Mancave Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mancave 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
62%
24492
20%
74528
17%
24444
66%
24444
30%
46302

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
49%
757
23%
2459
18%
757
57%
757
29%
1443
January11th to 20thNight
54%
732
25%
2378
21%
732
63%
732
31%
1370
January21st to endNight
43%
792
23%
2413
17%
792
52%
792
27%
1516
February1st to 10thNight
48%
720
23%
2160
18%
720
54%
720
31%
1323
February11th to 20thNight
54%
700
26%
2099
18%
700
61%
700
40%
1152
February21st to endNight
59%
592
29%
1704
23%
592
65%
592
39%
974
March1st to 10thNight
54%
720
33%
1980
20%
720
64%
720
50%
1045
March11th to 20thNight
58%
720
29%
1980
20%
720
64%
720
44%
1108
March21st to endNight
57%
792
31%
2178
23%
792
63%
792
44%
1217
April1st to 10thNight
62%
720
24%
1980
18%
720
66%
720
45%
1082
April11th to 20thNight
57%
711
21%
1953
16%
711
62%
711
40%
1129
April21st to endNight
63%
720
29%
1835
20%
720
66%
720
46%
1076
May1st to 10thNight
77%
575
32%
1655
27%
575
80%
575
54%
827
May11th to 20thNight
71%
531
18%
1592
14%
531
73%
531
33%
978
May21st to endNight
74%
582
23%
1745
20%
582
75%
582
36%
1039
June1st to 10thNight
73%
540
14%
1620
13%
540
73%
540
26%
1101
June11th to 20thNight
77%
540
11%
1620
10%
540
78%
540
29%
1051
June21st to endNight
78%
540
9%
1620
8%
540
78%
540
23%
1137
July1st to 10thNight
74%
525
5%
1575
5%
525
74%
525
21%
1152
July11th to 20thNight
76%
522
5%
1566
5%
522
76%
522
20%
1170
July21st to endNight
74%
591
8%
1672
8%
558
75%
558
20%
1214
August1st to 10thNight
78%
537
4%
1609
5%
534
78%
534
24%
1134
August11th to 20thNight
78%
542
5%
1784
6%
542
78%
542
21%
1228
August21st to endNight
62%
792
7%
2178
7%
792
62%
792
16%
1667
September1st to 10thNight
71%
720
7%
1980
7%
720
71%
720
21%
1422
September11th to 20thNight
63%
720
8%
1980
8%
720
64%
720
18%
1472
September21st to endNight
62%
720
15%
1980
13%
720
64%
720
20%
1435
October1st to 10thNight
63%
720
21%
1980
19%
720
65%
720
29%
1287
October11th to 20thNight
66%
720
27%
2124
26%
720
69%
720
34%
1264
October21st to endNight
62%
792
27%
2376
26%
792
67%
792
35%
1408
November1st to 10thNight
59%
740
26%
2221
23%
740
65%
740
35%
1324
November11th to 20thNight
55%
760
30%
2280
26%
760
62%
760
34%
1346
November21st to endNight
56%
760
28%
2382
25%
760
62%
760
33%
1368
December1st to 10thNight
59%
760
26%
2470
24%
760
66%
760
34%
1403
December11th to 20thNight
57%
759
24%
2936
23%
758
61%
758
26%
1653
December21st to endNight
55%
828
15%
4464
22%
817
61%
817
17%
2787

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
7%5%36%7%46%6%7%9%39%
74843
Night
7%5%25%5%35%6%7%10%44%
74909
TransparencyDay
39%9%15%18%14%5%
74566
Night
34%9%17%20%15%5%
74705
SeeingDay
8%416%25%26%22%
14398
Night
8%316%34%29%10%
24509

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
10%6%35%435%5%5%11%44%
1706
11th to 20thDay
6%4245%35%6%7%9%49%
1644
21st to endDay
