Johnson City
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Johnson City 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
46%
16123
18%
48474
14%
16081
51%
16081
22%
32930

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%
779
16%
2522
10%
776
36%
776
14%
1834
January16th to endNight
26%
788
17%
2560
11%
788
35%
788
15%
1833
February1st to 15thNight
27%
704
16%
2202
9%
701
36%
701
17%
1537
February16th to endNight
19%
631
17%
1893
9%
631
28%
631
14%
1413
March1st to 15thNight
29%
720
18%
2008
12%
720
34%
720
19%
1431
March16th to endNight
35%
768
14%
2112
10%
768
38%
768
20%
1523
April1st to 15thNight
37%
716
18%
1956
10%
716
44%
716
25%
1294
April16th to endNight
45%
540
19%
1620
11%
540
51%
540
23%
1089
May1st to 15thNight
44%
540
13%
1620
9%
540
48%
540
20%
1140
May16th to endNight
60%
561
13%
1684
11%
561
62%
561
23%
1143
June1st to 15thNight
69%
540
12%
1620
10%
540
70%
540
26%
1073
June16th to endNight
67%
540
15%
1620
13%
540
69%
540
26%
1079
July1st to 15thNight
64%
510
9%
1530
7%
510
65%
510
23%
1061
July16th to endNight
73%
564
12%
1595
11%
531
74%
531
26%
1060
August1st to 15thNight
72%
539
16%
1609
15%
536
72%
536
25%
1081
August16th to endNight
70%
606
20%
1803
19%
606
70%
606
27%
1178
September1st to 15thNight
63%
720
19%
1980
17%
720
63%
720
26%
1339
September16th to endNight
62%
717
25%
1980
22%
717
64%
717
32%
1246
October1st to 15thNight
55%
720
27%
2071
25%
720
59%
720
32%
1277
October16th to endNight
48%
768
28%
2304
24%
768
56%
768
29%
1426
November1st to 15thNight
53%
760
26%
2411
23%
760
58%
760
29%
1452
November16th to endNight
45%
780
26%
2535
21%
780
53%
780
25%
1556
December1st to 15thNight
34%
780
16%
2535
13%
780
40%
780
16%
1819
December16th to endNight
28%
832
15%
2704
10%
832
35%
832
12%
2046

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
15%7%35%5%35%5%6%7%34%
49049
Night
14%7%35%43445%7%39%
48671
TransparencyDay
47%8%11%17%12%2
48750
Night
44%7%11%19%14%2
48474
SeeingDay
17%10%18%23%19%11%
5896
Night
17%9%19%30%20%2
16126

