The Sky's The Limit Observatory and Nature Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the The Sky's The Limit Observatory and Nature Center clear sky chart from 2005-11-06 to 2024-03-01.

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
71%
24889
39%
79349
31%
24803
80%
24803
61%
33041

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
63%
756
42%
3973
28%
736
75%
736
43%
1230
January11th to 20thNight
65%
750
43%
3945
32%
740
78%
740
40%
1376
January21st to endNight
54%
827
28%
3903
26%
814
73%
814
33%
1704
February1st to 10thNight
59%
760
39%
2280
29%
760
74%
760
52%
1054
February11th to 20thNight
58%
740
41%
2218
30%
740
74%
740
55%
1009
February21st to endNight
53%
628
37%
1884
30%
628
67%
628
50%
874
March1st to 10thNight
56%
722
34%
2165
26%
722
71%
722
52%
992
March11th to 20thNight
62%
720
39%
2022
28%
720
76%
720
62%
907
March21st to endNight
59%
792
39%
2152
23%
792
73%
792
58%
991
April1st to 10thNight
58%
720
39%
1800
19%
720
69%
720
61%
888
April11th to 20thNight
57%
711
42%
1779
19%
711
69%
711
69%
829
April21st to endNight
65%
687
45%
1767
22%
687
76%
687
77%
755
May1st to 10thNight
66%
540
45%
1620
29%
540
74%
540
77%
607
May11th to 20thNight
72%
531
44%
1595
31%
531
78%
531
76%
610
May21st to endNight
69%
583
42%
1746
29%
582
76%
582
80%
646
June1st to 10thNight
79%
540
38%
1620
31%
540
82%
540
80%
608
June11th to 20thNight
78%
540
40%
1620
33%
540
82%
540
83%
599
June21st to endNight
80%
540
37%
1620
31%
540
83%
540
77%
632
July1st to 10thNight
91%
525
37%
1575
32%
525
91%
525
79%
606
July11th to 20thNight
87%
522
35%
1566
30%
522
87%
522
66%
666
July21st to endNight
86%
591
36%
1674
30%
558
86%
558
56%
785
August1st to 10thNight
88%
667
37%
1732
24%
664
89%
664
73%
791
August11th to 20thNight
93%
712
41%
1780
26%
712
94%
712
79%
810
August21st to endNight
90%
792
44%
1980
31%
792
91%
792
77%
910
September1st to 10thNight
90%
720
41%
1861
33%
720
91%
720
76%
843
September11th to 20thNight
89%
720
49%
1980
41%
720
94%
720
87%
773
September21st to endNight
86%
720
47%
1980
39%
720
92%
720
82%
803
October1st to 10thNight
76%
720
44%
1980
34%
720
85%
720
73%
855
October11th to 20thNight
80%
720
51%
1980
43%
720
88%
720
81%
804
October21st to endNight
78%
792
45%
2479
41%
792
88%
792
76%
917
November1st to 10thNight
74%
740
42%
2405
37%
740
86%
740
69%
912
November11th to 20thNight
77%
760
43%
2470
40%
760
87%
760
68%
964
November21st to endNight
68%
760
40%
2470
36%
760
78%
760
56%
1055
December1st to 10thNight
67%
760
37%
2470
32%
760
77%
760
52%
1112
December11th to 20thNight
62%
758
36%
2890
29%
758
74%
758
40%
1318
December21st to endNight
57%
823
24%
4368
30%
817
70%
817
31%
1806

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
2212223346%75%
79037
Night
1112213346%76%
80454
TransparencyDay
11%35%13%26%41%
78764
Night
11%46%14%27%38%
80249
SeeingDay
410%21%34%23%8%
14557
Night
25%18%35%32%7%
24932

