Knox Octagon Barn
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Knox Octagon Barn clear sky chart from 2005-11-06 to 2026-03-03.

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	14% 9% 3 9% 6% 5% 5% 4 6% 7% 31%	131040
	Night	15% 9% 3 9% 6% 5% 5% 4 6% 7% 31%	130138
Transparency	Day	49% 6% 12% 20% 11% 1	134528
	Night	49% 6% 12% 19% 12% 1	134737
Seeing	Day	22% 18% 29% 20% 9% 2	16392
	Night	20% 17% 31% 24% 7% 1	25603

By Month

Percentage Cloud Cover NE (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	10% 12% 5% 18% 9% 7% 6% 5% 5% 5% 18%	4661
	11th to 20th	Day	11% 13% 5% 12% 7% 7% 7% 4 6% 6% 21%	4650
	21st to end	Day	12% 12% 4 9% 6% 6% 5% 4 6% 7% 29%	5382
February	1st to 10th	Day	13% 11% 4 11% 8% 7% 6% 5% 5% 6% 24%	1890
	11th to 20th	Day	10% 11% 5% 13% 8% 5% 5% 4 7% 6% 25%	1998
	21st to end	Day	14% 11% 5% 11% 6% 5% 5% 3 5% 6% 28%	1730
March	1st to 10th	Day	18% 11% 4 10% 6% 5% 5% 3 4 5% 28%	4496
	11th to 20th	Day	13% 12% 4 8% 5% 4 4 3 5% 6% 35%	4782
	21st to end	Day	16% 10% 4 9% 6% 5% 4 3 4 5% 33%	5920
April	1st to 10th	Day	17% 12% 3 9% 6% 4 4 3 5% 5% 33%	2400
	11th to 20th	Day	15% 10% 3 8% 5% 4 4 4 5% 5% 36%	2374
	21st to end	Day	19% 8% 3 8% 5% 4 5% 4 5% 6% 33%	2470
May	1st to 10th	Day	30% 10% 3 7% 5% 4 4 3 4 6% 23%	6061
	11th to 20th	Day	15% 9% 4 9% 6% 6% 5% 4 5% 7% 31%	6318
	21st to end	Day	18% 8% 3 8% 5% 5% 6% 5% 7% 8% 29%	6949
June	1st to 10th	Day	16% 6% 2 8% 5% 5% 6% 5% 7% 8% 32%	2800
	11th to 20th	Day	15% 7% 2 7% 5% 5% 6% 5% 6% 9% 33%	2800
	21st to end	Day	14% 8% 3 7% 5% 5% 4 5% 7% 9% 33%	2800
July	1st to 10th	Day	9% 7% 3 8% 6% 6% 6% 5% 7% 9% 33%	6360
	11th to 20th	Day	7% 5% 2 8% 6% 6% 6% 5% 8% 10% 36%	6360
	21st to end	Day	12% 6% 2 7% 5% 5% 5% 4 6% 8% 40%	6926
August	1st to 10th	Day	15% 6% 3 8% 5% 5% 5% 4 6% 8% 34%	4504
	11th to 20th	Day	11% 7% 3 8% 7% 6% 6% 5% 7% 10% 30%	3864
	21st to end	Day	11% 4 2 7% 5% 5% 6% 5% 8% 10% 38%	4312
September	1st to 10th	Day	13% 5% 2 6% 5% 5% 6% 4 5% 7% 43%	2400
	11th to 20th	Day	12% 5% 2 5% 3 4 4 4 5% 7% 49%	2325
	21st to end	Day	16% 6% 2 6% 4 4 5% 4 7% 8% 38%	2200
October	1st to 10th	Day	17% 8% 3 7% 5% 5% 4 4 5% 7% 36%	2063
	11th to 20th	Day	14% 8% 2 8% 5% 4 3 4 6% 8% 38%	2000
	21st to end	Day	20% 10% 3 7% 5% 5% 5% 4 5% 7% 30%	2009
November	1st to 10th	Day	12% 11% 3 6% 5% 4 3 3 5% 6% 41%	1851
	11th to 20th	Day	13% 10% 3 8% 6% 5% 5% 4 5% 7% 35%	1890
