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 2024-11-25.

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	17% 8% 3 7% 5% 4 4 4 5% 6% 37%	105661
	Night	20% 9% 3 7% 5% 4 4 3 5% 6% 33%	102412
Transparency	Day	24% 49% 10% 11% 5% 1	105411
	Night	28% 49% 8% 10% 5% 1	102308
Seeing	Day	18% 5% 13% 26% 27% 11%	15413
	Night	25% 6% 16% 24% 22% 6%	23625

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% 15% 5% 10% 6% 5% 5% 3 4 4 11%	2219
	11th to 20th	Day	24% 15% 5% 9% 6% 4 4 3 4 5% 21%	2206
	21st to end	Day	38% 17% 5% 10% 5% 4 4 3 4 3 8%	2862
February	1st to 10th	Day	27% 13% 4 9% 7% 5% 4 3 5% 6% 17%	1710
	11th to 20th	Day	24% 13% 4 10% 5% 4 4 3 5% 5% 22%	1665
	21st to end	Day	21% 14% 4 8% 7% 6% 5% 4 5% 6% 19%	1432
March	1st to 10th	Day	18% 12% 4 9% 6% 6% 6% 5% 7% 9% 18%	3257
	11th to 20th	Day	17% 9% 3 8% 5% 4 4 4 5% 6% 34%	3490
	21st to end	Day	20% 12% 4 9% 6% 4 5% 4 5% 5% 26%	3913
April	1st to 10th	Day	20% 11% 3 8% 6% 6% 5% 5% 7% 7% 23%	2280
	11th to 20th	Day	17% 11% 3 8% 5% 6% 4 5% 6% 8% 29%	2339
	21st to end	Day	18% 9% 3 7% 5% 5% 6% 5% 6% 7% 30%	2511
May	1st to 10th	Day	13% 7% 2 6% 5% 4 4 4 5% 5% 46%	4420
	11th to 20th	Day	9% 6% 2 6% 4 5% 5% 4 6% 10% 42%	4377
	21st to end	Day	19% 10% 3 8% 5% 4 4 4 6% 7% 30%	4865
June	1st to 10th	Day	15% 8% 2 7% 5% 4 5% 4 6% 8% 36%	2850
	11th to 20th	Day	14% 7% 3 8% 5% 5% 5% 5% 6% 7% 36%	2850
	21st to end	Day	10% 5% 2 6% 5% 5% 5% 4 6% 8% 44%	2850
July	1st to 10th	Day	5% 3 1 3 2 3 3 2 3 4 71%	4740
	11th to 20th	Day	4 2 1 3 2 2 2 2 3 5% 73%	4740
	21st to end	Day	9% 4 1 3 2 2 3 3 4 6% 62%	4835
August	1st to 10th	Day	4 3 1 3 2 2 3 2 4 5% 72%	4324
	11th to 20th	Day	9% 4 2 6% 4 5% 4 4 5% 7% 49%	4026
	21st to end	Day	12% 6% 2 7% 5% 4 4 3 5% 7% 45%	4409
September	1st to 10th	Day	8% 5% 3 5% 4 4 4 3 4 8% 50%	2280
	11th to 20th	Day	12% 7% 3 8% 5% 4 4 3 5% 7% 41%	2274
	21st to end	Day	17% 8% 3 6% 4 4 3 3 5% 7% 39%	2002
October	1st to 10th	Day	18% 5% 2 7% 5% 5% 7% 5% 7% 8% 30%	3180
	11th to 20th	Day	29% 9% 3 8% 5% 4 4 4 5% 6% 24%	3161
	21st to end	Day	22% 11% 3 10% 5% 6% 4 4 6% 6% 23%	3214
November	1st to 10th	Day	30% 11% 3 7% 6% 5% 5% 4 5% 5% 18%	1568
	11th to 20th	Day	28% 12% 3 9% 5% 4 5% 3 5% 5% 22%	1600
	21st to end	Day	30% 11% 4 9% 5% 4 5% 4 5% 5% 18%	1552
December	1st to 10th	Day	26% 14% 4 8% 5% 4 4 4 4 5% 22%	1520
	11th to 20th	Day	29% 14% 5% 13% 6% 5% 5% 3 4 4 11%	1698
	21st to end	Day	26% 16% 5% 11% 6% 5% 5% 3 5% 5% 11%	2442
January	1st to 10th	Night	29% 14% 5% 12% 6% 5% 5% 4 4 4 13%	4726
	11th to 20th	Night	28% 10% 3 8% 5% 4 3 3 4 8% 24%	4690
	21st to end	Night	40% 13% 3 9% 4 4 3 3 4 4 13%	4796
February	1st to 10th	Night	28% 13% 3 8% 5% 4 4 3 5% 5% 21%	2470
