Robastro Home Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Robastro Home Observatory clear sky chart from 2005-11-06 to 2024-01-13.

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
49%
23982
28%
74226
19%
23923
58%
23923
36%
41246

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
35%
948
31%
2458
12%
946
47%
946
38%
1471
January11th to 20thNight
34%
915
28%
2379
10%
915
45%
915
33%
1477
January21st to endNight
34%
990
31%
2574
12%
990
44%
990
35%
1586
February1st to 10thNight
31%
835
26%
2275
10%
835
40%
835
31%
1411
February11th to 20thNight
24%
704
23%
2098
9%
700
35%
700
28%
1282
February21st to endNight
21%
538
28%
1722
8%
538
38%
538
25%
1040
March1st to 10thNight
30%
540
25%
1980
12%
540
45%
540
24%
1155
March11th to 20thNight
31%
540
24%
1980
15%
540
43%
540
24%
1162
March21st to endNight
32%
594
26%
2178
14%
594
48%
594
27%
1200
April1st to 10thNight
32%
540
27%
1980
14%
540
51%
540
31%
1041
April11th to 20thNight
33%
533
24%
1837
15%
533
48%
533
28%
1044
April21st to endNight
35%
540
29%
1720
16%
540
53%
540
34%
948
May1st to 10thNight
38%
540
26%
1620
17%
540
51%
540
32%
958
May11th to 20thNight
46%
531
21%
1594
18%
531
54%
531
34%
943
May21st to endNight
51%
584
24%
1745
19%
582
61%
582
35%
1012
June1st to 10thNight
70%
540
24%
1620
24%
540
75%
540
45%
847
June11th to 20thNight
69%
540
27%
1620
27%
540
74%
540
52%
792
June21st to endNight
72%
540
27%
1620
28%
540
76%
540
46%
851
July1st to 10thNight
74%
525
23%
1575
25%
525
77%
525
41%
877
July11th to 20thNight
83%
522
33%
1566
38%
522
87%
522
64%
691
July21st to endNight
86%
591
31%
1673
36%
558
89%
558
54%
812
August1st to 10thNight
89%
537
36%
1601
41%
534
91%
534
67%
687
August11th to 20thNight
80%
534
32%
1600
36%
534
81%
534
43%
865
August21st to endNight
83%
594
27%
2018
33%
594
84%
594
43%
995
September1st to 10thNight
74%
540
25%
1980
30%
540
75%
540
38%
987
September11th to 20thNight
72%
540
26%
1980
30%
540
73%
540
33%
1051
September21st to endNight
75%
540
36%
1980
37%
540
79%
540
45%
900
October1st to 10thNight
71%
592
36%
2032
32%
592
76%
592
48%
936
October11th to 20thNight
53%
720
35%
2160
19%
720
64%
720
42%
1165
October21st to endNight
45%
792
33%
2376
20%
792
54%
792
38%
1317
November1st to 10thNight
51%
740
32%
2220
19%
740
61%
740
41%
1209
November11th to 20thNight
46%
834
31%
2354
16%
834
56%
834
40%
1316
November21st to endNight
35%
950
29%
2470
12%
950
46%
950
33%
1550
December1st to 10thNight
37%
950
32%
2470
14%
950
49%
950
36%
1518
December11th to 20thNight
35%
949
30%
2860
13%
948
44%
948
28%
1756
December21st to endNight
34%
1040
18%
4311
12%
1026
44%
1026
24%
2394

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
11%5%2443445%7%50%
74945
Night
11%424423447%55%
74830
TransparencyDay
33%5%10%23%21%7%
74670
Night
30%5%10%22%24%11%
74625
SeeingDay
12%7%22%28%23%7%
13994
Night
13%7%27%35%17%2
23990

