Stayton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stayton clear sky chart from 2005-11-06 to 2024-11-02.

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	20% 8% 2 6% 4 3 4 3 4 5% 40%	101524
	Night	23% 10% 3 6% 4 3 3 3 4 5% 36%	97595
Transparency	Day	45% 7% 12% 18% 13% 5%	101268
	Night	50% 7% 11% 16% 11% 4	97440
Seeing	Day	24% 7% 23% 27% 15% 4	14690
	Night	27% 5% 17% 30% 18% 2	23628

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	40% 17% 4 8% 5% 4 4 2 3 3 9%	2539
	11th to 20th	Day	42% 11% 3 7% 5% 4 3 2 2 4 17%	2540
	21st to end	Day	38% 13% 3 7% 4 4 4 3 5% 5% 15%	3096
February	1st to 10th	Day	33% 12% 3 7% 4 4 4 4 5% 6% 18%	1710
	11th to 20th	Day	30% 13% 3 8% 5% 4 4 3 5% 4 20%	1665
	21st to end	Day	32% 17% 3 7% 4 3 3 3 3 5% 20%	1495
March	1st to 10th	Day	23% 18% 4 8% 5% 4 5% 4 5% 5% 20%	3310
	11th to 20th	Day	22% 10% 3 6% 4 3 3 3 3 5% 38%	3490
	21st to end	Day	28% 14% 4 9% 6% 6% 5% 4 4 5% 16%	3903
April	1st to 10th	Day	30% 14% 4 9% 5% 5% 4 3 4 5% 17%	2280
	11th to 20th	Day	27% 12% 3 8% 5% 4 4 3 4 4 25%	2249
	21st to end	Day	25% 10% 3 8% 5% 4 4 3 5% 6% 26%	2449
May	1st to 10th	Day	23% 10% 3 7% 5% 3 5% 3 5% 5% 32%	4317
	11th to 20th	Day	13% 5% 2 5% 4 3 3 3 4 6% 52%	4377
	21st to end	Day	21% 9% 3 8% 6% 5% 5% 4 6% 7% 28%	4813
June	1st to 10th	Day	25% 8% 2 6% 4 4 3 4 4 5% 34%	2660
	11th to 20th	Day	21% 7% 3 7% 5% 5% 5% 4 6% 6% 32%	2660
	21st to end	Day	10% 5% 1 4 3 3 4 2 4 6% 57%	2660
July	1st to 10th	Day	4 2 1 2 1 1 2 2 3 4 78%	4420
	11th to 20th	Day	4 2 1 2 1 2 2 2 3 4 77%	4420
	21st to end	Day	5% 2 1 2 1 1 2 1 2 3 78%	4772
August	1st to 10th	Day	3 2 1 3 2 2 3 2 4 5% 72%	4091
	11th to 20th	Day	6% 3 1 4 3 3 3 3 5% 7% 62%	4026
	21st to end	Day	7% 5% 1 4 3 3 3 3 4 6% 60%	4283
September	1st to 10th	Day	8% 3 1 3 1 2 2 2 4 6% 67%	2280
	11th to 20th	Day	13% 5% 2 6% 4 4 4 4 5% 6% 47%	2280
	21st to end	Day	16% 5% 2 5% 3 3 4 3 4 6% 48%	1996
October	1st to 10th	Day	19% 7% 1 4 3 3 4 3 6% 5% 44%	1900
	11th to 20th	Day	22% 8% 3 7% 4 4 4 3 4 6% 37%	1900
	21st to end	Day	27% 8% 2 7% 4 4 3 3 5% 5% 31%	2063
November	1st to 10th	Day	35% 10% 3 7% 4 3 3 3 5% 5% 22%	1598
	11th to 20th	Day	35% 9% 2 7% 4 4 4 4 5% 6% 20%	1520
	21st to end	Day	31% 10% 3 7% 4 4 4 3 4 5% 24%	1520
December	1st to 10th	Day	28% 11% 3 8% 5% 3 3 3 5% 5% 27%	1520
	11th to 20th	Day	34% 11% 3 6% 5% 4 5% 6% 7% 7% 11%	1928
	21st to end	Day	34% 15% 4 9% 4 4 5% 4 5% 5% 11%	2794
January	1st to 10th	Night	38% 16% 4 9% 5% 4 4 3 3 3 10%	4406
	11th to 20th	Night	41% 14% 3 8% 4 3 3 2 3 4 17%	4420
	21st to end	Night	38% 16% 3 7% 4 3 3 2 3 5% 15%	4552
February	1st to 10th	Night	31% 13% 3 8% 6% 4 3 3 4 5% 19%	2470
	11th to 20th	Night	33% 12% 2 6% 3 3 3 3 4 4 26%	2402
	21st to end	Night	32% 15% 3 7% 3 3 3 3 4 5% 21%	1958
