Tellico Skies Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tellico Skies Observatory clear sky chart from 2005-11-06 to 2026-07-31.

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	12% 8% 3 7% 5% 5% 5% 4 6% 8% 37%	137980
	Night	13% 8% 3 7% 5% 5% 5% 4 6% 8% 39%	135039
Transparency	Day	41% 8% 12% 21% 15% 3	141731
	Night	41% 7% 11% 21% 16% 4	139359
Seeing	Day	16% 10% 22% 23% 19% 9%	17101
	Night	16% 8% 23% 30% 20% 3	27106

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% 11% 3 8% 5% 4 4 3 6% 6% 33%	5258
	11th to 20th	Day	11% 9% 4 8% 4 4 4 3 5% 5% 43%	5280
	21st to end	Day	19% 11% 4 8% 4 4 3 3 5% 6% 34%	5822
February	1st to 10th	Day	19% 10% 3 8% 5% 5% 4 3 6% 4 34%	2100
	11th to 20th	Day	21% 10% 4 8% 5% 4 3 3 4 6% 33%	2048
	21st to end	Day	19% 8% 3 7% 4 4 4 3 5% 6% 36%	1730
March	1st to 10th	Day	18% 11% 3 8% 5% 4 4 3 5% 6% 34%	4706
	11th to 20th	Day	11% 6% 3 7% 4 4 4 3 5% 7% 47%	5090
	21st to end	Day	15% 7% 2 6% 4 4 4 3 5% 6% 43%	5586
April	1st to 10th	Day	11% 5% 2 5% 5% 4 5% 4 8% 8% 42%	2401
	11th to 20th	Day	12% 6% 2 6% 4 4 4 4 5% 7% 46%	2494
	21st to end	Day	12% 7% 3 6% 4 5% 4 4 6% 7% 42%	2726
May	1st to 10th	Day	14% 8% 3 7% 5% 5% 5% 4 6% 9% 32%	7616
	11th to 20th	Day	11% 8% 3 9% 6% 6% 6% 4 7% 7% 34%	7626
	21st to end	Day	14% 10% 4 10% 6% 5% 6% 4 6% 7% 27%	8391
June	1st to 10th	Day	8% 6% 3 7% 5% 5% 6% 5% 8% 11% 37%	2730
	11th to 20th	Day	4 4 2 6% 5% 6% 7% 6% 9% 11% 40%	2730
	21st to end	Day	6% 6% 2 6% 6% 6% 5% 5% 8% 12% 38%	2730
July	1st to 10th	Day	5% 4 2 6% 6% 6% 7% 5% 10% 12% 39%	6030
	11th to 20th	Day	8% 5% 2 7% 6% 6% 6% 6% 9% 12% 33%	6030
	21st to end	Day	11% 9% 3 10% 6% 7% 7% 6% 8% 10% 23%	6554
August	1st to 10th	Day	6% 5% 2 6% 6% 6% 6% 6% 8% 11% 38%	4234
	11th to 20th	Day	6% 5% 2 7% 5% 6% 7% 5% 8% 11% 38%	4020
	21st to end	Day	6% 4 2 5% 5% 5% 5% 4 6% 8% 49%	4312
September	1st to 10th	Day	11% 7% 2 7% 5% 5% 4 4 6% 8% 41%	2226
	11th to 20th	Day	14% 5% 2 6% 5% 4 5% 4 6% 8% 41%	2200
	21st to end	Day	13% 6% 2 5% 4 4 5% 4 5% 8% 46%	2200
October	1st to 10th	Day	9% 5% 2 6% 4 3 4 4 4 6% 52%	2200
	11th to 20th	Day	11% 5% 2 4 3 3 3 2 5% 7% 54%	2065
	21st to end	Day	15% 6% 2 5% 3 4 4 3 5% 7% 48%	2165
November	1st to 10th	Day	11% 6% 3 5% 3 4 3 3 6% 6% 51%	1852
	11th to 20th	Day	11% 6% 2 5% 5% 3 4 3 5% 8% 47%	1890
	21st to end	Day	13% 8% 2 6% 5% 4 4 4 6% 7% 42%	1890
December	1st to 10th	Day	14% 7% 3 6% 5% 4 5% 3 5% 6% 41%	3020
	11th to 20th	Day	17% 12% 3 10% 6% 5% 5% 3 5% 4 29%	3463
	21st to end	Day	14% 11% 3 8% 6% 5% 5% 4 6% 8% 30%	4565
January	1st to 10th	Night	15% 8% 3 9% 5% 4 4 3 5% 6% 37%	7635
	11th to 20th	Night	16% 8% 2 6% 3 3 3 3 5% 6% 45%	7680
	21st to end	Night	17% 11% 3 7% 5% 4 4 3 5% 6% 34%	8341
February	1st to 10th	Night	15% 9% 3 7% 5% 4 5% 4 6% 7% 36%	2520
	11th to 20th	Night	21% 10% 3 7% 4 4 4 3 5% 4 35%	2458
	21st to end	Night	20% 9% 3 7% 4 4 4 5% 4 6% 33%	2076
