Franklinton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Franklinton clear sky chart from 2005-11-06 to 2025-12-03.

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	11% 6% 2 7% 5% 5% 5% 4 6% 8% 40%	125723
	Night	13% 6% 2 6% 4 4 4 4 5% 8% 44%	125003
Transparency	Day	40% 6% 12% 18% 17% 7%	129408
	Night	37% 5% 12% 19% 18% 9%	129393
Seeing	Day	15% 8% 20% 25% 22% 10%	16204
	Night	15% 7% 21% 29% 22% 6%	25842

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	17% 6% 3 6% 4 4 3 3 5% 6% 44%	4077
	11th to 20th	Day	12% 7% 3 6% 4 3 4 3 4 4 51%	4080
	21st to end	Day	22% 9% 3 7% 4 3 4 3 4 5% 36%	4899
February	1st to 10th	Day	17% 10% 4 7% 5% 4 4 3 4 5% 39%	2000
	11th to 20th	Day	18% 7% 2 5% 4 3 5% 3 5% 7% 41%	1948
	21st to end	Day	18% 8% 3 8% 4 4 4 4 5% 6% 37%	1650
March	1st to 10th	Day	19% 9% 3 7% 4 4 4 4 5% 7% 35%	4699
	11th to 20th	Day	14% 5% 3 6% 4 4 4 4 5% 7% 44%	4980
	21st to end	Day	14% 8% 3 8% 5% 5% 5% 4 5% 5% 40%	5734
April	1st to 10th	Day	12% 8% 2 6% 5% 5% 5% 4 7% 6% 40%	2400
	11th to 20th	Day	14% 6% 3 6% 5% 5% 5% 3 5% 6% 41%	2374
	21st to end	Day	9% 5% 2 6% 5% 5% 5% 4 6% 7% 45%	2400
May	1st to 10th	Day	17% 7% 2 7% 5% 5% 6% 4 6% 8% 32%	5405
	11th to 20th	Day	10% 5% 2 6% 4 5% 5% 5% 7% 10% 41%	5404
	21st to end	Day	6% 4 2 7% 5% 5% 5% 5% 8% 11% 41%	5932
June	1st to 10th	Day	9% 7% 3 8% 7% 7% 6% 6% 7% 9% 31%	2449
	11th to 20th	Day	5% 6% 2 9% 7% 6% 7% 6% 9% 11% 32%	2660
	21st to end	Day	7% 7% 3 8% 8% 8% 8% 7% 9% 10% 26%	2600
July	1st to 10th	Day	5% 6% 2 8% 7% 8% 8% 7% 9% 12% 29%	5900
	11th to 20th	Day	6% 4 2 7% 7% 8% 8% 6% 9% 10% 32%	5900
	21st to end	Day	7% 6% 3 8% 7% 7% 8% 6% 9% 12% 28%	5922
August	1st to 10th	Day	3 3 1 5% 5% 4 5% 4 6% 9% 54%	3905
	11th to 20th	Day	6% 4 2 7% 5% 6% 6% 6% 6% 11% 41%	3849
	21st to end	Day	10% 6% 3 8% 6% 6% 7% 5% 6% 8% 35%	4312
September	1st to 10th	Day	11% 7% 3 7% 6% 7% 7% 5% 6% 8% 35%	2400
	11th to 20th	Day	11% 6% 3 6% 5% 5% 6% 5% 7% 8% 39%	2340
	21st to end	Day	8% 5% 2 5% 4 4 4 4 6% 6% 50%	2200
October	1st to 10th	Day	7% 5% 2 5% 4 4 4 4 5% 6% 55%	2108
	11th to 20th	Day	6% 4 2 5% 5% 3 4 3 5% 7% 56%	2000
	21st to end	Day	9% 4 2 4 4 4 3 3 5% 5% 56%	2200
November	1st to 10th	Day	9% 6% 2 5% 4 4 4 4 4 6% 52%	2058
	11th to 20th	Day	11% 5% 2 5% 3 3 3 3 6% 6% 54%	1977
	21st to end	Day	14% 6% 2 6% 3 4 4 4 6% 6% 45%	1890
December	1st to 10th	Day	18% 8% 3 6% 3 5% 4 4 4 5% 42%	2948
	11th to 20th	Day	11% 7% 2 6% 5% 4 4 3 6% 6% 45%	3373
	21st to end	Day	17% 8% 2 5% 4 3 4 3 5% 6% 44%	4750
January	1st to 10th	Night	19% 6% 2 5% 3 3 2 3 4 5% 48%	5888
	11th to 20th	Night	19% 8% 3 5% 3 3 2 2 3 5% 48%	5900
	21st to end	Night	24% 9% 2 5% 3 3 4 3 4 7% 37%	6053
February	1st to 10th	Night	18% 8% 3 5% 4 4 4 2 5% 6% 41%	2400
	11th to 20th	Night	21% 9% 2 6% 4 3 3 3 4 5% 40%	2338
	21st to end	Night	20% 8% 3 6% 4 3 3 3 5% 6% 37%	1980
