Mancave Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mancave Observatory clear sky chart from 2005-11-05 to 2017-09-22.

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
63%
15946
20%
47021
17%
15908
67%
15908
31%
29254

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
52%
716
19%
2327
16%
716
58%
716
25%
1443
January16th to endNight
50%
768
25%
2389
20%
768
57%
768
29%
1445
February1st to 15thNight
49%
701
24%
2104
18%
699
56%
699
32%
1264
February16th to endNight
54%
631
27%
1845
19%
631
63%
631
41%
1026
March1st to 15thNight
55%
720
30%
1980
18%
720
65%
720
45%
1091
March16th to endNight
58%
768
27%
2112
21%
768
62%
768
42%
1197
April1st to 15thNight
65%
718
23%
1976
19%
718
68%
718
46%
1071
April16th to endNight
62%
720
27%
1882
19%
720
67%
720
42%
1118
May1st to 15thNight
77%
562
29%
1642
25%
562
79%
562
46%
877
May16th to endNight
77%
561
23%
1683
19%
561
78%
561
37%
991
June1st to 15thNight
72%
540
10%
1620
9%
540
72%
540
25%
1125
June16th to endNight
80%
540
8%
1620
8%
540
80%
540
24%
1124
July1st to 15thNight
75%
510
6%
1530
6%
510
75%
510
19%
1147
July16th to endNight
76%
564
8%
1595
8%
531
77%
531
22%
1144
August1st to 15thNight
79%
539
5%
1675
6%
536
80%
536
24%
1146
August16th to endNight
65%
711
7%
2048
7%
711
65%
711
19%
1498
September1st to 15thNight
66%
720
7%
1980
7%
720
66%
720
18%
1465
September16th to endNight
64%
685
11%
1892
10%
685
64%
685
19%
1391
October1st to 15thNight
70%
660
25%
1848
25%
660
72%
660
35%
1120
October16th to endNight
57%
704
25%
2112
24%
704
62%
704
31%
1291
November1st to 15thNight
64%
700
31%
2101
29%
700
70%
700
39%
1196
November16th to endNight
55%
720
30%
2224
25%
720
64%
720
36%
1266
December1st to 15thNight
57%
720
24%
2340
23%
720
62%
720
29%
1403
December16th to endNight
61%
768
24%
2496
24%
768
64%
768
33%
1415

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%26%7%46%6%6%8%36%
47842
Night
6%425%5%35%5%6%9%43%
47228
TransparencyDay
42%8%14%16%13%5%
47543
Night
34%8%17%20%14%5%
47031
SeeingDay
9%212%20%25%29%
5802
Night
8%215%33%29%10%
15956