	11th to 20th	Night	22% 12% 4 9% 5% 4 4 3 4 5% 27%	2402
	21st to end	Night	24% 13% 4 7% 5% 3 4 4 5% 6% 25%	2022
March	1st to 10th	Night	18% 12% 4 9% 6% 6% 6% 4 6% 7% 20%	3616
	11th to 20th	Night	17% 7% 2 6% 4 4 5% 3 6% 7% 39%	3489
	21st to end	Night	22% 14% 5% 9% 6% 5% 4 3 5% 5% 22%	3739
April	1st to 10th	Night	21% 11% 3 8% 6% 5% 4 5% 6% 6% 25%	1900
	11th to 20th	Night	16% 11% 3 6% 5% 6% 4 5% 6% 7% 32%	1787
	21st to end	Night	18% 11% 3 8% 6% 5% 4 4 6% 7% 28%	1667
May	1st to 10th	Night	13% 7% 3 7% 4 4 4 3 4 5% 47%	2540
	11th to 20th	Night	8% 5% 2 6% 4 4 4 3 5% 8% 51%	2516
	21st to end	Night	16% 11% 3 7% 6% 6% 5% 5% 6% 6% 30%	2707
June	1st to 10th	Night	17% 8% 3 7% 4 4 5% 4 6% 6% 34%	1330
	11th to 20th	Night	12% 8% 3 7% 6% 4 5% 4 7% 7% 36%	1330
	21st to end	Night	9% 7% 1 7% 4 4 4 4 7% 9% 44%	1330
July	1st to 10th	Night	5% 3 1 4 2 3 3 2 4 6% 67%	2220
	11th to 20th	Night	3 2 1 2 2 2 3 2 3 4 77%	2220
	21st to end	Night	8% 5% 2 4 3 3 3 3 5% 5% 60%	2717
August	1st to 10th	Night	3 2 1 3 2 2 2 2 4 6% 72%	2592
	11th to 20th	Night	11% 5% 2 5% 3 3 4 3 4 7% 53%	2812
	21st to end	Night	10% 4 1 5% 4 4 4 4 6% 9% 50%	3260
September	1st to 10th	Night	7% 3 1 4 3 3 4 3 5% 7% 61%	1900
	11th to 20th	Night	14% 6% 3 6% 4 4 4 3 5% 6% 46%	1905
	21st to end	Night	15% 6% 3 6% 5% 3 4 3 5% 7% 44%	2177
October	1st to 10th	Night	14% 6% 2 6% 5% 4 5% 4 5% 7% 42%	3800
	11th to 20th	Night	25% 8% 2 6% 4 4 5% 3 5% 6% 31%	3777
	21st to end	Night	24% 10% 4 8% 4 4 4 3 5% 6% 29%	4344
November	1st to 10th	Night	31% 10% 4 8% 5% 5% 5% 3 4 5% 20%	2730
	11th to 20th	Night	30% 11% 3 8% 4 4 4 3 5% 6% 23%	2800
	21st to end	Night	27% 12% 3 9% 6% 4 4 4 4 5% 21%	2722
December	1st to 10th	Night	25% 13% 4 8% 6% 4 4 3 5% 6% 24%	2660
	11th to 20th	Night	32% 15% 5% 10% 5% 4 4 3 4 5% 13%	3505
	21st to end	Night	28% 15% 5% 10% 6% 5% 4 3 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	44% 44% 6% 3 2	2219
	11th to 20th	Day	37% 40% 10% 8% 3 3	2227
	21st to end	Day	54% 42% 2 2	2862
February	1st to 10th	Day	24% 66% 3 3 2 1	1710
	11th to 20th	Day	25% 65% 3 5% 2	1674
	21st to end	Day	22% 66% 5% 4 2 1	1432
March	1st to 10th	Day	29% 50% 11% 7% 3	3257
	11th to 20th	Day	23% 44% 12% 18% 2	3490
	21st to end	Day	34% 45% 12% 7% 2	3913
April	1st to 10th	Day	20% 68% 6% 6%	2280
	11th to 20th	Day	18% 68% 6% 5% 2 1	2339
	21st to end	Day	17% 67% 5% 7% 3	2511
May	1st to 10th	Day	19% 42% 13% 15% 9% 1	4420
	11th to 20th	Day	17% 46% 20% 14% 2	4380
	21st to end	Day	31% 45% 15% 7% 1	4866
June	1st to 10th	Day	15% 66% 9% 8% 3	2850
	11th to 20th	Day	15% 66% 7% 9% 3	2850
	21st to end	Day	12% 65% 9% 10% 3	2850
July	1st to 10th	Day	9% 36% 5% 18% 22% 9%	4666
	11th to 20th	Day	6% 36% 7% 26% 23% 2	4659