March	1st to 10th	Night	19% 10% 3 6% 4 4 3 3 5% 6% 37%	5196
	11th to 20th	Night	15% 6% 2 5% 4 4 4 3 5% 5% 47%	4980
	21st to end	Night	17% 7% 2 6% 3 4 4 3 4 5% 44%	5193
April	1st to 10th	Night	15% 8% 2 6% 4 4 3 3 5% 7% 43%	2000
	11th to 20th	Night	14% 7% 2 5% 4 4 4 3 4 6% 47%	1975
	21st to end	Night	9% 4 2 5% 3 3 3 3 5% 6% 56%	2000
May	1st to 10th	Night	17% 8% 3 7% 4 4 4 3 5% 7% 38%	4490
	11th to 20th	Night	12% 7% 2 7% 4 4 4 4 6% 8% 42%	4489
	21st to end	Night	8% 5% 2 6% 4 4 5% 5% 8% 12% 41%	4922
June	1st to 10th	Night	7% 7% 3 7% 5% 4 5% 5% 7% 11% 39%	1907
	11th to 20th	Night	4 4 1 6% 4 5% 5% 7% 7% 11% 46%	1705
	21st to end	Night	6% 5% 2 6% 6% 5% 7% 5% 8% 10% 39%	1800
July	1st to 10th	Night	4 4 3 7% 6% 6% 7% 5% 10% 13% 34%	4078
	11th to 20th	Night	3 4 2 6% 5% 6% 6% 5% 9% 13% 40%	4077
	21st to end	Night	5% 5% 3 9% 6% 6% 7% 5% 9% 12% 33%	4924
August	1st to 10th	Night	2 2 1 3 3 3 5% 4 7% 11% 57%	3244
	11th to 20th	Night	3 4 1 5% 4 5% 6% 5% 8% 13% 45%	3200
	21st to end	Night	6% 6% 3 7% 5% 5% 6% 5% 7% 10% 40%	3586
September	1st to 10th	Night	8% 6% 3 6% 5% 5% 5% 5% 8% 10% 41%	2000
	11th to 20th	Night	9% 5% 2 6% 4 5% 5% 5% 7% 8% 45%	2039
	21st to end	Night	8% 5% 2 6% 4 5% 4 3 5% 7% 51%	2200
October	1st to 10th	Night	8% 4 2 5% 3 4 3 3 5% 7% 57%	2287
	11th to 20th	Night	6% 4 2 4 3 3 3 3 4 7% 62%	2400
	21st to end	Night	12% 5% 2 4 2 3 3 2 4 5% 57%	2640
November	1st to 10th	Night	11% 4 2 5% 3 3 3 3 4 5% 56%	2460
	11th to 20th	Night	13% 5% 2 3 3 3 3 3 5% 5% 55%	2637
	21st to end	Night	13% 6% 2 5% 4 3 4 3 5% 6% 47%	2730
December	1st to 10th	Night	18% 8% 2 6% 4 4 4 3 4 5% 44%	4277
	11th to 20th	Night	12% 9% 2 6% 4 4 4 3 5% 6% 45%	4822
	21st to end	Night	21% 9% 2 5% 3 3 3 2 3 5% 44%	6186

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	41% 4 4 19% 27% 7%	4078
	11th to 20th	Day	38% 2 4 16% 29% 10%	4080
	21st to end	Day	52% 3 6% 12% 16% 12%	4899
February	1st to 10th	Day	48% 3 7% 13% 19% 10%	2000
	11th to 20th	Day	43% 4 6% 17% 20% 10%	1958
	21st to end	Day	49% 3 8% 14% 17% 10%	1650
March	1st to 10th	Day	49% 3 7% 15% 16% 10%	4699
	11th to 20th	Day	39% 4 7% 13% 18% 17%	4980
	21st to end	Day	46% 4 9% 14% 18% 8%	5736
April	1st to 10th	Day	42% 5% 9% 17% 17% 9%	2400
	11th to 20th	Day	42% 4 7% 18% 18% 10%	2374
	21st to end	Day	36% 5% 10% 23% 21% 5%	2400
May	1st to 10th	Day	47% 5% 13% 22% 11% 3	5440
	11th to 20th	Day	36% 5% 15% 23% 19% 2	5408
	21st to end	Day	34% 6% 16% 29% 13% 2	5945
June	1st to 10th	Day	46% 7% 13% 23% 10% 1	2449
	11th to 20th	Day	42% 7% 16% 20% 13% 2	2660
	21st to end	Day	48% 10% 16% 19% 7% 1	2600
July	1st to 10th	Day	43% 11% 25% 17% 4	5836
	11th to 20th	Day	40% 12% 33% 13% 1	5831
	21st to end	Day	44% 12% 19% 22% 3	5752
August	1st to 10th	Day	26% 6% 15% 27% 25% 1	3893
	11th to 20th	Day	35% 8% 19% 26% 11% 1	3885
	21st to end	Day	47% 7% 13% 16% 15% 2	4311
