This page made possible by the sponsorship of: Jerome Hollon.

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 2020-06-03.

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%
18981
20%
57616
14%
18937
49%
18937
24%
37862

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
19%
900
14%
2912
7%
896
28%
896
13%
2155
January16th to endNight
20%
960
17%
3120
9%
960
30%
960
15%
2227
February1st to 15thNight
19%
884
14%
2690
6%
881
28%
881
16%
1965
February16th to endNight
17%
791
15%
2373
6%
791
25%
791
14%
1764
March1st to 15thNight
24%
900
17%
2610
8%
900
31%
900
18%
1852
March16th to endNight
31%
960
15%
2640
8%
960
36%
960
21%
1867
April1st to 15thNight
36%
727
21%
2300
14%
727
47%
727
25%
1435
April16th to endNight
39%
669
20%
2055
12%
669
48%
669
24%
1365
May1st to 15thNight
39%
675
15%
2025
10%
675
44%
675
20%
1420
May16th to endNight
59%
706
17%
2116
13%
705
62%
705
27%
1366
June1st to 15thNight
65%
637
19%
1913
16%
637
68%
637
38%
1095
June16th to endNight
67%
630
19%
1744
15%
630
69%
630
36%
1064
July1st to 15thNight
64%
600
16%
1704
14%
600
65%
600
31%
1069
July16th to endNight
74%
660
21%
1883
18%
627
76%
627
36%
1098
August1st to 15thNight
77%
620
24%
1850
22%
617
79%
617
37%
1088
August16th to endNight
74%
669
22%
2175
24%
669
75%
669
35%
1206
September1st to 15thNight
64%
780
24%
2250
21%
780
67%
780
32%
1391
September16th to endNight
62%
837
29%
2310
23%
837
65%
837
35%
1399
October1st to 15thNight
57%
840
31%
2344
25%
840
62%
840
38%
1365
October16th to endNight
41%
896
26%
2771
20%
896
50%
896
28%
1717
November1st to 15thNight
42%
880
26%
2861
22%
880
51%
880
27%
1722
November16th to endNight
35%
900
22%
2925
16%
900
44%
900
22%
1903
December1st to 15thNight
27%
900
15%
2925
8%
900
35%
900
16%
2054
December16th to endNight
24%
960
17%
3120
8%
960
35%
960
14%
2275

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%345%5%7%36%
58772
Night
14%7%35%5%3445%7%39%
57807
Cloud CoverDay
15%7%36%5%3445%7%36%
58782
Night
14%7%35%5%3445%7%39%
57811
TransparencyDay
45%5%11%21%13%2
58481
Night
43%5%10%22%15%2
57616
SeeingDay
18%8%22%22%17%10%
9024
Night
18%7%24%28%18%2
18982

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%9%48%5%34445%28%
2016
16th to endDay
17%11%5%7%7%24445%30%
2160
February1st to 15thDay
21%11%48%5%2444428%
2161
16th to endDay
18%10%47%6%35%445%27%
1980
March1st to 15thDay
22%9%36%43344432%
2329
16th to endDay
20%8%36%6%3445%6%31%
2640
April1st to 15thDay
15%7%35%5%3345%6%39%
2650
16th to endDay
17%6%25%5%3445%7%36%
2839
May1st to 15thDay
20%7%35%5%3445%7%33%
2916
16th to endDay
10%5%26%7%35%5%6%9%36%
3055
June1st to 15thDay
9%425%5%35%6%6%8%41%
2756
16th to endDay
8%425%5%35%6%6%9%39%
2868
July1st to 15thDay
12%6%35%5%35%5%7%8%36%
2818
16th to endDay
9%5%25%6%47%7%7%9%35%
2881
August1st to 15thDay
9%5%15%5%36%6%7%9%39%
2682
16th to endDay
8%5%26%6%45%5%6%9%37%
2728
September1st to 15thDay
13%5%25%5%26%6%5%7%40%
2356
16th to endDay
14%5%25%423446%46%
2310
October1st to 15thDay
11%5%1343345%6%49%
2274
16th to endDay
18%5%23413335%46%
2156
November1st to 15thDay
15%6%24423335%47%
1987
16th to endDay
16%9%45%422346%39%
2025
December1st to 15thDay
22%11%46%435%34430%
2025
16th to endDay
20%12%37%433446%29%
2160
January1st to 15thNight
18%10%5%8%7%35%43428%
2912
16th to endNight
17%10%48%6%3434432%
3120
February1st to 15thNight
22%9%47%5%23346%29%
2688
16th to endNight
19%11%48%5%3435%5%28%
2373
March1st to 15thNight
19%8%37%5%24445%34%
2598
16th to endNight
16%8%46%6%24347%35%
2640
April1st to 15thNight
14%5%25%5%24447%42%
2300
16th to endNight
14%7%36%435%446%39%
2055
May1st to 15thNight
16%6%35%6%346%5%7%33%
2025
16th to endNight
9%426%5%45%5%7%11%38%
2114
June1st to 15thNight
6%4244245%7%11%46%
1913
16th to endNight
6%2235%25%6%6%12%43%
1744
July1st to 15thNight
8%425%5%3446%9%44%
1792
16th to endNight
6%314435%5%6%10%47%
1991
August1st to 15thNight
5%213435%6%6%10%49%
1861
16th to endNight
6%4135%3446%10%49%
2175
September1st to 15thNight
11%4134245%5%9%44%
2250
16th to endNight
10%4245%24346%51%
2310
October1st to 15thNight
10%42332345%8%51%
2344
16th to endNight
17%5%24433345%46%
2771
November1st to 15thNight
14%6%35%323336%47%
2861
16th to endNight
17%8%35%423345%40%
2925
December1st to 15thNight
21%10%36%424445%32%
2925
16th to endNight
20%12%36%5%24446%28%
3120

