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 2024-06-30.

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	14% 7% 2 6% 4 4 4 4 5% 7% 42%	89592
	Night	13% 6% 2 5% 4 3 4 3 5% 7% 48%	89563
Transparency	Day	40% 7% 10% 19% 18% 5%	89364
	Night	36% 6% 11% 19% 21% 7%	89397
Seeing	Day	14% 9% 23% 26% 21% 7%	14637
	Night	15% 9% 25% 31% 18% 3	24481

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	19% 12% 4 5% 2 2 3 2 4 5% 42%	2847
	11th to 20th	Day	24% 6% 2 5% 3 2 2 2 3 6% 45%	2850
	21st to end	Day	22% 8% 2 4 3 3 2 2 4 4 45%	3135
February	1st to 10th	Day	21% 9% 3 6% 4 3 3 3 4 5% 39%	1710
	11th to 20th	Day	20% 10% 3 6% 4 4 3 3 3 5% 41%	1828
	21st to end	Day	22% 9% 3 8% 3 4 4 2 3 5% 38%	1690
March	1st to 10th	Day	21% 12% 4 8% 4 4 4 3 4 5% 30%	3436
	11th to 20th	Day	17% 8% 3 6% 5% 4 4 4 5% 7% 36%	3480
	21st to end	Day	16% 9% 3 8% 4 3 3 3 5% 4 41%	3814
April	1st to 10th	Day	12% 7% 2 6% 5% 5% 4 4 6% 5% 43%	2245
	11th to 20th	Day	17% 8% 2 7% 4 5% 4 3 5% 7% 40%	2254
	21st to end	Day	12% 6% 2 6% 4 5% 4 3 5% 7% 45%	2280
May	1st to 10th	Day	14% 8% 3 7% 5% 5% 5% 4 6% 8% 36%	3765
	11th to 20th	Day	12% 6% 2 7% 5% 4 4 3 5% 7% 43%	3884
	21st to end	Day	11% 6% 3 7% 5% 5% 6% 5% 7% 9% 37%	4477
June	1st to 10th	Day	8% 6% 2 7% 6% 6% 6% 5% 7% 10% 37%	2470
	11th to 20th	Day	7% 5% 2 5% 6% 6% 5% 5% 6% 9% 44%	2470
	21st to end	Day	6% 4 1 6% 6% 6% 7% 6% 8% 9% 42%	2458
July	1st to 10th	Day	8% 4 2 7% 6% 8% 8% 5% 8% 11% 32%	2340
	11th to 20th	Day	8% 4 2 5% 7% 6% 7% 5% 8% 11% 37%	2340
	21st to end	Day	7% 5% 2 6% 7% 6% 6% 6% 8% 11% 35%	2546
August	1st to 10th	Day	6% 4 2 6% 5% 5% 6% 4 8% 10% 44%	2292
	11th to 20th	Day	8% 4 2 6% 5% 5% 5% 5% 8% 10% 42%	2125
	21st to end	Day	12% 4 2 6% 5% 5% 6% 4 6% 10% 40%	2376
September	1st to 10th	Day	8% 5% 2 6% 5% 6% 6% 4 6% 8% 46%	2160
	11th to 20th	Day	14% 5% 2 6% 5% 5% 5% 4 5% 8% 41%	2132
	21st to end	Day	8% 4 2 5% 3 5% 3 3 5% 6% 56%	1890
October	1st to 10th	Day	7% 4 1 5% 4 3 4 3 4 7% 59%	1800
	11th to 20th	Day	12% 6% 2 4 4 3 2 2 4 6% 55%	1800
	21st to end	Day	15% 6% 2 4 4 3 3 2 3 4 53%	1980
November	1st to 10th	Day	12% 4 2 5% 4 4 3 3 4 6% 53%	1858
	11th to 20th	Day	12% 6% 2 5% 3 3 4 3 4 4 54%	1900
	21st to end	Day	18% 7% 2 5% 5% 4 3 3 4 5% 44%	1900
December	1st to 10th	Day	16% 8% 3 7% 4 3 3 4 4 5% 43%	1764
	11th to 20th	Day	16% 11% 3 5% 4 4 4 3 3 5% 42%	2161
	21st to end	Day	15% 8% 2 7% 5% 4 4 3 4 5% 42%	3135
January	1st to 10th	Night	16% 8% 3 6% 3 3 3 3 4 5% 48%	4108
	11th to 20th	Night	19% 6% 2 5% 3 3 3 3 3 4 50%	4120
	21st to end	Night	24% 9% 2 5% 3 3 2 2 3 4 44%	4532
February	1st to 10th	Night	17% 8% 2 6% 3 4 4 2 4 5% 44%	2470