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 15thDay
10%5%35%5%45%5%6%10%37%
1611
16th to endDay
9%425%425%5%5%8%45%
1833
February1st to 15thDay
10%5%25%5%3446%5%45%
1750
16th to endDay
7%5%1443445%7%50%
1627
March1st to 15thDay
431343446%7%55%
1980
16th to endDay
7%4245%35%36%8%48%
2111
April1st to 15thDay
5%4246%37%5%7%9%44%
1972
16th to endDay
6%416%435%5%5%7%47%
2076
May1st to 15thDay
5%2145%35%5%6%8%50%
2316
16th to endDay
7%5%37%7%47%6%7%9%34%
2431
June1st to 15thDay
11%8%38%8%5%7%8%7%8%20%
2340
16th to endDay
7%6%38%10%5%9%8%9%8%21%
2340
July1st to 15thDay
8%6%310%11%7%9%7%7%8%19%
2340
16th to endDay
8%7%48%9%6%9%7%9%9%19%
2465
August1st to 15thDay
5%6%39%10%6%9%10%7%9%20%
2269
16th to endDay
10%6%28%9%7%8%8%7%9%21%
2141
September1st to 15thDay
8%5%39%10%6%7%8%8%10%19%
1980
16th to endDay
8%8%49%10%48%6%7%9%21%
1881
October1st to 15thDay
6%5%28%5%47%6%6%7%38%
1780
16th to endDay
9%6%25%5%25%45%6%44%
1760
November1st to 15thDay
6%415%5%35%46%8%49%
1757
16th to endDay
7%425%5%45%448%47%
1734
December1st to 15thDay
9%5%35%6%35%5%6%7%41%
1620
16th to endDay
7%5%25%5%45%5%5%8%44%
1728
January1st to 15thNight
8%5%35%6%35%5%6%8%40%
2327
16th to endNight
11%4245%2446%8%43%
2389
February1st to 15thNight
10%5%25%424446%48%
2103
16th to endNight
5%4244245%7%8%50%
1845
March1st to 15thNight
42134235%5%8%56%
1980
16th to endNight
5%325%5%235%48%54%
2112
April1st to 15thNight
43124245%6%9%55%
1976
16th to endNight
4325%435%46%9%51%
1882
May1st to 15thNight
331331445%9%58%
1642
16th to endNight
4314435%5%7%8%49%
1682
June1st to 15thNight
9%436%7%26%6%7%10%34%
1620
16th to endNight
4325%6%47%8%9%16%31%
1620
July1st to 15thNight
5%6%37%5%37%7%10%10%30%
1620
16th to endNight
3435%7%47%8%10%14%28%
1703
August1st to 15thNight
4425%6%46%6%9%14%34%
1686
16th to endNight
7%5%26%7%5%7%6%8%10%30%
2048
September1st to 15thNight
6%6%28%6%46%8%8%12%28%
1980
16th to endNight
9%6%26%7%47%7%9%9%27%
1892
October1st to 15thNight
5%415%5%345%6%8%47%
1848
16th to endNight
9%6%25%42335%8%46%
2112
November1st to 15thNight
5%3345%345%5%8%50%
2101
16th to endNight
7%325%435%46%8%49%
2224
December1st to 15thNight
8%425%446%45%8%44%
2340
16th to endNight
6%425%425%6%5%9%47%
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
40%6%8%20%18%4
1612
16th to endDay
35%5%8%20%22%7%
1833
February1st to 15thDay
37%5%7%16%19%13%
1752
16th to endDay
32%5%10%18%23%10%
1627
March1st to 15thDay
27%311%25%22%9%
1980
16th to endDay
33%410%22%21%8%
2112
April1st to 15thDay
33%7%13%20%19%6%
1972
16th to endDay
32%6%9%19%24%7%
2076
May1st to 15thDay
29%6%13%22%20%7%
2316
16th to endDay
42%7%14%19%14%1
2435
June1st to 15thDay
56%8%17%13%2
2340
16th to endDay
52%12%20%12%1
2340
July1st to 15thDay
58%14%19%5%1
2201
16th to endDay
54%13%22%9%1
2310
August1st to 15thDay
52%13%26%7%
2256
16th to endDay
55%14%20%8%
2141
September1st to 15thDay
54%14%20%8%2
1980
16th to endDay
54%8%17%13%41
1881
October1st to 15thDay
40%7%10%17%16%6%
1780
16th to endDay
38%5%7%15%21%11%
1760
November1st to 15thDay
31%49%23%22%9%
1757
16th to endDay
34%5%8%19%18%13%
1734
December1st to 15thDay
39%6%12%19%15%6%
1620
16th to endDay
36%6%11%21%18%6%
1728
January1st to 15thNight
39%5%11%23%14%4
2327
16th to endNight
36%5%9%22%19%7%
2389
February1st to 15thNight
35%37%19%21%12%
2112
16th to endNight
26%5%15%22%22%8%
1845
March1st to 15thNight
24%5%12%28%21%7%
1980
16th to endNight
27%412%25%21%8%
2112
April1st to 15thNight
23%5%18%26%19%6%
1976
16th to endNight
28%5%13%23%24%5%
1882
May1st to 15thNight
22%6%13%31%19%7%
1643
16th to endNight
29%7%18%26%17%1
1684
June1st to 15thNight
42%9%24%17%5%
1620
16th to endNight
35%17%27%15%5%
1620
July1st to 15thNight
43%16%29%8%1
1530
16th to endNight
38%17%29%14%
1595
August1st to 15thNight
34%17%37%10%
1675
16th to endNight
43%14%28%10%1
2048
September1st to 15thNight
44%15%23%13%2
1980
16th to endNight
46%12%20%14%5%1
1892
October1st to 15thNight
32%6%14%18%20%6%
1848
16th to endNight
35%6%9%16%22%9%
2112
November1st to 15thNight
28%5%9%22%22%10%
2101
16th to endNight
31%410%23%17%12%
2224
December1st to 15thNight
36%5%12%23%16%5%
2340
16th to endNight
31%5%15%21%19%6%
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
20%6%33%22%15%2
90
16th to endDay
10%18%31%27%10%2
96
February1st to 15thDay
13%8%27%26%16%6%
90
16th to endDay
10%432%37%14%
128
March1st to 15thDay
5%229%33%24%4
270
16th to endDay
8%6%21%30%27%5%
288
April1st to 15thDay
6%220%32%30%7%
270
16th to endDay
7%313%30%31%14%
270
May1st to 15thDay
5%38%24%37%20%
288
16th to endDay
5%16%19%29%37%
331
June1st to 15thDay
17%26%13%20%39%
315
16th to endDay
7%146%20%59%
315
July1st to 15thDay
7%2317%69%
305
16th to endDay
13%127%17%57%
326
August1st to 15thDay
8%25%18%63%
313
16th to endDay
11%136%24%52%
332
September1st to 15thDay
8%26%9%26%45%
315
16th to endDay
7%112%40%36%
278
October1st to 15thDay
7%18%28%37%15%
255
16th to endDay
11%215%30%28%11%
272
November1st to 15thDay
9%113%32%33%9%
265
16th to endDay
7%225%32%24%7%
204
December1st to 15thDay
11%237%35%13%
90
16th to endDay
6%410%38%35%5%
96
January1st to 15thNight
11%5%21%42%17%1
720
16th to endNight
13%5%23%40%15%
768
February1st to 15thNight
12%5%27%40%14%
704
16th to endNight
7%327%45%14%
631
March1st to 15thNight
5%430%44%14%
720
16th to endNight
6%323%45%18%1
768
April1st to 15thNight
6%220%47%21%1
718
16th to endNight
6%220%45%24%
720
May1st to 15thNight
49%49%31%3
563
16th to endNight
5%6%37%41%8%
563
June1st to 15thNight
9%2219%47%17%
540
16th to endNight
6%29%44%36%
540
July1st to 15thNight
7%15%44%40%
510
16th to endNight
416%46%40%
564
August1st to 15thNight
6%15%45%40%
539
16th to endNight
11%1310%42%30%
711
September1st to 15thNight
10%416%41%26%
720
16th to endNight
13%421%42%16%
685
October1st to 15thNight
9%7%41%35%5%
660
16th to endNight
12%118%32%31%3
704
November1st to 15thNight
6%317%45%24%3
700
16th to endNight
8%324%40%21%1
720
December1st to 15thNight
10%219%41%23%
720
16th to endNight
8%320%41%24%1
768
Page generated at 2017-09-23 06:43:35. Version ac04

Copyright 2017 A. Danko


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