Rutherford County Astronomical Society - Site 1
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rutherford County Astronomical Society - Site 1 clear sky chart from 2005-11-06 to 2026-01-17.

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% 5% 2 5% 4 4 4 4 6% 8% 44%	127426
	Night	15% 5% 2 5% 4 4 4 4 5% 7% 44%	124277
Transparency	Day	24% 39% 8% 13% 12% 4	131111
	Night	25% 39% 6% 12% 14% 5%	128661
Seeing	Day	17% 8% 21% 25% 19% 10%	16724
	Night	17% 5% 22% 32% 21% 3	26824

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	14% 6% 1 3 2 2 2 2 4 5% 58%	4146
	11th to 20th	Day	12% 6% 2 4 3 2 2 2 3 3 62%	4114
	21st to end	Day	19% 4 2 5% 3 3 3 3 4 5% 48%	4466
February	1st to 10th	Day	15% 6% 2 4 4 4 3 4 5% 7% 44%	1845
	11th to 20th	Day	21% 7% 2 4 3 3 3 3 5% 5% 44%	1948
	21st to end	Day	18% 6% 3 5% 5% 3 4 3 5% 6% 42%	1650
March	1st to 10th	Day	20% 6% 2 5% 4 4 4 3 5% 5% 43%	4925
	11th to 20th	Day	12% 5% 2 4 3 3 3 3 4 6% 55%	4980
	21st to end	Day	19% 6% 2 4 3 3 3 3 5% 5% 48%	5465
April	1st to 10th	Day	13% 4 1 5% 4 4 4 3 6% 8% 48%	2200
	11th to 20th	Day	14% 5% 2 4 4 4 4 4 6% 7% 48%	2359
	21st to end	Day	14% 5% 2 5% 4 4 5% 3 5% 7% 46%	2600
May	1st to 10th	Day	11% 7% 3 7% 5% 5% 6% 5% 7% 9% 36%	5862
	11th to 20th	Day	19% 8% 2 7% 5% 5% 4 4 6% 8% 31%	5861
	21st to end	Day	13% 5% 2 6% 4 4 5% 4 6% 8% 41%	6433
June	1st to 10th	Day	10% 5% 2 7% 4 5% 6% 6% 9% 11% 35%	2600
	11th to 20th	Day	7% 5% 2 6% 6% 5% 6% 5% 8% 12% 39%	2600
	21st to end	Day	7% 4 2 6% 5% 7% 6% 6% 8% 10% 40%	2600
July	1st to 10th	Day	8% 5% 2 7% 5% 6% 6% 6% 7% 10% 38%	5900
	11th to 20th	Day	7% 5% 2 7% 6% 6% 6% 6% 9% 12% 35%	5900
	21st to end	Day	10% 6% 2 8% 6% 7% 8% 6% 8% 11% 28%	6424
August	1st to 10th	Day	18% 7% 3 7% 5% 5% 6% 5% 7% 10% 28%	4234
	11th to 20th	Day	9% 5% 2 6% 5% 5% 6% 5% 8% 11% 36%	4174
	21st to end	Day	7% 4 2 4 4 4 4 3 6% 9% 52%	4357
September	1st to 10th	Day	9% 5% 2 7% 5% 5% 5% 5% 6% 10% 43%	2200
	11th to 20th	Day	15% 6% 2 6% 5% 4 5% 3 5% 8% 41%	2200
	21st to end	Day	17% 6% 2 6% 4 4 4 4 5% 7% 41%	2200
October	1st to 10th	Day	15% 4 2 4 2 2 3 2 4 6% 55%	2130
	11th to 20th	Day	13% 4 2 4 2 2 2 2 3 4 61%	2000
	21st to end	Day	14% 5% 2 4 2 3 3 3 3 5% 58%	2200
November	1st to 10th	Day	14% 4 1 5% 3 3 3 2 4 6% 55%	2025
	11th to 20th	Day	13% 5% 2 4 3 2 3 3 5% 6% 54%	1890
	21st to end	Day	16% 5% 2 3 3 2 3 4 5% 6% 52%	1890
December	1st to 10th	Day	16% 5% 2 4 2 3 3 3 4 6% 52%	3020
	11th to 20th	Day	20% 5% 2 5% 3 4 4 3 5% 6% 45%	3463
	21st to end	Day	23% 4 2 4 2 2 3 2 4 6% 47%	4565
January	1st to 10th	Night	14% 3 1 3 3 3 3 3 4 4 59%	6019
	11th to 20th	Night	12% 5% 2 5% 3 3 3 3 4 4 57%	5979
	21st to end	Night	19% 6% 2 4 3 3 3 3 4 6% 48%	6490
February	1st to 10th	Night	16% 5% 2 5% 3 3 4 3 5% 5% 48%	2550
	11th to 20th	Night	21% 6% 2 4 4 3 4 3 5% 4 44%	2338
	21st to end	Night	16% 6% 2 6% 4 3 4 3 5% 6% 44%	1980
