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 2024-03-08.

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% 4 6% 5% 3 4 4 5% 7% 32%	78614
	Night	22% 12% 4 7% 5% 3 4 4 4 6% 29%	80983
Transparency	Day	52% 3 12% 20% 10% 3	78329
	Night	57% 3 11% 17% 9% 3	80789
Seeing	Day	22% 11% 29% 26% 10% 2	14008
	Night	28% 6% 16% 28% 19% 4	23140

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% 17% 5% 9% 6% 3 5% 3 4 5% 15%	2539
	11th to 20th	Day	38% 12% 3 5% 5% 3 4 3 3 4 20%	2798
	21st to end	Day	32% 12% 4 7% 6% 3 5% 4 5% 5% 18%	3146
February	1st to 10th	Day	26% 10% 4 7% 7% 3 5% 5% 5% 5% 21%	1710
	11th to 20th	Day	24% 12% 5% 8% 6% 4 4 4 4 5% 24%	1665
	21st to end	Day	26% 13% 5% 9% 6% 3 5% 4 4 5% 22%	1471
March	1st to 10th	Day	27% 12% 5% 7% 5% 4 4 4 5% 7% 20%	2059
	11th to 20th	Day	24% 13% 4 8% 6% 3 5% 5% 6% 6% 21%	1980
	21st to end	Day	26% 11% 4 8% 6% 4 6% 4 7% 5% 17%	2178
April	1st to 10th	Day	27% 13% 5% 7% 6% 3 4 4 4 6% 20%	2124
	11th to 20th	Day	22% 12% 4 7% 6% 3 4 4 5% 7% 25%	2163
	21st to end	Day	21% 8% 3 6% 6% 3 5% 6% 7% 8% 28%	2340
May	1st to 10th	Day	16% 10% 3 6% 5% 4 5% 4 5% 8% 35%	2340
	11th to 20th	Day	17% 12% 3 7% 5% 3 5% 4 6% 9% 28%	2440
	21st to end	Day	19% 12% 4 6% 5% 3 5% 4 5% 9% 28%	2723
June	1st to 10th	Day	18% 10% 4 6% 7% 3 4 4 5% 8% 31%	2520
	11th to 20th	Day	13% 10% 3 6% 5% 3 4 4 5% 9% 37%	2520
	21st to end	Day	10% 7% 2 5% 5% 3 3 4 5% 8% 48%	2520
July	1st to 10th	Day	5% 9% 3 5% 4 2 3 3 5% 9% 51%	2520
	11th to 20th	Day	8% 8% 2 4 4 2 3 4 6% 8% 49%	2511
	21st to end	Day	6% 8% 3 5% 4 3 3 4 6% 10% 49%	2546
August	1st to 10th	Day	6% 9% 3 5% 6% 2 4 4 7% 10% 44%	2328
	11th to 20th	Day	6% 6% 3 5% 4 2 3 4 5% 10% 52%	2298
	21st to end	Day	7% 7% 2 5% 4 2 3 3 5% 10% 52%	2482
September	1st to 10th	Day	3 5% 2 4 3 3 3 4 6% 9% 59%	2160
	11th to 20th	Day	10% 8% 3 6% 5% 2 4 4 6% 8% 44%	2052
	21st to end	Day	10% 5% 3 5% 4 2 4 5% 6% 9% 48%	1958
October	1st to 10th	Day	13% 8% 3 6% 5% 3 4 4 6% 7% 42%	1800
	11th to 20th	Day	16% 6% 3 5% 5% 3 5% 5% 6% 8% 38%	1800
	21st to end	Day	20% 9% 3 7% 5% 3 3 5% 5% 7% 33%	1980
November	1st to 10th	Day	26% 11% 3 7% 5% 3 5% 4 6% 6% 22%	1661
	11th to 20th	Day	24% 11% 5% 7% 7% 4 4 4 5% 7% 22%	1520
	21st to end	Day	24% 10% 4 6% 5% 3 4 4 5% 6% 29%	1520
December	1st to 10th	Day	21% 9% 4 8% 6% 3 4 5% 5% 6% 29%	1520
