Brodhead
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Brodhead clear sky chart from 2005-11-05 to 2017-12-01.

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
42%
15720
20%
47844
14%
15676
49%
15676
24%
31399

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
15%
2327
7%
716
28%
716
14%
1696
January16th to endNight
19%
768
18%
2496
8%
768
31%
768
15%
1746
February1st to 15thNight
18%
704
15%
2133
5%
701
28%
701
16%
1542
February16th to endNight
14%
631
16%
1893
5%
631
24%
631
14%
1395
March1st to 15thNight
24%
720
17%
2084
9%
720
31%
720
18%
1470
March16th to endNight
31%
768
14%
2112
9%
768
35%
768
19%
1536
April1st to 15thNight
33%
590
22%
1848
12%
590
45%
590
27%
1157
April16th to endNight
36%
540
21%
1665
12%
540
45%
540
26%
1077
May1st to 15thNight
38%
539
15%
1619
9%
539
44%
539
20%
1136
May16th to endNight
57%
562
18%
1684
14%
561
60%
561
27%
1079
June1st to 15thNight
66%
540
17%
1620
15%
540
69%
540
33%
984
June16th to endNight
66%
540
17%
1620
15%
540
68%
540
33%
970
July1st to 15thNight
63%
510
13%
1530
12%
510
64%
510
28%
985
July16th to endNight
72%
564
19%
1595
16%
531
75%
531
34%
949
August1st to 15thNight
73%
539
21%
1609
20%
536
74%
536
33%
985
August16th to endNight
76%
573
22%
1871
24%
573
77%
573
32%
1076
September1st to 15thNight
63%
675
22%
1935
20%
675
64%
675
31%
1221
September16th to endNight
59%
717
28%
1980
22%
717
62%
717
35%
1207
October1st to 15thNight
57%
720
31%
2008
27%
720
62%
720
37%
1187
October16th to endNight
42%
768
27%
2361
21%
768
51%
768
28%
1449
November1st to 15thNight
43%
760
27%
2471
22%
760
53%
760
29%
1451
November16th to endNight
35%
780
24%
2535
17%
780
46%
780
24%
1594
December1st to 15thNight
28%
724
15%
2352
10%
724
34%
724
16%
1677
December16th to endNight
21%
768
17%
2496
8%
768
33%
768
14%
1830

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%35%45%7%36%
48578
Night
14%7%35%42445%7%40%
48042
TransparencyDay
45%6%10%20%14%2
48279
Night
43%5%10%21%16%3
47845
SeeingDay
17%7%22%22%19%10%
5551
Night
18%8%24%27%18%2
15722

