Buckley
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Buckley 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	23% 10% 4 6% 6% 3 5% 4 5% 6% 29%	78992
	Night	24% 10% 4 7% 6% 3 4 4 4 5% 28%	80736
Transparency	Day	57% 9% 11% 15% 7% 1	78715
	Night	58% 9% 10% 14% 8% 2	80594
Seeing	Day	26% 14% 22% 25% 11% 2	14010
	Night	29% 11% 17% 25% 16% 2	22656

By Month

Percentage Cloud Cover NW (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	35% 16% 4 8% 6% 3 5% 3 4 4 11%	2539
	11th to 20th	Day	24% 13% 4 7% 6% 4 4 5% 4 6% 24%	2516
	21st to end	Day	38% 13% 4 7% 6% 2 3 3 4 5% 13%	2872
February	1st to 10th	Day	30% 11% 4 7% 6% 4 5% 4 4 7% 19%	1710
	11th to 20th	Day	31% 13% 5% 6% 6% 3 5% 4 4 5% 19%	1665
	21st to end	Day	30% 16% 5% 7% 5% 3 4 4 3 4 19%	1494
March	1st to 10th	Day	22% 13% 5% 8% 8% 4 6% 5% 5% 5% 19%	1933
	11th to 20th	Day	28% 13% 4 8% 6% 3 4 5% 4 5% 19%	2059
	21st to end	Day	26% 15% 6% 8% 8% 4 6% 5% 5% 6% 11%	2258
April	1st to 10th	Day	27% 14% 4 7% 6% 4 6% 6% 5% 5% 14%	2160
	11th to 20th	Day	25% 13% 4 7% 6% 3 5% 4 5% 6% 21%	2132
	21st to end	Day	25% 13% 4 9% 7% 4 5% 4 5% 5% 20%	2376
May	1st to 10th	Day	22% 9% 4 6% 6% 4 5% 6% 5% 6% 28%	2520
	11th to 20th	Day	21% 10% 4 8% 6% 3 5% 6% 6% 7% 25%	2477
	21st to end	Day	29% 10% 4 6% 6% 4 5% 5% 5% 6% 21%	2723
June	1st to 10th	Day	26% 9% 4 7% 6% 4 5% 4 5% 7% 24%	2520
	11th to 20th	Day	27% 10% 5% 8% 6% 4 6% 5% 5% 6% 18%	2651
	21st to end	Day	15% 7% 3 5% 5% 3 5% 5% 5% 7% 38%	2700
July	1st to 10th	Day	13% 6% 3 5% 4 2 4 5% 5% 7% 46%	2682
	11th to 20th	Day	12% 6% 3 5% 4 3 3 4 6% 7% 48%	2520
	21st to end	Day	9% 3 2 3 3 2 3 3 4 6% 61%	2741
August	1st to 10th	Day	11% 5% 2 4 4 2 4 5% 5% 7% 51%	2465
	11th to 20th	Day	9% 5% 2 4 3 2 3 4 6% 7% 56%	2298
	21st to end	Day	12% 7% 3 5% 5% 3 5% 4 5% 7% 44%	2448
September	1st to 10th	Day	12% 6% 1 4 4 2 4 5% 4 8% 51%	2160
	11th to 20th	Day	15% 6% 3 7% 5% 4 4 5% 5% 6% 39%	2160
	21st to end	Day	19% 6% 3 6% 6% 3 4 4 5% 5% 40%	1910
October	1st to 10th	Day	22% 8% 3 6% 5% 3 4 4 5% 7% 32%	1800
	11th to 20th	Day	24% 8% 3 6% 6% 2 5% 5% 5% 7% 30%	1800
	21st to end	Day	30% 9% 3 7% 5% 3 4 4 3 5% 26%	1868
November	1st to 10th	Day	32% 10% 4 7% 6% 4 4 5% 5% 6% 18%	1556
	11th to 20th	Day	33% 12% 3 6% 5% 3 5% 4 5% 4 21%	1520
	21st to end	Day	30% 11% 4 7% 5% 3 4 4 4 6% 22%	1520
December	1st to 10th	Day	28% 11% 4 6% 5% 4 4 4 3 5% 26%	1520
	11th to 20th	Day	31% 11% 5% 7% 5% 3 5% 4 4 6% 19%	1925
	21st to end	Day	25% 12% 5% 9% 7% 4 6% 5% 5% 5% 17%	2794
January	1st to 10th	Night	33% 17% 5% 8% 7% 3 4 3 4 4 11%	4406
	11th to 20th	Night	27% 12% 4 7% 5% 3 4 4 4 6% 23%	4382
	21st to end	Night	35% 12% 5% 7% 6% 3 4 4 4 5% 15%	4772
February	1st to 10th	Night	30% 13% 4 8% 6% 3 5% 4 4 5% 17%	2470
	11th to 20th	Night	28% 13% 4 6% 6% 3 4 3 3 5% 24%	2402
	21st to end	Night	26% 15% 4 6% 4 3 6% 6% 5% 5% 20%	1960