	21st to end	Day	18% 38% 19% 17% 8% 1	4682
August	1st to 10th	Day	6% 37% 8% 32% 15% 1	4307
	11th to 20th	Day	22% 42% 21% 12% 3	4065
	21st to end	Day	26% 40% 13% 15% 6%	4408
September	1st to 10th	Day	16% 63% 9% 8% 5% 1	2280
	11th to 20th	Day	20% 62% 6% 7% 6%	2274
	21st to end	Day	20% 61% 8% 8% 4	2002
October	1st to 10th	Day	29% 41% 12% 16% 2	3180
	11th to 20th	Day	39% 39% 7% 9% 6%	3161
	21st to end	Day	40% 41% 8% 9% 3	3214
November	1st to 10th	Day	30% 58% 7% 4 1	1568
	11th to 20th	Day	25% 59% 5% 7% 2 1	1600
	21st to end	Day	26% 60% 5% 4 3	1552
December	1st to 10th	Day	26% 61% 3 6% 3	1520
	11th to 20th	Day	39% 52% 5% 2 2	1701
	21st to end	Day	47% 43% 7% 2 1	2442
January	1st to 10th	Night	45% 43% 6% 4 2	4726
	11th to 20th	Night	32% 40% 12% 11% 4 1	4731
	21st to end	Night	53% 41% 3 3	4796
February	1st to 10th	Night	23% 66% 3 3 2 2	2470
	11th to 20th	Night	25% 65% 3 4 2 1	2404
	21st to end	Night	19% 66% 5% 6% 3 1	2022
March	1st to 10th	Night	32% 48% 9% 7% 4	3616
	11th to 20th	Night	18% 45% 15% 19% 3	3490
	21st to end	Night	38% 45% 9% 7%	3739
April	1st to 10th	Night	20% 66% 5% 7% 1	1900
	11th to 20th	Night	18% 67% 5% 6% 3 1	1787
	21st to end	Night	19% 66% 5% 5% 4	1667
May	1st to 10th	Night	20% 44% 8% 18% 9% 1	2540
	11th to 20th	Night	14% 45% 21% 16% 4	2516
	21st to end	Night	33% 44% 12% 9% 2	2707
June	1st to 10th	Night	15% 65% 7% 10% 3 1	1330
	11th to 20th	Night	15% 66% 6% 9% 3	1330
	21st to end	Night	13% 65% 8% 9% 4	1330
July	1st to 10th	Night	10% 36% 4 19% 21% 10%	2185
	11th to 20th	Night	7% 35% 4 24% 28% 2	2178
	21st to end	Night	22% 37% 9% 19% 13% 1	2631
August	1st to 10th	Night	6% 36% 7% 26% 23% 1	2584
	11th to 20th	Night	24% 40% 19% 12% 4 1	2839
	21st to end	Night	21% 41% 14% 16% 8%	3260
September	1st to 10th	Night	12% 63% 8% 9% 6% 1	1900
	11th to 20th	Night	20% 60% 6% 6% 7% 1	1905
	21st to end	Night	17% 62% 7% 9% 5%	2177
October	1st to 10th	Night	28% 40% 15% 14% 3	3800
	11th to 20th	Night	36% 39% 8% 14% 3	3777
	21st to end	Night	36% 40% 11% 10% 4	4344
November	1st to 10th	Night	30% 58% 7% 5% 1	2730
	11th to 20th	Night	26% 58% 6% 5% 3 2	2800
	21st to end	Night	27% 60% 4 4 5% 1	2722
December	1st to 10th	Night	26% 61% 3 6% 3	2660
	11th to 20th	Night	40% 52% 5% 2 2	3501
	21st to end	Night	44% 42% 6% 6% 2	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% 19% 17% 14% 2	180
	21st to end	Day	40% 7% 18% 21% 10% 3	240
February	1st to 10th	Day	32% 11% 19% 20% 16% 2	370
	11th to 20th	Day	31% 6% 20% 25% 14% 3	365
	21st to end	Day	26% 9% 19% 28% 14% 4	316
March	1st to 10th	Day	27% 8% 18% 23% 20% 5%	460
	11th to 20th	Day	23% 8% 18% 22% 21% 8%	460
	21st to end	Day	25% 7% 17% 28% 19% 4	506
April	1st to 10th	Day	24% 7% 18% 27% 19% 5%	460
