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 2017-04-28.

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
60%
15138
20%
45422
19%
15101
62%
15101
30%
28100

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
50%
716
11%
2327
12%
716
52%
716
17%
1674
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%
534
25%
1602
20%
534
60%
534
31%
996
May1st to 15thNight
58%
494
23%
1484
18%
494
61%
494
33%
884
May16th to endNight
62%
513
16%
1541
16%
513
63%
513
30%
950
June1st to 15thNight
69%
465
22%
1293
20%
465
72%
465
45%
705
June16th to endNight
75%
330
31%
1182
36%
330
82%
330
57%
467
July1st to 15thNight
76%
343
22%
1273
29%
343
79%
343
42%
591
July16th to endNight
81%
522
27%
1467
28%
489
81%
489
53%
712
August1st to 15thNight
77%
494
30%
1476
26%
491
80%
491
47%
770
August16th to endNight
78%
525
36%
1575
30%
525
80%
525
51%
785
September1st to 15thNight
77%
630
31%
1779
27%
630
80%
630
51%
907
September16th to endNight
76%
656
35%
1815
29%
656
79%
656
53%
939
October1st to 15thNight
69%
660
28%
1919
24%
660
72%
660
42%
1065
October16th to endNight
67%
704
29%
2144
28%
704
70%
704
37%
1222
November1st to 15thNight
63%
700
22%
2275
23%
700
65%
700
30%
1359
November16th to endNight
59%
822
19%
2442
17%
822
61%
822
30%
1514
December1st to 15thNight
46%
900
9%
2520
7%
900
48%
900
21%
1816
December16th to endNight
39%
897
10%
2625
9%
897
40%
897
14%
2050

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%25%42445%7%48%
46263
Night
9%7%25%42445%6%46%
45611
TransparencyDay
35%5%11%19%17%10%
45951
Night
37%5%12%20%15%8%
45424
SeeingDay
10%7%22%33%20%4
5040
Night
13%313%39%26%4
15152

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%
1611
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%25%6%2445%7%42%
2305
May1st to 15thDay
8%5%35%435%5%5%8%44%
2136
16th to endDay
9%6%26%5%35%46%8%41%
2221
June1st to 15thDay
5%3144245%6%8%51%
2329
16th to endDay
2212112235%72%
2444
July1st to 15thDay
2212225%35%8%64%
2272
16th to endDay
222323347%67%
2285
August1st to 15thDay
2212322347%65%
2145
16th to endDay
4212322237%66%
2275
September1st to 15thDay
4213323446%62%
1849
16th to endDay
6%2221334468%
1815
October1st to 15thDay
9%42432445%6%50%
1711
16th to endDay
8%4243245%5%7%51%
1727
November1st to 15thDay
10%9%25%434346%46%
1584
16th to endDay
10%8%45%5%2335%6%42%
1504
December1st to 15thDay
14%12%5%8%7%34446%28%
1440
16th to endDay
15%14%49%5%24445%27%
1608
January1st to 15thNight
16%10%37%5%24446%34%
2327
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%26%434446%46%
1602
May1st to 15thNight
6%435%5%2445%8%47%
1484
16th to endNight
10%5%25%5%245%7%7%43%
1540
June1st to 15thNight
432431445%8%56%
1293
16th to endNight
312212346%72%
1182
July1st to 15thNight
3213425%45%7%59%
1356
16th to endNight
3213323446%64%
1575
August1st to 15thNight
32134335%6%9%55%
1485
16th to endNight
231232345%7%62%
1575
September1st to 15thNight
3313313346%63%
1779
16th to endNight
5%31221333467%
1815
October1st to 15thNight
7%414314447%55%
1919
16th to endNight
8%5%23323446%53%
2144
November1st to 15thNight
10%6%24424446%49%
2275
16th to endNight
7%7%24426%46%6%45%
2442
December1st to 15thNight
14%10%47%5%3445%5%34%
2520
16th to endNight
18%16%47%6%34345%25%
2625

