ME Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the ME Observatory clear sky chart from 2005-11-05 to 2017-10-16.

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
50%
15631
23%
47257
16%
15590
58%
15590
29%
29077

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
28%
719
24%
2327
10%
716
44%
716
23%
1431
January16th to endNight
27%
768
25%
2455
12%
768
43%
768
23%
1538
February1st to 15thNight
32%
703
26%
2111
11%
701
48%
701
27%
1294
February16th to endNight
26%
631
25%
1893
9%
631
40%
631
26%
1170
March1st to 15thNight
34%
720
24%
2056
12%
720
43%
720
29%
1283
March16th to endNight
41%
768
22%
2112
13%
768
48%
768
31%
1307
April1st to 15thNight
46%
650
25%
1908
17%
650
55%
650
35%
1101
April16th to endNight
51%
540
25%
1695
17%
540
60%
540
34%
978
May1st to 15thNight
51%
540
20%
1620
12%
540
58%
540
29%
1005
May16th to endNight
65%
561
21%
1682
15%
561
69%
561
32%
1032
June1st to 15thNight
73%
540
17%
1620
16%
540
74%
540
30%
1020
June16th to endNight
77%
540
16%
1620
14%
540
78%
540
33%
973
July1st to 15thNight
73%
510
12%
1530
12%
510
73%
510
29%
988
July16th to endNight
76%
564
16%
1595
14%
531
77%
531
28%
1024
August1st to 15thNight
72%
539
18%
1627
19%
536
72%
536
27%
1064
August16th to endNight
66%
573
18%
1910
20%
573
67%
573
21%
1278
September1st to 15thNight
67%
712
20%
1972
18%
712
68%
712
28%
1327
September16th to endNight
65%
717
25%
1980
20%
717
68%
717
31%
1262
October1st to 15thNight
59%
720
31%
1994
25%
720
65%
720
36%
1184
October16th to endNight
54%
708
33%
2123
26%
708
66%
708
38%
1178
November1st to 15thNight
53%
700
31%
2251
27%
700
63%
700
37%
1205
November16th to endNight
41%
720
27%
2340
18%
720
54%
720
31%
1328
December1st to 15thNight
38%
720
24%
2340
16%
720
48%
720
26%
1434
December16th to endNight
32%
768
21%
2496
14%
768
42%
768
20%
1673

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
12%5%244345%5%8%42%
48152
Night
11%42442445%7%46%
47457
TransparencyDay
37%7%12%20%17%4
47853
Night
35%6%11%20%19%6%
47260
SeeingDay
14%5%16%22%24%16%
5510
Night
13%6%22%29%23%4
15635

By Month

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
15%5%4442445%5%43%
1611
16th to endDay
18%6%24323446%43%
1767
February1st to 15thDay
15%6%24325%446%44%
1750
16th to endDay
18%5%24414446%43%
1580
March1st to 15thDay
15%5%25%42345%8%43%
1902
16th to endDay
16%4143245%5%8%43%
2111
April1st to 15thDay
11%5%35%5%2345%7%46%
2049
16th to endDay
11%4224245%5%8%49%
2264
May1st to 15thDay
10%5%34424449%46%
2331
16th to endDay
9%324435%5%7%9%43%
2431
June1st to 15thDay
8%425%5%35%6%8%12%37%
2340
16th to endDay
42145%36%5%7%12%45%
2340
July1st to 15thDay
9%435%5%47%7%8%11%31%
2340
16th to endDay
7%336%6%48%8%8%10%32%
2465
August1st to 15thDay
8%5%26%5%47%7%8%11%32%
2318
16th to endDay
13%6%36%6%46%6%6%9%29%
2286
September1st to 15thDay
11%6%25%5%35%6%6%8%37%
1980
16th to endDay
14%5%15%43345%7%45%
1980
October1st to 15thDay
12%5%22323345%54%
1965
16th to endDay
11%314312335%58%
1770
November1st to 15thDay
11%423313346%55%
1604
16th to endDay
15%433233345%49%
1620
December1st to 15thDay
17%6%344335%45%41%
1620
16th to endDay
23%7%35%423335%36%
1728
January1st to 15thNight
17%6%24423346%45%
2327
16th to endNight
16%6%25%423445%44%
2455
February1st to 15thNight
15%4245%13346%48%
2103
16th to endNight
16%5%25%32335%5%46%
1893
March1st to 15thNight
13%5%24424346%48%
2056
16th to endNight
12%5%23324446%49%
2112
April1st to 15thNight
11%41232445%8%50%
1908
16th to endNight
9%423424447%51%
1695
May1st to 15thNight
9%425%5%345%5%7%46%
1619
16th to endNight
7%424435%5%6%8%47%
1682
June1st to 15thNight
6%424436%7%6%11%41%
1620
16th to endNight
42135%36%6%8%12%43%
1620
July1st to 15thNight
6%3246%46%6%8%13%35%
1620
16th to endNight
4325%5%48%7%8%13%35%
1703
August1st to 15thNight
6%5%15%6%45%6%9%11%37%
1638
16th to endNight
11%5%26%5%27%5%7%9%35%
1910
September1st to 15thNight
8%425%5%46%5%7%8%41%
1972
16th to endNight
12%5%144345%47%46%
1980
October1st to 15thNight
11%41331345%7%53%
1994
16th to endNight
10%32441333460%
2123
November1st to 15thNight
11%313313235%58%
2251
16th to endNight
14%41332335%5%52%
2340
December1st to 15thNight
14%5%34424346%46%
2340
16th to endNight
21%7%245%23446%37%
2496