	11th to 20th	Day	27% 11% 4 7% 7% 3 5% 4 6% 5% 20%	1928
	21st to end	Day	32% 13% 5% 9% 7% 3 4 4 4 5% 14%	2794
January	1st to 10th	Night	33% 15% 5% 8% 7% 4 5% 4 4 4 13%	4406
	11th to 20th	Night	36% 15% 4 7% 5% 2 3 3 3 4 19%	4168
	21st to end	Night	39% 12% 4 6% 5% 3 3 3 4 5% 17%	4521
February	1st to 10th	Night	24% 12% 4 7% 7% 4 4 5% 6% 7% 20%	2470
	11th to 20th	Night	25% 13% 4 8% 6% 3 3 4 4 5% 25%	2402
	21st to end	Night	28% 12% 4 7% 7% 3 3 4 5% 5% 22%	1980
March	1st to 10th	Night	26% 14% 4 7% 6% 3 5% 4 5% 6% 21%	2061
	11th to 20th	Night	23% 11% 5% 8% 6% 4 5% 4 4 6% 23%	1980
	21st to end	Night	30% 13% 5% 8% 6% 2 5% 3 4 6% 19%	2178
April	1st to 10th	Night	28% 12% 3 7% 6% 3 5% 4 5% 5% 23%	1834
	11th to 20th	Night	21% 13% 4 7% 5% 2 5% 4 4 6% 28%	1741
	21st to end	Night	24% 11% 4 6% 6% 3 5% 5% 5% 6% 26%	1620
May	1st to 10th	Night	17% 11% 3 6% 6% 3 5% 3 4 6% 35%	1620
	11th to 20th	Night	17% 13% 4 8% 6% 3 4 4 6% 8% 27%	1452
	21st to end	Night	19% 15% 3 6% 4 3 4 5% 5% 8% 27%	1552
June	1st to 10th	Night	19% 11% 4 6% 5% 2 5% 4 4 8% 32%	1440
	11th to 20th	Night	13% 9% 4 7% 5% 2 4 4 6% 8% 38%	1440
	21st to end	Night	11% 11% 2 5% 4 2 3 4 5% 7% 46%	1440
July	1st to 10th	Night	8% 13% 2 4 4 2 3 3 5% 8% 48%	1440
	11th to 20th	Night	9% 12% 3 5% 4 2 3 3 4 7% 48%	1445
	21st to end	Night	7% 16% 3 6% 4 2 3 3 4 7% 46%	1773
August	1st to 10th	Night	7% 15% 3 6% 5% 3 3 3 4 7% 44%	1611
	11th to 20th	Night	6% 12% 3 5% 3 1 2 3 5% 9% 50%	1602
	21st to end	Night	8% 10% 2 5% 4 2 3 3 3 6% 54%	1873
September	1st to 10th	Night	5% 6% 2 4 4 2 4 4 5% 7% 58%	1800
	11th to 20th	Night	8% 9% 3 5% 5% 2 3 4 5% 7% 49%	1906
	21st to end	Night	13% 7% 3 5% 5% 3 3 4 4 7% 45%	2001
October	1st to 10th	Night	13% 9% 3 6% 5% 2 3 4 4 6% 44%	2160
	11th to 20th	Night	15% 9% 3 5% 5% 3 4 5% 5% 6% 40%	2160
	21st to end	Night	20% 10% 3 7% 6% 2 4 4 4 5% 35%	2376
November	1st to 10th	Night	25% 10% 4 7% 6% 3 4 5% 5% 7% 25%	2413
	11th to 20th	Night	26% 10% 4 8% 6% 4 5% 5% 4 5% 23%	2660
	21st to end	Night	19% 10% 4 7% 5% 4 5% 4 5% 6% 30%	2660
December	1st to 10th	Night	22% 10% 4 6% 6% 3 5% 4 5% 6% 29%	2660
	11th to 20th	Night	29% 12% 4 7% 5% 3 5% 4 5% 7% 19%	3276
	21st to end	Night	28% 13% 5% 8% 7% 4 4 4 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	65% 3 11% 16% 4	2059
	11th to 20th	Day	64% 4 11% 16% 6%	1980
	21st to end	Day	68% 4 12% 14% 2	2178
