Louisiana Tech University Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Louisiana Tech University Observatory clear sky chart from 2005-11-06 to 2024-01-15.

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	13% 6% 3 5% 5% 3 5% 5% 5% 7% 43%	75043
	Night	12% 5% 2 4 4 2 4 4 5% 7% 50%	74752
Transparency	Day	39% 7% 11% 19% 18% 6%	74768
	Night	34% 6% 11% 20% 21% 8%	74548
Seeing	Day	14% 9% 22% 26% 21% 7%	14002
	Night	15% 9% 25% 31% 18% 3	23913

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	18% 9% 3 4 3 2 3 3 4 5% 45%	1707
	11th to 20th	Day	22% 8% 2 6% 5% 2 3 3 3 5% 43%	1656
	21st to end	Day	17% 9% 3 4 3 2 3 3 4 4 48%	1782
February	1st to 10th	Day	21% 8% 3 5% 5% 2 3 4 4 5% 40%	1620
	11th to 20th	Day	20% 9% 3 5% 4 3 3 3 3 5% 41%	1729
	21st to end	Day	23% 8% 3 7% 4 3 4 3 3 5% 37%	1593
March	1st to 10th	Day	19% 7% 3 5% 4 3 5% 4 5% 6% 38%	1980
	11th to 20th	Day	18% 7% 4 6% 5% 3 5% 4 4 7% 39%	1980
	21st to end	Day	14% 7% 3 7% 5% 3 4 4 5% 5% 44%	2178
April	1st to 10th	Day	12% 6% 3 6% 6% 4 5% 5% 6% 6% 44%	2126
	11th to 20th	Day	17% 7% 3 6% 4 4 4 4 4 7% 40%	2134
	21st to end	Day	12% 5% 3 5% 5% 3 4 5% 5% 7% 45%	2160
May	1st to 10th	Day	13% 7% 3 6% 5% 3 5% 5% 5% 7% 41%	2160
	11th to 20th	Day	11% 6% 3 6% 6% 4 5% 5% 6% 8% 40%	2188
	21st to end	Day	9% 4 2 5% 6% 3 8% 6% 6% 10% 41%	2531
June	1st to 10th	Day	8% 5% 2 6% 7% 5% 6% 6% 7% 10% 37%	2340
	11th to 20th	Day	6% 4 3 5% 6% 4 6% 6% 6% 9% 43%	2340
	21st to end	Day	7% 4 2 5% 6% 4 7% 7% 8% 9% 41%	2340
July	1st to 10th	Day	8% 4 2 6% 7% 6% 10% 6% 8% 11% 32%	2340
	11th to 20th	Day	8% 4 2 4 7% 5% 7% 7% 8% 12% 38%	2340
	21st to end	Day	8% 4 3 5% 7% 5% 7% 7% 8% 12% 36%	2546
August	1st to 10th	Day	6% 3 2 5% 6% 4 6% 6% 7% 10% 44%	2292
	11th to 20th	Day	8% 4 2 5% 6% 4 6% 5% 8% 10% 42%	2125
	21st to end	Day	12% 4 3 5% 5% 4 6% 6% 6% 10% 40%	2376
September	1st to 10th	Day	8% 5% 2 4 7% 4 6% 5% 5% 8% 46%	2160
	11th to 20th	Day	14% 4 2 5% 6% 3 6% 5% 5% 9% 41%	2132
	21st to end	Day	8% 4 2 5% 4 3 4 4 5% 6% 56%	1890
October	1st to 10th	Day	7% 4 1 4 4 3 3 4 4 7% 59%	1800
	11th to 20th	Day	12% 5% 3 4 4 3 3 3 4 6% 55%	1800
	21st to end	Day	15% 5% 2 4 4 3 3 3 3 4 53%	1980
November	1st to 10th	Day	12% 4 2 4 4 2 4 3 4 6% 54%	1858
	11th to 20th	Day	12% 6% 2 5% 4 3 4 4 4 5% 54%	1900
	21st to end	Day	18% 6% 2 4 6% 3 3 4 4 5% 44%	1900
December	1st to 10th	Day	16% 8% 3 6% 4 2 4 5% 4 5% 43%	1764
	11th to 20th	Day	16% 10% 3 4 4 3 4 4 3 5% 42%	2161
	21st to end	Day	15% 8% 3 6% 6% 3 4 4 4 5% 42%	3135
January	1st to 10th	Night	17% 6% 2 5% 3 2 3 4 4 5% 49%	2458
	11th to 20th	Night	19% 7% 3 5% 4 2 3 4 3 6% 45%	2393
	21st to end	Night	18% 7% 3 5% 3 2 3 3 3 5% 47%	2574
February	1st to 10th	Night	16% 7% 3 6% 4 3 4 3 4 6% 45%	2340
	11th to 20th	Night	20% 7% 3 5% 5% 3 3 3 4 5% 44%	2116
	21st to end	Night	21% 9% 2 4 5% 2 3 4 4 4 42%	1678
