Canfield
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Canfield clear sky chart from 2005-11-06 to 2026-01-02.

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% 11% 4 9% 5% 5% 5% 4 5% 7% 30%	126884
	Night	16% 12% 4 9% 5% 4 4 3 5% 6% 31%	124449
Transparency	Day	51% 7% 11% 19% 10% 1	130503
	Night	52% 6% 11% 19% 11% 1	128899
Seeing	Day	22% 14% 28% 21% 11% 4	16073
	Night	22% 12% 27% 27% 11% 1	25881

By Month

Percentage Cloud Cover SE (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	15% 20% 8% 22% 5% 3 3 2 3 5% 13%	4065
	11th to 20th	Day	12% 23% 7% 16% 9% 7% 4 2 3 4 12%	4060
	21st to end	Day	21% 19% 8% 12% 7% 5% 4 2 4 4 13%	4466
February	1st to 10th	Day	18% 19% 4 12% 8% 4 3 2 3 4 22%	1800
	11th to 20th	Day	16% 14% 6% 14% 7% 4 5% 3 4 5% 20%	1763
	21st to end	Day	19% 15% 4 12% 6% 4 4 4 5% 5% 23%	1650
March	1st to 10th	Day	17% 12% 7% 11% 4 4 3 3 4 5% 29%	4923
	11th to 20th	Day	12% 10% 4 9% 5% 5% 5% 3 4 6% 37%	4980
	21st to end	Day	19% 12% 4 10% 5% 4 4 3 5% 6% 29%	5465
April	1st to 10th	Day	16% 14% 3 8% 5% 4 5% 3 4 8% 30%	2275
	11th to 20th	Day	18% 12% 3 7% 5% 4 4 4 5% 6% 33%	2475
	21st to end	Day	20% 11% 3 7% 5% 3 3 3 5% 6% 34%	2600
May	1st to 10th	Day	22% 9% 3 8% 5% 4 5% 4 6% 6% 28%	5862
	11th to 20th	Day	19% 9% 2 7% 5% 5% 5% 4 6% 8% 30%	5861
	21st to end	Day	19% 7% 2 6% 5% 5% 5% 4 6% 7% 33%	6702
June	1st to 10th	Day	16% 6% 2 6% 6% 5% 5% 4 7% 8% 34%	2800
	11th to 20th	Day	15% 6% 3 7% 5% 5% 5% 4 6% 9% 36%	2800
	21st to end	Day	12% 5% 2 6% 5% 5% 5% 5% 7% 10% 38%	2800
July	1st to 10th	Day	8% 6% 2 6% 5% 5% 5% 5% 6% 10% 41%	6052
	11th to 20th	Day	10% 6% 3 7% 5% 6% 6% 5% 8% 10% 35%	5900
	21st to end	Day	12% 6% 2 7% 5% 5% 5% 4 6% 8% 40%	6424
August	1st to 10th	Day	15% 8% 3 6% 6% 5% 6% 5% 6% 8% 32%	4234
	11th to 20th	Day	12% 7% 3 7% 5% 5% 5% 5% 8% 9% 34%	4174
	21st to end	Day	9% 5% 2 7% 5% 6% 5% 5% 8% 9% 39%	4522
September	1st to 10th	Day	14% 6% 2 5% 4 4 5% 3 5% 6% 45%	2354
	11th to 20th	Day	11% 5% 3 5% 4 4 5% 4 6% 8% 45%	2200
	21st to end	Day	19% 8% 3 7% 4 4 4 3 5% 7% 36%	2200
October	1st to 10th	Day	15% 6% 2 7% 5% 4 4 4 6% 7% 40%	2030
	11th to 20th	Day	18% 10% 3 8% 6% 5% 4 4 5% 6% 34%	2000
	21st to end	Day	22% 11% 3 7% 4 5% 4 3 4 7% 29%	2200
November	1st to 10th	Day	12% 8% 3 8% 5% 4 4 3 5% 7% 39%	1907
	11th to 20th	Day	16% 17% 4 8% 5% 4 5% 4 4 6% 28%	1791