March	1st to 10th	Night	24% 12% 5% 7% 5% 3 5% 4 5% 8% 23%	2244
	11th to 20th	Night	26% 10% 4 7% 6% 4 5% 4 4 6% 24%	2066
	21st to end	Night	26% 15% 5% 8% 7% 3 5% 5% 5% 5% 16%	2098
April	1st to 10th	Night	25% 12% 4 7% 6% 4 5% 6% 5% 7% 19%	1800
	11th to 20th	Night	23% 10% 4 6% 6% 3 5% 4 5% 7% 26%	1779
	21st to end	Night	26% 10% 4 7% 6% 3 5% 5% 4 7% 22%	1580
May	1st to 10th	Night	21% 10% 4 7% 6% 2 4 5% 5% 5% 32%	1440
	11th to 20th	Night	20% 8% 2 6% 7% 3 6% 6% 6% 7% 29%	1416
	21st to end	Night	24% 9% 3 7% 6% 4 4 5% 4 6% 28%	1552
June	1st to 10th	Night	22% 9% 5% 7% 6% 3 5% 4 4 7% 28%	1440
	11th to 20th	Night	21% 11% 4 7% 7% 3 5% 5% 5% 7% 25%	1303
	21st to end	Night	14% 6% 3 5% 4 3 3 4 5% 7% 44%	1260
July	1st to 10th	Night	12% 6% 2 5% 4 3 4 3 5% 6% 51%	1273
	11th to 20th	Night	10% 6% 2 5% 4 2 2 4 3 6% 56%	1440
	21st to end	Night	6% 3 1 3 3 2 4 3 4 6% 65%	1576
August	1st to 10th	Night	10% 4 2 4 2 2 3 4 4 7% 59%	1471
	11th to 20th	Night	8% 4 1 3 4 2 3 3 4 6% 62%	1602
	21st to end	Night	12% 5% 2 4 4 3 4 4 4 6% 52%	1907
September	1st to 10th	Night	12% 4 2 4 3 2 4 4 5% 7% 53%	1800
	11th to 20th	Night	16% 7% 3 8% 5% 2 3 5% 4 5% 42%	1800
	21st to end	Night	17% 6% 2 5% 6% 3 4 5% 4 7% 41%	2046
October	1st to 10th	Night	21% 6% 3 6% 5% 4 5% 4 4 5% 38%	2160
	11th to 20th	Night	24% 8% 4 6% 5% 2 4 5% 4 4 33%	2160
	21st to end	Night	28% 8% 3 5% 5% 3 3 3 5% 6% 30%	2487
November	1st to 10th	Night	34% 8% 3 7% 5% 4 4 5% 5% 5% 21%	2522
	11th to 20th	Night	31% 10% 4 7% 6% 3 4 4 4 4 22%	2660
	21st to end	Night	29% 10% 4 7% 6% 2 4 5% 4 5% 22%	2660
December	1st to 10th	Night	27% 11% 3 7% 6% 3 5% 4 4 5% 24%	2660
	11th to 20th	Night	28% 13% 4 8% 7% 3 5% 4 5% 4 20%	3280
	21st to end	Night	26% 13% 5% 10% 8% 4 5% 6% 4 4 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	76% 7% 6% 7% 3 1	2539
	11th to 20th	Day	61% 9% 11% 12% 6% 2	2540
	21st to end	Day	71% 9% 7% 8% 4 1	2872
February	1st to 10th	Day	68% 8% 10% 9% 5% 1	1710
	11th to 20th	Day	68% 8% 7% 10% 5% 2	1674
	21st to end	Day	71% 7% 7% 11% 4	1494
March	1st to 10th	Day	66% 9% 11% 11% 3	1933
	11th to 20th	Day	69% 8% 7% 13% 3 1	2059
	21st to end	Day	76% 9% 9% 6% 1	2258
April	1st to 10th	Day	72% 9% 10% 7% 1	2160
	11th to 20th	Day	66% 8% 10% 10% 5% 1	2132
	21st to end	Day	69% 8% 10% 9% 3 1	2376
May	1st to 10th	Day	57% 9% 14% 14% 5%	2520
	11th to 20th	Day	59% 12% 12% 12% 4	2480
	21st to end	Day	65% 10% 13% 11% 1	2724
June	1st to 10th	Day	62% 10% 14% 10% 4	2520
	11th to 20th	Day	68% 10% 11% 9% 2	2651
	21st to end	Day	46% 10% 17% 16% 9% 1	2700
July	1st to 10th	Day	40% 8% 14% 22% 13% 2	2609
	11th to 20th	Day	34% 7% 13% 28% 17% 1	2445
	21st to end	Day	23% 6% 13% 35% 19% 4	2589
August	1st to 10th	Day	32% 8% 15% 28% 14% 3	2448
	11th to 20th	Day	27% 8% 17% 29% 16% 2	2298
	21st to end	Day	39% 7% 15% 27% 10% 1	2448
