Nirvana
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Nirvana clear sky chart from 2005-11-05 to 2018-02-14.

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
26%
15289
13%
48847
7%
15258
34%
15258
16%
34696

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
14%
780
7%
2716
2%
776
20%
776
7%
2174
January16th to endNight
15%
832
10%
2798
4%
832
22%
832
10%
2150
February1st to 15thNight
13%
759
10%
2468
2%
757
22%
757
11%
1867
February16th to endNight
16%
631
14%
1988
4%
631
28%
631
13%
1438
March1st to 15thNight
16%
720
14%
2046
6%
720
24%
720
14%
1520
March16th to endNight
28%
768
20%
2071
9%
768
37%
768
23%
1400
April1st to 15thNight
19%
718
16%
1796
5%
718
26%
718
19%
1330
April16th to endNight
30%
630
17%
1710
7%
630
37%
630
22%
1189
May1st to 15thNight
36%
380
18%
1460
15%
380
45%
380
18%
948
May16th to endNight
32%
375
14%
1497
9%
374
46%
374
20%
905
June1st to 15thNight
32%
360
9%
1440
6%
360
42%
360
16%
935
June16th to endNight
40%
360
10%
1440
11%
360
47%
360
19%
902
July1st to 15thNight
46%
340
15%
1360
19%
340
53%
340
27%
744
July16th to endNight
51%
376
14%
1418
13%
354
58%
354
27%
799
August1st to 15thNight
52%
511
15%
1582
11%
509
56%
509
29%
1000
August16th to endNight
49%
672
20%
1818
9%
672
56%
672
36%
1107
September1st to 15thNight
42%
720
17%
1800
7%
720
46%
720
30%
1223
September16th to endNight
46%
717
23%
1979
15%
717
51%
717
31%
1263
October1st to 15thNight
29%
720
15%
2160
10%
720
37%
720
20%
1508
October16th to endNight
19%
768
11%
2352
4%
768
28%
768
12%
1802
November1st to 15thNight
26%
760
17%
2576
13%
760
35%
760
15%
1822
November16th to endNight
19%
780
10%
2730
7%
780
25%
780
10%
2111
December1st to 15thNight
12%
780
7%
2730
2%
780
18%
780
7%
2200
December16th to endNight
9%
832
9%
2912
3%
832
17%
832
7%
2359

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
17%9%47%6%34446%30%
49239
Night
16%10%46%5%3445%6%32%
49017
Cloud CoverDay
17%9%46%6%34446%31%
49249
Night
16%10%46%5%3445%6%32%
49022
TransparencyDay
53%5%11%18%9%1
48927
Night
51%6%12%19%10%
48847
SeeingDay
23%14%30%19%8%3
5826
Night
22%14%31%22%8%
15290

