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 2005-11-05 to 2017-09-24.

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 TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(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

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
48%
15535
25%
46930
17%
15490
56%
15490
31%
27851

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
29%
900
25%
2327
9%
895
39%
895
27%
1512
January16th to endNight
26%
960
26%
2496
8%
960
37%
960
27%
1643
February1st to 15thNight
29%
836
24%
2244
8%
833
40%
833
29%
1430
February16th to endNight
21%
565
27%
1827
10%
565
35%
565
23%
1129
March1st to 15thNight
27%
540
24%
1980
14%
540
40%
540
22%
1216
March16th to endNight
36%
576
20%
2112
15%
576
45%
576
24%
1238
April1st to 15thNight
35%
539
25%
1818
15%
539
50%
539
31%
1002
April16th to endNight
39%
540
25%
1800
18%
540
52%
540
29%
1029
May1st to 15thNight
42%
540
19%
1800
14%
540
52%
540
27%
1076
May16th to endNight
59%
562
25%
1695
22%
561
65%
561
36%
983
June1st to 15thNight
77%
540
20%
1620
20%
540
80%
540
42%
891
June16th to endNight
72%
540
21%
1620
22%
540
75%
540
37%
943
July1st to 15thNight
76%
510
20%
1530
21%
510
78%
510
39%
862
July16th to endNight
82%
564
22%
1594
26%
531
82%
531
42%
883
August1st to 15thNight
84%
539
22%
1691
27%
536
85%
536
46%
859
August16th to endNight
73%
573
20%
1910
26%
573
74%
573
28%
1159
September1st to 15thNight
71%
540
23%
1800
25%
540
72%
540
32%
1038
September16th to endNight
67%
563
31%
1914
31%
563
70%
563
36%
1029
October1st to 15thNight
62%
660
31%
1980
23%
660
67%
660
40%
1085
October16th to endNight
55%
704
36%
2112
25%
704
63%
704
41%
1130
November1st to 15thNight
49%
700
30%
2100
21%
700
57%
700
36%
1177
November16th to endNight
40%
720
32%
2160
20%
720
51%
720
30%
1297
December1st to 15thNight
34%
864
24%
2304
12%
864
42%
864
27%
1525
December16th to endNight
30%
960
22%
2496
8%
960
39%
960
24%
1715

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 ForecastData
Points
Cloud CoverDay
13%5%25%5%35%45%7%42%
47992
Night
11%424423347%50%
47128
TransparencyDay
41%6%10%18%17%5%
47693
Night
33%5%11%19%21%8%
46932
SeeingDay
12%5%18%27%26%9%
5596
Night
14%7%24%30%20%3
15536

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
19%6%24422235%45%
1611
16th to endDay
19%7%3431233346%
1728
February1st to 15thDay
18%7%3432333445%
1617
16th to endDay
19%6%35%423325%42%
1655
March1st to 15thDay
21%6%34334345%38%
1980
16th to endDay
14%6%36%424445%43%
2110
April1st to 15thDay
12%6%25%434346%45%
2130
16th to endDay
14%6%35%5%34447%41%
2160
May1st to 15thDay
14%7%36%5%345%5%6%36%
2151
16th to endDay
8%435%6%37%6%6%9%38%
2416
June1st to 15thDay
7%426%6%45%7%6%10%37%
2340
16th to endDay
7%426%7%48%6%8%8%36%
2340
July1st to 15thDay
9%325%7%5%9%6%7%9%32%
2340
16th to endDay
9%435%7%47%7%7%10%32%
2466
August1st to 15thDay
8%325%5%35%6%7%10%41%
2256
16th to endDay
12%425%5%46%5%6%10%34%
2292
September1st to 15thDay
11%4245%36%45%8%42%
2160
16th to endDay
10%2145%35%5%47%47%
1890
October1st to 15thDay
9%4246%23346%53%
1650
16th to endDay
14%41322222459%
1760
November1st to 15thDay
11%424424345%52%
1758
16th to endDay
17%6%2342333448%
1800
December1st to 15thDay
18%8%35%314335%40%
1654
16th to endDay
17%8%35%5%33335%39%
1728
January1st to 15thNight
16%5%25%32334449%
2327
16th to endNight
19%6%3431323447%
2496
February1st to 15thNight
14%6%25%323235%49%
2235
16th to endNight
16%6%24422335%47%
1827
March1st to 15thNight
17%5%25%5%14345%44%
1980
16th to endNight
13%5%14434346%47%
2112
April1st to 15thNight
8%323424449%51%
1818
16th to endNight
10%5%24424347%50%
1800
May1st to 15thNight
12%5%25%42436%7%45%
1799
16th to endNight
7%3245%2435%10%49%
1695
June1st to 15thNight
5%21232446%11%55%
1620
16th to endNight
5%324425%5%6%8%51%
1620
July1st to 15thNight
6%32342448%10%49%
1620
16th to endNight
42134245%7%15%47%
1702
August1st to 15thNight
5%11322347%12%54%
1701
16th to endNight
9%324335%5%7%10%42%
1910
September1st to 15thNight
9%41343346%7%51%
1800
16th to endNight
8%424423336%56%
1914
October1st to 15thNight
7%314424346%58%
1980
16th to endNight
13%312212335%60%
2112
November1st to 15thNight
9%424423336%56%
2100
16th to endNight
15%42432333452%
2160
December1st to 15thNight
18%7%24313345%44%
2304
16th to endNight
17%8%25%422335%43%
2496

