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 2017-04-30.

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%
14976
20%
45454
14%
14932
49%
14932
25%
29663

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%
537
21%
1653
13%
537
49%
537
25%
1082
May1st to 15thNight
40%
495
15%
1485
9%
495
45%
495
19%
1068
May16th to endNight
62%
514
19%
1540
15%
513
64%
513
29%
972
June1st to 15thNight
67%
495
20%
1485
17%
495
70%
495
39%
841
June16th to endNight
69%
495
18%
1370
14%
495
70%
495
37%
821
July1st to 15thNight
60%
465
16%
1320
12%
465
61%
465
29%
854
July16th to endNight
75%
522
19%
1469
16%
489
78%
489
37%
845
August1st to 15thNight
78%
494
26%
1474
23%
491
80%
491
40%
844
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%36%
46250
Night
14%7%35%5%3445%7%40%
45645
Cloud CoverDay
14%7%36%5%35%45%7%36%
46260
Night
14%7%35%5%3445%7%40%
45649
TransparencyDay
45%5%11%21%13%2
45959
Night
43%5%10%22%15%3
45454
SeeingDay
17%6%21%22%19%12%
4895
Night
18%7%24%28%18%2
14977

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%
2285
May1st to 15thDay
21%7%35%5%3446%7%30%
2136
16th to endDay
9%5%26%6%45%5%5%9%37%
2223
June1st to 15thDay
9%5%35%5%45%6%6%8%39%
2145
16th to endDay
7%435%6%46%6%7%9%38%
2253
July1st to 15thDay
14%7%35%5%36%5%7%9%32%
2214
16th to endDay
9%5%25%6%48%7%7%9%32%
2283
August1st to 15thDay
9%5%15%5%36%6%7%10%39%
2145
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%447%40%
1653
May1st to 15thNight
17%6%35%6%35%7%6%7%30%
1485
16th to endNight
8%425%6%45%5%6%9%40%
1538
June1st to 15thNight
5%3244345%7%11%47%
1485
16th to endNight
5%2245%25%7%7%13%44%
1370
July1st to 15thNight
10%5%25%5%3446%8%42%
1408
16th to endNight
6%314435%5%7%11%46%
1577
August1st to 15thNight
4213435%5%6%10%52%
1485
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%
2285
May1st to 15thDay
21%7%35%5%35%46%7%30%
2136
16th to endDay
9%5%26%6%35%5%5%9%38%
2223
June1st to 15thDay
9%435%5%36%6%6%8%39%
2145
16th to endDay
7%435%5%36%6%7%9%38%
2253
July1st to 15thDay
14%7%25%436%5%7%9%32%
2214
16th to endDay
9%5%25%7%48%7%7%9%32%
2283
August1st to 15thDay
9%5%15%5%46%6%6%10%39%
2145
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%
1653
May1st to 15thNight
17%6%35%6%35%6%6%7%30%
1484
16th to endNight
8%425%6%45%5%6%10%40%
1538
June1st to 15thNight
5%3225%345%8%11%47%
1485
16th to endNight
5%2245%25%7%7%13%44%
1370
July1st to 15thNight
9%5%25%5%35%45%8%42%
1408
16th to endNight
6%324336%5%7%11%46%
1577
August1st to 15thNight
5%334345%6%10%52%
1485
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%410%22%13%4
2285
May1st to 15thDay
51%5%12%18%10%
2136
16th to endDay
41%6%14%22%12%1
2227
June1st to 15thDay
39%7%12%25%13%1
2145
16th to endDay
38%8%13%19%16%2
2253
July1st to 15thDay
44%8%13%15%15%2
2073
16th to endDay
41%8%15%22%10%1
2128
August1st to 15thDay
37%8%13%23%16%1
2132
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
43%5%9%21%13%6%
1653
May1st to 15thNight
49%8%10%20%9%2
1485
16th to endNight
36%7%14%21%15%3
1540
June1st to 15thNight
28%5%17%29%15%3
1485
16th to endNight
29%7%19%23%15%5%
1370
July1st to 15thNight
40%5%12%20%16%5%
1320
16th to endNight
28%7%17%28%15%2
1469
August1st to 15thNight
26%7%15%26%20%3
1474
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%
266
May1st to 15thDay
25%7%25%16%16%8%
228
16th to endDay
16%317%25%18%18%
267
June1st to 15thDay
11%315%22%33%13%
255
16th to endDay
9%321%27%25%13%
363
July1st to 15thDay
22%214%25%19%15%
312
16th to endDay
13%15%23%24%31%
270
August1st to 15thDay
11%9%20%28%30%
253
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
16%5%32%30%13%1
537
May1st to 15thNight
23%325%28%17%2
495
16th to endNight
11%214%37%28%5%
515
June1st to 15thNight
7%16%43%28%3
495
16th to endNight
7%14%40%32%5%
495
July1st to 15thNight
13%213%33%31%6%
465
16th to endNight
8%16%34%39%9%
522
August1st to 15thNight
7%6%34%44%6%
494
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 2017-04-30 20:40:13. Version ac04

Copyright 2017 A. Danko


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