September	1st to 10th	Day	45% 7% 14% 18% 13% 3	2400
	11th to 20th	Day	40% 7% 12% 18% 16% 7%	2340
	21st to end	Day	33% 5% 10% 23% 20% 9%	2200
October	1st to 10th	Day	28% 2 6% 12% 23% 29%	3433
	11th to 20th	Day	18% 2 4 18% 28% 30%	3240
	21st to end	Day	21% 4 4 14% 38% 20%	3538
November	1st to 10th	Day	32% 3 7% 19% 26% 13%	2058
	11th to 20th	Day	31% 3 7% 17% 29% 12%	1977
	21st to end	Day	39% 4 7% 17% 23% 11%	1890
December	1st to 10th	Day	45% 3 6% 15% 24% 6%	2948
	11th to 20th	Day	39% 4 10% 15% 23% 10%	3370
	21st to end	Day	42% 3 7% 18% 26% 4	4750
January	1st to 10th	Night	39% 3 5% 19% 26% 8%	5888
	11th to 20th	Night	41% 2 3 16% 27% 11%	5900
	21st to end	Night	50% 3 5% 13% 20% 10%	6053
February	1st to 10th	Night	44% 3 6% 17% 20% 10%	2400
	11th to 20th	Night	47% 3 4 14% 19% 12%	2339
	21st to end	Night	47% 4 8% 14% 14% 12%	1980
March	1st to 10th	Night	49% 3 7% 12% 20% 9%	5196
	11th to 20th	Night	39% 4 8% 15% 19% 15%	4980
	21st to end	Night	42% 4 8% 21% 17% 8%	5193
April	1st to 10th	Night	42% 4 10% 17% 17% 11%	2000
	11th to 20th	Night	40% 3 8% 20% 19% 10%	1975
	21st to end	Night	28% 5% 12% 23% 25% 7%	2000
May	1st to 10th	Night	45% 5% 13% 19% 14% 3	4520
	11th to 20th	Night	38% 6% 17% 24% 14% 1	4490
	21st to end	Night	32% 6% 21% 30% 10% 1	4931
June	1st to 10th	Night	36% 7% 17% 27% 12% 1	1907
	11th to 20th	Night	28% 10% 20% 28% 12% 2	1705
	21st to end	Night	37% 9% 21% 23% 9% 1	1800
July	1st to 10th	Night	34% 14% 29% 17% 5%	4035
	11th to 20th	Night	31% 15% 41% 11% 1	4026
	21st to end	Night	40% 16% 18% 24% 3	4781
August	1st to 10th	Night	18% 7% 22% 28% 24% 1	3232
	11th to 20th	Night	27% 11% 25% 29% 8% 1	3230
	21st to end	Night	39% 9% 18% 18% 12% 4	3586
September	1st to 10th	Night	36% 8% 21% 18% 12% 6%	2000
	11th to 20th	Night	34% 8% 17% 19% 14% 8%	2039
	21st to end	Night	31% 5% 11% 26% 17% 11%	2200
October	1st to 10th	Night	27% 3 7% 13% 22% 27%	3742
	11th to 20th	Night	16% 2 4 20% 27% 30%	3899
	21st to end	Night	20% 2 5% 12% 36% 24%	4252
November	1st to 10th	Night	31% 3 8% 19% 24% 15%	2460
	11th to 20th	Night	31% 3 7% 16% 27% 16%	2637
	21st to end	Night	37% 3 7% 20% 20% 13%	2730
December	1st to 10th	Night	45% 2 5% 17% 25% 6%	4277
	11th to 20th	Night	40% 4 9% 17% 20% 10%	4824
	21st to end	Night	46% 3 6% 17% 22% 8%	6186

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	27% 16% 36% 16% 4 1	300
	11th to 20th	Day	24% 17% 35% 18% 5%	300
	21st to end	Day	29% 20% 34% 14% 3	330
February	1st to 10th	Day	28% 17% 34% 15% 5% 1	300
	11th to 20th	Day	33% 16% 32% 15% 4	300
	21st to end	Day	23% 26% 37% 11% 3	249
March	1st to 10th	Day	23% 18% 38% 19% 2	300
	11th to 20th	Day	27% 20% 33% 15% 4	300
	21st to end	Day	21% 16% 34% 21% 7%	447
April	1st to 10th	Day	22% 15% 32% 21% 10% 1	500
	11th to 20th	Day	21% 14% 30% 23% 11% 1	492
	21st to end	Day	12% 10% 32% 27% 16% 3	500