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%10%48%5%35%445%27%
2016
16th to endDay
17%10%5%7%6%24445%30%
2160
February1st to 15thDay
20%11%48%5%2444428%
2161
16th to endDay
18%10%48%6%35%35%5%27%
1980
March1st to 15thDay
22%9%37%43344432%
2340
16th to endDay
20%8%36%6%3445%6%31%
2639
April1st to 15thDay
14%7%26%5%3345%6%39%
2650
16th to endDay
17%7%25%5%3445%7%36%
2839
May1st to 15thDay
19%7%25%5%3445%7%33%
2916
16th to endDay
10%6%26%7%35%5%6%9%36%
3055
June1st to 15thDay
9%425%5%36%6%5%7%41%
2756
16th to endDay
7%435%5%36%6%6%9%39%
2868
July1st to 15thDay
11%6%25%5%35%5%6%9%36%
2818
16th to endDay
9%5%246%47%6%7%9%35%
2881
August1st to 15thDay
9%5%15%5%46%6%6%10%39%
2682
16th to endDay
8%5%26%5%45%6%7%9%37%
2728
September1st to 15thDay
12%5%245%35%5%5%7%40%
2356
16th to endDay
14%5%25%42335%6%46%
2310
October1st to 15thDay
11%5%1342345%6%49%
2274
16th to endDay
18%5%24423335%46%
2156
November1st to 15thDay
15%6%24423335%47%
1987
16th to endDay
16%9%45%423336%39%
2025
December1st to 15thDay
21%11%46%5%3434430%
2025
16th to endDay
20%12%37%423446%29%
2160
January1st to 15thNight
18%10%5%7%7%35%44427%
2912
16th to endNight
17%10%5%8%6%3434432%
3120
February1st to 15thNight
21%9%37%5%23446%30%
2681
16th to endNight
19%11%37%6%3435%5%28%
2373
March1st to 15thNight
18%8%37%433445%34%
2610
16th to endNight
16%8%37%5%34346%35%
2640
April1st to 15thNight
13%5%25%5%2445%7%42%
2300
16th to endNight
13%7%36%5%35%446%39%
2055
May1st to 15thNight
16%6%35%6%346%5%7%33%
2024
16th to endNight
9%425%6%45%5%7%11%37%
2114
June1st to 15thNight
6%4234345%7%11%46%
1913
16th to endNight
5%2245%25%6%7%13%43%
1744
July1st to 15thNight
8%5%25%5%35%45%9%45%
1792
16th to endNight
6%324435%5%7%10%47%
1991
August1st to 15thNight
5%313435%6%6%10%49%
1861
16th to endNight
6%4135%245%6%10%49%
2175
September1st to 15thNight
11%5%234345%5%8%45%
2250
16th to endNight
10%424434345%51%
2310
October1st to 15thNight
10%41332345%8%51%
2344
16th to endNight
16%5%24423345%46%
2771
November1st to 15thNight
14%5%34324336%47%
2861
16th to endNight
17%7%36%424345%40%
2925
December1st to 15thNight
21%9%46%423445%32%
2925
16th to endNight
20%12%46%5%34446%28%
3120

