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 2021-06-17.

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%
21289
16%
61930
9%
21242
39%
21242
24%
41631

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
25%
1200
12%
3346
6%
1195
31%
1195
18%
2490
January16th to endNight
20%
1280
10%
3482
4%
1280
24%
1280
16%
2678
February1st to 15thNight
22%
1180
14%
3068
4%
1176
29%
1176
21%
2243
February16th to endNight
27%
926
16%
2612
7%
926
34%
926
20%
1832
March1st to 15thNight
31%
868
18%
2788
11%
868
38%
868
22%
1793
March16th to endNight
31%
768
16%
2728
14%
768
37%
768
18%
1808
April1st to 15thNight
26%
719
14%
2397
10%
719
34%
719
19%
1619
April16th to endNight
29%
714
15%
2301
10%
714
37%
714
22%
1519
May1st to 15thNight
27%
720
15%
1920
8%
720
33%
720
24%
1357
May16th to endNight
38%
755
13%
2009
6%
753
43%
753
29%
1325
June1st to 15thNight
41%
720
14%
1920
6%
720
44%
720
33%
1220
June16th to endNight
46%
681
14%
1816
6%
681
49%
681
37%
1109
July1st to 15thNight
57%
645
16%
1720
9%
645
59%
645
46%
967
July16th to endNight
58%
708
19%
1801
11%
675
65%
675
47%
1003
August1st to 15thNight
62%
665
21%
1908
19%
662
65%
662
37%
1117
August16th to endNight
52%
717
20%
2315
20%
717
58%
717
33%
1317
September1st to 15thNight
50%
675
23%
2250
21%
675
57%
675
33%
1246
September16th to endNight
43%
792
22%
2439
16%
792
50%
792
32%
1435
October1st to 15thNight
34%
900
21%
2700
13%
900
40%
900
27%
1701
October16th to endNight
32%
960
16%
2974
9%
960
39%
960
21%
2002
November1st to 15thNight
27%
1016
18%
3132
10%
1016
36%
1016
23%
2061
November16th to endNight
22%
1200
14%
3360
6%
1200
29%
1200
19%
2420
December1st to 15thNight
21%
1200
11%
3360
4%
1200
27%
1200
16%
2524
December16th to endNight
18%
1280
10%
3584
3%
1280
25%
1280
13%
2845

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
14%8%36%5%3445%6%36%
62841
Night
14%8%36%5%24446%38%
62099
Cloud CoverDay
23%7%25%5%23446%32%
62851
Night
22%7%36%423345%35%
62103
Cloud CoverDay
14%8%36%5%3445%7%36%
62849
Night
14%8%36%5%24446%38%
62103
TransparencyDay
47%412%24%10%
62526
Night
46%312%24%12%1
61931
SeeingDay
17%8%28%26%14%4
11240
Night
18%7%30%31%11%1
21289