	21st to end	Day	16% 12% 4 8% 6% 5% 5% 3 6% 6% 30%	1701
December	1st to 10th	Day	12% 13% 5% 15% 8% 6% 6% 4 6% 6% 18%	2680
	11th to 20th	Day	16% 12% 4 8% 5% 5% 5% 4 6% 7% 28%	3066
	21st to end	Day	16% 12% 7% 10% 6% 5% 5% 4 5% 7% 23%	4048
January	1st to 10th	Night	12% 13% 5% 17% 8% 6% 5% 4 6% 6% 19%	8234
	11th to 20th	Night	10% 14% 5% 15% 8% 6% 6% 4 6% 7% 19%	8235
	21st to end	Night	11% 10% 4 9% 6% 7% 7% 5% 6% 6% 28%	8786
February	1st to 10th	Night	13% 11% 4 11% 7% 5% 5% 5% 7% 6% 26%	2730
	11th to 20th	Night	10% 11% 4 12% 7% 5% 6% 6% 7% 7% 25%	2506
	21st to end	Night	16% 10% 4 10% 6% 5% 5% 4 5% 6% 27%	2076
March	1st to 10th	Night	17% 9% 3 9% 8% 5% 6% 4 6% 7% 26%	5389
	11th to 20th	Night	14% 10% 3 7% 5% 5% 5% 4 5% 7% 35%	5173
	21st to end	Night	18% 11% 3 9% 6% 6% 5% 4 5% 5% 29%	5011
April	1st to 10th	Night	17% 10% 4 9% 6% 5% 5% 4 5% 6% 29%	2000
	11th to 20th	Night	20% 9% 2 8% 5% 4 4 3 5% 6% 34%	1975
	21st to end	Night	18% 8% 2 6% 4 4 4 4 5% 6% 37%	1930
May	1st to 10th	Night	30% 9% 3 8% 5% 4 4 3 4 6% 24%	3921
	11th to 20th	Night	14% 11% 3 8% 6% 5% 5% 4 5% 7% 31%	3575
	21st to end	Night	19% 9% 3 8% 5% 5% 5% 4 6% 7% 30%	3926
June	1st to 10th	Night	16% 8% 2 7% 4 4 4 4 5% 7% 40%	1600
	11th to 20th	Night	15% 5% 2 6% 5% 4 5% 4 7% 10% 39%	1600
	21st to end	Night	11% 4 1 6% 5% 6% 5% 4 6% 9% 43%	1600
July	1st to 10th	Night	8% 5% 3 9% 6% 5% 5% 4 6% 9% 40%	3600
	11th to 20th	Night	9% 7% 2 8% 5% 5% 6% 4 7% 8% 38%	3600
	21st to end	Night	9% 6% 2 7% 5% 4 5% 4 5% 6% 47%	3926
August	1st to 10th	Night	17% 7% 2 7% 4 5% 5% 4 6% 6% 37%	2641
	11th to 20th	Night	13% 8% 3 7% 5% 4 5% 4 6% 7% 39%	3150
	21st to end	Night	12% 5% 2 5% 4 5% 5% 3 6% 8% 45%	3586
September	1st to 10th	Night	13% 6% 3 5% 4 4 4 4 6% 6% 46%	2000
	11th to 20th	Night	13% 4 1 6% 3 3 4 3 5% 6% 53%	2075
	21st to end	Night	14% 5% 2 6% 4 5% 4 4 6% 7% 44%	2200
October	1st to 10th	Night	18% 7% 3 6% 4 3 4 3 6% 6% 39%	2334
	11th to 20th	Night	15% 7% 3 6% 4 4 4 4 6% 7% 40%	2400
	21st to end	Night	20% 9% 2 8% 4 5% 4 4 6% 6% 33%	2830
November	1st to 10th	Night	14% 9% 3 7% 5% 4 3 4 5% 6% 40%	2667
	11th to 20th	Night	15% 9% 4 7% 6% 5% 5% 4 6% 6% 34%	2730
	21st to end	Night	14% 9% 3 8% 6% 5% 5% 4 5% 7% 33%	2914
December	1st to 10th	Night	13% 13% 4 10% 6% 7% 5% 5% 7% 7% 22%	4720
	11th to 20th	Night	19% 10% 4 10% 5% 5% 5% 4 5% 5% 29%	5348
	21st to end	Night	19% 13% 7% 9% 5% 5% 4 3 5% 5% 25%	7150

