TIMPA
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the TIMPA clear sky chart from 2005-11-05 to 2017-12-04.

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
78%
15929
37%
47850
34%
15891
82%
15891
56%
22257

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
75%
718
34%
2327
36%
716
78%
716
53%
1055
January16th to endNight
71%
768
36%
2496
36%
768
78%
768
44%
1251
February1st to 15thNight
75%
700
37%
2187
37%
700
81%
700
53%
1022
February16th to endNight
69%
632
38%
1850
37%
632
75%
632
51%
925
March1st to 15thNight
71%
720
40%
1980
33%
720
78%
720
60%
956
March16th to endNight
74%
768
40%
2112
30%
768
83%
768
64%
991
April1st to 15thNight
70%
698
36%
1957
26%
698
77%
698
60%
919
April16th to endNight
74%
540
46%
1763
41%
540
83%
540
73%
646
May1st to 15thNight
75%
539
41%
1619
32%
539
83%
539
74%
641
May16th to endNight
79%
561
42%
1684
36%
561
83%
561
74%
665
June1st to 15thNight
82%
540
35%
1620
30%
540
84%
540
72%
661
June16th to endNight
87%
540
34%
1620
29%
540
87%
540
66%
699
July1st to 15thNight
83%
510
22%
1530
19%
510
83%
510
43%
818
July16th to endNight
83%
564
21%
1593
18%
531
83%
531
36%
925
August1st to 15thNight
86%
539
28%
1611
26%
536
86%
536
50%
805
August16th to endNight
86%
624
33%
1887
32%
624
86%
624
45%
996
September1st to 15thNight
80%
720
31%
1980
27%
720
81%
720
46%
1108
September16th to endNight
82%
716
46%
1980
36%
716
87%
716
71%
877
October1st to 15thNight
83%
720
41%
2079
35%
720
87%
720
69%
899
October16th to endNight
88%
768
47%
2304
43%
768
91%
768
72%
939
November1st to 15thNight
83%
760
43%
2280
39%
760
87%
760
66%
978
November16th to endNight
76%
780
42%
2503
40%
780
81%
780
55%
1125
December1st to 15thNight
73%
736
38%
2392
40%
736
76%
736
50%
1106
December16th to endNight
69%
768
36%
2496
37%
768
74%
768
43%
1250

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
3212323346%68%
48641
Night
3212213336%69%
48046
TransparencyDay
18%3411%23%39%
48336
Night
16%25%12%24%37%
47852
SeeingDay
5%5%18%32%25%12%
5693
Night
4111%41%36%5%
15938

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 15thDay
423214336%66%
1611
16th to endDay
5%313323336%63%
1728
February1st to 15thDay
5%31221213470%
1674
16th to endDay
7%312312245%65%
1624
March1st to 15thDay
322212345%69%
1980
16th to endDay
211213225%74%
2112
April1st to 15thDay
211212335%74%
1990
16th to endDay
11111112483%
2193
May1st to 15thDay
1121123480%
2331
16th to endDay
1111212285%
2429
June1st to 15thDay
2111112482%
2340
16th to endDay
21221223475%
2340
July1st to 15thDay
32135%46%6%7%10%47%
2340
16th to endDay
6%426%6%5%7%6%9%10%34%
2467
August1st to 15thDay
5%3246%36%5%7%7%47%
2340
16th to endDay
32145%36%6%6%6%52%
2310
September1st to 15thDay
5%3133246%5%7%55%
1980
16th to endDay
31122223475%
1980
October1st to 15thDay
111122225%77%
1881
16th to endDay
111223480%
1920
November1st to 15thDay
111111336%76%
1909
16th to endDay
311122224473%
1785
December1st to 15thDay
6%212323246%65%
1649
16th to endDay
6%213223247%64%
1728
January1st to 15thNight
5%2221233470%
2327
16th to endNight
5%214324435%62%
2496
February1st to 15thNight
3212312235%68%
2176
16th to endNight
5%312223445%64%
1850
March1st to 15thNight
4111213335%71%
1980
16th to endNight
22121223475%
2112
April1st to 15thNight
312213335%72%
1957
16th to endNight
21111286%
1763
May1st to 15thNight
112335%79%
1619
16th to endNight
1111111385%
1684
June1st to 15thNight
112222381%
1620
16th to endNight
111211222477%
1620
July1st to 15thNight
22143345%7%11%52%
1620
16th to endNight
32145%46%7%9%15%39%
1701
August1st to 15thNight
2134235%6%10%58%
1620
16th to endNight
32124245%6%10%55%
1887
September1st to 15thNight
421442445%8%57%
1980
16th to endNight
11111112479%
1980
October1st to 15thNight
11111223379%
2079
16th to endNight
11111122481%
2304
November1st to 15thNight
111212236%75%
2280
16th to endNight
422212335%70%
2503
December1st to 15thNight
6%312212246%66%
2392
16th to endNight
6%313413245%62%
2496