March	1st to 10th	Night	19% 5% 2 5% 4 4 4 3 4 6% 44%	4927
	11th to 20th	Night	10% 4 2 3 3 3 4 3 5% 8% 55%	4980
	21st to end	Night	17% 4 2 4 4 4 4 3 5% 6% 47%	5467
April	1st to 10th	Night	14% 5% 2 5% 4 3 4 3 6% 7% 49%	2200
	11th to 20th	Night	13% 5% 2 5% 4 3 3 3 6% 7% 50%	2005
	21st to end	Night	12% 5% 2 5% 4 4 4 4 4 6% 49%	1800
May	1st to 10th	Night	14% 6% 2 7% 5% 4 4 4 7% 9% 37%	4033
	11th to 20th	Night	21% 7% 3 7% 5% 5% 5% 4 6% 9% 31%	4032
	21st to end	Night	14% 6% 3 6% 4 4 5% 4 6% 8% 40%	4421
June	1st to 10th	Night	10% 6% 2 7% 6% 5% 5% 6% 7% 13% 32%	1800
	11th to 20th	Night	10% 7% 2 5% 5% 4 6% 5% 7% 11% 37%	1800
	21st to end	Night	8% 6% 2 5% 7% 5% 6% 5% 7% 12% 37%	1800
July	1st to 10th	Night	10% 6% 3 7% 6% 7% 7% 6% 8% 9% 30%	4058
	11th to 20th	Night	11% 5% 3 8% 6% 6% 6% 6% 9% 10% 29%	4057
	21st to end	Night	13% 8% 3 10% 6% 6% 6% 5% 8% 10% 24%	4427
August	1st to 10th	Night	17% 8% 3 8% 6% 5% 4 5% 7% 9% 26%	2915
	11th to 20th	Night	15% 6% 3 8% 4 6% 6% 5% 8% 8% 30%	2875
	21st to end	Night	7% 5% 3 6% 5% 5% 5% 4 7% 8% 44%	3502
September	1st to 10th	Night	11% 6% 2 6% 6% 5% 5% 4 7% 8% 40%	2200
	11th to 20th	Night	16% 5% 3 8% 6% 5% 5% 4 5% 7% 35%	2200
	21st to end	Night	18% 7% 2 6% 4 4 4 3 5% 6% 41%	2200
October	1st to 10th	Night	17% 5% 1 4 3 4 3 3 5% 6% 49%	2270
	11th to 20th	Night	14% 6% 2 4 3 3 3 2 4 6% 53%	2400
	21st to end	Night	15% 3 2 4 2 3 3 2 4 4 58%	2640
November	1st to 10th	Night	15% 4 2 5% 3 3 3 3 3 5% 54%	2487
	11th to 20th	Night	14% 5% 2 4 3 3 3 3 4 6% 54%	2730
	21st to end	Night	15% 4 2 4 3 3 4 3 5% 7% 50%	2730
December	1st to 10th	Night	16% 6% 2 4 3 3 3 2 4 5% 53%	4380
	11th to 20th	Night	22% 6% 2 5% 3 3 4 2 4 5% 44%	4952
	21st to end	Night	21% 4 2 4 3 3 3 3 4 6% 47%	6633

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	24% 25% 3 14% 27% 8%	4147
	11th to 20th	Day	20% 25% 3 10% 33% 9%	4114
	21st to end	Day	29% 28% 2 14% 19% 7%	4466
February	1st to 10th	Day	15% 62% 4 10% 8% 2	1845
	11th to 20th	Day	19% 61% 3 7% 8% 2	1958
	21st to end	Day	17% 63% 2 4 11% 2	1650
March	1st to 10th	Day	36% 29% 4 9% 11% 11%	4925
	11th to 20th	Day	20% 29% 4 9% 20% 18%	4980
	21st to end	Day	28% 29% 3 18% 17% 5%	5465
April	1st to 10th	Day	15% 62% 5% 7% 9% 2	2200
	11th to 20th	Day	16% 63% 4 9% 6% 3	2359
	21st to end	Day	15% 62% 5% 11% 7% 1	2600
May	1st to 10th	Day	33% 32% 12% 15% 7% 1	5897
	11th to 20th	Day	39% 31% 9% 15% 7%	5865
	21st to end	Day	29% 30% 10% 15% 14% 3	6447
June	1st to 10th	Day	15% 63% 8% 9% 4 1	2600
	11th to 20th	Day	12% 64% 10% 9% 5%	2600
	21st to end	Day	14% 63% 8% 10% 4	2600
July	1st to 10th	Day	27% 32% 13% 19% 8%	5835
	11th to 20th	Day	28% 34% 25% 13% 1	5831
	21st to end	Day	37% 32% 11% 15% 4 1	6240
August	1st to 10th	Day	35% 38% 11% 13% 2	4221
	11th to 20th	Day	21% 41% 17% 12% 8% 2	4213
	21st to end	Day	13% 37% 9% 25% 15% 1	4357
