Lexington
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lexington clear sky chart from 2005-11-05 to 2017-12-20.

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
44%
15782
20%
47885
15%
15738
50%
15738
25%
31082

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
18%
720
14%
2327
7%
716
27%
716
13%
1716
January16th to endNight
20%
768
17%
2496
9%
768
29%
768
16%
1756
February1st to 15thNight
20%
704
14%
2142
6%
701
30%
701
18%
1533
February16th to endNight
17%
631
15%
1893
6%
631
26%
631
15%
1386
March1st to 15thNight
25%
720
17%
2088
9%
720
32%
720
18%
1474
March16th to endNight
33%
768
15%
2112
9%
768
38%
768
22%
1476
April1st to 15thNight
36%
581
22%
1839
14%
581
47%
581
27%
1120
April16th to endNight
42%
540
21%
1661
13%
540
49%
540
25%
1085
May1st to 15thNight
39%
540
14%
1620
9%
540
44%
540
19%
1159
May16th to endNight
60%
562
19%
1684
15%
561
63%
561
29%
1062
June1st to 15thNight
68%
540
19%
1620
16%
540
71%
540
40%
905
June16th to endNight
67%
540
19%
1494
14%
540
70%
540
37%
898
July1st to 15thNight
60%
510
15%
1448
12%
510
62%
510
29%
930
July16th to endNight
75%
564
21%
1595
18%
531
77%
531
38%
907
August1st to 15thNight
77%
539
24%
1609
21%
536
79%
536
38%
938
August16th to endNight
76%
573
24%
1863
26%
573
77%
573
36%
1022
September1st to 15thNight
64%
669
25%
1929
22%
669
67%
669
32%
1190
September16th to endNight
62%
717
29%
1980
24%
717
64%
717
36%
1200
October1st to 15thNight
56%
720
31%
2010
25%
720
62%
720
38%
1171
October16th to endNight
41%
768
27%
2375
21%
768
51%
768
28%
1467
November1st to 15thNight
45%
760
27%
2471
24%
760
53%
760
29%
1444
November16th to endNight
35%
780
24%
2535
17%
780
44%
780
24%
1607
December1st to 15thNight
29%
780
15%
2535
8%
780
37%
780
17%
1765
December16th to endNight
23%
788
16%
2559
7%
788
34%
788
14%
1871

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
14%7%35%5%3445%7%37%
48930
Night
13%7%35%5%3445%7%40%
48076
Cloud CoverDay
14%7%36%5%35%45%7%37%
48940
Night
13%6%35%5%3445%7%40%
48080
TransparencyDay
45%5%11%21%14%2
48639
Night
42%5%10%22%15%3
47885
SeeingDay
17%6%21%22%19%12%
5784
Night
17%7%24%28%18%2
15783

By Month

Percentage Cloud Cover NE (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
20%10%49%434445%28%
1611
16th to endDay
17%11%5%7%5%23446%31%
1728
February1st to 15thDay
16%11%5%9%5%24445%30%
1719
16th to endDay
16%10%48%6%36%35%6%28%
1580
March1st to 15thDay
23%8%36%43334434%
1861
16th to endDay
18%8%36%6%3445%6%31%
2112
April1st to 15thDay
15%7%25%5%34446%39%
2118
16th to endDay
16%6%25%5%2445%8%37%
2298
May1st to 15thDay
21%7%35%5%3445%7%31%
2331
16th to endDay
10%5%26%6%45%5%6%9%37%
2431
June1st to 15thDay
9%4345%35%6%6%8%41%
2340
16th to endDay
7%435%5%36%6%7%9%39%
2458
July1st to 15thDay
13%7%35%5%35%5%7%9%34%
2415
16th to endDay
9%5%25%6%47%7%7%9%34%
2465
August1st to 15thDay
9%5%15%5%36%6%7%9%38%
2340
16th to endDay
8%5%26%6%45%5%7%9%37%
2336
September1st to 15thDay
14%5%15%5%26%6%5%7%38%
2019
16th to endDay
13%5%25%423445%47%
1980
October1st to 15thDay
11%6%13433445%50%
1949
16th to endDay
18%5%23413335%46%
1848
November1st to 15thDay
13%6%24424335%48%
1717
16th to endDay
16%8%44423336%42%
1755
December1st to 15thDay
22%10%36%435%345%31%
1755
16th to endDay
19%13%37%433436%30%
1764
January1st to 15thNight
18%10%5%8%7%35%44427%
2327
16th to endNight
17%10%47%5%3434433%
2496
February1st to 15thNight
19%9%47%5%2435%5%32%
2140
16th to endNight
18%11%48%5%34345%29%
1893
March1st to 15thNight
17%9%37%5%23445%35%
2076
16th to endNight
15%8%47%5%2435%8%35%
2112
April1st to 15thNight
12%5%25%5%2445%7%44%
1839
16th to endNight
13%6%35%435%446%40%
1661
May1st to 15thNight
17%6%35%6%35%7%6%7%31%
1620
16th to endNight
8%425%6%45%6%7%10%40%
1682
June1st to 15thNight
5%3234245%7%11%48%
1620
16th to endNight
5%2245%25%6%6%13%44%
1494
July1st to 15thNight
9%5%25%5%4446%8%42%
1536
16th to endNight
5%314425%5%6%11%48%
1703
August1st to 15thNight
5%2135%35%5%6%10%50%
1620
16th to endNight
6%4134345%6%10%50%
1863
September1st to 15thNight
12%4134245%48%46%
1929
16th to endNight
9%5%245%24346%51%
1980
October1st to 15thNight
9%5%2332345%8%50%
2010
16th to endNight
15%5%25%434345%46%
2375
November1st to 15thNight
13%5%24323336%49%
2471
16th to endNight
17%7%25%423345%42%
2535
December1st to 15thNight
21%9%36%424445%32%
2535
16th to endNight
21%12%46%424446%28%
2559