By Month

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 10thDay
13%6%24412346%55%
1707
11th to 20thDay
15%6%24422336%51%
1643
21st to endDay
17%6%24322347%52%
1782
February1st to 10thDay
19%6%37%423335%45%
1700
11th to 20thDay
19%7%35%423345%44%
1749
21st to endDay
22%6%2442323449%
1534
March1st to 10thDay
18%7%2442435%7%44%
1980
11th to 20thDay
18%6%35%423446%44%
1980
21st to endDay
14%6%35%5%24445%47%
2178
April1st to 10thDay
14%6%25%5%345%5%6%45%
1980
11th to 20thDay
14%6%36%5%3445%7%44%
2070
21st to endDay
12%435%5%35%6%47%46%
2236
May1st to 10thDay
14%5%35%5%3445%7%45%
2340
11th to 20thDay
12%6%26%6%35%5%6%8%41%
2302
21st to endDay
10%7%36%7%35%7%7%9%35%
2531
June1st to 10thDay
6%325%5%36%5%6%10%50%
2340
11th to 20thDay
5%3245%35%5%7%8%52%
2340
21st to endDay
5%3245%35%46%9%54%
2340
July1st to 10thDay
6%5%26%7%47%7%7%11%39%
2340
11th to 20thDay
3223425%5%6%9%59%
2340
21st to endDay
4323435%7%9%11%50%
2546
August1st to 10thDay
2212325%46%11%62%
2328
11th to 20thDay
8%3245%345%7%9%50%
2301
21st to endDay
4415%5%36%6%6%11%48%
2332
September1st to 10thDay
7%4245%35%5%5%7%53%
1980
11th to 20thDay
10%435%6%46%45%7%47%
1980
21st to endDay
8%41343335%7%58%
1980
October1st to 10thDay
5%415%33435%6%60%
1908
11th to 20thDay
13%423313346%59%
1800
21st to endDay
15%42432233458%
1980
November1st to 10thDay
12%42342335%6%55%
1858
11th to 20thDay
8%425%5%2335%6%57%
1824
21st to endDay
17%6%24324235%51%
1710
December1st to 10thDay
15%5%2443345%6%49%
1710
11th to 20thDay
16%7%35%6%2435%5%45%
2161
21st to endDay
17%7%24423445%48%
3135
January1st to 10thNight
13%5%24323346%55%
2458
11th to 20thNight
15%6%24323345%53%
2379
21st to endNight
14%6%2442333454%
2574
February1st to 10thNight
16%6%25%423245%52%
2275
11th to 20thNight
18%6%24423346%48%
2098
21st to endNight
20%425%323335%49%
1722
March1st to 10thNight
17%5%35%42445%7%45%
1980
11th to 20thNight
15%5%35%425%346%49%
1980
21st to endNight
13%425%424447%52%
2178
April1st to 10thNight
9%42343446%8%53%
1980
11th to 20thNight
13%434424447%50%
1837
21st to endNight
11%5%2431345%7%55%
1720
May1st to 10thNight
9%6%35%42445%9%50%
1620
11th to 20thNight
10%5%235%3446%9%49%
1593
21st to endNight
8%4335%25%5%6%8%52%
1745
June1st to 10thNight
5%31243445%9%60%
1620
11th to 20thNight
3312323449%65%
1620
21st to endNight
42133245%6%10%59%
1620
July1st to 10thNight
44244346%6%10%53%
1620
11th to 20thNight
311231235%9%71%
1620
21st to endNight
11133245%6%12%61%
1772
August1st to 10thNight
111111235%11%71%
1611
11th to 20thNight
5%4244345%5%8%57%
1600
21st to endNight
33144345%6%10%57%
2018
September1st to 10thNight
6%42443346%8%57%
1980
11th to 20thNight
10%42443445%7%54%
1980
21st to endNight
6%313333347%63%
1980
October1st to 10thNight
6%21332345%8%64%
2032
11th to 20thNight
12%413222335%61%
2160
21st to endNight
16%5%1322223360%
2376
November1st to 10thNight
10%424323335%61%
2220
11th to 20thNight
8%42442335%7%57%
2354
21st to endNight
16%5%34423345%52%
2470
December1st to 10thNight
14%6%24423347%53%
2470
11th to 20thNight
14%7%245%23336%50%
3036
21st to endNight
17%6%24323335%53%
4532