11%435%5%36%5%5%8%45%
1940
February1st to 10thDay
10%5%25%6%35%5%7%6%45%
1800
11th to 20thDay
5%42443445%9%56%
1748
21st to endDay
7%425%5%445%6%7%51%
1551
March1st to 10thDay
3324435%5%6%7%59%
1980
11th to 20thDay
6%3235%4447%8%54%
1980
21st to endDay
6%4245%35%45%8%54%
2178
April1st to 10thDay
5%4245%36%6%7%10%48%
1980
11th to 20thDay
7%5%26%5%46%6%8%9%42%
1956
21st to endDay
5%3245%45%6%6%8%53%
2124
May1st to 10thDay
4314435%46%9%58%
2318
11th to 20thDay
9%5%25%6%47%7%8%9%38%
2301
21st to endDay
7%5%37%7%5%7%6%7%8%36%
2531
June1st to 10thDay
12%9%38%8%6%7%8%8%10%22%
2340
11th to 20thDay
7%5%38%9%5%9%9%8%9%26%
2340
21st to endDay
7%7%48%9%5%9%8%8%9%25%
2340
July1st to 10thDay
8%6%39%10%6%9%7%8%10%23%
2340
11th to 20thDay
6%6%39%10%6%10%8%9%11%22%
2340
21st to endDay
8%6%48%10%6%9%8%8%10%22%
2547
August1st to 10thDay
6%6%38%10%6%9%10%8%11%23%
2312
11th to 20thDay
5%5%310%10%7%9%10%7%9%23%
2097
21st to endDay
10%6%39%9%7%9%8%7%10%22%
2178
September1st to 10thDay
7%5%38%10%6%8%9%9%11%23%
1980
11th to 20thDay
7%7%48%10%6%9%8%8%10%23%
1980
21st to endDay
8%6%39%8%5%7%7%8%9%30%
1980
October1st to 10thDay
8%6%38%7%46%6%7%8%37%
1980
11th to 20thDay
6%6%26%446%6%5%9%46%
1834
21st to endDay
8%5%25%6%36%5%6%8%48%
1980
November1st to 10thDay
7%4146%35%5%6%8%50%
1857
11th to 20thDay
8%5%36%5%35%5%6%8%46%
1900
21st to endDay
8%425%5%45%5%5%9%47%
1794
December1st to 10thDay
7%435%6%35%5%6%9%48%
1710
11th to 20thDay
10%6%36%5%345%5%9%45%
2153
21st to endDay
11%8%38%7%5%6%5%6%7%34%
3124
January1st to 10thNight
9%5%35%6%35%5%6%9%44%
2459
11th to 20thNight
8%6%35%5%345%6%9%47%
2378
21st to endNight
12%5%25%5%35%5%6%8%43%
2413
February1st to 10thNight
9%6%26%5%35%5%5%8%47%
2160
11th to 20thNight
9%41343446%7%54%
2098
21st to endNight
6%4245%25%5%7%9%51%
1704
March1st to 10thNight
42133245%5%8%61%
1980
11th to 20thNight
6%3245%345%6%10%54%
1980
21st to endNight
5%425%4335%5%8%57%
2178
April1st to 10thNight
5%3233345%6%10%56%
1980
11th to 20thNight
6%4245%35%5%7%10%49%
1953
21st to endNight
5%3145%345%5%9%56%
1835
May1st to 10thNight
331232345%10%64%
1655
11th to 20thNight
7%326%5%46%5%7%8%47%
1592
21st to endNight
5%4246%35%6%7%8%50%
1744
June1st to 10thNight
10%5%36%6%36%6%8%10%37%
1620
11th to 20thNight
5%435%6%36%7%9%14%38%
1620
21st to endNight
5%426%7%47%8%9%16%32%
1620
July1st to 10thNight
5%7%37%6%46%7%10%12%32%
1620
11th to 20thNight
5%5%36%8%48%8%9%14%29%
1620
21st to endNight
45%37%7%5%8%8%10%13%30%
1771
August1st to 10thNight
4436%7%47%7%9%15%33%
1620
11th to 20thNight
5%5%25%7%5%8%7%10%13%33%
1784
21st to endNight
8%6%38%8%6%7%8%7%10%28%
2178
September1st to 10thNight
5%6%38%6%5%6%7%9%15%30%
1980
11th to 20thNight
10%6%47%8%5%7%7%8%10%29%
1980
21st to endNight
10%7%37%7%47%7%8%9%30%
1980
October1st to 10thNight
7%6%26%6%45%7%7%8%42%
1980
11th to 20thNight
7%5%35%44446%9%49%
2124
21st to endNight
8%5%25%5%3445%9%50%
2376
November1st to 10thNight
7%435%5%446%6%8%50%
2221
11th to 20thNight
