	21st to end	Night	26% 13% 4 10% 6% 5% 5% 4 4 4 18%	7623

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	53% 33% 7% 6% 1	3249
	11th to 20th	Day	36% 31% 12% 14% 5% 2	3243
	21st to end	Day	49% 32% 8% 10% 1	4114
February	1st to 10th	Day	26% 63% 3 4 2 2	1800
	11th to 20th	Day	27% 62% 2 6% 2	1764
	21st to end	Day	25% 63% 5% 4 2 1	1505
March	1st to 10th	Day	40% 36% 11% 10% 3	4689
	11th to 20th	Day	37% 32% 11% 16% 3	5000
	21st to end	Day	46% 34% 12% 6% 2	5613
April	1st to 10th	Day	21% 65% 7% 7%	2400
	11th to 20th	Day	18% 65% 6% 7% 3 1	2464
	21st to end	Day	18% 64% 7% 8% 3	2643
May	1st to 10th	Day	25% 31% 15% 19% 11% 1	6320
	11th to 20th	Day	31% 35% 18% 14% 2	6280
	21st to end	Day	31% 34% 19% 13% 2	6984
June	1st to 10th	Day	14% 63% 10% 9% 3	3000
	11th to 20th	Day	17% 63% 7% 9% 3	3000
	21st to end	Day	14% 62% 10% 10% 3	3000
July	1st to 10th	Day	14% 28% 16% 18% 17% 6%	6706
	11th to 20th	Day	8% 26% 16% 26% 21% 3	6699
	21st to end	Day	16% 28% 27% 22% 7% 1	6738
August	1st to 10th	Day	7% 37% 9% 32% 14% 1	4445
	11th to 20th	Day	22% 41% 21% 12% 3 1	4195
	21st to end	Day	26% 39% 13% 15% 7% 1	4547
September	1st to 10th	Day	16% 60% 10% 9% 4 1	2400
	11th to 20th	Day	20% 59% 6% 8% 6%	2393
	21st to end	Day	20% 59% 8% 8% 4	2107
October	1st to 10th	Day	30% 40% 12% 16% 2	3280
	11th to 20th	Day	40% 38% 7% 10% 6%	3261
	21st to end	Day	41% 40% 8% 9% 3	3316
November	1st to 10th	Day	31% 56% 8% 4 1	1648
	11th to 20th	Day	28% 57% 6% 7% 2 1	1680
	21st to end	Day	30% 56% 5% 5% 4	1680
December	1st to 10th	Day	42% 39% 7% 10% 2	2700
	11th to 20th	Day	53% 34% 6% 5% 1	2731
	21st to end	Day	56% 31% 8% 4 1	3575
January	1st to 10th	Night	55% 31% 7% 6% 1	6916
	11th to 20th	Night	30% 31% 16% 17% 5% 1	6847
	21st to end	Night	46% 31% 8% 12% 2	6847
February	1st to 10th	Night	25% 63% 3 3 3 2	2600
	11th to 20th	Night	27% 62% 3 5% 2 1	2534
	21st to end	Night	22% 63% 6% 6% 3 1	2125
March	1st to 10th	Night	37% 35% 12% 10% 6%	5204
	11th to 20th	Night	34% 33% 12% 18% 3	5000
	21st to end	Night	49% 34% 10% 6% 1	5361
April	1st to 10th	Night	23% 63% 6% 8% 1	2000
	11th to 20th	Night	19% 64% 6% 7% 4 1	1882
	21st to end	Night	19% 63% 7% 7% 4	1755
May	1st to 10th	Night	26% 31% 7% 25% 10% 1	3637
	11th to 20th	Night	32% 33% 18% 14% 3	3616
	21st to end	Night	37% 33% 15% 14% 1	3889
June	1st to 10th	Night	15% 62% 8% 10% 4 1	1400
	11th to 20th	Night	16% 63% 6% 11% 3	1400
	21st to end	Night	15% 62% 9% 10% 4	1400
July	1st to 10th	Night	15% 27% 14% 22% 16% 7%	3145
	11th to 20th	Night	7% 25% 14% 26% 25% 3	3138
	21st to end	Night	18% 27% 18% 26% 11% 1	3786
August	1st to 10th	Night	7% 35% 8% 26% 22% 1	2666
	11th to 20th	Night	25% 39% 19% 12% 4 1	2929
	21st to end	Night	21% 40% 15% 16% 8%	3363
September	1st to 10th	Night	13% 60% 10% 11% 6% 1	2000
	11th to 20th	Night	20% 57% 7% 8% 7% 1	2005
	21st to end	Night	18% 59% 8% 10% 5%	2292
October	1st to 10th	Night	28% 39% 15% 15% 3	3920
	11th to 20th	Night	36% 38% 8% 14% 4	3897
	21st to end	Night	36% 39% 11% 11% 4	4484
November	1st to 10th	Night	31% 55% 7% 6% 1	2870
	11th to 20th	Night	28% 55% 6% 5% 3 2	2940
	21st to end	Night	30% 56% 5% 5% 4 1	2940
December	1st to 10th	Night	40% 39% 8% 10% 3	4700
	11th to 20th	Night	55% 34% 6% 4 1	5690
	21st to end	Night	51% 32% 8% 9% 1	7623

