Mais Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mais Observatory clear sky chart from 2005-11-05 to 2017-12-02.

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
77%
16537
33%
47893
30%
16494
78%
16494
49%
24806

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
68%
717
29%
2327
29%
716
73%
716
42%
1200
January16th to endNight
64%
768
33%
2304
30%
768
69%
768
38%
1294
February1st to 15thNight
70%
698
33%
2109
34%
698
74%
698
43%
1126
February16th to endNight
60%
632
27%
1895
31%
632
62%
632
30%
1178
March1st to 15thNight
69%
720
29%
2160
32%
720
72%
720
40%
1181
March16th to endNight
73%
768
28%
2035
25%
768
74%
768
43%
1165
April1st to 15thNight
65%
719
26%
1799
18%
719
66%
719
41%
1098
April16th to endNight
72%
720
30%
1800
19%
720
74%
720
50%
1026
May1st to 15thNight
73%
578
29%
1658
21%
578
74%
578
44%
928
May16th to endNight
72%
561
27%
1685
21%
561
73%
561
41%
942
June1st to 15thNight
81%
540
30%
1620
26%
540
81%
540
52%
813
June16th to endNight
93%
540
36%
1620
33%
540
93%
540
78%
637
July1st to 15thNight
92%
510
29%
1530
25%
510
92%
510
64%
674
July16th to endNight
90%
625
31%
1649
24%
587
89%
587
59%
792
August1st to 15thNight
93%
717
37%
1790
24%
713
93%
713
77%
823
August16th to endNight
94%
764
41%
1910
29%
764
94%
764
76%
898
September1st to 15thNight
91%
720
37%
1872
31%
720
92%
720
68%
896
September16th to endNight
89%
716
46%
1980
44%
716
90%
716
71%
872
October1st to 15thNight
80%
720
35%
1980
34%
720
81%
720
56%
1005
October16th to endNight
77%
768
38%
2303
39%
768
79%
768
50%
1141
November1st to 15thNight
78%
760
33%
2470
37%
760
80%
760
47%
1193
November16th to endNight
75%
780
35%
2535
38%
780
78%
780
44%
1277
December1st to 15thNight
68%
728
32%
2366
35%
728
70%
728
38%
1267
December16th to endNight
62%
768
31%
2496
31%
768
67%
768
35%
1380

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
5%312212346%65%
48540
Night
6%312323346%62%
48097
TransparencyDay
20%35%15%26%28%
48241
Night
22%36%14%23%29%
47897
SeeingDay
8%7%27%39%13%3
6178
Night
7%17%32%38%11%
16549

