This page made possible by the sponsorship of: Chippewa Valley Astronomical Society.

Hobbs Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hobbs Observatory clear sky chart from 2005-11-05 to 2019-05-11.

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
33%
18443
16%
53667
9%
18396
38%
18396
24%
36056

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
26%
1050
13%
2926
6%
1045
32%
1045
19%
2146
January16th to endNight
21%
1120
12%
3047
4%
1120
25%
1120
17%
2309
February1st to 15thNight
23%
1030
14%
2678
4%
1026
29%
1026
20%
1955
February16th to endNight
26%
807
14%
2277
6%
807
32%
807
19%
1616
March1st to 15thNight
31%
760
18%
2440
11%
760
37%
760
21%
1596
March16th to endNight
32%
672
17%
2388
14%
672
38%
672
20%
1554
April1st to 15thNight
25%
629
15%
2097
10%
629
34%
629
19%
1408
April16th to endNight
27%
624
16%
2011
9%
624
34%
624
20%
1359
May1st to 15thNight
26%
617
15%
1646
7%
617
31%
617
22%
1190
May16th to endNight
39%
611
14%
1625
5%
609
43%
609
31%
1061
June1st to 15thNight
38%
585
12%
1560
4%
585
41%
585
31%
1019
June16th to endNight
44%
585
14%
1560
5%
585
47%
585
37%
951
July1st to 15thNight
54%
555
18%
1480
8%
555
57%
555
46%
825
July16th to endNight
64%
612
19%
1545
10%
579
65%
579
47%
857
August1st to 15thNight
62%
575
22%
1650
19%
572
64%
572
37%
970
August16th to endNight
50%
621
20%
2006
18%
621
55%
621
32%
1152
September1st to 15thNight
54%
585
25%
1950
23%
585
60%
585
36%
1049
September16th to endNight
45%
686
22%
2115
16%
686
51%
686
32%
1232
October1st to 15thNight
35%
780
22%
2340
14%
780
40%
780
28%
1461
October16th to endNight
32%
832
17%
2577
9%
832
39%
832
22%
1712
November1st to 15thNight
28%
887
18%
2733
10%
887
36%
887
23%
1796
November16th to endNight
23%
1050
14%
2940
7%
1050
29%
1050
19%
2108
December1st to 15thNight
20%
1050
11%
2940
4%
1050
25%
1050
15%
2225
December16th to endNight
19%
1120
11%
3136
4%
1120
24%
1120
12%
2505

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%8%36%5%3445%6%35%
54202
Night
14%8%36%5%24446%38%
53836
Cloud CoverDay
25%7%25%5%23346%31%
54212
Night
24%7%25%423345%34%
53840
Cloud CoverDay
15%8%36%5%3445%7%35%
54210
Night
14%8%36%5%24446%38%
53840
TransparencyDay
48%413%23%10%
53887
Night
46%312%24%11%1
53668
SeeingDay
18%7%27%26%14%4
8260
Night
18%7%29%31%11%1
18443

