De Kalb
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the De Kalb clear sky chart from 2005-11-05 to 2018-04-23.

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
37%
16885
18%
49527
11%
16843
44%
16843
25%
32582

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
20%
975
15%
2716
5%
970
30%
970
20%
1927
January16th to endNight
23%
1040
13%
2853
4%
1040
29%
1040
18%
2081
February1st to 15thNight
22%
891
15%
2422
4%
891
29%
891
20%
1712
February16th to endNight
27%
683
18%
2049
7%
683
36%
683
18%
1425
March1st to 15thNight
31%
780
16%
2340
8%
780
37%
780
21%
1565
March16th to endNight
30%
647
16%
2171
11%
647
38%
647
19%
1476
April1st to 15thNight
29%
584
15%
1947
10%
584
39%
584
20%
1301
April16th to endNight
34%
558
19%
1813
12%
558
44%
558
23%
1201
May1st to 15thNight
36%
540
16%
1566
7%
540
44%
540
23%
1079
May16th to endNight
47%
562
18%
1498
10%
561
53%
561
33%
957
June1st to 15thNight
53%
540
16%
1440
10%
540
57%
540
36%
897
June16th to endNight
53%
540
17%
1440
10%
540
57%
540
32%
935
July1st to 15thNight
64%
510
17%
1360
11%
510
66%
510
42%
810
July16th to endNight
70%
564
22%
1417
17%
531
73%
531
43%
820
August1st to 15thNight
74%
539
22%
1575
20%
536
75%
536
43%
850
August16th to endNight
66%
573
21%
1910
22%
573
70%
573
35%
1049
September1st to 15thNight
64%
540
29%
1800
29%
540
69%
540
38%
941
September16th to endNight
60%
703
28%
1966
21%
703
65%
703
39%
1148
October1st to 15thNight
45%
720
24%
2099
18%
720
51%
720
32%
1273
October16th to endNight
30%
768
20%
2424
11%
768
40%
768
22%
1565
November1st to 15thNight
32%
760
23%
2471
15%
760
43%
760
24%
1536
November16th to endNight
27%
853
19%
2608
9%
853
38%
853
21%
1728
December1st to 15thNight
23%
975
14%
2730
4%
975
30%
975
18%
1984
December16th to endNight
18%
1040
12%
2912
3%
1040
26%
1040
13%
2322

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%36%5%35%45%7%36%
50002
Night
13%8%35%5%24446%40%
49695
Cloud CoverDay
13%8%36%5%3445%7%36%
50010
Night
14%7%35%5%24447%40%
49700
TransparencyDay
45%5%12%22%12%1
49688
Night
43%412%23%14%2
49527
SeeingDay
15%7%26%27%17%6%
6686
Night
17%7%29%30%12%1
16889