March	1st to 10th	Night	20% 21% 4 9% 5% 4 4 3 5% 5% 20%	3561
	11th to 20th	Night	21% 11% 2 6% 3 3 2 3 4 5% 41%	3490
	21st to end	Night	27% 17% 4 10% 5% 5% 4 3 5% 4 15%	3750
April	1st to 10th	Night	30% 13% 3 8% 5% 4 3 2 5% 4 22%	1900
	11th to 20th	Night	25% 12% 3 6% 3 4 4 3 5% 7% 27%	1879
	21st to end	Night	25% 11% 3 6% 4 4 4 3 5% 5% 30%	1728
May	1st to 10th	Night	25% 11% 3 8% 3 3 3 2 3 4 34%	2645
	11th to 20th	Night	12% 6% 2 5% 3 3 3 2 5% 6% 53%	2516
	21st to end	Night	21% 7% 3 7% 4 4 4 4 5% 8% 33%	2762
June	1st to 10th	Night	20% 8% 3 7% 4 3 4 3 4 5% 38%	1520
	11th to 20th	Night	18% 8% 2 7% 4 4 4 3 5% 5% 39%	1520
	21st to end	Night	9% 5% 2 6% 3 2 3 3 3 4 60%	1520
July	1st to 10th	Night	4 2 1 2 2 1 2 1 2 2 81%	2540
	11th to 20th	Night	4 2 1 3 1 2 2 2 2 3 79%	2540
	21st to end	Night	5% 2 1 1 1 1 1 1 2 3 81%	2778
August	1st to 10th	Night	2 2 1 3 1 2 2 2 3 5% 77%	2848
	11th to 20th	Night	7% 3 2 5% 3 3 3 3 4 6% 61%	2812
	21st to end	Night	10% 4 2 4 2 2 2 2 3 5% 66%	3391
September	1st to 10th	Night	8% 3 1 3 2 2 2 2 4 5% 68%	1900
	11th to 20th	Night	12% 4 1 4 4 4 4 3 5% 5% 52%	1900
	21st to end	Night	13% 5% 1 5% 3 4 3 2 5% 7% 52%	2178
October	1st to 10th	Night	19% 6% 2 6% 4 3 3 2 4 5% 47%	2280
	11th to 20th	Night	20% 6% 2 6% 4 4 3 3 5% 6% 42%	2280
	21st to end	Night	27% 9% 3 6% 3 3 3 3 3 4 36%	2533
November	1st to 10th	Night	33% 10% 2 7% 5% 4 4 3 4 5% 24%	2498
	11th to 20th	Night	36% 8% 3 7% 4 4 4 3 4 4 22%	2660
	21st to end	Night	29% 9% 2 7% 4 3 4 4 4 5% 29%	2660
December	1st to 10th	Night	30% 9% 3 6% 5% 4 4 3 5% 5% 27%	2660
	11th to 20th	Night	32% 12% 3 7% 4 4 4 3 5% 7% 19%	3276
	21st to end	Night	30% 13% 3 9% 7% 6% 4 3 4 5% 15%	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	79% 9% 6% 4 1 1	2539
	11th to 20th	Day	73% 6% 7% 8% 3 3	2540
	21st to end	Day	69% 9% 8% 8% 5% 1	3096
February	1st to 10th	Day	66% 8% 11% 10% 5%	1710
	11th to 20th	Day	67% 9% 9% 8% 4 2	1674
	21st to end	Day	69% 7% 8% 9% 5% 2	1495
March	1st to 10th	Day	63% 9% 12% 14% 3	3310
	11th to 20th	Day	49% 7% 10% 24% 10% 1	3490
	21st to end	Day	68% 10% 11% 7% 4	3903
April	1st to 10th	Day	70% 7% 10% 10% 4	2280
	11th to 20th	Day	61% 8% 10% 11% 7% 2	2252
	21st to end	Day	58% 7% 13% 12% 7% 2	2449
May	1st to 10th	Day	51% 10% 12% 17% 11%	4317
	11th to 20th	Day	32% 6% 18% 31% 12% 1	4380
	21st to end	Day	50% 13% 20% 15% 2	4814
June	1st to 10th	Day	52% 6% 16% 20% 6%	2660
	11th to 20th	Day	50% 8% 18% 17% 6%	2660
	21st to end	Day	30% 5% 16% 32% 12% 4	2660
July	1st to 10th	Day	13% 4 9% 18% 24% 33%	4351
	11th to 20th	Day	13% 3 6% 17% 36% 25%	4345
	21st to end	Day	12% 3 9% 27% 39% 10%	4621
August	1st to 10th	Day	15% 4 9% 30% 30% 12%	4076
	11th to 20th	Day	21% 6% 17% 35% 17% 4	4065
	21st to end	Day	25% 6% 13% 25% 24% 9%	4282
September	1st to 10th	Day	19% 3 13% 30% 23% 13%	2280