September	1st to 10th	Day	32% 8% 17% 25% 14% 5%	2160
	11th to 20th	Day	45% 9% 12% 16% 15% 3	2160
	21st to end	Day	46% 8% 15% 16% 12% 2	1910
October	1st to 10th	Day	51% 8% 11% 19% 9% 1	1800
	11th to 20th	Day	52% 8% 14% 18% 7% 1	1800
	21st to end	Day	61% 7% 8% 14% 10% 1	1868
November	1st to 10th	Day	67% 8% 11% 9% 4 1	1556
	11th to 20th	Day	69% 7% 8% 7% 7% 2	1520
	21st to end	Day	64% 8% 6% 10% 10% 2	1520
December	1st to 10th	Day	62% 8% 10% 10% 8% 2	1520
	11th to 20th	Day	65% 9% 11% 10% 5% 1	1928
	21st to end	Day	66% 10% 11% 10% 3	2794
January	1st to 10th	Night	77% 7% 6% 6% 2 1	4406
	11th to 20th	Night	61% 8% 9% 15% 6% 2	4420
	21st to end	Night	69% 10% 8% 7% 6% 1	4772
February	1st to 10th	Night	69% 8% 9% 9% 5% 1	2470
	11th to 20th	Night	63% 8% 9% 10% 6% 3	2404
	21st to end	Night	67% 9% 9% 10% 4	1960
March	1st to 10th	Night	60% 8% 12% 14% 5%	2244
	11th to 20th	Night	62% 7% 11% 14% 5% 1	2067
	21st to end	Night	68% 13% 10% 9% 1	2098
April	1st to 10th	Night	66% 11% 12% 9% 1	1800
	11th to 20th	Night	60% 10% 11% 13% 6% 1	1779
	21st to end	Night	65% 10% 9% 10% 5% 1	1580
May	1st to 10th	Night	55% 9% 14% 14% 8%	1440
	11th to 20th	Night	54% 11% 16% 12% 6% 1	1416
	21st to end	Night	58% 12% 13% 15% 2	1552
June	1st to 10th	Night	58% 10% 14% 13% 5%	1440
	11th to 20th	Night	60% 9% 17% 11% 2	1303
	21st to end	Night	42% 9% 17% 20% 9% 2	1260
July	1st to 10th	Night	36% 9% 12% 24% 15% 4	1238
	11th to 20th	Night	34% 6% 11% 28% 19% 3	1392
	21st to end	Night	23% 6% 10% 33% 20% 8%	1488
August	1st to 10th	Night	26% 7% 13% 28% 20% 4	1463
	11th to 20th	Night	26% 7% 15% 29% 17% 5%	1602
	21st to end	Night	34% 7% 14% 28% 14% 1	1907
September	1st to 10th	Night	32% 8% 13% 24% 17% 5%	1800
	11th to 20th	Night	46% 9% 8% 17% 15% 5%	1800
	21st to end	Night	42% 10% 13% 17% 13% 4	2046
October	1st to 10th	Night	47% 8% 13% 21% 10% 2	2160
	11th to 20th	Night	54% 7% 9% 19% 9% 2	2160
	21st to end	Night	55% 7% 10% 15% 12% 1	2487
November	1st to 10th	Night	66% 9% 10% 11% 4 1	2522
	11th to 20th	Night	66% 7% 8% 10% 6% 3	2660
	21st to end	Night	65% 7% 7% 9% 11% 2	2660
December	1st to 10th	Night	63% 8% 8% 10% 8% 2	2660
	11th to 20th	Night	65% 9% 11% 10% 5% 1	3276
	21st to end	Night	67% 12% 10% 8% 4	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	37% 19% 19% 11% 10% 3	180
	11th to 20th	Day	32% 19% 20% 18% 9% 1	180
	21st to end	Day	38% 19% 17% 16% 10% 1	250
February	1st to 10th	Day	40% 14% 22% 16% 6% 1	370
	11th to 20th	Day	42% 16% 22% 15% 5% 1	365
	21st to end	Day	37% 19% 22% 17% 4 1	346
March	1st to 10th	Day	29% 22% 26% 18% 5%	460
	11th to 20th	Day	30% 19% 23% 21% 7% 1	449
	21st to end	Day	35% 21% 23% 14% 7%	462
April	1st to 10th	Day	36% 17% 21% 17% 8% 1	420
	11th to 20th	Day	31% 21% 27% 12% 7% 2	412
	21st to end	Day	28% 20% 28% 18% 6% 1	420
May	1st to 10th	Day	21% 17% 27% 26% 7% 2	423