March	1st to 10th	Night	18% 9% 3 7% 5% 5% 5% 3 5% 7% 33%	5365
	11th to 20th	Night	11% 6% 2 4 3 4 4 3 6% 8% 50%	5090
	21st to end	Night	12% 7% 2 8% 5% 5% 5% 3 5% 7% 41%	5588
April	1st to 10th	Night	12% 5% 1 5% 4 4 4 3 6% 9% 46%	2235
	11th to 20th	Night	12% 6% 3 5% 4 3 3 4 4 6% 49%	2075
	21st to end	Night	12% 6% 2 7% 5% 5% 5% 4 6% 6% 43%	1891
May	1st to 10th	Night	13% 9% 3 9% 5% 5% 5% 4 7% 9% 31%	5237
	11th to 20th	Night	13% 8% 3 8% 5% 5% 4 3 6% 8% 36%	5234
	21st to end	Night	15% 9% 4 10% 6% 5% 5% 4 6% 7% 29%	5761
June	1st to 10th	Night	6% 6% 3 7% 5% 6% 6% 5% 8% 10% 38%	1890
	11th to 20th	Night	4 4 1 6% 4 4 4 5% 10% 13% 46%	1890
	21st to end	Night	6% 5% 2 7% 5% 5% 6% 5% 7% 10% 42%	1890
July	1st to 10th	Night	7% 6% 2 8% 6% 6% 7% 6% 8% 11% 32%	4148
	11th to 20th	Night	7% 5% 2 7% 5% 6% 6% 5% 9% 12% 35%	4147
	21st to end	Night	10% 9% 4 10% 7% 7% 7% 6% 9% 11% 22%	4517
August	1st to 10th	Night	6% 5% 2 7% 6% 6% 5% 5% 8% 12% 38%	2915
	11th to 20th	Night	7% 6% 2 7% 5% 5% 4 5% 7% 9% 43%	3024
	21st to end	Night	5% 4 2 5% 4 5% 6% 4 7% 10% 48%	3586
September	1st to 10th	Night	10% 7% 2 6% 6% 5% 5% 4 7% 8% 40%	2152
	11th to 20th	Night	11% 7% 2 8% 4 4 5% 4 6% 8% 40%	2200
	21st to end	Night	12% 6% 2 5% 4 5% 5% 4 5% 7% 45%	2200
October	1st to 10th	Night	11% 5% 2 5% 3 4 3 3 4 7% 53%	2200
	11th to 20th	Night	13% 4 2 4 4 4 4 3 4 5% 54%	2333
	21st to end	Night	14% 6% 2 5% 3 3 3 3 4 5% 52%	2670
November	1st to 10th	Night	13% 6% 2 5% 4 4 4 3 4 6% 50%	2666
	11th to 20th	Night	13% 6% 2 6% 4 4 3 3 5% 6% 48%	2730
	21st to end	Night	14% 7% 3 5% 4 4 5% 3 6% 7% 43%	2730
December	1st to 10th	Night	15% 8% 3 7% 5% 5% 4 3 6% 7% 38%	4380
	11th to 20th	Night	20% 9% 4 7% 5% 4 4 4 5% 6% 31%	4952
	21st to end	Night	15% 9% 3 8% 5% 5% 5% 5% 6% 8% 30%	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	48% 6% 10% 23% 12% 1	5259
	11th to 20th	Day	41% 7% 6% 17% 26% 4	5280
	21st to end	Day	50% 5% 7% 22% 13% 3	5822
February	1st to 10th	Day	51% 5% 9% 18% 14% 2	2100
	11th to 20th	Day	53% 5% 9% 18% 13% 2	2058
	21st to end	Day	49% 5% 9% 16% 17% 5%	1730
March	1st to 10th	Day	48% 6% 8% 14% 16% 8%	4706
	11th to 20th	Day	36% 5% 7% 18% 25% 9%	5090
	21st to end	Day	41% 5% 8% 30% 14% 1	5586
April	1st to 10th	Day	36% 9% 12% 24% 16% 3	2401
	11th to 20th	Day	36% 6% 9% 20% 24% 5%	2494
	21st to end	Day	40% 7% 11% 25% 14% 2	2726
May	1st to 10th	Day	46% 8% 12% 22% 11% 1	7651
	11th to 20th	Day	46% 8% 15% 20% 10% 1	7630
	21st to end	Day	53% 8% 10% 15% 11% 2	8405
June	1st to 10th	Day	38% 11% 15% 21% 13% 2	2730
	11th to 20th	Day	33% 12% 20% 21% 13% 2	2730
	21st to end	Day	35% 12% 17% 19% 13% 3	2730
July	1st to 10th	Day	33% 12% 20% 23% 12% 1	5965
	11th to 20th	Day	39% 11% 25% 18% 5% 2	5961
	21st to end	Day	51% 11% 17% 16% 5%	6370
August	1st to 10th	Day	34% 11% 17% 27% 9% 1	4221
	11th to 20th	Day	35% 11% 18% 23% 12% 1	4059
