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 2024-01-13.

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	6% 7% 3 6% 6% 4 5% 5% 6% 8% 43%	74767
	Night	6% 7% 3 6% 6% 4 5% 6% 6% 9% 43%	74980
Transparency	Day	40% 7% 15% 19% 14% 5%	74470
	Night	39% 9% 18% 17% 12% 5%	74798
Seeing	Day	13% 18% 29% 26% 11% 2	13458
	Night	11% 13% 27% 30% 16% 2	22581

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	10% 13% 5% 9% 9% 5% 7% 6% 7% 10% 19%	1519
	11th to 20th	Day	7% 11% 5% 9% 9% 5% 8% 6% 7% 10% 24%	1456
	21st to end	Day	6% 11% 4 9% 9% 4 6% 7% 7% 10% 27%	1674
February	1st to 10th	Day	8% 12% 4 7% 8% 5% 6% 7% 7% 10% 27%	1620
	11th to 20th	Day	7% 10% 5% 6% 5% 4 6% 8% 9% 10% 29%	1575
	21st to end	Day	7% 10% 6% 10% 7% 5% 6% 5% 6% 8% 28%	1456
March	1st to 10th	Day	6% 13% 6% 8% 9% 5% 7% 6% 8% 9% 24%	1821
	11th to 20th	Day	5% 13% 5% 9% 10% 6% 5% 7% 6% 9% 24%	1980
	21st to end	Day	8% 14% 6% 10% 9% 4 6% 6% 6% 7% 22%	2269
April	1st to 10th	Day	9% 9% 4 9% 9% 5% 6% 6% 6% 9% 27%	2160
	11th to 20th	Day	8% 12% 5% 9% 7% 4 5% 6% 6% 7% 30%	2129
	21st to end	Day	6% 8% 3 7% 7% 4 7% 6% 7% 10% 37%	2279
May	1st to 10th	Day	5% 6% 3 6% 7% 4 6% 5% 6% 7% 44%	2520
	11th to 20th	Day	9% 7% 3 7% 7% 4 5% 6% 7% 7% 37%	2477
	21st to end	Day	9% 7% 3 6% 6% 4 6% 6% 6% 9% 37%	2723
June	1st to 10th	Day	9% 6% 3 6% 6% 4 5% 6% 6% 9% 39%	2520
	11th to 20th	Day	5% 5% 3 6% 6% 3 5% 5% 7% 9% 45%	2520
	21st to end	Day	4 3 2 4 4 2 4 4 5% 7% 61%	2520
July	1st to 10th	Day	2 2 1 2 2 2 3 3 4 6% 72%	2520
	11th to 20th	Day	3 2 1 3 3 2 3 3 3 5% 72%	2520
	21st to end	Day	2 2 1 2 1 1 2 1 2 4 83%	2741
August	1st to 10th	Day	2 2 1 2 2 2 3 3 4 6% 74%	2426
	11th to 20th	Day	2 2 1 3 2 2 3 3 4 5% 73%	2298
	21st to end	Day	2 3 1 3 3 2 3 4 4 7% 68%	2396
September	1st to 10th	Day	3 1 1 3 3 2 3 4 4 7% 70%	2160
	11th to 20th	Day	4 3 2 5% 6% 2 5% 4 6% 8% 54%	2160
	21st to end	Day	6% 6% 2 5% 5% 3 5% 4 5% 7% 52%	1922
October	1st to 10th	Day	9% 7% 3 5% 5% 3 5% 4 5% 7% 47%	1800
	11th to 20th	Day	6% 6% 2 6% 7% 4 5% 5% 7% 9% 43%	1800
	21st to end	Day	8% 8% 2 7% 7% 4 5% 6% 6% 8% 39%	1883
November	1st to 10th	Day	8% 9% 4 9% 8% 5% 6% 6% 7% 10% 28%	1641
	11th to 20th	Day	5% 11% 7% 9% 9% 5% 8% 7% 8% 9% 24%	1520
	21st to end	Day	5% 9% 6% 8% 6% 4 5% 7% 9% 9% 31%	1520
December	1st to 10th	Day	7% 11% 5% 9% 9% 4 6% 5% 6% 8% 32%	1520
	11th to 20th	Day	6% 12% 5% 9% 9% 4 8% 7% 9% 10% 21%	1928
	21st to end	Day	7% 13% 5% 12% 10% 5% 7% 6% 7% 7% 21%	2794
January	1st to 10th	Night	7% 12% 5% 8% 10% 5% 7% 7% 7% 11% 20%	2646
	11th to 20th	Night	6% 9% 5% 10% 9% 5% 6% 8% 7% 11% 25%	2548
	21st to end	Night	7% 9% 4 8% 9% 5% 6% 7% 6% 9% 30%	2681