	11th to 20th	Day	36% 8% 12% 22% 15% 7%	2280
	21st to end	Day	37% 6% 13% 21% 16% 6%	1996
October	1st to 10th	Day	40% 7% 11% 19% 17% 5%	1900
	11th to 20th	Day	50% 8% 12% 14% 14% 2	1900
	21st to end	Day	55% 9% 9% 13% 13% 2	2063
November	1st to 10th	Day	65% 8% 10% 12% 5%	1598
	11th to 20th	Day	65% 8% 10% 8% 6% 3	1520
	21st to end	Day	62% 8% 9% 7% 13% 1	1520
December	1st to 10th	Day	60% 8% 10% 9% 11% 2	1520
	11th to 20th	Day	69% 11% 8% 9% 2	1928
	21st to end	Day	72% 12% 9% 5% 2	2794
January	1st to 10th	Night	78% 8% 6% 4 3 1	4406
	11th to 20th	Night	74% 6% 5% 10% 3 2	4420
	21st to end	Night	73% 5% 6% 8% 6% 1	4552
February	1st to 10th	Night	68% 6% 11% 9% 5% 2	2470
	11th to 20th	Night	62% 7% 12% 10% 6% 2	2404
	21st to end	Night	65% 6% 10% 11% 6% 2	1958
March	1st to 10th	Night	63% 9% 12% 12% 4	3561
	11th to 20th	Night	45% 7% 14% 20% 13% 1	3490
	21st to end	Night	69% 9% 11% 9% 1	3750
April	1st to 10th	Night	65% 7% 12% 11% 5%	1900
	11th to 20th	Night	56% 8% 15% 11% 7% 3	1879
	21st to end	Night	56% 7% 15% 15% 6% 3	1728
May	1st to 10th	Night	51% 9% 11% 18% 10% 1	2645
	11th to 20th	Night	31% 6% 17% 35% 9% 2	2516
	21st to end	Night	45% 13% 27% 13% 3	2762
June	1st to 10th	Night	47% 8% 16% 24% 5%	1520
	11th to 20th	Night	45% 8% 19% 21% 7%	1520
	21st to end	Night	29% 5% 17% 32% 13% 4	1520
July	1st to 10th	Night	12% 3 8% 19% 25% 33%	2500
	11th to 20th	Night	14% 3 6% 18% 32% 28%	2492
	21st to end	Night	10% 2 11% 29% 37% 10%	2691
August	1st to 10th	Night	12% 3 10% 37% 27% 12%	2839
	11th to 20th	Night	23% 7% 19% 33% 14% 4	2839
	21st to end	Night	23% 5% 13% 29% 22% 8%	3391
September	1st to 10th	Night	20% 4 11% 30% 22% 12%	1900
	11th to 20th	Night	32% 6% 14% 24% 13% 10%	1900
	21st to end	Night	33% 6% 13% 24% 16% 9%	2178
October	1st to 10th	Night	40% 5% 8% 23% 19% 5%	2280
	11th to 20th	Night	43% 7% 12% 18% 16% 4	2280
	21st to end	Night	52% 7% 9% 13% 16% 3	2533
November	1st to 10th	Night	61% 8% 10% 12% 8% 1	2498
	11th to 20th	Night	64% 8% 9% 8% 9% 2	2660
	21st to end	Night	57% 8% 9% 11% 11% 4	2660
December	1st to 10th	Night	59% 7% 10% 12% 10% 2	2660
	11th to 20th	Night	67% 9% 10% 9% 5%	3276
	21st to end	Night	68% 14% 10% 6% 2 1	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	51% 5% 18% 16% 8% 1	180
	11th to 20th	Day	42% 7% 20% 18% 8% 4	180
	21st to end	Day	37% 7% 20% 20% 13% 3	383
February	1st to 10th	Day	40% 5% 23% 18% 12% 2	370
	11th to 20th	Day	38% 9% 25% 19% 7% 2	365
	21st to end	Day	39% 11% 19% 18% 11% 1	347
March	1st to 10th	Day	38% 8% 27% 17% 10%	460
	11th to 20th	Day	31% 9% 23% 22% 12% 3	460
	21st to end	Day	36% 11% 27% 17% 9% 1	506
April	1st to 10th	Day	36% 11% 22% 20% 9% 2	460
	11th to 20th	Day	31% 13% 24% 19% 10% 3	452
	21st to end	Day	33% 9% 27% 18% 12% 2	460
May	1st to 10th	Day	20% 13% 29% 24% 11% 3	463
