Nocturne Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Nocturne Observatory clear sky chart from 2005-11-05 to 2018-01-12.

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
61%
16041
21%
48141
19%
16004
63%
16004
31%
29559

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
51%
760
11%
2471
12%
760
52%
760
18%
1766
January16th to endNight
48%
768
12%
2496
12%
768
50%
768
18%
1806
February1st to 15thNight
51%
697
10%
2287
12%
696
53%
696
18%
1630
February16th to endNight
50%
632
16%
1912
16%
632
52%
632
24%
1269
March1st to 15thNight
57%
720
17%
2033
16%
720
59%
720
27%
1350
March16th to endNight
53%
768
16%
2112
13%
768
55%
768
27%
1429
April1st to 15thNight
51%
648
17%
1843
13%
648
53%
648
27%
1210
April16th to endNight
58%
540
25%
1620
21%
540
60%
540
31%
1004
May1st to 15thNight
60%
539
22%
1619
18%
539
62%
539
34%
945
May16th to endNight
63%
561
17%
1685
17%
561
64%
561
31%
1030
June1st to 15thNight
68%
507
21%
1410
19%
507
71%
507
45%
772
June16th to endNight
77%
360
33%
1290
40%
360
83%
360
57%
507
July1st to 15thNight
76%
376
22%
1396
28%
376
79%
376
42%
649
July16th to endNight
81%
564
28%
1593
28%
531
81%
531
52%
777
August1st to 15thNight
78%
539
29%
1611
25%
536
80%
536
48%
837
August16th to endNight
79%
573
38%
1719
32%
573
81%
573
52%
851
September1st to 15thNight
79%
687
29%
1941
25%
687
81%
687
52%
981
September16th to endNight
75%
716
36%
1980
30%
716
78%
716
51%
1035
October1st to 15thNight
69%
720
27%
2094
23%
720
72%
720
43%
1153
October16th to endNight
69%
768
32%
2339
30%
768
72%
768
39%
1304
November1st to 15thNight
62%
760
22%
2470
22%
760
64%
760
30%
1481
November16th to endNight
60%
891
19%
2646
18%
891
61%
891
30%
1646
December1st to 15thNight
49%
975
10%
2730
8%
975
51%
975
23%
1920
December16th to endNight
40%
972
10%
2844
8%
972
41%
972
15%
2207

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
8%6%2442445%7%49%
49184
Night
9%7%25%42445%6%47%
48330
TransparencyDay
34%411%19%17%10%
48872
Night
36%5%12%21%15%8%
48143
SeeingDay
10%6%21%33%22%5%
5996
Night
12%313%39%26%3
16055

By Month

Percentage Cloud Cover SW (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
13%13%47%5%34445%31%
1710
16th to endDay
14%13%37%5%3445%6%28%
1728
February1st to 15thDay
15%12%46%42345%6%34%
1575
16th to endDay
8%14%48%5%345%5%6%32%
1560
March1st to 15thDay
7%7%35%6%2447%8%40%
1926
16th to endDay
10%12%5%6%6%245%5%8%32%
2112
April1st to 15thDay
9%9%35%5%35%5%6%7%38%
2101
16th to endDay
9%7%26%6%2445%7%42%
2340
May1st to 15thDay
7%5%245%35%5%5%8%46%
2331
16th to endDay
8%5%26%435%46%8%43%
2429
June1st to 15thDay
5%3134245%6%8%52%
2542
16th to endDay
222112235%73%
2666
July1st to 15thDay
2212225%35%8%63%
2478
16th to endDay
3212323346%65%
2467
August1st to 15thDay
2212322447%65%
2340
16th to endDay
3212322237%66%
2483
September1st to 15thDay
4213313446%63%
2016
16th to endDay
7%212213345%65%
1980
October1st to 15thDay
9%42432445%6%51%
1866
16th to endDay
8%42432345%7%53%
1884
November1st to 15thDay
10%9%25%434345%45%
1719
16th to endDay
10%8%45%5%2335%7%42%
1629
December1st to 15thDay
13%11%48%7%34446%31%
1560
16th to endDay
15%14%48%5%34445%28%
1742
January1st to 15thNight
17%9%37%5%2345%6%33%
2471
16th to endNight
16%12%37%5%34446%32%
2496
February1st to 15thNight
14%12%36%5%24446%34%
2277
16th to endNight
9%11%36%5%3345%6%38%
1912
March1st to 15thNight
9%10%35%4245%5%7%38%
2033
16th to endNight
8%8%35%6%35%5%6%6%39%
2112
April1st to 15thNight
8%8%36%5%25%5%46%42%
1843
16th to endNight
10%5%36%43445%6%46%
1620
May1st to 15thNight
6%435%5%2445%7%50%
1619
16th to endNight
10%5%245%245%6%7%44%
1684
June1st to 15thNight
5%325%31445%8%56%
1410
16th to endNight
212212346%73%
1290
July1st to 15thNight
3213425%45%7%58%
1479
16th to endNight
321332345%6%63%
1701
August1st to 15thNight
32133335%6%9%55%
1620
16th to endNight
231232335%7%63%
1719
September1st to 15thNight
3313313346%64%
1941
16th to endNight
6%312213335%66%
1980
October1st to 15thNight
7%414324447%56%
2094
16th to endNight
7%5%13323446%55%
2339
November1st to 15thNight
10%6%24424447%48%
2470
16th to endNight
8%7%24425%5%6%6%45%
2646
December1st to 15thNight
13%10%37%5%3445%6%36%
2730
16th to endNight
17%15%47%6%34346%25%
2844

