Lookout Mountain
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lookout Mountain clear sky chart from 2005-11-06 to 2024-11-10.

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	5% 7% 3 7% 5% 5% 5% 4 6% 7% 47%	105470
	Night	5% 7% 3 7% 5% 5% 5% 4 7% 8% 45%	102364
Transparency	Day	36% 7% 14% 20% 14% 8%	105213
	Night	37% 9% 17% 18% 12% 6%	102210
Seeing	Day	13% 19% 29% 25% 11% 2	14595
	Night	11% 13% 27% 30% 16% 2	23574

By Month

Percentage Cloud Cover SW (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	8% 14% 5% 9% 8% 6% 7% 6% 8% 11% 20%	2539
	11th to 20th	Day	9% 16% 4 11% 7% 6% 6% 4 7% 8% 21%	2540
	21st to end	Day	6% 16% 5% 13% 8% 6% 7% 5% 6% 8% 19%	2954
February	1st to 10th	Day	7% 14% 4 9% 7% 5% 6% 5% 8% 8% 26%	1710
	11th to 20th	Day	7% 12% 4 7% 5% 5% 6% 7% 9% 10% 28%	1665
	21st to end	Day	6% 11% 5% 11% 7% 7% 5% 4 7% 8% 28%	1544
March	1st to 10th	Day	3 11% 5% 10% 7% 6% 7% 6% 8% 9% 27%	3185
	11th to 20th	Day	3 11% 3 8% 6% 5% 4 3 5% 7% 45%	3490
	21st to end	Day	6% 15% 5% 13% 8% 6% 7% 5% 6% 6% 24%	3993
April	1st to 10th	Day	8% 11% 3 11% 7% 6% 6% 5% 6% 9% 27%	2280
	11th to 20th	Day	8% 13% 4 10% 6% 6% 4 5% 6% 7% 31%	2249
	21st to end	Day	5% 9% 3 8% 6% 5% 7% 5% 7% 9% 36%	2406
May	1st to 10th	Day	7% 8% 3 7% 5% 5% 4 3 5% 6% 46%	4420
	11th to 20th	Day	5% 4 2 5% 3 3 3 3 5% 6% 61%	4377
	21st to end	Day	8% 7% 2 7% 6% 5% 6% 6% 8% 8% 37%	4813
June	1st to 10th	Day	9% 7% 3 7% 6% 5% 5% 5% 6% 8% 40%	2660
	11th to 20th	Day	5% 5% 2 7% 5% 4 5% 4 7% 9% 46%	2660
	21st to end	Day	4 3 1 5% 4 3 4 3 5% 7% 61%	2660
July	1st to 10th	Day	1 1 1 1 1 2 2 2 3 4 82%	4420
	11th to 20th	Day	2 2 1 2 2 2 2 2 3 4 81%	4420
	21st to end	Day	3 2 1 2 1 2 2 2 2 4 80%	4790
August	1st to 10th	Day	2 2 1 3 2 3 3 3 4 5% 73%	4254
	11th to 20th	Day	2 2 1 4 3 3 4 3 5% 7% 66%	4026
	21st to end	Day	4 4 2 4 3 3 3 3 4 6% 64%	4213
September	1st to 10th	Day	3 2 1 3 2 2 3 3 4 7% 70%	2280
	11th to 20th	Day	4 4 2 6% 5% 4 5% 3 6% 8% 54%	2280
	21st to end	Day	6% 6% 2 5% 4 4 5% 3 6% 7% 53%	2028
October	1st to 10th	Day	5% 5% 2 4 3 4 5% 3 5% 6% 59%	3180
	11th to 20th	Day	4 4 2 7% 6% 6% 6% 5% 7% 9% 43%	3161
	21st to end	Day	5% 8% 3 9% 5% 7% 7% 5% 7% 9% 35%	3270
November	1st to 10th	Day	8% 10% 4 10% 7% 6% 6% 5% 7% 10% 28%	1721
	11th to 20th	Day	5% 12% 6% 10% 8% 7% 7% 6% 8% 8% 24%	1520
