De Kalb
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the De Kalb clear sky chart from 2005-11-06 to 2024-01-12.

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
36%
24607
18%
74642
11%
24555
43%
24555
24%
49506

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 10thNight
20%
950
15%
2648
4%
946
30%
946
20%
1893
January11th to 20thNight
19%
906
13%
2535
5%
906
26%
906
16%
1901
January21st to endNight
22%
990
12%
2690
4%
990
28%
990
16%
2029
February1st to 10thNight
18%
900
12%
2340
3%
900
24%
900
18%
1743
February11th to 20thNight
26%
700
19%
2099
8%
700
34%
700
20%
1414
February21st to endNight
20%
592
18%
1776
5%
592
32%
592
19%
1242
March1st to 10thNight
25%
720
14%
2160
6%
720
31%
720
19%
1470
March11th to 20thNight
33%
662
19%
2102
11%
662
42%
662
24%
1339
March21st to endNight
26%
594
15%
1985
9%
594
34%
594
16%
1421
April1st to 10thNight
27%
540
16%
1800
9%
540
38%
540
20%
1174
April11th to 20thNight
30%
533
20%
1775
13%
533
42%
533
21%
1151
April21st to endNight
31%
540
16%
1733
9%
540
41%
540
21%
1162
May1st to 10thNight
34%
540
15%
1620
8%
540
41%
540
25%
1079
May11th to 20thNight
37%
531
18%
1426
8%
531
44%
531
28%
948
May21st to endNight
45%
584
17%
1552
9%
582
51%
582
30%
1030
June1st to 10thNight
54%
540
17%
1440
11%
540
58%
540
37%
879
June11th to 20thNight
53%
540
20%
1440
12%
540
58%
540
36%
882
June21st to endNight
53%
540
18%
1440
10%
540
57%
540
31%
939
July1st to 10thNight
70%
525
17%
1400
13%
525
71%
525
41%
841
July11th to 20thNight
60%
522
21%
1392
15%
522
64%
522
43%
813
July21st to endNight
69%
591
22%
1487
17%
558
71%
558
42%
866
August1st to 10thNight
69%
537
21%
1457
18%
534
71%
534
40%
845
August11th to 20thNight
69%
534
22%
1776
24%
534
72%
534
38%
961
August21st to endNight
65%
594
24%
1980
24%
594
70%
594
38%
1037
September1st to 10thNight
59%
540
25%
1800
23%
540
64%
540
34%
992
September11th to 20thNight
61%
609
34%
1869
30%
609
66%
609
38%
1037
September21st to endNight
51%
720
24%
1980
16%
720
57%
720
35%
1199
October1st to 10thNight
47%
720
24%
2068
18%
720
52%
720
34%
1249
October11th to 20thNight
31%
720
22%
2160
10%
720
43%
720
25%
1357
October21st to endNight
26%
792
17%
2555
10%
792
36%
792
20%
1708
November1st to 10thNight
31%
740
26%
2406
16%
740
45%
740
27%
1415
November11th to 20thNight
25%
760
19%
2470
8%
760
38%
760
19%
1630
November21st to endNight
25%
867
18%
2577
8%
867
36%
867
21%
1760
December1st to 10thNight
22%
950
14%
2660
5%
950
29%
950
19%
1905
December11th to 20thNight
24%
948
15%
3200
5%
948
32%
948
15%
2286
December21st to endNight
16%
1036
6%
4844
3%
1026
23%
1026
7%
3909

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
13%8%47%6%35%5%5%7%37%
74788
Night
14%9%46%5%3445%7%39%
74943
TransparencyDay
46%5%13%23%12%2
74489
Night
45%5%12%23%14%2
74763
SeeingDay
16%9%28%26%15%6%
14647
Night
17%9%31%30%12%1
24621

