Elgin
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Elgin 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
47%
22538
14%
74638
14%
22495
49%
22495
20%
50586

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
25%
757
7%
2646
6%
756
28%
756
8%
2157
January11th to 20thNight
35%
728
9%
2548
8%
728
37%
728
12%
1950
January21st to endNight
36%
792
9%
2772
8%
792
39%
792
11%
2123
February1st to 10thNight
29%
720
6%
2434
5%
720
31%
720
9%
1947
February11th to 20thNight
37%
704
10%
2144
10%
700
39%
700
14%
1654
February21st to endNight
27%
592
11%
1776
8%
592
32%
592
11%
1419
March1st to 10thNight
35%
720
10%
2160
9%
720
38%
720
15%
1625
March11th to 20thNight
38%
720
10%
2123
9%
720
40%
720
16%
1593
March21st to endNight
31%
792
7%
1980
3%
792
32%
792
13%
1617
April1st to 10thNight
38%
720
9%
1800
5%
720
39%
720
17%
1407
April11th to 20thNight
40%
707
13%
1775
6%
707
42%
707
21%
1308
April21st to endNight
47%
540
12%
1620
10%
540
49%
540
21%
1146
May1st to 10thNight
53%
455
16%
1535
17%
455
54%
455
25%
955
May11th to 20thNight
62%
354
14%
1416
17%
354
65%
354
20%
891
May21st to endNight
56%
388
9%
1552
15%
388
57%
388
17%
1024
June1st to 10thNight
59%
360
9%
1440
15%
360
61%
360
19%
911
June11th to 20thNight
53%
360
12%
1440
16%
360
57%
360
21%
864
June21st to endNight
72%
360
18%
1440
31%
360
74%
360
35%
692
July1st to 10thNight
80%
350
20%
1400
34%
350
84%
350
48%
572
July11th to 20thNight
82%
348
27%
1392
41%
348
87%
348
57%
512
July21st to endNight
84%
394
35%
1488
49%
372
88%
372
62%
518
August1st to 10thNight
81%
358
32%
1424
40%
356
86%
356
54%
542
August11th to 20thNight
81%
525
32%
1593
28%
525
82%
525
57%
722
August21st to endNight
71%
792
32%
1980
20%
792
73%
792
58%
1035
September1st to 10thNight
75%
720
33%
1800
19%
720
77%
720
61%
924
September11th to 20thNight
71%
720
30%
1890
21%
720
73%
720
43%
1094
September21st to endNight
63%
720
27%
1980
23%
720
65%
720
39%
1176
October1st to 10thNight
59%
720
18%
2056
17%
720
62%
720
29%
1313
October11th to 20thNight
52%
720
20%
2217
19%
720
55%
720
24%
1464
October21st to endNight
47%
792
16%
2574
17%
792
50%
792
18%
1792
November1st to 10thNight
36%
740
12%
2405
11%
740
39%
740
14%
1796
November11th to 20thNight
33%
760
9%
2503
7%
760
35%
760
13%
1924
November21st to endNight
39%
760
10%
2660
8%
760
42%
760
16%
1906
December1st to 10thNight
35%
760
8%
2660
7%
760
37%
760
11%
2055
December11th to 20thNight
25%
759
7%
3196
5%
759
28%
759
7%
2570
December21st to endNight
23%
831
4%
4819
6%
817
25%
817
5%
3388

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
8%9%47%6%35%5%5%7%41%
74802
Night
9%10%47%6%45%5%5%6%39%
74944
TransparencyDay
42%9%12%18%14%5%
74506
Night
44%9%13%18%11%4
74761
SeeingDay
12%17%29%25%13%4
13272
Night
13%12%22%32%19%2
22548

