EAFB
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the EAFB clear sky chart from 2005-11-05 to 2018-04-23.

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
67%
16593
38%
49411
29%
16551
76%
16551
63%
21542

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
65%
776
30%
2716
29%
776
73%
776
46%
1252
January16th to endNight
64%
832
39%
2567
33%
832
74%
832
52%
1205
February1st to 15thNight
62%
757
37%
2285
30%
757
74%
757
55%
1075
February16th to endNight
56%
684
35%
2051
30%
684
68%
684
49%
1013
March1st to 15thNight
60%
780
31%
2340
27%
780
69%
780
52%
1121
March16th to endNight
54%
832
35%
2180
20%
832
68%
832
61%
1074
April1st to 15thNight
47%
779
36%
1949
14%
779
60%
779
61%
989
April16th to endNight
52%
744
39%
1860
15%
744
64%
744
71%
862
May1st to 15thNight
55%
588
38%
1667
22%
587
63%
587
75%
674
May16th to endNight
50%
561
37%
1685
21%
561
62%
561
72%
651
June1st to 15thNight
61%
439
38%
1519
29%
439
73%
439
81%
495
June16th to endNight
74%
360
42%
1440
42%
360
85%
360
86%
398
July1st to 15thNight
88%
340
37%
1360
41%
340
92%
340
69%
449
July16th to endNight
85%
564
38%
1589
31%
527
86%
527
69%
668
August1st to 15thNight
82%
717
39%
1790
23%
713
84%
713
85%
774
August16th to endNight
87%
764
46%
1910
29%
764
89%
764
83%
846
September1st to 15thNight
82%
720
44%
1833
29%
720
87%
720
81%
805
September16th to endNight
80%
716
50%
1980
40%
716
89%
716
85%
785
October1st to 15thNight
68%
720
41%
1992
31%
720
80%
720
69%
885
October16th to endNight
73%
768
47%
2353
42%
768
84%
768
70%
948
November1st to 15thNight
74%
760
37%
2470
36%
760
82%
760
64%
1002
November16th to endNight
74%
780
41%
2535
41%
780
81%
780
60%
1066
December1st to 15thNight
66%
780
35%
2535
31%
780
76%
780
50%
1165
December16th to endNight
60%
832
34%
2805
30%
832
70%
832
44%
1340

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
211212236%75%
50085
Night
211212235%75%
49607
TransparencyDay
12%25%16%27%35%
49774
Night
12%25%18%30%30%
49419
SeeingDay
39%24%28%21%12%
6616
Night
2323%40%26%2
16606

By Month

Percentage Cloud Cover SW (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
5%213334338%59%
1552
16th to endDay
6%323214337%60%
2002
February1st to 15thDay
211331335%8%66%
1901
16th to endDay
411332325%7%62%
1709
March1st to 15thDay
211122236%10%65%
1950
16th to endDay
11121125%5%8%66%
2392
April1st to 15thDay
2112212336%71%
2329
16th to endDay
1111237%79%
2214
May1st to 15thDay
11225%83%
2281
16th to endDay
11111225%81%
2429
June1st to 15thDay
11122483%
2436
16th to endDay
111289%
2520
July1st to 15thDay
1121222480%
2520
16th to endDay
212112225%76%
2462
August1st to 15thDay
11112385%
2160
16th to endDay
1122484%
2292
September1st to 15thDay
11213384%
2127
16th to endDay
1111387%
1980
October1st to 15thDay
121111123478%
1966
16th to endDay
11211235%78%
1869
November1st to 15thDay
111112245%73%
1719
16th to endDay
212323349%67%
1755
December1st to 15thDay
221332335%9%62%
1755
16th to endDay
5%31332345%7%58%
1765
January1st to 15thNight
4213313347%63%
2716
16th to endNight
4213212247%66%
2567
February1st to 15thNight
2213213246%68%
2281
16th to endNight
5%212323346%65%
2051
March1st to 15thNight
211222335%8%66%
2340
16th to endNight
1112212248%70%
2180
April1st to 15thNight
2112213236%72%
1949
16th to endNight
1112235%80%
1860
May1st to 15thNight
11235%82%
1667
16th to endNight
112135%83%
1684
June1st to 15thNight
122486%
1519
16th to endNight
1292%
1440
July1st to 15thNight
1111222481%
1440
16th to endNight
2111233478%
1700
August1st to 15thNight
1112388%
1800
16th to endNight
1112386%
1910
September1st to 15thNight
12111385%
1833
16th to endNight
1112388%
1980
October1st to 15thNight
121323479%
1992
16th to endNight
12123480%
2353
November1st to 15thNight
111112236%76%
2470
16th to endNight
31212347%71%
2535
December1st to 15thNight
322223337%68%
2535
16th to endNight
421231345%7%63%
2805