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 10thDay
14%10%5%9%8%36%5%5%8%27%
1517
11th to 20thDay
13%14%7%13%7%345%5%6%24%
1448
21st to endDay
14%16%6%11%6%35%45%6%24%
1664
February1st to 10thDay
14%14%5%8%8%47%45%7%25%
1620
11th to 20thDay
13%10%47%7%45%5%5%6%34%
1747
21st to endDay
15%12%6%11%5%3445%6%29%
1480
March1st to 10thDay
15%12%49%5%345%47%33%
1800
11th to 20thDay
14%8%36%6%46%46%8%36%
1872
21st to endDay
20%10%49%6%47%45%6%25%
2371
April1st to 10thDay
17%11%5%7%7%4445%7%30%
2160
11th to 20thDay
16%9%36%6%45%5%5%7%33%
2134
21st to endDay
20%8%37%6%45%5%46%32%
2225
May1st to 10thDay
16%9%46%6%45%5%6%7%31%
2340
11th to 20thDay
19%8%36%5%45%5%5%8%34%
2467
21st to endDay
13%7%36%6%46%5%6%9%36%
2725
June1st to 10thDay
9%425%5%35%5%6%8%46%
2520
11th to 20thDay
9%5%25%5%35%5%6%9%46%
2520
21st to endDay
10%6%36%6%46%6%7%8%38%
2520
July1st to 10thDay
7%4345%35%6%7%9%47%
2520
11th to 20thDay
9%424435%6%6%10%46%
2520
21st to endDay
6%5%26%5%45%6%6%9%45%
2743
August1st to 10thDay
8%5%35%6%45%5%7%10%43%
2468
11th to 20thDay
9%5%25%5%36%6%7%9%44%
2125
21st to endDay
9%4246%35%5%6%9%48%
2376
September1st to 10thDay
12%435%5%445%5%7%46%
2160
11th to 20thDay
13%3243235%5%7%53%
2072
21st to endDay
10%6%36%6%3446%8%45%
1980
October1st to 10thDay
13%6%35%4345%5%7%46%
1890
11th to 20thDay
18%9%36%5%3445%6%35%
1800
21st to endDay
21%8%45%5%34446%37%
1800
November1st to 10thDay
11%9%36%5%3445%6%45%
1672
11th to 20thDay
15%12%48%6%245%5%8%32%
1710
21st to endDay
18%10%48%6%34345%35%
1601
December1st to 10thDay
14%13%5%9%6%35%446%32%
1520
11th to 20thDay
12%12%5%9%7%45%5%5%7%28%
1918
21st to endDay
19%21%10%11%7%4333315%
2783
January1st to 10thNight
13%12%49%7%345%45%35%
2648
11th to 20thNight
15%13%6%10%6%345%46%28%
2535
21st to endNight
14%12%7%9%7%35%5%5%7%26%
2690
February1st to 10thNight
15%13%6%8%6%44445%31%
2340
11th to 20thNight
14%10%37%6%3445%6%38%
2098
21st to endNight
17%13%5%6%5%3435%6%35%
1776
March1st to 10thNight
17%9%46%6%44446%36%
2160
11th to 20thNight
12%8%46%5%345%6%6%41%
2102
21st to endNight
20%10%5%7%6%35%446%30%
1985
April1st to 10thNight
17%8%46%5%345%45%40%
1800
11th to 20thNight
19%8%345%34446%39%
1775
21st to endNight
17%8%36%6%35%45%7%37%
1733
May1st to 10thNight
14%7%35%5%36%5%7%8%37%
1620
11th to 20thNight
16%6%25%5%25%5%5%10%39%
1425
21st to endNight
12%6%26%6%346%7%8%41%
1551
June1st to 10thNight
9%5%25%5%245%6%8%49%
1440
11th to 20thNight
9%5%25%435%5%6%9%48%
1440
21st to endNight
8%5%35%6%36%6%6%8%44%
1440
July1st to 10thNight
6%423436%5%7%11%49%
1440
11th to 20thNight
6%424435%5%6%10%52%
1440
21st to endNight
5%325%5%35%5%7%9%51%
1575
August1st to 10thNight
4415%5%346%7%9%51%
1466
11th to 20thNight
7%5%244245%5%10%52%
1776
21st to endNight
9%41342446%9%53%
1980
September1st to 10thNight
10%6%34423446%55%
1800
11th to 20thNight
10%424433447%54%
1869
21st to endNight
11%5%236%3445%8%48%
1980
October1st to 10thNight
12%5%25%43445%6%51%
2068
11th to 20thNight
17%8%25%434346%45%
2160
21st to endNight
19%10%35%5%2445%6%37%
2555
November1st to 10thNight
12%8%25%423346%50%
2406
11th to 20thNight
15%8%47%6%3445%7%37%
2470
21st to endNight
16%10%46%5%34446%37%
2577
December1st to 10thNight
16%10%48%7%3445%7%32%
2660
11th to 20thNight
15%12%48%6%3445%6%32%
3279
21st to endNight
21%17%7%9%7%345%5%6%16%
4884

