TIMPA
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the TIMPA clear sky chart from 2005-11-06 to 2024-02-20.

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
74%
24143
37%
79285
32%
24066
80%
24066
52%
36131

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
68%
749
41%
3978
33%
736
76%
736
38%
1440
January11th to 20thNight
72%
747
48%
3874
37%
740
80%
740
48%
1206
January21st to endNight
64%
827
24%
4284
33%
814
73%
814
26%
2153
February1st to 10thNight
68%
760
37%
2398
35%
760
77%
760
50%
1149
February11th to 20thNight
63%
738
35%
2212
30%
738
73%
738
48%
1114
February21st to endNight
62%
592
39%
1707
32%
592
72%
592
53%
842
March1st to 10thNight
61%
720
38%
1980
27%
720
73%
720
55%
1000
March11th to 20thNight
69%
720
39%
1980
30%
720
77%
720
60%
966
March21st to endNight
69%
792
39%
2178
27%
792
79%
792
58%
1070
April1st to 10thNight
72%
720
39%
1980
26%
720
81%
720
67%
896
April11th to 20thNight
66%
592
41%
1836
33%
592
76%
592
64%
754
April21st to endNight
72%
540
47%
1745
40%
540
82%
540
74%
642
May1st to 10thNight
73%
540
43%
1620
34%
540
81%
540
71%
646
May11th to 20thNight
77%
531
43%
1594
36%
531
82%
531
73%
641
May21st to endNight
77%
582
44%
1746
36%
582
82%
582
80%
662
June1st to 10thNight
81%
540
38%
1620
31%
540
83%
540
70%
675
June11th to 20thNight
83%
540
40%
1620
32%
540
86%
540
80%
625
June21st to endNight
84%
540
32%
1620
27%
540
86%
540
61%
734
July1st to 10thNight
83%
525
24%
1575
21%
525
83%
525
46%
821
July11th to 20thNight
83%
522
21%
1566
18%
522
83%
522
36%
897
July21st to endNight
78%
591
18%
1674
16%
558
77%
558
31%
1024
August1st to 10thNight
86%
537
27%
1602
25%
534
86%
534
50%
810
August11th to 20thNight
81%
534
32%
1602
29%
534
81%
534
44%
843
August21st to endNight
84%
669
31%
2032
30%
669
85%
669
46%
1063
September1st to 10thNight
80%
720
32%
1980
29%
720
80%
720
47%
1099
September11th to 20thNight
84%
720
41%
1980
35%
720
86%
720
61%
962
September21st to endNight
79%
720
40%
1980
30%
720
84%
720
62%
947
October1st to 10thNight
80%
720
41%
2036
33%
720
85%
720
63%
942
October11th to 20thNight
82%
720
45%
2160
37%
720
89%
720
72%
879
October21st to endNight
82%
792
46%
2376
40%
792
87%
792
74%
949
November1st to 10thNight
80%
740
45%
2220
40%
740
85%
740
67%
934
November11th to 20thNight
79%
760
44%
2327
38%
760
85%
760
65%
993
November21st to endNight
67%
760
38%
2470
35%
760
74%
760
49%
1167
December1st to 10thNight
70%
760
39%
2470
38%
760
75%
760
50%
1147
December11th to 20thNight
64%
758
34%
2933
35%
758
72%
758
36%
1525
December21st to endNight
65%
825
24%
4330
35%
817
71%
817
30%
1914

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
4213323346%67%
78873
Night
4313323446%68%
80382
TransparencyDay
18%45%11%24%38%
78600
Night
18%35%13%26%35%
80177
SeeingDay
5%5%18%32%27%13%
13946
Night
4214%44%32%4
24195