	21st to end	Day	30% 9% 13% 33% 14% 2	4311
September	1st to 10th	Day	38% 8% 13% 18% 17% 6%	2226
	11th to 20th	Day	39% 9% 11% 21% 17% 3	2200
	21st to end	Day	37% 7% 11% 22% 18% 6%	2200
October	1st to 10th	Day	26% 5% 7% 20% 30% 11%	3590
	11th to 20th	Day	22% 4 6% 24% 31% 12%	3344
	21st to end	Day	28% 4 9% 27% 23% 9%	3479
November	1st to 10th	Day	33% 4 10% 22% 26% 5%	1852
	11th to 20th	Day	35% 5% 7% 24% 24% 4	1890
	21st to end	Day	40% 6% 9% 24% 19% 3	1890
December	1st to 10th	Day	42% 6% 7% 22% 22% 2	3020
	11th to 20th	Day	56% 6% 8% 16% 12% 2	3460
	21st to end	Day	48% 7% 14% 23% 8% 1	4565
January	1st to 10th	Night	44% 5% 14% 23% 12% 1	7636
	11th to 20th	Night	40% 6% 5% 19% 26% 4	7680
	21st to end	Night	49% 5% 8% 17% 15% 5%	8341
February	1st to 10th	Night	47% 6% 9% 20% 16% 2	2520
	11th to 20th	Night	52% 6% 7% 17% 14% 3	2459
	21st to end	Night	50% 7% 9% 16% 15% 4	2076
March	1st to 10th	Night	47% 8% 9% 16% 17% 4	5365
	11th to 20th	Night	32% 6% 7% 20% 23% 11%	5090
	21st to end	Night	41% 7% 9% 26% 15% 2	5588
April	1st to 10th	Night	35% 7% 13% 23% 20% 3	2235
	11th to 20th	Night	35% 6% 8% 23% 22% 6%	2075
	21st to end	Night	39% 7% 12% 26% 15% 1	1891
May	1st to 10th	Night	46% 9% 13% 21% 10% 1	5264
	11th to 20th	Night	46% 7% 14% 20% 12%	5235
	21st to end	Night	51% 9% 12% 18% 10% 1	5771
June	1st to 10th	Night	37% 11% 16% 21% 14% 2	1890
	11th to 20th	Night	25% 12% 23% 26% 13% 2	1890
	21st to end	Night	35% 11% 16% 23% 13% 4	1890
July	1st to 10th	Night	40% 12% 18% 20% 9% 1	4105
	11th to 20th	Night	37% 10% 27% 19% 4 2	4096
	21st to end	Night	51% 12% 19% 13% 4	4387
August	1st to 10th	Night	35% 10% 17% 28% 10% 1	2904
	11th to 20th	Night	33% 11% 20% 24% 12% 1	3051
	21st to end	Night	27% 10% 15% 34% 13% 1	3586
September	1st to 10th	Night	38% 10% 15% 17% 15% 5%	2152
	11th to 20th	Night	39% 9% 13% 18% 20% 1	2200
	21st to end	Night	36% 7% 12% 20% 19% 6%	2200
October	1st to 10th	Night	29% 5% 8% 19% 26% 12%	3590
	11th to 20th	Night	21% 4 5% 24% 31% 15%	3793
	21st to end	Night	25% 4 5% 27% 28% 11%	4306
November	1st to 10th	Night	35% 5% 8% 21% 24% 7%	2666
	11th to 20th	Night	36% 6% 7% 21% 24% 7%	2730
	21st to end	Night	41% 5% 8% 23% 20% 3	2730
December	1st to 10th	Night	45% 7% 7% 19% 21% 2	4380
	11th to 20th	Night	52% 6% 8% 17% 15% 1	4954
	21st to end	Night	48% 7% 15% 19% 10% 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	28% 19% 29% 20% 3	330
	11th to 20th	Day	27% 23% 29% 15% 5% 1	330
	21st to end	Day	21% 23% 38% 13% 4	363
February	1st to 10th	Day	25% 21% 29% 17% 8% 1	330
	11th to 20th	Day	33% 23% 31% 10% 2	330
	21st to end	Day	36% 18% 30% 14% 2	273
March	1st to 10th	Day	25% 17% 35% 17% 6% 1	378
	11th to 20th	Day	21% 20% 35% 17% 7%	540
	21st to end	Day	23% 16% 33% 20% 7% 1	594
April	1st to 10th	Day	20% 17% 24% 26% 11% 2	540
	11th to 20th	Day	18% 15% 30% 21% 14% 2	532
	21st to end	Day	19% 11% 29% 24% 14% 3	540
