Mount Nemo Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mount Nemo Observatory clear sky chart from 2005-11-05 to 2018-02-13.

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
33%
15450
15%
48717
9%
15414
41%
15414
18%
33352

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
15%
776
11%
2651
4%
776
24%
776
9%
2023
January16th to endNight
15%
832
13%
2704
4%
832
25%
832
10%
2038
February1st to 15thNight
16%
750
9%
2444
3%
750
24%
750
11%
1874
February16th to endNight
24%
631
13%
2005
5%
631
34%
631
13%
1466
March1st to 15thNight
22%
720
14%
1980
7%
720
29%
720
14%
1492
March16th to endNight
27%
768
20%
2112
8%
768
38%
768
19%
1454
April1st to 15thNight
27%
718
16%
1832
6%
718
32%
718
21%
1323
April16th to endNight
36%
552
21%
1632
7%
552
46%
552
22%
1049
May1st to 15thNight
40%
517
17%
1597
10%
517
47%
517
20%
1053
May16th to endNight
42%
374
17%
1497
13%
374
54%
374
21%
855
June1st to 15thNight
38%
360
13%
1440
10%
360
51%
360
18%
861
June16th to endNight
47%
360
15%
1345
16%
360
56%
360
22%
777
July1st to 15thNight
62%
340
17%
1339
23%
340
66%
340
32%
675
July16th to endNight
55%
520
16%
1551
14%
487
64%
487
30%
888
August1st to 15thNight
62%
539
18%
1609
13%
536
66%
536
33%
949
August16th to endNight
60%
616
23%
1762
15%
616
64%
616
34%
1034
September1st to 15thNight
56%
720
22%
1828
12%
720
60%
720
33%
1177
September16th to endNight
56%
717
24%
1992
17%
717
60%
717
31%
1233
October1st to 15thNight
40%
720
19%
2160
16%
720
46%
720
23%
1413
October16th to endNight
26%
768
16%
2304
10%
768
35%
768
16%
1669
November1st to 15thNight
33%
760
18%
2561
14%
760
41%
760
19%
1666
November16th to endNight
22%
780
13%
2730
5%
780
32%
780
11%
1949
December1st to 15thNight
16%
780
8%
2730
3%
780
22%
780
9%
2082
December16th to endNight
13%
832
8%
2912
2%
832
20%
832
6%
2352

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
13%7%36%6%35%5%5%7%32%
49289
Night
14%7%36%5%3445%7%36%
48899
Cloud CoverDay
13%7%36%6%35%5%5%7%34%
49299
Night
14%7%36%5%3445%7%36%
48903
TransparencyDay
48%5%13%20%10%1
48989
Night
47%5%11%21%11%1
48717
SeeingDay
15%13%22%25%15%8%
5857
Night
15%20%23%25%12%1
15458

By Month

Percentage Cloud Cover NE (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
16%10%5%9%7%5%5%45%7%21%
1614
16th to endDay
11%13%6%12%9%5%6%5%5%5%18%
1872
February1st to 15thDay
14%14%6%8%8%46%5%5%6%19%
1683
16th to endDay
17%11%48%6%36%5%6%7%23%
1466
March1st to 15thDay
14%10%5%9%7%45%445%28%
1969
16th to endDay
14%8%5%7%6%25%45%6%33%
2112
April1st to 15thDay
18%9%45%6%35%45%6%30%
2116
16th to endDay
17%7%36%5%24335%39%
2338
May1st to 15thDay
15%5%37%6%345%6%7%35%
2352
16th to endDay
10%5%25%6%35%45%8%41%
2618
June1st to 15thDay
13%5%25%5%345%6%8%39%
2520
16th to endDay
11%425%5%36%5%6%8%38%
2603
July1st to 15thDay
7%424436%6%8%9%40%
2529
16th to endDay
9%425%5%45%6%8%10%37%
2507
August1st to 15thDay
7%426%6%46%6%6%9%38%
2340
16th to endDay
10%5%25%5%446%5%8%40%
2426
September1st to 15thDay
13%5%25%6%35%5%5%7%40%
2130
16th to endDay
12%425%6%3445%7%41%
1967
October1st to 15thDay
18%7%35%6%34446%35%
1800
16th to endDay
22%9%26%7%45%5%5%5%25%
1920
November1st to 15thDay
12%9%37%6%45%5%5%8%31%
1623
16th to endDay
16%11%47%6%35%5%6%7%24%
1560
December1st to 15thDay
14%15%5%10%8%35%5%5%6%20%
1560
16th to endDay
19%12%5%9%8%46%6%5%6%15%
1664
January1st to 15thNight
18%10%5%8%7%35%5%5%6%23%
2651
16th to endNight
13%10%5%9%7%46%5%5%7%24%
2704
February1st to 15thNight
14%10%6%8%8%35%46%7%25%
2442
16th to endNight
12%10%5%7%7%35%5%5%7%28%
2005
March1st to 15thNight
17%7%46%6%35%5%5%6%30%
1968
16th to endNight
14%8%47%324245%41%
2112
April1st to 15thNight
17%6%35%5%34447%36%
1832
16th to endNight
11%5%37%5%34445%44%
1632
May1st to 15thNight
14%5%25%5%35%5%5%7%39%
1597
16th to endNight
11%42443445%7%47%
1495
June1st to 15thNight
11%425%5%35%46%9%40%
1440
16th to endNight
9%4244345%6%8%46%
1345
July1st to 15thNight
5%21432445%9%56%
1419
16th to endNight
7%223435%45%9%49%
1658
August1st to 15thNight
6%213425%5%6%9%50%
1620
16th to endNight
9%4135%34445%53%
1762
September1st to 15thNight
12%31442445%7%49%
1828
16th to endNight
10%42442446%6%48%
1992
October1st to 15thNight
17%5%25%4235%5%6%41%
2160
16th to endNight
18%9%36%435%45%5%32%
2304
November1st to 15thNight
16%6%25%5%345%6%7%37%
2561
16th to endNight
17%8%36%5%35%5%5%8%28%
2730
December1st to 15thNight
18%12%48%5%35%5%6%6%24%
2730
16th to endNight
19%11%7%10%6%45%5%6%6%17%
2912