8%5%35%5%345%6%8%49%
2280
21st to endNight
8%425%5%35%46%9%47%
2382
December1st to 10thNight
7%425%5%45%46%9%48%
2470
11th to 20thNight
11%5%25%425%5%5%8%48%
3042
21st to endNight
13%7%47%6%45%6%5%7%37%
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
35%6%9%24%18%8%
1707
11th to 20thDay
30%5%8%26%22%8%
1644
21st to endDay
38%5%8%19%21%8%
1940
February1st to 10thDay
36%6%10%20%18%10%
1800
11th to 20thDay
26%410%23%26%11%
1758
21st to endDay
31%7%10%18%25%9%
1551
March1st to 10thDay
23%411%26%25%11%
1980
11th to 20thDay
27%5%11%26%21%9%
1980
21st to endDay
29%5%10%25%23%8%
2178
April1st to 10thDay
28%7%17%24%18%6%
1980
11th to 20thDay
35%7%12%18%21%6%
1956
21st to endDay
28%7%9%23%25%8%
2124
May1st to 10thDay
23%6%12%25%25%9%
2318
11th to 20thDay
39%9%15%19%16%2
2305
21st to endDay
42%8%14%19%16%2
2531
June1st to 10thDay
54%10%18%14%4
2340
11th to 20thDay
47%12%22%16%3
2340
21st to endDay
49%13%22%13%21
2340
July1st to 10thDay
51%15%25%7%2
2275
11th to 20thDay
51%15%25%9%
2271
21st to endDay
50%14%23%10%1
2405
August1st to 10thDay
49%13%30%8%
2299
11th to 20thDay
51%15%24%9%
2097
21st to endDay
53%15%21%9%2
2178
September1st to 10thDay
49%14%24%11%1
1980
11th to 20thDay
50%13%20%13%3
1980
21st to endDay
46%11%16%16%9%2
1980
October1st to 10thDay
42%8%13%17%13%7%
1980
11th to 20thDay
34%7%9%22%23%4
1834
21st to endDay
33%7%9%20%20%12%
1980
November1st to 10thDay
30%6%12%22%18%12%
1857
11th to 20thDay
35%6%9%22%20%8%
1900
21st to endDay
33%6%11%21%21%8%
1794
December1st to 10thDay
33%6%13%25%17%6%
1710
11th to 20thDay
37%5%10%20%18%11%
2150
21st to endDay
47%7%10%18%15%4
3124
January1st to 10thNight
35%6%11%23%18%7%
2459
11th to 20thNight
34%5%10%26%19%7%
2378
21st to endNight
38%7%10%20%18%7%
2413
February1st to 10thNight
36%6%11%20%20%8%
2160
11th to 20thNight
28%411%23%23%11%
2099
21st to endNight
27%7%13%21%26%7%
1704
March1st to 10thNight
20%6%11%30%25%8%
1980
11th to 20thNight
26%5%15%28%19%7%
1980
21st to endNight
25%5%11%27%24%8%
2178
April1st to 10thNight
23%6%20%28%16%7%
1980
11th to 20thNight
27%7%17%23%21%5%
1953
21st to endNight
26%6%13%25%25%5%
1835
May1st to 10thNight
17%5%12%32%23%10%
1655
11th to 20thNight
32%9%20%23%16%1
1593
21st to endNight
30%8%18%24%19%1
1745
June1st to 10thNight
40%10%22%22%6%
1620
11th to 20thNight
32%13%31%19%4
1620
21st to endNight
36%17%26%15%6%
1620
July1st to 10thNight
41%16%32%10%1
1575
11th to 20thNight
41%19%30%10%
1566
21st to endNight
39%19%30%13%
1672
August1st to 10thNight
36%17%35%11%1
1609
11th to 20thNight
39%15%37%9%
1784
21st to endNight
48%16%23%11%2
2178
September1st to 10thNight
39%17%28%14%2
1980
11th to 20thNight
47%13%22%14%2
1980
21st to endNight
45%12%18%15%9%1
1980
October1st to 10thNight
36%10%15%18%14%6%
1980
11th to 20thNight
32%7%12%23%21%4
2124
21st to endNight
32%6%11%20%21%9%
2376
November1st to 10thNight
31%7%11%20%19%11%
2221
11th to 20thNight
32%7%10%24%19%8%
2280
21st to endNight
32%6%10%24%20%7%