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
13%11%6%7%7%25%5%5%8%25%
1552
16th to endDay
12%14%6%9%6%34445%27%
1722
February1st to 15thDay
13%13%6%8%5%35%445%28%
1769
16th to endDay
15%10%5%7%5%34447%31%
1710
March1st to 15thDay
14%10%37%5%245%5%6%34%
1940
16th to endDay
16%8%47%6%36%45%6%29%
2415
April1st to 15thDay
18%10%5%6%6%34446%28%
2331
16th to endDay
19%8%36%5%24347%33%
2260
May1st to 15thDay
18%8%46%6%35%45%7%28%
2384
16th to endDay
12%7%35%5%35%5%5%8%37%
2617
June1st to 15thDay
10%5%25%5%25%5%5%8%42%
2520
16th to endDay
8%5%25%5%36%5%7%9%38%
2520
July1st to 15thDay
6%4245%36%7%6%8%45%
2520
16th to endDay
6%5%25%6%35%5%6%10%41%
2655
August1st to 15thDay
6%435%5%346%6%9%43%
2373
16th to endDay
10%5%25%5%35%46%8%43%
2292
September1st to 15thDay
12%31442445%6%49%
2160
16th to endDay
8%5%35%5%2445%7%46%
1981
October1st to 15thDay
16%5%26%323446%42%
1860
16th to endDay
18%8%345%2445%6%37%
1800
November1st to 15thDay
14%9%35%5%34447%38%
1717
16th to endDay
16%11%45%422336%37%
1680
December1st to 15thDay
15%13%5%7%5%34347%28%
1560
16th to endDay
19%14%6%7%7%34445%23%
1664
January1st to 15thNight
15%10%5%7%6%34445%34%
2716
16th to endNight
12%10%7%9%6%24446%29%
2853
February1st to 15thNight
14%12%5%6%5%24345%35%
2420
16th to endNight
15%11%36%42435%6%34%
2049
March1st to 15thNight
15%9%35%5%24335%39%
2327
16th to endNight
16%8%46%5%345%46%33%
2171
April1st to 15thNight
19%8%34424446%35%
1947
16th to endNight
17%8%26%424346%39%
1813
May1st to 15thNight
16%6%246%25%5%6%7%34%
1566
16th to endNight
9%6%24425%5%7%9%42%
1496
June1st to 15thNight
10%424424447%48%
1440
16th to endNight
7%435%5%36%6%7%8%42%
1440
July1st to 15thNight
6%3134245%5%10%51%
1440
16th to endNight
6%223435%47%11%49%
1513
August1st to 15thNight
33134345%7%9%54%
1584
16th to endNight
9%41442345%9%50%
1910
September1st to 15thNight
9%413323346%57%
1800
16th to endNight
9%41442445%7%51%
1966
October1st to 15thNight
13%5%24423345%49%
2099
16th to endNight
17%9%34323246%41%
2424
November1st to 15thNight
14%7%345%23336%45%
2471
16th to endNight
15%8%46%424346%38%
2608
December1st to 15thNight
18%9%38%6%34445%31%
2730
16th to endNight
20%14%5%8%6%35%435%22%
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
14%11%5%8%6%25%5%48%26%
1552
16th to endDay
12%14%6%9%6%34445%27%
1722
February1st to 15thDay
13%13%5%8%5%26%445%28%
1769
16th to endDay
15%10%47%5%3445%6%31%
1710
March1st to 15thDay
15%9%37%42445%6%34%
1950
16th to endDay
17%8%47%5%36%45%7%30%
2413
April1st to 15thDay
18%11%46%6%34446%28%
2331
16th to endDay
20%8%25%5%34446%33%
2260
May1st to 15thDay
18%9%36%5%45%5%5%7%28%
2384
16th to endDay
13%6%25%5%35%5%5%9%37%
2617
June1st to 15thDay
11%425%5%25%46%7%43%
2520
16th to endDay
9%5%25%5%36%6%7%9%38%
2520
July1st to 15thDay
7%3235%35%6%6%8%44%
2520
16th to endDay
6%5%26%5%35%6%6%9%42%
2655
August1st to 15thDay
7%425%6%35%5%7%8%43%
2373
16th to endDay
11%5%246%35%5%5%9%42%
2292
September1st to 15thDay
12%3234345%5%6%49%
2160
16th to endDay
8%5%25%5%2435%8%46%
1981
October1st to 15thDay
15%6%25%42345%6%42%
1860
16th to endDay
18%7%345%2445%6%37%
1800
November1st to 15thDay
13%10%35%5%2445%6%39%
1717
16th to endDay
17%10%45%5%23335%37%
1680
December1st to 15thDay
15%13%48%5%35%347%29%
1560
16th to endDay
20%14%6%7%6%34445%23%
1664
January1st to 15thNight
15%11%47%5%24435%35%
2716
16th to endNight
12%10%7%9%6%3445%6%30%
2853
February1st to 15thNight
14%12%5%6%423345%35%
2413
16th to endNight
16%11%36%5%24346%34%
2049
March1st to 15thNight
16%9%35%5%33336%39%
2340
16th to endNight
16%8%46%5%2445%6%33%
2171
April1st to 15thNight
19%8%344245%46%36%
1947
16th to endNight
18%8%25%424346%39%
1813
May1st to 15thNight
16%7%245%25%5%6%7%34%
1565
16th to endNight
10%5%25%5%236%7%9%42%
1496
June1st to 15thNight
10%425%424447%48%
1440
16th to endNight
7%425%5%36%5%6%8%42%
1440
July1st to 15thNight
6%313425%46%9%51%
1440
16th to endNight
5%2234345%7%10%49%
1513
August1st to 15thNight
33134335%6%9%54%
1584
16th to endNight
9%4134235%5%9%50%
1910
September1st to 15thNight
9%413323346%58%
1800
16th to endNight
8%42342345%7%51%
1966
October1st to 15thNight
13%5%24423345%49%
