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 2024-10-20.

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% 38%	100820
	Night	13% 8% 3 7% 5% 5% 4 4 6% 8% 39%	97815
Transparency	Day	41% 9% 12% 21% 14% 3	100632
	Night	41% 8% 12% 21% 16% 3	97672
Seeing	Day	17% 10% 22% 23% 19% 9%	14764
	Night	16% 8% 22% 30% 20% 3	24777

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% 11% 3 8% 5% 5% 5% 4 7% 6% 30%	2836
	11th to 20th	Day	17% 11% 4 8% 5% 4 6% 4 5% 5% 31%	2840
	21st to end	Day	21% 13% 3 7% 4 4 3 3 4 5% 32%	3138
February	1st to 10th	Day	20% 10% 3 8% 5% 4 4 3 5% 4 34%	1900
	11th to 20th	Day	20% 10% 4 8% 5% 4 3 3 4 5% 33%	1848
	21st to end	Day	21% 9% 3 6% 4 4 4 3 5% 6% 35%	1570
March	1st to 10th	Day	21% 11% 3 7% 4 4 4 3 4 6% 32%	3202
	11th to 20th	Day	13% 6% 3 7% 4 4 4 3 5% 5% 47%	3480
	21st to end	Day	16% 8% 2 7% 5% 4 5% 4 5% 6% 39%	3815
April	1st to 10th	Day	11% 5% 2 6% 5% 4 5% 4 7% 8% 42%	2172
	11th to 20th	Day	13% 6% 2 6% 4 4 4 4 5% 7% 45%	2254
	21st to end	Day	12% 7% 3 6% 4 5% 4 4 6% 6% 43%	2466
May	1st to 10th	Day	12% 7% 3 8% 6% 5% 5% 4 6% 8% 35%	4082
	11th to 20th	Day	14% 9% 3 8% 5% 5% 5% 4 6% 7% 34%	4081
	21st to end	Day	9% 6% 2 7% 5% 5% 6% 5% 7% 9% 38%	4476
June	1st to 10th	Day	8% 6% 3 7% 5% 5% 6% 5% 7% 10% 37%	2470
	11th to 20th	Day	4 4 2 5% 5% 6% 6% 6% 9% 11% 41%	2470
	21st to end	Day	6% 6% 2 6% 6% 6% 5% 5% 8% 11% 38%	2470
July	1st to 10th	Day	5% 5% 2 6% 6% 7% 7% 6% 10% 13% 34%	4120
	11th to 20th	Day	9% 6% 2 7% 6% 5% 6% 5% 8% 10% 37%	4120
	21st to end	Day	14% 11% 4 11% 7% 7% 7% 6% 6% 8% 19%	4466
August	1st to 10th	Day	6% 5% 2 6% 6% 6% 6% 6% 9% 11% 38%	4104
	11th to 20th	Day	6% 5% 2 7% 5% 6% 7% 5% 8% 11% 38%	3895
	21st to end	Day	6% 4 2 5% 4 5% 5% 4 6% 9% 50%	4180
September	1st to 10th	Day	11% 7% 2 7% 5% 5% 4 4 6% 8% 41%	2115
	11th to 20th	Day	14% 5% 2 6% 5% 4 5% 4 6% 8% 40%	2090
	21st to end	Day	13% 6% 2 5% 4 4 5% 4 4 7% 47%	2090
October	1st to 10th	Day	10% 5% 2 6% 3 3 4 4 4 6% 53%	2090
	11th to 20th	Day	12% 6% 2 4 3 3 3 2 5% 7% 52%	1952
	21st to end	Day	14% 6% 2 5% 3 3 4 3 5% 7% 48%	1949
November	1st to 10th	Day	11% 5% 2 5% 3 4 3 3 5% 6% 52%	1672
	11th to 20th	Day	12% 6% 2 5% 4 3 4 3 5% 7% 48%	1710
	21st to end	Day	14% 8% 2 5% 4 4 3 4 6% 6% 43%	1710
December	1st to 10th	Day	20% 9% 3 7% 4 4 5% 3 6% 6% 33%	1710
	11th to 20th	Day	14% 12% 2 7% 4 5% 6% 4 6% 5% 35%	2153
	21st to end	Day	17% 12% 3 8% 5% 5% 4 3 5% 7% 30%	3124
January	1st to 10th	Night	17% 10% 3 8% 5% 5% 4 4 5% 6% 32%	4109
	11th to 20th	Night	18% 10% 3 7% 4 3 3 3 6% 6% 37%	4120
	21st to end	Night	19% 13% 3 8% 5% 4 4 4 6% 5% 29%	4500
February	1st to 10th	Night	15% 8% 3 7% 5% 4 5% 3 6% 6% 36%	2280
	11th to 20th	Night	21% 10% 3 7% 4 4 4 3 5% 4 35%	2218
	21st to end	Night	21% 9% 3 7% 4 5% 4 5% 4 6% 32%	1884
March	1st to 10th	Night	21% 9% 3 7% 6% 5% 5% 3 6% 6% 29%	3649