April	1st to 10th	Day	67% 2 13% 13% 5%	2124
	11th to 20th	Day	61% 4 13% 14% 7% 1	2166
	21st to end	Day	54% 4 15% 19% 6% 1	2340
May	1st to 10th	Day	49% 3 20% 21% 7% 1	2340
	11th to 20th	Day	53% 4 17% 18% 6% 2	2443
	21st to end	Day	55% 5% 18% 19% 2	2724
June	1st to 10th	Day	54% 3 13% 25% 4	2520
	11th to 20th	Day	46% 3 20% 25% 6%	2520
	21st to end	Day	35% 3 17% 31% 12% 2	2520
July	1st to 10th	Day	32% 3 14% 27% 21% 4	2451
	11th to 20th	Day	31% 3 8% 26% 24% 7%	2436
	21st to end	Day	29% 4 6% 31% 28% 4	2405
August	1st to 10th	Day	35% 3 13% 32% 14% 3	2312
	11th to 20th	Day	28% 3 12% 33% 21% 3	2298
	21st to end	Day	31% 3 11% 30% 22% 3	2482
September	1st to 10th	Day	23% 2 9% 34% 22% 9%	2160
	11th to 20th	Day	37% 3 13% 27% 16% 4	2052
	21st to end	Day	33% 4 14% 28% 17% 5%	1958
October	1st to 10th	Day	42% 3 10% 23% 16% 6%	1800
	11th to 20th	Day	43% 4 14% 21% 16% 3	1800
	21st to end	Day	51% 3 11% 18% 12% 6%	1980
November	1st to 10th	Day	62% 4 9% 15% 9% 1	1661
	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	65% 3 9% 17% 6%	2061
	11th to 20th	Night	63% 3 12% 16% 5% 1	1980
	21st to end	Night	69% 4 12% 12% 3	2178
April	1st to 10th	Night	64% 3 14% 14% 5%	1834
	11th to 20th	Night	58% 5% 13% 16% 6% 2	1741
	21st to end	Night	59% 3 12% 18% 6% 1	1620
May	1st to 10th	Night	52% 4 15% 21% 7% 2	1620
	11th to 20th	Night	55% 4 17% 15% 6% 3	1452
	21st to end	Night	55% 4 19% 18% 2	1552
June	1st to 10th	Night	52% 3 19% 24% 2	1440
	11th to 20th	Night	44% 5% 20% 26% 5%	1440
	21st to end	Night	38% 2 17% 33% 8% 3	1440
July	1st to 10th	Night	35% 4 11% 27% 19% 4	1400
	11th to 20th	Night	36% 3 8% 25% 23% 5%	1397
	21st to end	Night	39% 3 4 27% 22% 4	1674
August	1st to 10th	Night	41% 3 12% 29% 13% 3	1602
	11th to 20th	Night	33% 2 8% 32% 20% 4	1602
	21st to end	Night	33% 2 9% 31% 20% 4	1873
September	1st to 10th	Night	26% 3 9% 31% 21% 11%	1800
	11th to 20th	Night	34% 4 14% 27% 18% 3	1906
	21st to end	Night	40% 3 13% 20% 16% 8%	2001
October	1st to 10th	Night	42% 3 11% 21% 17% 6%	2160
	11th to 20th	Night	45% 3 15% 19% 16% 3	2160
	21st to end	Night	52% 2 11% 15% 12% 7%	2376
November	1st to 10th	Night	59% 3 12% 15% 10% 1	2413
	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	37% 13% 23% 20% 6%	449
	11th to 20th	Day	32% 10% 28% 19% 9% 2	420
	21st to end	Day	30% 19% 24% 20% 6% 1	462
