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 2024-03-18.

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	22% 9% 3 6% 5% 3 4 4 5% 7% 33%	78698
	Night	25% 11% 3 6% 5% 3 4 4 4 6% 31%	81105
Transparency	Day	51% 8% 13% 17% 9% 2	78412
	Night	55% 7% 11% 15% 9% 3	80913
Seeing	Day	22% 9% 25% 29% 13% 2	14004
	Night	27% 6% 16% 26% 21% 3	23138

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% 17% 6% 8% 6% 2 3 4 3 5% 13%	2539
	11th to 20th	Day	40% 10% 4 6% 5% 2 3 3 2 4 21%	2746
	21st to end	Day	37% 12% 3 6% 6% 3 4 4 4 5% 17%	3146
February	1st to 10th	Day	29% 11% 5% 7% 6% 3 5% 4 5% 6% 19%	1710
	11th to 20th	Day	29% 11% 4 7% 5% 3 4 4 5% 5% 23%	1665
	21st to end	Day	31% 13% 4 7% 5% 3 4 3 3 5% 22%	1461
March	1st to 10th	Day	30% 13% 4 7% 5% 3 6% 5% 5% 6% 17%	2090
	11th to 20th	Day	29% 12% 4 7% 5% 3 4 4 4 6% 22%	2059
	21st to end	Day	31% 11% 5% 8% 7% 3 6% 5% 4 5% 15%	2178
April	1st to 10th	Day	30% 12% 5% 8% 7% 3 4 3 3 6% 19%	2132
	11th to 20th	Day	25% 12% 5% 7% 6% 3 4 4 5% 6% 23%	2159
	21st to end	Day	24% 7% 3 8% 5% 4 5% 5% 6% 8% 27%	2340
May	1st to 10th	Day	19% 9% 3 6% 5% 3 4 4 5% 7% 34%	2340
	11th to 20th	Day	22% 10% 3 6% 5% 3 4 4 5% 7% 28%	2461
	21st to end	Day	23% 10% 3 6% 5% 3 4 4 5% 9% 27%	2723
June	1st to 10th	Day	25% 8% 4 6% 4 3 4 5% 5% 7% 30%	2520
	11th to 20th	Day	16% 9% 3 6% 5% 3 5% 4 6% 8% 34%	2520
	21st to end	Day	12% 8% 3 4 4 3 3 3 4 7% 50%	2520
July	1st to 10th	Day	6% 7% 3 5% 4 2 3 3 5% 8% 54%	2520
	11th to 20th	Day	9% 6% 3 4 4 2 3 3 4 6% 55%	2520
	21st to end	Day	5% 6% 3 3 4 3 3 4 5% 8% 57%	2563
August	1st to 10th	Day	5% 9% 2 4 4 3 4 4 5% 9% 50%	2328
	11th to 20th	Day	5% 6% 2 4 3 2 3 4 5% 8% 58%	2298
	21st to end	Day	6% 6% 2 4 3 3 3 3 4 9% 56%	2480
September	1st to 10th	Day	5% 4 1 4 3 2 3 3 4 7% 63%	2160
	11th to 20th	Day	11% 7% 3 5% 5% 3 3 4 4 10% 46%	2064
	21st to end	Day	12% 5% 2 5% 5% 3 5% 4 5% 8% 47%	1952
October	1st to 10th	Day	16% 7% 4 5% 5% 3 4 4 5% 5% 43%	1800
	11th to 20th	Day	21% 6% 2 5% 4 3 4 4 5% 9% 38%	1800
	21st to end	Day	23% 9% 4 5% 4 3 3 4 5% 7% 33%	1980
November	1st to 10th	Day	31% 9% 3 7% 5% 4 4 4 5% 5% 22%	1642
	11th to 20th	Day	32% 9% 4 7% 5% 3 4 4 5% 6% 21%	1520
	21st to end	Day	27% 9% 4 6% 5% 2 3 4 4 7% 28%	1520
December	1st to 10th	Day	26% 9% 3 7% 5% 3 4 3 4 8% 28%	1520
	11th to 20th	Day	30% 13% 4 6% 6% 3 4 5% 4 6% 19%	1928
	21st to end	Day	36% 15% 4 7% 4 3 4 4 4 5% 14%	2794
January	1st to 10th	Night	38% 15% 4 7% 6% 3 4 4 3 3 12%	4406
	11th to 20th	Night	40% 13% 3 5% 4 2 3 3 3 3 20%	4203
	21st to end	Night	45% 11% 4 5% 4 2 3 3 3 5% 16%	4521
February	1st to 10th	Night	28% 11% 4 7% 6% 3 5% 5% 4 6% 21%	2470
	11th to 20th	Night	29% 12% 3 7% 5% 3 4 3 4 5% 26%	2402
	21st to end	Night	31% 12% 4 6% 5% 3 4 4 5% 5% 22%	1990
March	1st to 10th	Night	30% 11% 4 7% 5% 3 3 4 4 5% 22%	2090
	11th to 20th	Night	26% 12% 3 7% 5% 3 4 3 4 5% 26%	2067
	21st to end	Night	34% 12% 3 7% 5% 3 4 4 4 5% 19%	2178
April	1st to 10th	Night	31% 12% 4 6% 5% 3 4 4 4 5% 23%	1827
	11th to 20th	Night	24% 14% 4 7% 5% 2 3 4 4 6% 28%	1744
