Poulsbo Deep Space Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Poulsbo Deep Space Observatory clear sky chart from 2005-11-06 to 2025-11-18.

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	14% 10% 3 8% 5% 5% 5% 4 5% 7% 33%	131227
	Night	16% 10% 3 8% 5% 5% 5% 4 5% 6% 32%	127811
Transparency	Day	49% 8% 16% 19% 8% 1	130940
	Night	53% 8% 14% 17% 7% 1	127675
Seeing	Day	21% 8% 19% 27% 19% 6%	16511
	Night	25% 7% 16% 28% 20% 3	24811

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	22% 16% 4 13% 7% 5% 6% 3 5% 5% 12%	3179
	11th to 20th	Day	13% 10% 4 11% 7% 6% 5% 5% 6% 9% 24%	3504
	21st to end	Day	17% 15% 4 11% 6% 5% 5% 4 5% 6% 22%	4142
February	1st to 10th	Day	16% 15% 4 10% 6% 6% 6% 5% 6% 7% 19%	1800
	11th to 20th	Day	14% 14% 4 10% 7% 5% 6% 4 6% 7% 22%	1755
	21st to end	Day	14% 15% 5% 10% 6% 5% 5% 4 6% 6% 24%	1535
March	1st to 10th	Day	12% 13% 5% 10% 7% 6% 7% 5% 7% 8% 20%	4663
	11th to 20th	Day	13% 12% 4 10% 6% 6% 6% 4 6% 6% 29%	5000
	21st to end	Day	14% 11% 4 11% 8% 7% 8% 6% 7% 8% 17%	5650
April	1st to 10th	Day	17% 14% 5% 9% 6% 5% 5% 5% 7% 7% 21%	2400
	11th to 20th	Day	16% 10% 3 9% 6% 6% 4 4 5% 8% 28%	2417
	21st to end	Day	15% 11% 4 8% 6% 6% 5% 4 6% 7% 27%	2635
May	1st to 10th	Day	15% 8% 2 6% 4 4 4 3 5% 6% 41%	6320
	11th to 20th	Day	17% 11% 3 8% 6% 5% 4 5% 6% 8% 28%	6277
	21st to end	Day	20% 9% 3 7% 5% 5% 5% 4 6% 8% 27%	6903
June	1st to 10th	Day	18% 8% 3 8% 6% 5% 4 5% 6% 7% 30%	2895
	11th to 20th	Day	19% 10% 4 8% 7% 6% 6% 5% 6% 6% 23%	3000
	21st to end	Day	12% 7% 3 7% 5% 5% 5% 4 7% 7% 38%	3000
July	1st to 10th	Day	10% 5% 1 4 3 3 3 2 4 6% 59%	6780
	11th to 20th	Day	5% 4 1 4 3 3 3 2 3 4 66%	6580
	21st to end	Day	10% 7% 2 5% 3 4 4 3 4 6% 52%	6874
August	1st to 10th	Day	6% 4 1 5% 3 3 4 3 5% 7% 58%	4446
	11th to 20th	Day	10% 7% 3 8% 4 4 4 4 6% 8% 42%	4156
	21st to end	Day	14% 8% 3 7% 4 4 4 3 4 5% 43%	4489
September	1st to 10th	Day	9% 7% 3 5% 3 4 4 3 5% 7% 51%	2400
	11th to 20th	Day	11% 7% 2 8% 5% 4 4 4 6% 7% 41%	2400
	21st to end	Day	12% 7% 3 7% 5% 5% 5% 4 6% 7% 41%	2106
October	1st to 10th	Day	11% 8% 3 7% 5% 5% 5% 4 7% 9% 37%	3280
	11th to 20th	Day	22% 9% 3 9% 5% 5% 4 4 5% 7% 26%	3261
	21st to end	Day	16% 11% 4 12% 6% 6% 6% 4 6% 7% 21%	3373
November	1st to 10th	Day	19% 13% 5% 10% 6% 6% 7% 4 5% 6% 19%	1672
	11th to 20th	Day	20% 13% 4 7% 7% 5% 5% 4 5% 8% 22%	1656
	21st to end	Day	20% 13% 4 9% 6% 5% 5% 3 6% 8% 21%	1600
December	1st to 10th	Day	15% 10% 3 14% 8% 6% 6% 4 6% 7% 20%	2620
	11th to 20th	Day	22% 13% 6% 11% 7% 6% 6% 4 6% 7% 13%	2961
	21st to end	Day	19% 14% 5% 12% 7% 6% 5% 4 5% 6% 15%	3498
January	1st to 10th	Night	20% 16% 5% 11% 7% 6% 6% 4 5% 6% 13%	6766
	11th to 20th	Night	13% 10% 4 11% 5% 4 5% 4 5% 8% 31%	6376
	21st to end	Night	20% 12% 3 7% 5% 5% 5% 4 5% 7% 26%	6803
February	1st to 10th	Night	17% 16% 4 10% 6% 4 5% 4 5% 8% 22%	2600