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
15%11%49%8%45%5%5%6%22%
1614
16th to endDay
10%13%6%11%9%5%6%6%5%6%18%
1872
February1st to 15thDay
14%14%6%9%8%45%5%5%6%19%
1683
16th to endDay
17%10%47%7%45%5%5%7%24%
1466
March1st to 15thDay
14%10%5%10%7%35%445%27%
1980
16th to endDay
14%7%46%6%25%5%5%6%35%
2111
April1st to 15thDay
17%8%37%5%36%45%6%31%
2116
16th to endDay
16%8%35%5%33345%40%
2338
May1st to 15thDay
14%6%36%5%345%6%7%36%
2352
16th to endDay
10%5%25%5%35%45%8%42%
2618
June1st to 15thDay
13%5%25%6%35%5%5%8%40%
2520
16th to endDay
11%4245%35%5%7%9%39%
2603
July1st to 15thDay
7%4145%36%6%7%9%42%
2529
16th to endDay
8%4245%36%6%8%10%38%
2507
August1st to 15thDay
7%425%6%46%5%7%8%41%
2340
16th to endDay
10%435%5%35%45%7%44%
2426
September1st to 15thDay
12%5%346%26%45%7%41%
2130
16th to endDay
12%425%4345%5%8%42%
1967
October1st to 15thDay
17%5%35%6%35%45%7%35%
1800
16th to endDay
21%8%37%6%345%5%5%26%
1920
November1st to 15thDay
10%8%47%6%35%5%5%9%32%
1623
16th to endDay
16%10%47%6%35%5%6%7%25%
1560
December1st to 15thDay
13%14%49%7%46%45%7%21%
1560
16th to endDay
18%13%48%9%45%5%6%6%16%
1664
January1st to 15thNight
17%11%5%8%6%345%5%6%23%
2651
16th to endNight
12%10%6%8%7%36%5%5%7%24%
2704
February1st to 15thNight
14%11%5%9%7%35%5%5%6%25%
2435
16th to endNight
13%10%5%8%6%35%5%5%6%29%
2005
March1st to 15thNight
18%7%47%5%35%5%47%29%
1980
16th to endNight
15%8%46%424435%41%
2112
April1st to 15thNight
17%6%36%5%35%446%36%
1832
16th to endNight
11%6%35%5%24446%43%
1632
May1st to 15thNight
14%435%5%345%5%8%38%
1596
16th to endNight
11%4145%25%45%7%47%
1495
June1st to 15thNight
12%425%5%25%5%5%8%41%
1440
16th to endNight
9%3245%35%5%5%7%46%
1345
July1st to 15thNight
5%21333435%9%55%
1419
16th to endNight
7%3244335%6%9%50%
1658
August1st to 15thNight
7%213425%46%10%50%
1620
16th to endNight
7%425%423446%52%
1762
September1st to 15thNight
12%31443345%7%48%
1828
16th to endNight
10%4245%3435%7%47%
1992
October1st to 15thNight
17%6%2442345%6%41%
2160
16th to endNight
19%8%36%5%35%45%6%31%
2304
November1st to 15thNight
16%5%25%435%45%8%37%
2561
16th to endNight
17%8%46%6%25%5%6%7%29%
2730
December1st to 15thNight
18%13%47%5%4445%6%24%
2730
16th to endNight
19%11%7%9%7%35%45%6%18%
2912