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
2312322345%73%
2858
11th to 20thDay
2212223448%70%
2860
21st to endDay
431343446%8%60%
3466
February1st to 10thDay
3322223346%72%
1900
11th to 20thDay
2112214347%71%
1850
21st to endDay
12123235%46%70%
1570
March1st to 10thDay
22222345%9%69%
1801
11th to 20thDay
2212222446%73%
1935
21st to endDay
1111223346%77%
2200
April1st to 10thDay
2212323346%73%
2160
11th to 20thDay
1111112236%82%
2129
21st to endDay
111112235%84%
2191
May1st to 10thDay
111112235%81%
2340
11th to 20thDay
1111112487%
2301
21st to endDay
11121122485%
2530
June1st to 10thDay
11111223485%
2340
11th to 20thDay
11112489%
2340
21st to endDay
111221122384%
2340
July1st to 10thDay
2112212245%78%
2340
11th to 20thDay
2212222346%73%
2340
21st to endDay
3314435%46%7%61%
2545
August1st to 10thDay
2212213346%76%
2194
11th to 20thDay
211221345%5%74%
2122
21st to endDay
1111213346%76%
2376
September1st to 10thDay
2111222446%75%
2098
11th to 20thDay
1112389%
1980
21st to endDay
11111223383%
1980
October1st to 10thDay
1112213435%78%
1980
11th to 20thDay
1111222486%
1980
21st to endDay
1121322485%
1872
November1st to 10thDay
1111212327%80%
1674
11th to 20thDay
11222235%7%75%
1710
21st to endDay
111221335%7%73%
1710
December1st to 10thDay
321243345%7%65%
1710
11th to 20thDay
2223325%5%6%10%60%
2169
21st to endDay
5%3133245%7%9%59%
3146
January1st to 10thNight
111222335%7%73%
4097
11th to 20thNight
221222346%8%70%
4110
21st to endNight
43123245%5%7%64%
4209
February1st to 10thNight
3312223346%70%
2280
11th to 20thNight
221221335%6%72%
2218
21st to endNight
121333445%7%69%
1884
March1st to 10thNight
221232345%8%69%
2165
11th to 20thNight
2112312346%74%
2022
21st to endNight
11222335%6%75%
2152
April1st to 10thNight
1113323337%74%
1800
11th to 20thNight
11221232482%
1779
21st to endNight
111111237%82%
1767
May1st to 10thNight
1111135%86%
1620
11th to 20thNight
11212125%86%
1594
21st to endNight
111113488%
1746
June1st to 10thNight
111222487%
1620
11th to 20thNight
111112290%
1620
21st to endNight
11111222287%
1620
July1st to 10thNight
11111223484%
1620
11th to 20thNight
1112312336%75%
1620
21st to endNight
322332335%6%68%
1773
August1st to 10thNight
21121233480%
1741
11th to 20thNight
111112246%81%
1780
21st to endNight
112211245%81%
1980
September1st to 10thNight
1111112245%80%
1861
11th to 20thNight
111112291%
1980
21st to endNight
1111222388%
1980
October1st to 10thNight
112212235%80%
1980
11th to 20thNight
111111112388%
1980
21st to endNight
1112235%85%
2479
November1st to 10thNight
11113235%82%
2405
11th to 20thNight
1111113345%79%
2470
21st to endNight
221222335%6%73%
2470
December1st to 10thNight
331231345%7%68%
2470
11th to 20thNight
221332446%9%63%
3041
21st to endNight
32123345%6%9%62%
4521

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
15%46%17%42%17%
2859
11th to 20thDay
15%6%9%28%26%15%
2860
21st to endDay
20%7%10%18%31%14%
3466
February1st to 10thDay
16%46%15%29%31%
1900
11th to 20thDay
13%45%17%30%32%
1860
21st to endDay
15%5%7%17%28%28%
1570
March1st to 10thDay
14%36%17%30%30%
1801
11th to 20thDay
12%47%16%31%30%
1935
21st to endDay
10%36%21%34%27%
2200
April1st to 10thDay
14%35%15%32%31%
2160
11th to 20thDay
7%2411%32%45%
2132
21st to endDay
6%2414%33%42%
2191
May1st to 10thDay
8%2412%29%45%
2340
11th to 20thDay
6%128%30%53%
2304
21st to endDay
6%1410%29%50%
2530
June1st to 10thDay
7%227%23%60%
2340
11th to 20thDay
3126%15%73%
2340
21st to endDay
9%12310%75%
2340
July1st to 10thDay
10%247%14%63%
2276
11th to 20thDay
12%36%14%23%41%
2271
21st to endDay
19%6%8%15%21%31%
2404
August1st to 10thDay
11%36%8%21%52%
2179
11th to 20thDay
10%45%12%22%47%
2122
21st to endDay
10%35%9%23%50%
2376
September1st to 10thDay
11%47%9%14%55%
2098
11th to 20thDay
4125%20%67%
1980
21st to endDay
7%238%22%58%
1980
October1st to 10thDay
10%249%25%49%
1980
11th to 20thDay
5%149%24%56%
1980
21st to endDay
8%149%22%56%
1872
November1st to 10thDay
9%25%13%31%41%
1674
11th to 20thDay
10%35%15%27%41%
1710
21st to endDay
12%36%16%30%33%
1710
December1st to 10thDay
19%47%19%25%27%
1710
11th to 20thDay
19%7%11%24%22%16%
2168
21st to endDay
21%6%12%23%25%13%
3146
January1st to 10thNight
10%6%8%16%37%22%
4097
11th to 20thNight
13%6%8%28%29%16%
4110
21st to endNight
19%6%10%19%30%16%
4209
February1st to 10thNight
16%46%15%25%34%
2280
11th to 20thNight
14%5%5%16%31%31%
2219
21st to endNight
15%5%6%17%29%28%
1884
March1st to 10thNight
15%47%19%30%26%
2165
11th to 20thNight
11%37%17%33%29%
2022
21st to endNight
11%47%16%35%27%
2152
April1st to 10thNight
13%36%18%32%28%
1800
11th to 20thNight
9%2412%31%42%
1779
21st to endNight
5%25%13%33%42%
1767
May1st to 10thNight
5%1415%33%43%
1620
11th to 20thNight
6%139%32%48%
1595
21st to endNight
41313%36%43%
1746
June1st to 10thNight
5%138%25%58%
1620
11th to 20thNight
4226%14%72%
1620
21st to endNight
7%115%11%74%
1620
July1st to 10thNight
6%227%15%68%
1575
11th to 20thNight
11%36%13%24%43%
1566
21st to endNight
15%5%7%18%24%30%
1674
August1st to 10thNight
9%35%10%19%54%
1732
11th to 20thNight
6%35%11%25%49%
1780
21st to endNight
9%2310%23%54%
1980
September1st to 10thNight
8%25%9%20%55%
1861
11th to 20thNight
3126%20%67%
1980
21st to endNight
5%237%21%62%
1980
October1st to 10thNight
9%25%9%30%45%
1980
11th to 20thNight
6%128%27%56%
1980
21st to endNight
6%25%9%20%58%
2479
November1st to 10thNight
8%3410%33%43%
2405
11th to 20thNight
9%3413%30%43%
2470
21st to endNight
14%36%13%30%33%
2470
December1st to 10thNight
16%5%7%18%24%30%
2470
11th to 20thNight
18%7%10%18%28%20%
3041
21st to endNight
18%8%10%23%27%14%
4521