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%19%15%2
1612
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
2305
May1st to 15thDay
36%410%24%18%5%
2136
16th to endDay
39%5%9%21%19%3
2224
June1st to 15thDay
28%5%11%20%26%7%
2329
16th to endDay
14%2311%31%35%
2444
July1st to 15thDay
18%3417%25%30%
2126
16th to endDay
17%2312%25%38%
2130
August1st to 15thDay
17%2415%25%34%
2130
16th to endDay
18%2316%32%24%
2275
September1st to 15thDay
21%45%16%31%20%
1849
16th to endDay
18%37%22%35%11%
1815
October1st to 15thDay
33%5%13%28%15%4
1711
16th to endDay
32%315%31%16%
1727
November1st to 15thDay
40%415%24%12%1
1584
16th to endDay
41%5%19%23%8%
1504
December1st to 15thDay
56%7%16%15%3
1440
16th to endDay
58%6%16%14%3
1608
January1st to 15thNight
50%8%18%17%31
2327
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
38%48%26%19%3
1602
May1st to 15thNight
33%5%9%24%19%7%
1485
16th to endNight
36%6%11%22%18%4
1541
June1st to 15thNight
24%411%19%31%8%
1293
16th to endNight
13%3212%31%37%
1182
July1st to 15thNight
23%25%14%22%31%
1273
16th to endNight
19%3213%21%39%
1467
August1st to 15thNight
23%35%12%20%34%
1476
16th to endNight
20%4412%31%27%
1575
September1st to 15thNight
21%26%14%27%27%
1779
16th to endNight
20%35%18%33%18%
1815
October1st to 15thNight
28%311%28%22%6%
1919
16th to endNight
31%48%32%21%2
2144
November1st to 15thNight
36%5%13%25%16%3
2275
16th to endNight
37%5%17%26%11%1
2442
December1st to 15thNight
51%5%21%16%4
2520
16th to endNight
61%5%14%15%3
2625

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
27%215%26%22%5%
90
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
15%15%27%25%11%3
259
May1st to 15thDay
11%12%30%30%12%2
228
16th to endDay
12%10%17%30%23%5%
266
June1st to 15thDay
6%6%18%35%26%7%
414
16th to endDay
3318%39%29%5%
389
July1st to 15thDay
3122%43%25%4
245
16th to endDay
25%21%42%26%1
271
August1st to 15thDay
4322%44%22%2
255
16th to endDay
4215%39%30%7%
268
September1st to 15thDay
47%24%36%21%5%
255
16th to endDay
6%5%17%32%30%7%
255
October1st to 15thDay
13%6%19%30%19%10%
151
16th to endDay
14%420%27%29%4
96
November1st to 15thDay
7%413%26%26%21%
90
16th to endDay
23%8%21%34%7%4
90
December1st to 15thDay
20%321%41%14%
90
16th to endDay
16%5%18%37%18%3
96
January1st to 15thNight
22%111%36%21%4
720
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
534
May1st to 15thNight
9%6%17%41%23%2
495
16th to endNight
12%412%32%33%4
515
June1st to 15thNight
5%415%43%30%1
465
16th to endNight
3114%42%33%4
330
July1st to 15thNight
319%37%45%2
343
16th to endNight
316%44%40%3
522
August1st to 15thNight
428%47%35%1
494
16th to endNight
419%41%38%4
525
September1st to 15thNight
5%27%41%36%6%
630
16th to endNight
7%28%33%35%12%
656
October1st to 15thNight
9%212%41%28%6%
660
16th to endNight
11%211%36%32%5%
704
November1st to 15thNight
13%213%38%29%3
700
16th to endNight
12%216%41%20%6%
822
December1st to 15thNight
19%417%39%18%1
900
16th to endNight
25%414%36%17%1
897
Page generated at 2017-04-29 07:45:06. Version ac04

Copyright 2017 A. Danko


Nocturne Observatory Clear Sky Chart | Charts Home