Berthoud
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Berthoud clear sky chart from 2005-11-05 to 2018-03-21.

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
58%
16772
27%
49230
19%
16732
66%
16732
42%
26737

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
47%
972
30%
2716
18%
970
58%
970
46%
1432
January16th to endNight
48%
893
33%
2765
22%
893
61%
893
44%
1416
February1st to 15thNight
40%
758
24%
2448
13%
757
55%
757
37%
1332
February16th to endNight
44%
684
29%
2050
16%
684
58%
684
38%
1136
March1st to 15thNight
55%
780
29%
2295
17%
780
65%
780
45%
1230
March16th to endNight
51%
702
26%
2088
17%
702
59%
702
40%
1162
April1st to 15thNight
49%
539
23%
1798
18%
539
59%
539
34%
976
April16th to endNight
44%
540
22%
1800
18%
540
52%
540
29%
1041
May1st to 15thNight
53%
540
19%
1579
16%
540
57%
540
28%
1021
May16th to endNight
62%
562
18%
1498
13%
561
65%
561
37%
909
June1st to 15thNight
71%
540
20%
1440
16%
540
73%
540
45%
811
June16th to endNight
79%
540
28%
1440
23%
540
81%
540
57%
731
July1st to 15thNight
76%
510
18%
1360
15%
510
77%
510
39%
798
July16th to endNight
82%
564
27%
1427
24%
531
82%
531
46%
790
August1st to 15thNight
79%
539
22%
1659
23%
536
79%
536
42%
873
August16th to endNight
81%
573
29%
1910
34%
573
81%
573
41%
975
September1st to 15thNight
74%
540
27%
1800
29%
540
77%
540
40%
928
September16th to endNight
76%
537
36%
1932
37%
537
81%
537
48%
870
October1st to 15thNight
63%
711
27%
2151
21%
711
67%
711
41%
1177
October16th to endNight
62%
808
35%
2344
22%
808
70%
808
46%
1231
November1st to 15thNight
60%
950
31%
2470
18%
950
66%
950
51%
1347
November16th to endNight
56%
975
34%
2618
20%
975
65%
975
53%
1352
December1st to 15thNight
47%
975
25%
2730
12%
975
58%
975
42%
1509
December16th to endNight
46%
1040
27%
2912
15%
1040
56%
1040
39%
1690

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
5%4134245%6%8%53%
49640
Night
5%42332335%7%58%
49403
Cloud CoverDay
6%41332445%8%53%
49638
Night
5%413323347%58%
49403
TransparencyDay
26%7%13%24%20%7%
49316
Night
24%5%12%26%22%7%
49230
SeeingDay
9%5%25%34%19%6%
6454
Night
7%324%43%18%2
16782

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
17%14413338%59%
1552
16th to endDay
15%2442335%6%61%
1823
February1st to 15thDay
26%35%323449%54%
1744
16th to endDay
25%2431345%7%58%
1710
March1st to 15thDay
3325%32346%7%56%
1993
16th to endDay
5%6%2432446%8%49%
2263
April1st to 15thDay
7%5%2332345%8%53%
2150
16th to endDay
12%7%1443445%7%43%
2160
May1st to 15thDay
12%5%135%36%5%6%8%41%
2370
16th to endDay
9%424435%5%7%9%42%
2616
June1st to 15thDay
5%212425%6%8%10%49%
2520
16th to endDay
312325%6%7%9%57%
2520
July1st to 15thDay
6%314435%7%6%10%46%
2520
16th to endDay
32135%35%7%8%10%48%
2643
August1st to 15thDay
5%3145%36%7%8%10%44%
2292
16th to endDay
42133246%7%9%52%
2292
September1st to 15thDay
8%3133245%5%7%56%
2160
16th to endDay
5%413223335%63%
2028
October1st to 15thDay
6%5%1322345%6%58%
1806
16th to endDay
5%42212346%66%
1866
November1st to 15thDay
242331345%8%59%
1718
16th to endDay
232331335%9%60%
1670
December1st to 15thDay
26%14323449%55%
1560
16th to endDay
45%2442345%7%55%
1664
January1st to 15thNight
1434313336%63%
2716
16th to endNight
35%24323346%62%
2765
February1st to 15thNight
27%36%31335%7%55%
2438
16th to endNight
28%34413345%56%
2050
March1st to 15thNight
342332335%8%59%
2295
16th to endNight
6%6%24323347%56%
2088
April1st to 15thNight
7%42342435%8%53%
1798
16th to endNight
14%6%24422247%49%
1800
May1st to 15thNight
14%41442445%7%45%
1578
16th to endNight
10%313423448%53%
1497
June1st to 15thNight
6%1342245%9%58%
1440
16th to endNight
12221346%8%65%
1440
July1st to 15thNight
6%212325%5%6%10%52%
1440
16th to endNight
31134245%8%8%56%
1523
August1st to 15thNight
32133145%7%10%55%
1668
16th to endNight
42133245%5%7%58%
1910
September1st to 15thNight
8%2133245%5%7%57%
1800
16th to endNight
6%22222346%66%
1932
October1st to 15thNight
8%423312346%59%
2151
16th to endNight
6%5%12213235%63%
2344
November1st to 15thNight
331332335%6%63%
2470
16th to endNight
2412222347%64%
2618
December1st to 15thNight
36%25%322348%57%
2730
16th to endNight
37%3442445%8%53%
2912