	11th to 20th	Day	21% 4 17% 33% 18% 8%	452
	21st to end	Day	19% 5% 16% 30% 22% 8%	460
May	1st to 10th	Day	12% 4 10% 35% 32% 7%	463
	11th to 20th	Day	14% 3 6% 28% 33% 15%	488
	21st to end	Day	14% 3 10% 29% 30% 13%	555
June	1st to 10th	Day	15% 4 12% 31% 29% 8%	680
	11th to 20th	Day	14% 3 15% 33% 26% 10%	680
	21st to end	Day	10% 1 10% 28% 37% 14%	680
July	1st to 10th	Day	9% 1 7% 26% 39% 18%	671
	11th to 20th	Day	5% 1 7% 26% 41% 20%	668
	21st to end	Day	5% 1 4 19% 44% 26%	563
August	1st to 10th	Day	5% 1 5% 18% 40% 30%	487
	11th to 20th	Day	4 1 4 26% 39% 26%	477
	21st to end	Day	11% 1 8% 26% 36% 17%	539
September	1st to 10th	Day	10% 2 11% 28% 35% 14%	490
	11th to 20th	Day	14% 2 12% 28% 30% 12%	490
	21st to end	Day	18% 5% 14% 26% 27% 9%	490
October	1st to 10th	Day	22% 4 15% 22% 26% 10%	490
	11th to 20th	Day	29% 6% 12% 22% 21% 9%	490
	21st to end	Day	28% 8% 22% 24% 15% 5%	417
November	1st to 10th	Day	29% 10% 21% 27% 12% 2	200
	11th to 20th	Day	29% 9% 21% 17% 17% 9%	200
	21st to end	Day	34% 7% 20% 20% 11% 9%	188
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% 16% 20% 18% 2	846
	21st to end	Night	34% 8% 19% 21% 15% 3	836
February	1st to 10th	Night	34% 11% 19% 23% 11% 3	760
	11th to 20th	Night	27% 8% 22% 26% 15% 2	744
	21st to end	Night	29% 12% 21% 22% 13% 4	628
March	1st to 10th	Night	27% 8% 24% 22% 15% 5%	760
	11th to 20th	Night	28% 8% 21% 20% 18% 4	760
	21st to end	Night	29% 8% 17% 26% 15% 5%	836
April	1st to 10th	Night	24% 7% 18% 29% 18% 5%	760
	11th to 20th	Night	22% 4 20% 30% 18% 6%	659
	21st to end	Night	22% 5% 17% 32% 19% 6%	527
May	1st to 10th	Night	14% 4 14% 31% 30% 7%	380
	11th to 20th	Night	14% 2 9% 27% 38% 9%	374
	21st to end	Night	15% 3 10% 28% 36% 7%	411
June	1st to 10th	Night	19% 3 14% 29% 28% 6%	380
	11th to 20th	Night	14% 3 19% 33% 24% 7%	380
	21st to end	Night	11% 3 11% 29% 38% 9%	380
July	1st to 10th	Night	10% 6% 28% 45% 11%	370
	11th to 20th	Night	5% 2 10% 30% 42% 11%	368
	21st to end	Night	4 7% 27% 47% 14%	416
August	1st to 10th	Night	7% 2 7% 16% 45% 23%	415
	11th to 20th	Night	6% 1 4 23% 48% 18%	564
	21st to end	Night	10% 2 8% 24% 44% 11%	689
September	1st to 10th	Night	9% 1 8% 31% 36% 16%	760
	11th to 20th	Night	17% 3 12% 19% 32% 18%	760
	21st to end	Night	19% 3 14% 25% 31% 8%	760
October	1st to 10th	Night	19% 3 15% 24% 26% 13%	760
	11th to 20th	Night	27% 5% 16% 23% 21% 9%	760
	21st to end	Night	28% 8% 20% 26% 14% 4	836
November	1st to 10th	Night	35% 8% 20% 23% 13% 1	780
	11th to 20th	Night	35% 9% 19% 21% 13% 3	800
	21st to end	Night	34% 8% 18% 22% 13% 4	778
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 2024-11-22 05:02:23. Version ac07

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