	11th to 20th	Night	15% 13% 4 9% 6% 5% 5% 4 6% 6% 27%	2532
	21st to end	Night	15% 14% 4 10% 5% 5% 5% 5% 5% 7% 25%	2094
March	1st to 10th	Night	12% 13% 5% 9% 6% 6% 6% 5% 7% 8% 21%	5227
	11th to 20th	Night	13% 13% 4 9% 5% 5% 4 3 6% 7% 32%	4999
	21st to end	Night	20% 13% 4 10% 6% 6% 5% 4 6% 6% 19%	5324
April	1st to 10th	Night	16% 11% 4 9% 6% 6% 6% 5% 6% 8% 22%	2000
	11th to 20th	Night	15% 10% 3 8% 5% 5% 5% 4 6% 7% 31%	1930
	21st to end	Night	17% 10% 4 7% 5% 5% 5% 4 6% 8% 29%	1765
May	1st to 10th	Night	14% 9% 2 5% 3 4 4 3 4 6% 46%	3640
	11th to 20th	Night	19% 8% 4 8% 4 4 4 3 4 5% 36%	3616
	21st to end	Night	20% 9% 2 7% 5% 5% 5% 4 6% 8% 29%	3972
June	1st to 10th	Night	17% 9% 2 8% 5% 4 5% 4 6% 6% 35%	1500
	11th to 20th	Night	21% 10% 4 8% 6% 4 5% 4 6% 7% 27%	1400
	21st to end	Night	11% 6% 2 7% 4 3 5% 3 8% 7% 44%	1400
July	1st to 10th	Night	15% 5% 2 4 3 3 2 2 3 4 58%	3180
	11th to 20th	Night	5% 3 1 3 2 1 2 2 3 4 75%	3364
	21st to end	Night	13% 5% 2 4 3 3 3 3 4 6% 55%	3969
August	1st to 10th	Night	5% 2 1 4 3 3 3 3 3 5% 67%	2703
	11th to 20th	Night	13% 5% 3 6% 4 4 2 2 4 6% 49%	2902
	21st to end	Night	16% 6% 2 6% 4 3 3 2 4 6% 48%	3425
September	1st to 10th	Night	7% 4 2 5% 3 4 3 4 5% 6% 56%	2000
	11th to 20th	Night	12% 8% 3 6% 6% 4 4 3 5% 5% 43%	2000
	21st to end	Night	13% 7% 2 7% 5% 5% 4 4 5% 6% 42%	2289
October	1st to 10th	Night	12% 6% 3 8% 5% 4 5% 4 6% 8% 38%	3920
	11th to 20th	Night	20% 9% 3 8% 5% 5% 5% 3 5% 6% 32%	3897
	21st to end	Night	19% 10% 4 9% 5% 6% 5% 4 5% 7% 27%	4432
November	1st to 10th	Night	21% 10% 3 8% 5% 5% 5% 4 5% 6% 26%	2844
	11th to 20th	Night	20% 12% 4 8% 6% 5% 5% 4 6% 5% 24%	2898
	21st to end	Night	16% 11% 4 9% 7% 6% 7% 4 5% 7% 23%	2800
December	1st to 10th	Night	14% 9% 4 11% 7% 7% 6% 4 5% 7% 26%	4560
	11th to 20th	Night	23% 13% 4 12% 7% 6% 5% 4 5% 6% 14%	5226
	21st to end	Night	20% 16% 5% 11% 7% 6% 6% 4 5% 6% 14%	7458

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	75% 9% 6% 8% 2	3179
	11th to 20th	Day	59% 7% 14% 16% 4 1	3528
	21st to end	Day	64% 6% 10% 13% 6%	4142
February	1st to 10th	Day	67% 9% 11% 8% 4 1	1800
	11th to 20th	Day	67% 8% 9% 9% 7% 1	1764
	21st to end	Day	63% 8% 13% 11% 5%	1535
March	1st to 10th	Day	62% 8% 13% 13% 4	4663
	11th to 20th	Day	55% 9% 12% 20% 3	5000
	21st to end	Day	64% 10% 14% 11% 1	5650
April	1st to 10th	Day	60% 10% 17% 12% 1	2400
	11th to 20th	Day	54% 8% 14% 16% 7% 2	2417
	21st to end	Day	54% 8% 16% 16% 6% 1	2635
May	1st to 10th	Day	41% 7% 16% 25% 10% 1	6320
	11th to 20th	Day	49% 10% 19% 18% 4	6280
	21st to end	Day	48% 9% 23% 17% 2	6904
June	1st to 10th	Day	46% 9% 20% 17% 6% 1	2895
	11th to 20th	Day	53% 8% 20% 15% 4	3000
	21st to end	Day	40% 9% 22% 21% 7% 1	3000
July	1st to 10th	Day	24% 6% 18% 23% 20% 9%	6706
	11th to 20th	Day	17% 5% 15% 32% 29% 3	6499
	21st to end	Day	25% 5% 25% 31% 12% 1	6681
August	1st to 10th	Day	21% 6% 15% 38% 18% 2	4429