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 10thDay
55%5%13%16%11%
1518
11th to 20thDay
60%414%15%6%1
1448
21st to endDay
61%412%13%10%
1664
February1st to 10thDay
58%412%16%8%2
1620
11th to 20thDay
50%5%12%22%10%2
1757
21st to endDay
55%6%10%19%9%1
1480
March1st to 10thDay
53%5%13%22%8%1
1800
11th to 20thDay
46%6%13%22%11%1
1872
21st to endDay
59%5%11%18%6%1
2371
April1st to 10thDay
53%5%11%22%9%
2160
11th to 20thDay
48%6%10%22%11%2
2134
21st to endDay
52%5%12%17%12%1
2225
May1st to 10thDay
51%5%13%23%7%
2340
11th to 20thDay
48%6%11%23%11%
2471
21st to endDay
44%6%14%19%15%2
2725
June1st to 10thDay
34%6%14%28%17%2
2520
11th to 20thDay
35%5%12%25%21%3
2520
21st to endDay
41%7%14%23%13%2
2520
July1st to 10thDay
32%7%15%30%14%3
2451
11th to 20thDay
32%6%16%28%16%2
2445
21st to endDay
33%6%17%26%15%3
2591
August1st to 10thDay
34%7%17%30%11%2
2453
11th to 20thDay
36%6%14%27%16%1
2125
21st to endDay
31%6%12%28%20%3
2376
September1st to 10thDay
37%6%12%24%17%4
2160
11th to 20thDay
31%5%12%29%21%3
2072
21st to endDay
37%410%28%19%2
1980
October1st to 10thDay
38%6%11%26%18%1
1890
11th to 20thDay
49%5%11%21%13%2
1800
21st to endDay
49%412%23%10%2
1800
November1st to 10thDay
40%413%25%16%2
1672
11th to 20thDay
51%413%22%10%1
1710
21st to endDay
53%412%23%8%
1601
December1st to 10thDay
54%413%20%8%1
1520
11th to 20thDay
54%314%18%8%2
1915
21st to endDay
76%37%9%4
2783
January1st to 10thNight
51%411%20%13%1
2648
11th to 20thNight
57%413%15%10%
2535
21st to endNight
58%312%16%10%1
2690
February1st to 10thNight
55%311%17%12%1
2340
11th to 20thNight
47%411%23%13%1
2099
21st to endNight
51%411%19%11%4
1776
March1st to 10thNight
50%312%22%11%1
2160
11th to 20thNight
42%5%13%21%17%3
2102
21st to endNight
56%311%18%11%1
1985
April1st to 10thNight
45%413%22%14%2
1800
11th to 20thNight
46%38%22%16%4
1775
21st to endNight
47%5%11%24%10%3
1733
May1st to 10thNight
45%5%14%25%11%
1620
11th to 20thNight
42%6%14%23%14%1
1426
21st to endNight
39%7%14%21%17%2
1552
June1st to 10thNight
33%5%13%26%20%3
1440
11th to 20thNight
33%6%13%24%23%3
1440
21st to endNight
37%7%14%23%17%3
1440
July1st to 10thNight
29%6%15%28%18%4
1400
11th to 20thNight
28%6%14%30%20%3
1392
21st to endNight
28%6%17%26%18%6%
1487
August1st to 10thNight
27%7%17%32%14%2
1457
11th to 20thNight
27%6%16%29%20%1
1776
21st to endNight
27%5%12%30%21%5%
1980
September1st to 10thNight
30%5%11%27%23%3
1800
11th to 20thNight
29%5%9%33%22%2
1869
21st to endNight
34%412%30%17%2
1980
October1st to 10thNight
34%5%10%27%22%2
2068
11th to 20thNight
42%39%25%19%2
2160
21st to endNight
48%410%24%13%1
2555
November1st to 10thNight
36%5%9%27%19%3
2406
11th to 20thNight
47%312%23%13%2
2470
21st to endNight
48%412%24%12%
2577
December1st to 10thNight
53%311%23%9%1
2660
11th to 20thNight
53%412%20%10%1
3281
21st to endNight
68%6%10%12%4
4884

