Observatoire de Mirabilis
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire de Mirabilis clear sky chart from 2005-11-05 to

2017-09-12
.

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
26%
14579
13%
46789
7%
14547
33%
14547
15%
33724

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%
720
7%
2506
2%
716
19%
716
7%
2038
January16th to endNight
17%
768
10%
2688
5%
768
25%
768
10%
2020
February1st to 15thNight
16%
704
10%
2296
3%
701
25%
701
10%
1757
February16th to endNight
18%
631
12%
1919
5%
631
27%
631
11%
1464
March1st to 15thNight
16%
720
13%
2148
6%
720
25%
720
12%
1637
March16th to endNight
27%
768
20%
2001
7%
768
36%
768
21%
1389
April1st to 15thNight
23%
718
16%
1796
5%
718
28%
718
19%
1331
April16th to endNight
25%
631
16%
1711
6%
631
32%
631
19%
1207
May1st to 15thNight
27%
360
15%
1440
11%
360
39%
360
15%
979
May16th to endNight
28%
375
13%
1497
9%
374
40%
374
17%
979
June1st to 15thNight
30%
360
7%
1440
5%
360
37%
360
13%
996
June16th to endNight
41%
360
8%
1440
11%
360
45%
360
16%
941
July1st to 15thNight
49%
340
11%
1360
15%
340
54%
340
26%
763
July16th to endNight
52%
376
12%
1418
14%
354
56%
354
24%
830
August1st to 15thNight
52%
375
13%
1446
13%
373
57%
373
21%
904
August16th to endNight
46%
737
19%
1883
10%
737
51%
737
34%
1195
September1st to 15thNight
43%
707
13%
1768
6%
707
45%
707
27%
1230
September16th to endNight
42%
657
19%
1787
11%
657
47%
657
30%
1158
October1st to 15thNight
28%
660
17%
1972
10%
660
37%
660
18%
1384
October16th to endNight
22%
704
11%
2241
6%
704
28%
704
13%
1697
November1st to 15thNight
24%
700
17%
2304
10%
700
34%
700
14%
1657
November16th to endNight
19%
720
11%
2520
7%
720
25%
720
9%
1954
December1st to 15thNight
12%
720
8%
2520
2%
720
19%
720
7%
2039
December16th to endNight
10%
768
10%
2688
3%
768
18%
768
6%
2175

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
20%10%46%5%34446%28%
47882
Night
19%11%46%5%24446%30%
46958
Cloud CoverDay
20%10%46%5%34446%28%
47891
Night
18%11%46%5%34445%30%
46964
TransparencyDay
56%310%18%8%1
47569
Night
55%410%19%9%
46789
SeeingDay
27%14%28%19%8%2
5496
Night
25%13%27%23%8%
14579