March	1st to 10th	Night	16% 6% 3 6% 6% 2 4 3 5% 6% 44%	1980
	11th to 20th	Night	16% 6% 2 5% 5% 3 4 4 5% 8% 41%	1980
	21st to end	Night	14% 6% 2 5% 4 3 4 4 4 6% 47%	2178
April	1st to 10th	Night	11% 4 3 4 3 2 5% 4 5% 8% 51%	1832
	11th to 20th	Night	13% 7% 2 5% 5% 2 4 4 4 7% 47%	1775
	21st to end	Night	9% 6% 2 5% 4 2 4 4 5% 7% 52%	1800
May	1st to 10th	Night	11% 5% 2 5% 4 2 4 4 6% 7% 49%	1800
	11th to 20th	Night	11% 5% 2 4 5% 2 5% 4 6% 9% 48%	1701
	21st to end	Night	7% 3 2 5% 5% 3 5% 5% 5% 10% 49%	1745
June	1st to 10th	Night	7% 3 2 4 5% 3 5% 5% 6% 12% 49%	1620
	11th to 20th	Night	4 3 1 3 4 2 4 5% 7% 11% 56%	1620
	21st to end	Night	6% 4 2 4 5% 3 5% 5% 5% 8% 53%	1620
July	1st to 10th	Night	5% 3 2 4 6% 3 5% 6% 9% 11% 46%	1620
	11th to 20th	Night	6% 2 1 3 4 3 5% 6% 8% 13% 50%	1620
	21st to end	Night	4 2 2 3 5% 3 5% 6% 7% 15% 49%	1772
August	1st to 10th	Night	4 2 1 3 3 3 5% 5% 7% 13% 55%	1642
	11th to 20th	Night	7% 2 2 4 3 3 4 5% 8% 12% 50%	1776
	21st to end	Night	9% 4 2 5% 4 3 6% 5% 7% 10% 46%	1980
September	1st to 10th	Night	7% 5% 2 5% 6% 3 4 4 5% 7% 53%	1800
	11th to 20th	Night	10% 5% 2 5% 5% 3 4 5% 5% 7% 48%	1823
	21st to end	Night	8% 4 2 4 4 2 3 4 4 6% 59%	2052
October	1st to 10th	Night	7% 3 1 3 4 2 4 4 4 7% 61%	2160
	11th to 20th	Night	11% 4 2 4 3 2 4 3 4 5% 58%	2160
	21st to end	Night	13% 5% 1 3 4 3 3 3 4 5% 56%	2376
November	1st to 10th	Night	11% 4 2 4 3 3 3 3 4 6% 57%	2220
	11th to 20th	Night	12% 5% 3 3 4 2 3 3 4 5% 56%	2280
	21st to end	Night	15% 6% 3 5% 4 2 4 4 4 5% 48%	2280
December	1st to 10th	Night	17% 7% 3 5% 3 2 3 4 5% 6% 44%	2413
	11th to 20th	Night	15% 8% 2 6% 5% 2 4 4 4 4 47%	3036
	21st to end	Night	16% 9% 2 5% 4 2 3 3 4 5% 46%	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	43% 3 6% 19% 22% 8%	1708
	11th to 20th	Day	47% 3 5% 17% 21% 7%	1656
	21st to end	Day	41% 3 4 18% 26% 8%	1782
February	1st to 10th	Day	47% 5% 6% 17% 14% 11%	1620
	11th to 20th	Day	48% 4 5% 16% 19% 7%	1739
	21st to end	Day	51% 4 6% 11% 19% 9%	1593
March	1st to 10th	Day	47% 5% 9% 14% 17% 9%	1980
	11th to 20th	Day	46% 6% 8% 16% 18% 6%	1980
	21st to end	Day	43% 5% 8% 17% 24% 3	2178
April	1st to 10th	Day	39% 6% 9% 22% 16% 7%	2126
	11th to 20th	Day	45% 6% 9% 14% 19% 8%	2134
	21st to end	Day	38% 5% 11% 21% 23% 3	2160
May	1st to 10th	Day	43% 7% 9% 19% 16% 5%	2160
	11th to 20th	Day	40% 8% 14% 23% 14% 2	2192
	21st to end	Day	37% 8% 16% 24% 14% 1	2531
June	1st to 10th	Day	40% 10% 15% 21% 13% 2	2340
	11th to 20th	Day	34% 9% 15% 24% 16% 2	2340
	21st to end	Day	36% 11% 16% 21% 14% 3	2340
July	1st to 10th	Day	40% 12% 20% 20% 8% 1	2276
	11th to 20th	Day	34% 11% 21% 21% 12% 1	2271
	21st to end	Day	38% 11% 20% 21% 9% 1	2405
August	1st to 10th	Day	32% 12% 19% 25% 12% 1	2278
	11th to 20th	Day	35% 10% 17% 22% 14% 2	2125
	21st to end	Day	38% 10% 16% 21% 12% 3	2376