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%11%6%10%7%46%346%26%
1912
16th to endDay
12%15%6%12%7%35%45%7%20%
2148
February1st to 15thDay
10%10%5%8%6%35%5%5%6%32%
2115
16th to endDay
12%10%5%9%6%3445%6%30%
2026
March1st to 15thDay
15%9%46%5%34446%36%
2494
16th to endDay
17%9%36%5%3345%7%33%
2904
April1st to 15thDay
18%10%46%7%2435%5%31%
2871
16th to endDay
21%9%26%5%24445%32%
2922
May1st to 15thDay
18%6%26%6%35%446%34%
3351
16th to endDay
16%6%25%6%3446%6%37%
3513
June1st to 15thDay
16%42442445%7%42%
3360
16th to endDay
10%5%25%5%35%6%6%9%37%
3172
July1st to 15thDay
8%314435%5%7%9%45%
3150
16th to endDay
8%323435%6%6%8%46%
3327
August1st to 15thDay
9%425%6%35%5%7%8%40%
2954
16th to endDay
13%5%2443446%8%43%
2942
September1st to 15thDay
14%5%24423446%46%
2700
16th to endDay
16%5%2443445%7%40%
2494
October1st to 15thDay
19%8%35%424345%39%
2250
16th to endDay
20%11%26%423335%36%
2306
November1st to 15thDay
14%10%46%5%33336%37%
2042
16th to endDay
15%11%5%6%6%2435%6%31%
1920
December1st to 15thDay
13%12%6%10%9%45%445%24%
1920
16th to endDay
18%16%7%11%8%4433318%
2048
January1st to 15thNight
11%10%6%10%7%35%44430%
3346
16th to endNight
12%12%6%10%6%345%5%6%25%
3482
February1st to 15thNight
8%10%5%10%6%35%446%33%
3065
16th to endNight
11%10%47%6%34446%34%
2612
March1st to 15thNight
12%7%46%5%34446%42%
2776
16th to endNight
16%8%36%5%34446%36%
2728
April1st to 15thNight
20%9%24433445%35%
2397
16th to endNight
20%8%2442335%7%36%
2301
May1st to 15thNight
22%6%15%5%23446%36%
1920
16th to endNight
14%5%25%42445%7%41%
2008
June1st to 15thNight
12%4244235%5%8%44%
1920
16th to endNight
9%324425%5%6%8%46%
1816
July1st to 15thNight
7%31332345%9%56%
1800
16th to endNight
6%22325%45%9%55%
1897
August1st to 15thNight
9%32442445%8%49%
1917
16th to endNight
12%5%24314345%52%
2315
September1st to 15thNight
10%414423446%51%
2250
16th to endNight
13%424423446%49%
2439
October1st to 15thNight
18%7%24423346%44%
2700
16th to endNight
17%9%35%5%24345%38%
2974
November1st to 15thNight
15%9%46%323347%39%
3132
16th to endNight
15%10%48%434446%33%
3360
December1st to 15thNight
14%12%6%9%7%24346%28%
3360
16th to endNight
17%14%5%11%7%3443423%
3584

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
20%9%5%8%6%44346%25%
1912
16th to endDay
22%14%5%11%6%3345%5%17%
2148
February1st to 15thDay
20%10%48%5%33345%29%
2115
16th to endDay
22%9%48%6%33446%26%
2026
March1st to 15thDay
24%8%35%434335%34%
2504
16th to endDay
26%8%25%5%23346%29%
2904
April1st to 15thDay
28%9%36%6%2334428%
2871
16th to endDay
31%9%25%5%23335%27%
2922
May1st to 15thDay
27%5%25%6%24345%30%
3351
16th to endDay
26%5%15%5%23445%33%
3513
June1st to 15thDay
26%5%2342345%6%36%
3360
16th to endDay
23%5%245%345%5%8%32%
3172
July1st to 15thDay
20%31443446%8%38%
3150
16th to endDay
21%2134335%5%7%41%
3327
August1st to 15thDay
15%4245%345%6%8%37%
2954
16th to endDay
17%5%1443345%7%41%
2942
September1st to 15thDay
18%5%14423346%43%
2700
16th to endDay
21%5%24434446%38%
2494
October1st to 15thDay
24%8%25%32433437%
2250
16th to endDay
25%10%25%42223435%
2306
November1st to 15thDay
23%9%36%5%23335%34%
2042
16th to endDay
25%9%45%5%2324429%
1920
December1st to 15thDay
23%12%48%7%35%33422%
1920
16th to endDay
28%13%5%10%8%3332317%
2048
January1st to 15thNight
20%9%49%6%3434428%
3346
16th to endNight
23%11%5%9%6%335%5%422%
3482
February1st to 15thNight
18%9%5%8%6%24445%29%
3058
16th to endNight
20%9%36%6%34445%31%
2612
March1st to 15thNight
21%6%25%5%34335%38%
2788
16th to endNight
26%7%26%423345%32%
2728
April1st to 15thNight
29%8%2442334431%
2397
16th to endNight
30%7%24323246%31%
2301
May1st to 15thNight
32%5%15%422336%31%
1919
16th to endNight
25%5%2432335%6%36%
2008
June1st to 15thNight
23%3144235%5%7%38%
1920
16th to endNight
21%32341445%7%41%
1816
July1st to 15thNight
19%313322348%48%
1800
16th to endNight
19%22223447%49%
1897
August1st to 15thNight
14%31442445%7%47%
1917
16th to endNight
16%414313345%50%
2315
September1st to 15thNight
15%424423445%48%
2250
16th to endNight
17%414323346%47%
2439
October1st to 15thNight
23%7%24322335%41%
2700
16th to endNight
22%8%25%43334435%
2974
November1st to 15thNight
23%8%35%322335%36%
3132
16th to endNight
25%9%47%433335%29%
3360
December1st to 15thNight
24%11%48%6%23335%24%
3360
16th to endNight
26%12%410%6%2333421%
3584