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
21%19%5%10%7%3432417%
1432
16th to endDay
12%15%7%9%7%35%5%5%5%21%
1536
February1st to 15thDay
12%16%6%11%9%24345%22%
1563
16th to endDay
14%19%5%8%6%44345%23%
1553
March1st to 15thDay
17%13%5%9%5%34335%26%
1801
16th to endDay
16%10%46%423447%35%
2223
April1st to 15thDay
23%12%45%423335%31%
2152
16th to endDay
22%8%36%5%2444334%
2259
May1st to 15thDay
23%9%36%424446%28%
2511
16th to endDay
23%8%35%5%34346%29%
2618
June1st to 15thDay
24%8%35%5%36%5%5%6%25%
2520
16th to endDay
22%6%36%5%35%6%5%7%27%
2520
July1st to 15thDay
18%5%25%5%35%45%8%33%
2520
16th to endDay
16%6%25%6%35%5%7%8%30%
2654
August1st to 15thDay
18%7%26%6%45%5%5%7%29%
2502
16th to endDay
15%5%25%5%346%5%8%38%
2306
September1st to 15thDay
22%6%25%434446%35%
2112
16th to endDay
22%6%23312337%42%
1843
October1st to 15thDay
25%9%3443435%6%30%
1656
16th to endDay
29%14%28%5%2433419%
1631
November1st to 15thDay
18%11%47%5%345%5%6%28%
1554
16th to endDay
25%15%46%42324424%
1440
December1st to 15thDay
24%19%6%6%6%24335%16%
1440
16th to endDay
23%18%7%8%6%2433317%
1536
January1st to 15thNight
18%18%8%10%7%24345%15%
2506
16th to endNight
11%16%6%9%7%345%5%5%21%
2688
February1st to 15thNight
11%16%7%10%8%34445%23%
2294
16th to endNight
16%14%6%11%6%1445%6%23%
1919
March1st to 15thNight
20%12%5%7%6%34245%27%
2135
16th to endNight
15%9%36%424335%39%
2001
April1st to 15thNight
25%9%35%323335%33%
1796
16th to endNight
21%9%25%5%23445%36%
1711
May1st to 15thNight
22%7%45%5%24436%34%
1440
16th to endNight
19%6%35%4245%5%6%36%
1495
June1st to 15thNight
21%7%36%6%2346%6%29%
1440
16th to endNight
20%425%435%6%5%6%36%
1440
July1st to 15thNight
13%5%244245%6%8%44%
1440
16th to endNight
11%4235%345%6%9%42%
1514
August1st to 15thNight
13%5%246%345%6%8%39%
1456
16th to endNight
12%4245%2346%7%47%
1883
September1st to 15thNight
18%6%2442445%6%39%
1768
16th to endNight
18%5%23223346%45%
1787
October1st to 15thNight
21%7%36%5%33446%34%
1972
16th to endNight
29%12%35%423346%24%
2241
November1st to 15thNight
21%9%46%5%3445%5%29%
2304
16th to endNight
22%16%6%8%5%2433422%
2520
December1st to 15thNight
23%18%6%8%6%2434417%
2520
16th to endNight
22%18%6%8%6%3433417%
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
21%18%6%9%6%3433317%
1432
16th to endDay
12%15%8%9%7%345%45%22%
1536
February1st to 15thDay
12%16%6%10%9%34445%22%
1563
16th to endDay
15%18%5%8%7%3434423%
1553
March1st to 15thDay
18%13%6%9%5%35%34425%
1811
16th to endDay
16%9%46%423346%35%
2222
April1st to 15thDay
23%12%45%5%22335%31%
2152
16th to endDay
22%9%36%42444433%
2259
May1st to 15thDay
22%9%47%5%24446%28%
2511
16th to endDay
22%9%36%5%34346%29%
2618
June1st to 15thDay
23%8%35%6%35%5%5%6%25%
2520
16th to endDay
22%7%26%5%35%5%5%7%26%
2520
July1st to 15thDay
17%6%26%5%345%6%7%33%
2520
16th to endDay
16%5%36%5%36%6%7%8%29%
2654
August1st to 15thDay
17%7%36%7%45%45%7%29%
2502
16th to endDay
13%6%25%5%3446%8%38%
2306
September1st to 15thDay
21%7%245%33446%35%
2112
16th to endDay
22%6%23322237%42%
1843
October1st to 15thDay
25%8%35%423446%30%
1656
16th to endDay
29%13%36%6%2333420%
1631
November1st to 15thDay
18%11%46%5%245%47%28%
1554
16th to endDay
25%14%46%5%23335%24%
1440
December1st to 15thDay
24%20%5%7%5%24335%17%
1440
16th to endDay
22%18%8%8%5%2443317%
1536
January1st to 15thNight
18%19%7%9%7%34345%16%
2506
16th to endNight
11%15%7%9%7%445%5%6%22%
2688
February1st to 15thNight
11%15%7%10%8%35%44423%
2287
16th to endNight
15%14%6%11%5%24446%23%
1919
March1st to 15thNight
20%12%47%6%35%24427%
2148
16th to endNight
15%9%35%5%24335%39%
2001
April1st to 15thNight
25%9%36%42333433%
1796
16th to endNight
20%10%25%423446%36%
1711
May1st to 15thNight
21%8%36%5%2243435%
1440
16th to endNight
20%6%26%5%25%446%35%
1495
June1st to 15thNight
21%9%36%5%25%447%29%
1440
16th to endNight
20%5%245%35%5%47%36%
1440
July1st to 15thNight
12%6%2442446%8%43%
1440
16th to endNight
11%5%25%425%5%6%7%43%
1514
August1st to 15thNight
12%5%346%4447%7%39%
1456
16th to endNight
12%5%145%2336%7%47%
1883
September1st to 15thNight
18%6%24334445%40%
1768
16th to endNight
19%5%23323445%46%