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	61% 5% 12% 15% 5% 1	4662
	11th to 20th	Day	57% 6% 10% 14% 11% 2	4680
	21st to end	Day	49% 7% 10% 23% 10% 1	5382
February	1st to 10th	Day	57% 6% 12% 15% 9% 1	1890
	11th to 20th	Day	55% 5% 12% 18% 8% 2	2007
	21st to end	Day	54% 5% 12% 17% 11% 1	1730
March	1st to 10th	Day	55% 6% 9% 14% 11% 4	4499
	11th to 20th	Day	48% 4 17% 20% 7% 4	4782
	21st to end	Day	52% 5% 8% 13% 19% 3	5920
April	1st to 10th	Day	52% 4 9% 21% 12% 2	2400
	11th to 20th	Day	49% 5% 11% 20% 14% 2	2374
	21st to end	Day	50% 5% 11% 18% 13% 3	2470
May	1st to 10th	Day	61% 6% 9% 14% 9% 1	6072
	11th to 20th	Day	50% 7% 13% 20% 9% 1	6322
	21st to end	Day	49% 8% 12% 21% 9% 1	6949
June	1st to 10th	Day	47% 9% 13% 19% 12% 1	2800
	11th to 20th	Day	46% 7% 15% 20% 11% 1	2800
	21st to end	Day	46% 7% 14% 21% 11% 1	2800
July	1st to 10th	Day	46% 7% 13% 22% 11% 1	6290
	11th to 20th	Day	41% 7% 15% 24% 12% 1	6285
	21st to end	Day	42% 5% 12% 28% 12%	6728
August	1st to 10th	Day	48% 7% 14% 20% 11% 1	4490
	11th to 20th	Day	46% 7% 16% 25% 5%	3900
	21st to end	Day	37% 9% 13% 30% 10% 1	4312
September	1st to 10th	Day	40% 7% 12% 25% 16% 1	2400
	11th to 20th	Day	35% 5% 12% 28% 19% 1	2325
	21st to end	Day	41% 8% 11% 24% 14% 2	2200
October	1st to 10th	Day	44% 7% 8% 22% 18% 1	3362
	11th to 20th	Day	38% 6% 11% 25% 16% 4	3240
	21st to end	Day	37% 6% 14% 26% 13% 3	3221
November	1st to 10th	Day	43% 6% 13% 24% 13% 1	1851
	11th to 20th	Day	48% 6% 12% 19% 14% 2	1890
	21st to end	Day	52% 6% 16% 18% 7% 1	1701
December	1st to 10th	Day	61% 5% 13% 16% 4	2680
	11th to 20th	Day	54% 4 15% 18% 9% 1	3066
	21st to end	Day	58% 6% 9% 15% 9% 2	4048
January	1st to 10th	Night	60% 7% 11% 14% 7%	8234
	11th to 20th	Night	60% 7% 11% 10% 10% 2	8280
	21st to end	Night	52% 6% 10% 15% 14% 2	8786
February	1st to 10th	Night	54% 7% 12% 18% 8% 1	2730
	11th to 20th	Night	54% 6% 15% 16% 9% 1	2508
	21st to end	Night	53% 6% 13% 17% 9% 2	2076
March	1st to 10th	Night	51% 7% 13% 16% 12% 1	5399
	11th to 20th	Night	47% 5% 19% 19% 8% 2	5174
	21st to end	Night	52% 5% 8% 17% 17% 2	5011
April	1st to 10th	Night	53% 6% 12% 18% 10% 2	2000
	11th to 20th	Night	49% 5% 12% 18% 15% 1	1975
	21st to end	Night	46% 6% 12% 18% 15% 3	1930
May	1st to 10th	Night	61% 6% 10% 12% 10% 2	3927
	11th to 20th	Night	51% 8% 12% 21% 8% 1	3576
	21st to end	Night	51% 8% 12% 17% 10% 1	3927
June	1st to 10th	Night	43% 7% 11% 24% 14% 2	1600
	11th to 20th	Night	39% 8% 15% 26% 12%	1600
	21st to end	Night	36% 9% 16% 25% 14% 1	1600
July	1st to 10th	Night	40% 6% 15% 23% 15% 1	3560
	11th to 20th	Night	42% 7% 15% 22% 14%	3552
	21st to end	Night	36% 6% 12% 33% 12% 1	3809
August	1st to 10th	Night	45% 7% 14% 24% 9%	2631
	11th to 20th	Night	42% 6% 18% 25% 9%	3180
	21st to end	Night	33% 8% 12% 36% 11% 1	3586
September	1st to 10th	Night	37% 7% 11% 27% 16% 1	2000
	11th to 20th	Night	31% 6% 12% 28% 22% 1	2075
	21st to end	Night	40% 7% 12% 24% 17% 1	2200
October	1st to 10th	Night	46% 7% 11% 23% 12% 1	3815
	11th to 20th	Night	34% 7% 12% 24% 19% 3	3899
	21st to end	Night	40% 5% 15% 29% 11% 1	4568
November	1st to 10th	Night	42% 6% 11% 22% 16% 2	2667
	11th to 20th	Night	47% 5% 13% 19% 13% 2	2730
	21st to end	Night	47% 7% 18% 20% 7% 1	2914
December	1st to 10th	Night	54% 7% 14% 20% 5%	4720
	11th to 20th	Night	54% 4 13% 15% 13% 1	5348
	21st to end	Night	60% 6% 9% 13% 10% 3	7150