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	34% 12% 21% 19% 11% 4	220
	11th to 20th	Day	30% 14% 18% 19% 16% 2	212
	21st to end	Day	38% 6% 17% 23% 11% 5%	265
February	1st to 10th	Day	31% 11% 20% 21% 16% 2	400
	11th to 20th	Day	31% 6% 19% 26% 15% 3	395
	21st to end	Day	27% 9% 18% 28% 13% 5%	341
March	1st to 10th	Day	27% 7% 17% 23% 21% 5%	500
	11th to 20th	Day	24% 8% 19% 21% 21% 7%	500
	21st to end	Day	25% 7% 17% 29% 18% 4	550
April	1st to 10th	Day	24% 7% 17% 26% 19% 6%	500
	11th to 20th	Day	19% 4 17% 33% 19% 8%	492
	21st to end	Day	18% 5% 15% 29% 24% 10%	500
May	1st to 10th	Day	12% 4 10% 34% 33% 8%	503
	11th to 20th	Day	14% 3 6% 29% 32% 14%	528
	21st to end	Day	14% 3 10% 29% 31% 13%	601
June	1st to 10th	Day	14% 4 12% 30% 31% 9%	730
	11th to 20th	Day	14% 3 14% 32% 27% 11%	730
	21st to end	Day	10% 2 10% 26% 37% 15%	730
July	1st to 10th	Day	9% 1 7% 25% 39% 19%	721
	11th to 20th	Day	5% 1 7% 25% 42% 20%	718
	21st to end	Day	5% 1 4 18% 43% 29%	608
August	1st to 10th	Day	5% 1 5% 17% 40% 31%	527
	11th to 20th	Day	5% 2 4 26% 39% 24%	517
	21st to end	Day	10% 1 8% 25% 36% 20%	583
September	1st to 10th	Day	9% 2 10% 26% 34% 18%	530
	11th to 20th	Day	14% 2 12% 27% 31% 14%	530
	21st to end	Day	18% 5% 14% 29% 27% 9%	530
October	1st to 10th	Day	22% 4 15% 23% 26% 10%	530
	11th to 20th	Day	28% 6% 14% 23% 21% 8%	530
	21st to end	Day	28% 8% 21% 24% 14% 4	453
November	1st to 10th	Day	29% 11% 20% 27% 12% 2	220
	11th to 20th	Day	31% 8% 19% 17% 17% 8%	220
	21st to end	Day	35% 6% 20% 20% 12% 8%	220
December	1st to 10th	Day	36% 8% 18% 15% 16% 6%	220
	11th to 20th	Day	38% 14% 17% 22% 8%	220
	21st to end	Day	35% 13% 24% 18% 10%	242
January	1st to 10th	Night	39% 10% 20% 18% 10% 2	950
	11th to 20th	Night	35% 8% 16% 21% 18% 2	925
	21st to end	Night	33% 7% 18% 22% 16% 4	880
February	1st to 10th	Night	33% 11% 19% 23% 11% 3	800
	11th to 20th	Night	27% 8% 22% 26% 15% 2	784
	21st to end	Night	29% 12% 21% 22% 13% 3	660
March	1st to 10th	Night	26% 8% 24% 23% 16% 5%	800
	11th to 20th	Night	29% 9% 22% 20% 18% 4	800
	21st to end	Night	29% 8% 18% 25% 15% 5%	880
April	1st to 10th	Night	23% 7% 17% 29% 18% 5%	800
	11th to 20th	Night	21% 4 20% 30% 18% 6%	694
	21st to end	Night	21% 5% 16% 32% 20% 6%	555
May	1st to 10th	Night	14% 4 14% 30% 31% 8%	400
	11th to 20th	Night	15% 2 10% 27% 37% 9%	394
	21st to end	Night	15% 4 10% 29% 36% 7%	433
June	1st to 10th	Night	18% 4 14% 30% 29% 6%	400
	11th to 20th	Night	14% 3 18% 33% 25% 7%	400
	21st to end	Night	11% 3 11% 28% 39% 9%	400
July	1st to 10th	Night	10% 6% 27% 46% 11%	390
	11th to 20th	Night	4 2 10% 30% 43% 11%	388
	21st to end	Night	4 6% 27% 46% 16%	438
August	1st to 10th	Night	8% 2 7% 16% 44% 23%	437
	11th to 20th	Night	7% 1 4 24% 47% 17%	594
	21st to end	Night	10% 2 8% 24% 46% 11%	726
September	1st to 10th	Night	9% 1 7% 30% 37% 16%	800
	11th to 20th	Night	16% 3 12% 19% 33% 18%	800
	21st to end	Night	20% 3 14% 25% 31% 8%	800
October	1st to 10th	Night	19% 3 15% 25% 26% 13%	800
	11th to 20th	Night	27% 6% 16% 23% 21% 8%	800
	21st to end	Night	28% 8% 20% 26% 15% 4	880
November	1st to 10th	Night	35% 8% 21% 23% 13% 1	820
	11th to 20th	Night	35% 9% 19% 22% 13% 3	840
	21st to end	Night	34% 8% 18% 23% 13% 4	840
December	1st to 10th	Night	32% 8% 17% 25% 16% 3	840
	11th to 20th	Night	40% 11% 23% 18% 8% 1	942
	21st to end	Night	38% 10% 26% 18% 7% 1	1045

Page generated at 2026-01-13 22:14:25. Version ac07

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