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
43%3417%23%8%
1612
16th to endDay
43%2417%23%8%
1728
February1st to 15thDay
43%45%19%18%9%
1619
16th to endDay
45%35%15%22%7%
1655
March1st to 15thDay
48%47%16%17%6%
1980
16th to endDay
43%5%8%17%22%2
2112
April1st to 15thDay
39%5%9%21%18%7%
2130
16th to endDay
42%5%10%17%20%4
2160
May1st to 15thDay
47%5%9%14%16%6%
2151
16th to endDay
39%8%15%23%12%1
2420
June1st to 15thDay
38%9%14%21%14%
2340
16th to endDay
41%9%14%18%12%2
2340
July1st to 15thDay
42%9%19%19%9%
2201
16th to endDay
42%10%17%19%9%
2311
August1st to 15thDay
34%10%17%22%13%1
2242
16th to endDay
43%10%16%16%10%2
2292
September1st to 15thDay
39%9%11%18%15%6%
2160
16th to endDay
35%6%10%18%22%7%
1890
October1st to 15thDay
32%47%17%22%15%
1650
16th to endDay
30%25%14%32%13%
1760
November1st to 15thDay
34%47%18%26%8%
1758
16th to endDay
40%35%13%26%9%
1800
December1st to 15thDay
47%47%16%16%7%
1654
16th to endDay
48%37%18%17%4
1728
January1st to 15thNight
38%46%15%26%8%
2327
16th to endNight
41%26%16%22%10%
2496
February1st to 15thNight
38%47%18%23%8%
2244
16th to endNight
40%45%19%19%10%
1827
March1st to 15thNight
42%48%16%20%7%
1980
16th to endNight
37%5%10%19%22%5%
2112
April1st to 15thNight
30%5%11%22%19%10%
1818
16th to endNight
34%49%22%22%7%
1800
May1st to 15thNight
37%5%11%18%17%9%
1800
16th to endNight
29%6%16%26%19%1
1697
June1st to 15thNight
23%8%16%29%21%1
1620
16th to endNight
28%8%18%22%19%3
1620
July1st to 15thNight
25%8%23%28%11%2
1530
16th to endNight
22%9%24%29%13%1
1594
August1st to 15thNight
20%6%24%27%16%3
1691
16th to endNight
32%10%18%21%13%3
1910
September1st to 15thNight
30%8%15%19%18%7%
1800
16th to endNight
28%5%9%17%27%11%
1914
October1st to 15thNight
27%49%16%23%18%
1980
16th to endNight
27%35%15%28%19%
2112
November1st to 15thNight
30%48%18%26%11%
2100
16th to endNight
37%25%13%27%13%
2160
December1st to 15thNight
42%49%18%18%6%
2304
16th to endNight
45%36%18%20%5%
2496

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
16%17%43%14%7%
90
16th to endDay
18%34%33%11%2
96
February1st to 15thDay
21%20%41%14%3
90
16th to endDay
13%32%37%13%3
81
March1st to 15thDay
27%24%36%10%1
90
16th to endDay
17%19%23%31%6%1
96
April1st to 15thDay
20%13%34%18%12%1
249
16th to endDay
19%9%28%25%14%2
270
May1st to 15thDay
18%7%30%28%12%3
288
16th to endDay
8%5%27%33%18%5%
503
June1st to 15thDay
8%112%40%29%6%
495
16th to endDay
7%114%34%31%10%
495
July1st to 15thDay
6%10%33%36%10%
475
16th to endDay
6%427%44%16%
515
August1st to 15thDay
10%326%41%18%
409
16th to endDay
18%319%37%19%
332
September1st to 15thDay
9%28%23%35%20%
315
16th to endDay
7%9%29%38%14%
155
October1st to 15thDay
1428%33%25%6%
90
16th to endDay
17%5%25%18%27%6%
96
November1st to 15thDay
18%7%33%33%5%1
90
16th to endDay
21%12%43%11%6%5%
90
December1st to 15thDay
23%11%41%12%10%2
90
16th to endDay
21%19%40%11%5%1
96
January1st to 15thNight
20%15%32%24%8%
900
16th to endNight
21%13%35%26%3
960
February1st to 15thNight
19%13%34%28%4
836
16th to endNight
21%15%38%21%1
565
March1st to 15thNight
19%13%36%26%4
540
16th to endNight
14%10%35%28%9%
576
April1st to 15thNight
10%12%39%25%10%
539
16th to endNight
15%9%32%31%10%
540
May1st to 15thNight
12%6%34%33%11%1
540
16th to endNight
7%323%38%25%2
563
June1st to 15thNight
6%10%43%34%5%
540
16th to endNight
410%32%42%8%
540
July1st to 15thNight
5%8%33%43%7%
510
16th to endNight
5%329%46%14%
564
August1st to 15thNight
5%326%51%12%
539
16th to endNight
11%5%29%42%10%
573
September1st to 15thNight
10%7%35%35%9%
540
16th to endNight
9%29%35%35%7%
563
October1st to 15thNight
9%320%31%31%4
660
16th to endNight
14%421%33%23%3
704
November1st to 15thNight
9%8%27%32%19%2
700
16th to endNight
17%9%29%29%13%
720
December1st to 15thNight
22%10%29%28%9%
864
16th to endNight
22%16%27%26%7%
960
Page generated at 2017-09-25 08:02:21. Version ac04

Copyright 2017 A. Danko


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