1787
October1st to 15thNight
19%8%36%5%33445%34%
1972
16th to endNight
28%11%26%424336%24%
2241
November1st to 15thNight
21%8%46%5%3435%5%30%
2304
16th to endNight
22%15%5%8%5%3333423%
2520
December1st to 15thNight
22%18%6%7%7%2433418%
2520
16th to endNight
22%18%6%8%7%3344417%
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
72%26%12%4
1433
16th to endDay
61%47%16%8%
1536
February1st to 15thDay
64%28%17%5%
1565
16th to endDay
64%27%14%9%1
1553
March1st to 15thDay
61%39%15%9%1
1811
16th to endDay
49%38%19%14%4
2223
April1st to 15thDay
55%27%19%11%2
2152
16th to endDay
53%37%18%12%3
2259
May1st to 15thDay
56%46%18%12%1
2511
16th to endDay
56%310%18%9%1
2622
June1st to 15thDay
57%410%16%9%
2520
16th to endDay
55%5%11%19%7%1
2520
July1st to 15thDay
46%415%23%9%
2371
16th to endDay
50%5%16%18%8%
2487
August1st to 15thDay
53%5%16%19%5%
2488
16th to endDay
42%417%25%9%
2306
September1st to 15thDay
49%312%22%11%
2112
16th to endDay
43%312%29%10%
1843
October1st to 15thDay
54%311%20%9%
1656
16th to endDay
68%310%13%5%
1631
November1st to 15thDay
55%5%14%16%8%
1554
16th to endDay
63%310%15%5%
1440
December1st to 15thDay
70%310%12%3
1440
16th to endDay
71%37%11%7%
1536
January1st to 15thNight
70%38%12%4
2506
16th to endNight
61%39%15%8%1
2688
February1st to 15thNight
62%39%18%5%
2296
16th to endNight
60%39%15%9%
1919
March1st to 15thNight
60%38%16%9%1
2148
16th to endNight
47%310%18%17%2
2001
April1st to 15thNight
54%26%21%12%2
1796
16th to endNight
49%49%18%15%2
1711
May1st to 15thNight
52%37%18%13%3
1440
16th to endNight
48%410%21%13%1
1497
June1st to 15thNight
53%5%11%20%8%
1440
16th to endNight
46%7%10%22%12%
1440
July1st to 15thNight
36%418%27%12%
1360
16th to endNight
37%6%18%26%10%
1418
August1st to 15thNight
41%7%18%24%7%
1446
16th to endNight
35%417%31%9%
1883
September1st to 15thNight
44%5%13%25%10%
1768
16th to endNight
40%413%32%9%
1787
October1st to 15thNight
51%311%22%10%
1972
16th to endNight
61%211%16%6%
2241
November1st to 15thNight
54%412%17%8%1
2304
16th to endNight
65%38%16%5%
2520
December1st to 15thNight
70%38%14%3
2520
16th to endNight
70%27%11%6%
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
31%18%28%18%3
60
16th to endDay
37%18%28%9%6%
64
February1st to 15thDay
35%25%32%33
88
16th to endDay
30%21%29%14%3
212
March1st to 15thDay
28%21%30%18%1
270
16th to endDay
27%17%29%15%8%2
288
April1st to 15thDay
32%18%25%15%6%1
270
16th to endDay
29%16%25%17%8%1
270
May1st to 15thDay
34%14%27%14%7%
288
16th to endDay
27%15%32%17%6%
331
June1st to 15thDay
31%12%33%15%6%
315
16th to endDay
23%13%35%20%6%1
315
July1st to 15thDay
21%8%34%25%7%2
305
16th to endDay
18%6%32%32%8%2
326
August1st to 15thDay
18%8%27%29%11%4
313
16th to endDay
18%9%28%21%13%8%
332
September1st to 15thDay
26%7%23%21%14%7%
299
16th to endDay
24%11%22%20%13%7%
254
October1st to 15thDay
29%16%21%18%10%2
255
16th to endDay
37%14%26%13%8%
249
November1st to 15thDay
26%16%23%25%6%1
208
16th to endDay
38%20%26%15%
60
December1st to 15thDay
45%16%23%13%1
60
16th to endDay
43%28%25%3
64
January1st to 15thNight
30%18%30%16%4
720
16th to endNight
21%17%33%19%6%1
768
February1st to 15thNight
20%19%34%19%4
704
16th to endNight
25%18%31%19%4
631
March1st to 15thNight
28%17%31%20%2
720
16th to endNight
23%14%29%23%6%1
768
April1st to 15thNight
31%14%25%23%4
718
16th to endNight
28%16%26%18%9%
631
May1st to 15thNight
26%9%29%23%8%1
360
16th to endNight
22%9%35%22%9%
375
June1st to 15thNight
24%10%28%28%6%1
360
16th to endNight
20%6%22%34%15%1
360
July1st to 15thNight
15%7%22%36%16%1
340
16th to endNight
12%5%24%39%16%1
376
August1st to 15thNight
16%219%40%19%1
375
16th to endNight
15%6%24%30%20%2
737
September1st to 15thNight
21%5%24%33%14%
707
16th to endNight
21%7%23%28%16%1
657
October1st to 15thNight
24%13%25%25%9%
660
16th to endNight
34%13%24%21%5%
704
November1st to 15thNight
27%14%27%20%8%1
700
16th to endNight
31%19%23%15%8%1
720
December1st to 15thNight
33%19%25%16%3
720
16th to endNight
36%16%27%14%31
768
Page generated at 2017-09-13 07:39:15. Version ac04

Copyright 2017 A. Danko


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