By Month

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 10thDay
9%15%5%10%10%6%8%6%7%6%18%
1519
11th to 20thDay
10%14%6%10%7%45%6%6%7%24%
1451
21st to endDay
9%14%49%7%5%8%6%6%6%26%
1584
February1st to 10thDay
9%17%6%10%8%46%5%6%6%23%
1525
11th to 20thDay
10%18%6%10%8%45%5%46%23%
1704
21st to endDay
9%14%5%11%10%5%6%5%47%23%
1480
March1st to 10thDay
9%15%7%10%9%46%6%6%6%23%
1800
11th to 20thDay
10%14%5%9%8%5%6%7%7%7%23%
1834
21st to endDay
12%18%6%9%8%5%7%6%6%6%18%
2376
April1st to 10thDay
11%15%5%10%8%46%5%5%7%24%
2160
11th to 20thDay
11%12%48%6%45%5%5%8%31%
2132
21st to endDay
12%13%48%6%35%46%7%32%
2340
May1st to 10thDay
9%10%46%5%35%47%8%38%
2421
11th to 20thDay
12%9%46%7%36%6%6%7%34%
2477
21st to endDay
14%9%47%6%45%46%7%33%
2723
June1st to 10thDay
14%8%37%5%35%46%8%36%
2520
11th to 20thDay
13%7%36%5%345%5%7%42%
2520
21st to endDay
5%323424346%64%
2520
July1st to 10thDay
221332345%6%68%
2520
11th to 20thDay
2212313345%74%
2520
21st to endDay
112223346%77%
2741
August1st to 10thDay
3213324446%69%
2507
11th to 20thDay
3213312346%73%
2304
21st to endDay
4313324346%66%
2376
September1st to 10thDay
4313323345%72%
2160
11th to 20thDay
7%42442445%7%56%
2070
21st to endDay
8%6%25%5%2445%7%53%
1980
October1st to 10thDay
12%6%35%5%44345%47%
1902
11th to 20thDay
10%8%36%5%35%5%6%7%43%
1742
21st to endDay
11%10%38%7%5%6%446%35%
1782
November1st to 10thDay
14%11%49%8%46%5%47%28%
1674
11th to 20thDay
10%15%6%8%8%5%7%7%7%7%20%
1676
21st to endDay
9%13%6%8%6%46%6%7%8%28%
1520
December1st to 10thDay
8%14%6%9%7%47%6%6%8%25%
1520
11th to 20thDay
7%13%5%9%10%5%8%6%7%7%21%
1928
21st to endDay
7%12%6%10%9%5%8%7%5%6%24%
2794
January1st to 10thNight
9%15%6%10%10%5%6%6%6%7%19%
2646
11th to 20thNight
11%14%5%8%7%46%5%6%7%25%
2548
21st to endNight
10%15%5%8%9%46%6%5%7%26%
2772
February1st to 10thNight
11%17%5%10%8%45%5%6%6%24%
2434
11th to 20thNight
9%17%5%10%7%36%5%5%6%29%
2143
21st to endNight
9%16%8%10%9%45%5%5%6%24%
1776
March1st to 10thNight
11%11%5%8%8%47%5%5%7%29%
2160
11th to 20thNight
10%12%47%6%47%7%6%7%30%
2123
21st to endNight
11%16%5%9%7%46%5%6%7%24%
1980
April1st to 10thNight
11%12%5%9%7%46%5%5%5%31%
1800
11th to 20thNight
13%10%5%7%6%35%45%5%38%
1775
21st to endNight
10%9%37%5%35%5%6%7%40%
1620
May1st to 10thNight
8%7%26%5%35%5%5%7%48%
1535
11th to 20thNight
11%7%35%435%6%7%8%41%
1416
21st to endNight
14%7%36%5%35%5%6%8%38%
1552
June1st to 10thNight
13%6%36%5%35%5%6%9%40%
1440
11th to 20thNight
13%6%345%2445%7%46%
1440
21st to endNight
441442445%7%61%
1440
July1st to 10thNight
3212223447%71%
1440
11th to 20thNight
1112222335%78%
1440
21st to endNight
112322346%77%
1576
August1st to 10thNight
321221236%8%70%
1432
11th to 20thNight
2112323245%74%
1593
21st to endNight
321332335%6%70%
1980
September1st to 10thNight
5%213222336%72%
1800
11th to 20thNight
5%324325%45%6%59%
1890
21st to endNight
9%6%25%333346%57%
1980
October1st to 10thNight
9%7%26%5%345%5%6%48%
2056
11th to 20thNight
11%7%46%6%4445%6%45%
2217
21st to endNight
10%8%46%7%5%5%6%5%5%39%
2574
November1st to 10thNight
15%11%47%7%36%6%5%6%30%
2405
11th to 20thNight
13%13%47%7%5%7%6%6%6%25%
2503
21st to endNight
9%12%5%8%6%46%6%6%6%31%
2660
December1st to 10thNight
8%13%5%9%9%5%7%5%7%8%25%
2660
11th to 20thNight
8%15%5%10%10%6%7%6%6%7%20%
3276
21st to endNight
8%13%5%10%9%7%9%6%5%7%20%
4862