	11th to 20th	Night	12% 7% 2 5% 3 4 3 3 5% 8% 49%	3480
	21st to end	Night	14% 8% 3 8% 4 5% 4 3 4 6% 40%	3817
April	1st to 10th	Night	12% 5% 1 6% 4 4 4 3 5% 8% 47%	2023
	11th to 20th	Night	13% 7% 3 5% 4 3 3 4 4 6% 48%	1875
	21st to end	Night	12% 6% 2 7% 5% 5% 5% 4 6% 6% 43%	1711
May	1st to 10th	Night	10% 8% 3 9% 5% 6% 5% 4 6% 8% 36%	2813
	11th to 20th	Night	16% 8% 3 7% 4 4 3 4 6% 8% 37%	2812
	21st to end	Night	6% 5% 3 8% 6% 4 6% 4 8% 10% 40%	3079
June	1st to 10th	Night	6% 6% 3 7% 6% 6% 6% 5% 8% 10% 38%	1710
	11th to 20th	Night	3 3 2 5% 4 4 4 5% 9% 13% 47%	1710
	21st to end	Night	5% 5% 2 7% 6% 5% 6% 5% 7% 10% 41%	1710
July	1st to 10th	Night	7% 6% 2 8% 6% 7% 7% 6% 8% 10% 32%	2840
	11th to 20th	Night	8% 5% 2 5% 5% 5% 6% 5% 8% 10% 41%	2840
	21st to end	Night	12% 11% 4 10% 7% 7% 6% 6% 8% 9% 22%	3087
August	1st to 10th	Night	6% 5% 2 7% 6% 6% 4 5% 8% 12% 39%	2825
	11th to 20th	Night	8% 6% 2 7% 5% 5% 5% 5% 7% 9% 44%	2930
	21st to end	Night	5% 4 2 5% 4 5% 5% 4 7% 10% 48%	3476
September	1st to 10th	Night	9% 7% 2 6% 6% 5% 5% 4 7% 7% 41%	2044
	11th to 20th	Night	12% 8% 2 8% 5% 4 5% 3 6% 8% 40%	2090
	21st to end	Night	11% 5% 2 5% 5% 5% 5% 4 5% 7% 46%	2090
October	1st to 10th	Night	11% 5% 2 5% 3 3 3 3 4 7% 54%	2090
	11th to 20th	Night	14% 4 2 4 4 4 4 3 4 5% 53%	2211
	21st to end	Night	13% 6% 2 5% 4 3 3 3 4 5% 51%	2402
November	1st to 10th	Night	13% 6% 2 5% 3 3 3 2 5% 6% 51%	2406
	11th to 20th	Night	13% 6% 3 6% 4 4 3 3 4 6% 48%	2470
	21st to end	Night	14% 7% 3 5% 4 4 4 3 6% 7% 43%	2470
December	1st to 10th	Night	19% 10% 3 7% 5% 4 4 3 5% 6% 34%	2470
	11th to 20th	Night	16% 9% 3 8% 4 4 5% 4 5% 6% 36%	3042
	21st to end	Night	18% 10% 4 8% 5% 6% 6% 5% 6% 7% 26%	4532

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% 8% 8% 20% 15% 1	2837
	11th to 20th	Day	50% 9% 9% 15% 16% 1	2840
	21st to end	Day	52% 6% 8% 21% 13% 1	3138
February	1st to 10th	Day	52% 5% 9% 17% 15% 2	1900
	11th to 20th	Day	53% 5% 8% 18% 14% 2	1858
	21st to end	Day	50% 5% 9% 14% 16% 6%	1570
March	1st to 10th	Day	51% 7% 9% 16% 11% 6%	3202
	11th to 20th	Day	38% 6% 8% 22% 22% 5%	3480
	21st to end	Day	45% 6% 9% 27% 12% 2	3815
April	1st to 10th	Day	37% 9% 11% 23% 17% 3	2172
	11th to 20th	Day	38% 6% 9% 17% 24% 5%	2254
	21st to end	Day	40% 7% 11% 26% 14% 3	2466
May	1st to 10th	Day	43% 11% 11% 22% 12% 1	4120
	11th to 20th	Day	46% 10% 11% 22% 9% 1	4085
	21st to end	Day	37% 10% 13% 21% 16% 2	4489
June	1st to 10th	Day	38% 12% 15% 20% 13% 2	2470
	11th to 20th	Day	31% 12% 20% 21% 14% 2	2470
	21st to end	Day	36% 12% 17% 19% 13% 3	2470
July	1st to 10th	Day	35% 13% 22% 20% 10% 1	4055
	11th to 20th	Day	39% 10% 20% 21% 7% 2	4051
	21st to end	Day	60% 10% 12% 13% 4	4324
August	1st to 10th	Day	34% 12% 18% 27% 9% 1	4091
	11th to 20th	Day	34% 10% 18% 23% 12% 1	3934
	21st to end	Day	30% 9% 13% 33% 13% 2	4179
September	1st to 10th	Day	38% 8% 14% 18% 17% 6%	2115
