Coos Bay
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Coos Bay clear sky chart from 2005-11-06 to 2024-11-03.

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	19% 10% 3 6% 4 4 4 3 5% 7% 37%	101434
	Night	23% 13% 3 7% 4 3 3 3 4 5% 32%	97730
Transparency	Day	46% 8% 14% 17% 10% 4	101188
	Night	54% 7% 11% 15% 9% 4	97566
Seeing	Day	21% 9% 25% 29% 13% 2	14924
	Night	27% 6% 16% 27% 21% 3	23853

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	34% 18% 5% 9% 5% 3 3 3 3 5% 13%	2539
	11th to 20th	Day	39% 11% 4 7% 4 3 3 2 3 4 21%	2746
	21st to end	Day	37% 12% 3 7% 5% 4 4 3 4 5% 16%	3146
February	1st to 10th	Day	29% 12% 4 8% 6% 4 4 4 5% 5% 19%	1710
	11th to 20th	Day	28% 12% 4 8% 4 4 4 3 5% 5% 23%	1665
	21st to end	Day	30% 15% 3 8% 5% 4 4 2 3 5% 21%	1461
March	1st to 10th	Day	22% 19% 4 7% 4 4 5% 4 4 5% 22%	3442
	11th to 20th	Day	21% 11% 4 8% 4 3 3 3 4 5% 34%	3490
	21st to end	Day	29% 14% 3 10% 6% 5% 6% 4 4 5% 14%	3825
April	1st to 10th	Day	29% 14% 4 9% 6% 4 3 3 4 5% 19%	2251
	11th to 20th	Day	24% 13% 4 8% 5% 4 4 3 5% 5% 23%	2281
	21st to end	Day	25% 7% 3 8% 4 5% 5% 4 6% 7% 26%	2470
May	1st to 10th	Day	20% 9% 2 7% 5% 3 4 3 5% 6% 35%	4110
	11th to 20th	Day	12% 7% 2 5% 3 3 3 3 5% 7% 49%	4361
	21st to end	Day	15% 8% 2 6% 4 4 4 4 7% 10% 35%	4813
June	1st to 10th	Day	24% 9% 3 6% 4 4 3 4 6% 7% 30%	2660
	11th to 20th	Day	16% 10% 2 7% 5% 4 4 3 6% 8% 35%	2660
	21st to end	Day	11% 8% 3 5% 3 4 3 3 5% 7% 50%	2660
July	1st to 10th	Day	4 5% 2 4 2 2 2 2 4 6% 69%	4420
	11th to 20th	Day	6% 7% 2 4 3 3 3 3 4 7% 58%	4420
	21st to end	Day	6% 9% 3 4 3 3 3 3 5% 7% 55%	4485
August	1st to 10th	Day	4 12% 3 7% 4 4 4 3 5% 9% 44%	4091
	11th to 20th	Day	6% 8% 2 5% 3 3 4 3 7% 9% 50%	4026
	21st to end	Day	6% 6% 2 5% 3 3 3 2 4 8% 57%	4349
September	1st to 10th	Day	5% 5% 1 4 3 2 3 2 5% 7% 62%	2280
	11th to 20th	Day	11% 7% 2 7% 3 4 3 3 4 10% 46%	2178
	21st to end	Day	12% 5% 2 5% 4 4 4 2 5% 8% 48%	2060
October	1st to 10th	Day	16% 7% 3 5% 4 4 4 3 5% 5% 44%	1900
	11th to 20th	Day	20% 6% 1 6% 4 4 3 4 6% 8% 36%	1900
	21st to end	Day	23% 10% 3 6% 4 4 4 3 5% 7% 32%	2090
November	1st to 10th	Day	31% 9% 3 8% 4 5% 3 4 5% 6% 21%	1663
	11th to 20th	Day	32% 9% 4 8% 4 4 4 3 5% 6% 21%	1520
	21st to end	Day	27% 10% 3 7% 4 3 3 3 4 7% 28%	1520
December	1st to 10th	Day	25% 9% 3 8% 5% 4 3 3 5% 7% 28%	1520
	11th to 20th	Day	30% 14% 4 7% 5% 4 4 4 5% 5% 19%	1928
	21st to end	Day	36% 15% 3 8% 4 4 4 3 4 5% 14%	2794
January	1st to 10th	Night	38% 16% 4 8% 5% 4 4 3 3 3 12%	4406
	11th to 20th	Night	39% 14% 3 6% 3 3 3 2 3 3 20%	4203
	21st to end	Night	45% 11% 3 6% 3 3 2 2 3 5% 16%	4521
February	1st to 10th	Night	28% 11% 4 7% 5% 4 4 4 5% 6% 21%	2470
	11th to 20th	Night	28% 13% 3 8% 4 4 3 2 4 5% 25%	2402
	21st to end	Night	30% 13% 4 8% 4 4 4 3 5% 5% 22%	1990