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
11%10%6%9%6%36%35%6%28%
1672
16th to endDay
12%15%5%11%7%35%5%5%7%21%
1879
February1st to 15thDay
10%10%6%8%5%35%45%6%32%
1845
16th to endDay
14%10%5%9%6%345%5%6%28%
1767
March1st to 15thDay
15%10%46%5%35%445%34%
2180
16th to endDay
17%9%36%5%3445%6%34%
2540
April1st to 15thDay
18%10%46%6%2435%5%31%
2511
16th to endDay
23%9%26%5%24345%31%
2553
May1st to 15thDay
19%6%36%6%35%446%33%
2862
16th to endDay
14%6%25%6%3446%6%39%
2841
June1st to 15thDay
18%5%25%42446%7%39%
2730
16th to endDay
10%5%26%5%36%6%6%9%36%
2730
July1st to 15thDay
8%324436%5%6%9%45%
2730
16th to endDay
9%3245%35%6%6%8%45%
2879
August1st to 15thDay
10%425%6%35%5%7%8%39%
2553
16th to endDay
14%5%2443446%8%42%
2548
September1st to 15thDay
12%424423347%48%
2340
16th to endDay
18%5%24434347%40%
2161
October1st to 15thDay
19%8%35%424345%39%
1950
16th to endDay
20%11%26%422235%38%
1997
November1st to 15thDay
15%10%46%5%23336%37%
1782
16th to endDay
15%10%45%6%2436%6%32%
1680
December1st to 15thDay
14%12%6%10%9%45%435%22%
1680
16th to endDay
20%16%6%11%8%4433319%
1792
January1st to 15thNight
12%10%5%9%7%35%345%32%
2926
16th to endNight
12%12%5%9%7%345%5%6%26%
3047
February1st to 15thNight
9%11%5%9%6%25%446%33%
2675
16th to endNight
12%11%47%6%34446%33%
2277
March1st to 15thNight
13%7%46%5%24446%40%
2428
16th to endNight
16%7%35%5%34345%38%
2388
April1st to 15thNight
21%9%2442345%5%35%
2097
16th to endNight
21%8%25%433346%35%
2011
May1st to 15thNight
24%6%25%5%24446%33%
1646
16th to endNight
12%5%36%42445%6%43%
1624
June1st to 15thNight
13%5%244345%5%8%41%
1560
16th to endNight
9%324325%5%6%9%46%
1560
July1st to 15thNight
6%21332345%9%56%
1560
16th to endNight
6%12325%5%5%9%55%
1641
August1st to 15thNight
8%3244245%5%7%49%
1659
16th to endNight
13%5%24314345%51%
2006
September1st to 15thNight
9%41442345%6%54%
1950
16th to endNight
14%423423446%49%
2115
October1st to 15thNight
18%6%24322246%45%
2340
16th to endNight
18%8%25%423345%39%
2577
November1st to 15thNight
16%9%36%31335%6%39%
2733
16th to endNight
16%10%47%5%34446%33%
2940
December1st to 15thNight
15%12%6%9%7%24346%27%
2940
16th to endNight
18%14%5%11%7%3443423%
3136

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
22%8%5%8%6%35%346%26%
1672
16th to endDay
24%14%310%6%3345%5%17%
1879
February1st to 15thDay
23%10%48%423345%29%
1845
16th to endDay
24%9%48%6%33445%24%
1767
March1st to 15thDay
26%8%35%43433432%
2190
16th to endDay
27%8%25%5%24346%29%
2540
April1st to 15thDay
30%9%25%5%2334427%
2511
16th to endDay
34%9%25%42333426%
2553
May1st to 15thDay
30%5%25%6%24345%28%
2862
16th to endDay
27%5%14423445%33%
2841
June1st to 15thDay
30%5%1432345%6%31%
2730
16th to endDay
25%5%25%5%345%47%30%
2730
July1st to 15thDay
23%31433445%8%37%
2730
16th to endDay
23%2134335%5%7%38%
2879
August1st to 15thDay
17%4245%345%6%8%36%
2553
16th to endDay
19%5%1342345%7%40%
2548
September1st to 15thDay
18%5%14423346%44%
2340
16th to endDay
22%5%24434346%38%
2161
October1st to 15thDay
25%7%25%32433436%
1950
16th to endDay
26%9%25%42223436%
1997
November1st to 15thDay
25%9%25%422235%33%
1782
16th to endDay
26%8%45%5%2425%429%
1680
December1st to 15thDay
26%12%48%7%35%33419%
1680
16th to endDay
30%13%5%9%7%3332317%
1792
January1st to 15thNight
22%8%48%6%3434429%
2926
16th to endNight
24%11%48%6%335%5%5%22%
3047
February1st to 15thNight
21%10%5%8%6%23335%29%
2668
16th to endNight
22%10%36%6%34435%30%
2277
March1st to 15thNight
23%6%25%5%24335%37%
2440
16th to endNight
27%6%25%423245%34%
2388
April1st to 15thNight
31%8%2442334431%
2097
16th to endNight
33%8%24323235%29%
2011
May1st to 15thNight
35%5%24423336%27%
1645
16th to endNight
26%5%2431325%6%36%
1624
June1st to 15thNight
26%3144335%5%6%34%
1560
16th to endNight
23%32341445%7%40%
1560
July1st to 15thNight
21%213312347%48%
1560
16th to endNight
20%12223447%48%
1641
August1st to 15thNight
15%31442445%7%46%
1659
16th to endNight
18%414313245%49%
2006
September1st to 15thNight
15%41432335%5%50%
1950
16th to endNight
18%414322336%48%
2115
October1st to 15thNight
24%6%24322235%42%
2340
16th to endNight
24%7%25%42334437%
2577
November1st to 15thNight
25%8%35%312335%36%
2733
16th to endNight
26%9%37%433335%29%
2940
December1st to 15thNight
27%11%48%6%22235%23%
2940
16th to endNight
28%12%410%6%2333320%
3136