	11th to 20th	Day	37% 9% 21% 24% 8% 2	4195
	21st to end	Day	42% 5% 13% 28% 11% 1	4488
September	1st to 10th	Day	32% 7% 19% 25% 12% 4	2400
	11th to 20th	Day	42% 8% 16% 19% 15% 1	2400
	21st to end	Day	46% 7% 18% 19% 9% 2	2106
October	1st to 10th	Day	42% 9% 19% 25% 5%	3280
	11th to 20th	Day	60% 6% 13% 14% 6%	3261
	21st to end	Day	63% 8% 12% 11% 6% 1	3373
November	1st to 10th	Day	65% 9% 13% 10% 4	1672
	11th to 20th	Day	65% 7% 10% 11% 5% 1	1656
	21st to end	Day	66% 9% 9% 11% 6%	1600
December	1st to 10th	Day	62% 8% 10% 14% 6%	2620
	11th to 20th	Day	73% 8% 9% 8% 1	2964
	21st to end	Day	73% 8% 11% 7% 2	3498
January	1st to 10th	Night	76% 8% 7% 7% 2	6766
	11th to 20th	Night	50% 10% 14% 22% 4	6414
	21st to end	Night	59% 8% 11% 17% 5%	6803
February	1st to 10th	Night	64% 8% 11% 11% 5% 1	2600
	11th to 20th	Night	61% 7% 12% 11% 7% 1	2534
	21st to end	Night	60% 7% 13% 14% 4	2094
March	1st to 10th	Night	58% 11% 12% 14% 5%	5227
	11th to 20th	Night	51% 10% 15% 21% 2	5000
	21st to end	Night	66% 10% 13% 10% 1	5324
April	1st to 10th	Night	58% 12% 14% 14% 2	2000
	11th to 20th	Night	52% 7% 15% 15% 8% 2	1930
	21st to end	Night	55% 9% 15% 14% 6% 1	1765
May	1st to 10th	Night	42% 6% 12% 30% 10% 1	3637
	11th to 20th	Night	49% 9% 20% 16% 5%	3616
	21st to end	Night	53% 13% 19% 13% 1	3972
June	1st to 10th	Night	48% 9% 19% 16% 6% 1	1500
	11th to 20th	Night	56% 9% 16% 16% 3	1400
	21st to end	Night	40% 6% 24% 20% 7% 3	1400
July	1st to 10th	Night	33% 4 15% 20% 18% 11%	3145
	11th to 20th	Night	15% 4 17% 30% 33% 2	3322
	21st to end	Night	27% 6% 22% 29% 14% 2	3857
August	1st to 10th	Night	20% 4 14% 39% 21% 2	2695
	11th to 20th	Night	35% 7% 23% 22% 11% 2	2929
	21st to end	Night	39% 6% 15% 27% 12% 1	3425
September	1st to 10th	Night	29% 7% 18% 27% 14% 5%	2000
	11th to 20th	Night	43% 7% 12% 19% 15% 4	2000
	21st to end	Night	45% 7% 13% 25% 9% 1	2289
October	1st to 10th	Night	42% 8% 19% 27% 5%	3920
	11th to 20th	Night	54% 6% 14% 20% 6%	3897
	21st to end	Night	60% 8% 12% 13% 6%	4432
November	1st to 10th	Night	62% 7% 14% 12% 4 1	2844
	11th to 20th	Night	65% 7% 11% 10% 4 2	2898
	21st to end	Night	64% 7% 11% 11% 6%	2800
December	1st to 10th	Night	60% 8% 11% 16% 5%	4560
	11th to 20th	Night	73% 8% 11% 6% 2	5222
	21st to end	Night	72% 9% 9% 8% 2	7458

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% 12% 22% 18% 10% 5%	200
	11th to 20th	Day	31% 11% 22% 15% 17% 5%	200
	21st to end	Day	35% 11% 22% 18% 10% 4	280
February	1st to 10th	Day	35% 11% 21% 22% 10% 2	400
	11th to 20th	Day	32% 12% 26% 20% 8% 2	395
	21st to end	Day	31% 11% 24% 21% 11% 3	357
March	1st to 10th	Day	27% 14% 24% 22% 10% 3	500
	11th to 20th	Day	27% 12% 22% 19% 15% 5%	500
	21st to end	Day	29% 11% 26% 22% 10% 2	550
April	1st to 10th	Day	25% 11% 24% 23% 12% 4	500
	11th to 20th	Day	22% 12% 29% 21% 11% 5%	492
	21st to end	Day	20% 7% 25% 30% 14% 4	500
May	1st to 10th	Day	15% 6% 23% 34% 19% 4	503