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
20%9%49%5%34435%27%
1611
16th to endDay
17%11%5%7%5%24445%31%
1728
February1st to 15thDay
16%10%5%9%5%24445%30%
1719
16th to endDay
16%10%48%6%45%35%6%28%
1580
March1st to 15thDay
23%8%36%43334433%
1872
16th to endDay
18%8%26%6%25%45%6%32%
2111
April1st to 15thDay
14%7%26%5%34446%39%
2118
16th to endDay
16%6%245%3445%8%37%
2298
May1st to 15thDay
20%7%25%5%3445%7%32%
2331
16th to endDay
10%5%26%6%35%5%5%9%38%
2431
June1st to 15thDay
9%425%5%36%6%6%8%41%
2340
16th to endDay
7%435%5%36%6%6%9%40%
2458
July1st to 15thDay
13%7%35%435%5%7%9%34%
2415
16th to endDay
9%5%247%47%7%7%9%34%
2465
August1st to 15thDay
9%5%15%5%46%5%6%10%39%
2340
16th to endDay
8%5%26%6%36%6%7%9%37%
2336
September1st to 15thDay
13%5%25%5%36%6%5%7%38%
2019
16th to endDay
13%5%25%42335%5%47%
1980
October1st to 15thDay
11%5%14423446%50%
1949
16th to endDay
18%5%24423325%46%
1848
November1st to 15thDay
13%6%24423335%48%
1717
16th to endDay
16%8%35%423336%42%
1755
December1st to 15thDay
22%10%35%435%345%31%
1755
16th to endDay
19%13%37%423446%30%
1764
January1st to 15thNight
18%10%6%8%7%3444427%
2327
16th to endNight
17%10%5%7%5%3434433%
2496
February1st to 15thNight
19%9%47%5%24446%32%
2133
16th to endNight
18%12%47%6%34345%29%
1893
March1st to 15thNight
17%9%37%433445%35%
2088
16th to endNight
15%8%37%5%2435%7%36%
2112
April1st to 15thNight
12%5%35%5%2445%7%44%
1839
16th to endNight
13%6%35%5%35%447%40%
1661
May1st to 15thNight
17%6%35%6%35%6%6%7%31%
1619
16th to endNight
8%425%6%446%7%10%40%
1682
June1st to 15thNight
5%3224345%7%11%48%
1620
16th to endNight
5%2245%25%6%7%13%44%
1494
July1st to 15thNight
9%5%25%5%35%45%8%43%
1536
16th to endNight
5%324435%5%7%11%48%
1703
August1st to 15thNight
5%313435%5%6%10%50%
1620
16th to endNight
5%3135%245%6%10%50%
1863
September1st to 15thNight
12%4234345%5%8%46%
1929
16th to endNight
10%424434345%51%
1980
October1st to 15thNight
9%41432345%8%51%
2010
16th to endNight
15%5%25%434345%46%
2375
November1st to 15thNight
13%5%24323336%49%
2471
16th to endNight
17%7%25%324345%42%
2535
December1st to 15thNight
21%9%36%42345%6%32%
2535
16th to endNight
21%12%46%434446%28%
2559