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
12%11%5%9%7%36%45%6%27%
1672
16th to endDay
12%15%5%11%7%35%5%5%7%21%
1879
February1st to 15thDay
11%10%6%8%6%35%45%6%32%
1845
16th to endDay
14%10%49%6%35%5%5%7%27%
1767
March1st to 15thDay
15%10%46%5%35%446%34%
2190
16th to endDay
17%9%36%5%3435%7%33%
2538
April1st to 15thDay
18%10%37%6%34345%31%
2511
16th to endDay
23%9%35%5%24445%31%
2553
May1st to 15thDay
19%6%36%6%35%45%6%33%
2862
16th to endDay
14%5%25%6%345%6%6%39%
2841
June1st to 15thDay
18%5%2442445%8%38%
2730
16th to endDay
10%5%26%6%35%6%6%10%36%
2730
July1st to 15thDay
8%3145%36%5%7%9%44%
2730
16th to endDay
8%3245%35%5%6%9%45%
2879
August1st to 15thDay
9%5%25%6%35%5%7%8%39%
2553
16th to endDay
14%6%1442445%8%41%
2548
September1st to 15thDay
12%5%245%2345%7%47%
2340
16th to endDay
17%434434347%40%
2161
October1st to 15thDay
19%8%35%323345%39%
1950
16th to endDay
20%10%35%433235%37%
1997
November1st to 15thDay
15%10%46%433336%37%
1782
16th to endDay
16%11%46%6%35%36%6%32%
1680
December1st to 15thDay
14%13%6%10%9%45%43421%
1680
16th to endDay
19%16%7%11%8%3433219%
1792
January1st to 15thNight
12%10%5%9%7%35%345%32%
2926
16th to endNight
12%12%6%9%7%345%5%6%26%
3047
February1st to 15thNight
9%11%6%9%7%35%345%33%
2668
16th to endNight
12%11%47%6%3445%6%33%
2277
March1st to 15thNight
13%7%36%5%34445%40%
2440
16th to endNight
16%7%35%5%34345%38%
2388
April1st to 15thNight
21%9%245%2445%5%35%
2097
16th to endNight
21%8%25%423346%35%
2011
May1st to 15thNight
23%6%26%424445%34%
1645
16th to endNight
13%5%36%42445%7%43%
1624
June1st to 15thNight
13%5%244345%5%8%42%
1560
16th to endNight
9%323325%5%7%8%46%
1560
July1st to 15thNight
6%31422345%9%57%
1560
16th to endNight
6%233345%5%9%55%
1641
August1st to 15thNight
8%4144245%5%8%49%
1659
16th to endNight
13%424324345%51%
2006
September1st to 15thNight
9%42442335%6%53%
1950
16th to endNight
14%424423446%49%
2115
October1st to 15thNight
18%6%24323246%44%
2340
16th to endNight
18%9%25%423345%39%
2577
November1st to 15thNight
16%9%45%413347%38%
2733
16th to endNight
16%10%47%5%33445%33%
2940
December1st to 15thNight
15%13%5%9%7%23335%27%
2940
16th to endNight
18%14%5%10%6%3443422%
3136