September	1st to 10th	Day	15% 59% 6% 10% 9% 1	2200
	11th to 20th	Day	18% 58% 7% 8% 7% 1	2200
	21st to end	Day	21% 58% 7% 8% 6% 1	2200
October	1st to 10th	Day	17% 36% 5% 13% 21% 7%	3468
	11th to 20th	Day	9% 35% 2 10% 20% 22%	3240
	21st to end	Day	18% 35% 2 17% 14% 14%	3538
November	1st to 10th	Day	20% 53% 3 9% 11% 4	2025
	11th to 20th	Day	16% 54% 3 10% 13% 4	1890
	21st to end	Day	16% 54% 4 12% 12% 3	1890
December	1st to 10th	Day	22% 35% 4 12% 20% 8%	3020
	11th to 20th	Day	31% 32% 5% 9% 16% 6%	3460
	21st to end	Day	30% 26% 6% 23% 14% 2	4565
January	1st to 10th	Night	21% 26% 3 13% 29% 8%	6019
	11th to 20th	Night	22% 26% 3 12% 31% 7%	5979
	21st to end	Night	27% 28% 3 13% 20% 8%	6490
February	1st to 10th	Night	15% 62% 4 10% 8% 1	2550
	11th to 20th	Night	20% 60% 4 6% 8% 2	2339
	21st to end	Night	15% 62% 3 7% 9% 4	1980
March	1st to 10th	Night	32% 30% 5% 8% 19% 6%	4927
	11th to 20th	Night	16% 29% 4 10% 23% 18%	4980
	21st to end	Night	27% 29% 4 17% 16% 7%	5467
April	1st to 10th	Night	15% 62% 4 7% 9% 2	2200
	11th to 20th	Night	15% 63% 4 9% 7% 3	2005
	21st to end	Night	14% 62% 5% 10% 7% 1	1800
May	1st to 10th	Night	32% 31% 11% 17% 8% 1	4060
	11th to 20th	Night	36% 32% 10% 14% 7%	4033
	21st to end	Night	30% 31% 8% 19% 11% 2	4429
June	1st to 10th	Night	17% 65% 6% 8% 4 1	1800
	11th to 20th	Night	14% 65% 8% 8% 5%	1800
	21st to end	Night	13% 64% 9% 7% 6%	1800
July	1st to 10th	Night	35% 32% 13% 15% 5%	4015
	11th to 20th	Night	35% 34% 19% 11% 1	4006
	21st to end	Night	41% 32% 11% 12% 4	4297
August	1st to 10th	Night	38% 40% 12% 9% 1	2904
	11th to 20th	Night	32% 41% 13% 9% 5%	2902
	21st to end	Night	18% 39% 8% 21% 12% 2	3502
September	1st to 10th	Night	15% 59% 8% 9% 8% 1	2200
	11th to 20th	Night	20% 59% 7% 7% 6% 1	2200
	21st to end	Night	21% 58% 7% 9% 4	2200
October	1st to 10th	Night	23% 37% 6% 11% 16% 6%	3712
	11th to 20th	Night	10% 35% 3 12% 20% 19%	3899
	21st to end	Night	19% 35% 2 14% 18% 12%	4252
November	1st to 10th	Night	21% 53% 3 10% 9% 4	2487
	11th to 20th	Night	15% 54% 3 8% 13% 6%	2730
	21st to end	Night	16% 54% 3 11% 13% 2	2730
December	1st to 10th	Night	23% 34% 3 15% 19% 6%	4380
	11th to 20th	Night	32% 31% 5% 10% 14% 7%	4954
	21st to end	Night	30% 26% 8% 18% 17% 1	6633

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	25% 15% 32% 22% 6%	330
	11th to 20th	Day	25% 19% 28% 20% 7% 1	318
	21st to end	Day	22% 15% 38% 20% 5%	330
February	1st to 10th	Day	20% 15% 36% 22% 6% 1	300
	11th to 20th	Day	37% 19% 30% 11% 3	300
	21st to end	Day	25% 22% 33% 15% 5%	249
March	1st to 10th	Day	22% 13% 30% 24% 9% 2	490
	11th to 20th	Day	20% 13% 34% 27% 5% 1	500
	21st to end	Day	23% 15% 28% 25% 8% 1	550
April	1st to 10th	Day	19% 16% 27% 25% 11% 3	500
	11th to 20th	Day	16% 14% 28% 24% 15% 4	492
	21st to end	Day	18% 9% 25% 27% 15% 7%	500