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 10thDay
20%11%33%26%9%1
270
11th to 20thDay
19%13%41%20%5%2
243
21st to endDay
22%13%35%23%6%1
264
February1st to 10thDay
20%17%41%19%31
240
11th to 20thDay
24%15%34%22%5%
240
21st to endDay
24%21%37%17%2
198
March1st to 10thDay
21%18%37%20%4
240
11th to 20thDay
23%15%37%15%10%1
240
21st to endDay
28%13%31%20%7%2
457
April1st to 10thDay
23%11%36%25%5%
420
11th to 20thDay
20%17%31%20%10%3
412
21st to endDay
22%12%30%24%9%2
420
May1st to 10thDay
22%11%30%26%9%2
423
11th to 20thDay
22%11%26%25%13%3
613
21st to endDay
16%8%26%24%18%8%
679
June1st to 10thDay
9%5%29%31%19%7%
630
11th to 20thDay
10%6%28%31%19%5%
630
21st to endDay
12%8%27%32%15%5%
630
July1st to 10thDay
9%316%30%23%18%
621
11th to 20thDay
11%322%32%22%11%
618
21st to endDay
6%421%36%26%7%
684
August1st to 10thDay
9%218%32%27%12%
617
11th to 20thDay
10%6%15%27%24%19%
439
21st to endDay
7%417%32%28%12%
495
September1st to 10thDay
14%420%30%25%7%
450
11th to 20thDay
12%417%30%25%12%
450
21st to endDay
11%11%26%26%20%6%
450
October1st to 10thDay
16%5%28%27%18%5%
360
11th to 20thDay
22%18%31%21%7%
270
21st to endDay
33%12%29%20%5%1
297
November1st to 10thDay
14%13%36%23%10%4
270
11th to 20thDay
22%17%34%19%6%2
270
21st to endDay
24%10%34%26%6%
270
December1st to 10thDay
19%14%38%21%7%1
270
11th to 20thDay
17%12%39%23%9%
270
21st to endDay
25%18%40%15%2
297
January1st to 10thNight
18%13%39%24%5%
950
11th to 20thNight
20%12%38%24%6%1
906
21st to endNight
20%11%35%30%4
990
February1st to 10thNight
22%13%38%22%4
900
11th to 20thNight
21%13%35%26%5%
703
21st to endNight
23%12%39%21%4
592
March1st to 10thNight
21%11%37%24%6%
720
11th to 20thNight
16%10%36%29%8%1
662
21st to endNight
23%11%33%25%6%1
594
April1st to 10thNight
20%13%36%25%5%
540
11th to 20thNight
24%11%32%26%7%
533
21st to endNight
20%9%34%30%8%
540
May1st to 10thNight
16%11%34%31%8%1
540
11th to 20thNight
18%7%33%29%12%
531
21st to endNight
14%428%34%20%
584
June1st to 10thNight
10%426%44%17%
540
11th to 20thNight
10%329%45%12%1
540
21st to endNight
10%426%39%20%1
540
July1st to 10thNight
7%214%41%31%5%
525
11th to 20thNight
9%221%37%27%4
522
21st to endNight
6%216%49%26%2
591
August1st to 10thNight
5%114%45%30%5%
537
11th to 20thNight
7%213%41%32%5%
534
21st to endNight
10%118%38%30%2
594
September1st to 10thNight
11%420%34%26%4
540
11th to 20thNight
10%419%34%28%4
609
21st to endNight
13%7%24%35%18%3
720
October1st to 10thNight
15%5%28%33%17%2
720
11th to 20thNight
22%12%30%26%10%
720
21st to endNight
25%11%34%22%8%
792
November1st to 10thNight
16%10%39%24%11%1
740
11th to 20thNight
19%16%34%24%7%
760
21st to endNight
21%11%37%25%6%
867
December1st to 10thNight
21%13%38%23%6%
950
11th to 20thNight
22%11%34%27%5%1
950
21st to endNight
27%14%34%22%3
1045
Page generated at 2024-01-08 21:31:24. Version ac07

Copyright 2024 Attilla Danko


De Kalb Clear Sky Chart |Charts Home