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
33%37%19%30%7%
1708
11th to 20thDay
36%37%22%25%6%
1643
21st to endDay
35%36%18%29%10%
1782
February1st to 10thDay
44%26%18%20%10%
1700
11th to 20thDay
45%45%18%20%8%
1759
21st to endDay
42%25%15%22%13%
1534
March1st to 10thDay
40%5%7%17%22%10%
1980
11th to 20thDay
42%48%17%23%6%
1980
21st to endDay
39%5%9%19%20%8%
2178
April1st to 10thDay
38%5%10%20%17%9%
1980
11th to 20thDay
39%6%8%18%21%8%
2070
21st to endDay
38%5%8%20%24%5%
2236
May1st to 10thDay
38%6%8%23%19%6%
2340
11th to 20thDay
41%7%10%22%19%2
2306
21st to endDay
42%9%12%20%15%2
2531
June1st to 10thDay
27%9%15%29%17%3
2340
11th to 20thDay
28%7%14%29%18%4
2340
21st to endDay
27%7%12%29%22%3
2340
July1st to 10thDay
34%11%16%26%13%1
2276
11th to 20thDay
20%6%15%35%20%3
2271
21st to endDay
22%10%19%35%13%1
2405
August1st to 10thDay
16%6%15%37%24%2
2314
11th to 20thDay
28%8%14%28%19%3
2301
21st to endDay
28%8%14%31%16%3
2332
September1st to 10thDay
30%6%10%24%21%10%
1980
11th to 20thDay
36%7%11%18%21%8%
1980
21st to endDay
26%49%23%25%13%
1980
October1st to 10thDay
24%5%11%24%21%16%
1908
11th to 20thDay
28%37%18%27%17%
1800
21st to endDay
32%36%17%26%16%
1980
November1st to 10thDay
31%47%24%25%9%
1858
11th to 20thDay
29%49%19%29%10%
1824
21st to endDay
37%25%22%24%10%
1710
December1st to 10thDay
36%5%9%19%23%7%
1710
11th to 20thDay
42%46%15%25%8%
2159
21st to endDay
39%36%23%22%7%
3135
January1st to 10thNight
31%36%20%27%12%
2458
11th to 20thNight
35%37%19%25%10%
2379
21st to endNight
35%3415%29%13%
2574
February1st to 10thNight
37%37%17%22%13%
2275
11th to 20thNight
39%37%16%24%10%
2098
21st to endNight
39%47%14%20%16%
1722
March1st to 10thNight
39%49%15%20%13%
1980
11th to 20thNight
38%5%9%14%26%9%
1980
21st to endNight
34%5%10%19%25%8%
2178
April1st to 10thNight
29%5%11%23%19%13%
1980
11th to 20thNight
34%5%9%20%18%14%
1837
21st to endNight
30%5%9%23%28%5%
1720
May1st to 10thNight
33%6%10%22%20%9%
1620
11th to 20thNight
32%6%16%25%18%3
1594
21st to endNight
28%9%16%26%18%2
1746
June1st to 10thNight
20%8%16%31%21%4
1620
11th to 20thNight
17%6%14%36%20%7%
1620
21st to endNight
21%7%12%29%25%6%
1620
July1st to 10thNight
25%8%17%33%15%2
1575
11th to 20thNight
11%5%15%38%27%5%
1566
21st to endNight
14%8%19%40%18%1
1673
August1st to 10thNight
10%415%37%29%5%
1601
11th to 20thNight
24%6%14%27%22%6%
1600
21st to endNight
21%6%15%32%22%4
2018
September1st to 10thNight
26%5%12%24%23%10%
1980
11th to 20thNight
30%5%13%21%22%10%
1980
21st to endNight
21%39%21%30%16%
1980
October1st to 10thNight
19%5%10%26%21%19%
2032
11th to 20thNight
27%36%16%25%22%
2160
21st to endNight
31%2417%25%20%
2376
November1st to 10thNight
28%37%21%28%14%
2220
11th to 20thNight
27%47%20%28%14%
2354
21st to endNight
36%37%16%26%11%
2470
December1st to 10thNight
33%48%21%23%11%
2470
11th to 20thNight
37%36%16%27%11%
3037
21st to endNight
36%36%17%27%11%
4532