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%17%10%1
2017
16th to endDay
55%39%21%8%1
2160
February1st to 15thDay
58%46%20%7%1
2163
16th to endDay
57%49%18%8%1
1980
March1st to 15thDay
54%310%18%12%1
2340
16th to endDay
52%411%20%9%
2640
April1st to 15thDay
44%411%24%12%2
2650
16th to endDay
46%410%21%12%4
2839
May1st to 15thDay
49%5%12%20%10%1
2916
16th to endDay
42%7%15%22%10%1
3059
June1st to 15thDay
38%7%12%26%14%1
2756
16th to endDay
37%8%13%21%16%2
2868
July1st to 15thDay
41%8%13%18%15%2
2677
16th to endDay
39%8%13%23%12%2
2726
August1st to 15thDay
37%8%13%24%14%1
2669
16th to endDay
39%7%10%23%15%3
2728
September1st to 15thDay
40%6%13%17%16%5%
2356
16th to endDay
38%48%25%21%2
2310
October1st to 15thDay
35%49%25%21%3
2274
16th to endDay
40%37%25%19%2
2156
November1st to 15thDay
40%38%24%19%4
1987
16th to endDay
46%28%24%17%1
2025
December1st to 15thDay
57%310%18%9%1
2025
16th to endDay
56%411%20%7%
2160
January1st to 15thNight
58%47%15%12%1
2912
16th to endNight
55%38%20%10%1
3120
February1st to 15thNight
55%310%20%8%1
2690
16th to endNight
57%49%16%9%2
2373
March1st to 15thNight
51%47%19%14%2
2610
16th to endNight
49%5%11%22%10%1
2640
April1st to 15thNight
40%49%22%19%3
2300
16th to endNight
44%5%10%20%14%5%
2055
May1st to 15thNight
47%7%10%21%9%3
2025
16th to endNight
37%8%15%21%13%2
2116
June1st to 15thNight
29%6%16%27%16%3
1913
16th to endNight
31%7%17%23%15%4
1744
July1st to 15thNight
36%6%13%22%17%4
1704
16th to endNight
29%7%15%27%17%2
1883
August1st to 15thNight
28%8%15%26%18%3
1850
16th to endNight
29%6%14%26%19%3
2175
September1st to 15thNight
35%6%12%21%18%5%
2250
16th to endNight
34%37%25%25%2
2310
October1st to 15thNight
30%410%26%22%5%
2344
16th to endNight
40%36%25%21%3
2771
November1st to 15thNight
39%37%23%21%5%
2861
16th to endNight
45%37%24%16%1
2925
December1st to 15thNight
53%310%19%11%1
2925
16th to endNight
56%49%18%9%1
3120

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%16%34%15%6%
225
16th to endDay
24%20%37%16%2
240
February1st to 15thDay
31%22%32%9%4
225
16th to endDay
32%11%37%13%3
201
March1st to 15thDay
28%20%34%14%1
315
16th to endDay
25%14%31%20%7%1
480
April1st to 15thDay
18%16%26%24%11%2
450
16th to endDay
23%9%26%22%12%5%
439
May1st to 15thDay
22%8%29%19%14%5%
468
16th to endDay
15%322%25%17%13%
523
June1st to 15thDay
11%215%24%31%13%
443
16th to endDay
10%321%26%21%15%
573
July1st to 15thDay
16%211%22%24%22%
511
16th to endDay
11%19%24%28%24%
454
August1st to 15thDay
12%11%22%28%24%
418
16th to endDay
11%111%31%28%16%
460
September1st to 15thDay
14%19%23%29%21%
435
16th to endDay
17%211%21%29%15%
434
October1st to 15thDay
15%420%27%22%10%
435
16th to endDay
17%8%28%28%13%3
380
November1st to 15thDay
24%9%27%22%12%3
225
16th to endDay
26%7%32%24%8%
225
December1st to 15thDay
23%19%30%23%3
225
16th to endDay
27%15%37%14%5%
240
January1st to 15thNight
26%14%34%19%5%
900
16th to endNight
25%13%34%24%2
960
February1st to 15thNight
28%12%33%23%1
884
16th to endNight
26%13%39%18%2
791
March1st to 15thNight
23%12%34%23%5%
900
16th to endNight
21%10%31%25%10%
960
April1st to 15thNight
17%10%31%30%9%
727
16th to endNight
17%5%32%30%13%1
669
May1st to 15thNight
21%427%27%18%1
675
16th to endNight
12%216%36%27%4
707
June1st to 15thNight
8%15%42%28%4
637
16th to endNight
7%115%37%31%5%
630
July1st to 15thNight
11%211%32%33%9%
600
16th to endNight
9%16%33%41%8%
660
August1st to 15thNight
8%6%35%42%7%
620
16th to endNight
7%18%34%41%6%
669
September1st to 15thNight
14%111%26%38%7%
780
16th to endNight
13%214%30%33%5%
837
October1st to 15thNight
12%320%31%27%4
840
16th to endNight
20%6%28%29%14%1
896
November1st to 15thNight
17%7%27%28%17%2
880
16th to endNight
21%10%28%28%10%
900
December1st to 15thNight
26%11%28%25%7%
900
16th to endNight
28%11%30%25%4
960
Page generated at 2020-06-04 03:18:55. Version ac04

Copyright 2020 A. Danko


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