	21st to end	Night	25% 10% 4 7% 5% 2 5% 4 5% 6% 27%	1620
May	1st to 10th	Night	19% 10% 3 5% 5% 2 3 4 4 7% 37%	1620
	11th to 20th	Night	19% 11% 4 8% 5% 3 5% 5% 5% 7% 28%	1430
	21st to end	Night	22% 10% 3 6% 5% 3 4 5% 5% 7% 30%	1552
June	1st to 10th	Night	21% 9% 5% 5% 5% 3 4 4 5% 7% 34%	1440
	11th to 20th	Night	14% 9% 3 5% 4 2 4 4 5% 8% 41%	1440
	21st to end	Night	12% 10% 3 4 4 2 3 3 4 6% 49%	1440
July	1st to 10th	Night	7% 11% 2 4 4 3 4 3 4 7% 52%	1440
	11th to 20th	Night	8% 9% 3 4 4 2 3 4 4 7% 52%	1440
	21st to end	Night	5% 11% 3 4 4 2 4 3 5% 7% 51%	1750
August	1st to 10th	Night	6% 14% 3 4 3 2 4 4 5% 8% 47%	1611
	11th to 20th	Night	5% 9% 2 5% 4 2 2 4 4 6% 56%	1602
	21st to end	Night	7% 8% 2 4 4 2 3 4 5% 6% 55%	1876
September	1st to 10th	Night	8% 6% 2 3 3 2 3 3 5% 6% 61%	1800
	11th to 20th	Night	9% 7% 3 6% 4 3 4 3 4 6% 51%	1894
	21st to end	Night	15% 6% 3 4 5% 2 4 4 4 7% 47%	2006
October	1st to 10th	Night	14% 8% 3 6% 5% 2 4 3 4 6% 45%	2160
	11th to 20th	Night	18% 7% 2 6% 5% 3 3 4 5% 6% 41%	2160
	21st to end	Night	23% 9% 3 7% 5% 2 4 4 3 5% 35%	2376
November	1st to 10th	Night	30% 9% 3 6% 5% 3 4 4 5% 7% 25%	2432
	11th to 20th	Night	32% 9% 3 7% 5% 3 4 4 4 5% 24%	2660
	21st to end	Night	24% 8% 3 7% 5% 3 5% 4 4 6% 31%	2660
December	1st to 10th	Night	26% 10% 4 6% 5% 3 4 4 5% 5% 29%	2660
	11th to 20th	Night	32% 11% 4 6% 5% 3 4 4 4 7% 20%	3276
	21st to end	Night	31% 13% 4 7% 5% 3 3 3 4 4 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	65% 10% 9% 12% 4	2090
	11th to 20th	Day	62% 9% 9% 14% 6% 1	2059
	21st to end	Day	69% 11% 8% 11% 1	2178
April	1st to 10th	Day	66% 10% 9% 11% 4	2132
	11th to 20th	Day	60% 10% 10% 12% 6% 2	2162
	21st to end	Day	54% 11% 12% 16% 5% 1	2340
May	1st to 10th	Day	48% 9% 18% 17% 7% 1	2340
	11th to 20th	Day	53% 9% 17% 14% 5% 2	2464
	21st to end	Day	53% 12% 17% 15% 3	2724
June	1st to 10th	Day	53% 8% 14% 21% 3	2520
	11th to 20th	Day	45% 12% 20% 19% 4	2520
	21st to end	Day	34% 8% 19% 27% 10% 2	2520
July	1st to 10th	Day	28% 8% 18% 24% 18% 3	2451
	11th to 20th	Day	29% 5% 16% 25% 19% 7%	2445
	21st to end	Day	25% 4 16% 31% 20% 3	2421
August	1st to 10th	Day	32% 10% 19% 27% 10% 3	2312
	11th to 20th	Day	25% 7% 21% 28% 16% 3	2298
	21st to end	Day	27% 7% 20% 26% 18% 3	2480
September	1st to 10th	Day	22% 6% 15% 31% 18% 9%	2160
	11th to 20th	Day	37% 8% 16% 22% 12% 5%	2064
	21st to end	Day	34% 9% 15% 22% 15% 5%	1952
October	1st to 10th	Day	42% 8% 13% 18% 15% 4	1800
	11th to 20th	Day	43% 9% 14% 17% 16% 2	1800
	21st to end	Day	51% 7% 10% 14% 12% 6%	1980
November	1st to 10th	Day	62% 9% 9% 12% 7% 1	1642
	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	63% 7% 10% 14% 6%	2090
	11th to 20th	Night	61% 8% 10% 14% 7% 1	2067
	21st to end	Night	68% 9% 10% 11% 3	2178
April	1st to 10th	Night	65% 6% 13% 12% 4	1827
	11th to 20th	Night	59% 8% 12% 14% 4 3	1744
	21st to end	Night	58% 7% 12% 15% 6% 1	1620
May	1st to 10th	Night	48% 8% 15% 19% 7% 2	1620
	11th to 20th	Night	55% 7% 16% 13% 6% 3	1430
	21st to end	Night	55% 8% 19% 15% 2	1552
June	1st to 10th	Night	52% 6% 17% 23% 2	1440
	11th to 20th	Night	41% 9% 22% 23% 5%	1440