	11th to 20th	Day	40% 9% 11% 20% 18% 3	2090
	21st to end	Day	36% 7% 11% 22% 18% 6%	2090
October	1st to 10th	Day	31% 7% 10% 23% 24% 6%	2090
	11th to 20th	Day	31% 6% 10% 23% 24% 6%	1952
	21st to end	Day	35% 5% 8% 24% 24% 5%	1949
November	1st to 10th	Day	32% 4 9% 22% 27% 6%	1672
	11th to 20th	Day	36% 5% 7% 23% 24% 5%	1710
	21st to end	Day	39% 6% 9% 24% 19% 3	1710
December	1st to 10th	Day	51% 7% 8% 22% 11% 2	1710
	11th to 20th	Day	47% 8% 9% 17% 17% 2	2150
	21st to end	Day	50% 7% 10% 23% 9% 1	3124
January	1st to 10th	Night	48% 8% 9% 19% 15% 1	4109
	11th to 20th	Night	47% 7% 7% 17% 18% 5%	4120
	21st to end	Night	53% 7% 7% 16% 15% 1	4500
February	1st to 10th	Night	47% 6% 9% 19% 17% 2	2280
	11th to 20th	Night	52% 6% 7% 17% 15% 4	2219
	21st to end	Night	51% 7% 9% 14% 15% 4	1884
March	1st to 10th	Night	49% 10% 11% 14% 13% 3	3649
	11th to 20th	Night	33% 7% 9% 23% 18% 10%	3480
	21st to end	Night	42% 7% 9% 23% 16% 2	3817
April	1st to 10th	Night	35% 7% 12% 22% 20% 3	2023
	11th to 20th	Night	36% 6% 9% 21% 22% 6%	1875
	21st to end	Night	38% 7% 11% 27% 15% 1	1711
May	1st to 10th	Night	42% 11% 14% 21% 11% 1	2840
	11th to 20th	Night	42% 9% 15% 21% 12% 1	2813
	21st to end	Night	33% 13% 15% 24% 15% 1	3087
June	1st to 10th	Night	37% 11% 16% 21% 13% 2	1710
	11th to 20th	Night	24% 12% 23% 26% 13% 2	1710
	21st to end	Night	35% 11% 15% 22% 12% 4	1710
July	1st to 10th	Night	42% 13% 18% 19% 8% 1	2795
	11th to 20th	Night	34% 9% 23% 24% 7% 3	2786
	21st to end	Night	55% 12% 14% 13% 5% 1	2988
August	1st to 10th	Night	34% 10% 17% 28% 10% 1	2814
	11th to 20th	Night	33% 11% 19% 24% 12% 1	2957
	21st to end	Night	26% 10% 15% 35% 13% 1	3476
September	1st to 10th	Night	37% 10% 15% 17% 15% 5%	2044
	11th to 20th	Night	40% 9% 13% 17% 20% 1	2090
	21st to end	Night	35% 7% 12% 20% 19% 6%	2090
October	1st to 10th	Night	30% 5% 10% 20% 26% 8%	2090
	11th to 20th	Night	33% 6% 8% 23% 23% 8%	2211
	21st to end	Night	34% 5% 7% 21% 26% 7%	2402
November	1st to 10th	Night	35% 5% 7% 20% 25% 8%	2406
	11th to 20th	Night	37% 6% 7% 20% 23% 7%	2470
	21st to end	Night	40% 5% 8% 23% 21% 3	2470
December	1st to 10th	Night	50% 8% 9% 19% 12% 3	2470
	11th to 20th	Night	45% 7% 8% 18% 21% 2	3044
	21st to end	Night	51% 9% 11% 18% 10% 1	4532

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% 21% 29% 20% 4	270
	11th to 20th	Day	30% 24% 26% 14% 6% 1	270
	21st to end	Day	20% 24% 37% 13% 5%	297
February	1st to 10th	Day	27% 19% 28% 17% 8% 1	270
	11th to 20th	Day	33% 23% 31% 10% 2	270
	21st to end	Day	40% 19% 28% 12%	225
March	1st to 10th	Day	26% 17% 31% 19% 6% 1	313
	11th to 20th	Day	19% 21% 37% 17% 7%	460
	21st to end	Day	25% 16% 33% 18% 8% 1	506
April	1st to 10th	Day	20% 18% 23% 26% 11% 2	460
	11th to 20th	Day	20% 14% 29% 21% 14% 2	452
	21st to end	Day	20% 10% 30% 24% 13% 3	460
