Lewisville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lewisville clear sky chart from 2005-11-05 to 2018-01-20.

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%
16115
26%
48407
18%
16070
56%
16070
33%
28351

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
31%
974
26%
2522
9%
970
43%
970
28%
1629
January16th to endNight
27%
985
28%
2561
10%
985
38%
985
29%
1668
February1st to 15thNight
26%
880
23%
2288
6%
876
37%
876
30%
1450
February16th to endNight
24%
534
28%
1796
11%
534
39%
534
25%
1060
March1st to 15thNight
32%
540
25%
1980
15%
540
45%
540
24%
1165
March16th to endNight
34%
576
21%
2112
16%
576
44%
576
23%
1258
April1st to 15thNight
35%
539
26%
1845
16%
539
51%
539
31%
1016
April16th to endNight
40%
540
25%
1800
19%
540
52%
540
30%
1022
May1st to 15thNight
41%
540
22%
1731
17%
540
53%
540
28%
1052
May16th to endNight
55%
562
23%
1684
21%
561
61%
561
33%
1002
June1st to 15thNight
76%
540
22%
1620
23%
540
80%
540
43%
862
June16th to endNight
75%
540
25%
1620
26%
540
78%
540
43%
872
July1st to 15thNight
77%
510
20%
1530
21%
510
78%
510
37%
889
July16th to endNight
84%
564
26%
1594
31%
531
85%
531
46%
841
August1st to 15thNight
82%
539
28%
1637
31%
536
84%
536
46%
836
August16th to endNight
72%
573
22%
1910
27%
573
72%
573
30%
1127
September1st to 15thNight
70%
540
24%
1815
27%
540
72%
540
34%
1006
September16th to endNight
74%
557
34%
2000
35%
557
77%
557
39%
1020
October1st to 15thNight
64%
720
31%
2160
24%
720
69%
720
43%
1156
October16th to endNight
53%
768
38%
2304
24%
768
65%
768
43%
1196
November1st to 15thNight
47%
760
27%
2280
18%
760
54%
760
35%
1300
November16th to endNight
39%
819
33%
2379
20%
819
50%
819
31%
1422
December1st to 15thNight
37%
975
24%
2535
12%
975
45%
975
28%
1672
December16th to endNight
30%
1040
23%
2704
10%
1040
39%
1040
26%
1830

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%2443445%7%43%
49115
Night
11%423323447%51%
48603
TransparencyDay
39%5%10%20%18%5%
48815
Night
32%410%21%22%8%
48408
SeeingDay
12%6%20%26%25%8%
6002
Night
14%7%24%30%20%2
16117

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
17%5%3442333447%
1746
16th to endDay
21%5%24312235%46%
1767
February1st to 15thDay
20%6%2432233444%
1575
16th to endDay
22%7%25%32323442%
1684
March1st to 15thDay
21%6%24323335%42%
1980
16th to endDay
17%5%36%42435%6%40%
2110
April1st to 15thDay
13%5%25%434446%46%
2103
16th to endDay
15%5%25%5%245%47%42%
2160
May1st to 15thDay
15%6%35%5%26%5%5%6%36%
2217
16th to endDay
9%5%25%6%36%5%6%8%38%
2430
June1st to 15thDay
6%326%5%46%7%5%9%40%
2340
16th to endDay
6%3245%47%6%7%10%40%
2340
July1st to 15thDay
9%425%6%36%6%8%11%34%
2340
16th to endDay
8%325%5%47%7%8%9%38%
2466
August1st to 15thDay
5%2145%45%6%8%10%44%
2313
16th to endDay
10%5%25%6%37%6%7%9%36%
2292
September1st to 15thDay
11%4244345%5%7%44%
2142
16th to endDay
8%21343445%8%52%
1947
October1st to 15thDay
11%424433435%53%
1800
16th to endDay
14%31221222460%
1920
November1st to 15thDay
13%5%24423345%50%
1908
16th to endDay
16%5%25%32323352%
1908
December1st to 15thDay
18%7%3432333444%
1755
16th to endDay
19%7%25%434235%41%
1872
January1st to 15thNight
18%6%2332233450%
2522
16th to endNight
18%5%25%21232449%
2561
February1st to 15thNight
17%6%2431224451%
2278
16th to endNight
17%6%13313335%49%
1796
March1st to 15thNight
16%6%23323337%46%
1980
16th to endNight
14%5%24424346%46%
2112
April1st to 15thNight
9%32432445%6%52%
1845
16th to endNight
9%424423347%51%
1800
May1st to 15thNight
12%5%24425%347%47%
1730
16th to endNight
7%4244245%6%10%46%
1683
June1st to 15thNight
32142235%6%9%57%
1620
16th to endNight
422332446%9%56%
1620
July1st to 15thNight
5%3235%35%5%6%11%47%
1620
16th to endNight
3123246%7%11%54%
1702
August1st to 15thNight
41123225%6%9%58%
1647
16th to endNight
8%414425%5%7%12%42%
1910
September1st to 15thNight
9%3133235%5%9%51%
1815
16th to endNight
6%31332345%8%57%
2000
October1st to 15thNight
8%413323346%59%
2160
16th to endNight
11%312213235%63%
2304
November1st to 15thNight
10%424323346%54%
2280
16th to endNight
16%5%2331223353%
2379
December1st to 15thNight
15%6%33323445%46%
2535
16th to endNight
20%6%24413335%43%
2704