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
56%411%19%7%
1673
16th to endDay
61%312%15%5%
1879
February1st to 15thDay
51%315%19%8%
1846
16th to endDay
55%49%22%6%
1767
March1st to 15thDay
51%313%20%9%
2190
16th to endDay
50%313%24%7%
2540
April1st to 15thDay
54%39%19%11%1
2511
16th to endDay
55%211%19%10%1
2553
May1st to 15thDay
51%413%21%8%
2862
16th to endDay
43%5%11%24%12%2
2845
June1st to 15thDay
43%313%28%10%
2730
16th to endDay
41%5%15%26%10%
2730
July1st to 15thDay
34%414%29%14%2
2581
16th to endDay
33%5%16%27%15%1
2712
August1st to 15thDay
38%5%13%28%11%1
2538
16th to endDay
39%413%28%12%
2548
September1st to 15thDay
35%313%32%14%
2340
16th to endDay
44%313%30%7%
2161
October1st to 15thDay
47%211%26%11%
1950
16th to endDay
50%212%24%7%
1997
November1st to 15thDay
48%411%22%11%
1782
16th to endDay
52%318%17%6%
1680
December1st to 15thDay
65%211%16%4
1680
16th to endDay
70%28%11%5%
1792
January1st to 15thNight
54%312%20%7%
2926
16th to endNight
57%412%18%6%
3047
February1st to 15thNight
52%311%23%8%
2678
16th to endNight
51%311%24%7%
2277
March1st to 15thNight
45%412%26%10%1
2440
16th to endNight
47%311%24%11%1
2388
April1st to 15thNight
49%38%20%15%1
2097
16th to endNight
49%28%21%15%2
2011
May1st to 15thNight
50%411%21%10%1
1646
16th to endNight
40%311%24%17%1
1626
June1st to 15thNight
38%5%13%28%13%
1560
16th to endNight
32%5%14%30%14%2
1560
July1st to 15thNight
24%412%35%20%2
1480
16th to endNight
24%418%29%20%3
1545
August1st to 15thNight
31%413%28%18%2
1650
16th to endNight
34%314%28%15%2
2006
September1st to 15thNight
30%312%32%20%
1950
16th to endNight
35%213%34%13%
2115
October1st to 15thNight
41%210%30%14%1
2340
16th to endNight
47%212%22%13%
2577
November1st to 15thNight
46%314%22%12%
2733
16th to endNight
52%315%19%7%
2940
December1st to 15thNight
59%312%19%4
2940
16th to endNight
64%310%14%5%
3136

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
17%10%35%25%9%1
180
16th to endDay
22%8%35%27%5%
192
February1st to 15thDay
18%13%45%17%5%
180
16th to endDay
22%15%34%23%4
159
March1st to 15thDay
19%13%40%17%7%1
180
16th to endDay
21%8%29%21%13%5%
268
April1st to 15thDay
29%8%27%25%7%1
390
16th to endDay
29%10%22%22%11%2
435
May1st to 15thDay
24%10%30%24%9%1
594
16th to endDay
17%8%24%27%16%5%
597
June1st to 15thDay
17%5%27%31%14%3
570
16th to endDay
13%7%31%25%15%6%
570
July1st to 15thDay
10%421%29%23%11%
550
16th to endDay
8%421%32%22%10%
595
August1st to 15thDay
10%422%29%27%6%
549
16th to endDay
19%416%28%23%8%
460
September1st to 15thDay
13%5%19%32%22%7%
375
16th to endDay
19%428%31%14%1
312
October1st to 15thDay
28%10%31%19%6%3
180
16th to endDay
25%14%30%23%6%
192
November1st to 15thDay
15%8%32%32%8%1
180
16th to endDay
25%12%42%15%4
180
December1st to 15thDay
19%11%35%25%8%
180
16th to endDay
30%14%36%15%3
192
January1st to 15thNight
17%8%33%29%9%1
1050
16th to endNight
19%7%35%30%5%
1120
February1st to 15thNight
15%10%34%30%8%
1030
16th to endNight
17%11%33%28%7%
807
March1st to 15thNight
16%9%32%31%8%1
760
16th to endNight
19%5%30%29%12%1
672
April1st to 15thNight
26%7%31%27%6%
629
16th to endNight
25%5%29%27%9%
624
May1st to 15thNight
26%5%31%29%5%1
617
16th to endNight
15%5%25%35%16%1
611
June1st to 15thNight
14%5%26%41%11%
585
16th to endNight
11%227%42%14%1
585
July1st to 15thNight
7%324%36%25%2
555
16th to endNight
6%119%44%24%3
612
August1st to 15thNight
9%114%43%29%2
575
16th to endNight
15%221%32%24%3
621
September1st to 15thNight
10%321%39%18%5%
585
16th to endNight
15%5%26%32%17%1
686
October1st to 15thNight
22%7%27%26%14%1
780
16th to endNight
23%7%28%30%9%
832
November1st to 15thNight
22%7%32%27%8%
887
16th to endNight
22%12%34%23%7%
1050
December1st to 15thNight
22%9%34%24%8%
1050
16th to endNight
26%7%30%27%7%1
1120
Page generated at 2019-05-11 23:31:09. Version ac04

Copyright 2019 A. Danko


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