March	1st to 10th	Night	24% 19% 4 8% 4 4 3 3 4 5% 22%	3432
	11th to 20th	Night	18% 14% 4 8% 4 3 3 2 3 4 36%	3490
	21st to end	Night	30% 16% 3 8% 5% 4 4 3 4 5% 17%	3828
April	1st to 10th	Night	30% 13% 3 7% 4 4 3 3 4 5% 23%	1928
	11th to 20th	Night	23% 14% 4 8% 4 3 3 3 4 6% 28%	1842
	21st to end	Night	25% 11% 4 7% 5% 4 4 4 5% 6% 26%	1710
May	1st to 10th	Night	23% 10% 3 6% 4 3 3 2 3 5% 38%	2860
	11th to 20th	Night	11% 10% 3 8% 4 4 3 4 4 6% 42%	2530
	21st to end	Night	20% 11% 2 5% 4 3 3 3 4 7% 37%	2762
June	1st to 10th	Night	21% 10% 3 5% 5% 4 4 3 5% 7% 33%	1520
	11th to 20th	Night	13% 9% 3 5% 4 3 4 3 6% 8% 42%	1520
	21st to end	Night	12% 11% 2 5% 3 3 3 3 4 6% 48%	1520
July	1st to 10th	Night	4 9% 1 3 2 2 3 2 3 5% 66%	2540
	11th to 20th	Night	5% 15% 3 5% 4 3 3 3 3 6% 51%	2540
	21st to end	Night	9% 20% 3 4 3 3 3 2 4 6% 44%	3072
August	1st to 10th	Night	5% 32% 4 6% 3 3 3 3 4 6% 31%	2848
	11th to 20th	Night	10% 18% 3 6% 3 3 3 3 5% 6% 41%	2812
	21st to end	Night	7% 8% 2 4 3 3 2 3 4 5% 58%	3324
September	1st to 10th	Night	8% 7% 2 4 2 2 3 2 4 6% 59%	1900
	11th to 20th	Night	10% 8% 2 7% 4 4 3 3 5% 6% 50%	2000
	21st to end	Night	14% 6% 2 5% 4 3 3 3 4 7% 48%	2118
October	1st to 10th	Night	13% 8% 3 7% 4 3 3 3 4 6% 46%	2280
	11th to 20th	Night	17% 9% 3 7% 4 3 3 3 5% 6% 39%	2280
	21st to end	Night	23% 9% 3 8% 4 3 4 3 4 5% 34%	2508
November	1st to 10th	Night	30% 9% 3 6% 4 4 4 3 5% 7% 25%	2456
	11th to 20th	Night	32% 10% 2 8% 5% 4 4 3 4 5% 24%	2660
	21st to end	Night	23% 9% 3 8% 5% 4 4 3 5% 6% 30%	2660
December	1st to 10th	Night	25% 11% 3 7% 4 4 4 3 5% 5% 28%	2660
	11th to 20th	Night	31% 11% 4 7% 4 4 4 3 4 7% 20%	3276
	21st to end	Night	31% 13% 4 8% 5% 4 3 3 4 5% 21%	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	71% 9% 10% 6% 3 1	2539
	11th to 20th	Day	69% 6% 6% 11% 5% 4	2746
	21st to end	Day	68% 9% 7% 8% 6% 2	3146
February	1st to 10th	Day	65% 8% 10% 12% 4 2	1710
	11th to 20th	Day	62% 9% 12% 11% 4 2	1674
	21st to end	Day	65% 8% 9% 11% 5% 2	1461
March	1st to 10th	Day	58% 11% 12% 15% 3	3442
	11th to 20th	Day	50% 10% 8% 18% 12% 2	3490
	21st to end	Day	68% 12% 8% 9% 3	3825
April	1st to 10th	Day	65% 10% 10% 10% 4	2251
	11th to 20th	Day	60% 10% 10% 12% 6% 2	2284
	21st to end	Day	54% 11% 13% 16% 5% 1	2470
May	1st to 10th	Day	45% 11% 15% 16% 10% 2	4110
	11th to 20th	Day	33% 6% 21% 26% 12% 1	4364
	21st to end	Day	41% 14% 30% 14% 1	4814
June	1st to 10th	Day	52% 8% 14% 21% 4	2660
	11th to 20th	Day	44% 12% 19% 20% 5%	2660
	21st to end	Day	34% 8% 19% 27% 10% 2	2660
July	1st to 10th	Day	18% 5% 12% 15% 22% 27%	4351
	11th to 20th	Day	25% 5% 13% 18% 26% 13%	4345
	21st to end	Day	28% 4 16% 26% 20% 5%	4344
August	1st to 10th	Day	38% 8% 16% 19% 13% 6%	4076
	11th to 20th	Day	29% 8% 24% 28% 10% 2	4065
	21st to end	Day	25% 7% 20% 24% 21% 2	4348
September	1st to 10th	Day	22% 6% 15% 31% 17% 9%	2280
