Maryville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Maryville clear sky chart from 2005-11-05 to 2018-02-13.

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 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%
16082
19%
48779
15%
16039
53%
16039
24%
32325

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
30%
780
17%
2522
12%
776
37%
776
17%
1765
January16th to endNight
28%
832
19%
2704
11%
832
38%
832
16%
1890
February1st to 15thNight
27%
753
18%
2263
9%
750
36%
750
18%
1594
February16th to endNight
22%
631
20%
1893
11%
631
30%
631
17%
1351
March1st to 15thNight
31%
720
19%
2061
12%
720
36%
720
21%
1439
March16th to endNight
36%
768
16%
2112
11%
768
39%
768
21%
1491
April1st to 15thNight
40%
632
22%
1890
13%
632
49%
632
27%
1177
April16th to endNight
44%
540
20%
1668
14%
540
50%
540
26%
1080
May1st to 15thNight
51%
540
16%
1620
10%
540
56%
540
24%
1086
May16th to endNight
62%
561
16%
1683
11%
561
64%
561
26%
1105
June1st to 15thNight
68%
540
14%
1620
12%
540
70%
540
28%
1038
June16th to endNight
74%
540
18%
1620
15%
540
76%
540
30%
1008
July1st to 15thNight
68%
510
11%
1530
8%
510
69%
510
24%
1054
July16th to endNight
76%
564
14%
1595
13%
531
76%
531
29%
1034
August1st to 15thNight
76%
539
18%
1609
18%
536
76%
536
28%
1041
August16th to endNight
67%
573
16%
1881
18%
573
68%
573
23%
1247
September1st to 15thNight
65%
702
17%
1962
15%
702
65%
702
25%
1339
September16th to endNight
64%
717
25%
1980
21%
717
66%
717
32%
1250
October1st to 15thNight
56%
720
30%
2011
27%
720
60%
720
35%
1216
October16th to endNight
49%
768
30%
2310
24%
768
58%
768
33%
1352
November1st to 15thNight
50%
760
26%
2471
25%
760
56%
760
28%
1480
November16th to endNight
45%
780
25%
2535
21%
780
52%
780
26%
1562
December1st to 15thNight
36%
780
18%
2535
14%
780
43%
780
18%
1764
December16th to endNight
32%
832
17%
2704
12%
832
39%
832
15%
1962

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%6%25%5%35%5%5%7%39%
49257
Night
13%6%25%43445%7%41%
48977
TransparencyDay
44%8%11%18%14%2
48958
Night
42%7%11%19%16%3
48780
SeeingDay
16%8%19%24%20%10%
5846
Night
16%7%20%30%21%3
16084