February	1st to 10th	Night	5% 11% 5% 8% 7% 4 6% 6% 7% 10% 32%	2340
	11th to 20th	Night	7% 9% 3 6% 7% 3 5% 5% 7% 9% 38%	2272
	21st to end	Night	8% 9% 4 6% 7% 5% 6% 7% 7% 11% 31%	1798
March	1st to 10th	Night	6% 10% 4 7% 7% 4 7% 7% 7% 10% 31%	2138
	11th to 20th	Night	5% 9% 4 7% 9% 4 7% 6% 8% 11% 30%	1980
	21st to end	Night	7% 9% 5% 9% 8% 5% 7% 7% 7% 10% 27%	2086
April	1st to 10th	Night	8% 8% 3 7% 7% 5% 6% 7% 8% 10% 32%	1800
	11th to 20th	Night	6% 6% 3 6% 6% 6% 7% 5% 8% 9% 39%	1779
	21st to end	Night	6% 6% 3 5% 5% 4 6% 5% 7% 10% 41%	1678
May	1st to 10th	Night	4 5% 2 5% 5% 3 6% 6% 6% 9% 48%	1440
	11th to 20th	Night	6% 7% 2 4 5% 2 5% 6% 10% 10% 42%	1416
	21st to end	Night	6% 5% 3 4 4 4 8% 6% 7% 11% 43%	1552
June	1st to 10th	Night	9% 6% 3 6% 5% 4 4 5% 6% 9% 42%	1440
	11th to 20th	Night	6% 4 2 4 4 2 5% 5% 6% 9% 53%	1440
	21st to end	Night	4 3 1 5% 4 2 3 3 3 4 67%	1440
July	1st to 10th	Night	3 2 1 2 3 2 3 3 4 4 75%	1440
	11th to 20th	Night	2 1 1 1 2 1 2 4 4 6% 77%	1440
	21st to end	Night	2 1 2 2 1 2 2 3 4 82%	1576
August	1st to 10th	Night	2 2 1 1 2 1 3 3 4 5% 76%	1511
	11th to 20th	Night	2 1 1 2 2 2 3 3 3 4 77%	1602
	21st to end	Night	2 2 1 2 2 2 2 3 4 6% 75%	1958
September	1st to 10th	Night	2 2 1 2 2 1 2 3 4 6% 75%	1800
	11th to 20th	Night	4 3 2 4 5% 3 4 5% 6% 6% 59%	1800
	21st to end	Night	5% 5% 2 4 3 2 4 4 6% 8% 57%	2034
October	1st to 10th	Night	7% 5% 3 5% 4 3 3 4 5% 7% 55%	2160
	11th to 20th	Night	5% 5% 2 5% 5% 3 5% 5% 6% 9% 48%	2160
	21st to end	Night	8% 6% 3 6% 4 3 5% 6% 6% 8% 45%	2471
November	1st to 10th	Night	8% 8% 4 7% 7% 5% 6% 8% 7% 8% 33%	2436
	11th to 20th	Night	6% 9% 4 8% 7% 5% 6% 8% 8% 10% 29%	2660
	21st to end	Night	4 6% 4 7% 7% 4 7% 8% 7% 10% 35%	2660
December	1st to 10th	Night	7% 10% 5% 8% 6% 4 6% 6% 7% 9% 32%	2660
	11th to 20th	Night	7% 12% 5% 9% 9% 5% 6% 7% 8% 9% 23%	3276
	21st to end	Night	7% 10% 5% 10% 7% 5% 6% 6% 7% 8% 29%	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	61% 14% 12% 10% 2	1519
	11th to 20th	Day	55% 12% 16% 9% 5% 3	1456
	21st to end	Day	53% 11% 15% 12% 8% 2	1674
February	1st to 10th	Day	52% 14% 17% 13% 3	1620
	11th to 20th	Day	49% 11% 17% 16% 6%	1584
	21st to end	Day	55% 10% 14% 13% 7%	1456
March	1st to 10th	Day	55% 8% 19% 12% 5%	1821
	11th to 20th	Day	57% 8% 14% 16% 4	1980
	21st to end	Day	60% 10% 16% 13% 1	2269
April	1st to 10th	Day	54% 8% 18% 16% 5%	2160
	11th to 20th	Day	53% 7% 17% 13% 9% 2	2132
	21st to end	Day	42% 9% 22% 17% 8% 2	2279
May	1st to 10th	Day	39% 5% 19% 27% 9%	2520
	11th to 20th	Day	44% 6% 19% 22% 9% 1	2480
	21st to end	Day	43% 7% 22% 21% 6%	2724