May	1st to 10th	Day	15% 15% 31% 21% 13% 4	543
	11th to 20th	Day	12% 8% 26% 27% 19% 8%	567
	21st to end	Day	14% 8% 21% 25% 18% 13%	617
June	1st to 10th	Day	12% 6% 20% 27% 24% 11%	570
	11th to 20th	Day	6% 4 15% 28% 30% 17%	570
	21st to end	Day	9% 3 16% 27% 26% 19%	570
July	1st to 10th	Day	10% 3 12% 22% 29% 24%	565
	11th to 20th	Day	12% 2 10% 26% 30% 21%	564
	21st to end	Day	12% 2 10% 24% 31% 21%	616
August	1st to 10th	Day	13% 4 12% 23% 29% 18%	526
	11th to 20th	Day	10% 3 11% 30% 31% 15%	519
	21st to end	Day	10% 3 13% 21% 32% 22%	583
September	1st to 10th	Day	9% 5% 12% 26% 33% 15%	530
	11th to 20th	Day	14% 3 9% 24% 30% 20%	530
	21st to end	Day	16% 5% 14% 25% 30% 10%	530
October	1st to 10th	Day	11% 7% 18% 26% 26% 12%	530
	11th to 20th	Day	12% 10% 22% 30% 21% 4	530
	21st to end	Day	20% 7% 23% 28% 18% 4	548
November	1st to 10th	Day	17% 8% 30% 27% 14% 3	330
	11th to 20th	Day	14% 13% 32% 32% 8% 1	330
	21st to end	Day	14% 12% 33% 30% 11% 1	330
December	1st to 10th	Day	27% 17% 32% 18% 5% 1	330
	11th to 20th	Day	22% 18% 26% 22% 10% 1	330
	21st to end	Day	25% 19% 28% 17% 10% 1	363
January	1st to 10th	Night	24% 14% 32% 25% 4	840
	11th to 20th	Night	25% 16% 30% 25% 4	840
	21st to end	Night	21% 13% 37% 27% 2	924
February	1st to 10th	Night	19% 13% 33% 31% 4	840
	11th to 20th	Night	27% 18% 33% 20% 2	823
	21st to end	Night	28% 16% 32% 21% 3	692
March	1st to 10th	Night	22% 14% 30% 31% 4	840
	11th to 20th	Night	23% 11% 32% 26% 6% 1	840
	21st to end	Night	20% 13% 31% 27% 8%	924
April	1st to 10th	Night	14% 13% 31% 32% 9% 1	765
	11th to 20th	Night	15% 9% 32% 31% 13%	623
	21st to end	Night	15% 7% 28% 37% 13% 1	630
May	1st to 10th	Night	11% 8% 26% 36% 16% 3	630
	11th to 20th	Night	14% 6% 19% 34% 23% 4	621
	21st to end	Night	11% 4 15% 32% 35% 4	683
June	1st to 10th	Night	8% 3 14% 38% 33% 5%	630
	11th to 20th	Night	4 3 13% 35% 36% 10%	630
	21st to end	Night	7% 3 12% 31% 39% 8%	630
July	1st to 10th	Night	9% 2 7% 24% 47% 11%	615
	11th to 20th	Night	11% 3 6% 26% 43% 12%	612
	21st to end	Night	9% 2 9% 28% 40% 12%	687
August	1st to 10th	Night	9% 3 8% 26% 43% 11%	597
	11th to 20th	Night	8% 3 10% 30% 44% 5%	594
	21st to end	Night	10% 1 9% 24% 44% 11%	660
September	1st to 10th	Night	10% 3 11% 30% 38% 9%	752
	11th to 20th	Night	15% 3 9% 30% 38% 6%	800
	21st to end	Night	14% 3 17% 31% 33% 3	800
October	1st to 10th	Night	11% 7% 19% 25% 32% 7%	800
	11th to 20th	Night	16% 5% 23% 34% 21% 2	800
	21st to end	Night	16% 6% 21% 37% 18% 2	880
November	1st to 10th	Night	15% 6% 20% 35% 21% 2	820
	11th to 20th	Night	14% 11% 29% 34% 11% 1	840
	21st to end	Night	18% 10% 27% 32% 12%	840
December	1st to 10th	Night	24% 13% 28% 30% 6%	840
	11th to 20th	Night	23% 10% 26% 32% 8%	840
	21st to end	Night	25% 14% 25% 31% 6%	924

Page generated at 2026-07-28 03:25:25. Version ac07

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