Bandon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bandon 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	16% 10% 3 7% 4 4 4 3 5% 7% 36%	101397
	Night	20% 14% 3 7% 4 4 4 3 4 6% 31%	97778
Transparency	Day	48% 3 14% 20% 12% 4	101152
	Night	56% 3 11% 17% 10% 4	97612
Seeing	Day	22% 11% 29% 26% 10% 2	14964
	Night	27% 6% 16% 28% 19% 3	23900

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	27% 18% 5% 10% 5% 4 4 2 4 5% 15%	2539
	11th to 20th	Day	38% 13% 3 6% 4 4 3 2 3 4 20%	2798
	21st to end	Day	32% 13% 3 8% 5% 4 4 3 5% 5% 18%	3146
February	1st to 10th	Day	26% 12% 4 7% 7% 4 5% 4 6% 5% 21%	1710
	11th to 20th	Day	24% 13% 4 9% 5% 5% 4 3 4 5% 24%	1665
	21st to end	Day	25% 14% 4 9% 5% 5% 4 3 4 5% 22%	1471
March	1st to 10th	Day	20% 17% 3 7% 4 5% 4 4 5% 7% 24%	3442
	11th to 20th	Day	18% 11% 4 8% 5% 4 4 3 5% 6% 33%	3490
	21st to end	Day	24% 14% 3 10% 6% 7% 5% 4 6% 6% 15%	3825
April	1st to 10th	Day	26% 14% 4 8% 6% 4 3 4 5% 6% 20%	2243
	11th to 20th	Day	21% 13% 3 8% 6% 3 4 3 6% 7% 25%	2285
	21st to end	Day	21% 8% 3 7% 5% 4 5% 5% 7% 8% 27%	2470
May	1st to 10th	Day	16% 9% 3 6% 4 5% 4 3 4 7% 38%	4110
	11th to 20th	Day	10% 10% 2 5% 3 3 3 3 5% 8% 48%	4314
	21st to end	Day	12% 9% 2 6% 4 4 5% 4 6% 10% 38%	4813
June	1st to 10th	Day	18% 11% 3 7% 6% 4 4 3 5% 8% 31%	2660
	11th to 20th	Day	13% 11% 3 7% 4 3 4 3 6% 9% 37%	2660
	21st to end	Day	9% 7% 2 5% 5% 3 3 4 6% 8% 48%	2660
July	1st to 10th	Day	3 6% 2 4 3 2 2 2 4 7% 65%	4420
	11th to 20th	Day	5% 8% 3 5% 4 4 3 3 6% 8% 52%	4398
	21st to end	Day	6% 11% 3 5% 3 3 3 4 5% 9% 48%	4455
August	1st to 10th	Day	5% 12% 4 8% 5% 4 5% 4 7% 10% 36%	4091
	11th to 20th	Day	7% 8% 3 6% 4 3 4 4 6% 10% 47%	4026
	21st to end	Day	6% 6% 2 6% 3 3 3 2 5% 9% 54%	4351
September	1st to 10th	Day	3 5% 2 5% 2 3 3 3 6% 9% 58%	2280
	11th to 20th	Day	10% 8% 3 6% 5% 3 4 3 6% 8% 44%	2165
	21st to end	Day	10% 5% 2 5% 3 3 4 3 6% 9% 49%	2066
October	1st to 10th	Day	13% 8% 2 7% 4 4 3 3 5% 7% 43%	1900
	11th to 20th	Day	16% 7% 3 6% 4 5% 5% 4 6% 8% 37%	1900
	21st to end	Day	20% 9% 3 8% 4 4 3 4 5% 7% 33%	2090
November	1st to 10th	Day	26% 12% 3 8% 4 4 5% 3 6% 6% 22%	1672
	11th to 20th	Day	24% 11% 5% 8% 6% 4 4 4 6% 7% 22%	1520
	21st to end	Day	23% 12% 3 7% 5% 4 3 3 5% 6% 29%	1520
December	1st to 10th	Day	21% 9% 4 9% 5% 5% 3 4 5% 6% 29%	1520
	11th to 20th	Day	27% 13% 4 8% 6% 4 5% 4 6% 5% 20%	1928
	21st to end	Day	32% 14% 5% 10% 6% 5% 4 3 4 4 14%	2794
January	1st to 10th	Night	33% 16% 4 9% 5% 5% 5% 3 4 4 13%	4406
	11th to 20th	Night	36% 15% 4 7% 4 3 3 2 3 4 19%	4168
	21st to end	Night	39% 13% 3 7% 4 3 3 3 4 4 17%	4521
February	1st to 10th	Night	24% 13% 4 7% 7% 4 4 4 6% 7% 20%	2470
	11th to 20th	Night	25% 13% 3 9% 5% 4 3 3 4 5% 25%	2402
	21st to end	Night	27% 14% 4 8% 6% 4 3 3 5% 5% 22%	1980
March	1st to 10th	Night	21% 19% 4 9% 5% 4 5% 3 4 6% 20%	3432