May	1st to 10th	Day	14% 11% 29% 27% 14% 6%	503
	11th to 20th	Day	18% 6% 17% 29% 20% 10%	527
	21st to end	Day	18% 5% 16% 24% 23% 15%	573
June	1st to 10th	Day	12% 3 19% 29% 22% 14%	530
	11th to 20th	Day	10% 2 16% 27% 25% 20%	530
	21st to end	Day	10% 2 13% 29% 27% 19%	530
July	1st to 10th	Day	9% 2 9% 24% 30% 26%	525
	11th to 20th	Day	7% 1 8% 24% 32% 28%	524
	21st to end	Day	8% 1 9% 26% 31% 25%	576
August	1st to 10th	Day	19% 2 13% 23% 25% 18%	526
	11th to 20th	Day	13% 2 11% 24% 32% 18%	519
	21st to end	Day	12% 2 10% 23% 28% 25%	583
September	1st to 10th	Day	10% 2 13% 24% 31% 20%	530
	11th to 20th	Day	19% 2 11% 18% 31% 19%	530
	21st to end	Day	22% 3 19% 23% 25% 8%	530
October	1st to 10th	Day	17% 5% 15% 26% 25% 12%	530
	11th to 20th	Day	14% 7% 18% 31% 24% 6%	530
	21st to end	Day	21% 7% 19% 29% 19% 6%	583
November	1st to 10th	Day	21% 7% 24% 28% 15% 4	503
	11th to 20th	Day	17% 12% 32% 27% 11% 2	330
	21st to end	Day	12% 13% 29% 28% 15% 3	330
December	1st to 10th	Day	27% 10% 32% 25% 6%	330
	11th to 20th	Day	22% 12% 32% 24% 10% 1	330
	21st to end	Day	26% 13% 29% 21% 10% 1	363
January	1st to 10th	Night	19% 10% 31% 33% 7%	840
	11th to 20th	Night	19% 8% 35% 32% 5%	825
	21st to end	Night	19% 8% 38% 34% 3	880
February	1st to 10th	Night	17% 9% 34% 37% 3	800
	11th to 20th	Night	22% 11% 37% 28% 2	783
	21st to end	Night	17% 10% 38% 32% 3	660
March	1st to 10th	Night	18% 9% 30% 38% 6%	800
	11th to 20th	Night	18% 9% 34% 31% 8% 1	800
	21st to end	Night	19% 8% 32% 33% 7%	880
April	1st to 10th	Night	16% 12% 30% 32% 10%	800
	11th to 20th	Night	14% 12% 25% 33% 15% 1	761
	21st to end	Night	15% 5% 23% 38% 19% 1	600
May	1st to 10th	Night	14% 3 26% 35% 21% 1	600
	11th to 20th	Night	18% 4 19% 31% 25% 2	591
	21st to end	Night	17% 2 10% 30% 36% 5%	650
June	1st to 10th	Night	12% 2 10% 35% 36% 5%	600
	11th to 20th	Night	12% 3 10% 30% 34% 12%	600
	21st to end	Night	9% 2 8% 27% 48% 7%	600
July	1st to 10th	Night	12% 2 7% 22% 46% 11%	585
	11th to 20th	Night	9% 7% 20% 48% 15%	582
	21st to end	Night	8% 2 5% 26% 47% 12%	657
August	1st to 10th	Night	16% 3 8% 25% 39% 9%	597
	11th to 20th	Night	15% 3 5% 26% 40% 11%	594
	21st to end	Night	12% 2 8% 24% 45% 10%	755
September	1st to 10th	Night	12% 2 7% 28% 42% 9%	800
	11th to 20th	Night	17% 2 11% 25% 38% 7%	800
	21st to end	Night	21% 3 14% 31% 29% 2	800
October	1st to 10th	Night	18% 3 16% 29% 28% 7%	800
	11th to 20th	Night	17% 5% 22% 33% 21% 2	800
	21st to end	Night	16% 5% 22% 36% 20% 2	880
November	1st to 10th	Night	17% 5% 19% 39% 18% 2	820
	11th to 20th	Night	15% 7% 26% 40% 12% 1	840
	21st to end	Night	16% 6% 26% 38% 14% 1	840
December	1st to 10th	Night	23% 5% 28% 37% 7%	840
	11th to 20th	Night	20% 5% 27% 38% 10% 1	840
	21st to end	Night	26% 6% 27% 34% 7%	924

Page generated at 2026-01-14 01:14:32. Version ac07

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