2382
December1st to 10thNight
32%5%13%28%17%4
2470
11th to 20thNight
34%5%10%21%17%12%
3044
21st to endNight
43%8%14%16%15%4
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
10%9%38%28%13%2
270
11th to 20thDay
5%11%32%32%15%4
248
21st to endDay
12%16%39%25%7%1
264
February1st to 10thDay
10%9%29%32%16%4
240
11th to 20thDay
6%8%29%34%18%5%
240
21st to endDay
5%7%26%38%19%5%
269
March1st to 10thDay
46%35%35%19%2
420
11th to 20thDay
8%7%26%30%27%4
420
21st to endDay
5%6%24%36%24%5%
462
April1st to 10thDay
6%8%27%35%21%3
420
11th to 20thDay
8%6%23%36%21%7%
412
21st to endDay
6%421%29%30%9%
420
May1st to 10thDay
6%213%33%33%13%
423
11th to 20thDay
9%411%26%31%19%
447
21st to endDay
7%28%20%32%31%
485
June1st to 10thDay
15%48%22%25%27%
450
11th to 20thDay
8%26%16%29%39%
450
21st to endDay
5%2412%24%54%
450
July1st to 10thDay
7%236%22%60%
445
11th to 20thDay
5%238%31%51%
444
21st to endDay
10%25%10%24%48%
488
August1st to 10thDay
7%210%28%52%
446
11th to 20thDay
5%148%28%54%
439
21st to endDay
9%2414%31%39%
495
September1st to 10thDay
6%25%12%30%44%
450
11th to 20thDay
6%3418%34%35%
450
21st to endDay
7%2318%38%33%
450
October1st to 10thDay
11%212%31%34%10%
450
11th to 20thDay
6%215%32%34%12%
450
21st to endDay
7%314%36%31%8%
495
November1st to 10thDay
10%419%31%30%7%
455
11th to 20thDay
11%5%22%35%23%5%
460
21st to endDay
9%5%26%32%24%5%
354
December1st to 10thDay
5%7%30%31%18%8%
270
11th to 20thDay
12%6%29%31%19%3
270
21st to endDay
6%8%25%37%19%5%
297
January1st to 10thNight
10%6%28%41%15%1
760
11th to 20thNight
11%6%23%44%16%1
732
21st to endNight
13%8%29%38%12%
792
February1st to 10thNight
12%6%29%37%16%
720
11th to 20thNight
9%5%26%42%17%1
703
21st to endNight
7%423%48%17%
592
March1st to 10thNight
45%33%45%13%
720
11th to 20thNight
7%425%46%16%1
720
21st to endNight
6%327%45%18%1
792
April1st to 10thNight
6%423%48%19%1
720
11th to 20thNight
7%326%45%18%1
711
21st to endNight
5%323%47%22%1
720
May1st to 10thNight
5%112%49%31%3
575
11th to 20thNight
8%19%45%33%4
531
21st to endNight
5%27%34%44%8%
584
June1st to 10thNight
10%3325%46%13%
540
11th to 20thNight
5%1315%51%26%
540
21st to endNight
6%139%48%34%
540
July1st to 10thNight
7%226%45%38%
525
11th to 20thNight
5%216%46%41%
522
21st to endNight
5%127%49%36%
591
August1st to 10thNight
5%127%51%34%
537
11th to 20thNight
6%117%41%43%
542
21st to endNight
11%3416%40%26%
792
September1st to 10thNight
8%1316%46%26%
720
11th to 20thNight
11%3421%41%19%
720
21st to endNight
12%26%24%40%16%
720
October1st to 10thNight
10%113%41%30%5%
720
11th to 20thNight
8%312%36%38%3
720
21st to endNight
11%316%39%29%3
792
November1st to 10thNight
8%421%41%23%3
740
11th to 20thNight
8%6%21%42%21%2
760
21st to endNight
9%423%44%19%1
760
December1st to 10thNight
8%321%41%26%1
760
11th to 20thNight
11%321%42%21%1
760
21st to endNight
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836
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