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
42%25%19%22%6%
1747
16th to endDay
41%2418%25%5%
1767
February1st to 15thDay
43%45%20%20%6%
1576
16th to endDay
46%36%17%19%6%
1684
March1st to 15thDay
45%37%19%17%5%
1980
16th to endDay
44%5%8%20%19%2
2112
April1st to 15thDay
38%48%21%19%7%
2103
16th to endDay
41%48%22%18%3
2160
May1st to 15thDay
46%6%9%15%16%5%
2217
16th to endDay
39%8%15%22%12%1
2434
June1st to 15thDay
37%8%12%25%15%1
2340
16th to endDay
36%7%13%21%18%1
2340
July1st to 15thDay
38%8%16%22%13%
2201
16th to endDay
36%9%17%23%12%1
2311
August1st to 15thDay
30%9%17%25%15%1
2299
16th to endDay
40%9%15%19%11%2
2292
September1st to 15thDay
37%7%12%17%18%7%
2142
16th to endDay
29%5%11%23%20%9%
1947
October1st to 15thDay
33%48%18%20%14%
1800
16th to endDay
29%25%17%32%13%
1920
November1st to 15thDay
35%47%20%24%7%
1908
16th to endDay
38%25%15%28%8%
1908
December1st to 15thDay
44%37%18%17%8%
1755
16th to endDay
46%38%18%18%4
1872
January1st to 15thNight
38%36%17%26%7%
2522
16th to endNight
39%35%16%24%10%
2561
February1st to 15thNight
38%27%21%22%8%
2288
16th to endNight
38%36%21%20%9%
1796
March1st to 15thNight
38%49%19%18%9%
1980
16th to endNight
39%5%8%19%22%4
2112
April1st to 15thNight
32%310%21%20%11%
1845
16th to endNight
33%49%22%22%6%
1800
May1st to 15thNight
37%5%8%21%18%9%
1731
16th to endNight
30%8%15%25%17%1
1685
June1st to 15thNight
21%8%13%31%22%3
1620
16th to endNight
24%5%13%25%26%4
1620
July1st to 15thNight
27%8%17%27%16%1
1530
16th to endNight
20%8%20%32%16%2
1594
August1st to 15thNight
20%6%15%33%20%2
1637
16th to endNight
32%8%17%22%16%3
1910
September1st to 15thNight
29%6%14%20%21%8%
1815
16th to endNight
25%5%8%22%25%11%
2000
October1st to 15thNight
26%38%21%22%16%
2160
16th to endNight
25%35%16%29%20%
2304
November1st to 15thNight
31%410%18%25%10%
2280
16th to endNight
36%2415%29%11%
2379
December1st to 15thNight
40%410%17%18%8%
2535
16th to endNight
43%38%19%19%6%
2704

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
19%13%45%18%2
135
16th to endDay
18%25%33%14%6%
109
February1st to 15thDay
20%16%42%17%3
90
16th to endDay
19%22%43%12%2
81
March1st to 15thDay
30%22%34%10%3
90
16th to endDay
15%20%29%28%6%
96
April1st to 15thDay
18%14%36%18%10%1
222
16th to endDay
20%10%30%21%15%2
270
May1st to 15thDay
17%9%32%28%8%3
354
16th to endDay
12%429%32%16%4
517
June1st to 15thDay
8%12%37%33%7%
495
16th to endDay
7%213%33%33%10%
495
July1st to 15thDay
8%112%31%35%10%
475
16th to endDay
5%5%23%46%17%
515
August1st to 15thDay
8%5%26%42%16%
466
16th to endDay
18%5%24%34%17%
332
September1st to 15thDay
8%6%24%44%15%
297
16th to endDay
211%40%32%14%
135
October1st to 15thDay
3128%42%14%8%
135
16th to endDay
19%6%27%26%15%4
144
November1st to 15thDay
20%7%31%28%11%
135
16th to endDay
20%14%31%18%11%3
135
December1st to 15thDay
21%12%40%11%11%2
135
16th to endDay
27%23%31%12%21
144
January1st to 15thNight
23%13%28%27%7%
975
16th to endNight
22%13%34%25%3
985
February1st to 15thNight
21%13%35%24%4
880
16th to endNight
21%14%38%22%3
534
March1st to 15thNight
19%10%35%30%4
540
16th to endNight
15%11%36%26%9%
576
April1st to 15thNight
10%13%38%26%10%
539
16th to endNight
11%9%34%30%12%1
540
May1st to 15thNight
14%6%33%31%11%1
540
16th to endNight
7%326%36%23%3
563
June1st to 15thNight
5%10%42%38%2
540
16th to endNight
312%35%41%7%
540
July1st to 15thNight
5%8%37%42%6%
510
16th to endNight
3429%49%11%
564
August1st to 15thNight
46%28%45%13%
539
16th to endNight
11%5%30%44%7%
573
September1st to 15thNight
11%110%28%43%4
540
16th to endNight
7%19%35%41%5%
557
October1st to 15thNight
11%218%36%26%4
720
16th to endNight
11%5%25%32%22%2
768
November1st to 15thNight
11%9%27%34%16%1
760
16th to endNight
19%9%28%26%15%
819
December1st to 15thNight
20%10%28%30%9%
975
16th to endNight
23%14%28%27%6%
1040
Page generated at 2018-01-21 11:19:22. Version ac04

Copyright 2018 A. Danko


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