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
58%38%18%10%
1612
16th to endDay
54%310%23%7%1
1728
February1st to 15thDay
56%47%22%7%1
1721
16th to endDay
55%410%19%8%
1580
March1st to 15thDay
53%311%18%11%1
1872
16th to endDay
51%411%21%9%
2112
April1st to 15thDay
44%49%24%13%2
2118
16th to endDay
44%411%22%13%4
2298
May1st to 15thDay
50%5%12%19%10%1
2331
16th to endDay
41%6%14%23%12%1
2435
June1st to 15thDay
38%7%13%25%14%1
2340
16th to endDay
37%8%13%20%18%2
2458
July1st to 15thDay
43%7%13%15%15%3
2274
16th to endDay
40%8%14%22%11%2
2310
August1st to 15thDay
38%8%13%22%15%1
2327
16th to endDay
39%7%10%23%15%4
2336
September1st to 15thDay
42%6%11%17%16%5%
2019
16th to endDay
37%48%23%23%2
1980
October1st to 15thDay
34%38%26%22%3
1949
16th to endDay
41%38%26%18%2
1848
November1st to 15thDay
39%37%24%19%5%
1717
16th to endDay
44%27%24%19%1
1755
December1st to 15thDay
56%310%18%9%1
1755
16th to endDay
55%411%20%7%
1764
January1st to 15thNight
58%38%14%12%1
2327
16th to endNight
54%38%21%10%1
2496
February1st to 15thNight
53%310%22%9%1
2142
16th to endNight
56%310%19%9%
1893
March1st to 15thNight
50%48%20%13%2
2088
16th to endNight
47%5%12%23%10%
2112
April1st to 15thNight
38%49%22%20%4
1839
16th to endNight
42%5%9%21%13%6%
1661
May1st to 15thNight
48%8%10%20%9%2
1620
16th to endNight
36%8%14%22%15%3
1684
June1st to 15thNight
27%5%17%29%16%3
1620
16th to endNight
30%7%18%23%16%4
1494
July1st to 15thNight
39%6%12%21%15%4
1448
16th to endNight
27%7%16%27%17%2
1595
August1st to 15thNight
28%7%15%25%19%3
1609
16th to endNight
27%7%13%26%20%4
1863
September1st to 15thNight
35%6%11%21%19%6%
1929
16th to endNight
34%37%23%26%3
1980
October1st to 15thNight
30%49%26%22%5%
2010
16th to endNight
40%36%25%21%3
2375
November1st to 15thNight
36%36%24%23%5%
2471
16th to endNight
43%38%24%19%1
2535
December1st to 15thNight
52%310%19%11%1
2535
16th to endNight
56%5%9%18%8%1
2559

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
31%15%38%7%42
90
16th to endDay
25%21%40%10%2
96
February1st to 15thDay
15%28%36%15%3
90
16th to endDay
22%12%39%22%3
81
March1st to 15thDay
29%16%33%18%1
162
16th to endDay
21%12%31%21%10%2
288
April1st to 15thDay
18%14%23%26%12%3
270
16th to endDay
21%6%25%25%13%7%
270
May1st to 15thDay
25%8%27%17%14%6%
288
16th to endDay
17%321%25%16%16%
331
June1st to 15thDay
10%214%23%33%14%
315
16th to endDay
9%323%27%23%12%
433
July1st to 15thDay
20%215%25%21%14%
378
16th to endDay
11%16%24%26%28%
326
August1st to 15thDay
12%110%19%30%25%
313
16th to endDay
10%28%28%30%20%
332
September1st to 15thDay
16%210%20%29%20%
315
16th to endDay
14%212%20%30%19%
314
October1st to 15thDay
15%5%20%24%22%11%
315
16th to endDay
16%6%28%28%16%4
264
November1st to 15thDay
19%5%27%23%17%5%
135
16th to endDay
22%8%30%28%8%1
135
December1st to 15thDay
20%15%34%23%41
135
16th to endDay
26%21%41%7%2
108
January1st to 15thNight
24%15%36%18%5%
720
16th to endNight
25%13%35%23%2
768
February1st to 15thNight
25%12%35%25%1
704
16th to endNight
24%12%40%19%2
631
March1st to 15thNight
22%12%32%25%6%
720
16th to endNight
19%10%31%26%11%
768
April1st to 15thNight
15%11%33%29%10%
581
16th to endNight
15%5%32%30%13%1
540
May1st to 15thNight
22%327%27%16%2
540
16th to endNight
11%216%36%27%5%
563
June1st to 15thNight
7%15%42%30%3
540
16th to endNight
7%15%40%31%4
540
July1st to 15thNight
12%213%34%32%5%
510
16th to endNight
8%16%34%40%9%
564
August1st to 15thNight
7%6%35%43%6%
539
16th to endNight
6%17%35%41%6%
573
September1st to 15thNight
15%110%26%38%7%
669
16th to endNight
12%214%29%35%5%
717
October1st to 15thNight
11%421%29%27%5%
720
16th to endNight
18%5%29%29%15%2
768
November1st to 15thNight
16%6%26%27%19%2
760
16th to endNight
22%9%29%27%10%
780
December1st to 15thNight
26%11%26%27%7%
780
16th to endNight
28%11%31%23%4
788
Page generated at 2017-12-21 07:04:55. Version ac04

Copyright 2017 A. Danko


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