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
64%14%12%8%2
1519
11th to 20thDay
58%11%12%13%42
1451
21st to endDay
58%10%16%11%5%1
1584
February1st to 10thDay
62%11%12%11%3
1525
11th to 20thDay
61%11%10%11%6%
1714
21st to endDay
61%12%10%11%5%1
1480
March1st to 10thDay
60%12%12%11%5%
1800
11th to 20thDay
58%10%13%16%3
1834
21st to endDay
66%11%11%11%1
2376
April1st to 10thDay
59%10%13%15%3
2160
11th to 20thDay
52%10%14%14%9%1
2135
21st to endDay
52%9%11%17%10%
2340
May1st to 10thDay
41%11%16%24%9%
2421
11th to 20thDay
47%11%15%19%8%1
2480
21st to endDay
50%12%15%18%6%
2724
June1st to 10thDay
47%10%14%22%7%
2520
11th to 20thDay
41%9%15%21%12%2
2520
21st to endDay
23%6%12%34%20%6%
2520
July1st to 10thDay
16%5%13%21%29%16%
2451
11th to 20thDay
14%410%14%32%25%
2445
21st to endDay
10%47%14%41%24%
2589
August1st to 10thDay
17%5%10%19%36%14%
2490
11th to 20thDay
14%5%9%25%32%15%
2304
21st to endDay
19%5%10%26%29%11%
2376
September1st to 10thDay
17%411%24%28%15%
2160
11th to 20thDay
27%7%12%20%22%12%
2070
21st to endDay
31%8%12%24%20%5%
1980
October1st to 10thDay
40%7%10%22%18%3
1902
11th to 20thDay
39%9%13%23%14%1
1742
21st to endDay
51%8%11%19%10%
1782
November1st to 10thDay
56%9%12%16%6%1
1674
11th to 20thDay
60%12%13%11%3
1676
21st to endDay
53%12%13%13%8%1
1520
December1st to 10thDay
57%11%14%12%5%1
1520
11th to 20thDay
57%15%15%11%2
1928
21st to endDay
53%13%19%13%3
2794
January1st to 10thNight
62%12%11%12%21
2646
11th to 20thNight
58%9%11%15%6%1
2548
21st to endNight
57%10%13%14%5%1
2772
February1st to 10thNight
61%10%13%12%3
2434
11th to 20thNight
56%9%14%14%6%
2144
21st to endNight
61%9%10%14%5%1
1776
March1st to 10thNight
54%9%14%17%6%1
2160
11th to 20thNight
51%11%15%18%4
2123
21st to endNight
58%12%16%13%1
1980
April1st to 10thNight
54%10%14%17%4
1800
11th to 20thNight
48%9%15%17%10%1
1775
21st to endNight
44%11%15%18%11%1
1620
May1st to 10thNight
35%11%16%26%12%
1535
11th to 20thNight
38%12%18%23%8%1
1416
21st to endNight
43%11%17%21%7%
1552
June1st to 10thNight
39%12%13%27%9%1
1440
11th to 20thNight
37%10%14%27%10%2
1440
21st to endNight
23%7%14%29%21%5%
1440
July1st to 10thNight
15%6%10%23%29%17%
1400
11th to 20thNight
11%411%22%26%26%
1392
21st to endNight
9%36%19%35%27%
1488
August1st to 10thNight
13%411%24%32%15%
1424
11th to 20thNight
13%6%8%23%33%16%
1593
21st to endNight
16%5%10%28%30%12%
1980
September1st to 10thNight
16%410%27%27%16%
1800
11th to 20thNight
25%7%11%22%24%11%
1890
21st to endNight
29%7%12%27%18%8%
1980
October1st to 10thNight
37%8%11%23%19%3
2056
11th to 20thNight
40%9%10%21%17%2
2217
21st to endNight
45%11%11%18%14%1
2574
November1st to 10thNight
52%11%13%17%6%2
2405
11th to 20thNight
56%10%14%15%4
2503
21st to endNight
51%9%12%17%10%1
2660
December1st to 10thNight
55%13%14%14%31
2660
11th to 20thNight
60%12%13%13%2
3276
21st to endNight
55%11%20%10%4
4862