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	28% 28% 30% 11% 3	220
	11th to 20th	Day	35% 28% 25% 10% 1	220
	21st to end	Day	28% 29% 29% 10% 4	289
February	1st to 10th	Day	31% 29% 30% 9% 1	330
	11th to 20th	Day	30% 29% 31% 9% 1	486
	21st to end	Day	27% 26% 34% 12% 2	446
March	1st to 10th	Day	29% 24% 32% 12% 3	508
	11th to 20th	Day	26% 28% 30% 12% 3 1	500
	21st to end	Day	29% 28% 25% 13% 5% 1	550
April	1st to 10th	Day	32% 28% 22% 13% 5% 1	500
	11th to 20th	Day	28% 27% 24% 13% 7% 1	492
	21st to end	Day	30% 22% 29% 13% 5% 1	500
May	1st to 10th	Day	32% 17% 29% 13% 5% 3	503
	11th to 20th	Day	18% 18% 33% 23% 6% 2	527
	21st to end	Day	17% 12% 32% 25% 11% 3	573
June	1st to 10th	Day	15% 18% 32% 23% 10% 2	530
	11th to 20th	Day	16% 16% 31% 24% 12% 1	530
	21st to end	Day	15% 16% 34% 23% 10% 2	530
July	1st to 10th	Day	11% 12% 29% 30% 15% 3	525
	11th to 20th	Day	12% 6% 32% 33% 13% 3	524
	21st to end	Day	13% 8% 36% 29% 12% 3	576
August	1st to 10th	Day	11% 7% 30% 29% 17% 5%	526
	11th to 20th	Day	13% 9% 28% 29% 16% 5%	519
	21st to end	Day	12% 14% 28% 26% 16% 4	583
September	1st to 10th	Day	16% 9% 28% 23% 17% 7%	530
	11th to 20th	Day	12% 9% 25% 24% 18% 11%	530
	21st to end	Day	18% 11% 26% 26% 13% 5%	530
October	1st to 10th	Day	22% 13% 27% 19% 15% 4	530
	11th to 20th	Day	19% 20% 28% 24% 8% 2	530
	21st to end	Day	26% 17% 31% 19% 6%	477
November	1st to 10th	Day	26% 19% 24% 20% 11% 1	425
	11th to 20th	Day	25% 23% 29% 17% 4 1	430
	21st to end	Day	29% 25% 27% 17% 2	241
December	1st to 10th	Day	26% 25% 31% 14% 4	220
	11th to 20th	Day	32% 25% 32% 8% 2	220
	21st to end	Day	23% 27% 34% 12% 3	242
January	1st to 10th	Night	20% 26% 35% 16% 2	840
	11th to 20th	Night	25% 22% 33% 18% 2	840
	21st to end	Night	18% 23% 39% 18% 2	924
February	1st to 10th	Night	23% 23% 38% 15% 2	840
	11th to 20th	Night	23% 25% 36% 16%	823
	21st to end	Night	26% 23% 33% 16% 2	692
March	1st to 10th	Night	25% 22% 35% 15% 2	809
	11th to 20th	Night	24% 24% 33% 16% 2	800
	21st to end	Night	23% 24% 32% 17% 4	880
April	1st to 10th	Night	24% 25% 32% 17% 2	800
	11th to 20th	Night	24% 21% 32% 18% 6%	791
	21st to end	Night	22% 22% 31% 21% 5%	730
May	1st to 10th	Night	25% 17% 32% 20% 5%	545
	11th to 20th	Night	18% 16% 34% 26% 6% 1	394
	21st to end	Night	15% 9% 29% 37% 9% 1	433
June	1st to 10th	Night	18% 10% 32% 29% 10% 1	400
	11th to 20th	Night	17% 8% 30% 35% 10%	400
	21st to end	Night	13% 7% 33% 36% 11% 1	400
July	1st to 10th	Night	10% 5% 28% 41% 15% 1	390
	11th to 20th	Night	13% 5% 23% 42% 15% 1	388
	21st to end	Night	11% 5% 28% 42% 13%	438
August	1st to 10th	Night	12% 4 25% 39% 19% 1	427
	11th to 20th	Night	13% 6% 24% 37% 17% 4	755
	21st to end	Night	15% 8% 24% 35% 17% 1	880
September	1st to 10th	Night	13% 7% 28% 34% 16% 1	800
	11th to 20th	Night	14% 8% 26% 29% 19% 5%	800
	21st to end	Night	16% 8% 29% 32% 14% 2	800
October	1st to 10th	Night	21% 11% 25% 26% 15% 1	800
	11th to 20th	Night	18% 15% 31% 28% 8%	800
	21st to end	Night	26% 16% 30% 24% 4	880
November	1st to 10th	Night	21% 18% 29% 26% 7%	820
	11th to 20th	Night	20% 21% 31% 20% 6% 1	840
	21st to end	Night	21% 22% 29% 23% 4	840
December	1st to 10th	Night	23% 24% 34% 16% 3	840
	11th to 20th	Night	26% 20% 32% 19% 3	840
	21st to end	Night	27% 24% 30% 17% 2	924

Page generated at 2026-02-28 01:40:21. Version ac07

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