Observatoire du Mont-Cosmos
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire du Mont-Cosmos clear sky chart from 2005-11-05 to 2018-02-22.

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
25%
15314
11%
48969
6%
15282
31%
15282
13%
36638

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
11%
780
10%
2716
4%
776
19%
776
6%
2208
January16th to endNight
15%
832
9%
2912
3%
832
23%
832
8%
2263
February1st to 15thNight
16%
764
8%
2542
3%
761
23%
761
7%
2054
February16th to endNight
14%
659
12%
1976
3%
659
25%
659
10%
1545
March1st to 15thNight
18%
720
14%
2156
6%
720
26%
720
13%
1627
March16th to endNight
26%
768
16%
2030
6%
768
33%
768
17%
1504
April1st to 15thNight
22%
718
14%
1796
5%
718
28%
718
17%
1383
April16th to endNight
23%
540
15%
1620
6%
540
30%
540
16%
1151
May1st to 15thNight
28%
474
12%
1554
10%
474
33%
474
15%
1125
May16th to endNight
28%
375
10%
1494
9%
374
37%
374
12%
1063
June1st to 15thNight
31%
360
7%
1260
5%
360
35%
360
13%
938
June16th to endNight
40%
360
8%
1260
8%
360
43%
360
18%
867
July1st to 15thNight
41%
340
8%
1354
10%
340
45%
340
17%
905
July16th to endNight
46%
376
10%
1418
12%
354
48%
354
17%
922
August1st to 15thNight
44%
428
11%
1499
9%
426
47%
426
18%
1017
August16th to endNight
45%
642
16%
1788
9%
642
49%
642
26%
1203
September1st to 15thNight
37%
720
11%
1854
5%
720
39%
720
24%
1319
September16th to endNight
41%
717
19%
1980
12%
717
47%
717
28%
1292
October1st to 15thNight
30%
720
15%
2074
8%
720
36%
720
19%
1490
October16th to endNight
20%
768
10%
2496
5%
768
27%
768
11%
1931
November1st to 15thNight
25%
760
15%
2472
10%
760
33%
760
13%
1820
November16th to endNight
20%
802
13%
2732
7%
802
28%
802
10%
2080
December1st to 15thNight
14%
825
5%
2925
1%
825
19%
825
6%
2415
December16th to endNight
13%
866
9%
3061
3%
866
21%
866
5%
2516

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%11%47%6%34445%27%
49279
Night
18%11%47%6%34445%28%
49139
TransparencyDay
58%6%10%17%7%
48967
Night
56%6%11%17%7%
48969
SeeingDay
24%16%29%18%9%2
6480
Night
23%15%28%23%8%
15314

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
16%15%7%13%8%44425%17%
1552
16th to endDay
10%13%7%11%9%45%5%4422%
1664
February1st to 15thDay
11%19%7%11%10%35%33418%
1647
16th to endDay
13%18%6%11%8%3444321%
1644
March1st to 15thDay
17%14%6%8%6%33335%26%
1793
16th to endDay
16%11%5%8%5%3443431%
2193
April1st to 15thDay
22%11%47%42333430%
2152
16th to endDay
23%11%25%423335%32%
2340
May1st to 15thDay
23%9%47%5%34435%28%
2406
16th to endDay
22%10%47%5%3446%5%24%
2618
June1st to 15thDay
26%7%35%5%35%46%7%24%
2700
16th to endDay
23%7%46%6%35%45%7%24%
2700
July1st to 15thDay
17%6%36%6%35%5%5%8%29%
2523
16th to endDay
19%7%36%6%36%5%6%7%26%
2654
August1st to 15thDay
20%8%36%7%36%5%5%8%24%
2438
16th to endDay
16%6%36%5%34447%37%
2411
September1st to 15thDay
22%7%25%42335%6%35%
2106
16th to endDay
17%6%25%323447%41%
1980
October1st to 15thDay
21%11%25%425%446%30%
1884
16th to endDay
25%15%37%6%4443420%
1728
November1st to 15thDay
22%12%46%6%3434426%
1716
16th to endDay
20%17%5%9%42332423%
1554
December1st to 15thDay
21%19%7%9%6%3323317%
1365
16th to endDay
22%17%8%10%6%2434317%
1511
January1st to 15thNight
16%14%7%11%8%35%43420%
2716
16th to endNight
10%12%7%12%9%36%6%45%21%
2912
February1st to 15thNight
9%14%5%11%11%5%6%45%419%
2541
16th to endNight
15%15%6%10%7%35%33424%
1976
March1st to 15thNight
18%12%46%6%3433429%
2143
16th to endNight
14%12%5%7%5%3444433%
2030
April1st to 15thNight
21%13%36%5%245%45%27%
1796
16th to endNight
21%8%36%5%23335%36%
1620
May1st to 15thNight
23%9%35%5%24445%30%
1554
16th to endNight
23%7%47%5%23445%29%
1492
June1st to 15thNight
23%9%36%6%25%45%5%26%
1260
16th to endNight
17%6%36%5%35%5%7%6%31%
1260
July1st to 15thNight
17%5%26%5%35%45%8%34%
1434
16th to endNight
14%5%35%6%35%5%5%7%37%
1514
August1st to 15thNight
16%7%35%435%45%9%34%
1509
16th to endNight
14%424435%45%8%39%
1788
September1st to 15thNight
20%6%25%3235%46%38%
1854
16th to endNight
18%5%24223345%46%
1980
October1st to 15thNight
20%7%25%5%2445%434%
2074
16th to endNight
25%12%37%5%34335%25%
2496
November1st to 15thNight
19%10%36%6%35%445%29%
2472
16th to endNight
19%14%6%8%5%2433427%
2732
December1st to 15thNight
20%16%6%11%7%4433318%
2925
16th to endNight
19%18%6%9%7%35%44318%
3061