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
21%13%36%24%6%
270
11th to 20thDay
21%17%35%21%6%2
248
21st to endDay
21%15%37%17%9%1
264
February1st to 10thDay
24%14%36%20%5%
240
11th to 20thDay
28%16%40%12%4
240
21st to endDay
33%20%33%13%1
198
March1st to 10thDay
25%16%35%21%3
240
11th to 20thDay
25%18%35%15%5%1
240
21st to endDay
16%20%39%19%6%1
264
April1st to 10thDay
23%14%37%21%6%
240
11th to 20thDay
19%14%32%25%9%
348
21st to endDay
15%16%36%23%9%1
496
May1st to 10thDay
13%13%33%31%8%1
603
11th to 20thDay
15%6%29%31%16%3
625
21st to endDay
13%5%25%37%17%4
679
June1st to 10thDay
7%314%36%30%10%
630
11th to 20thDay
5%217%40%29%6%
630
21st to endDay
5%213%37%32%11%
630
July1st to 10thDay
6%211%30%40%11%
621
11th to 20thDay
215%34%45%14%
618
21st to endDay
35%29%49%14%
684
August1st to 10thDay
38%30%48%11%
626
11th to 20thDay
8%15%33%41%12%
615
21st to endDay
5%5%24%45%20%
451
September1st to 10thDay
8%1420%44%24%
270
11th to 20thDay
5%9%27%36%22%
270
21st to endDay
12%39%25%32%19%
270
October1st to 10thDay
4219%33%31%10%
270
11th to 20thDay
13%7%26%29%20%6%
270
21st to endDay
24%13%20%23%17%3
297
November1st to 10thDay
19%6%30%28%11%5%
270
11th to 20thDay
13%10%30%32%13%3
270
21st to endDay
20%14%32%25%7%1
270
December1st to 10thDay
19%10%35%24%10%3
270
11th to 20thDay
22%16%34%22%5%
270
21st to endDay
21%13%37%22%6%1
297
January1st to 10thNight
16%10%34%32%7%
950
11th to 20thNight
19%12%31%31%6%1
915
21st to endNight
17%10%36%31%6%
990
February1st to 10thNight
20%11%36%29%4
835
11th to 20thNight
21%12%39%25%4
704
21st to endNight
23%13%41%20%3
538
March1st to 10thNight
20%11%36%29%5%
540
11th to 20thNight
17%11%37%28%6%
540
21st to endNight
14%13%39%28%6%
594
April1st to 10thNight
10%10%46%29%4
540
11th to 20thNight
16%10%36%28%8%1
533
21st to endNight
15%10%39%27%9%1
540
May1st to 10thNight
10%10%38%34%8%1
540
11th to 20thNight
11%334%35%17%1
531
21st to endNight
9%429%39%17%2
584
June1st to 10thNight
6%217%46%25%4
540
11th to 20thNight
4122%54%18%1
540
21st to endNight
4215%40%33%5%
540
July1st to 10thNight
3112%42%36%5%
525
11th to 20thNight
38%43%42%4
522
21st to endNight
115%47%43%4
591
August1st to 10thNight
315%45%42%4
537
11th to 20thNight
7%5%41%41%7%
534
21st to endNight
5%1439%43%8%
594
September1st to 10thNight
6%10%39%40%5%
540
11th to 20thNight
12%27%39%36%4
540
21st to endNight
8%112%41%33%6%
540
October1st to 10thNight
7%217%43%28%4
592
11th to 20thNight
14%425%38%17%2
720
21st to endNight
18%7%28%30%16%2
792
November1st to 10thNight
11%430%39%15%1
740
11th to 20thNight
10%7%33%37%12%1
834
21st to endNight
20%9%32%28%10%1
950
December1st to 10thNight
15%9%34%34%7%
950
11th to 20thNight
21%8%32%33%6%
950
21st to endNight
20%9%33%31%6%
1045
Page generated at 2024-01-10 18:35:20. Version ac07

Copyright 2024 Attilla Danko


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