New Hamburg Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the New Hamburg Observatory clear sky chart from 2005-11-05 to 2017-09-20.

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
34%
14897
15%
46612
10%
14860
40%
14860
19%
32587

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
13%
717
10%
2410
4%
716
20%
716
8%
1938
January16th to endNight
16%
768
11%
2496
4%
768
23%
768
9%
2008
February1st to 15thNight
15%
701
8%
2287
2%
701
23%
701
10%
1797
February16th to endNight
22%
631
11%
1976
4%
631
30%
631
13%
1482
March1st to 15thNight
22%
720
14%
2001
7%
720
29%
720
16%
1501
March16th to endNight
32%
768
20%
2112
11%
768
40%
768
23%
1456
April1st to 15thNight
26%
696
15%
1832
7%
696
32%
696
21%
1330
April16th to endNight
37%
540
21%
1620
10%
540
45%
540
25%
1051
May1st to 15thNight
40%
540
17%
1620
11%
540
47%
540
25%
1072
May16th to endNight
45%
390
17%
1513
14%
390
55%
390
27%
834
June1st to 15thNight
49%
360
14%
1408
15%
360
57%
360
25%
804
June16th to endNight
52%
360
16%
1260
15%
360
59%
360
29%
725
July1st to 15thNight
64%
341
19%
1234
23%
341
69%
341
38%
616
July16th to endNight
59%
564
16%
1595
12%
531
63%
531
35%
937
August1st to 15thNight
65%
539
18%
1609
14%
536
69%
536
36%
928
August16th to endNight
61%
593
24%
1739
15%
593
66%
593
36%
1025
September1st to 15thNight
54%
720
22%
1866
13%
720
57%
720
34%
1180
September16th to endNight
56%
677
21%
1870
15%
677
59%
677
32%
1167
October1st to 15thNight
41%
660
19%
1972
15%
660
47%
660
24%
1309
October16th to endNight
23%
704
14%
2119
8%
704
32%
704
16%
1571
November1st to 15thNight
33%
700
18%
2345
15%
700
39%
700
18%
1600
November16th to endNight
24%
720
10%
2520
7%
720
29%
720
11%
1911
December1st to 15thNight
14%
720
6%
2520
2%
720
18%
720
7%
2081
December16th to endNight
10%
768
7%
2688
2%
768
15%
768
5%
2264

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
15%9%47%6%35%5%5%7%29%
48223
Night
14%9%47%6%35%45%7%32%
46788
Cloud CoverDay
15%9%47%6%35%45%7%30%
48233
Night
15%9%47%5%35%45%7%32%
46792
TransparencyDay
53%411%19%9%
47918
Night
51%411%20%10%1
46612
SeeingDay
18%7%25%24%15%7%
5643
Night
19%9%28%28%12%1
14904

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%14%6%11%8%35%446%15%
1528
16th to endDay
12%17%10%13%8%5%5%445%12%
1728
February1st to 15thDay
15%17%6%11%8%47%446%14%
1575
16th to endDay
15%15%6%10%7%45%45%5%18%
1494
March1st to 15thDay
15%13%6%9%6%45%445%24%
1947
16th to endDay
14%10%6%7%6%3445%6%29%
2112
April1st to 15thDay
20%10%5%6%43446%7%28%
2126
16th to endDay
18%10%25%423436%37%
2340
May1st to 15thDay
18%7%26%5%34347%34%
2331
16th to endDay
13%6%346%345%6%8%37%
2602
June1st to 15thDay
14%5%25%5%35%5%6%8%37%
2548
16th to endDay
13%5%25%6%25%6%6%10%36%
2700
July1st to 15thDay
9%5%246%35%6%7%9%38%
2647
16th to endDay
11%5%25%6%47%6%6%9%36%
2465
August1st to 15thDay
8%5%27%7%46%6%7%9%35%
2340
16th to endDay
11%6%36%5%35%6%5%8%36%
2450
September1st to 15thDay
13%7%35%435%5%7%9%35%
2094
16th to endDay
16%6%25%5%2445%7%39%
1859
October1st to 15thDay
19%8%36%6%34446%31%
1658
16th to endDay
24%12%37%6%345%45%21%
1752
November1st to 15thDay
13%12%36%5%25%45%6%31%
1511
16th to endDay
17%16%6%8%6%45%46%5%18%
1440
December1st to 15thDay
17%16%8%12%8%45%43411%
1440
16th to endDay
19%18%7%13%8%45%4449%
1536
January1st to 15thNight
21%13%6%9%7%45%45%5%16%
2410
16th to endNight
14%14%8%12%8%35%446%17%
2496
February1st to 15thNight
14%13%7%10%7%36%5%45%20%
2285
16th to endNight
15%11%49%9%35%45%7%23%
1976
March1st to 15thNight
18%9%27%7%35%45%6%28%
1989
16th to endNight
14%8%45%5%34445%39%
2112
April1st to 15thNight
19%8%36%6%24447%32%
1832
16th to endNight
12%7%36%5%34447%40%
1620
May1st to 15thNight
15%6%36%5%2445%8%37%
1620
16th to endNight
10%42442445%7%47%
1511
June1st to 15thNight
11%5%244345%7%8%42%
1408
16th to endNight
9%335%5%3446%9%45%
1260
July1st to 15thNight
421332446%8%55%
1307
16th to endNight
7%4244245%5%9%47%
1703
August1st to 15thNight
6%3245%345%6%10%47%
1620
16th to endNight
6%5%245%2446%6%51%
1739
September1st to 15thNight
11%4235%3435%7%47%
1866
16th to endNight
12%5%144345%5%7%45%
1870
October1st to 15thNight
17%7%35%5%24348%37%
1972
16th to endNight
22%8%37%6%3445%7%27%
2119
November1st to 15thNight
14%9%36%5%25%45%7%33%
2345
16th to endNight
19%12%6%8%5%35%45%6%21%
2520
December1st to 15thNight
19%16%7%9%7%45%445%15%
2520
16th to endNight
20%15%8%13%6%35%445%12%
2688