	11th to 20th	Night	20% 8% 2 6% 4 3 3 2 4 5% 44%	2237
	21st to end	Night	20% 10% 2 5% 4 3 3 2 4 4 43%	1780
March	1st to 10th	Night	20% 9% 3 7% 5% 4 4 2 4 6% 37%	3419
	11th to 20th	Night	18% 7% 2 6% 4 4 4 4 5% 8% 39%	3480
	21st to end	Night	13% 7% 2 7% 5% 4 5% 3 5% 6% 43%	3817
April	1st to 10th	Night	12% 5% 2 4 3 4 4 3 6% 7% 50%	1933
	11th to 20th	Night	13% 7% 2 5% 4 3 4 3 5% 7% 46%	1875
	21st to end	Night	9% 7% 2 6% 4 3 4 3 5% 7% 52%	1900
May	1st to 10th	Night	12% 7% 3 7% 4 4 5% 3 7% 8% 41%	3130
	11th to 20th	Night	15% 6% 2 6% 4 4 4 4 5% 8% 42%	3009
	21st to end	Night	10% 6% 3 7% 5% 4 5% 4 6% 8% 42%	3090
June	1st to 10th	Night	7% 3 1 4 5% 4 5% 5% 7% 11% 48%	1710
	11th to 20th	Night	4 4 1 3 4 3 3 4 7% 11% 56%	1710
	21st to end	Night	6% 5% 2 5% 4 4 4 4 6% 8% 53%	1701
July	1st to 10th	Night	5% 4 1 4 6% 4 5% 5% 9% 11% 46%	1620
	11th to 20th	Night	6% 2 1 3 4 4 5% 5% 8% 12% 50%	1620
	21st to end	Night	3 3 1 3 4 4 4 6% 8% 14% 48%	1772
August	1st to 10th	Night	4 2 1 4 3 4 4 4 7% 13% 55%	1642
	11th to 20th	Night	7% 2 2 4 3 4 4 4 8% 12% 50%	1776
	21st to end	Night	9% 4 2 5% 4 5% 6% 4 7% 10% 46%	1980
September	1st to 10th	Night	7% 5% 2 6% 5% 4 4 3 5% 7% 52%	1800
	11th to 20th	Night	10% 5% 2 6% 4 4 4 4 5% 7% 48%	1823
	21st to end	Night	8% 4 2 5% 4 3 3 3 4 6% 59%	2052
October	1st to 10th	Night	7% 3 1 4 3 3 4 3 5% 7% 61%	2160
	11th to 20th	Night	11% 5% 1 5% 3 3 4 2 4 5% 58%	2160
	21st to end	Night	13% 5% 1 4 3 3 3 3 4 5% 56%	2376
November	1st to 10th	Night	10% 5% 2 5% 3 3 3 3 4 6% 57%	2220
	11th to 20th	Night	12% 5% 2 4 4 3 3 2 4 6% 55%	2280
	21st to end	Night	15% 7% 3 6% 3 4 3 3 4 5% 48%	2280
December	1st to 10th	Night	17% 8% 3 5% 3 3 3 3 5% 6% 44%	2413
	11th to 20th	Night	15% 8% 2 6% 4 3 4 3 4 4 47%	3036
	21st to end	Night	16% 9% 2 6% 4 3 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	46% 3 4 15% 27% 5%	2848
	11th to 20th	Day	42% 4 6% 21% 22% 5%	2850
	21st to end	Day	44% 3 4 17% 21% 10%	3135
February	1st to 10th	Day	48% 5% 6% 17% 14% 11%	1710
	11th to 20th	Day	47% 4 5% 16% 20% 8%	1838
	21st to end	Day	50% 4 7% 12% 19% 9%	1690
March	1st to 10th	Day	55% 5% 7% 11% 15% 5%	3436
	11th to 20th	Day	46% 7% 7% 19% 16% 5%	3480
	21st to end	Day	46% 4 7% 17% 23% 3	3814
April	1st to 10th	Day	40% 6% 9% 21% 16% 8%	2245
	11th to 20th	Day	45% 6% 9% 14% 18% 8%	2254
	21st to end	Day	37% 6% 11% 20% 22% 3	2280
May	1st to 10th	Day	44% 9% 10% 24% 11% 3	3800
	11th to 20th	Day	38% 7% 12% 20% 22% 1	3888
	21st to end	Day	40% 10% 14% 23% 11% 2	4489
June	1st to 10th	Day	39% 10% 15% 21% 14% 2	2470
	11th to 20th	Day	34% 9% 15% 23% 17% 2	2470