	21st to end	Day	17% 16% 7% 12% 4 5% 4 4 5% 6% 22%	1680
December	1st to 10th	Day	20% 15% 7% 13% 6% 4 4 4 5% 4 19%	2680
	11th to 20th	Day	22% 19% 7% 10% 4 3 3 3 5% 5% 18%	3070
	21st to end	Day	24% 23% 7% 13% 5% 4 4 2 3 4 11%	4119
January	1st to 10th	Night	14% 18% 7% 25% 6% 4 3 3 3 4 13%	5903
	11th to 20th	Night	12% 19% 9% 17% 8% 6% 5% 3 3 4 13%	5900
	21st to end	Night	22% 17% 8% 13% 6% 4 5% 2 3 4 17%	6490
February	1st to 10th	Night	21% 13% 6% 11% 6% 6% 4 3 4 5% 22%	2600
	11th to 20th	Night	18% 14% 6% 13% 7% 6% 4 3 5% 4 22%	2520
	21st to end	Night	20% 14% 5% 11% 5% 5% 4 3 4 5% 24%	1980
March	1st to 10th	Night	22% 13% 5% 9% 4 3 3 2 3 5% 30%	4928
	11th to 20th	Night	14% 10% 4 7% 4 4 4 4 5% 7% 38%	4980
	21st to end	Night	18% 12% 4 8% 5% 4 4 3 4 5% 34%	5467
April	1st to 10th	Night	18% 14% 4 7% 5% 4 3 3 5% 6% 32%	2125
	11th to 20th	Night	16% 10% 3 8% 4 5% 4 4 6% 7% 33%	1891
	21st to end	Night	16% 10% 2 7% 4 4 4 3 6% 7% 37%	1800
May	1st to 10th	Night	26% 10% 3 8% 5% 5% 4 3 5% 6% 26%	4033
	11th to 20th	Night	17% 9% 3 7% 4 4 3 3 5% 8% 37%	4032
	21st to end	Night	17% 7% 2 5% 4 4 4 3 6% 9% 38%	4147
June	1st to 10th	Night	9% 6% 3 7% 6% 6% 5% 4 6% 6% 43%	1600
	11th to 20th	Night	11% 6% 3 7% 5% 5% 4 4 6% 8% 42%	1600
	21st to end	Night	11% 4 2 7% 5% 5% 5% 5% 7% 9% 42%	1600
July	1st to 10th	Night	10% 7% 2 7% 5% 5% 4 4 5% 8% 43%	3873
	11th to 20th	Night	10% 6% 2 6% 4 5% 5% 4 7% 9% 40%	4057
	21st to end	Night	8% 6% 2 6% 5% 4 5% 3 7% 8% 46%	4427
August	1st to 10th	Night	13% 7% 4 7% 4 5% 5% 4 5% 7% 39%	2915
	11th to 20th	Night	13% 7% 3 7% 4 4 4 3 5% 6% 44%	2875
	21st to end	Night	8% 4 2 7% 5% 5% 5% 5% 7% 8% 45%	3341
September	1st to 10th	Night	12% 5% 2 6% 3 3 4 3 5% 7% 50%	2043
	11th to 20th	Night	10% 4 2 4 3 4 4 3 5% 8% 53%	2200
	21st to end	Night	18% 7% 3 6% 4 4 4 4 5% 7% 39%	2200
October	1st to 10th	Night	15% 5% 2 5% 5% 4 4 3 5% 6% 46%	2370
	11th to 20th	Night	17% 7% 3 7% 5% 5% 5% 4 5% 7% 37%	2400
	21st to end	Night	23% 8% 2 6% 3 4 4 3 4 5% 36%	2640
November	1st to 10th	Night	14% 9% 2 5% 4 4 4 4 5% 7% 43%	2608
	11th to 20th	Night	16% 15% 4 8% 5% 4 5% 3 5% 5% 31%	2825
	21st to end	Night	20% 16% 4 8% 5% 4 4 3 4 6% 26%	2940
December	1st to 10th	Night	16% 18% 7% 14% 6% 5% 4 3 4 5% 17%	4720
	11th to 20th	Night	19% 21% 7% 11% 5% 4 3 3 4 5% 19%	5345
	21st to end	Night	23% 20% 7% 12% 5% 4 4 3 4 4 14%	7074