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
11%11%6%9%8%36%45%6%26%
1912
16th to endDay
12%15%6%12%7%3445%6%20%
2148
February1st to 15thDay
10%10%6%8%6%35%5%5%6%32%
2115
16th to endDay
12%10%49%7%3445%7%29%
2026
March1st to 15thDay
15%9%46%434446%36%
2504
16th to endDay
17%9%36%5%3435%7%33%
2902
April1st to 15thDay
18%10%37%6%24445%31%
2871
16th to endDay
21%9%35%5%34445%32%
2922
May1st to 15thDay
17%7%36%6%35%45%6%34%
3351
16th to endDay
16%5%25%6%345%5%6%37%
3513
June1st to 15thDay
16%42442345%8%42%
3360
16th to endDay
10%5%25%6%35%6%5%9%37%
3172
July1st to 15thDay
7%4145%35%5%7%9%45%
3150
16th to endDay
8%3245%35%5%6%9%46%
3327
August1st to 15thDay
9%425%6%35%5%7%8%40%
2954
16th to endDay
13%5%1443445%8%43%
2942
September1st to 15thDay
13%5%245%2345%7%45%
2700
16th to endDay
16%5%35%434447%40%
2494
October1st to 15thDay
19%8%35%424345%39%
2250
16th to endDay
20%11%35%433235%36%
2306
November1st to 15thDay
15%10%46%5%33336%37%
2042
16th to endDay
16%12%46%5%2435%5%31%
1920
December1st to 15thDay
13%13%6%10%9%35%445%24%
1920
16th to endDay
18%16%7%11%8%3433318%
2048
January1st to 15thNight
11%10%5%10%7%35%445%30%
3346
16th to endNight
13%13%6%10%6%345%5%5%25%
3482
February1st to 15thNight
8%10%5%9%7%35%445%33%
3058
16th to endNight
11%10%47%6%3445%6%34%
2612
March1st to 15thNight
12%7%36%5%34446%41%
2788
16th to endNight
17%8%36%5%34445%36%
2728
April1st to 15thNight
20%9%245%2445%5%35%
2397
16th to endNight
20%8%35%42345%6%36%
2301
May1st to 15thNight
22%6%26%5%24345%36%
1919
16th to endNight
15%425%42445%7%41%
2008
June1st to 15thNight
12%4244335%5%8%45%
1920
16th to endNight
10%323425%5%6%8%46%
1816
July1st to 15thNight
6%31331345%9%56%
1800
16th to endNight
6%233345%5%9%56%
1897
August1st to 15thNight
9%415%4245%5%8%49%
1917
16th to endNight
12%424324345%51%
2315
September1st to 15thNight
10%4245%2335%6%51%
2250
16th to endNight
14%424423446%48%
2439
October1st to 15thNight
18%6%24323346%43%
2700
16th to endNight
17%9%35%434445%38%
2974
November1st to 15thNight
15%9%46%423347%38%
3132
16th to endNight
16%10%48%5%33445%33%
3360
December1st to 15thNight
14%12%5%9%7%24446%28%
3360
16th to endNight
17%14%5%11%7%3443423%
3584