	21st to end	Day	34% 11% 16% 22% 14% 3	2458
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	39% 4 6% 15% 28% 7%	4108
	11th to 20th	Night	38% 4 7% 22% 21% 9%	4120
	21st to end	Night	46% 3 7% 16% 20% 8%	4532
February	1st to 10th	Night	42% 4 7% 17% 20% 9%	2470
	11th to 20th	Night	45% 4 5% 16% 21% 9%	2238
	21st to end	Night	45% 5% 6% 13% 16% 14%	1780
March	1st to 10th	Night	49% 6% 7% 14% 17% 7%	3419
	11th to 20th	Night	42% 8% 10% 15% 19% 6%	3480
	21st to end	Night	40% 7% 9% 17% 25% 3	3817
April	1st to 10th	Night	33% 6% 11% 20% 18% 11%	1933
	11th to 20th	Night	37% 5% 9% 17% 19% 12%	1875
	21st to end	Night	32% 6% 9% 23% 25% 5%	1900
May	1st to 10th	Night	38% 9% 11% 21% 16% 5%	3160
	11th to 20th	Night	37% 8% 12% 23% 19% 1	3010
	21st to end	Night	36% 10% 14% 24% 15% 1	3099
June	1st to 10th	Night	27% 11% 16% 26% 19% 1	1710
	11th to 20th	Night	22% 8% 19% 28% 20% 3	1710
	21st to end	Night	27% 9% 16% 25% 20% 3	1701
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	30% 20% 35% 11% 4 1	270
	21st to end	Day	26% 26% 30% 15% 3	297
February	1st to 10th	Day	29% 17% 37% 11% 5% 1	270
	11th to 20th	Day	35% 18% 36% 10%	270
	21st to end	Day	35% 32% 26% 5% 2	225
March	1st to 10th	Day	28% 21% 32% 16% 3	270
	11th to 20th	Day	21% 29% 36% 13% 1	270
	21st to end	Day	22% 26% 34% 15% 4	297
April	1st to 10th	Day	21% 21% 33% 18% 6%	425
	11th to 20th	Day	27% 14% 32% 17% 10% 1	452
	21st to end	Day	15% 16% 33% 26% 9% 2	460
May	1st to 10th	Day	15% 12% 34% 27% 11% 1	463
	11th to 20th	Day	14% 7% 28% 30% 17% 5%	555
	21st to end	Day	8% 7% 26% 37% 18% 5%	734
June	1st to 10th	Day	9% 3 16% 38% 26% 8%	680
	11th to 20th	Day	7% 3 18% 39% 28% 6%	680
	21st to end	Day	8% 2 16% 31% 32% 12%	676
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% 16% 31% 24% 7%	950
	21st to end	Night	22% 14% 35% 26% 2	1045
February	1st to 10th	Night	22% 14% 33% 26% 4	950
	11th to 20th	Night	26% 16% 34% 21% 3	762
	21st to end	Night	28% 16% 35% 19% 2	524
March	1st to 10th	Night	20% 14% 35% 26% 5%	570
	11th to 20th	Night	18% 15% 35% 27% 4 1	570
	21st to end	Night	16% 13% 37% 26% 7%	627
April	1st to 10th	Night	15% 13% 40% 24% 7%	570
	11th to 20th	Night	18% 13% 34% 25% 9% 1	563
	21st to end	Night	13% 11% 35% 29% 10% 1	570
May	1st to 10th	Night	11% 8% 34% 36% 11% 1	570
	11th to 20th	Night	11% 5% 31% 32% 18% 2	561
	21st to end	Night	6% 4 23% 40% 23% 4	617
June	1st to 10th	Night	6% 2 12% 43% 31% 5%	570
	11th to 20th	Night	5% 2 14% 39% 37% 3	570
	21st to end	Night	6% 1 14% 33% 37% 8%	567
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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