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
41%310%15%24%4
1612
16th to endDay
40%37%20%20%7%
1767
February1st to 15thDay
40%48%20%22%3
1752
16th to endDay
42%46%20%19%6%
1580
March1st to 15thDay
39%411%19%19%4
1902
16th to endDay
38%6%12%21%16%3
2112
April1st to 15thDay
37%5%9%22%20%5%
2049
16th to endDay
31%6%11%24%22%4
2264
May1st to 15thDay
35%7%14%21%19%3
2331
16th to endDay
34%8%15%25%14%1
2435
June1st to 15thDay
35%9%21%24%7%1
2340
16th to endDay
28%8%18%26%15%2
2340
July1st to 15thDay
39%12%20%19%6%1
2201
16th to endDay
39%13%18%18%8%1
2310
August1st to 15thDay
41%12%16%19%8%1
2305
16th to endDay
47%11%14%14%10%
2286
September1st to 15thDay
40%9%14%17%15%2
1980
16th to endDay
37%5%12%19%20%3
1980
October1st to 15thDay
31%410%18%26%7%
1965
16th to endDay
29%36%19%31%11%
1770
November1st to 15thDay
30%37%16%31%10%
1604
16th to endDay
36%46%17%27%7%
1620
December1st to 15thDay
43%5%7%21%14%7%
1620
16th to endDay
50%47%17%13%6%
1728
January1st to 15thNight
40%37%18%24%5%
2327
16th to endNight
42%35%18%22%7%
2455
February1st to 15thNight
38%37%19%21%10%
2112
16th to endNight
38%36%19%24%6%
1893
March1st to 15thNight
37%49%18%20%8%
2056
16th to endNight
34%5%10%22%21%5%
2112
April1st to 15thNight
31%410%23%22%8%
1908
16th to endNight
32%5%10%22%21%8%
1695
May1st to 15thNight
36%6%13%20%20%2
1620
16th to endNight
32%8%13%26%15%3
1684
June1st to 15thNight
33%10%18%26%9%1
1620
16th to endNight
28%10%19%22%15%2
1620
July1st to 15thNight
33%11%23%22%6%2
1530
16th to endNight
32%13%22%19%10%2
1595
August1st to 15thNight
35%11%16%24%10%1
1627
16th to endNight
41%10%17%17%12%
1910
September1st to 15thNight
37%11%14%18%15%4
1972
16th to endNight
35%7%12%19%17%5%
1980
October1st to 15thNight
31%6%10%18%26%7%
1994
16th to endNight
29%4416%31%13%
2123
November1st to 15thNight
29%35%17%31%14%
2251
16th to endNight
33%37%17%27%10%
2340
December1st to 15thNight
38%49%21%17%8%
2340
16th to endNight
47%47%15%18%5%
2496

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
18%14%31%24%8%2
90
16th to endDay
17%25%39%11%6%
96
February1st to 15thDay
12%22%35%26%3
90
16th to endDay
20%14%40%19%3
81
March1st to 15thDay
17%13%27%30%9%1
192
16th to endDay
18%7%25%30%16%1
288
April1st to 15thDay
13%14%27%19%21%4
270
16th to endDay
14%322%27%26%4
270
May1st to 15thDay
13%6%23%22%20%13%
288
16th to endDay
12%213%24%25%21%
331
June1st to 15thDay
10%18%19%26%33%
315
16th to endDay
7%16%26%27%30%
315
July1st to 15thDay
9%5%18%30%35%
305
16th to endDay
8%415%34%36%
326
August1st to 15thDay
15%7%20%29%27%
313
16th to endDay
15%8%19%31%25%
332
September1st to 15thDay
13%211%19%31%21%
315
16th to endDay
17%18%23%36%12%
314
October1st to 15thDay
14%318%29%23%10%
315
16th to endDay
13%5%16%25%31%7%
276
November1st to 15thDay
23%11%21%21%17%4
112
16th to endDay
13%7%30%25%17%5%
90
December1st to 15thDay
25%6%36%21%10%
90
16th to endDay
33%16%20%20%7%1
96
January1st to 15thNight
21%12%31%25%7%
720
16th to endNight
19%13%34%26%5%
768
February1st to 15thNight
18%12%31%31%5%
704
16th to endNight
17%14%38%26%3
631
March1st to 15thNight
16%10%34%31%6%
720
16th to endNight
14%9%28%30%15%
768
April1st to 15thNight
14%8%28%30%16%1
650
16th to endNight
10%5%25%34%21%2
540
May1st to 15thNight
10%425%32%23%3
540
16th to endNight
9%15%31%35%6%
563
June1st to 15thNight
8%10%31%37%11%
540
16th to endNight
5%8%31%42%12%
540
July1st to 15thNight
7%6%23%47%14%
510
16th to endNight
5%7%21%52%13%
564
August1st to 15thNight
8%5%27%46%11%
539
16th to endNight
13%15%24%45%9%
573
September1st to 15thNight
10%17%25%43%10%
712
16th to endNight
14%110%33%35%3
717
October1st to 15thNight
13%318%31%26%5%
720
16th to endNight
10%5%23%31%24%4
708
November1st to 15thNight
14%5%23%30%25%1
700
16th to endNight
16%9%29%27%16%
720
December1st to 15thNight
15%9%31%30%12%1
720
16th to endNight
23%10%28%29%7%
768
Page generated at 2017-10-17 16:35:27. Version ac04

Copyright 2017 A. Danko


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