	11th to 20th	Night	15% 15% 5% 8% 5% 4 4 3 4 5% 33%	3490
	21st to end	Night	25% 18% 5% 9% 5% 4 4 3 4 5% 17%	3828
April	1st to 10th	Night	27% 13% 3 8% 5% 5% 3 3 5% 6% 23%	1935
	11th to 20th	Night	21% 14% 4 7% 4 4 4 4 4 6% 29%	1838
	21st to end	Night	23% 12% 4 6% 5% 5% 4 5% 6% 5% 25%	1710
May	1st to 10th	Night	19% 10% 3 7% 5% 4 4 2 4 5% 37%	2860
	11th to 20th	Night	10% 16% 5% 7% 4 2 3 2 4 6% 40%	2580
	21st to end	Night	18% 14% 2 6% 3 3 3 3 5% 7% 37%	2762
June	1st to 10th	Night	18% 12% 3 7% 4 3 5% 3 4 7% 32%	1520
	11th to 20th	Night	12% 10% 4 7% 4 3 3 3 6% 8% 40%	1520
	21st to end	Night	11% 11% 2 6% 4 3 2 3 5% 7% 45%	1520
July	1st to 10th	Night	5% 10% 1 3 2 2 2 2 4 5% 65%	2540
	11th to 20th	Night	5% 19% 4 7% 4 3 3 3 3 6% 44%	2559
	21st to end	Night	12% 22% 3 5% 3 2 3 2 3 5% 40%	3109
August	1st to 10th	Night	8% 35% 5% 7% 3 3 2 2 3 5% 27%	2848
	11th to 20th	Night	11% 18% 3 6% 3 3 3 3 4 7% 39%	2812
	21st to end	Night	8% 8% 2 6% 3 2 4 2 3 5% 57%	3321
September	1st to 10th	Night	5% 8% 2 5% 3 3 4 3 5% 6% 56%	1900
	11th to 20th	Night	8% 9% 2 6% 4 3 3 3 5% 7% 48%	2012
	21st to end	Night	12% 8% 3 6% 4 4 3 3 4 7% 46%	2113
October	1st to 10th	Night	12% 9% 3 7% 4 3 3 3 4 6% 45%	2280
	11th to 20th	Night	15% 10% 3 7% 4 4 4 3 5% 7% 39%	2280
	21st to end	Night	20% 10% 3 8% 5% 3 3 4 4 6% 34%	2508
November	1st to 10th	Night	25% 11% 4 8% 5% 4 4 4 5% 6% 25%	2436
	11th to 20th	Night	26% 11% 4 9% 5% 5% 4 4 4 5% 23%	2660
	21st to end	Night	19% 11% 3 8% 5% 5% 4 4 5% 6% 30%	2660
December	1st to 10th	Night	22% 11% 3 7% 5% 5% 4 3 5% 5% 29%	2660
	11th to 20th	Night	29% 12% 3 8% 4 5% 4 3 5% 7% 19%	3276
	21st to end	Night	28% 14% 4 10% 6% 5% 4 3 4 5% 18%	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	73% 2 12% 9% 3 1	2539
	11th to 20th	Day	71% 2 7% 11% 5% 5%	2798
	21st to end	Day	69% 2 10% 10% 7% 2	3146
February	1st to 10th	Day	64% 3 12% 15% 4 2	1710
	11th to 20th	Day	64% 3 13% 14% 4 2	1674
	21st to end	Day	66% 3 9% 14% 6% 1	1471
March	1st to 10th	Day	62% 2 14% 18% 4	3442
	11th to 20th	Day	53% 3 9% 21% 12% 2	3490
	21st to end	Day	71% 2 11% 13% 3	3825
April	1st to 10th	Day	66% 2 14% 13% 5%	2243
	11th to 20th	Day	60% 4 13% 14% 8% 1	2288
	21st to end	Day	54% 4 16% 19% 6% 1	2470
May	1st to 10th	Day	48% 2 18% 20% 10% 3	4110
	11th to 20th	Day	37% 2 18% 27% 15% 1	4317
	21st to end	Day	43% 4 32% 19% 1	4814
June	1st to 10th	Day	53% 3 14% 24% 5%	2660
	11th to 20th	Day	45% 3 20% 26% 6%	2660
	21st to end	Day	35% 3 17% 31% 12% 2	2660
July	1st to 10th	Day	20% 2 9% 16% 22% 31%	4351
	11th to 20th	Day	27% 2 9% 19% 29% 13%	4323
	21st to end	Day	31% 3 11% 25% 25% 5%	4315
August	1st to 10th	Day	37% 2 16% 24% 16% 5%	4076
	11th to 20th	Day	31% 5% 17% 33% 13% 2	4065
	21st to end	Day	27% 4 16% 27% 23% 2	4350