2099
16th to endNight
18%8%24423346%41%
2424
November1st to 15thNight
14%7%34423336%45%
2471
16th to endNight
16%8%46%424347%38%
2608
December1st to 15thNight
18%9%38%6%2435%6%31%
2730
16th to endNight
21%14%5%8%6%34435%22%
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
54%413%16%10%
1553
16th to endDay
57%314%14%8%
1722
February1st to 15thDay
56%311%18%8%1
1771
16th to endDay
52%5%12%20%8%1
1710
March1st to 15thDay
49%5%12%22%8%
1950
16th to endDay
52%5%13%21%5%
2415
April1st to 15thDay
54%410%21%8%
2331
16th to endDay
50%412%18%11%2
2260
May1st to 15thDay
54%5%11%22%6%
2384
16th to endDay
42%6%13%21%13%1
2621
June1st to 15thDay
37%5%12%26%16%1
2520
16th to endDay
39%7%13%22%15%2
2520
July1st to 15thDay
33%7%13%28%14%2
2371
16th to endDay
34%6%18%24%13%3
2488
August1st to 15thDay
35%6%13%28%14%1
2358
16th to endDay
36%5%13%25%16%2
2292
September1st to 15thDay
33%5%10%26%20%4
2160
16th to endDay
35%410%29%18%1
1981
October1st to 15thDay
41%5%10%25%14%1
1860
16th to endDay
46%413%22%11%1
1800
November1st to 15thDay
45%311%23%13%2
1717
16th to endDay
49%313%25%7%
1680
December1st to 15thDay
55%313%18%8%
1560
16th to endDay
62%411%12%7%
1664
January1st to 15thNight
50%311%19%14%
2716
16th to endNight
54%315%16%9%
2853
February1st to 15thNight
50%312%20%12%
2422
16th to endNight
50%411%22%9%2
2049
March1st to 15thNight
47%312%21%12%2
2340
16th to endNight
50%312%20%11%1
2171
April1st to 15thNight
48%310%21%13%2
1947
16th to endNight
46%39%23%10%5%
1813
May1st to 15thNight
46%5%12%23%11%
1566
16th to endNight
35%6%15%21%18%2
1498
June1st to 15thNight
34%412%24%20%2
1440
16th to endNight
36%7%12%21%19%2
1440
July1st to 15thNight
29%413%29%20%2
1360
16th to endNight
26%6%16%27%18%4
1417
August1st to 15thNight
24%5%15%32%19%2
1575
16th to endNight
30%5%13%27%18%4
1910
September1st to 15thNight
27%49%29%26%3
1800
16th to endNight
30%411%32%19%2
1966
October1st to 15thNight
35%410%26%21%2
2099
16th to endNight
45%310%25%14%1
2424
November1st to 15thNight
41%39%24%17%3
2471
16th to endNight
45%312%25%12%
2608
December1st to 15thNight
54%310%21%8%
2730
16th to endNight
64%310%14%6%
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
21%8%36%27%5%
135
16th to endDay
19%7%36%27%8%1
144
February1st to 15thDay
22%13%42%20%1
135
16th to endDay
31%13%29%17%8%
120
March1st to 15thDay
28%14%26%22%7%
135
16th to endDay
25%7%31%22%10%2
284
April1st to 15thDay
23%10%32%23%9%
330
16th to endDay
23%10%22%27%11%4
289
May1st to 15thDay
23%9%28%23%11%3
341
16th to endDay
17%8%26%25%15%5%
517
June1st to 15thDay
10%329%32%19%4
495
16th to endDay
10%7%30%30%13%6%
495
July1st to 15thDay
9%321%33%21%11%
475
16th to endDay
6%321%31%26%10%
515
August1st to 15thDay
8%315%31%26%14%
427
16th to endDay
10%315%27%29%13%
332
September1st to 15thDay
11%313%31%29%9%
315
16th to endDay
8%420%27%30%7%
314
October1st to 15thDay
18%7%22%27%19%5%
195
16th to endDay
25%9%29%29%5%
144
November1st to 15thDay
16%8%28%22%16%6%
135
16th to endDay
30%6%37%17%7%
135
December1st to 15thDay
17%16%34%21%9%
135
16th to endDay
24%15%49%6%3
144
January1st to 15thNight
20%11%39%21%6%
975
16th to endNight
17%11%37%29%4
1040
February1st to 15thNight
21%10%36%25%5%
894
16th to endNight
21%12%32%27%5%
683
March1st to 15thNight
20%9%33%28%8%
780
16th to endNight
20%7%33%28%8%1
647
April1st to 15thNight
24%10%32%27%5%
584
16th to endNight
22%6%31%27%10%
558
May1st to 15thNight
19%7%30%32%10%
540
16th to endNight
12%428%35%18%
563
June1st to 15thNight
11%323%46%14%
540
16th to endNight
8%227%41%17%2
540
July1st to 15thNight
8%118%39%30%2
510
16th to endNight
6%14%47%27%4
564
August1st to 15thNight
49%48%30%5%
539
16th to endNight
9%213%36%34%3
573
September1st to 15thNight
11%216%34%29%4
540
16th to endNight
11%418%35%25%4
703
October1st to 15thNight
16%6%26%32%16%1
720
16th to endNight
23%9%33%23%10%
768
November1st to 15thNight
18%9%34%24%11%1
760
16th to endNight
19%13%33%25%7%
853
December1st to 15thNight
24%12%33%24%5%
975
16th to endNight
27%11%33%24%3
1040
Page generated at 2018-04-24 09:03:05. Version ac04

Copyright 2018 A. Danko


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