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
19%2413%26%32%
1612
16th to endDay
22%2314%24%30%
1728
February1st to 15thDay
19%1312%27%35%
1674
16th to endDay
22%1313%30%28%
1624
March1st to 15thDay
16%235%29%41%
1980
16th to endDay
14%227%28%44%
2112
April1st to 15thDay
13%115%33%44%
1990
16th to endDay
9%116%22%59%
2193
May1st to 15thDay
9%116%20%60%
2331
16th to endDay
8%115%22%60%
2432
June1st to 15thDay
9%217%68%
2340
16th to endDay
13%22413%63%
2340
July1st to 15thDay
28%6%12%15%15%22%
2201
16th to endDay
38%9%16%20%11%3
2312
August1st to 15thDay
32%6%10%15%17%17%
2325
16th to endDay
28%7%9%17%18%18%
2310
September1st to 15thDay
25%6%7%19%18%23%
1980
16th to endDay
14%127%30%43%
1980
October1st to 15thDay
11%249%26%45%
1881
16th to endDay
9%138%24%52%
1920
November1st to 15thDay
11%1211%33%39%
1909
16th to endDay
15%229%28%41%
1785
December1st to 15thDay
21%2415%31%25%
1649
16th to endDay
20%35%18%32%18%
1728
January1st to 15thNight
18%25%13%26%32%
2327
16th to endNight
24%3413%29%25%
2496
February1st to 15thNight
19%2315%24%34%
2187
16th to endNight
21%2313%31%28%
1850
March1st to 15thNight
16%229%25%43%
1980
16th to endNight
13%2210%29%41%
2112
April1st to 15thNight
15%127%31%40%
1957
16th to endNight
7%6%23%60%
1763
May1st to 15thNight
7%228%23%56%
1620
16th to endNight
8%115%21%62%
1685
June1st to 15thNight
9%12317%65%
1620
16th to endNight
12%12315%64%
1620
July1st to 15thNight
22%7%13%15%16%23%
1530
16th to endNight
27%9%21%23%13%3
1593
August1st to 15thNight
18%5%15%21%17%19%
1611
16th to endNight
22%6%10%21%20%18%
1887
September1st to 15thNight
24%5%7%22%19%20%
1980
16th to endNight
11%1210%32%41%
1980
October1st to 15thNight
11%2313%24%46%
2079
16th to endNight
9%1210%23%51%
2304
November1st to 15thNight
11%2311%32%37%
2280
16th to endNight
17%2210%25%41%
2503
December1st to 15thNight
20%2317%29%27%
2392
16th to endNight
25%25%17%28%19%
2496

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
13%320%38%21%3
90
16th to endDay
4413%36%31%10%
96
February1st to 15thDay
5%8%14%40%27%2
189
16th to endDay
8%11%31%28%15%4
238
March1st to 15thDay
5%11%27%27%18%9%
270
16th to endDay
311%31%25%18%10%
288
April1st to 15thDay
5%13%30%24%17%9%
269
16th to endDay
117%31%30%13%5%
270
May1st to 15thDay
312%31%31%12%7%
288
16th to endDay
16%27%36%22%5%
330
June1st to 15thDay
5%123%40%17%10%
315
16th to endDay
312%41%26%15%
315
July1st to 15thDay
5%16%32%37%16%
305
16th to endDay
6%17%27%30%27%
327
August1st to 15thDay
7%5%26%39%19%
315
16th to endDay
415%28%36%23%
332
September1st to 15thDay
9%13%33%29%12%
315
16th to endDay
5%220%36%24%10%
315
October1st to 15thDay
1422%33%25%13%
216
16th to endDay
26%29%45%16%
144
November1st to 15thDay
25%10%34%36%9%
135
16th to endDay
4316%34%30%10%
135
December1st to 15thDay
316%33%50%7%
100
16th to endDay
12%220%36%25%3
96
January1st to 15thNight
6%111%48%27%4
720
16th to endNight
8%113%45%26%4
768
February1st to 15thNight
5%211%46%28%5%
704
16th to endNight
6%217%51%19%2
632
March1st to 15thNight
4218%43%27%3
720
16th to endNight
2215%45%29%4
768
April1st to 15thNight
4418%49%22%1
698
16th to endNight
2318%51%21%2
540
May1st to 15thNight
319%47%26%2
540
16th to endNight
1214%48%30%1
563
June1st to 15thNight
1111%50%33%2
540
16th to endNight
26%38%50%1
540
July1st to 15thNight
35%25%59%6%
510
16th to endNight
4318%59%14%
564
August1st to 15thNight
3217%62%13%
539
16th to endNight
3321%61%10%
624
September1st to 15thNight
41428%50%10%
720
16th to endNight
29%38%42%6%
716
October1st to 15thNight
119%44%38%4
720
16th to endNight
16%42%40%7%
768
November1st to 15thNight
39%44%37%4
760
16th to endNight
5%112%41%33%5%
780
December1st to 15thNight
8%29%44%31%4
736
16th to endNight
8%211%49%23%4
768
Page generated at 2017-12-05 08:18:57. Version ac04

Copyright 2017 A. Danko


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