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
8%5%14422335%59%
1611
16th to endDay
10%5%23213347%55%
1917
February1st to 15thDay
9%314323335%57%
1751
16th to endDay
14%7%24323347%45%
1579
March1st to 15thDay
7%31331335%8%56%
1800
16th to endDay
6%314323347%58%
2184
April1st to 15thDay
8%423224446%55%
2149
16th to endDay
6%312212236%66%
2160
May1st to 15thDay
5%423313435%62%
2289
16th to endDay
4312213345%65%
2429
June1st to 15thDay
331221222471%
2340
16th to endDay
111112385%
2340
July1st to 15thDay
112322346%69%
2340
16th to endDay
21221346%7%66%
2402
August1st to 15thDay
111211235%77%
2160
16th to endDay
11212345%77%
2292
September1st to 15thDay
1121223477%
2088
16th to endDay
11121123479%
1980
October1st to 15thDay
5%312212335%66%
1980
16th to endDay
5%31331223469%
1917
November1st to 15thDay
5%313323345%63%
1719
16th to endDay
7%413213247%61%
1755
December1st to 15thDay
9%41333335%8%52%
1630
16th to endDay
14%424323235%53%
1728
January1st to 15thNight
7%32332334459%
2327
16th to endNight
11%42342233456%
2304
February1st to 15thNight
8%423222335%59%
2101
16th to endNight
14%6%24424335%47%
1895
March1st to 15thNight
9%5%1331335%7%55%
2160
16th to endNight
7%42332345%8%54%
2035
April1st to 15thNight
9%7%24313347%51%
1799
16th to endNight
6%422322336%62%
1800
May1st to 15thNight
5%5%23424447%56%
1658
16th to endNight
5%6%233225%36%57%
1684
June1st to 15thNight
1412323347%64%
1620
16th to endNight
11223482%
1620
July1st to 15thNight
1132335%8%68%
1620
16th to endNight
2222345%9%64%
1762
August1st to 15thNight
1111227%8%72%
1800
16th to endNight
11112345%77%
1910
September1st to 15thNight
112213345%73%
1872
16th to endNight
21121123479%
1980
October1st to 15thNight
5%212213346%67%
1980
16th to endNight
6%313322345%65%
2303
November1st to 15thNight
4322323435%64%
2470
16th to endNight
5%413323346%59%
2535
December1st to 15thNight
9%413323347%54%
2366
16th to endNight
13%414312335%55%
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
27%25%12%26%25%
1612
16th to endDay
29%37%13%16%29%
1917
February1st to 15thDay
28%35%13%23%26%
1751
16th to endDay
38%45%15%23%13%
1579
March1st to 15thDay
25%36%20%23%21%
1800
16th to endDay
24%48%23%22%15%
2184
April1st to 15thDay
28%46%22%26%10%
2149
16th to endDay
19%37%22%27%18%
2160
May1st to 15thDay
23%36%20%27%19%
2289
16th to endDay
20%36%22%33%13%
2432
June1st to 15thDay
18%2317%30%27%
2340
16th to endDay
7%126%22%59%
2340
July1st to 15thDay
14%3411%25%40%
2201
16th to endDay
14%49%22%28%20%
2252
August1st to 15thDay
10%1314%33%36%
2146
16th to endDay
10%3311%34%36%
2292
September1st to 15thDay
10%339%35%37%
2088
16th to endDay
10%128%35%40%
1980
October1st to 15thDay
20%2415%28%28%
1980
16th to endDay
19%2411%20%41%
1917
November1st to 15thDay
22%36%14%20%32%
1719
16th to endDay
23%3412%22%34%
1755
December1st to 15thDay
29%39%14%17%26%
1630
16th to endDay
33%36%14%23%17%
1728
January1st to 15thNight
27%26%12%21%30%
2327
16th to endNight
31%27%10%16%31%
2304
February1st to 15thNight
26%26%14%20%29%
2112
16th to endNight
39%3313%22%16%
1895
March1st to 15thNight
28%36%18%19%23%
2160
16th to endNight
26%5%9%18%23%16%
2035
April1st to 15thNight
31%37%21%22%13%
1799
16th to endNight
24%38%20%22%20%
1800
May1st to 15thNight
26%48%16%22%20%
1659
16th to endNight
28%47%19%26%14%
1685
June1st to 15thNight
19%46%15%29%25%
1620
16th to endNight
6%247%20%58%
1620
July1st to 15thNight
12%2412%25%41%
1530
16th to endNight
15%411%21%28%19%
1649
August1st to 15thNight
8%15%16%37%30%
1790
16th to endNight
8%26%10%32%40%
1910
September1st to 15thNight
13%16%10%30%38%
1872
16th to endNight
11%129%34%40%
1980
October1st to 15thNight
19%25%16%28%27%
1980
16th to endNight
22%249%18%42%
2303
November1st to 15thNight
21%3415%19%35%
2470
16th to endNight
25%25%13%18%34%
2535
December1st to 15thNight
29%36%14%19%25%
2366
16th to endNight
31%38%13%21%21%
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
27%417%41%8%
90
16th to endDay
15%11%31%31%8%1
285
February1st to 15thDay
9%11%30%36%10%1
266
16th to endDay
20%12%35%25%5%
238
March1st to 15thDay
11%12%31%27%13%2
270
16th to endDay
7%14%36%26%12%2
288
April1st to 15thDay
12%17%35%23%8%2
269
16th to endDay
7%16%40%26%7%1
270
May1st to 15thDay
14%9%31%35%6%2
288
16th to endDay
11%10%34%32%10%1
330
June1st to 15thDay
4334%39%14%3
315
16th to endDay
123%49%18%6%
315
July1st to 15thDay
2114%54%18%7%
305
16th to endDay
48%59%16%10%
327
August1st to 15thDay
117%58%13%7%
315
16th to endDay
1112%58%17%8%
332
September1st to 15thDay
3126%53%11%3
315
16th to endDay
46%33%39%12%3
315
October1st to 15thDay
5%7%37%33%14%
315
16th to endDay
10%431%27%21%3
270
November1st to 15thDay
11%417%34%29%3
135
16th to endDay
13%5%17%37%21%5%
135
December1st to 15thDay
6%318%40%28%3
94
16th to endDay
21%428%34%11%
96
January1st to 15thNight
9%114%41%24%8%
720
16th to endNight
13%210%37%27%7%
768
February1st to 15thNight
11%19%37%30%9%
704
16th to endNight
16%310%38%24%6%
632
March1st to 15thNight
11%38%40%30%5%
720
16th to endNight
8%28%36%34%8%
768
April1st to 15thNight
11%410%39%28%5%
719
16th to endNight
8%211%35%33%8%
720
May1st to 15thNight
8%19%36%35%8%
579
16th to endNight
9%29%32%39%6%
563
June1st to 15thNight
2110%39%41%5%
540
16th to endNight
1234%53%7%
540
July1st to 15thNight
20%64%12%
510
16th to endNight
12114%63%18%
625
August1st to 15thNight
1118%59%18%
717
16th to endNight
110%59%28%
764
September1st to 15thNight
122%55%18%
720
16th to endNight
3430%45%16%
716
October1st to 15thNight
6%6%37%38%10%
720
16th to endNight
8%6%29%36%17%
768
November1st to 15thNight
6%16%39%33%12%
760
16th to endNight
8%18%35%31%13%
780
December1st to 15thNight
13%19%39%27%9%
728
16th to endNight
16%211%38%24%6%
768
Page generated at 2017-12-03 08:16:43. Version ac04

Copyright 2017 A. Danko


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