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 2017-09-20.

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%
15635
18%
46952
14%
15593
51%
15593
22%
31987

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
27%
719
16%
2327
10%
716
35%
716
13%
1707
January16th to endNight
25%
768
17%
2496
10%
768
35%
768
15%
1798
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
60%
677
23%
1870
20%
677
63%
677
31%
1197
October1st to 15thNight
53%
660
28%
1898
25%
660
58%
660
31%
1178
October16th to endNight
47%
704
26%
2112
22%
704
55%
704
28%
1321
November1st to 15thNight
53%
700
27%
2221
24%
700
59%
700
30%
1317
November16th to endNight
42%
720
24%
2340
19%
720
51%
720
24%
1459
December1st to 15thNight
35%
720
16%
2340
14%
720
39%
720
16%
1687
December16th to endNight
29%
768
16%
2496
11%
768
36%
768
12%
1882

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%
47882
Night
14%7%35%43445%7%38%
47149
TransparencyDay
47%8%11%17%12%2
47583
Night
44%7%11%19%14%2
46952
SeeingDay
17%10%17%22%19%11%
5482
Night
17%9%19%29%20%2
15638

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
18%9%5%10%5%23445%29%
1611
16th to endDay
16%12%46%43345%5%32%
1728
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
16%6%245%245%6%6%39%
1859
October1st to 15thDay
15%42442345%7%46%
1730
16th to endDay
18%7%24323335%45%
1760
November1st to 15thDay
13%6%23323246%49%
1636
16th to endDay
14%7%35%43345%6%42%
1620
December1st to 15thDay
17%11%26%435%45%6%33%
1620
16th to endDay
19%12%36%434346%31%
1728
January1st to 15thNight
17%10%410%5%23336%30%
2327
16th to endNight
17%12%46%43434432%
2496
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%49%
1870
October1st to 15thNight
15%424323346%49%
1898
16th to endNight
15%6%24223436%47%
2112
November1st to 15thNight
14%7%13313337%50%
2221
16th to endNight
12%8%24424446%45%
2340
December1st to 15thNight
16%10%5%7%434346%32%
2340
16th to endNight
20%12%46%5%34446%28%
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
57%5%8%15%10%2
1612
16th to endDay
51%48%23%9%1
1728
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%16%17%2
1859
October1st to 15thDay
36%6%10%20%20%4
1730
16th to endDay
41%48%22%18%4
1760
November1st to 15thDay
37%37%17%27%6%
1636
16th to endDay
42%5%8%21%18%3
1620
December1st to 15thDay
49%6%9%18%12%2
1620
16th to endDay
54%5%12%14%11%1
1728
January1st to 15thNight
55%5%7%14%12%4
2327
16th to endNight
54%5%8%17%13%1
2496
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
37%6%12%19%22%1
1870
October1st to 15thNight
35%6%9%23%21%3
1898
16th to endNight
38%5%7%22%20%5%
2112
November1st to 15thNight
36%38%18%25%7%
2221
16th to endNight
39%5%7%24%19%3
2340
December1st to 15thNight
52%6%9%15%11%3
2340
16th to endNight
57%7%8%12%12%1
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
30%28%25%10%41
90
16th to endDay
25%35%23%12%3
96
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
16%215%23%29%13%
270
October1st to 15thDay
18%9%15%26%21%10%
255
16th to endDay
21%9%17%26%21%4
272
November1st to 15thDay
14%15%17%26%18%6%
144
16th to endDay
18%15%28%27%7%1
90
December1st to 15thDay
24%21%30%18%5%
90
16th to endDay
27%23%29%17%2
96
January1st to 15thNight
23%20%25%24%5%
720
16th to endNight
24%17%28%26%2
768
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
16%312%31%32%4
677
October1st to 15thNight
16%6%17%29%24%6%
660
16th to endNight
18%9%19%32%17%2
704
November1st to 15thNight
17%7%17%34%20%3
700
16th to endNight
17%15%21%31%12%1
720
December1st to 15thNight
22%13%22%30%9%
720
16th to endNight
27%13%23%28%6%
768
Page generated at 2017-09-21 07:18:13. Version ac04

Copyright 2017 A. Danko


Johnson City Clear Sky Chart | Charts Home