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%9%5%10%6%33446%29%
1746
16th to endDay
16%12%46%433445%33%
1768
February1st to 15thDay
16%12%5%8%5%34445%30%
1657
16th to endDay
20%12%47%42235%6%30%
1580
March1st to 15thDay
18%9%34324346%37%
1950
16th to endDay
20%10%35%42445%5%33%
2111
April1st to 15thDay
15%6%2342446%7%41%
2001
16th to endDay
16%6%25%5%35%5%46%37%
2340
May1st to 15thDay
18%5%36%6%45%5%5%7%32%
2331
16th to endDay
14%6%35%6%36%5%6%8%32%
2431
June1st to 15thDay
10%5%25%7%5%7%6%7%8%31%
2340
16th to endDay
9%5%26%6%36%7%8%8%33%
2340
July1st to 15thDay
14%5%37%7%46%6%6%9%26%
2340
16th to endDay
13%6%36%7%5%7%7%7%8%26%
2465
August1st to 15thDay
12%5%36%7%37%6%8%9%27%
2340
16th to endDay
12%5%25%6%46%7%8%8%31%
2384
September1st to 15thDay
13%6%36%6%45%5%6%7%35%
1980
16th to endDay
15%5%245%245%6%6%39%
1980
October1st to 15thDay
14%42432345%7%47%
1887
16th to endDay
17%7%24223345%46%
1920
November1st to 15thDay
14%6%34334346%46%
1776
16th to endDay
13%7%25%433346%44%
1755
December1st to 15thDay
16%11%36%425%446%33%
1755
16th to endDay
18%12%36%424446%31%
1872
January1st to 15thNight
17%10%49%5%23336%31%
2522
16th to endNight
17%12%46%5%3434433%
2560
February1st to 15thNight
15%10%46%424446%36%
2193
16th to endNight
18%13%48%424445%30%
1893
March1st to 15thNight
16%12%35%43335%5%37%
2008
16th to endNight
16%8%34434447%36%
2112
April1st to 15thNight
14%6%34424448%42%
1956
16th to endNight
14%6%25%5%35%45%6%41%
1620
May1st to 15thNight
15%6%36%5%2446%9%34%
1619
16th to endNight
10%4345%46%5%6%10%38%
1682
June1st to 15thNight
7%425%5%26%5%8%11%39%
1620
16th to endNight
7%435%5%45%46%11%41%
1620
July1st to 15thNight
10%5%346%35%6%7%10%35%
1620
16th to endNight
7%436%435%7%8%11%36%
1703
August1st to 15thNight
8%425%6%46%5%7%9%40%
1620
16th to endNight
9%425%5%35%5%8%9%39%
1803
September1st to 15thNight
12%5%344345%5%8%41%
1980
16th to endNight
13%42443325%6%50%
1980
October1st to 15thNight
14%423323346%50%
2071
16th to endNight
14%6%24223336%47%
2304
November1st to 15thNight
15%6%13313347%48%
2411
16th to endNight
11%8%24324446%46%
2535
December1st to 15thNight
16%9%5%7%43435%6%33%
2535
16th to endNight
20%12%46%5%345%46%27%
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
56%5%8%15%10%2
1747
16th to endDay
51%48%23%9%1
1768
February1st to 15thDay
57%5%6%17%13%
1659
16th to endDay
55%5%10%16%10%2
1580
March1st to 15thDay
48%5%7%20%15%3
1950
16th to endDay
52%6%11%18%9%1
2112
April1st to 15thDay
41%5%11%22%15%3
2001
16th to endDay
46%7%8%19%12%4
2340
May1st to 15thDay
49%8%12%17%9%1
2331
16th to endDay
46%9%15%18%8%1
2435
June1st to 15thDay
45%12%17%15%7%
2340
16th to endDay
42%13%13%15%13%1
2340
July1st to 15thDay
49%12%14%11%9%1
2201
16th to endDay
48%13%13%13%8%1
2310
August1st to 15thDay
47%14%14%14%8%
2327
16th to endDay
44%13%13%17%10%1
2384
September1st to 15thDay
45%10%11%16%11%3
1980
16th to endDay
42%8%12%17%16%2
1980
October1st to 15thDay
35%6%10%21%20%4
1887
16th to endDay
40%48%22%19%4
1920
November1st to 15thDay
40%47%16%25%5%
1776
16th to endDay
40%5%8%21%20%3
1755
December1st to 15thDay
50%6%9%19%11%2
1755
16th to endDay
54%5%12%14%10%1
1872
January1st to 15thNight
54%5%8%14%12%4
2522
16th to endNight
53%48%17%13%1
2560
February1st to 15thNight
50%410%19%12%2
2202
16th to endNight
55%5%8%18%9%2
1893
March1st to 15thNight
49%5%9%19%13%2
2008
16th to endNight
47%8%12%19%11%
2112
April1st to 15thNight
40%6%11%22%14%3
1956
16th to endNight
43%6%11%19%14%4
1620
May1st to 15thNight
45%9%15%19%8%
1620
16th to endNight
39%11%16%20%9%2
1684
June1st to 15thNight
35%12%21%18%10%
1620
16th to endNight
35%13%14%20%13%2
1620
July1st to 15thNight
40%12%17%16%10%2
1530
16th to endNight
34%13%20%18%9%2
1595
August1st to 15thNight
38%11%17%19%11%1
1609
16th to endNight
36%10%16%25%10%
1803
September1st to 15thNight
40%9%14%19%13%3
1980
16th to endNight
35%6%12%21%22%1
1980
October1st to 15thNight
35%5%9%24%21%3
2071
16th to endNight
37%5%7%22%21%5%
2304
November1st to 15thNight
37%48%19%23%7%
2411
16th to endNight
38%5%6%23%21%3
2535
December1st to 15thNight
52%6%9%16%11%3
2535
16th to endNight
57%7%9%12%11%1
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
25%28%27%14%3
135
16th to endDay
22%33%22%16%3
109
February1st to 15thDay
26%32%34%6%
90
16th to endDay
28%29%30%8%2
81
March1st to 15thDay
22%16%25%27%7%
240
16th to endDay
19%18%24%24%11%1
288
April1st to 15thDay
17%17%17%28%15%3
270
16th to endDay
18%8%23%21%19%7%
270
May1st to 15thDay
23%16%19%17%14%7%
288
16th to endDay
19%5%15%20%21%17%
331
June1st to 15thDay
11%315%26%27%14%
315
16th to endDay
13%6%17%23%23%15%
315
July1st to 15thDay
16%418%22%20%18%
305
16th to endDay
11%17%30%26%21%
326
August1st to 15thDay
14%113%24%26%19%
313
16th to endDay
14%17%22%27%26%
332
September1st to 15thDay
14%6%10%17%30%19%
315
16th to endDay
14%214%24%30%13%
314
October1st to 15thDay
16%7%14%27%24%9%
315
16th to endDay
21%10%16%25%21%5%
336
November1st to 15thDay
19%13%17%27%17%5%
194
16th to endDay
14%14%29%28%11%2
135
December1st to 15thDay
25%18%31%20%4
135
16th to endDay
28%20%36%12%1
144
January1st to 15thNight
23%19%24%27%5%
780
16th to endNight
23%17%28%27%3
788
February1st to 15thNight
22%19%27%27%3
704
16th to endNight
24%24%27%20%2
631
March1st to 15thNight
23%15%26%27%5%
720
16th to endNight
20%11%27%29%10%
768
April1st to 15thNight
18%16%24%28%11%
716
16th to endNight
16%9%23%34%14%1
540
May1st to 15thNight
18%6%23%33%16%1
540
16th to endNight
11%217%30%32%6%
563
June1st to 15thNight
8%19%38%35%5%
540
16th to endNight
9%210%35%37%4
540
July1st to 15thNight
13%28%28%41%4
510
16th to endNight
8%25%28%43%11%
564
August1st to 15thNight
8%26%32%44%6%
539
16th to endNight
11%6%30%43%7%
606
September1st to 15thNight
15%29%28%37%7%
720
16th to endNight
15%212%30%33%4
717
October1st to 15thNight
16%5%16%29%25%6%
720
16th to endNight
18%9%19%30%18%2
768
November1st to 15thNight
17%6%17%35%20%3
760
16th to endNight
17%14%21%32%13%1
780
December1st to 15thNight
22%14%22%31%8%
780
16th to endNight
27%13%24%28%6%
832
Page generated at 2018-01-21 12:19:24. Version ac04

Copyright 2018 A. Danko


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