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
16%24323248%58%
1552
16th to endDay
2424422447%61%
1823
February1st to 15thDay
26%3432445%8%54%
1744
16th to endDay
26%2331245%7%58%
1710
March1st to 15thDay
341442445%8%57%
1993
16th to endDay
6%6%2431445%9%49%
2261
April1st to 15thDay
8%5%2332345%8%53%
2150
16th to endDay
13%6%1443446%7%43%
2160
May1st to 15thDay
13%5%14426%5%5%8%41%
2370
16th to endDay
10%4145%35%6%6%8%41%
2616
June1st to 15thDay
6%212326%6%6%10%49%
2520
16th to endDay
2112325%6%7%8%57%
2520
July1st to 15thDay
7%313435%6%6%9%47%
2520
16th to endDay
4213436%6%7%9%49%
2643
August1st to 15thDay
6%314435%6%8%10%44%
2292
16th to endDay
5%213425%5%7%8%53%
2292
September1st to 15thDay
9%21332445%6%57%
2160
16th to endDay
6%313212336%63%
2028
October1st to 15thDay
7%412323348%58%
1806
16th to endDay
5%41212347%66%
1866
November1st to 15thDay
25%1231346%7%59%
1718
16th to endDay
232321335%9%61%
1670
December1st to 15thDay
26%2432345%7%56%
1560
16th to endDay
45%25%423447%56%
1664
January1st to 15thNight
1424313347%62%
2716
16th to endNight
35%24323346%62%
2765
February1st to 15thNight
27%26%323347%55%
2438
16th to endNight
28%34423236%57%
2050
March1st to 15thNight
342332435%7%60%
2295
16th to endNight
6%6%24323347%56%
2088
April1st to 15thNight
7%42432445%7%53%
1798
16th to endNight
15%6%13323236%50%
1800
May1st to 15thNight
15%41342345%7%46%
1578
16th to endNight
11%313323447%53%
1497
June1st to 15thNight
6%21232435%9%58%
1440
16th to endNight
21221345%7%66%
1440
July1st to 15thNight
7%2123245%8%9%53%
1440
16th to endNight
32123345%6%8%56%
1523
August1st to 15thNight
33133235%7%10%54%
1668
16th to endNight
5%213425%45%6%60%
1910
September1st to 15thNight
9%212224447%58%
1800
16th to endNight
5%212222445%66%
1932
October1st to 15thNight
9%313222346%59%
2151
16th to endNight
6%5%13212235%63%
2344
November1st to 15thNight
4313313346%63%
2470
16th to endNight
241321235%6%65%
2618
December1st to 15thNight
36%25%322348%57%
2730
16th to endNight
37%2442445%7%53%
2912

