Embro Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Embro Observatory clear sky chart from 2005-11-06 to 2024-01-14.

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
34%
22973
15%
74373
10%
22925
40%
22925
18%
51862

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 10thNight
14%
758
12%
2564
5%
757
23%
757
9%
2010
January11th to 20thNight
15%
735
8%
2386
4%
735
20%
735
7%
1983
January21st to endNight
20%
792
12%
2574
5%
792
28%
792
10%
2012
February1st to 10thNight
15%
720
8%
2340
3%
720
21%
720
9%
1854
February11th to 20thNight
19%
701
11%
2274
4%
699
28%
699
12%
1722
February21st to endNight
19%
592
12%
1798
4%
592
27%
592
12%
1378
March1st to 10thNight
24%
720
18%
2017
9%
720
32%
720
19%
1425
March11th to 20thNight
25%
720
19%
1980
9%
720
34%
720
20%
1405
March21st to endNight
29%
792
19%
2178
10%
792
36%
792
20%
1551
April1st to 10thNight
27%
720
16%
1899
7%
720
33%
720
21%
1361
April11th to 20thNight
31%
583
20%
1647
8%
583
39%
583
23%
1123
April21st to endNight
34%
540
19%
1620
8%
540
43%
540
22%
1081
May1st to 10thNight
38%
540
17%
1620
10%
540
44%
540
25%
1071
May11th to 20thNight
42%
495
19%
1557
12%
495
50%
495
26%
968
May21st to endNight
51%
388
19%
1551
19%
388
60%
388
31%
806
June1st to 10thNight
48%
360
15%
1440
16%
360
57%
360
26%
789
June11th to 20thNight
46%
360
18%
1306
17%
360
58%
360
28%
730
June21st to endNight
53%
360
19%
1260
19%
360
62%
360
29%
720
July1st to 10thNight
66%
350
21%
1225
24%
350
71%
350
39%
623
July11th to 20thNight
60%
470
19%
1497
19%
470
65%
470
37%
826
July21st to endNight
62%
591
17%
1672
14%
558
65%
558
35%
979
August1st to 10thNight
65%
537
20%
1600
16%
534
68%
534
35%
937
August11th to 20thNight
67%
534
24%
1598
18%
534
70%
534
38%
908
August21st to endNight
57%
618
24%
1806
15%
618
62%
618
35%
1067
September1st to 10thNight
52%
720
20%
1822
11%
720
56%
720
33%
1182
September11th to 20thNight
60%
720
28%
1980
20%
720
64%
720
39%
1160
September21st to endNight
46%
720
21%
1980
15%
720
51%
720
28%
1297
October1st to 10thNight
43%
720
19%
2137
16%
720
48%
720
25%
1396
October11th to 20thNight
30%
720
17%
2160
11%
720
39%
720
20%
1514
October21st to endNight
25%
792
17%
2390
11%
792
34%
792
15%
1783
November1st to 10thNight
37%
740
21%
2406
17%
740
44%
740
21%
1577
November11th to 20thNight
22%
760
15%
2652
8%
760
32%
760
15%
1876
November21st to endNight
22%
760
10%
2660
7%
760
28%
760
11%
1991
December1st to 10thNight
14%
760
8%
2660
3%
760
20%
760
8%
2142
December11th to 20thNight
14%
760
8%
3251
3%
759
22%
759
7%
2480
December21st to endNight
11%
825
4%
4866
2%
817
17%
817
3%
4135

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%10%48%7%45%5%6%7%30%
75126
Night
15%10%5%8%6%35%5%5%7%32%
74608
TransparencyDay
53%311%21%11%1
74841
Night
53%311%21%11%1
74429
SeeingDay
20%9%28%24%13%6%
13802
Night
20%9%28%30%12%2
22989