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
62%6%9%13%7%
1615
16th to endDay
66%5%11%11%5%
1872
February1st to 15thDay
65%6%8%14%4
1685
16th to endDay
60%5%12%14%5%1
1466
March1st to 15thDay
60%412%16%6%
1980
16th to endDay
49%5%11%20%11%1
2112
April1st to 15thDay
54%312%17%11%
2116
16th to endDay
46%310%21%15%2
2338
May1st to 15thDay
46%6%10%24%11%
2352
16th to endDay
40%6%13%23%13%1
2622
June1st to 15thDay
41%6%12%24%13%1
2520
16th to endDay
39%6%15%23%14%
2603
July1st to 15thDay
34%6%13%25%18%2
2380
16th to endDay
39%7%15%22%11%2
2351
August1st to 15thDay
37%9%16%21%13%2
2327
16th to endDay
38%6%15%25%12%1
2426
September1st to 15thDay
42%5%14%24%11%
2130
16th to endDay
39%5%14%28%11%
1967
October1st to 15thDay
49%412%21%10%1
1800
16th to endDay
57%5%14%15%6%
1920
November1st to 15thDay
46%7%15%20%8%
1623
16th to endDay
56%5%15%14%6%
1560
December1st to 15thDay
61%6%14%13%3
1560
16th to endDay
67%7%10%11%3
1664
January1st to 15thNight
61%5%10%12%8%
2651
16th to endNight
59%5%11%17%5%
2704
February1st to 15thNight
59%6%11%16%5%
2444
16th to endNight
55%5%11%19%8%
2005
March1st to 15thNight
56%411%20%6%
1980
16th to endNight
46%47%23%15%2
2112
April1st to 15thNight
50%310%21%13%1
1832
16th to endNight
42%48%22%18%4
1632
May1st to 15thNight
43%5%9%25%13%2
1597
16th to endNight
37%5%13%25%15%3
1497
June1st to 15thNight
40%6%11%24%16%1
1440
16th to endNight
35%6%14%24%18%1
1345
July1st to 15thNight
26%5%11%25%26%3
1339
16th to endNight
30%7%14%25%18%3
1551
August1st to 15thNight
29%7%16%30%13%2
1609
16th to endNight
31%5%12%30%17%2
1762
September1st to 15thNight
35%5%12%29%15%2
1828
16th to endNight
35%5%10%32%15%
1992
October1st to 15thNight
43%411%25%15%
2160
16th to endNight
52%5%12%20%8%
2304
November1st to 15thNight
43%6%13%22%13%
2561
16th to endNight
52%7%13%18%6%
2730
December1st to 15thNight
60%6%13%14%5%
2730
16th to endNight
66%6%10%12%4
2912

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%15%42%18%9%
104
16th to endDay
21%18%37%18%4
144
February1st to 15thDay
22%11%51%11%2
126
16th to endDay
22%16%28%28%2
83
March1st to 15thDay
18%17%30%25%8%
270
16th to endDay
20%17%27%25%7%1
288
April1st to 15thDay
18%20%22%27%7%2
270
16th to endDay
14%19%25%22%10%8%
270
May1st to 15thDay
16%14%20%24%16%7%
288
16th to endDay
12%12%23%25%18%6%
331
June1st to 15thDay
13%13%18%31%19%2
315
16th to endDay
13%15%20%26%17%6%
398
July1st to 15thDay
10%9%12%30%24%13%
314
16th to endDay
8%11%16%31%18%14%
326
August1st to 15thDay
9%6%15%28%23%17%
313
16th to endDay
10%6%14%23%24%20%
332
September1st to 15thDay
9%7%12%26%25%18%
315
16th to endDay
13%7%13%22%22%19%
314
October1st to 15thDay
19%12%17%24%16%9%
315
16th to endDay
21%13%27%26%10%
336
November1st to 15thDay
13%11%27%30%12%4
129
16th to endDay
20%12%34%22%8%2
90
December1st to 15thDay
17%21%28%24%7%
90
16th to endDay
21%20%42%12%2
96
January1st to 15thNight
16%28%31%18%4
780
16th to endNight
14%26%32%20%5%
832
February1st to 15thNight
20%24%32%19%3
753
16th to endNight
17%22%27%27%4
631
March1st to 15thNight
20%24%25%21%7%
720
16th to endNight
17%23%25%23%9%
768
April1st to 15thNight
17%23%26%25%6%
718
16th to endNight
11%21%24%31%10%1
552
May1st to 15thNight
15%18%19%28%15%2
517
16th to endNight
12%19%21%27%18%1
375
June1st to 15thNight
13%19%21%32%12%1
360
16th to endNight
8%18%17%36%18%
360
July1st to 15thNight
412%15%41%22%3
340
16th to endNight
9%16%11%39%20%2
520
August1st to 15thNight
7%10%10%38%29%3
539
16th to endNight
8%9%12%32%33%3
616
September1st to 15thNight
10%11%15%29%26%6%
720
16th to endNight
11%11%14%24%29%8%
717
October1st to 15thNight
18%13%21%23%19%3
720
16th to endNight
22%16%28%27%5%
768
November1st to 15thNight
16%19%24%24%13%2
760
16th to endNight
20%25%27%18%8%
780
December1st to 15thNight
25%25%25%19%4
780
16th to endNight
22%25%28%18%4
832
Page generated at 2018-02-13 20:46:09. Version ac04

Copyright 2018 A. Danko


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