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	74% 6% 7% 9% 4	4066
	11th to 20th	Day	76% 4 8% 9% 3	4060
	21st to end	Day	76% 4 7% 9% 4	4466
February	1st to 10th	Day	68% 4 9% 13% 6%	1800
	11th to 20th	Day	66% 7% 8% 13% 7%	1772
	21st to end	Day	61% 7% 10% 14% 7% 1	1650
March	1st to 10th	Day	56% 6% 11% 20% 7%	4923
	11th to 20th	Day	47% 7% 13% 24% 8% 1	4980
	21st to end	Day	55% 5% 9% 18% 12% 1	5465
April	1st to 10th	Day	53% 7% 11% 17% 12% 1	2275
	11th to 20th	Day	51% 7% 11% 17% 12% 2	2475
	21st to end	Day	51% 6% 11% 20% 10% 2	2600
May	1st to 10th	Day	54% 8% 10% 16% 9% 4	5897
	11th to 20th	Day	49% 8% 11% 20% 10% 1	5865
	21st to end	Day	45% 8% 13% 20% 11% 3	6717
June	1st to 10th	Day	45% 8% 13% 22% 11% 1	2800
	11th to 20th	Day	45% 8% 13% 21% 13% 1	2800
	21st to end	Day	39% 9% 14% 24% 13% 1	2800
July	1st to 10th	Day	37% 6% 14% 26% 15% 2	5987
	11th to 20th	Day	41% 8% 13% 24% 13%	5831
	21st to end	Day	39% 7% 11% 23% 19% 1	6240
August	1st to 10th	Day	47% 8% 14% 21% 10%	4221
	11th to 20th	Day	41% 9% 13% 28% 8% 1	4213
	21st to end	Day	38% 9% 13% 27% 11% 2	4522
September	1st to 10th	Day	39% 7% 12% 22% 17% 3	2354
	11th to 20th	Day	35% 8% 13% 25% 17% 1	2200
	21st to end	Day	48% 7% 12% 21% 12% 1	2200
October	1st to 10th	Day	32% 6% 12% 29% 20% 1	3303
	11th to 20th	Day	46% 6% 11% 19% 14% 4	3240
	21st to end	Day	41% 5% 12% 26% 15% 1	3538
November	1st to 10th	Day	43% 6% 12% 21% 15% 2	1907
	11th to 20th	Day	56% 6% 10% 17% 8% 2	1791
	21st to end	Day	62% 6% 11% 15% 5% 1	1680
December	1st to 10th	Day	68% 5% 12% 12% 3	2680
	11th to 20th	Day	68% 5% 10% 13% 4	3066
	21st to end	Day	78% 4 8% 8% 2	4119
January	1st to 10th	Night	75% 5% 7% 9% 3	5903
	11th to 20th	Night	75% 5% 9% 8% 3	5900
	21st to end	Night	73% 4 7% 10% 4 1	6490
February	1st to 10th	Night	65% 5% 10% 15% 5%	2600
	11th to 20th	Night	64% 5% 10% 15% 6%	2522
	21st to end	Night	63% 6% 8% 14% 8% 1	1980
March	1st to 10th	Night	58% 4 11% 19% 8%	4928
	11th to 20th	Night	44% 7% 15% 24% 8% 2	4980
	21st to end	Night	51% 6% 11% 17% 14% 1	5467
April	1st to 10th	Night	53% 6% 11% 17% 12% 2	2125
	11th to 20th	Night	48% 7% 12% 17% 14% 2	1891
	21st to end	Night	44% 7% 13% 19% 15% 2	1800
May	1st to 10th	Night	58% 6% 9% 14% 9% 4	4060
	11th to 20th	Night	45% 8% 10% 24% 12% 1	4033
	21st to end	Night	41% 8% 14% 24% 11% 2	4154
June	1st to 10th	Night	37% 9% 13% 23% 16% 2	1600
	11th to 20th	Night	38% 7% 14% 23% 16% 2	1600
	21st to end	Night	37% 10% 13% 23% 17% 1	1600
July	1st to 10th	Night	40% 6% 11% 23% 19% 1	3830
	11th to 20th	Night	37% 9% 15% 26% 12% 1	4006
	21st to end	Night	34% 7% 12% 19% 26% 2	4297
August	1st to 10th	Night	43% 8% 12% 23% 13% 1	2904
	11th to 20th	Night	39% 7% 11% 28% 14% 1	2902
	21st to end	Night	34% 8% 13% 30% 13% 2	3341
September	1st to 10th	Night	33% 7% 12% 25% 19% 4	2043
	11th to 20th	Night	29% 7% 15% 26% 21% 2	2200
	21st to end	Night	44% 6% 13% 20% 17% 1	2200
October	1st to 10th	Night	33% 5% 10% 27% 24% 1	3877
	11th to 20th	Night	39% 6% 12% 23% 14% 6%	3899
	21st to end	Night	37% 5% 10% 29% 17% 2	4252
November	1st to 10th	Night	40% 7% 12% 23% 15% 3	2608
	11th to 20th	Night	55% 6% 10% 18% 8% 3	2825
	21st to end	Night	60% 6% 11% 17% 5% 1	2940
December	1st to 10th	Night	69% 6% 12% 11% 3	4720
	11th to 20th	Night	68% 5% 10% 14% 2	5348
	21st to end	Night	72% 7% 9% 11% 2	7074

