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 2017-08-12.

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
43%
15282
20%
46355
14%
15238
50%
15238
25%
30192

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
30%
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
41%
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
62%
561
29%
1062
June1st to 15thNight
69%
540
19%
1620
16%
540
72%
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
78%
531
38%
907
August1st to 15thNight
78%
527
24%
1575
22%
524
80%
524
39%
910
August16th to endNight
76%
525
22%
1707
24%
525
76%
525
35%
945
September1st to 15thNight
66%
613
26%
1768
24%
613
69%
613
32%
1087
September16th to endNight
60%
657
27%
1815
22%
657
63%
657
33%
1126
October1st to 15thNight
55%
660
32%
1842
26%
660
61%
660
38%
1073
October16th to endNight
41%
704
26%
2177
19%
704
51%
704
28%
1349
November1st to 15thNight
46%
700
29%
2276
24%
700
56%
700
31%
1296
November16th to endNight
33%
720
22%
2340
15%
720
42%
720
23%
1513
December1st to 15thNight
28%
720
14%
2340
9%
720
34%
720
16%
1662
December16th to endNight
23%
768
16%
2496
7%
768
34%
768
14%
1824

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%35%45%7%37%
47592
Night
14%7%35%5%3445%7%40%
46546
Cloud CoverDay
14%7%36%5%35%45%7%37%
47602
Night
13%6%35%5%3445%7%40%
46550
TransparencyDay
45%5%11%21%14%2
47301
Night
42%5%10%22%15%3
46355
SeeingDay
17%6%21%22%19%12%
5319
Night
17%7%24%28%18%2
15283

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%10%39%
2288
16th to endDay
8%5%26%6%35%5%7%9%37%
2140
September1st to 15thDay
12%5%16%5%26%6%5%8%38%
1851
16th to endDay
14%5%35%42345%5%46%
1815
October1st to 15thDay
11%5%1343345%5%50%
1787
16th to endDay
19%5%23414325%46%
1694
November1st to 15thDay
12%6%24424335%50%
1582
16th to endDay
17%8%44423336%40%
1620
December1st to 15thDay
23%11%46%435%34429%
1620
16th to endDay
19%13%37%433436%30%
1728
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%213435%5%6%10%51%
1586
16th to endNight
6%413435%5%5%9%50%
1707
September1st to 15thNight
10%423435%5%5%9%45%
1768
16th to endNight
10%5%245%25%345%50%
1815
October1st to 15thNight
9%5%2332345%8%51%
1842
16th to endNight
16%5%25%434345%46%
2177
November1st to 15thNight
13%5%24323336%51%
2276
16th to endNight
18%8%25%424345%40%
2340
December1st to 15thNight
22%10%36%423445%31%
2340
16th to endNight
21%12%46%424446%28%
2496

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%36%5%6%10%39%
2288
16th to endDay
8%5%27%5%35%5%7%9%37%
2140
September1st to 15thDay
12%5%25%5%36%6%6%7%38%
1851
16th to endDay
14%5%35%42335%5%45%
1815
October1st to 15thDay
11%5%13423446%50%
1787
16th to endDay
19%5%24423325%46%
1694
November1st to 15thDay
12%6%24423335%50%
1582
16th to endDay
17%8%45%423336%40%
1620
December1st to 15thDay
23%11%35%435%34429%
1620
16th to endDay
19%13%37%423446%30%
1728
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%3134345%6%10%51%
1586
16th to endNight
5%4135%25%5%5%9%50%
1707
September1st to 15thNight
10%423435%5%5%8%45%
1768
16th to endNight
10%5%245%34345%49%
1815
October1st to 15thNight
9%42332345%8%51%
1842
16th to endNight
15%5%25%434445%46%
2177
November1st to 15thNight
13%5%24313336%51%
2276
16th to endNight
18%8%25%324345%40%
2340
December1st to 15thNight
22%9%36%423445%31%
2340
16th to endNight
21%11%46%434346%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
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
2275
16th to endDay
40%7%10%22%15%4
2140
September1st to 15thDay
41%6%12%16%17%5%
1851
16th to endDay
39%47%21%24%2
1815
October1st to 15thDay
34%38%26%22%4
1787
16th to endDay
42%38%26%17%2
1694
November1st to 15thDay
37%37%24%21%6%
1582
16th to endDay
46%28%22%19%1
1620
December1st to 15thDay
57%39%18%8%1
1620
16th to endDay
55%411%20%7%
1728
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
27%7%15%25%20%3
1575
16th to endNight
28%6%13%24%21%4
1707
September1st to 15thNight
34%6%11%20%20%6%
1768
16th to endNight
36%36%21%26%3
1815
October1st to 15thNight
30%48%27%22%5%
1842
16th to endNight
40%36%26%20%3
2177
November1st to 15thNight
34%36%24%24%6%
2276
16th to endNight
45%38%23%17%1
2340
December1st to 15thNight
54%311%18%10%1
2340
16th to endNight
56%49%18%9%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
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%18%30%27%
297
16th to endDay
11%27%24%30%23%
268
September1st to 15thDay
13%19%19%32%24%
255
16th to endDay
18%212%21%29%15%
254
October1st to 15thDay
15%421%25%20%12%
255
16th to endDay
17%427%30%17%1
206
November1st to 15thDay
15%5%24%22%23%8%
90
16th to endDay
27%12%30%24%5%
90
December1st to 15thDay
22%15%32%25%22
90
16th to endDay
25%20%42%8%3
96
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%34%43%6%
527
16th to endNight
6%18%34%41%7%
525
September1st to 15thNight
14%19%27%38%7%
613
16th to endNight
13%314%31%32%4
657
October1st to 15thNight
11%422%30%25%5%
660
16th to endNight
19%5%29%29%14%1
704
November1st to 15thNight
16%6%26%27%20%3
700
16th to endNight
23%10%29%26%10%
720
December1st to 15thNight
28%10%26%25%7%
720
16th to endNight
28%12%30%23%4
768
Page generated at 2017-08-13 14:16:16. Version ac04

Copyright 2017 A. Danko


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