September	1st to 10th	Day	36% 9% 12% 19% 17% 7%	2160
	11th to 20th	Day	39% 9% 11% 16% 19% 6%	2132
	21st to end	Day	29% 5% 10% 20% 25% 10%	1890
October	1st to 10th	Day	26% 5% 9% 23% 23% 14%	1800
	11th to 20th	Day	32% 3 6% 19% 26% 14%	1800
	21st to end	Day	36% 4 6% 15% 27% 12%	1980
November	1st to 10th	Day	32% 6% 8% 18% 26% 10%	1858
	11th to 20th	Day	35% 4 6% 16% 27% 12%	1900
	21st to end	Day	43% 4 7% 16% 22% 8%	1900
December	1st to 10th	Day	43% 6% 8% 18% 16% 9%	1764
	11th to 20th	Day	45% 4 5% 12% 27% 6%	2159
	21st to end	Day	44% 5% 6% 14% 25% 6%	3135
January	1st to 10th	Night	38% 4 7% 17% 26% 8%	2458
	11th to 20th	Night	42% 4 8% 18% 21% 8%	2393
	21st to end	Night	42% 3 5% 15% 25% 10%	2574
February	1st to 10th	Night	42% 4 7% 18% 20% 9%	2340
	11th to 20th	Night	45% 4 5% 17% 21% 8%	2117
	21st to end	Night	47% 5% 6% 12% 16% 14%	1678
March	1st to 10th	Night	41% 4 8% 15% 21% 10%	1980
	11th to 20th	Night	41% 7% 10% 16% 18% 7%	1980
	21st to end	Night	39% 5% 8% 18% 24% 5%	2178
April	1st to 10th	Night	32% 6% 12% 21% 19% 10%	1832
	11th to 20th	Night	37% 5% 9% 17% 20% 12%	1775
	21st to end	Night	31% 6% 9% 24% 25% 5%	1800
May	1st to 10th	Night	35% 6% 10% 21% 19% 9%	1800
	11th to 20th	Night	32% 7% 13% 25% 20% 2	1702
	21st to end	Night	29% 8% 16% 27% 20% 1	1746
June	1st to 10th	Night	27% 11% 16% 26% 19% 1	1620
	11th to 20th	Night	21% 8% 20% 29% 20% 3	1620
	21st to end	Night	27% 10% 16% 24% 20% 3	1620
July	1st to 10th	Night	27% 12% 25% 25% 10% 2	1575
	11th to 20th	Night	20% 11% 25% 28% 14% 2	1566
	21st to end	Night	21% 11% 25% 28% 12% 1	1673
August	1st to 10th	Night	19% 7% 27% 30% 15% 1	1632
	11th to 20th	Night	24% 10% 21% 24% 16% 4	1776
	21st to end	Night	30% 10% 18% 22% 16% 3	1980
September	1st to 10th	Night	30% 8% 14% 20% 20% 8%	1800
	11th to 20th	Night	34% 8% 11% 17% 21% 9%	1823
	21st to end	Night	26% 6% 10% 21% 24% 13%	2052
October	1st to 10th	Night	23% 5% 11% 21% 23% 17%	2160
	11th to 20th	Night	30% 4 7% 15% 28% 16%	2160
	21st to end	Night	31% 4 7% 16% 25% 16%	2376
November	1st to 10th	Night	30% 4 8% 18% 26% 14%	2220
	11th to 20th	Night	32% 5% 8% 16% 27% 13%	2280
	21st to end	Night	40% 4 6% 17% 24% 10%	2280
December	1st to 10th	Night	40% 6% 10% 17% 20% 7%	2413
	11th to 20th	Night	42% 4 6% 12% 25% 11%	3037
	21st to end	Night	41% 5% 6% 19% 24% 6%	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	24% 20% 39% 13% 3	270
	11th to 20th	Day	29% 18% 36% 12% 4 1	252
	21st to end	Day	25% 26% 31% 15% 3	264
February	1st to 10th	Day	28% 17% 37% 12% 5% 1	240
	11th to 20th	Day	35% 19% 37% 9%	240
	21st to end	Day	36% 29% 26% 6% 2	198
March	1st to 10th	Day	28% 21% 32% 15% 3	240
	11th to 20th	Day	22% 30% 34% 13% 1	240
	21st to end	Day	21% 25% 34% 16% 4	264
April	1st to 10th	Day	20% 19% 35% 19% 7%	386
	11th to 20th	Day	25% 13% 32% 18% 10% 1	412