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
7%12%29%34%16%3
270
11th to 20thDay
11%6%22%39%20%2
270
21st to endDay
7%18%27%29%15%3
487
February1st to 10thDay
8%17%27%28%17%3
460
11th to 20thDay
6%21%29%32%11%1
455
21st to endDay
9%21%33%23%14%
382
March1st to 10thDay
9%21%28%30%11%1
421
11th to 20thDay
7%15%29%32%16%2
420
21st to endDay
6%23%29%29%11%2
462
April1st to 10thDay
8%16%24%29%19%5%
420
11th to 20thDay
421%30%25%17%2
412
21st to endDay
418%25%28%18%6%
420
May1st to 10thDay
413%24%37%16%5%
423
11th to 20thDay
312%24%34%20%7%
448
21st to endDay
211%24%37%18%8%
485
June1st to 10thDay
28%21%35%24%10%
450
11th to 20thDay
15%23%31%30%10%
450
21st to endDay
3419%38%24%11%
450
July1st to 10thDay
2112%39%31%17%
446
11th to 20thDay
119%36%32%21%
444
21st to endDay
228%38%30%21%
487
August1st to 10thDay
213%38%30%16%
447
11th to 20thDay
3110%35%32%19%
437
21st to endDay
2110%33%35%20%
495
September1st to 10thDay
2214%41%31%10%
450
11th to 20thDay
1417%38%32%8%
450
21st to endDay
27%19%33%31%8%
450
October1st to 10thDay
29%21%36%26%5%
450
11th to 20thDay
15%22%40%29%3
450
21st to endDay
38%18%34%28%8%
319
November1st to 10thDay
38%21%34%30%4
270
11th to 20thDay
49%20%37%27%4
270
21st to endDay
210%26%32%23%7%
270
December1st to 10thDay
5%6%24%42%20%3
270
11th to 20thDay
411%23%36%23%3
270
21st to endDay
9%14%30%27%17%2
297
January1st to 10thNight
38%22%37%23%8%
760
11th to 20thNight
46%22%39%23%6%
760
21st to endNight
5%9%25%36%20%4
836
February1st to 10thNight
49%24%34%23%6%
760
11th to 20thNight
39%27%35%21%5%
744
21st to endNight
411%29%36%16%4
628
March1st to 10thNight
410%27%37%20%3
722
11th to 20thNight
310%23%31%25%9%
720
21st to endNight
213%23%37%21%5%
792
April1st to 10thNight
29%26%35%24%3
720
11th to 20thNight
39%29%31%23%5%
711
21st to endNight
18%24%35%26%6%
687
May1st to 10thNight
26%24%37%28%3
540
11th to 20thNight
7%18%36%34%4
531
21st to endNight
17%22%38%28%4
584
June1st to 10thNight
1315%45%33%3
540
11th to 20thNight
1218%42%35%3
540
21st to endNight
1115%35%42%5%
540
July1st to 10thNight
15%36%50%8%
525
11th to 20thNight
26%35%49%8%
522
21st to endNight
3434%52%6%
591
August1st to 10thNight
27%31%49%11%
667
11th to 20thNight
2323%58%14%
712
21st to endNight
21423%53%18%
792
September1st to 10thNight
115%29%51%13%
720
11th to 20thNight
118%36%44%11%
720
21st to endNight
1210%35%41%11%
720
October1st to 10thNight
1317%40%35%5%
720
11th to 20thNight
2313%38%35%9%
720
21st to endNight
15%14%35%33%13%
792
November1st to 10thNight
1419%35%32%9%
740
11th to 20thNight
2416%37%33%10%
760
21st to endNight
36%19%38%26%8%
760
December1st to 10thNight
4420%42%24%6%
760
11th to 20thNight
5%6%23%37%25%4
760
21st to endNight
6%10%23%37%19%5%
836
Page generated at 2024-02-27 03:30:16. Version ac07

Copyright © 2024 Attilla Danko.


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