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 10thDay
15%15%7%12%8%46%6%45%17%
1600
11th to 20thDay
16%17%9%14%7%3445%5%14%
1647
21st to endDay
13%18%8%12%10%47%5%4415%
1782
February1st to 10thDay
16%17%6%11%11%5%6%445%14%
1620
11th to 20thDay
13%14%8%12%9%46%5%45%19%
1573
21st to endDay
17%15%6%9%7%46%446%22%
1456
March1st to 10thDay
15%13%410%7%5%45%5%6%25%
1938
11th to 20thDay
14%13%6%9%7%44447%29%
1980
21st to endDay
18%11%6%8%6%4445%5%30%
2178
April1st to 10thDay
16%12%5%7%6%45%5%5%7%28%
2060
11th to 20thDay
18%10%46%6%3436%7%33%
2276
21st to endDay
21%10%47%6%3335%6%32%
2340
May1st to 10thDay
18%8%46%6%45%5%5%8%33%
2340
11th to 20thDay
16%8%36%6%35%45%7%36%
2336
21st to endDay
12%5%25%6%36%6%6%10%40%
2725
June1st to 10thDay
13%5%36%5%35%5%7%8%39%
2520
11th to 20thDay
11%6%36%5%46%6%6%10%38%
2647
21st to endDay
13%5%25%5%45%6%6%10%40%
2700
July1st to 10thDay
9%425%6%36%6%6%10%44%
2700
11th to 20thDay
11%5%36%6%36%6%8%10%36%
2406
21st to endDay
9%6%27%6%46%5%7%9%39%
2547
August1st to 10thDay
9%5%26%6%5%6%6%8%10%37%
2327
11th to 20thDay
9%5%36%8%36%7%7%9%36%
2303
21st to endDay
12%6%26%6%45%5%6%8%40%
2530
September1st to 10thDay
12%6%36%6%45%5%6%9%37%
2135
11th to 20thDay
12%5%36%5%345%6%8%43%
1980
21st to endDay
15%6%37%6%36%46%7%36%
1980
October1st to 10thDay
17%9%38%6%3446%6%35%
1823
11th to 20thDay
22%9%48%6%35%46%6%27%
1800
21st to endDay
23%12%38%7%36%5%5%6%22%
1962
November1st to 10thDay
14%10%48%6%45%5%5%8%31%
1672
11th to 20thDay
15%14%48%7%45%5%7%9%23%
1525
21st to endDay
19%15%7%9%7%35%5%47%18%
1520
December1st to 10thDay
16%18%8%11%8%36%45%5%17%
1520
11th to 20thDay
17%17%8%12%7%46%5%5%5%15%
1906
21st to endDay
29%19%8%12%8%333448%
2772
January1st to 10thNight
17%12%7%12%8%45%5%5%6%18%
2564
11th to 20thNight
20%17%8%10%8%45%445%15%
2386
21st to endNight
12%12%8%14%9%46%446%20%
2574
February1st to 10thNight
15%16%7%11%9%45%446%19%
2340
11th to 20thNight
14%12%7%10%8%47%45%7%23%
2273
21st to endNight
17%12%5%11%8%45%5%46%23%
1798
March1st to 10thNight
13%9%38%7%45%5%6%8%32%
2007
11th to 20thNight
14%10%49%6%4445%7%33%
1979
21st to endNight
16%11%49%5%3445%435%
2178
April1st to 10thNight
18%8%47%5%35%45%7%33%
1899
11th to 20thNight
16%8%46%6%3445%7%36%
1647
21st to endNight
14%9%37%6%445%7%8%33%
1620
May1st to 10thNight
17%7%36%5%245%6%8%36%
1620
11th to 20thNight
13%6%35%6%35%5%6%8%40%
1556
21st to endNight
9%4244245%5%8%51%
1550
June1st to 10thNight
11%4346%35%47%8%45%
1440
11th to 20thNight
9%5%25%5%36%47%10%43%
1306
21st to endNight
10%5%35%4446%5%8%46%
1260
July1st to 10thNight
5%32443445%9%56%
1260
11th to 20thNight
8%5%245%2446%8%51%
1546
21st to endNight
7%5%25%5%36%5%6%9%47%
1771
August1st to 10thNight
7%5%17%4346%7%8%48%
1611
11th to 20thNight
7%5%15%435%47%9%50%
1598
21st to endNight
8%6%25%5%35%5%6%9%47%
1806
September1st to 10thNight
10%6%36%6%3445%7%46%
1822
11th to 20thNight
10%4243245%47%53%
1980
21st to endNight
15%7%26%6%3445%7%41%
1980
October1st to 10thNight
15%8%35%5%345%5%7%40%
2137
11th to 20thNight
18%9%37%7%345%5%6%33%
2160
21st to endNight
22%9%47%6%35%5%5%6%27%
2390
November1st to 10thNight
14%8%36%6%35%46%8%36%
2406
11th to 20thNight
16%12%48%6%35%5%6%8%27%
2652
21st to endNight
19%13%6%8%6%45%5%5%7%22%
2660
December1st to 10thNight
18%16%8%12%8%45%45%5%17%
2660
11th to 20thNight
14%19%7%11%7%3445%6%19%
3288
21st to endNight
26%20%8%9%7%3434411%
4884