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
54%7%18%15%3
1711
16th to endDay
54%9%15%15%4
1728
February1st to 15thDay
50%7%18%17%5%
1575
16th to endDay
49%7%17%18%41
1560
March1st to 15thDay
39%8%19%22%8%1
1926
16th to endDay
49%5%15%20%8%
2112
April1st to 15thDay
43%415%23%12%
2101
16th to endDay
40%310%25%17%1
2340
May1st to 15thDay
35%410%25%18%5%
2331
16th to endDay
38%410%22%19%3
2432
June1st to 15thDay
27%410%22%26%7%
2542
16th to endDay
13%2311%31%36%
2666
July1st to 15thDay
18%3416%25%30%
2332
16th to endDay
19%2411%24%36%
2312
August1st to 15thDay
18%3415%24%33%
2325
16th to endDay
18%2317%32%24%
2483
September1st to 15thDay
20%45%16%30%22%
2016
16th to endDay
20%38%22%33%10%
1980
October1st to 15thDay
32%412%28%17%4
1866
16th to endDay
30%316%30%19%
1884
November1st to 15thDay
41%5%14%25%12%1
1719
16th to endDay
40%5%21%23%8%
1629
December1st to 15thDay
54%7%17%16%5%
1560
16th to endDay
57%6%16%14%4
1742
January1st to 15thNight
50%8%17%18%41
2471
16th to endNight
52%6%17%15%6%1
2496
February1st to 15thNight
50%7%14%20%7%
2288
16th to endNight
44%415%26%6%1
1912
March1st to 15thNight
43%5%16%24%9%
2033
16th to endNight
43%5%14%23%10%2
2112
April1st to 15thNight
42%412%26%10%3
1843
16th to endNight
37%48%26%19%3
1620
May1st to 15thNight
31%5%9%26%19%6%
1620
16th to endNight
35%5%11%23%19%4
1685
June1st to 15thNight
25%410%19%31%8%
1410
16th to endNight
12%3212%31%37%
1290
July1st to 15thNight
23%25%14%23%29%
1396
16th to endNight
19%3313%22%37%
1593
August1st to 15thNight
23%35%12%20%34%
1611
16th to endNight
19%4412%30%28%
1719
September1st to 15thNight
21%26%14%26%28%
1941
16th to endNight
21%35%19%32%16%
1980
October1st to 15thNight
27%310%28%23%6%
2094
16th to endNight
29%48%31%23%2
2339
November1st to 15thNight
36%5%12%25%15%3
2470
16th to endNight
37%5%17%26%10%1
2646
December1st to 15thNight
48%5%21%18%5%
2730
16th to endNight
60%5%14%15%3
2844

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
25%413%26%25%5%
123
16th to endDay
32%49%30%21%2
96
February1st to 15thDay
30%411%21%24%8%
90
16th to endDay
14%12%35%26%6%4
219
March1st to 15thDay
13%9%31%31%14%
270
16th to endDay
16%9%36%26%9%
288
April1st to 15thDay
13%13%30%26%13%2
269
16th to endDay
16%15%28%25%11%3
270
May1st to 15thDay
9%11%29%31%14%2
288
16th to endDay
11%9%18%29%24%6%
330
June1st to 15thDay
7%6%17%35%27%6%
489
16th to endDay
3319%38%30%5%
461
July1st to 15thDay
3118%41%27%7%
305
16th to endDay
3419%43%26%2
327
August1st to 15thDay
4219%48%21%2
315
16th to endDay
3212%37%36%8%
332
September1st to 15thDay
46%20%33%24%10%
315
16th to endDay
10%419%30%27%7%
315
October1st to 15thDay
13%5%25%28%17%8%
201
16th to endDay
11%320%26%32%5%
144
November1st to 15thDay
14%414%31%21%14%
135
16th to endDay
22%7%16%33%17%2
135
December1st to 15thDay
15%215%40%20%4
135
16th to endDay
20%318%41%13%2
144
January1st to 15thNight
22%111%36%22%4
764
16th to endNight
22%310%33%25%4
768
February1st to 15thNight
21%211%39%22%2
704
16th to endNight
14%418%43%15%3
632
March1st to 15thNight
15%313%45%18%3
720
16th to endNight
13%5%19%43%16%1
768
April1st to 15thNight
12%5%21%38%19%2
648
16th to endNight
12%417%41%21%2
540
May1st to 15thNight
8%6%17%41%23%2
540
16th to endNight
12%412%32%33%4
563
June1st to 15thNight
6%415%41%31%1
507
16th to endNight
3113%43%33%4
360
July1st to 15thNight
318%35%46%2
376
16th to endNight
316%43%41%3
564
August1st to 15thNight
428%46%36%1
539
16th to endNight
419%39%41%4
573
September1st to 15thNight
5%17%38%39%7%
687
16th to endNight
7%28%35%34%11%
716
October1st to 15thNight
8%212%41%27%6%
720
16th to endNight
11%210%38%32%5%
768
November1st to 15thNight
14%213%40%27%3
760
16th to endNight
12%215%42%20%5%
891
December1st to 15thNight
18%415%40%19%1
975
16th to endNight
25%414%38%15%1
972
Page generated at 2018-01-12 20:01:25. Version ac04

Copyright 2018 A. Danko


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