	11th to 20th	Day	28% 6% 20% 26% 15% 5%	488
	21st to end	Day	21% 7% 23% 27% 18% 4	529
June	1st to 10th	Day	24% 6% 23% 32% 13% 1	490
	11th to 20th	Day	20% 8% 30% 29% 12% 1	490
	21st to end	Day	8% 6% 23% 41% 16% 5%	490
July	1st to 10th	Day	8% 5% 24% 37% 21% 5%	486
	11th to 20th	Day	4 7% 25% 39% 20% 5%	484
	21st to end	Day	4 3 19% 47% 22% 5%	531
August	1st to 10th	Day	4 2 20% 40% 28% 7%	487
	11th to 20th	Day	4 3 16% 45% 24% 8%	477
	21st to end	Day	6% 5% 27% 37% 20% 5%	539
September	1st to 10th	Day	8% 5% 25% 34% 22% 5%	490
	11th to 20th	Day	15% 7% 21% 32% 20% 5%	490
	21st to end	Day	18% 8% 24% 29% 16% 4	490
October	1st to 10th	Day	19% 7% 24% 25% 19% 6%	490
	11th to 20th	Day	24% 6% 18% 26% 22% 4	490
	21st to end	Day	31% 8% 25% 20% 11% 5%	512
November	1st to 10th	Day	36% 11% 22% 17% 12% 3	233
	11th to 20th	Day	37% 3 22% 18% 14% 6%	180
	21st to end	Day	36% 7% 22% 14% 16% 5%	180
December	1st to 10th	Day	39% 9% 17% 19% 11% 6%	180
	11th to 20th	Day	49% 8% 18% 15% 7% 3	180
	21st to end	Day	46% 6% 18% 16% 12% 2	198
January	1st to 10th	Night	43% 7% 15% 18% 14% 2	760
	11th to 20th	Night	41% 6% 13% 23% 15% 2	760
	21st to end	Night	35% 5% 13% 30% 15% 2	836
February	1st to 10th	Night	35% 6% 16% 26% 15% 2	760
	11th to 20th	Night	39% 5% 17% 24% 14% 1	744
	21st to end	Night	40% 8% 15% 26% 10%	628
March	1st to 10th	Night	35% 7% 18% 28% 12% 1	760
	11th to 20th	Night	30% 8% 19% 26% 16% 1	760
	21st to end	Night	36% 6% 21% 23% 12% 1	836
April	1st to 10th	Night	34% 5% 19% 25% 16% 1	760
	11th to 20th	Night	30% 6% 21% 26% 16% 1	751
	21st to end	Night	28% 6% 22% 28% 16% 1	588
May	1st to 10th	Night	22% 4 28% 31% 14% 2	446
	11th to 20th	Night	21% 4 18% 34% 21% 2	374
	21st to end	Night	23% 3 19% 32% 20% 1	411
June	1st to 10th	Night	22% 4 22% 36% 16% 1	380
	11th to 20th	Night	22% 4 22% 40% 11% 1	380
	21st to end	Night	10% 2 26% 41% 21%	380
July	1st to 10th	Night	8% 2 17% 49% 24%	370
	11th to 20th	Night	5% 4 27% 45% 19% 1	368
	21st to end	Night	3 2 19% 50% 24% 1	421
August	1st to 10th	Night	4 2 14% 38% 37% 4	567
	11th to 20th	Night	5% 3 10% 44% 36% 2	564
	21st to end	Night	8% 3 21% 41% 24% 2	768
September	1st to 10th	Night	9% 3 19% 41% 26% 2	760
	11th to 20th	Night	13% 3 14% 33% 31% 6%	760
	21st to end	Night	15% 4 16% 37% 25% 3	760
October	1st to 10th	Night	19% 3 19% 34% 23% 3	760
	11th to 20th	Night	21% 4 14% 33% 24% 4	760
	21st to end	Night	31% 5% 19% 25% 15% 4	836
November	1st to 10th	Night	37% 6% 14% 28% 14% 1	744
	11th to 20th	Night	39% 6% 17% 23% 14% 1	760
	21st to end	Night	29% 7% 15% 29% 18% 2	760
December	1st to 10th	Night	34% 5% 13% 30% 15% 2	760
	11th to 20th	Night	43% 5% 14% 23% 15% 1	760
	21st to end	Night	45% 7% 17% 19% 10% 1	836

Page generated at 2024-10-29 22:22:54. Version ac07

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