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 10thDay
70%38%13%5%
1601
11th to 20thDay
73%38%10%5%1
1647
21st to endDay
74%35%11%6%1
1782
February1st to 10thDay
74%19%12%4
1620
11th to 20thDay
68%28%14%8%
1582
21st to endDay
65%311%14%7%1
1456
March1st to 10thDay
60%311%18%7%1
1941
11th to 20thDay
57%38%19%11%2
1980
21st to endDay
57%29%19%12%2
2178
April1st to 10thDay
57%310%19%11%
2060
11th to 20thDay
52%211%20%13%1
2276
21st to endDay
54%210%20%11%2
2340
May1st to 10thDay
51%210%24%12%1
2340
11th to 20thDay
48%312%24%12%2
2340
21st to endDay
41%414%24%15%2
2725
June1st to 10thDay
43%313%26%14%2
2520
11th to 20thDay
42%412%24%17%2
2647
21st to endDay
40%412%26%17%
2700
July1st to 10thDay
36%411%29%18%3
2626
11th to 20thDay
41%413%27%14%1
2333
21st to endDay
41%412%26%15%2
2405
August1st to 10thDay
40%415%28%11%2
2314
11th to 20thDay
43%315%26%12%1
2303
21st to endDay
42%411%27%14%2
2530
September1st to 10thDay
44%313%26%13%1
2135
11th to 20thDay
39%312%31%15%
1980
21st to endDay
47%312%27%10%1
1980
October1st to 10thDay
51%311%20%14%1
1823
11th to 20thDay
57%312%18%9%1
1800
21st to endDay
64%311%16%7%
1962
November1st to 10thDay
53%410%24%8%1
1672
11th to 20thDay
57%414%15%9%1
1525
21st to endDay
68%211%14%4
1520
December1st to 10thDay
70%311%11%5%
1520
11th to 20thDay
73%29%11%4
1906
21st to endDay
83%17%8%1
2772
January1st to 10thNight
67%29%14%7%
2564
11th to 20thNight
72%38%11%5%
2386
21st to endNight
67%28%16%6%1
2574
February1st to 10thNight
68%29%15%6%
2340
11th to 20thNight
62%410%16%8%
2275
21st to endNight
64%29%17%8%
1798
March1st to 10thNight
52%211%23%10%1
2017
11th to 20thNight
52%39%24%10%2
1980
21st to endNight
53%27%21%13%3
2178
April1st to 10thNight
52%28%21%15%1
1899
11th to 20thNight
48%38%20%18%2
1647
21st to endNight
49%29%22%15%3
1620
May1st to 10thNight
46%210%23%15%3
1620
11th to 20thNight
42%311%26%14%4
1557
21st to endNight
32%315%28%18%3
1551
June1st to 10thNight
38%212%28%17%3
1440
11th to 20thNight
37%214%27%18%2
1306
21st to endNight
36%415%25%20%1
1260
July1st to 10thNight
27%410%31%24%4
1225
11th to 20thNight
31%313%32%17%3
1497
21st to endNight
34%414%27%18%3
1672
August1st to 10thNight
33%414%34%13%1
1600
11th to 20thNight
32%316%33%14%2
1598
21st to endNight
34%412%31%17%2
1806
September1st to 10thNight
39%312%28%16%2
1822
11th to 20thNight
32%311%34%18%2
1980
21st to endNight
44%213%28%13%
1980
October1st to 10thNight
45%310%25%16%1
2137
11th to 20thNight
52%311%23%11%1
2160
21st to endNight
58%38%19%11%1
2390
November1st to 10thNight
46%411%25%13%1
2406
11th to 20thNight
55%312%20%8%1
2652
21st to endNight
62%316%14%5%1
2660
December1st to 10thNight
70%39%14%4
2660
11th to 20thNight
66%212%15%41
3288
21st to endNight
79%110%8%2
4884