May	1st to 10th	Day	14% 13% 32% 22% 14% 5%	463
	11th to 20th	Day	13% 7% 24% 27% 20% 9%	487
	21st to end	Day	13% 6% 19% 26% 19% 15%	529
June	1st to 10th	Day	12% 6% 20% 27% 24% 11%	490
	11th to 20th	Day	7% 4 12% 27% 31% 19%	490
	21st to end	Day	9% 3 17% 28% 26% 17%	490
July	1st to 10th	Day	11% 2 14% 21% 30% 23%	485
	11th to 20th	Day	12% 1 11% 26% 29% 21%	484
	21st to end	Day	11% 2 9% 24% 33% 20%	532
August	1st to 10th	Day	12% 3 13% 24% 30% 18%	486
	11th to 20th	Day	10% 3 12% 32% 30% 13%	479
	21st to end	Day	10% 2 12% 20% 32% 23%	539
September	1st to 10th	Day	9% 4 12% 25% 34% 16%	490
	11th to 20th	Day	15% 3 9% 23% 31% 18%	490
	21st to end	Day	16% 6% 14% 24% 31% 10%	490
October	1st to 10th	Day	11% 7% 19% 27% 26% 11%	490
	11th to 20th	Day	12% 11% 22% 30% 21% 4	486
	21st to end	Day	20% 8% 22% 29% 18% 3	464
November	1st to 10th	Day	16% 9% 29% 28% 15% 3	270
	11th to 20th	Day	15% 13% 31% 32% 7% 1	270
	21st to end	Day	13% 11% 34% 30% 11% 1	270
December	1st to 10th	Day	29% 15% 31% 19% 6% 1	270
	11th to 20th	Day	24% 16% 26% 20% 11% 1	270
	21st to end	Day	26% 18% 29% 18% 8% 1	297
January	1st to 10th	Night	24% 15% 31% 25% 5%	760
	11th to 20th	Night	25% 15% 29% 25% 5%	760
	21st to end	Night	22% 13% 36% 27% 2	836
February	1st to 10th	Night	19% 12% 34% 31% 4	760
	11th to 20th	Night	27% 16% 34% 21% 2	743
	21st to end	Night	29% 15% 33% 21% 2	628
March	1st to 10th	Night	22% 13% 29% 31% 4	760
	11th to 20th	Night	23% 12% 33% 25% 7% 1	760
	21st to end	Night	21% 13% 30% 27% 9%	836
April	1st to 10th	Night	15% 13% 31% 32% 9% 1	693
	11th to 20th	Night	15% 10% 32% 28% 14%	563
	21st to end	Night	15% 8% 29% 36% 12% 1	570
May	1st to 10th	Night	11% 7% 24% 37% 18% 3	570
	11th to 20th	Night	14% 6% 19% 32% 25% 4	561
	21st to end	Night	8% 3 13% 33% 38% 4	617
June	1st to 10th	Night	8% 3 15% 36% 33% 5%	570
	11th to 20th	Night	3 2 13% 35% 36% 11%	570
	21st to end	Night	7% 3 12% 32% 38% 8%	570
July	1st to 10th	Night	10% 2 7% 26% 46% 10%	555
	11th to 20th	Night	10% 3 6% 27% 43% 11%	552
	21st to end	Night	8% 2 9% 29% 40% 12%	624
August	1st to 10th	Night	9% 2 8% 26% 45% 11%	567
	11th to 20th	Night	8% 2 10% 31% 43% 5%	564
	21st to end	Night	10% 1 9% 23% 46% 11%	627
September	1st to 10th	Night	10% 3 11% 29% 39% 9%	714
	11th to 20th	Night	15% 3 9% 30% 37% 5%	760
	21st to end	Night	14% 3 18% 31% 33% 3	760
October	1st to 10th	Night	11% 6% 19% 25% 31% 7%	760
	11th to 20th	Night	16% 5% 23% 33% 21% 2	759
	21st to end	Night	16% 7% 21% 38% 17% 2	792
November	1st to 10th	Night	16% 6% 19% 34% 22% 3	740
	11th to 20th	Night	14% 11% 29% 34% 11% 1	760
	21st to end	Night	18% 10% 26% 33% 13%	760
December	1st to 10th	Night	24% 12% 28% 30% 7%	760
	11th to 20th	Night	22% 10% 27% 32% 9%	760
	21st to end	Night	25% 14% 24% 31% 6%	836

Page generated at 2024-10-17 13:09:41. Version ac07

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