	11th to 20th	Day	36% 8% 18% 21% 12% 5%	2178
	21st to end	Day	33% 8% 16% 23% 14% 5%	2060
October	1st to 10th	Day	41% 8% 12% 18% 16% 5%	1900
	11th to 20th	Day	44% 9% 14% 16% 15% 2	1900
	21st to end	Day	51% 7% 10% 15% 11% 5%	2090
November	1st to 10th	Day	62% 9% 9% 12% 7% 1	1663
	11th to 20th	Day	63% 7% 11% 8% 7% 4	1520
	21st to end	Day	57% 6% 11% 9% 10% 8%	1520
December	1st to 10th	Day	56% 7% 11% 13% 11% 2	1520
	11th to 20th	Day	66% 8% 11% 9% 5% 1	1928
	21st to end	Day	72% 8% 7% 9% 2 2	2794
January	1st to 10th	Night	75% 8% 7% 6% 3 2	4406
	11th to 20th	Night	69% 6% 6% 10% 5% 4	4203
	21st to end	Night	72% 5% 6% 7% 7% 2	4521
February	1st to 10th	Night	63% 9% 11% 11% 5% 1	2470
	11th to 20th	Night	62% 8% 10% 13% 5% 2	2404
	21st to end	Night	64% 9% 9% 10% 6% 2	1990
March	1st to 10th	Night	62% 9% 11% 14% 3	3432
	11th to 20th	Night	51% 9% 11% 15% 11% 3	3490
	21st to end	Night	68% 10% 12% 9% 1	3828
April	1st to 10th	Night	64% 6% 14% 12% 4	1928
	11th to 20th	Night	58% 8% 12% 14% 4 3	1842
	21st to end	Night	58% 8% 12% 15% 6% 1	1710
May	1st to 10th	Night	46% 11% 13% 20% 10% 1	2860
	11th to 20th	Night	40% 6% 19% 22% 9% 3	2530
	21st to end	Night	46% 11% 28% 13% 1	2762
June	1st to 10th	Night	52% 6% 17% 23% 2	1520
	11th to 20th	Night	40% 9% 22% 24% 6%	1520
	21st to end	Night	37% 6% 18% 28% 8% 3	1520
July	1st to 10th	Night	24% 3 8% 14% 21% 29%	2500
	11th to 20th	Night	38% 4 7% 15% 25% 12%	2492
	21st to end	Night	43% 4 9% 20% 22% 4	2976
August	1st to 10th	Night	56% 6% 9% 17% 9% 2	2839
	11th to 20th	Night	44% 6% 15% 21% 10% 3	2839
	21st to end	Night	28% 6% 11% 30% 21% 3	3324
September	1st to 10th	Night	27% 5% 12% 26% 20% 10%	1900
	11th to 20th	Night	36% 7% 15% 24% 15% 4	2000
	21st to end	Night	37% 7% 13% 21% 16% 7%	2118
October	1st to 10th	Night	41% 6% 11% 20% 17% 6%	2280
	11th to 20th	Night	45% 8% 13% 16% 15% 3	2280
	21st to end	Night	53% 7% 10% 12% 12% 6%	2508
November	1st to 10th	Night	59% 7% 12% 12% 9% 1	2456
	11th to 20th	Night	63% 6% 9% 12% 6% 4	2660
	21st to end	Night	54% 8% 9% 11% 10% 8%	2660
December	1st to 10th	Night	57% 7% 9% 14% 12% 2	2660
	11th to 20th	Night	65% 6% 11% 10% 7% 1	3276
	21st to end	Night	66% 7% 9% 12% 3 2	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	43% 15% 15% 17% 7% 3	180
	11th to 20th	Day	40% 10% 15% 18% 13% 4	308
	21st to end	Day	31% 12% 21% 18% 14% 4	407
February	1st to 10th	Day	28% 11% 24% 26% 9% 1	370
	11th to 20th	Day	33% 13% 21% 27% 6% 1	365
	21st to end	Day	32% 15% 23% 24% 5% 1	324
March	1st to 10th	Day	34% 14% 22% 21% 8%	460
	11th to 20th	Day	30% 8% 24% 24% 12% 2	460
	21st to end	Day	30% 15% 26% 22% 6% 1	506
April	1st to 10th	Day	32% 14% 23% 22% 8% 2	460
	11th to 20th	Day	28% 17% 25% 21% 7% 2	452
	21st to end	Day	25% 13% 27% 25% 8% 2	460
May	1st to 10th	Day	17% 13% 33% 26% 9% 2	463