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
23%48%25%25%12%
1552
16th to endDay
24%27%23%25%15%
2002
February1st to 15thDay
17%26%22%30%20%
1901
16th to endDay
20%27%24%30%13%
1709
March1st to 15thDay
14%29%26%26%19%
1950
16th to endDay
14%310%25%29%16%
2392
April1st to 15thDay
15%26%22%30%21%
2329
16th to endDay
7%16%23%32%26%
2214
May1st to 15thDay
7%1420%32%33%
2281
16th to endDay
9%1417%39%27%
2432
June1st to 15thDay
6%312%25%51%
2436
16th to endDay
42415%72%
2520
July1st to 15thDay
9%115%17%63%
2371
16th to endDay
12%1311%22%48%
2311
August1st to 15thDay
6%17%21%63%
2146
16th to endDay
7%11425%58%
2292
September1st to 15thDay
7%138%24%55%
2127
16th to endDay
5%17%34%51%
1980
October1st to 15thDay
11%2213%31%38%
1966
16th to endDay
10%2414%27%41%
1869
November1st to 15thDay
13%25%18%38%20%
1719
16th to endDay
16%36%20%30%23%
1755
December1st to 15thDay
20%48%22%26%17%
1755
16th to endDay
25%49%23%23%12%
1765
January1st to 15thNight
21%36%23%29%16%
2716
16th to endNight
18%37%23%26%20%
2567
February1st to 15thNight
17%28%19%29%23%
2292
16th to endNight
21%27%23%30%15%
2051
March1st to 15thNight
17%49%24%24%19%
2340
16th to endNight
13%310%28%28%15%
2180
April1st to 15thNight
14%27%30%28%15%
1949
16th to endNight
8%27%27%35%17%
1860
May1st to 15thNight
5%26%24%38%23%
1668
16th to endNight
6%17%21%43%19%
1685
June1st to 15thNight
45%17%31%41%
1519
16th to endNight
326%25%62%
1440
July1st to 15thNight
8%118%19%60%
1360
16th to endNight
11%1412%26%42%
1589
August1st to 15thNight
4118%26%56%
1790
16th to endNight
5%17%32%51%
1910
September1st to 15thNight
6%128%32%48%
1833
16th to endNight
419%39%45%
1980
October1st to 15thNight
10%1214%33%36%
1992
16th to endNight
8%2313%27%43%
2353
November1st to 15thNight
12%25%19%35%26%
2470
16th to endNight
13%26%20%28%27%
2535
December1st to 15thNight
18%38%20%28%20%
2535
16th to endNight
21%410%23%25%14%
2805

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
13%7%18%24%30%5%
90
16th to endDay
8%10%19%21%25%14%
330
February1st to 15thDay
411%23%21%20%18%
326
16th to endDay
6%20%22%22%16%11%
290
March1st to 15thDay
6%13%26%26%16%9%
330
16th to endDay
5%17%28%23%20%5%
352
April1st to 15thDay
6%17%33%20%14%7%
329
16th to endDay
5%17%36%20%12%7%
288
May1st to 15thDay
312%35%26%14%8%
288
16th to endDay
313%31%26%14%10%
330
June1st to 15thDay
19%34%28%15%9%
315
16th to endDay
334%28%19%12%
315
July1st to 15thDay
1121%39%23%12%
305
16th to endDay
2114%46%20%14%
327
August1st to 15thDay
126%37%18%15%
315
16th to endDay
1115%42%22%16%
332
September1st to 15thDay
323%32%25%14%
315
16th to endDay
16%16%31%29%14%
315
October1st to 15thDay
19%24%27%28%7%
315
16th to endDay
27%20%22%28%20%
285
November1st to 15thDay
4320%22%27%20%
135
16th to endDay
210%14%32%30%10%
135
December1st to 15thDay
16%15%28%38%8%
135
16th to endDay
5%10%15%26%31%10%
119
January1st to 15thNight
5%320%40%27%2
780
16th to endNight
5%321%41%26%1
832
February1st to 15thNight
3324%38%27%2
764
16th to endNight
7%5%28%37%19%2
684
March1st to 15thNight
26%26%42%20%1
780
16th to endNight
26%34%35%19%1
832
April1st to 15thNight
28%39%30%17%1
779
16th to endNight
18%36%33%18%2
744
May1st to 15thNight
6%37%40%15%
588
16th to endNight
17%38%38%14%
563
June1st to 15thNight
5%32%51%10%
439
16th to endNight
23%57%17%
360
July1st to 15thNight
17%59%30%
340
16th to endNight
19%55%31%1
564
August1st to 15thNight
114%49%32%2
717
16th to endNight
19%41%42%4
764
September1st to 15thNight
111%40%39%6%
720
16th to endNight
16%37%39%5%
716
October1st to 15thNight
1225%38%30%2
720
16th to endNight
1119%32%36%7%
768
November1st to 15thNight
1120%41%31%4
760
16th to endNight
3216%39%33%4
780
December1st to 15thNight
4321%42%25%2
780
16th to endNight
5%425%39%22%2
832
Page generated at 2018-04-24 07:02:59. Version ac04

Copyright 2018 A. Danko


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