	21st to end	Day	16% 15% 33% 25% 9% 1	420
May	1st to 10th	Day	16% 10% 35% 28% 11% 1	423
	11th to 20th	Day	14% 6% 27% 29% 18% 5%	511
	21st to end	Day	8% 5% 24% 38% 19% 5%	679
June	1st to 10th	Day	10% 3 15% 38% 27% 8%	630
	11th to 20th	Day	5% 3 18% 39% 29% 6%	630
	21st to end	Day	8% 2 17% 31% 31% 11%	630
July	1st to 10th	Day	7% 2 11% 34% 34% 12%	621
	11th to 20th	Day	5% 2 8% 31% 40% 14%	618
	21st to end	Day	5% 1 7% 35% 40% 12%	684
August	1st to 10th	Day	6% 2 8% 28% 41% 16%	590
	11th to 20th	Day	8% 1 7% 27% 43% 15%	439
	21st to end	Day	14% 2 4 21% 37% 22%	495
September	1st to 10th	Day	7% 2 10% 28% 38% 15%	450
	11th to 20th	Day	11% 3 11% 26% 34% 14%	422
	21st to end	Day	10% 3 10% 37% 29% 10%	270
October	1st to 10th	Day	7% 4 21% 40% 20% 6%	270
	11th to 20th	Day	10% 9% 34% 26% 17% 4	270
	21st to end	Day	22% 11% 31% 22% 11% 3	297
November	1st to 10th	Day	17% 10% 27% 30% 13% 3	270
	11th to 20th	Day	13% 16% 39% 23% 9% 1	270
	21st to end	Day	21% 14% 37% 19% 7% 1	270
December	1st to 10th	Day	18% 14% 42% 18% 6% 2	270
	11th to 20th	Day	28% 16% 31% 21% 4	270
	21st to end	Day	23% 19% 39% 13% 4 2	297
January	1st to 10th	Night	21% 16% 34% 23% 5%	950
	11th to 20th	Night	23% 15% 30% 25% 7%	921
	21st to end	Night	21% 15% 36% 25% 3	990
February	1st to 10th	Night	22% 14% 34% 26% 4	900
	11th to 20th	Night	26% 16% 34% 22% 2	721
	21st to end	Night	29% 15% 34% 20% 2	494
March	1st to 10th	Night	20% 14% 35% 26% 5%	540
	11th to 20th	Night	18% 15% 35% 27% 4 1	540
	21st to end	Night	16% 13% 37% 27% 8%	594
April	1st to 10th	Night	14% 12% 41% 25% 7%	540
	11th to 20th	Night	17% 13% 33% 26% 10% 1	533
	21st to end	Night	13% 11% 35% 30% 11% 1	540
May	1st to 10th	Night	11% 7% 34% 36% 11% 1	540
	11th to 20th	Night	11% 5% 31% 32% 19% 2	531
	21st to end	Night	7% 3 21% 41% 24% 4	584
June	1st to 10th	Night	7% 2 11% 43% 32% 5%	540
	11th to 20th	Night	4 2 13% 40% 37% 3	540
	21st to end	Night	6% 1 14% 33% 37% 9%	540
July	1st to 10th	Night	5% 2 8% 35% 41% 10%	525
	11th to 20th	Night	4 1 7% 32% 44% 11%	522
	21st to end	Night	4 1 7% 38% 39% 11%	591
August	1st to 10th	Night	3 1 5% 33% 47% 10%	537
	11th to 20th	Night	7% 1 5% 38% 43% 7%	534
	21st to end	Night	10% 1 7% 29% 42% 11%	594
September	1st to 10th	Night	8% 1 7% 38% 38% 8%	540
	11th to 20th	Night	12% 1 11% 31% 36% 8%	540
	21st to end	Night	9% 3 11% 39% 33% 5%	612
October	1st to 10th	Night	8% 3 16% 36% 31% 5%	720
	11th to 20th	Night	12% 6% 24% 36% 20% 2	720
	21st to end	Night	16% 6% 26% 32% 17% 2	792
November	1st to 10th	Night	12% 6% 26% 35% 19% 2	740
	11th to 20th	Night	13% 10% 28% 36% 13% 1	760
	21st to end	Night	18% 11% 29% 29% 12%	760
December	1st to 10th	Night	20% 12% 31% 28% 8%	893
	11th to 20th	Night	23% 13% 30% 27% 7%	950
	21st to end	Night	23% 17% 28% 26% 6%	1045

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