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 2017-03-24.

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
76%
15615
33%
45300
30%
15572
78%
15572
48%
23534

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%
740
27%
1965
24%
740
75%
740
43%
1123
April1st to 15thNight
62%
659
26%
1649
19%
659
64%
659
39%
1027
April16th to endNight
71%
660
28%
1650
18%
660
73%
660
48%
956
May1st to 15thNight
73%
530
30%
1520
22%
530
74%
530
44%
849
May16th to endNight
71%
513
25%
1541
19%
513
72%
513
41%
867
June1st to 15thNight
81%
495
31%
1485
28%
495
82%
495
53%
741
June16th to endNight
93%
495
33%
1485
30%
495
93%
495
77%
589
July1st to 15thNight
92%
465
31%
1395
26%
465
92%
465
62%
623
July16th to endNight
90%
578
31%
1518
24%
540
89%
540
59%
727
August1st to 15thNight
92%
657
38%
1640
25%
653
93%
653
76%
759
August16th to endNight
93%
700
39%
1750
27%
700
93%
700
75%
825
September1st to 15thNight
92%
660
40%
1716
33%
660
92%
660
71%
808
September16th to endNight
89%
656
45%
1815
43%
656
91%
656
73%
790
October1st to 15thNight
79%
660
36%
1815
35%
660
80%
660
54%
934
October16th to endNight
76%
704
36%
2110
37%
704
78%
704
49%
1054
November1st to 15thNight
79%
700
34%
2275
38%
700
81%
700
49%
1069
November16th to endNight
75%
720
34%
2340
37%
720
78%
720
44%
1179
December1st to 15thNight
68%
720
32%
2340
35%
720
70%
720
38%
1255
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%312213336%65%
45619
Night
6%312323346%62%
45504
TransparencyDay
21%35%15%26%28%
45320
Night
23%36%14%23%29%
45304
SeeingDay
9%7%29%39%11%3
5214
Night
8%17%32%38%11%
15627

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%
2099
April1st to 15thDay
9%424214436%54%
1969
16th to endDay
6%312212236%65%
1980
May1st to 15thDay
5%423313435%63%
2097
16th to endDay
4312213345%67%
2221
June1st to 15thDay
431221322470%
2145
16th to endDay
111112384%
2145
July1st to 15thDay
111422346%70%
2145
16th to endDay
21221345%7%67%
2226
August1st to 15thDay
112211235%77%
1980
16th to endDay
11212345%76%
2100
September1st to 15thDay
1121223478%
1914
16th to endDay
1121123479%
1815
October1st to 15thDay
6%412222345%64%
1815
16th to endDay
6%31331223468%
1758
November1st to 15thDay
5%312222345%66%
1584
16th to endDay
7%313213247%61%
1620
December1st to 15thDay
9%41333345%8%52%
1620
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%9%53%
1965
April1st to 15thNight
10%8%24313347%50%
1649
16th to endNight
7%422322335%61%
1650
May1st to 15thNight
45%2242445%7%56%
1520
16th to endNight
5%7%23322436%57%
1540
June1st to 15thNight
1412323347%65%
1485
16th to endNight
1111223481%
1485
July1st to 15thNight
1132335%7%67%
1485
16th to endNight
2222345%8%65%
1631
August1st to 15thNight
1111227%8%70%
1650
16th to endNight
11112345%77%
1750
September1st to 15thNight
12212245%74%
1716
16th to endNight
21111122481%
1815
October1st to 15thNight
5%212313346%66%
1815
16th to endNight
6%313322345%64%
2110
November1st to 15thNight
422232233467%
2275
16th to endNight
6%412323436%60%
2340
December1st to 15thNight
9%414323347%54%
2340
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
25%48%23%21%15%
2099
April1st to 15thDay
30%46%23%23%11%
1969
16th to endDay
20%36%22%28%17%
1980
May1st to 15thDay
22%36%20%27%20%
2097
16th to endDay
19%36%23%35%11%
2224
June1st to 15thDay
19%2316%30%27%
2145
16th to endDay
7%126%23%57%
2145
July1st to 15thDay
13%3411%25%41%
2006
16th to endDay
14%49%22%27%21%
2076
August1st to 15thDay
10%1314%33%36%
1966
16th to endDay
10%3411%34%35%
2100
September1st to 15thDay
10%237%34%40%
1914
16th to endDay
10%228%34%41%
1815
October1st to 15thDay
22%2416%27%26%
1815
16th to endDay
20%25%10%20%40%
1758
November1st to 15thDay
20%36%13%20%34%
1584
16th to endDay
23%3412%21%34%
1620
December1st to 15thDay
29%39%14%16%26%
1620
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%
1965
April1st to 15thNight
34%37%21%20%13%
1649
16th to endNight
25%38%19%23%20%
1650
May1st to 15thNight
26%48%16%22%21%
1521
16th to endNight
28%47%19%26%13%
1541
June1st to 15thNight
18%46%14%29%25%
1485
16th to endNight
6%25%7%21%56%
1485
July1st to 15thNight
13%25%12%23%41%
1395
16th to endNight
15%410%21%28%20%
1518
August1st to 15thNight
8%25%16%37%30%
1640
16th to endNight
8%26%10%31%39%
1750
September1st to 15thNight
11%16%8%30%40%
1716
16th to endNight
10%1310%33%41%
1815
October1st to 15thNight
20%35%17%28%25%
1815
16th to endNight
23%2410%19%40%
2110
November1st to 15thNight
20%3414%19%38%
2275
16th to endNight
24%25%14%18%34%
2340
December1st to 15thNight
29%36%14%19%26%
2340
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%38%25%11%2
260
April1st to 15thDay
15%20%36%21%41
209
16th to endDay
10%17%39%28%21
210
May1st to 15thDay
15%11%32%35%4
228
16th to endDay
12%11%34%31%9%1
266
June1st to 15thDay
5%438%39%10%2
255
16th to endDay
1126%50%14%5%
255
July1st to 15thDay
2216%60%14%4
245
16th to endDay
5%10%63%12%7%
271
August1st to 15thDay
2120%60%9%6%
255
16th to endDay
1111%61%14%8%
268
September1st to 15thDay
3125%56%10%2
255
16th to endDay
36%35%41%8%3
255
October1st to 15thDay
6%9%41%30%10%
255
16th to endDay
12%5%34%28%16%2
212
November1st to 15thDay
8%414%28%37%5%
90
16th to endDay
13%6%21%40%16%2
90
December1st to 15thDay
6%318%41%26%3
90
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%9%
740
April1st to 15thNight
12%411%39%27%5%
659
16th to endNight
9%211%35%32%8%
660
May1st to 15thNight
7%110%37%35%7%
531
16th to endNight
10%310%31%39%6%
515
June1st to 15thNight
219%39%41%5%
495
16th to endNight
1335%53%6%
495
July1st to 15thNight
21%64%12%
465
16th to endNight
12113%64%17%
578
August1st to 15thNight
1119%59%18%
657
16th to endNight
19%59%28%
700
September1st to 15thNight
120%57%19%
660
16th to endNight
3429%46%16%
656
October1st to 15thNight
6%16%38%36%11%
660
16th to endNight
9%6%29%36%17%
704
November1st to 15thNight
5%16%37%35%14%
700
16th to endNight
8%18%35%31%14%
720
December1st to 15thNight
13%19%39%27%9%
720
16th to endNight
16%211%38%24%6%
768
Page generated at 2017-03-25 09:39:53. Version ac04

Copyright 2017 A. Danko


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