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	33% 24% 30% 10% 4	303
	11th to 20th	Day	31% 25% 32% 8% 3	300
	21st to end	Day	30% 27% 32% 9% 3 1	330
February	1st to 10th	Day	32% 23% 36% 8% 1	300
	11th to 20th	Day	32% 26% 31% 9% 2	300
	21st to end	Day	34% 23% 35% 8%	249
March	1st to 10th	Day	27% 19% 35% 15% 4	488
	11th to 20th	Day	30% 17% 33% 14% 5% 1	500
	21st to end	Day	33% 19% 27% 16% 4 1	550
April	1st to 10th	Day	26% 22% 29% 15% 7% 1	500
	11th to 20th	Day	29% 16% 27% 16% 9% 3	492
	21st to end	Day	26% 17% 32% 18% 5% 2	500
May	1st to 10th	Day	27% 19% 25% 18% 8% 3	503
	11th to 20th	Day	23% 12% 30% 24% 8% 3	527
	21st to end	Day	17% 9% 27% 25% 16% 5%	573
June	1st to 10th	Day	16% 10% 33% 27% 11% 4	530
	11th to 20th	Day	18% 10% 27% 26% 15% 4	530
	21st to end	Day	13% 10% 32% 25% 15% 5%	530
July	1st to 10th	Day	12% 6% 20% 29% 22% 11%	525
	11th to 20th	Day	11% 8% 25% 30% 18% 8%	524
	21st to end	Day	13% 4 26% 30% 19% 9%	576
August	1st to 10th	Day	12% 6% 22% 31% 19% 10%	526
	11th to 20th	Day	14% 5% 24% 27% 20% 11%	519
	21st to end	Day	10% 5% 25% 29% 20% 11%	583
September	1st to 10th	Day	15% 9% 20% 25% 21% 10%	530
	11th to 20th	Day	9% 3 19% 32% 25% 12%	530
	21st to end	Day	24% 10% 23% 22% 13% 6%	530
October	1st to 10th	Day	13% 11% 25% 26% 20% 5%	530
	11th to 20th	Day	20% 15% 35% 18% 8% 2	530
	21st to end	Day	29% 17% 30% 19% 5%	583
November	1st to 10th	Day	19% 22% 33% 15% 9% 2	385
	11th to 20th	Day	33% 19% 26% 16% 5% 1	278
	21st to end	Day	29% 21% 39% 11%	220
December	1st to 10th	Day	32% 25% 30% 10% 3 1	220
	11th to 20th	Day	33% 20% 33% 11% 4	220
	21st to end	Day	39% 20% 26% 13% 2	259
January	1st to 10th	Night	27% 21% 32% 16% 3	805
	11th to 20th	Night	30% 19% 32% 15% 4	800
	21st to end	Night	28% 19% 30% 20% 4	880
February	1st to 10th	Night	29% 17% 30% 21% 2	800
	11th to 20th	Night	28% 16% 35% 19% 2	783
	21st to end	Night	29% 16% 34% 18% 3	660
March	1st to 10th	Night	25% 16% 33% 24% 3	800
	11th to 20th	Night	24% 17% 30% 23% 5% 1	800
	21st to end	Night	25% 15% 32% 23% 5% 1	880
April	1st to 10th	Night	26% 15% 30% 24% 5%	800
	11th to 20th	Night	23% 13% 33% 22% 8% 1	707
	21st to end	Night	20% 10% 35% 29% 7%	600
May	1st to 10th	Night	23% 9% 26% 31% 10% 1	600
	11th to 20th	Night	20% 7% 25% 35% 13% 1	591
	21st to end	Night	12% 4 24% 38% 19% 3	531
June	1st to 10th	Night	11% 4 27% 44% 14% 1	400
	11th to 20th	Night	11% 6% 25% 45% 13% 1	400
	21st to end	Night	11% 4 26% 39% 21% 1	400
July	1st to 10th	Night	7% 3 17% 42% 25% 5%	504
	11th to 20th	Night	10% 3 20% 37% 26% 4	582
	21st to end	Night	12% 2 15% 41% 28% 2	657
August	1st to 10th	Night	11% 3 14% 44% 27% 2	597
	11th to 20th	Night	15% 3 12% 37% 29% 5%	594
	21st to end	Night	13% 2 20% 32% 28% 5%	726
September	1st to 10th	Night	14% 5% 18% 34% 25% 5%	800
	11th to 20th	Night	12% 3 14% 37% 31% 5%	800
	21st to end	Night	20% 8% 21% 28% 19% 4	800
October	1st to 10th	Night	17% 7% 24% 29% 21% 3	800
	11th to 20th	Night	20% 12% 31% 27% 10% 1	800
	21st to end	Night	29% 10% 28% 27% 6%	880
November	1st to 10th	Night	20% 11% 30% 28% 10%	820
	11th to 20th	Night	27% 17% 29% 20% 6% 1	840
	21st to end	Night	30% 16% 29% 20% 4	840
December	1st to 10th	Night	31% 19% 28% 18% 4	840
	11th to 20th	Night	28% 20% 30% 19% 3	840
	21st to end	Night	30% 17% 31% 19% 2	924

Page generated at 2025-12-30 01:14:11. Version ac07

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