By Month

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
19%13%5%9%5%2335%6%26%
1611
16th to endDay
18%12%5%6%424345%33%
1728
February1st to 15thDay
17%12%5%8%42335%5%30%
1729
16th to endDay
16%12%38%5%25%446%28%
1580
March1st to 15thDay
23%9%35%42434434%
1875
16th to endDay
18%9%45%5%35%446%32%
2111
April1st to 15thDay
14%7%35%425%447%39%
2109
16th to endDay
16%7%35%425%45%6%37%
2295
May1st to 15thDay
19%7%35%5%35%46%7%31%
2331
16th to endDay
11%6%36%5%35%5%49%37%
2431
June1st to 15thDay
9%425%7%46%5%5%9%37%
2340
16th to endDay
8%425%6%35%6%8%10%38%
2340
July1st to 15thDay
13%6%26%6%36%5%7%9%32%
2340
16th to endDay
10%5%25%7%5%6%7%6%9%32%
2465
August1st to 15thDay
10%5%26%6%36%6%7%8%34%
2340
16th to endDay
9%5%25%5%37%6%7%9%35%
2328
September1st to 15thDay
15%6%35%5%35%5%5%7%36%
2013
16th to endDay
14%42443445%7%44%
1980
October1st to 15thDay
11%424423446%51%
1950
16th to endDay
19%5%23313235%47%
1860
November1st to 15thDay
14%6%2442335%6%46%
1717
16th to endDay
16%8%35%314335%44%
1755
December1st to 15thDay
22%11%35%434335%32%
1622
16th to endDay
19%12%47%424346%30%
1728
January1st to 15thNight
19%10%5%8%7%33335%29%
2327
16th to endNight
18%10%5%7%424345%34%
2496
February1st to 15thNight
17%10%48%5%24345%32%
2124
16th to endNight
18%11%47%5%34335%31%
1893
March1st to 15thNight
16%9%45%5%34445%34%
2084
16th to endNight
15%9%46%5%35%445%33%
2112
April1st to 15thNight
13%7%24423447%44%
1848
16th to endNight
13%5%25%5%2445%7%40%
1665
May1st to 15thNight
16%5%35%6%46%5%45%35%
1619
16th to endNight
8%4245%46%5%6%8%41%
1682
June1st to 15thNight
5%315%5%25%6%8%10%43%
1620
16th to endNight
5%434435%47%14%41%
1620
July1st to 15thNight
9%425%5%35%5%6%10%40%
1620
16th to endNight
6%3145%36%5%8%11%43%
1703
August1st to 15thNight
5%4145%35%5%6%9%47%
1620
16th to endNight
6%314435%47%10%46%
1871
September1st to 15thNight
13%414425%5%6%7%44%
1935
16th to endNight
9%6%34424336%51%
1980
October1st to 15thNight
11%42342245%6%52%
2008
16th to endNight
16%5%24324336%46%
2361
November1st to 15thNight
13%6%24422346%49%
2471
16th to endNight
17%8%24323335%44%
2535
December1st to 15thNight
22%10%47%424345%31%
2352
16th to endNight
22%11%46%43433430%
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%48%15%11%1
1612
16th to endDay
53%38%24%9%1
1728
February1st to 15thDay
55%47%20%9%2
1731
16th to endDay
54%5%11%18%9%1
1580
March1st to 15thDay
53%39%17%14%1
1875
16th to endDay
51%6%10%21%9%
2112
April1st to 15thDay
42%5%9%24%15%3
2109
16th to endDay
46%5%9%21%13%3
2295
May1st to 15thDay
50%6%11%19%10%1
2331
16th to endDay
43%7%13%22%10%2
2435
June1st to 15thDay
41%7%12%22%13%1
2340
16th to endDay
38%8%12%18%19%2
2340
July1st to 15thDay
46%7%14%15%13%2
2201
16th to endDay
43%9%13%17%12%2
2310
August1st to 15thDay
43%9%12%19%12%1
2327
16th to endDay
40%9%12%20%15%2
2328
September1st to 15thDay
46%7%10%16%13%4
2013
16th to endDay
38%5%10%19%23%2
1980
October1st to 15thDay
33%5%8%24%23%4
1950
16th to endDay
39%36%25%22%2
1860
November1st to 15thDay
40%37%23%20%5%
1717
16th to endDay
42%37%24%19%2
1755
December1st to 15thDay
55%38%19%10%2
1622
16th to endDay
54%5%10%20%7%
1728
January1st to 15thNight
57%38%14%13%1
2327
16th to endNight
52%48%21%11%1
2496
February1st to 15thNight
54%39%19%10%1
2133
16th to endNight
56%49%18%9%1
1893
March1st to 15thNight
50%48%18%13%3
2084
16th to endNight
50%6%9%22%9%
2112
April1st to 15thNight
39%410%21%19%4
1848
16th to endNight
41%5%10%23%14%4
1665
May1st to 15thNight
49%6%11%20%10%2
1620
16th to endNight
37%9%14%22%13%2
1684
June1st to 15thNight
30%9%15%26%15%2
1620
16th to endNight
30%9%16%23%16%4
1620
July1st to 15thNight
37%8%14%20%15%3
1530
16th to endNight
30%8%18%23%15%3
1595
August1st to 15thNight
31%9%14%21%19%2
1609
16th to endNight
29%8%14%25%18%3
1871
September1st to 15thNight
35%7%14%19%16%6%
1935
16th to endNight
35%48%21%27%2
1980
October1st to 15thNight
31%5%9%23%24%5%
2008
16th to endNight
39%37%21%23%3
2361
November1st to 15thNight
36%36%23%23%6%
2471
16th to endNight
42%36%23%20%2
2535
December1st to 15thNight
55%39%18%10%3
2352
16th to endNight
57%38%17%10%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
28%23%36%5%41
90
16th to endDay
30%29%33%6%1
96
February1st to 15thDay
22%26%38%10%2
90
16th to endDay
30%14%37%14%2
81
March1st to 15thDay
30%19%36%11%1
165
16th to endDay
18%15%34%21%7%1
288
April1st to 15thDay
17%15%27%24%12%2
270
16th to endDay
18%10%29%21%14%5%
270
May1st to 15thDay
22%10%27%20%12%7%
288
16th to endDay
18%420%27%15%12%
331
June1st to 15thDay
12%315%25%28%15%
315
16th to endDay
11%421%25%23%13%
315
July1st to 15thDay
18%217%26%19%15%
305
16th to endDay
13%111%19%30%23%
326
August1st to 15thDay
13%9%24%31%19%
313
16th to endDay
11%110%28%28%19%
332
September1st to 15thDay
17%313%17%30%18%
315
16th to endDay
13%212%26%29%15%
314
October1st to 15thDay
13%420%28%20%12%
315
16th to endDay
19%6%26%23%19%4
276
November1st to 15thDay
24%10%25%24%11%2
135
16th to endDay
22%10%31%23%9%1
135
December1st to 15thDay
27%16%35%12%7%
90
16th to endDay
26%18%47%43
96
January1st to 15thNight
25%17%33%18%5%
720
16th to endNight
25%16%34%21%1
768
February1st to 15thNight
23%15%38%21%1
704
16th to endNight
26%15%39%16%2
631
March1st to 15thNight
23%13%33%23%5%
720
16th to endNight
21%10%29%26%10%
768
April1st to 15thNight
18%12%33%24%10%
590
16th to endNight
17%6%35%25%13%1
540
May1st to 15thNight
18%6%27%30%14%2
540
16th to endNight
10%220%32%28%6%
563
June1st to 15thNight
6%115%41%29%5%
540
16th to endNight
7%215%40%31%3
540
July1st to 15thNight
13%12%34%35%3
510
16th to endNight
8%110%28%43%8%
564
August1st to 15thNight
8%8%33%42%7%
539
16th to endNight
8%7%38%37%6%
573
September1st to 15thNight
13%113%26%37%6%
675
16th to endNight
13%116%27%34%5%
717
October1st to 15thNight
14%6%16%28%27%6%
720
16th to endNight
20%5%27%26%17%2
768
November1st to 15thNight
18%6%26%28%17%2
760
16th to endNight
22%12%26%26%10%
780
December1st to 15thNight
27%13%26%24%7%
724
16th to endNight
29%12%31%21%4
768
Page generated at 2017-12-02 09:14:22. Version ac04

Copyright 2017 A. Danko


Brodhead Clear Sky Chart |Charts Home