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
6%324323336%66%
2858
11th to 20thDay
3213434335%68%
2860
21st to endDay
7%42332445%9%56%
3146
February1st to 10thDay
5%323223246%69%
1779
11th to 20thDay
8%32343434464%
1841
21st to endDay
7%313312335%68%
1547
March1st to 10thDay
431332345%6%65%
1980
11th to 20thDay
4312323345%68%
1980
21st to endDay
3213323335%73%
2178
April1st to 10thDay
2111223346%76%
1980
11th to 20thDay
221111222481%
2070
21st to endDay
1112112235%82%
2210
May1st to 10thDay
11121233481%
2340
11th to 20thDay
111221223480%
2301
21st to endDay
11111122388%
2530
June1st to 10thDay
2111212236%79%
2340
11th to 20thDay
11221112386%
2340
21st to endDay
321332435%5%71%
2340
July1st to 10thDay
32135%35%5%6%9%56%
2340
11th to 20thDay
4325%6%46%7%10%12%40%
2340
21st to endDay
7%436%6%5%7%6%9%12%34%
2545
August1st to 10thDay
5%4245%36%5%7%7%51%
2328
11th to 20thDay
33146%36%6%10%9%49%
2299
21st to endDay
32245%46%6%6%7%54%
2316
September1st to 10thDay
6%4244245%5%6%59%
1980
11th to 20thDay
3212223446%73%
1980
21st to endDay
4212223445%72%
1980
October1st to 10thDay
212223446%74%
1922
11th to 20thDay
111121222384%
1800
21st to endDay
112212235%79%
1980
November1st to 10thDay
212212237%78%
1859
11th to 20thDay
2212223445%73%
1849
21st to endDay
422332335%7%66%
1710
December1st to 10thDay
6%21343446%6%63%
1710
11th to 20thDay
6%425%43436%7%54%
2169
21st to endDay
7%314434347%61%
3146
January1st to 10thNight
5%313323445%67%
4097
11th to 20thNight
3212212335%76%
4110
21st to endNight
11%5%14423437%55%
4521
February1st to 10thNight
5%412323345%67%
2398
11th to 20thNight
6%324323345%65%
2211
21st to endNight
6%31332335%5%67%
1707
March1st to 10thNight
4222323447%65%
1980
11th to 20thNight
4312312345%71%
1980
21st to endNight
3412323335%71%
2178
April1st to 10thNight
2112213336%75%
1980
11th to 20thNight
221221333380%
1836
21st to endNight
22111122484%
1745
May1st to 10thNight
111113335%80%
1620
11th to 20thNight
1111112335%80%
1594
21st to endNight
11111122388%
1746
June1st to 10thNight
2112213336%77%
1620
11th to 20thNight
111111122485%
1620
21st to endNight
2212223345%72%
1620
July1st to 10thNight
2324435%6%7%9%56%
1620
11th to 20thNight
2215%5%5%7%7%9%14%42%
1620
21st to endNight
4425%6%5%7%8%10%15%34%
1773
August1st to 10thNight
32143336%6%12%57%
1611
11th to 20thNight
33245%25%6%6%10%54%
1602
21st to endNight
43134246%8%11%53%
2032
September1st to 10thNight
5%3145%3445%9%57%
1980
11th to 20thNight
2213323335%73%
1980
21st to endNight
2213323345%73%
1980
October1st to 10thNight
2212222345%74%
2036
11th to 20thNight
211212235%80%
2160
21st to endNight
111111222483%
2376
November1st to 10thNight
2212212337%76%
2220
11th to 20thNight
2211223345%76%
2327
21st to endNight
6%313323446%65%
2470
December1st to 10thNight
6%312323346%66%
2470
11th to 20thNight
7%425%5%24346%57%
3041
21st to endNight
6%4144245%5%5%60%
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
21%3311%33%28%
2859
11th to 20thDay
20%3311%36%26%
2860
21st to endDay
25%48%16%30%18%
3146
February1st to 10thDay
20%2411%23%41%
1779
11th to 20thDay
25%2313%25%31%
1851
21st to endDay
20%2311%29%35%
1547
March1st to 10thDay
20%349%28%37%
1980
11th to 20thDay
19%239%24%43%
1980
21st to endDay
16%328%32%39%
2178
April1st to 10thDay
11%215%33%47%
1980
11th to 20thDay
10%215%23%58%
2073
21st to endDay
8%227%24%57%
2210
May1st to 10thDay
9%216%20%61%
2340
11th to 20thDay
10%228%20%58%
2304
21st to endDay
6%11320%68%
2530
June1st to 10thDay
9%11421%64%
2340
11th to 20thDay
7%11212%77%
2340
21st to endDay
16%346%16%55%
2340
July1st to 10thDay
24%5%9%13%17%32%
2276
11th to 20thDay
30%9%16%22%15%8%
2271
21st to endDay
37%10%15%21%13%5%
2404
August1st to 10thDay
29%7%10%16%17%20%
2313
11th to 20thDay
25%8%14%17%20%16%
2299
21st to endDay
25%7%10%19%20%18%
2316
September1st to 10thDay
25%6%6%18%19%26%
1980
11th to 20thDay
13%3411%25%43%
1980
21st to endDay
15%349%27%42%
1980
October1st to 10thDay
11%45%13%26%41%
1922
11th to 20thDay
8%227%26%55%
1800
21st to endDay
11%239%24%51%
1980
November1st to 10thDay
10%2210%35%41%
1859
11th to 20thDay
14%3210%27%44%
1849
21st to endDay
20%3412%26%36%
1710
December1st to 10thDay
22%4414%28%29%
1710
11th to 20thDay
28%45%17%25%22%
2168
21st to endDay