April	1st to 10th	Day	33% 17% 23% 18% 6% 2	420
	11th to 20th	Day	29% 17% 28% 17% 5% 3	412
	21st to end	Day	24% 16% 33% 19% 8% 1	420
May	1st to 10th	Day	21% 16% 35% 21% 7% 1	423
	11th to 20th	Day	31% 10% 25% 24% 8% 1	448
	21st to end	Day	23% 11% 34% 24% 6% 1	485
June	1st to 10th	Day	18% 11% 35% 25% 10% 1	450
	11th to 20th	Day	17% 16% 41% 21% 4	450
	21st to end	Day	9% 9% 39% 35% 6% 2	450
July	1st to 10th	Day	10% 6% 41% 33% 9%	446
	11th to 20th	Day	7% 7% 44% 34% 8% 1	444
	21st to end	Day	8% 3 39% 40% 8% 1	487
August	1st to 10th	Day	8% 3 28% 41% 17% 3	447
	11th to 20th	Day	8% 3 29% 41% 15% 3	437
	21st to end	Day	9% 5% 36% 36% 10% 4	495
September	1st to 10th	Day	6% 5% 32% 36% 18% 3	450
	11th to 20th	Day	17% 7% 25% 33% 16% 2	450
	21st to end	Day	14% 11% 28% 30% 13% 4	450
October	1st to 10th	Day	19% 10% 24% 29% 13% 4	450
	11th to 20th	Day	18% 12% 24% 24% 16% 6%	450
	21st to end	Day	27% 12% 21% 26% 10% 4	495
November	1st to 10th	Day	30% 10% 26% 21% 10% 2	321
	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	37% 8% 18% 23% 12% 1	750
	11th to 20th	Night	29% 9% 18% 27% 16% 2	720
	21st to end	Night	39% 6% 18% 23% 13% 2	792
April	1st to 10th	Night	37% 8% 17% 20% 16% 3	720
	11th to 20th	Night	31% 7% 18% 26% 15% 3	673
	21st to end	Night	31% 5% 14% 29% 20% 2	540
May	1st to 10th	Night	25% 6% 18% 30% 19% 1	540
	11th to 20th	Night	25% 3 13% 28% 27% 4	390
	21st to end	Night	30% 5% 15% 29% 18% 3	389
June	1st to 10th	Night	25% 2 19% 32% 19% 3	360
	11th to 20th	Night	18% 4 24% 38% 14% 2	360
	21st to end	Night	19% 1 17% 36% 24% 3	360
July	1st to 10th	Night	16% 2 15% 37% 28% 3	350
	11th to 20th	Night	17% 3 20% 38% 19% 3	353
	21st to end	Night	20% 3 12% 37% 26% 3	591
August	1st to 10th	Night	21% 2 8% 30% 32% 7%	537
	11th to 20th	Night	15% 2 7% 31% 38% 7%	534
	21st to end	Night	15% 2 14% 36% 27% 5%	685
September	1st to 10th	Night	8% 2 16% 39% 31% 4	720
	11th to 20th	Night	12% 4 12% 30% 32% 10%	720
	21st to end	Night	17% 5% 18% 30% 23% 7%	720
October	1st to 10th	Night	17% 4 20% 28% 24% 6%	720
	11th to 20th	Night	20% 7% 17% 28% 22% 7%	720
	21st to end	Night	26% 7% 20% 26% 16% 5%	792
November	1st to 10th	Night	31% 8% 18% 26% 16% 2	740
	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 2024-03-05 04:24:01. Version ac07

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