	11th to 20th	Day	32% 10% 25% 21% 9% 3	448
	21st to end	Day	28% 14% 22% 24% 9% 2	485
June	1st to 10th	Day	28% 12% 22% 23% 13% 2	450
	11th to 20th	Day	27% 17% 27% 20% 8% 1	581
	21st to end	Day	16% 10% 22% 33% 16% 3	630
July	1st to 10th	Day	15% 8% 22% 40% 13% 2	604
	11th to 20th	Day	12% 8% 26% 36% 15% 3	444
	21st to end	Day	9% 4 23% 38% 22% 4	487
August	1st to 10th	Day	11% 7% 17% 40% 18% 7%	447
	11th to 20th	Day	8% 4 18% 43% 21% 6%	437
	21st to end	Day	11% 12% 26% 35% 12% 5%	495
September	1st to 10th	Day	15% 8% 25% 38% 11% 2	450
	11th to 20th	Day	18% 12% 22% 31% 15% 3	450
	21st to end	Day	19% 15% 22% 26% 16% 2	450
October	1st to 10th	Day	27% 11% 22% 21% 17% 2	450
	11th to 20th	Day	29% 14% 19% 21% 13% 4	450
	21st to end	Day	29% 19% 20% 20% 7% 4	383
November	1st to 10th	Day	40% 14% 16% 19% 11%	214
	11th to 20th	Day	39% 18% 13% 12% 13% 4	180
	21st to end	Day	33% 14% 22% 14% 12% 5%	180
December	1st to 10th	Day	42% 15% 17% 9% 11% 6%	180
	11th to 20th	Day	39% 14% 23% 17% 7% 1	180
	21st to end	Day	39% 15% 19% 18% 9% 1	198
January	1st to 10th	Night	43% 15% 19% 17% 6% 1	760
	11th to 20th	Night	34% 14% 19% 22% 9% 1	760
	21st to end	Night	34% 12% 18% 27% 8% 1	836
February	1st to 10th	Night	38% 11% 20% 23% 7% 1	760
	11th to 20th	Night	34% 13% 17% 26% 9%	744
	21st to end	Night	35% 16% 20% 21% 6% 1	628
March	1st to 10th	Night	29% 17% 19% 24% 11% 1	760
	11th to 20th	Night	32% 15% 19% 23% 10% 1	752
	21st to end	Night	33% 16% 20% 23% 8% 1	792
April	1st to 10th	Night	32% 13% 20% 24% 10% 2	720
	11th to 20th	Night	28% 13% 21% 25% 10% 3	711
	21st to end	Night	31% 12% 17% 27% 12% 1	500
May	1st to 10th	Night	24% 11% 17% 28% 18% 2	360
	11th to 20th	Night	25% 6% 14% 29% 24% 2	354
	21st to end	Night	27% 9% 13% 25% 23% 3	389
June	1st to 10th	Night	27% 8% 16% 26% 21% 3	360
	11th to 20th	Night	26% 11% 16% 28% 18% 1	360
	21st to end	Night	18% 6% 15% 28% 32% 3	360
July	1st to 10th	Night	14% 4 10% 32% 35% 5%	350
	11th to 20th	Night	13% 3 9% 39% 32% 4	348
	21st to end	Night	8% 4 10% 29% 45% 5%	394
August	1st to 10th	Night	16% 2 6% 24% 41% 10%	397
	11th to 20th	Night	10% 1 8% 27% 42% 12%	534
	21st to end	Night	14% 6% 11% 32% 34% 5%	719
September	1st to 10th	Night	14% 4 12% 38% 28% 4	720
	11th to 20th	Night	17% 8% 13% 24% 33% 7%	720
	21st to end	Night	21% 7% 12% 32% 25% 3	720
October	1st to 10th	Night	24% 7% 16% 26% 25% 3	720
	11th to 20th	Night	27% 10% 16% 25% 18% 4	720
	21st to end	Night	31% 11% 18% 27% 10% 3	792
November	1st to 10th	Night	36% 11% 25% 21% 6%	740
	11th to 20th	Night	38% 13% 19% 23% 6% 1	760
	21st to end	Night	35% 13% 19% 23% 10%	760
December	1st to 10th	Night	31% 13% 22% 24% 9% 1	760
	11th to 20th	Night	40% 11% 22% 19% 7% 1	760
	21st to end	Night	45% 15% 19% 17% 5%	836

Page generated at 2024-03-15 11:01:46. Version ac07

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