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
57%411%18%8%
1913
16th to endDay
63%311%15%5%
2148
February1st to 15thDay
51%314%19%8%1
2116
16th to endDay
53%49%22%9%
2026
March1st to 15thDay
49%313%21%10%1
2504
16th to endDay
51%212%24%8%1
2904
April1st to 15thDay
54%39%19%11%1
2871
16th to endDay
54%211%19%10%1
2922
May1st to 15thDay
50%312%22%10%
3351
16th to endDay
45%5%11%24%11%1
3517
June1st to 15thDay
39%312%30%12%
3360
16th to endDay
40%5%15%27%10%
3172
July1st to 15thDay
33%5%15%30%13%2
3001
16th to endDay
31%5%15%29%15%1
3160
August1st to 15thDay
37%5%14%29%11%1
2939
16th to endDay
37%414%29%13%
2942
September1st to 15thDay
37%413%30%13%
2700
16th to endDay
43%414%31%6%
2494
October1st to 15thDay
47%211%25%11%
2250
16th to endDay
51%212%24%8%
2306
November1st to 15thDay
48%411%21%12%1
2042
16th to endDay
53%317%18%6%
1920
December1st to 15thDay
62%211%17%5%
1920
16th to endDay
70%28%11%5%
2048
January1st to 15thNight
56%311%19%8%
3346
16th to endNight
59%311%17%6%
3482
February1st to 15thNight
52%311%22%8%1
3068
16th to endNight
50%310%24%9%1
2612
March1st to 15thNight
44%312%26%10%1
2788
16th to endNight
50%310%22%11%1
2728
April1st to 15thNight
50%38%20%15%1
2397
16th to endNight
47%29%21%16%2
2301
May1st to 15thNight
48%310%21%13%1
1920
16th to endNight
41%312%23%16%1
2010
June1st to 15thNight
35%5%11%29%16%1
1920
16th to endNight
32%414%30%14%2
1816
July1st to 15thNight
25%413%34%20%2
1720
16th to endNight
24%417%30%19%3
1801
August1st to 15thNight
31%414%28%18%2
1908
16th to endNight
33%314%29%15%2
2315
September1st to 15thNight
32%312%32%18%
2250
16th to endNight
36%313%33%12%
2439
October1st to 15thNight
42%29%29%14%1
2700
16th to endNight
48%311%22%12%1
2974
November1st to 15thNight
46%313%22%13%1
3132
16th to endNight
52%314%19%8%
3360
December1st to 15thNight
57%312%19%6%
3360
16th to endNight
64%310%15%5%
3584

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%33%25%11%2
270
16th to endDay
23%9%32%25%8%1
288
February1st to 15thDay
15%15%45%16%5%
270
16th to endDay
16%15%36%24%7%
240
March1st to 15thDay
19%14%37%17%10%1
270
16th to endDay
21%10%28%22%11%4
376
April1st to 15thDay
26%10%29%25%6%1
510
16th to endDay
26%11%22%25%11%2
562
May1st to 15thDay
21%10%30%25%10%2
768
16th to endDay
19%8%25%27%14%3
837
June1st to 15thDay
14%5%28%31%15%4
795
16th to endDay
13%6%29%27%16%6%
728
July1st to 15thDay
10%319%29%25%12%
700
16th to endDay
8%322%34%21%9%
755
August1st to 15thDay
10%320%30%28%8%
699
16th to endDay
16%419%28%23%7%
598
September1st to 15thDay
16%6%21%29%19%5%
495
16th to endDay
18%5%31%29%14%1
423
October1st to 15thDay
27%13%30%17%9%2
270
16th to endDay
26%14%34%19%5%
288
November1st to 15thDay
16%11%34%28%7%1
270
16th to endDay
27%11%39%15%5%
270
December1st to 15thDay
15%10%37%27%8%
270
16th to endDay
26%13%38%15%4
288
January1st to 15thNight
17%9%33%28%9%1
1200
16th to endNight
19%8%34%30%6%
1280
February1st to 15thNight
13%11%36%29%7%
1180
16th to endNight
16%10%34%30%7%
926
March1st to 15thNight
15%10%33%30%8%1
868
16th to endNight
20%7%30%28%10%1
768
April1st to 15thNight
25%7%32%27%6%
719
16th to endNight
23%6%30%28%10%
714
May1st to 15thNight
24%5%31%30%6%1
720
16th to endNight
16%5%26%35%14%1
755
June1st to 15thNight
13%6%26%41%12%
720
16th to endNight
11%325%43%14%1
681
July1st to 15thNight
7%222%37%26%3
645
16th to endNight
7%121%43%23%3
708
August1st to 15thNight
10%113%42%30%2
665
16th to endNight
14%121%35%23%2
717
September1st to 15thNight
12%323%38%17%5%
675
16th to endNight
15%5%28%32%16%1
792
October1st to 15thNight
22%8%29%26%13%
900
16th to endNight
22%7%29%30%8%
960
November1st to 15thNight
21%8%34%27%7%
1016
16th to endNight
22%12%35%23%7%
1200
December1st to 15thNight
20%9%35%25%8%
1200
16th to endNight
25%7%32%26%6%1
1280
Page generated at 2021-06-18 15:56:27. Version ac04

Copyright 2021 A. Danko


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