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%14%6%11%8%35%345%16%
1528
16th to endDay
12%17%10%14%8%45%435%13%
1728
February1st to 15thDay
15%16%7%11%7%46%445%15%
1575
16th to endDay
15%15%6%10%7%44446%19%
1494
March1st to 15thDay
16%13%5%8%6%35%445%24%
1958
16th to endDay
14%11%5%7%6%35%446%30%
2111
April1st to 15thDay
19%11%45%5%2445%6%28%
2126
16th to endDay
19%10%25%423336%38%
2340
May1st to 15thDay
19%7%26%5%34448%34%
2331
16th to endDay
13%6%346%35%46%8%37%
2602
June1st to 15thDay
15%425%5%35%6%5%8%37%
2548
16th to endDay
13%5%246%35%5%6%10%36%
2700
July1st to 15thDay
9%4246%36%6%6%9%39%
2647
16th to endDay
11%5%25%6%47%6%6%9%36%
2465
August1st to 15thDay
9%426%6%46%6%7%8%36%
2340
16th to endDay
12%6%35%5%35%6%5%8%36%
2450
September1st to 15thDay
14%7%25%5%345%7%8%35%
2094
16th to endDay
16%5%35%5%2445%7%39%
1859
October1st to 15thDay
20%8%36%6%34445%32%
1658
16th to endDay
24%11%37%6%34445%21%
1752
November1st to 15thDay
14%12%36%5%35%45%6%31%
1511
16th to endDay
18%15%6%7%7%35%45%5%19%
1440
December1st to 15thDay
17%17%8%12%9%45%5%4412%
1440
16th to endDay
20%17%8%12%8%35%35%49%
1536
January1st to 15thNight
21%13%6%9%7%44446%17%
2410
16th to endNight
14%14%8%11%7%35%45%6%17%
2496
February1st to 15thNight
14%13%8%10%7%36%5%45%21%
2278
16th to endNight
15%11%410%7%35%45%7%24%
1976
March1st to 15thNight
18%9%38%6%35%45%6%28%
2001
16th to endNight
14%8%45%425%345%39%
2112
April1st to 15thNight
20%8%36%6%24447%32%
1832
16th to endNight
12%7%25%5%3445%7%40%
1620
May1st to 15thNight
15%7%35%5%34448%37%
1619
16th to endNight
11%425%424448%47%
1511
June1st to 15thNight
11%424425%47%7%43%
1408
16th to endNight
9%335%4345%6%9%45%
1260
July1st to 15thNight
431342436%9%56%
1307
16th to endNight
7%5%2442445%10%47%
1703
August1st to 15thNight
6%315%5%3346%9%49%
1620
16th to endNight
7%43443445%7%51%
1739
September1st to 15thNight
12%423435%35%8%47%
1866
16th to endNight
12%5%134345%5%7%44%
1870
October1st to 15thNight
17%6%35%5%24348%38%
1972
16th to endNight
22%8%36%6%35%45%6%27%
2119
November1st to 15thNight
14%9%36%5%25%45%7%33%
2345
16th to endNight
20%12%5%7%5%35%5%5%7%22%
2520
December1st to 15thNight
19%15%6%9%7%46%445%16%
2520
16th to endNight
20%15%8%12%7%35%445%13%
2688