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
19%15%5%9%6%34445%20%
1552
16th to endDay
15%15%6%11%8%45%345%20%
1775
February1st to 15thDay
13%15%5%11%9%44445%21%
1695
16th to endDay
17%16%6%6%6%24435%26%
1485
March1st to 15thDay
15%12%5%8%8%45%445%26%
1902
16th to endDay
13%10%36%5%24435%38%
2152
April1st to 15thDay
21%10%45%5%23335%31%
2152
16th to endDay
20%9%36%323335%38%
2262
May1st to 15thDay
20%8%36%5%24445%32%
2490
16th to endDay
16%5%36%6%35%45%7%35%
2618
June1st to 15thDay
22%8%35%5%35%447%28%
2520
16th to endDay
17%6%26%5%35%5%6%7%32%
2520
July1st to 15thDay
13%6%26%6%35%5%6%9%35%
2520
16th to endDay
12%7%26%6%35%5%6%9%33%
2654
August1st to 15thDay
12%7%36%7%35%5%5%7%33%
2367
16th to endDay
14%6%25%6%35%5%5%8%36%
2370
September1st to 15thDay
18%6%245%34446%39%
2160
16th to endDay
16%5%345%34347%42%
1980
October1st to 15thDay
23%8%37%5%24346%29%
1800
16th to endDay
27%11%36%5%3444423%
1872
November1st to 15thDay
16%10%36%5%34346%32%
1609
16th to endDay
22%14%5%8%7%34435%21%
1560
December1st to 15thDay
20%18%6%10%6%3344416%
1560
16th to endDay
21%17%6%9%7%33335%19%
1664
January1st to 15thNight
18%14%7%9%7%35%5%35%18%
2716
16th to endNight
13%15%6%9%8%34446%23%
2798
February1st to 15thNight
13%14%6%9%7%35%46%6%23%
2466
16th to endNight
15%12%46%5%35%5%6%7%28%
1988
March1st to 15thNight
16%12%5%8%6%24345%31%
2034
16th to endNight
14%7%35%5%34445%41%
2071
April1st to 15thNight
20%8%35%5%2435%5%34%
1796
16th to endNight
17%7%26%5%24446%38%
1710
May1st to 15thNight
19%7%35%424346%37%
1460
16th to endNight
13%6%25%43446%7%40%
1495
June1st to 15thNight
17%7%35%5%2345%7%36%
1440
16th to endNight
14%6%25%5%35%5%6%7%38%
1440
July1st to 15thNight
9%425%43445%7%48%
1440
16th to endNight
9%324435%45%9%46%
1514
August1st to 15thNight
8%425%435%5%6%8%43%
1592
16th to endNight
9%42442345%7%50%
1818
September1st to 15thNight
13%5%26%5%3435%6%43%
1800
16th to endNight
16%5%23313445%48%
1979
October1st to 15thNight
21%7%36%32445%5%35%
2160
16th to endNight
23%11%46%6%33447%25%
2352
November1st to 15thNight
16%11%46%5%3445%6%32%
2576
16th to endNight
21%13%5%6%6%44445%23%
2730
December1st to 15thNight
19%18%6%7%6%34346%18%
2730
16th to endNight
21%15%6%9%7%3434419%
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
19%16%5%9%5%34345%21%
1552
16th to endDay
14%14%6%11%8%45%335%20%
1775
February1st to 15thDay
14%16%6%10%8%34445%21%
1695
16th to endDay
18%15%6%6%5%33435%27%
1485
March1st to 15thDay
16%12%48%7%36%44426%
1913
16th to endDay
14%9%35%5%34345%39%
2151
April1st to 15thDay
22%9%45%5%34335%32%
2152
16th to endDay
20%8%36%423345%37%
2262
May1st to 15thDay
20%7%36%5%2445%5%33%
2490
16th to endDay
15%5%36%6%35%45%7%35%
2618
June1st to 15thDay
22%7%35%5%36%45%7%28%
2520
16th to endDay
17%5%35%6%36%46%8%32%
2520
July1st to 15thDay
13%6%35%6%45%5%6%9%35%
2520
16th to endDay
11%7%36%6%45%5%6%8%34%
2654
August1st to 15thDay
11%7%37%6%45%6%5%7%33%
2367
16th to endDay
14%6%25%5%45%46%7%37%
2370
September1st to 15thDay
17%6%35%424446%39%
2160
16th to endDay
15%6%25%433346%42%
1980
October1st to 15thDay
22%8%46%5%33347%30%
1800
16th to endDay
27%10%36%6%34445%23%
1872
November1st to 15thDay
16%9%37%6%25%446%32%
1609
16th to endDay
22%13%5%7%7%345%35%21%
1560
December1st to 15thDay
20%18%5%10%6%3444417%
1560
16th to endDay
21%17%6%8%7%34335%19%
1664
January1st to 15thNight
19%14%6%9%8%34435%19%
2716
16th to endNight
13%15%5%9%7%35%346%24%
2798
February1st to 15thNight
12%14%6%9%6%35%46%6%23%
2459
16th to endNight
14%13%46%5%36%5%5%7%28%
1988
March1st to 15thNight
17%11%5%7%5%33345%30%
2046
16th to endNight
14%7%45%5%24435%42%
2071
April1st to 15thNight
20%8%345%24346%34%
1796
16th to endNight
16%8%25%5%24447%38%
1710
May1st to 15thNight
19%7%35%423447%38%
1460
16th to endNight
13%6%24435%45%7%41%
1495
June1st to 15thNight
16%7%37%5%2345%8%35%
1440
16th to endNight
14%5%35%5%345%5%9%37%
1440
July1st to 15thNight
8%5%245%25%448%48%
1440
16th to endNight
8%3145%35%46%9%46%
1514
August1st to 15thNight
9%5%25%5%35%6%5%8%43%
1592
16th to endNight
9%42442346%7%49%
1818
September1st to 15thNight
13%5%25%5%4345%6%44%
1800
16th to endNight
16%5%2331335%5%48%
1979