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%413%32%20%4
1553
16th to endDay
22%411%32%21%6%
1823
February1st to 15thDay
26%5%17%33%12%3
1745
16th to endDay
23%5%10%30%25%5%
1710
March1st to 15thDay
25%5%11%27%23%6%
1993
16th to endDay
30%5%14%25%18%4
2263
April1st to 15thDay
28%6%13%25%18%7%
2150
16th to endDay
38%7%12%21%16%3
2160
May1st to 15thDay
38%9%13%22%12%2
2370
16th to endDay
35%10%15%21%11%4
2620
June1st to 15thDay
25%10%15%20%19%8%
2520
16th to endDay
19%7%13%21%26%11%
2520
July1st to 15thDay
30%9%12%19%15%13%
2371
16th to endDay
26%10%14%23%16%8%
2477
August1st to 15thDay
30%10%15%17%15%10%
2277
16th to endDay
23%8%13%22%23%8%
2292
September1st to 15thDay
25%6%11%21%21%14%
2160
16th to endDay
22%48%22%34%7%
2028
October1st to 15thDay
26%5%12%20%26%8%
1806
16th to endDay
19%410%27%27%10%
1866
November1st to 15thDay
21%5%12%24%26%10%
1718
16th to endDay
20%311%26%30%7%
1670
December1st to 15thDay
25%5%14%32%18%3
1560
16th to endDay
27%5%16%27%19%4
1664
January1st to 15thNight
22%413%31%24%4
2716
16th to endNight
24%311%28%25%7%
2765
February1st to 15thNight
28%5%14%30%17%3
2448
16th to endNight
28%49%26%23%7%
2050
March1st to 15thNight
23%5%9%26%28%6%
2295
16th to endNight
28%314%25%22%4
2088
April1st to 15thNight
27%6%12%27%18%7%
1798
16th to endNight
35%411%25%18%4
1800
May1st to 15thNight
36%9%14%20%16%3
1579
16th to endNight
29%8%20%23%11%6%
1498
June1st to 15thNight
21%8%18%25%13%11%
1440
16th to endNight
15%6%11%25%28%13%
1440
July1st to 15thNight
26%8%15%21%17%9%
1360
16th to endNight
22%7%14%29%17%9%
1427
August1st to 15thNight
21%8%17%24%18%9%
1659
16th to endNight
23%6%10%25%24%9%
1910
September1st to 15thNight
24%6%13%22%16%16%
1800
16th to endNight
19%39%27%30%9%
1932
October1st to 15thNight
25%6%13%18%26%10%
2151
16th to endNight
23%49%25%27%10%
2344
November1st to 15thNight
20%411%24%26%11%
2470
16th to endNight
18%411%27%28%8%
2618
December1st to 15thNight
25%414%28%19%6%
2730
16th to endNight
29%5%14%29%18%2
2912

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
11%5%14%48%11%8%
135
16th to endDay
4131%40%19%2
144
February1st to 15thDay
413%36%40%5%
135
16th to endDay
45%38%44%5%1
120
March1st to 15thDay
5%12%29%39%10%2
178
16th to endDay
12%15%40%23%5%1
311
April1st to 15thDay
12%16%39%20%8%1
269
16th to endDay
22%16%28%24%5%1
270
May1st to 15thDay
15%7%25%31%13%4
435
16th to endDay
17%423%26%21%6%
517
June1st to 15thDay
6%221%33%27%8%
495
16th to endDay
2124%35%26%9%
495
July1st to 15thDay
11%115%31%28%12%
475
16th to endDay
5%114%30%36%11%
502
August1st to 15thDay
7%227%38%17%6%
315
16th to endDay
7%318%40%24%6%
332
September1st to 15thDay
6%426%35%19%7%
315
16th to endDay
9%224%30%27%6%
183
October1st to 15thDay
8%421%41%14%9%
135
16th to endDay
6%5%27%38%15%6%
144
November1st to 15thDay
4419%40%17%14%
135
16th to endDay
9%5%26%47%11%
135
December1st to 15thDay
8%6%32%42%8%
135
16th to endDay
2128%56%9%
144
January1st to 15thNight
36%34%39%11%2
975
16th to endNight
5%5%35%42%10%1
893
February1st to 15thNight
5%241%41%7%
764
16th to endNight
5%5%35%45%7%
684
March1st to 15thNight
4233%47%11%1
780
16th to endNight
7%5%29%47%9%
702
April1st to 15thNight
8%5%30%46%7%
539
16th to endNight
17%428%34%13%1
540
May1st to 15thNight
16%320%40%16%2
540
16th to endNight
11%116%39%27%3
563
June1st to 15thNight
6%114%51%22%2
540
16th to endNight
212%50%31%2
540
July1st to 15thNight
8%8%36%40%6%
510
16th to endNight
45%34%50%5%
564
August1st to 15thNight
47%37%45%3
539
16th to endNight
5%16%38%41%7%
573
September1st to 15thNight
9%18%41%31%8%
540
16th to endNight
6%13%45%28%5%
537
October1st to 15thNight
11%118%45%18%4
711
16th to endNight
10%220%44%18%3
808
November1st to 15thNight
5%425%48%14%2
950
16th to endNight
5%429%47%12%
975
December1st to 15thNight
5%435%44%9%
975
16th to endNight
7%335%43%8%1
1040
Page generated at 2018-03-22 09:34:21. Version ac04

Copyright 2018 A. Danko


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