September	1st to 10th	Day	24% 2 9% 34% 22% 9%	2280
	11th to 20th	Day	36% 4 14% 27% 15% 4	2165
	21st to end	Day	32% 3 14% 29% 16% 5%	2066
October	1st to 10th	Day	41% 3 10% 23% 16% 7%	1900
	11th to 20th	Day	44% 4 14% 20% 15% 3	1900
	21st to end	Day	51% 3 10% 18% 12% 5%	2090
November	1st to 10th	Day	62% 4 9% 15% 9% 1	1672
	11th to 20th	Day	63% 2 12% 11% 8% 4	1520
	21st to end	Day	56% 3 12% 10% 12% 8%	1520
December	1st to 10th	Day	56% 3 12% 14% 12% 3	1520
	11th to 20th	Day	66% 2 14% 11% 5% 1	1928
	21st to end	Day	75% 2 6% 11% 4 2	2794
January	1st to 10th	Night	77% 2 8% 8% 3 2	4406
	11th to 20th	Night	72% 2 7% 10% 5% 5%	4168
	21st to end	Night	73% 2 7% 9% 8% 2	4521
February	1st to 10th	Night	63% 4 12% 13% 5% 2	2470
	11th to 20th	Night	62% 3 11% 17% 5% 2	2404
	21st to end	Night	66% 3 9% 13% 6% 2	1980
March	1st to 10th	Night	67% 2 10% 18% 4	3432
	11th to 20th	Night	56% 2 13% 16% 10% 3	3490
	21st to end	Night	72% 2 14% 11% 2	3828
April	1st to 10th	Night	63% 3 15% 14% 5%	1935
	11th to 20th	Night	58% 5% 13% 16% 6% 2	1838
	21st to end	Night	60% 3 13% 18% 6% 1	1710
May	1st to 10th	Night	52% 2 12% 23% 10% 2	2860
	11th to 20th	Night	48% 2 14% 23% 11% 3	2580
	21st to end	Night	49% 3 30% 17% 1	2762
June	1st to 10th	Night	53% 3 18% 24% 2	1520
	11th to 20th	Night	43% 4 19% 27% 6%	1520
	21st to end	Night	39% 2 17% 33% 8% 3	1520
July	1st to 10th	Night	24% 2 7% 16% 22% 29%	2500
	11th to 20th	Night	40% 2 8% 16% 25% 9%	2511
	21st to end	Night	46% 3 6% 20% 22% 3	3011
August	1st to 10th	Night	61% 2 9% 18% 9% 2	2839
	11th to 20th	Night	45% 5% 13% 24% 11% 2	2839
	21st to end	Night	29% 3 12% 31% 22% 3	3321
September	1st to 10th	Night	27% 3 9% 30% 21% 10%	1900
	11th to 20th	Night	35% 4 15% 26% 17% 3	2012
	21st to end	Night	38% 3 13% 22% 16% 7%	2113
October	1st to 10th	Night	41% 3 10% 21% 18% 7%	2280
	11th to 20th	Night	46% 3 15% 18% 15% 3	2280
	21st to end	Night	53% 2 11% 15% 12% 7%	2508
November	1st to 10th	Night	60% 3 11% 15% 9% 1	2436
	11th to 20th	Night	64% 3 9% 13% 7% 4	2660
	21st to end	Night	55% 3 11% 13% 11% 8%	2660
December	1st to 10th	Night	57% 3 9% 16% 13% 2	2660
	11th to 20th	Night	66% 2 11% 11% 8% 1	3276
	21st to end	Night	71% 2 8% 14% 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	39% 16% 19% 15% 6% 4	180
	11th to 20th	Day	40% 10% 17% 16% 11% 5%	334
	21st to end	Day	32% 11% 22% 19% 11% 4	407
February	1st to 10th	Day	32% 11% 25% 21% 10% 1	370
	11th to 20th	Day	38% 11% 28% 16% 4 2	365
	21st to end	Day	31% 16% 27% 21% 4 1	323
March	1st to 10th	Day	38% 12% 23% 20% 6%	460
	11th to 20th	Day	31% 10% 28% 20% 10% 2	460
	21st to end	Day	31% 19% 24% 20% 5% 1	506
April	1st to 10th	Day	32% 17% 24% 19% 7% 2	460
	11th to 20th	Day	29% 17% 29% 18% 5% 3	452
	21st to end	Day	24% 17% 32% 18% 7% 1	460
May	1st to 10th	Day	20% 17% 35% 20% 7% 1	463