October1st to 15thNight
20%7%26%42445%5%35%
2160
16th to endNight
23%11%36%6%34446%26%
2352
November1st to 15thNight
17%10%46%5%3445%5%33%
2576
16th to endNight
22%12%46%6%35%45%5%23%
2730
December1st to 15thNight
20%16%6%8%5%34446%19%
2730
16th to endNight
21%14%6%8%7%3444420%
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
65%5%9%11%7%1
1553
16th to endDay
66%5%7%10%8%1
1775
February1st to 15thDay
64%411%14%5%
1697
16th to endDay
60%49%13%11%1
1485
March1st to 15thDay
60%412%14%6%1
1913
16th to endDay
47%49%19%15%5%
2152
April1st to 15thDay
55%47%17%12%2
2152
16th to endDay
49%37%19%16%2
2262
May1st to 15thDay
51%5%9%16%14%2
2490
16th to endDay
47%6%12%19%12%1
2622
June1st to 15thDay
54%5%10%18%9%
2520
16th to endDay
48%7%12%18%12%1
2520
July1st to 15thDay
43%6%12%26%10%
2371
16th to endDay
46%7%15%21%8%
2487
August1st to 15thDay
48%8%14%19%9%
2353
16th to endDay
44%6%15%23%8%
2370
September1st to 15thDay
44%5%10%26%11%
2160
16th to endDay
42%6%11%28%11%
1980
October1st to 15thDay
54%5%10%19%9%
1800
16th to endDay
63%6%10%14%5%
1872
November1st to 15thDay
51%6%15%17%8%
1609
16th to endDay
65%5%9%11%6%1
1560
December1st to 15thDay
70%5%10%10%3
1560
16th to endDay
68%48%11%6%
1664
January1st to 15thNight
66%5%9%11%5%
2716
16th to endNight
61%5%9%13%8%
2798
February1st to 15thNight
60%5%14%14%5%
2468
16th to endNight
52%6%11%18%10%
1988
March1st to 15thNight
55%410%19%8%1
2046
16th to endNight
44%410%20%16%2
2071
April1st to 15thNight
51%48%20%13%1
1796
16th to endNight
45%6%8%19%17%2
1710
May1st to 15thNight
46%5%8%19%15%3
1460
16th to endNight
40%6%14%20%15%2
1497
June1st to 15thNight
46%6%13%20%12%
1440
16th to endNight
42%6%13%23%12%
1440
July1st to 15thNight
32%6%13%28%17%1
1360
16th to endNight
33%7%18%26%13%
1418
August1st to 15thNight
35%8%17%25%11%
1582
16th to endNight
31%7%16%33%11%
1818
September1st to 15thNight
39%7%14%26%11%
1800
16th to endNight
36%5%12%35%9%
1979
October1st to 15thNight
49%5%12%20%12%
2160
16th to endNight
58%6%13%15%6%
2352
November1st to 15thNight
51%6%12%18%9%1
2576
16th to endNight
61%6%11%15%4
2730
December1st to 15thNight
66%6%11%11%3
2730
16th to endNight
67%5%8%10%6%
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
30%25%24%15%4
90
16th to endDay
37%21%29%9%1
122
February1st to 15thDay
31%28%33%6%
130
16th to endDay
38%18%31%10%2
144
March1st to 15thDay
25%18%33%17%4
270
16th to endDay
26%17%32%15%7%1
288
April1st to 15thDay
28%21%29%13%7%
270
16th to endDay
24%21%23%19%8%2
270
May1st to 15thDay
33%10%27%17%5%5%
288
16th to endDay
21%14%36%16%8%2
331
June1st to 15thDay
24%13%34%17%10%
315
16th to endDay
15%14%33%23%9%2
315
July1st to 15thDay
14%8%31%29%12%3
305
16th to endDay
15%7%35%25%11%4
326
August1st to 15thDay
12%5%30%33%10%7%
313
16th to endDay
16%6%27%29%11%9%
332
September1st to 15thDay
17%8%28%20%14%10%
315
16th to endDay
16%8%25%22%18%8%
314
October1st to 15thDay
26%14%29%18%9%2
315
16th to endDay
33%16%29%16%3
324
November1st to 15thDay
25%12%32%21%5%1
173
16th to endDay
30%22%36%8%11
90
December1st to 15thDay
32%23%26%13%31
90
16th to endDay
37%26%33%21
96
January1st to 15thNight
28%20%30%15%4
780
16th to endNight
21%20%34%17%4
832
February1st to 15thNight
21%21%38%15%2
760
16th to endNight
19%21%39%15%3
631
March1st to 15thNight
25%19%33%19%1
720
16th to endNight
19%16%32%20%8%1
768
April1st to 15thNight
25%18%32%18%4
718
16th to endNight
22%15%29%23%9%
630
May1st to 15thNight
24%8%27%30%8%1
380
16th to endNight
16%7%38%26%10%
375
June1st to 15thNight
19%13%29%26%9%1
360
16th to endNight
17%6%31%32%10%
360
July1st to 15thNight
7%5%32%37%15%
340
16th to endNight
9%230%41%15%
376
August1st to 15thNight
11%423%38%18%2
511
16th to endNight
10%5%30%30%20%2
672
September1st to 15thNight
16%5%31%25%18%3
720
16th to endNight
20%7%23%25%20%3
717
October1st to 15thNight
26%11%28%21%10%1
720
16th to endNight
30%15%30%18%5%
768
November1st to 15thNight
23%14%29%22%8%1
760
16th to endNight
31%17%27%16%6%
780
December1st to 15thNight
30%18%32%14%3
780
16th to endNight
32%14%35%14%1
832
Page generated at 2018-02-15 10:58:41. Version ac04

Copyright 2018 A. Danko


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