23%45%16%32%19%
3146
January1st to 10thNight
18%3412%38%24%
4097
11th to 20thNight
12%2316%42%24%
4110
21st to endNight
30%5%7%15%29%14%
4521
February1st to 10thNight
20%3412%22%39%
2398
11th to 20thNight
23%2414%27%30%
2212
21st to endNight
19%3410%29%35%
1707
March1st to 10thNight
19%4311%27%36%
1980
11th to 20thNight
16%3311%23%45%
1980
21st to endNight
16%3211%32%35%
2178
April1st to 10thNight
12%229%31%45%
1980
11th to 20thNight
12%227%23%55%
1836
21st to endNight
8%127%25%57%
1745
May1st to 10thNight
9%228%22%57%
1620
11th to 20thNight
8%238%20%58%
1595
21st to endNight
6%11421%68%
1746
June1st to 10thNight
10%225%19%61%
1620
11th to 20thNight
6%12314%75%
1620
21st to endNight
15%345%15%58%
1620
July1st to 10thNight
21%7%10%12%15%34%
1575
11th to 20thNight
27%10%17%23%16%8%
1566
21st to endNight
32%10%22%19%13%5%
1674
August1st to 10thNight
19%7%14%21%18%22%
1602
11th to 20thNight
24%6%14%22%18%17%
1602
21st to endNight
22%7%11%21%22%17%
2032
September1st to 10thNight
24%5%8%21%18%24%
1980
11th to 20thNight
15%4412%28%38%
1980
21st to endNight
15%3411%27%41%
1980
October1st to 10thNight
13%4415%23%42%
2036
11th to 20thNight
9%2210%24%53%
2160
21st to endNight
8%239%26%52%
2376
November1st to 10thNight
11%2210%32%42%
2220
11th to 20thNight
12%3310%30%42%
2327
21st to endNight
21%3312%27%34%
2470
December1st to 10thNight
20%3418%24%31%
2470
11th to 20thNight
29%3416%26%22%
3041
21st to endNight
25%45%16%28%21%
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%5%24%35%26%2
270
11th to 20thDay
10%217%41%23%7%
270
21st to endDay
45%19%41%26%5%
297
February1st to 10thDay
6%6%25%34%22%6%
339
11th to 20thDay
11%10%26%35%17%1
452
21st to endDay
10%13%29%33%12%2
346
March1st to 10thDay
7%12%27%35%15%3
420
11th to 20thDay
5%10%31%26%19%9%
420
21st to endDay
6%12%31%30%15%6%
462
April1st to 10thDay
410%28%27%22%10%
420
11th to 20thDay
212%29%30%21%6%
412
21st to endDay
211%26%30%19%11%
420
May1st to 10thDay
29%28%31%18%11%
423
11th to 20thDay
2426%34%25%8%
448
21st to endDay
16%26%32%26%8%
485
June1st to 10thDay
4217%38%26%13%
450
11th to 20thDay
1318%36%30%13%
450
21st to endDay
4113%35%34%13%
450
July1st to 10thDay
226%28%38%23%
446
11th to 20thDay
5%15%24%34%31%
444
21st to endDay
6%2417%38%33%
487
August1st to 10thDay
6%1423%40%27%
447
11th to 20thDay
5%1422%40%28%
437
21st to endDay
21422%37%33%
495
September1st to 10thDay
8%210%29%31%20%
450
11th to 20thDay
3110%35%34%18%
450
21st to endDay
4415%32%29%16%
450
October1st to 10thDay
2421%32%28%13%
392
11th to 20thDay
3115%34%33%15%
270
21st to endDay
2214%35%33%15%
297
November1st to 10thDay
45%16%39%26%10%
270
11th to 20thDay
3316%39%30%9%
270
21st to endDay
4423%40%21%7%
270
December1st to 10thDay
7%216%37%32%6%
270
11th to 20thDay
7%420%40%25%4
270
21st to endDay
10%5%23%33%23%6%
297
January1st to 10thNight
7%216%50%22%3
760
11th to 20thNight
6%215%46%27%4
760
21st to endNight
9%318%46%21%3
836
February1st to 10thNight
7%318%44%23%5%
760
11th to 20thNight
6%5%19%51%17%1
742
21st to endNight
7%423%48%16%2
592
March1st to 10thNight
5%325%48%17%1
720
11th to 20thNight
5%319%41%27%5%
720
21st to endNight
4419%48%23%2
792
April1st to 10thNight
2320%52%21%2
720
11th to 20thNight
3423%50%19%1
592
21st to endNight
3221%53%18%2
540
May1st to 10thNight
2321%52%21%1
540
11th to 20thNight
1217%55%24%2
531
21st to endNight
1317%52%26%1
584
June1st to 10thNight
2112%52%32%1
540
11th to 20thNight
1112%52%31%2
540
21st to endNight
218%42%45%2
540
July1st to 10thNight
316%32%54%4
525
11th to 20thNight
2425%62%7%
522
21st to endNight
5%1321%56%14%
591
August1st to 10thNight
31122%61%12%
537
11th to 20thNight
41424%61%7%
534
21st to endNight
41321%61%10%
669
September1st to 10thNight
5%1429%52%8%
720
11th to 20thNight
316%38%45%7%
720
21st to endNight
2111%41%40%5%
720
October1st to 10thNight
3111%48%34%3
720
11th to 20thNight
2212%48%33%3
720
21st to endNight
2112%46%32%7%
792
November1st to 10thNight
3111%48%32%4
740
11th to 20thNight
314%46%33%3
760
21st to endNight
7%219%46%23%3
760
December1st to 10thNight
8%214%47%26%3
760
11th to 20thNight
8%317%49%21%2
760
21st to endNight
8%317%48%21%4
836
Page generated at 2024-02-17 04:28:41. Version ac07

Copyright 2024 Attilla Danko


TIMPA Clear Sky Chart |Charts Home