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 10thDay
24%17%33%20%5%1
220
11th to 20thDay
24%14%42%15%41
249
21st to endDay
28%11%37%20%31
264
February1st to 10thDay
30%14%42%13%1
240
11th to 20thDay
27%18%42%12%2
240
21st to endDay
28%28%31%12%1
198
March1st to 10thDay
24%14%35%20%6%1
381
11th to 20thDay
24%11%38%20%6%2
420
21st to endDay
28%12%29%23%7%1
462
April1st to 10thDay
20%16%32%24%5%2
420
11th to 20thDay
29%11%26%18%12%4
412
21st to endDay
27%9%31%23%7%3
420
May1st to 10thDay
25%7%27%24%13%4
423
11th to 20thDay
18%9%28%23%17%5%
447
21st to endDay
15%423%33%17%8%
485
June1st to 10thDay
15%6%30%31%14%5%
450
11th to 20thDay
12%7%29%31%16%4
577
21st to endDay
14%5%30%32%13%5%
630
July1st to 10thDay
10%422%29%25%10%
621
11th to 20thDay
14%323%27%21%12%
457
21st to endDay
10%124%35%22%8%
488
August1st to 10thDay
10%220%29%24%15%
446
11th to 20thDay
14%316%30%21%16%
439
21st to endDay
14%5%20%27%23%12%
495
September1st to 10thDay
15%5%20%27%21%12%
450
11th to 20thDay
10%318%28%28%12%
450
21st to endDay
18%8%25%26%14%10%
450
October1st to 10thDay
21%8%22%22%21%5%
450
11th to 20thDay
22%14%31%23%8%1
450
21st to endDay
29%10%33%22%5%1
477
November1st to 10thDay
22%19%31%17%8%3
270
11th to 20thDay
26%15%34%16%7%3
183
21st to endDay
26%15%40%16%3
180
December1st to 10thDay
31%17%34%13%41
180
11th to 20thDay
29%20%31%18%21
180
21st to endDay
32%17%37%12%3
198
January1st to 10thNight
24%15%36%19%5%2
760
11th to 20thNight
30%12%31%22%4
735
21st to endNight
19%10%34%29%7%
792
February1st to 10thNight
24%15%36%22%3
720
11th to 20thNight
23%14%34%23%6%
703
21st to endNight
25%15%34%23%3
592
March1st to 10thNight
20%13%35%26%7%
720
11th to 20thNight
20%13%37%23%6%1
720
21st to endNight
22%9%31%26%10%1
792
April1st to 10thNight
22%12%29%30%5%
720
11th to 20thNight
22%9%31%27%10%1
583
21st to endNight
20%7%31%34%8%
540
May1st to 10thNight
20%5%29%30%15%1
540
11th to 20thNight
18%427%37%14%1
495
21st to endNight
11%326%41%18%1
389
June1st to 10thNight
15%326%42%13%1
360
11th to 20thNight
11%329%43%14%1
360
21st to endNight
13%323%46%15%1
360
July1st to 10thNight
6%120%48%22%3
350
11th to 20thNight
10%121%40%25%3
470
21st to endNight
11%116%48%22%3
591
August1st to 10thNight
10%113%43%31%3
537
11th to 20thNight
10%113%41%29%6%
534
21st to endNight
10%120%39%26%4
618
September1st to 10thNight
14%321%33%23%6%
720
11th to 20thNight
13%317%36%26%5%
720
21st to endNight
19%420%33%19%5%
720
October1st to 10thNight
20%5%23%31%18%3
720
11th to 20thNight
24%9%30%27%10%1
720
21st to endNight
27%9%31%27%5%
792
November1st to 10thNight
20%11%25%32%11%1
740
11th to 20thNight
22%13%34%21%8%1
760
21st to endNight
28%10%31%25%7%
760
December1st to 10thNight
29%14%32%19%5%
760
11th to 20thNight
24%16%35%19%5%
760
21st to endNight
30%13%33%20%3
836
Page generated at 2024-01-11 04:22:37. Version ac07

Copyright 2024 Attilla Danko


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