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
16%9%47%6%3435%5%33%
1746
16th to endDay
17%7%25%42435%6%39%
1872
February1st to 15thDay
20%8%37%5%2434434%
1864
16th to endDay
16%7%45%5%34348%36%
1580
March1st to 15thDay
16%8%35%5%3446%6%36%
1897
16th to endDay
15%8%45%5%345%5%6%36%
2111
April1st to 15thDay
12%425%435%45%8%43%
2067
16th to endDay
14%5%25%5%35%446%43%
2291
May1st to 15thDay
14%425%5%36%5%5%6%40%
2331
16th to endDay
11%5%36%6%46%6%5%8%36%
2431
June1st to 15thDay
7%425%6%47%7%7%8%37%
2340
16th to endDay
6%3246%46%6%7%10%40%
2340
July1st to 15thDay
10%5%36%6%46%7%7%10%30%
2340
16th to endDay
8%5%25%7%47%7%9%10%31%
2465
August1st to 15thDay
7%326%7%45%8%8%11%33%
2340
16th to endDay
11%6%26%7%35%5%7%9%33%
2319
September1st to 15thDay
13%6%26%6%3446%8%37%
1986
16th to endDay
14%41343345%7%46%
1980
October1st to 15thDay
12%313322336%56%
1947
16th to endDay
15%313323335%53%
1911
November1st to 15thDay
12%5%25%323336%50%
1717
16th to endDay
12%7%24323346%48%
1755
December1st to 15thDay
16%8%25%4345%5%6%36%
1755
16th to endDay
20%11%35%423445%34%
1872
January1st to 15thNight
17%8%37%423345%37%
2522
16th to endNight
17%9%45%5%3443437%
2704
February1st to 15thNight
17%9%35%424446%37%
2254
16th to endNight
19%9%35%43445%5%36%
1893
March1st to 15thNight
16%8%35%434346%38%
2061
16th to endNight
15%7%35%434345%40%
2112
April1st to 15thNight
12%5%24324347%48%
1890
16th to endNight
12%425%435%447%45%
1668
May1st to 15thNight
13%425%43445%9%40%
1619
16th to endNight
8%436%5%335%6%12%40%
1682
June1st to 15thNight
4424436%6%9%13%39%
1620
16th to endNight
4325%435%6%6%13%44%
1620
July1st to 15thNight
8%5%25%6%46%6%7%10%36%
1620
16th to endNight
5%3245%35%7%9%13%38%
1703
August1st to 15thNight
6%435%435%5%7%11%42%
1620
16th to endNight
7%426%6%35%6%7%11%36%
1881
September1st to 15thNight
9%5%26%5%35%5%6%8%40%
1962
16th to endNight
9%424434446%49%
1980
October1st to 15thNight
12%424312345%54%
2011
16th to endNight
14%5%13413235%54%
2310
November1st to 15thNight
14%7%14323335%50%
2471
16th to endNight
14%5%24414445%48%
2535
December1st to 15thNight
17%8%36%423446%37%
2535
16th to endNight
22%9%35%434445%32%
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
53%6%7%16%14%2
1747
16th to endDay
46%5%9%21%15%2
1872
February1st to 15thDay
54%5%7%17%13%1
1866
16th to endDay
49%49%17%15%3
1580
March1st to 15thDay
49%6%7%18%15%3
1897
16th to endDay
49%6%11%19%11%1
2112
April1st to 15thDay
38%8%10%21%18%2
2067
16th to endDay
42%7%9%20%16%3
2291
May1st to 15thDay
44%9%11%20%11%2
2331
16th to endDay
46%10%12%17%10%2
2435
June1st to 15thDay
42%12%14%20%8%1
2340
16th to endDay
37%12%15%17%13%3
2340
July1st to 15thDay
46%12%16%13%10%1
2201
16th to endDay
44%12%16%15%8%1
2310
August1st to 15thDay
43%12%16%17%9%1
2327
16th to endDay
47%10%15%14%10%1
2319
September1st to 15thDay
45%10%11%15%12%4
1986
16th to endDay
39%6%12%18%19%3
1980
October1st to 15thDay
32%6%9%23%23%5%
1947
16th to endDay
34%37%22%25%6%
1911
November1st to 15thDay
37%47%19%25%5%
1717
16th to endDay
37%5%7%21%22%4
1755
December1st to 15thDay
49%7%8%19%12%3
1755
16th to endDay
53%5%11%15%12%1
1872
January1st to 15thNight
50%5%8%15%16%3
2522
16th to endNight
51%47%17%15%2
2704
February1st to 15thNight
50%5%8%19%13%2
2263
16th to endNight
51%5%8%18%14%1
1893
March1st to 15thNight
47%5%9%17%15%3
2061
16th to endNight
47%7%10%21%12%1
2112
April1st to 15thNight
38%5%10%23%19%3
1890
16th to endNight
39%7%11%21%17%3
1668
May1st to 15thNight
41%8%14%21%12%1
1620
16th to endNight
38%10%16%21%10%2
1684
June1st to 15thNight
34%11%21%22%10%
1620
16th to endNight
32%10%16%24%12%4
1620
July1st to 15thNight
39%12%17%17%11%1
1530
16th to endNight
33%12%23%19%9%1
1595
August1st to 15thNight
34%11%15%22%14%
1609
16th to endNight
39%11%16%19%11%1
1881
September1st to 15thNight
40%10%15%16%15%3
1962
16th to endNight
34%7%11%19%23%2
1980
October1st to 15thNight
32%5%9%21%24%6%
2011
16th to endNight
34%37%20%26%7%
2310
November1st to 15thNight
38%46%19%24%8%
2471
16th to endNight
39%5%7%21%22%4
2535
December1st to 15thNight
50%5%9%16%14%3
2535
16th to endNight
54%5%9%14%13%2
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
18%29%29%17%4
135
16th to endDay
22%26%31%13%41
144
February1st to 15thDay
32%25%30%11%
126
16th to endDay
32%11%35%20%
81
March1st to 15thDay
22%16%33%21%5%
187
16th to endDay
19%12%31%26%10%
288
April1st to 15thDay
18%15%17%29%16%1
270
16th to endDay
15%9%22%31%16%5%
270
May1st to 15thDay
16%11%28%19%16%7%
288
16th to endDay
16%6%17%24%20%14%
331
June1st to 15thDay
10%49%28%30%16%
315
16th to endDay
11%114%29%25%17%
315
July1st to 15thDay
14%313%25%28%14%
305
16th to endDay
11%7%24%28%27%
326
August1st to 15thDay
14%19%24%30%20%
313
16th to endDay
15%12%19%32%19%
332
September1st to 15thDay
12%410%22%34%15%
315
16th to endDay
15%19%28%31%12%
314
October1st to 15thDay
16%318%27%25%8%
315
16th to endDay
17%9%19%26%21%4
327
November1st to 15thDay
17%11%29%26%11%2
135
16th to endDay
11%11%27%37%11%
135
December1st to 15thDay
23%14%40%17%2
135
16th to endDay
28%16%36%16%1
144
January1st to 15thNight
20%16%28%28%6%
780
16th to endNight
22%16%28%29%3
832
February1st to 15thNight
23%13%32%27%2
753
16th to endNight
26%15%31%22%3
631
March1st to 15thNight
22%13%27%31%4
720
16th to endNight
21%12%25%28%10%
768
April1st to 15thNight
17%12%27%31%10%1
632
16th to endNight
15%7%26%31%17%1
540
May1st to 15thNight
15%423%35%18%2
540
16th to endNight
10%314%31%35%5%
563
June1st to 15thNight
7%113%32%38%7%
540
16th to endNight
6%10%34%40%8%
540
July1st to 15thNight
10%9%30%41%7%
510
16th to endNight
7%6%25%46%14%
564
August1st to 15thNight
6%15%31%45%10%
539
16th to endNight
10%7%24%47%8%
573
September1st to 15thNight
12%29%27%40%7%
702
16th to endNight
12%12%34%35%4
717
October1st to 15thNight
15%6%15%25%30%6%
720
16th to endNight
17%5%22%31%20%2
768
November1st to 15thNight
17%6%20%31%21%2
760
16th to endNight
18%9%22%33%15%
780
December1st to 15thNight
21%10%25%31%10%
780
16th to endNight
26%11%24%31%6%
832
Page generated at 2018-02-13 20:45:58. Version ac04

Copyright 2018 A. Danko


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