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
14%29%28%16%9%3
180
11th to 20thDay
18%20%36%13%9%4
163
21st to endDay
16%19%34%20%9%1
176
February1st to 10thDay
18%27%36%13%5%
245
11th to 20thDay
21%27%28%19%5%
395
21st to endDay
21%22%31%20%5%1
346
March1st to 10thDay
18%26%35%16%4
420
11th to 20thDay
16%22%30%22%8%
420
21st to endDay
21%26%31%16%6%
462
April1st to 10thDay
19%24%28%18%7%3
420
11th to 20thDay
19%25%29%15%8%3
412
21st to endDay
16%20%30%24%9%1
420
May1st to 10thDay
13%15%33%27%9%2
423
11th to 20thDay
19%13%28%23%12%4
448
21st to endDay
13%15%23%29%15%5%
485
June1st to 10thDay
16%15%23%26%14%6%
450
11th to 20thDay
14%18%31%26%9%3
450
21st to endDay
410%32%32%17%5%
450
July1st to 10thDay
29%30%35%20%4
446
11th to 20thDay
212%34%32%17%3
444
21st to endDay
19%32%31%20%7%
487
August1st to 10thDay
47%30%32%19%7%
447
11th to 20thDay
37%22%36%22%11%
437
21st to endDay
5%14%27%30%17%6%
495
September1st to 10thDay
413%25%28%21%8%
450
11th to 20thDay
9%11%26%30%18%6%
450
21st to endDay
10%11%27%31%17%4
450
October1st to 10thDay
11%14%31%23%19%3
450
11th to 20thDay
11%18%27%24%16%5%
392
21st to endDay
15%22%25%25%9%4
297
November1st to 10thDay
21%17%31%25%7%
270
11th to 20thDay
15%22%26%26%10%1
254
21st to endDay
17%13%33%27%9%
180
December1st to 10thDay
15%20%32%18%11%4
180
11th to 20thDay
19%32%31%15%21
180
21st to endDay
13%29%26%24%6%2
198
January1st to 10thNight
18%18%30%20%12%1
760
11th to 20thNight
18%17%25%26%12%2
728
21st to endNight
15%15%23%31%15%1
792
February1st to 10thNight
19%17%26%29%7%2
720
11th to 20thNight
16%16%23%32%12%1
704
21st to endNight
17%20%26%23%11%2
592
March1st to 10thNight
16%18%24%30%11%1
720
11th to 20thNight
13%16%26%30%14%1
720
21st to endNight
18%15%28%28%10%1
792
April1st to 10thNight
15%14%25%28%16%2
720
11th to 20thNight
14%15%26%26%16%2
707
21st to endNight
11%13%24%35%16%1
540
May1st to 10thNight
9%11%23%36%19%2
455
11th to 20thNight
13%6%13%30%33%4
354
21st to endNight
14%8%15%34%28%2
389
June1st to 10thNight
13%9%15%35%26%3
360
11th to 20thNight
13%8%21%37%21%1
360
21st to endNight
5%416%43%31%2
360
July1st to 10thNight
3312%44%36%3
350
11th to 20thNight
1313%53%30%1
348
21st to endNight
2210%47%35%4
394
August1st to 10thNight
3211%41%40%3
358
11th to 20thNight
2211%40%40%6%
525
21st to endNight
4318%39%32%4
792
September1st to 10thNight
5%314%42%31%4
720
11th to 20thNight
4413%36%35%7%
720
21st to endNight
10%5%18%37%26%5%
720
October1st to 10thNight
12%6%16%39%23%3
720
11th to 20thNight
13%10%18%32%22%5%
720
21st to endNight
15%10%21%33%16%4
792
November1st to 10thNight
19%14%27%31%9%1
740
11th to 20thNight
21%13%28%26%11%1
760
21st to endNight
13%17%27%27%13%3
760
December1st to 10thNight
15%16%27%29%11%2
760
11th to 20thNight
17%19%31%24%9%1
760
21st to endNight
19%23%28%24%5%1
836
Page generated at 2024-01-09 13:24:27. Version ac07

Copyright 2024 Attilla Danko


Elgin Clear Sky Chart |Charts Home