June	1st to 10th	Day	42% 5% 20% 22% 10% 1	2520
	11th to 20th	Day	36% 6% 24% 23% 8% 2	2520
	21st to end	Day	23% 5% 15% 30% 21% 6%	2520
July	1st to 10th	Day	14% 5% 14% 24% 28% 15%	2451
	11th to 20th	Day	17% 3 7% 18% 34% 21%	2445
	21st to end	Day	9% 2 6% 21% 41% 21%	2589
August	1st to 10th	Day	13% 4 12% 27% 32% 12%	2409
	11th to 20th	Day	15% 3 10% 27% 35% 11%	2298
	21st to end	Day	17% 4 13% 29% 29% 8%	2396
September	1st to 10th	Day	15% 3 15% 26% 26% 14%	2160
	11th to 20th	Day	29% 5% 15% 23% 21% 8%	2160
	21st to end	Day	33% 5% 15% 22% 19% 7%	1922
October	1st to 10th	Day	38% 6% 12% 24% 16% 5%	1800
	11th to 20th	Day	39% 7% 17% 18% 17% 2	1800
	21st to end	Day	45% 9% 13% 20% 12% 1	1883
November	1st to 10th	Day	52% 8% 16% 18% 5% 1	1641
	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	59% 15% 15% 8% 2	2646
	11th to 20th	Night	53% 11% 18% 11% 4 3	2548
	21st to end	Night	50% 12% 16% 13% 8% 1	2681
February	1st to 10th	Night	48% 14% 19% 15% 3	2340
	11th to 20th	Night	43% 13% 21% 14% 8% 1	2274
	21st to end	Night	48% 11% 17% 17% 7% 1	1798
March	1st to 10th	Night	46% 11% 19% 17% 5% 1	2138
	11th to 20th	Night	48% 7% 22% 18% 4 1	1980
	21st to end	Night	51% 12% 22% 11% 3	2086
April	1st to 10th	Night	46% 11% 23% 15% 6%	1800
	11th to 20th	Night	42% 8% 25% 14% 8% 3	1779
	21st to end	Night	38% 10% 25% 16% 9% 2	1678
May	1st to 10th	Night	33% 8% 23% 25% 10% 1	1440
	11th to 20th	Night	34% 9% 25% 21% 9% 2	1416
	21st to end	Night	35% 11% 26% 19% 8% 1	1552
June	1st to 10th	Night	39% 8% 19% 23% 9% 2	1440
	11th to 20th	Night	28% 8% 29% 25% 8% 3	1440
	21st to end	Night	22% 4 17% 29% 20% 8%	1440
July	1st to 10th	Night	14% 3 16% 21% 25% 21%	1400
	11th to 20th	Night	10% 4 12% 17% 29% 28%	1392
	21st to end	Night	8% 2 8% 16% 37% 30%	1488
August	1st to 10th	Night	13% 3 13% 22% 32% 17%	1503
	11th to 20th	Night	13% 3 11% 23% 33% 16%	1602
	21st to end	Night	12% 4 12% 28% 34% 10%	1958
September	1st to 10th	Night	12% 3 17% 27% 26% 16%	1800
	11th to 20th	Night	25% 6% 16% 20% 21% 12%	1800
	21st to end	Night	27% 5% 18% 22% 19% 9%	2034
October	1st to 10th	Night	32% 5% 15% 23% 20% 5%	2160
	11th to 20th	Night	34% 8% 16% 19% 18% 4	2160
	21st to end	Night	38% 9% 16% 18% 17% 2	2471
November	1st to 10th	Night	49% 9% 16% 18% 6% 1	2436
	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% 25% 28% 14% 9% 1	180
	11th to 20th	Day	22% 20% 31% 18% 6% 2	164
	21st to end	Day	14% 23% 30% 21% 11% 1	266
February	1st to 10th	Day	22% 24% 31% 17% 6%	340
	11th to 20th	Day	21% 28% 29% 19% 3	335
	21st to end	Day	23% 25% 26% 22% 4	336
March	1st to 10th	Day	17% 26% 37% 14% 5% 1	420
	11th to 20th	Day	19% 25% 28% 22% 7%	420