	11th to 20th	Day	28% 10% 27% 25% 8% 1	488
	21st to end	Day	21% 12% 35% 26% 6% 1	529
June	1st to 10th	Day	18% 11% 35% 26% 9% 1	490
	11th to 20th	Day	17% 17% 41% 21% 4	490
	21st to end	Day	9% 9% 39% 36% 6% 1	490
July	1st to 10th	Day	9% 7% 42% 32% 10%	486
	11th to 20th	Day	6% 7% 44% 35% 8% 1	484
	21st to end	Day	9% 4 39% 38% 9% 1	531
August	1st to 10th	Day	10% 4 29% 39% 16% 3	487
	11th to 20th	Day	8% 4 30% 41% 14% 3	477
	21st to end	Day	10% 5% 35% 36% 10% 4	539
September	1st to 10th	Day	6% 4 32% 37% 18% 3	490
	11th to 20th	Day	17% 8% 26% 32% 15% 2	490
	21st to end	Day	14% 11% 29% 30% 12% 3	490
October	1st to 10th	Day	19% 10% 25% 29% 14% 4	490
	11th to 20th	Day	18% 12% 24% 25% 15% 6%	490
	21st to end	Day	27% 15% 21% 25% 9% 3	539
November	1st to 10th	Day	31% 10% 26% 21% 10% 2	326
	11th to 20th	Day	25% 14% 21% 19% 16% 6%	180
	21st to end	Day	32% 10% 18% 18% 18% 4	180
December	1st to 10th	Day	33% 8% 14% 21% 16% 8%	180
	11th to 20th	Day	43% 7% 13% 23% 10% 3	180
	21st to end	Day	38% 12% 15% 22% 12% 1	198
January	1st to 10th	Night	40% 9% 17% 19% 11% 3	760
	11th to 20th	Night	38% 6% 17% 18% 16% 5%	760
	21st to end	Night	32% 6% 14% 25% 20% 4	836
February	1st to 10th	Night	33% 7% 13% 27% 18% 2	760
	11th to 20th	Night	32% 7% 19% 25% 14% 2	744
	21st to end	Night	36% 8% 17% 25% 13% 1	628
March	1st to 10th	Night	38% 8% 18% 23% 13% 1	760
	11th to 20th	Night	29% 8% 18% 27% 16% 2	760
	21st to end	Night	39% 6% 18% 24% 12% 1	836
April	1st to 10th	Night	36% 7% 16% 22% 16% 3	760
	11th to 20th	Night	31% 7% 19% 25% 15% 3	710
	21st to end	Night	30% 5% 15% 29% 20% 2	570
May	1st to 10th	Night	25% 6% 19% 30% 18% 1	570
	11th to 20th	Night	25% 3 14% 27% 26% 4	412
	21st to end	Night	30% 5% 15% 30% 18% 3	411
June	1st to 10th	Night	26% 2 19% 32% 19% 2	380
	11th to 20th	Night	17% 4 26% 37% 14% 2	380
	21st to end	Night	20% 1 17% 37% 23% 2	380
July	1st to 10th	Night	15% 2 15% 37% 28% 3	370
	11th to 20th	Night	17% 3 21% 38% 19% 2	374
	21st to end	Night	21% 3 13% 36% 25% 3	624
August	1st to 10th	Night	24% 2 8% 29% 31% 7%	567
	11th to 20th	Night	15% 3 7% 30% 38% 7%	564
	21st to end	Night	15% 2 14% 36% 27% 6%	724
September	1st to 10th	Night	9% 2 15% 39% 31% 4	760
	11th to 20th	Night	13% 4 13% 29% 31% 10%	760
	21st to end	Night	16% 5% 18% 31% 23% 7%	760
October	1st to 10th	Night	17% 4 21% 28% 25% 6%	760
	11th to 20th	Night	21% 6% 16% 28% 22% 6%	760
	21st to end	Night	27% 7% 20% 26% 16% 5%	836
November	1st to 10th	Night	31% 8% 18% 26% 15% 2	748
	11th to 20th	Night	33% 8% 16% 26% 15% 2	760
	21st to end	Night	24% 9% 17% 29% 18% 3	760
December	1st to 10th	Night	29% 8% 15% 28% 17% 4	760
	11th to 20th	Night	37% 7% 17% 22% 15% 2	760
	21st to end	Night	41% 10% 15% 22% 11% 1	836

Page generated at 2024-10-30 10:19:22. Version ac07

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