May	1st to 10th	Day	15% 11% 29% 25% 17% 3	503
	11th to 20th	Day	15% 5% 25% 30% 18% 7%	527
	21st to end	Day	8% 3 19% 35% 24% 10%	573
June	1st to 10th	Day	14% 3 12% 30% 27% 14%	533
	11th to 20th	Day	7% 3 13% 35% 31% 11%	730
	21st to end	Day	10% 3 10% 28% 32% 17%	730
July	1st to 10th	Day	9% 2 6% 26% 39% 19%	721
	11th to 20th	Day	9% 2 3 23% 39% 24%	718
	21st to end	Day	11% 2 4 21% 36% 26%	576
August	1st to 10th	Day	4 2 4 21% 40% 29%	526
	11th to 20th	Day	7% 2 4 17% 38% 32%	519
	21st to end	Day	12% 4 7% 22% 32% 23%	583
September	1st to 10th	Day	11% 2 8% 25% 36% 17%	530
	11th to 20th	Day	10% 4 10% 25% 34% 16%	530
	21st to end	Day	10% 5% 12% 32% 32% 9%	530
October	1st to 10th	Day	8% 6% 22% 35% 22% 6%	438
	11th to 20th	Day	7% 7% 26% 31% 23% 5%	330
	21st to end	Day	18% 9% 21% 32% 17% 3	363
November	1st to 10th	Day	16% 8% 24% 37% 12% 4	330
	11th to 20th	Day	15% 12% 32% 26% 13% 2	330
	21st to end	Day	15% 17% 35% 20% 8% 4	330
December	1st to 10th	Day	23% 10% 36% 21% 9% 1	306
	11th to 20th	Day	21% 16% 40% 17% 6% 1	300
	21st to end	Day	25% 15% 32% 20% 7% 1	330
January	1st to 10th	Night	23% 12% 33% 26% 7%	1000
	11th to 20th	Night	24% 12% 30% 26% 8% 1	1000
	21st to end	Night	25% 14% 31% 27% 4	910
February	1st to 10th	Night	23% 11% 35% 27% 4	800
	11th to 20th	Night	27% 14% 28% 25% 5%	783
	21st to end	Night	24% 14% 37% 22% 2	660
March	1st to 10th	Night	20% 15% 33% 26% 7%	727
	11th to 20th	Night	19% 10% 33% 30% 9%	600
	21st to end	Night	17% 12% 32% 28% 11%	660
April	1st to 10th	Night	20% 12% 29% 28% 12% 1	600
	11th to 20th	Night	18% 8% 32% 29% 12% 1	593
	21st to end	Night	12% 5% 27% 40% 15%	600
May	1st to 10th	Night	13% 4 27% 38% 18%	600
	11th to 20th	Night	11% 3 23% 37% 24% 3	591
	21st to end	Night	8% 2 17% 36% 30% 7%	650
June	1st to 10th	Night	9% 2 10% 37% 36% 7%	600
	11th to 20th	Night	5% 1 7% 33% 43% 10%	600
	21st to end	Night	8% 2 7% 27% 41% 15%	600
July	1st to 10th	Night	6% 2 4 20% 49% 19%	585
	11th to 20th	Night	4 1 3 18% 50% 25%	582
	21st to end	Night	6% 1 3 21% 47% 21%	657
August	1st to 10th	Night	4 1 2 19% 48% 26%	597
	11th to 20th	Night	7% 1 2 16% 49% 25%	594
	21st to end	Night	10% 2 5% 21% 40% 22%	660
September	1st to 10th	Night	9% 3 8% 25% 40% 15%	600
	11th to 20th	Night	11% 3 8% 25% 43% 11%	639
	21st to end	Night	10% 3 9% 34% 37% 7%	800
October	1st to 10th	Night	10% 3 18% 35% 31% 4	800
	11th to 20th	Night	9% 3 20% 38% 26% 3	800
	21st to end	Night	14% 7% 21% 36% 20% 3	880
November	1st to 10th	Night	14% 7% 20% 38% 20% 2	820
	11th to 20th	Night	16% 7% 28% 34% 15% 1	840
	21st to end	Night	16% 9% 29% 30% 14% 1	840
December	1st to 10th	Night	20% 11% 28% 28% 12%	809
	11th to 20th	Night	22% 7% 32% 30% 9%	800
	21st to end	Night	28% 11% 27% 28% 6%	965

Page generated at 2025-11-30 00:00:57. Version ac07

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