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
69%5%7%10%5%
1553
16th to endDay
62%6%8%16%6%
1664
February1st to 15thDay
69%5%7%11%5%
1650
16th to endDay
66%37%13%6%1
1644
March1st to 15thDay
61%39%13%10%1
1803
16th to endDay
55%5%7%17%12%1
2193
April1st to 15thDay
57%38%17%9%3
2152
16th to endDay
54%48%17%12%2
2340
May1st to 15thDay
57%5%8%17%9%1
2406
16th to endDay
59%7%9%15%7%
2622
June1st to 15thDay
58%6%11%15%7%
2700
16th to endDay
58%6%9%17%7%
2700
July1st to 15thDay
50%7%15%19%7%
2374
16th to endDay
55%8%12%17%4
2487
August1st to 15thDay
55%8%17%14%3
2424
16th to endDay
45%7%15%24%8%
2411
September1st to 15thDay
48%6%12%21%9%
2106
16th to endDay
42%5%13%27%10%
1980
October1st to 15thDay
54%5%12%22%5%
1884
16th to endDay
67%48%17%2
1728
November1st to 15thDay
59%6%11%15%6%
1716
16th to endDay
64%410%14%5%
1554
December1st to 15thDay
72%48%11%2
1365
16th to endDay
72%5%5%8%6%
1511
January1st to 15thNight
68%5%7%13%4
2716
16th to endNight
63%5%9%14%6%
2912
February1st to 15thNight
66%6%7%12%5%
2542
16th to endNight
63%38%12%10%1
1976
March1st to 15thNight
57%5%8%17%9%1
2156
16th to endNight
52%5%9%17%12%2
2030
April1st to 15thNight
56%47%17%10%2
1796
16th to endNight
50%6%9%16%13%3
1620
May1st to 15thNight
54%5%9%15%13%1
1554
16th to endNight
55%6%10%17%9%
1494
June1st to 15thNight
58%5%10%16%7%1
1260
16th to endNight
47%7%14%20%8%
1260
July1st to 15thNight
45%8%16%20%7%
1354
16th to endNight
44%9%17%19%9%
1418
August1st to 15thNight
46%8%18%22%3
1499
16th to endNight
40%8%17%26%7%
1788
September1st to 15thNight
45%7%13%24%8%
1854
16th to endNight
39%5%15%27%11%
1980
October1st to 15thNight
49%6%11%23%8%
2074
16th to endNight
61%5%10%16%5%
2496
November1st to 15thNight
55%6%13%16%7%
2472
16th to endNight
60%410%17%6%
2732
December1st to 15thNight
71%49%11%3
2925
16th to endNight
69%5%8%9%6%
3061

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%24%41%14%1
90
16th to endDay
19%33%36%8%11
96
February1st to 15thDay
24%23%32%15%3
178
16th to endDay
21%21%33%18%4
265
March1st to 15thDay
24%20%30%18%41
270
16th to endDay
22%19%26%16%12%2
288
April1st to 15thDay
30%17%27%18%41
270
16th to endDay
24%19%32%12%8%2
270
May1st to 15thDay
33%12%28%15%7%1
288
16th to endDay
21%16%35%17%6%1
331
June1st to 15thDay
29%13%25%21%9%
495
16th to endDay
26%10%30%22%8%
495
July1st to 15thDay
19%12%32%23%11%1
308
16th to endDay
19%8%31%28%10%1
326
August1st to 15thDay
18%10%32%18%15%4
313
16th to endDay
17%12%25%21%15%6%
332
September1st to 15thDay
21%9%27%21%12%6%
315
16th to endDay
13%16%27%21%13%8%
314
October1st to 15thDay
25%16%26%15%11%4
304
16th to endDay
32%19%25%14%5%1
288
November1st to 15thDay
28%19%21%18%10%
280
16th to endDay
32%19%20%18%8%1
178
December1st to 15thDay
36%20%27%11%22
90
16th to endDay
23%34%28%12%1
96
January1st to 15thNight
24%23%31%16%3
780
16th to endNight
19%19%33%21%4
832
February1st to 15thNight
16%22%36%19%5%
764
16th to endNight
24%20%32%17%4
659
March1st to 15thNight
25%18%33%18%3
720
16th to endNight
21%17%29%24%6%
768
April1st to 15thNight
27%15%29%21%5%
718
16th to endNight
25%15%28%22%8%
540
May1st to 15thNight
26%12%25%25%8%
474
16th to endNight
24%9%29%28%8%
375
June1st to 15thNight
28%6%26%27%11%
360
16th to endNight
20%6%27%35%10%
360
July1st to 15thNight
19%5%27%34%12%
340
16th to endNight
15%325%43%11%
376
August1st to 15thNight
21%323%30%19%
428
16th to endNight
17%5%26%32%15%2
642
September1st to 15thNight
22%8%25%29%12%1
720
16th to endNight
21%9%25%26%16%1
717
October1st to 15thNight
20%13%30%23%10%1
720
16th to endNight
33%16%24%18%7%
768
November1st to 15thNight
26%17%23%22%9%
760
16th to endNight
26%20%28%15%8%
802
December1st to 15thNight
29%20%28%16%5%
825
16th to endNight
28%21%26%17%41
866
Page generated at 2018-02-23 11:21:40. Version ac04

Copyright 2018 A. Danko


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