	11th to 20th	Day	19% 5% 17% 30% 20% 9%	528
	21st to end	Day	21% 6% 15% 29% 20% 9%	573
June	1st to 10th	Day	19% 5% 19% 33% 19% 5%	625
	11th to 20th	Day	20% 5% 20% 30% 20% 5%	730
	21st to end	Day	12% 5% 18% 34% 23% 8%	730
July	1st to 10th	Day	12% 3 14% 32% 29% 10%	721
	11th to 20th	Day	6% 2 14% 32% 34% 11%	635
	21st to end	Day	7% 3 8% 32% 35% 15%	575
August	1st to 10th	Day	8% 2 7% 30% 36% 16%	527
	11th to 20th	Day	8% 2 12% 35% 31% 13%	517
	21st to end	Day	12% 4 15% 35% 26% 8%	583
September	1st to 10th	Day	12% 4 16% 34% 27% 6%	530
	11th to 20th	Day	14% 8% 16% 30% 24% 7%	530
	21st to end	Day	18% 8% 22% 29% 19% 4	530
October	1st to 10th	Day	20% 8% 21% 26% 18% 7%	530
	11th to 20th	Day	27% 9% 19% 24% 17% 5%	530
	21st to end	Day	31% 13% 20% 22% 12% 2	473
November	1st to 10th	Day	39% 6% 26% 20% 6% 3	233
	11th to 20th	Day	36% 17% 17% 15% 9% 6%	214
	21st to end	Day	32% 10% 23% 18% 11% 7%	200
December	1st to 10th	Day	31% 12% 16% 18% 17% 8%	200
	11th to 20th	Day	35% 16% 28% 14% 7% 1	200
	21st to end	Day	33% 13% 20% 25% 6% 3	220
January	1st to 10th	Night	38% 8% 19% 19% 13% 2	900
	11th to 20th	Night	32% 7% 16% 26% 17% 2	820
	21st to end	Night	31% 7% 17% 26% 14% 4	880
February	1st to 10th	Night	33% 10% 20% 25% 11% 2	800
	11th to 20th	Night	29% 9% 18% 27% 15% 2	784
	21st to end	Night	31% 8% 20% 27% 11% 2	660
March	1st to 10th	Night	25% 10% 22% 27% 15% 2	800
	11th to 20th	Night	27% 14% 17% 25% 14% 2	800
	21st to end	Night	27% 10% 23% 28% 11% 1	880
April	1st to 10th	Night	25% 8% 19% 28% 18% 2	800
	11th to 20th	Night	22% 9% 19% 31% 16% 3	742
	21st to end	Night	25% 5% 17% 33% 16% 3	565
May	1st to 10th	Night	20% 7% 15% 36% 21% 2	400
	11th to 20th	Night	20% 3 11% 34% 28% 4	394
	21st to end	Night	21% 5% 10% 32% 25% 5%	433
June	1st to 10th	Night	20% 6% 16% 34% 21% 3	400
	11th to 20th	Night	23% 6% 14% 36% 19% 3	400
	21st to end	Night	15% 3 14% 37% 28% 3	400
July	1st to 10th	Night	12% 4 8% 34% 36% 5%	390
	11th to 20th	Night	8% 2 9% 38% 38% 5%	388
	21st to end	Night	9% 3 6% 34% 42% 5%	438
August	1st to 10th	Night	10% 2 4 28% 44% 11%	453
	11th to 20th	Night	10% 2 5% 28% 43% 11%	594
	21st to end	Night	14% 2 9% 34% 36% 5%	762
September	1st to 10th	Night	11% 2 9% 38% 34% 6%	800
	11th to 20th	Night	18% 3 11% 26% 33% 10%	800
	21st to end	Night	17% 7% 16% 32% 24% 4	800
October	1st to 10th	Night	18% 7% 16% 29% 25% 5%	800
	11th to 20th	Night	26% 6% 16% 27% 22% 4	800
	21st to end	Night	28% 9% 18% 27% 16% 2	880
November	1st to 10th	Night	35% 9% 18% 27% 11%	820
	11th to 20th	Night	35% 9% 19% 22% 13% 2	828
	21st to end	Night	30% 9% 18% 25% 14% 4	800
December	1st to 10th	Night	27% 9% 16% 27% 17% 3	800
	11th to 20th	Night	35% 11% 20% 21% 12% 1	810
	21st to end	Night	39% 10% 19% 21% 9% 1	990

Page generated at 2025-11-14 21:55:54. Version ac07

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