	21st to end	Day	5% 11% 5% 8% 6% 6% 5% 5% 9% 8% 31%	1520
December	1st to 10th	Day	7% 12% 5% 10% 8% 5% 5% 4 5% 8% 32%	1520
	11th to 20th	Day	6% 13% 5% 10% 7% 6% 8% 5% 9% 10% 21%	1928
	21st to end	Day	7% 13% 5% 13% 9% 7% 6% 5% 7% 7% 21%	2794
January	1st to 10th	Night	7% 12% 4 11% 8% 7% 7% 6% 8% 10% 19%	4406
	11th to 20th	Night	9% 15% 6% 11% 6% 5% 4 5% 6% 8% 24%	4420
	21st to end	Night	9% 12% 5% 12% 8% 7% 6% 5% 6% 8% 21%	4706
February	1st to 10th	Night	5% 12% 4 10% 6% 6% 5% 4 7% 9% 32%	2470
	11th to 20th	Night	7% 11% 3 7% 6% 5% 5% 4 7% 9% 36%	2402
	21st to end	Night	7% 10% 3 7% 6% 7% 6% 5% 8% 10% 31%	1908
March	1st to 10th	Night	3 8% 3 8% 6% 6% 6% 6% 9% 11% 33%	3688
	11th to 20th	Night	3 6% 3 6% 6% 4 5% 3 6% 8% 50%	3490
	21st to end	Night	6% 10% 3 10% 6% 7% 7% 6% 9% 10% 26%	3659
April	1st to 10th	Night	7% 9% 3 8% 6% 6% 6% 6% 8% 9% 32%	1900
	11th to 20th	Night	6% 7% 2 7% 6% 7% 6% 4 8% 9% 39%	1879
	21st to end	Night	6% 7% 3 6% 5% 5% 5% 5% 8% 9% 40%	1771
May	1st to 10th	Night	8% 9% 2 6% 4 3 4 3 5% 6% 50%	2540
	11th to 20th	Night	3 4 1 3 2 3 4 4 6% 7% 62%	2516
	21st to end	Night	4 4 2 5% 4 4 5% 4 8% 11% 49%	2762
June	1st to 10th	Night	9% 6% 2 7% 5% 4 5% 4 6% 9% 42%	1520
	11th to 20th	Night	6% 4 2 4 3 3 5% 5% 6% 9% 53%	1520
	21st to end	Night	3 3 1 5% 4 3 4 2 3 5% 67%	1520
July	1st to 10th	Night	1 1 1 1 2 1 2 2 2 85%	2540
	11th to 20th	Night	1 2 1 2 2 1 1 2 3 4 81%	2540
	21st to end	Night	2 1 2 1 1 2 1 3 4 83%	2761
August	1st to 10th	Night	2 3 1 2 2 2 3 2 4 6% 73%	2678
	11th to 20th	Night	2 1 1 3 2 3 3 3 4 5% 73%	2812
	21st to end	Night	3 2 1 3 2 2 2 3 4 5% 73%	3462
September	1st to 10th	Night	2 2 1 2 2 2 2 2 4 6% 74%	1900
	11th to 20th	Night	4 3 2 4 4 4 4 4 6% 7% 59%	1900
	21st to end	Night	4 5% 2 5% 3 3 4 3 6% 7% 58%	2148
October	1st to 10th	Night	4 3 1 3 2 3 3 3 6% 7% 63%	3800
	11th to 20th	Night	4 4 2 5% 4 6% 7% 5% 7% 10% 47%	3777
	21st to end	Night	6% 5% 2 7% 5% 5% 6% 6% 9% 10% 39%	4291
November	1st to 10th	Night	7% 8% 4 8% 6% 7% 7% 6% 7% 8% 33%	2560
	11th to 20th	Night	6% 10% 4 9% 7% 7% 6% 6% 8% 10% 29%	2660
	21st to end	Night	4 7% 4 8% 7% 6% 7% 6% 7% 10% 35%	2660
December	1st to 10th	Night	6% 11% 4 9% 6% 6% 6% 5% 7% 9% 32%	2660
	11th to 20th	Night	7% 13% 5% 11% 7% 6% 6% 6% 8% 9% 23%	3276
	21st to end	Night	7% 11% 4 11% 6% 6% 6% 4 7% 8% 28%	4862