	21st to end	Night	36% 6% 19% 28% 8% 3	1440
July	1st to 10th	Night	35% 5% 14% 25% 16% 5%	1400
	11th to 20th	Night	35% 4 9% 24% 23% 5%	1392
	21st to end	Night	33% 4 10% 27% 22% 4	1653
August	1st to 10th	Night	38% 6% 15% 27% 12% 3	1602
	11th to 20th	Night	30% 5% 13% 28% 18% 5%	1602
	21st to end	Night	30% 6% 12% 30% 18% 5%	1876
September	1st to 10th	Night	26% 5% 12% 27% 20% 11%	1800
	11th to 20th	Night	35% 7% 14% 24% 15% 4	1894
	21st to end	Night	38% 7% 13% 19% 16% 7%	2006
October	1st to 10th	Night	41% 6% 11% 19% 16% 6%	2160
	11th to 20th	Night	43% 8% 13% 17% 16% 3	2160
	21st to end	Night	52% 7% 10% 12% 12% 7%	2376
November	1st to 10th	Night	59% 7% 12% 12% 9% 1	2432
	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	31% 8% 24% 24% 11% 1	449
	21st to end	Day	30% 14% 26% 23% 7% 1	462
April	1st to 10th	Day	34% 14% 23% 21% 8% 1	420
	11th to 20th	Day	29% 17% 24% 21% 7% 3	412
	21st to end	Day	25% 11% 27% 26% 8% 2	420
May	1st to 10th	Day	17% 12% 33% 26% 9% 2	423
	11th to 20th	Day	28% 9% 27% 23% 11% 2	448
	21st to end	Day	20% 11% 27% 29% 11% 1	485
June	1st to 10th	Day	23% 6% 28% 30% 11% 2	450
	11th to 20th	Day	18% 6% 41% 26% 8% 1	450
	21st to end	Day	11% 4 27% 44% 13% 1	450
July	1st to 10th	Day	9% 3 31% 41% 15% 2	446
	11th to 20th	Day	7% 5% 30% 40% 17% 2	444
	21st to end	Day	5% 3 27% 45% 17% 2	487
August	1st to 10th	Day	8% 4 22% 40% 23% 4	447
	11th to 20th	Day	4 3 18% 45% 25% 4	437
	21st to end	Day	7% 4 26% 42% 16% 4	495
September	1st to 10th	Day	6% 4 28% 36% 24% 3	450
	11th to 20th	Day	14% 5% 25% 32% 20% 4	450
	21st to end	Day	15% 7% 23% 38% 14% 3	450
October	1st to 10th	Day	18% 6% 25% 30% 18% 3	450
	11th to 20th	Day	19% 8% 20% 30% 19% 5%	450
	21st to end	Day	26% 11% 23% 27% 10% 4	495
November	1st to 10th	Day	29% 12% 25% 22% 11% 2	302
	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% 15% 2	752
	21st to end	Night	37% 8% 18% 24% 12% 1	792
April	1st to 10th	Night	36% 7% 18% 20% 17% 3	720
	11th to 20th	Night	30% 8% 20% 25% 14% 3	676
	21st to end	Night	30% 6% 15% 26% 19% 2	540
May	1st to 10th	Night	24% 7% 19% 28% 20% 2	540
	11th to 20th	Night	25% 4 14% 29% 24% 4	368
	21st to end	Night	27% 6% 16% 25% 23% 2	389
June	1st to 10th	Night	23% 3 15% 36% 20% 3	360
	11th to 20th	Night	17% 4 20% 36% 19% 4	360
	21st to end	Night	19% 1 16% 31% 31% 2	360
July	1st to 10th	Night	13% 2 15% 32% 36% 3	350
	11th to 20th	Night	15% 3 15% 40% 25% 3	348
	21st to end	Night	14% 1 11% 35% 34% 4	568
August	1st to 10th	Night	18% 1 10% 30% 34% 7%	537
	11th to 20th	Night	12% 1 10% 25% 43% 10%	534
	21st to end	Night	12% 2 16% 32% 33% 6%	688
September	1st to 10th	Night	11% 1 14% 33% 38% 3	720
	11th to 20th	Night	12% 3 13% 28% 33% 11%	720
	21st to end	Night	17% 4 14% 32% 28% 5%	720
October	1st to 10th	Night	18% 4 19% 28% 28% 4	720
	11th to 20th	Night	20% 5% 13% 32% 25% 6%	720
	21st to end	Night	27% 7% 20% 24% 17% 4	792
November	1st to 10th	Night	33% 7% 17% 25% 16% 1	740
	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 2024-03-15 11:01:46. Version ac07

Copyright © 2024 Attilla Danko.