	21st to end	Day	25% 22% 30% 17% 5%	462
April	1st to 10th	Day	22% 25% 25% 20% 8% 1	420
	11th to 20th	Day	20% 28% 28% 14% 7% 2	412
	21st to end	Day	15% 25% 31% 21% 6% 2	420
May	1st to 10th	Day	15% 19% 33% 21% 9% 2	423
	11th to 20th	Day	20% 16% 28% 22% 10% 3	448
	21st to end	Day	12% 16% 27% 31% 11% 3	485
June	1st to 10th	Day	12% 21% 24% 26% 13% 4	450
	11th to 20th	Day	11% 25% 30% 23% 9% 2	450
	21st to end	Day	6% 13% 29% 34% 16% 3	450
July	1st to 10th	Day	3 9% 32% 39% 15% 2	446
	11th to 20th	Day	4 12% 30% 34% 17% 3	444
	21st to end	Day	2 5% 30% 38% 19% 5%	487
August	1st to 10th	Day	2 8% 28% 33% 20% 8%	447
	11th to 20th	Day	3 7% 25% 37% 22% 7%	437
	21st to end	Day	5% 11% 33% 31% 15% 6%	495
September	1st to 10th	Day	3 10% 31% 35% 16% 4	450
	11th to 20th	Day	8% 11% 29% 36% 15% 2	450
	21st to end	Day	12% 16% 28% 32% 12% 1	450
October	1st to 10th	Day	16% 12% 30% 25% 15%	450
	11th to 20th	Day	14% 19% 24% 27% 14% 2	450
	21st to end	Day	17% 26% 26% 18% 12% 2	398
November	1st to 10th	Day	19% 20% 28% 26% 7%	255
	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% 29% 26% 13% 2	728
	21st to end	Night	15% 13% 27% 30% 13% 2	792
February	1st to 10th	Night	15% 17% 30% 25% 13% 1	720
	11th to 20th	Night	15% 18% 28% 26% 13% 1	704
	21st to end	Night	19% 16% 30% 26% 8% 1	592
March	1st to 10th	Night	14% 18% 29% 26% 12% 1	720
	11th to 20th	Night	11% 17% 30% 31% 11% 1	720
	21st to end	Night	16% 20% 29% 24% 9% 2	792
April	1st to 10th	Night	16% 16% 28% 26% 12% 2	720
	11th to 20th	Night	11% 19% 32% 22% 13% 4	711
	21st to end	Night	11% 14% 36% 24% 14% 2	598
May	1st to 10th	Night	8% 15% 30% 29% 16% 2	360
	11th to 20th	Night	8% 10% 24% 33% 21% 3	354
	21st to end	Night	7% 8% 28% 37% 17% 2	389
June	1st to 10th	Night	13% 10% 26% 34% 16% 1	360
	11th to 20th	Night	8% 13% 33% 34% 12% 1	360
	21st to end	Night	6% 5% 24% 45% 19% 1	360
July	1st to 10th	Night	3 2 26% 49% 19% 1	350
	11th to 20th	Night	2 1 32% 47% 15% 2	348
	21st to end	Night	2 3 21% 50% 21% 3	394
August	1st to 10th	Night	3 1 20% 45% 27% 5%	437
	11th to 20th	Night	3 2 14% 37% 34% 10%	534
	21st to end	Night	3 5% 26% 39% 24% 5%	770
September	1st to 10th	Night	3 5% 22% 41% 25% 5%	720
	11th to 20th	Night	5% 4 21% 34% 31% 6%	720
	21st to end	Night	9% 7% 22% 34% 25% 3	720
October	1st to 10th	Night	11% 7% 27% 31% 20% 4	720
	11th to 20th	Night	9% 10% 25% 29% 22% 5%	720
	21st to end	Night	13% 17% 24% 28% 15% 4	792
November	1st to 10th	Night	14% 12% 32% 32% 10% 1	740
	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 2024-01-09 22:25:00. Version ac07

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