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	57% 15% 16% 11% 1	2539
	11th to 20th	Day	59% 13% 14% 10% 3 1	2540
	21st to end	Day	63% 10% 13% 8% 4 1	2954
February	1st to 10th	Day	53% 13% 17% 13% 3	1710
	11th to 20th	Day	51% 11% 17% 15% 5%	1674
	21st to end	Day	54% 10% 14% 14% 7%	1544
March	1st to 10th	Day	49% 6% 16% 22% 6%	3185
	11th to 20th	Day	40% 8% 11% 31% 9%	3490
	21st to end	Day	58% 8% 16% 14% 4	3993
April	1st to 10th	Day	54% 8% 18% 16% 5%	2280
	11th to 20th	Day	52% 7% 16% 13% 10% 2	2252
	21st to end	Day	43% 9% 22% 17% 7% 2	2406
May	1st to 10th	Day	40% 4 15% 30% 12%	4420
	11th to 20th	Day	25% 3 14% 35% 20% 3	4380
	21st to end	Day	41% 11% 23% 20% 4	4814
June	1st to 10th	Day	42% 5% 19% 22% 10% 2	2660
	11th to 20th	Day	34% 6% 24% 23% 9% 3	2660
	21st to end	Day	23% 5% 15% 30% 21% 6%	2660
July	1st to 10th	Day	8% 3 8% 15% 20% 46%	4351
	11th to 20th	Day	10% 2 5% 11% 25% 48%	4345
	21st to end	Day	10% 3 8% 19% 34% 26%	4639
August	1st to 10th	Day	15% 3 9% 18% 33% 23%	4238
	11th to 20th	Day	16% 5% 10% 37% 25% 6%	4065
	21st to end	Day	22% 5% 12% 24% 31% 7%	4212
September	1st to 10th	Day	15% 3 14% 26% 28% 14%	2280
	11th to 20th	Day	28% 5% 15% 24% 20% 7%	2280
	21st to end	Day	32% 5% 15% 24% 19% 6%	2028
October	1st to 10th	Day	27% 6% 10% 23% 29% 6%	3180
	11th to 20th	Day	36% 10% 15% 24% 13% 1	3161
	21st to end	Day	41% 11% 16% 21% 9% 1	3270
November	1st to 10th	Day	51% 8% 16% 18% 5% 1	1721
	11th to 20th	Day	57% 13% 15% 11% 4	1520
	21st to end	Day	49% 11% 16% 12% 11% 1	1520
December	1st to 10th	Day	53% 10% 15% 14% 7% 1	1520
	11th to 20th	Day	57% 14% 15% 11% 2	1928
	21st to end	Day	61% 10% 14% 12% 2	2794
January	1st to 10th	Night	58% 15% 15% 10% 1	4406
	11th to 20th	Night	58% 10% 18% 11% 2 2	4420
	21st to end	Night	60% 13% 15% 8% 5% 1	4706
February	1st to 10th	Night	49% 14% 19% 14% 4	2470
	11th to 20th	Night	45% 12% 20% 14% 7% 1	2404
	21st to end	Night	47% 11% 18% 17% 6% 1	1908
March	1st to 10th	Night	41% 9% 18% 27% 5% 1	3688
	11th to 20th	Night	33% 5% 19% 32% 9% 1	3490
	21st to end	Night	50% 14% 22% 12% 2	3659
April	1st to 10th	Night	45% 12% 23% 14% 5%	1900
	11th to 20th	Night	41% 8% 24% 15% 9% 3	1879
	21st to end	Night	38% 10% 24% 17% 9% 2	1771
May	1st to 10th	Night	36% 4 17% 31% 11% 1	2540
	11th to 20th	Night	21% 6% 17% 34% 21% 2	2516
	21st to end	Night	29% 15% 36% 16% 4 1	2762
June	1st to 10th	Night	40% 7% 19% 23% 10% 2	1520
	11th to 20th	Night	28% 8% 27% 25% 9% 3	1520
	21st to end	Night	21% 4 17% 29% 21% 8%	1520
July	1st to 10th	Night	8% 2 9% 12% 18% 51%	2500
	11th to 20th	Night	10% 3 7% 10% 21% 50%	2492
	21st to end	Night	7% 2 8% 17% 32% 34%	2674
August	1st to 10th	Night	14% 3 9% 14% 36% 24%	2670
	11th to 20th	Night	13% 6% 11% 34% 26% 11%	2839
	21st to end	Night	15% 5% 14% 25% 30% 10%	3462
September	1st to 10th	Night	12% 3 16% 26% 27% 15%	1900
	11th to 20th	Night	25% 6% 16% 21% 20% 12%	1900
	21st to end	Night	26% 5% 18% 24% 19% 9%	2148
October	1st to 10th	Night	21% 7% 12% 26% 30% 4	3800
	11th to 20th	Night	31% 9% 17% 25% 14% 2	3777
	21st to end	Night	35% 13% 20% 17% 13% 1	4291
November	1st to 10th	Night	48% 10% 16% 18% 7% 1	2560
	11th to 20th	Night	49% 14% 18% 13% 5%	2660
	21st to end	Night	43% 13% 18% 16% 9% 1	2660
December	1st to 10th	Night	50% 12% 16% 16% 7%	2660
	11th to 20th	Night	55% 13% 18% 10% 4	3276
	21st to end	Night	52% 14% 19% 12% 3	4862