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
70%48%12%4
1529
16th to endDay
74%37%10%3
1728
February1st to 15thDay
69%47%13%4
1577
16th to endDay
65%410%13%5%
1494
March1st to 15thDay
62%311%15%6%
1958
16th to endDay
54%410%17%11%1
2112
April1st to 15thDay
54%411%19%10%
2126
16th to endDay
48%311%20%14%2
2340
May1st to 15thDay
49%310%24%11%
2331
16th to endDay
43%413%23%13%1
2606
June1st to 15thDay
43%5%13%25%12%
2548
16th to endDay
43%5%13%24%13%
2700
July1st to 15thDay
38%5%11%25%17%1
2492
16th to endDay
43%6%12%23%12%2
2310
August1st to 15thDay
42%5%16%22%12%1
2327
16th to endDay
43%5%12%24%12%1
2450
September1st to 15thDay
44%415%23%11%
2094
16th to endDay
43%413%27%9%
1859
October1st to 15thDay
53%311%16%13%1
1658
16th to endDay
64%313%13%4
1752
November1st to 15thDay
52%5%13%17%9%
1511
16th to endDay
66%411%13%3
1440
December1st to 15thDay
75%5%10%7%1
1440
16th to endDay
77%47%8%2
1536
January1st to 15thNight
68%39%11%6%
2410
16th to endNight
68%39%14%4
2496
February1st to 15thNight
65%39%15%5%
2287
16th to endNight
59%312%15%7%
1976
March1st to 15thNight
56%411%19%7%
2001
16th to endNight
48%38%23%13%2
2112
April1st to 15thNight
52%39%21%13%
1832
16th to endNight
43%39%20%19%3
1620
May1st to 15thNight
44%49%25%13%2
1620
16th to endNight
36%315%27%14%3
1513
June1st to 15thNight
37%412%27%15%2
1408
16th to endNight
35%5%14%25%17%
1260
July1st to 15thNight
25%5%11%32%22%2
1234
16th to endNight
32%5%15%26%17%3
1595
August1st to 15thNight
31%5%16%31%13%1
1609
16th to endNight
32%411%31%17%2
1739
September1st to 15thNight
36%312%29%16%1
1866
16th to endNight
37%412%30%14%
1870
October1st to 15thNight
45%410%25%14%
1972
16th to endNight
56%313%18%7%
2119
November1st to 15thNight
49%411%19%12%1
2345
16th to endNight
62%312%15%5%
2520
December1st to 15thNight
71%410%10%3
2520
16th to endNight
73%48%9%3
2688

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
21%22%42%6%6%1
76
16th to endDay
33%13%39%13%
96
February1st to 15thDay
23%20%45%10%1
90
16th to endDay
25%20%41%7%3
81
March1st to 15thDay
25%12%29%24%7%
248
16th to endDay
25%7%32%22%9%2
288
April1st to 15thDay
24%11%30%20%11%1
270
16th to endDay
23%7%30%20%12%5%
270
May1st to 15thDay
21%7%26%22%14%7%
288
16th to endDay
15%6%29%26%13%7%
331
June1st to 15thDay
19%6%20%31%17%4
343
16th to endDay
14%6%29%30%14%4
495
July1st to 15thDay
12%6%22%27%22%9%
430
16th to endDay
11%219%30%23%11%
326
August1st to 15thDay
10%115%29%24%17%
313
16th to endDay
15%415%21%23%19%
332
September1st to 15thDay
12%316%24%30%13%
315
16th to endDay
18%317%22%21%16%
270
October1st to 15thDay
19%7%22%27%17%5%
255
16th to endDay
27%10%29%26%5%
264
November1st to 15thDay
12%16%30%23%12%3
78
16th to endDay
30%11%40%8%8%1
60
December1st to 15thDay
35%21%30%8%5%
60
16th to endDay
31%18%43%6%
64
January1st to 15thNight
27%16%34%16%4
720
16th to endNight
22%13%35%24%4
768
February1st to 15thNight
21%16%36%22%3
704
16th to endNight
22%13%32%25%6%
631
March1st to 15thNight
23%12%34%23%5%
720
16th to endNight
17%10%33%26%11%
768
April1st to 15thNight
23%10%33%25%6%
696
16th to endNight
15%9%32%32%10%1
540
May1st to 15thNight
17%5%27%31%16%1
540
16th to endNight
13%428%34%18%1
391
June1st to 15thNight
13%325%43%14%
360
16th to endNight
11%325%43%15%
360
July1st to 15thNight
4121%48%21%2
341
16th to endNight
10%218%44%20%3
564
August1st to 15thNight
7%113%45%27%4
539
16th to endNight
9%216%36%28%5%
593
September1st to 15thNight
13%5%19%32%23%5%
720
16th to endNight
15%317%31%25%6%
677
October1st to 15thNight
19%6%24%29%17%3
660
16th to endNight
28%9%30%25%5%
704
November1st to 15thNight
18%10%30%27%12%1
700
16th to endNight
27%12%27%23%8%
720
December1st to 15thNight
28%15%33%19%3
720
16th to endNight
28%16%33%16%4
768
Page generated at 2017-09-21 07:18:20. Version ac04

Copyright 2017 A. Danko


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