	11th to 20th	Day	26% 8% 29% 24% 11% 2	488
	21st to end	Day	19% 11% 27% 30% 12% 1	529
June	1st to 10th	Day	22% 7% 28% 31% 11% 2	490
	11th to 20th	Day	17% 7% 42% 26% 8% 1	490
	21st to end	Day	10% 5% 28% 43% 13% 1	490
July	1st to 10th	Day	8% 3 32% 41% 14% 2	486
	11th to 20th	Day	6% 5% 31% 40% 16% 2	484
	21st to end	Day	6% 4 27% 44% 17% 2	531
August	1st to 10th	Day	8% 5% 24% 38% 21% 4	487
	11th to 20th	Day	5% 4 19% 44% 24% 4	477
	21st to end	Day	8% 4 26% 41% 16% 5%	539
September	1st to 10th	Day	6% 4 27% 37% 24% 3	490
	11th to 20th	Day	15% 5% 27% 31% 19% 3	490
	21st to end	Day	14% 7% 24% 37% 14% 3	490
October	1st to 10th	Day	18% 6% 25% 30% 17% 4	490
	11th to 20th	Day	19% 8% 20% 30% 18% 5%	490
	21st to end	Day	26% 12% 23% 27% 9% 4	539
November	1st to 10th	Day	30% 12% 24% 22% 10% 2	311
	11th to 20th	Day	32% 9% 23% 18% 14% 4	180
	21st to end	Day	28% 14% 19% 19% 18% 2	180
December	1st to 10th	Day	35% 9% 16% 19% 14% 7%	180
	11th to 20th	Day	41% 13% 16% 20% 9% 1	180
	21st to end	Day	39% 11% 16% 23% 10% 2	198
January	1st to 10th	Night	43% 10% 15% 17% 12% 3	760
	11th to 20th	Night	38% 8% 15% 21% 14% 5%	760
	21st to end	Night	32% 6% 15% 26% 17% 4	836
February	1st to 10th	Night	34% 7% 16% 23% 18% 2	760
	11th to 20th	Night	34% 8% 18% 24% 14% 2	744
	21st to end	Night	33% 12% 17% 24% 13%	628
March	1st to 10th	Night	34% 12% 17% 23% 13% 1	760
	11th to 20th	Night	28% 10% 18% 28% 14% 3	760
	21st to end	Night	36% 9% 18% 24% 11% 1	836
April	1st to 10th	Night	35% 7% 18% 21% 17% 3	760
	11th to 20th	Night	29% 8% 21% 25% 14% 3	714
	21st to end	Night	30% 7% 16% 26% 19% 2	570
May	1st to 10th	Night	24% 7% 19% 28% 19% 2	570
	11th to 20th	Night	24% 5% 16% 28% 23% 4	388
	21st to end	Night	26% 6% 16% 27% 24% 2	411
June	1st to 10th	Night	23% 3 16% 36% 20% 3	380
	11th to 20th	Night	17% 4 22% 36% 18% 3	380
	21st to end	Night	19% 2 15% 32% 30% 2	380
July	1st to 10th	Night	12% 2 15% 32% 35% 3	370
	11th to 20th	Night	14% 3 15% 41% 25% 2	368
	21st to end	Night	15% 2 12% 35% 33% 4	600
August	1st to 10th	Night	21% 1 10% 29% 32% 7%	567
	11th to 20th	Night	13% 1 10% 24% 43% 10%	564
	21st to end	Night	12% 2 16% 31% 33% 6%	727
September	1st to 10th	Night	11% 1 14% 32% 38% 4	760
	11th to 20th	Night	12% 3 14% 28% 32% 10%	760
	21st to end	Night	17% 4 15% 32% 28% 5%	760
October	1st to 10th	Night	18% 4 18% 28% 28% 5%	760
	11th to 20th	Night	20% 5% 13% 32% 26% 5%	760
	21st to end	Night	28% 7% 20% 25% 16% 4	836
November	1st to 10th	Night	33% 7% 17% 25% 16% 1	748
	11th to 20th	Night	35% 10% 16% 23% 14% 2	760
	21st to end	Night	24% 8% 20% 28% 17% 3	760
December	1st to 10th	Night	29% 9% 16% 27% 16% 4	760
	11th to 20th	Night	38% 8% 17% 20% 15% 2	760
	21st to end	Night	42% 10% 15% 22% 9% 1	836

Page generated at 2024-10-31 00:39:25. Version ac07

Copyright © 2024 Attilla Danko.