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	22% 26% 27% 14% 9% 1	180
	11th to 20th	Day	22% 20% 30% 20% 6% 2	180
	21st to end	Day	14% 25% 31% 20% 10% 1	293
February	1st to 10th	Day	21% 24% 32% 16% 6% 1	370
	11th to 20th	Day	21% 29% 28% 19% 4	365
	21st to end	Day	22% 26% 26% 21% 4	370
March	1st to 10th	Day	17% 26% 36% 15% 4 1	460
	11th to 20th	Day	18% 24% 29% 21% 8%	460
	21st to end	Day	24% 23% 31% 16% 5%	506
April	1st to 10th	Day	21% 26% 25% 20% 8% 1	460
	11th to 20th	Day	19% 29% 29% 14% 7% 2	452
	21st to end	Day	15% 26% 30% 22% 6% 2	460
May	1st to 10th	Day	16% 20% 32% 20% 9% 2	463
	11th to 20th	Day	19% 15% 29% 23% 10% 4	488
	21st to end	Day	13% 16% 27% 30% 11% 3	529
June	1st to 10th	Day	12% 21% 23% 27% 13% 4	490
	11th to 20th	Day	12% 26% 30% 22% 8% 2	490
	21st to end	Day	6% 14% 29% 32% 15% 3	490
July	1st to 10th	Day	3 11% 33% 37% 14% 2	486
	11th to 20th	Day	3 12% 31% 33% 16% 3	484
	21st to end	Day	2 6% 31% 37% 19% 5%	531
August	1st to 10th	Day	2 9% 29% 32% 20% 7%	487
	11th to 20th	Day	3 8% 26% 36% 21% 6%	477
	21st to end	Day	6% 12% 31% 31% 15% 6%	539
September	1st to 10th	Day	3 9% 31% 37% 17% 3	490
	11th to 20th	Day	7% 12% 30% 35% 14% 2	490
	21st to end	Day	11% 16% 30% 31% 11% 1	490
October	1st to 10th	Day	16% 13% 31% 25% 15%	490
	11th to 20th	Day	14% 19% 27% 25% 13% 2	490
	21st to end	Day	17% 27% 27% 17% 11% 2	436
November	1st to 10th	Day	21% 19% 27% 25% 7%	281
	11th to 20th	Day	16% 25% 24% 22% 11% 2	180
	21st to end	Day	16% 15% 33% 27% 7% 1	180
December	1st to 10th	Day	17% 19% 28% 21% 12% 3	180
	11th to 20th	Day	17% 26% 35% 17% 4 1	180
	21st to end	Day	21% 24% 25% 22% 8% 1	198
January	1st to 10th	Night	20% 19% 26% 22% 12% 1	760
	11th to 20th	Night	16% 15% 28% 26% 13% 2	760
	21st to end	Night	16% 13% 28% 30% 13% 2	836
February	1st to 10th	Night	15% 17% 29% 26% 12% 1	760
	11th to 20th	Night	16% 18% 28% 25% 12% 1	744
	21st to end	Night	19% 17% 30% 26% 7% 1	628
March	1st to 10th	Night	14% 19% 29% 26% 11% 1	760
	11th to 20th	Night	10% 17% 29% 31% 12% 1	760
	21st to end	Night	15% 20% 29% 24% 9% 2	836
April	1st to 10th	Night	15% 17% 29% 26% 11% 2	760
	11th to 20th	Night	11% 19% 32% 22% 13% 3	751
	21st to end	Night	11% 15% 35% 25% 13% 1	631
May	1st to 10th	Night	8% 17% 30% 28% 15% 2	380
	11th to 20th	Night	8% 11% 25% 33% 20% 3	374
	21st to end	Night	7% 9% 28% 38% 16% 2	411
June	1st to 10th	Night	14% 10% 26% 34% 15% 1	380
	11th to 20th	Night	8% 14% 32% 33% 12% 1	380
	21st to end	Night	6% 5% 25% 44% 18% 1	380
July	1st to 10th	Night	3 2 28% 48% 18% 1	370
	11th to 20th	Night	2 2 34% 46% 15% 2	368
	21st to end	Night	2 3 22% 49% 21% 3	416
August	1st to 10th	Night	3 1 21% 44% 26% 5%	462
	11th to 20th	Night	3 3 15% 38% 32% 9%	564
	21st to end	Night	3 5% 26% 38% 23% 5%	813
September	1st to 10th	Night	3 5% 22% 40% 26% 4	760
	11th to 20th	Night	5% 5% 22% 33% 29% 5%	760
	21st to end	Night	8% 8% 23% 33% 25% 3	760
October	1st to 10th	Night	10% 7% 27% 32% 19% 4	760
	11th to 20th	Night	9% 11% 25% 30% 20% 4	760
	21st to end	Night	13% 17% 25% 27% 14% 4	836
November	1st to 10th	Night	14% 13% 31% 31% 10% 1	778
	11th to 20th	Night	16% 21% 26% 25% 11% 1	760
	21st to end	Night	10% 16% 28% 29% 14% 2	760
December	1st to 10th	Night	14% 14% 28% 26% 16% 1	760
	11th to 20th	Night	16% 15% 32% 24% 11% 1	760
	21st to end	Night	18% 19% 32% 22% 8% 1	836

Page generated at 2024-11-07 03:55:45. Version ac07

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