ROC St-Romain
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the ROC St-Romain clear sky chart from 2005-11-06 to 2024-01-27.

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
22%
22823
10%
75090
6%
22779
28%
22779
11%
57633

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 10thNight
7%
760
5%
2649
1%
757
12%
757
4%
2311
January11th to 20thNight
10%
760
5%
2660
2%
760
13%
760
4%
2298
January21st to endNight
13%
820
7%
2868
3%
820
19%
820
7%
2340
February1st to 10thNight
10%
720
8%
2476
3%
720
17%
720
7%
2046
February11th to 20thNight
8%
703
7%
2100
1%
700
16%
700
6%
1762
February21st to endNight
12%
592
12%
1776
3%
592
23%
592
10%
1420
March1st to 10thNight
14%
720
12%
2160
5%
720
22%
720
10%
1701
March11th to 20thNight
16%
720
12%
2063
4%
720
23%
720
11%
1615
March21st to endNight
22%
792
16%
2057
6%
792
29%
792
15%
1594
April1st to 10thNight
18%
720
12%
1800
3%
720
23%
720
15%
1422
April11th to 20thNight
24%
633
15%
1697
5%
633
30%
633
19%
1254
April21st to endNight
19%
540
13%
1620
5%
540
26%
540
13%
1217
May1st to 10thNight
20%
540
13%
1620
7%
540
27%
540
16%
1191
May11th to 20thNight
26%
368
16%
1430
12%
368
38%
368
14%
980
May21st to endNight
29%
389
11%
1551
10%
388
39%
388
15%
1052
June1st to 10thNight
27%
360
8%
1337
6%
360
35%
360
12%
975
June11th to 20thNight
39%
360
12%
1260
11%
360
45%
360
18%
842
June21st to endNight
33%
360
8%
1337
9%
360
37%
360
14%
975
July1st to 10thNight
36%
350
9%
1400
11%
350
43%
350
17%
910
July11th to 20thNight
41%
348
11%
1392
14%
348
47%
348
16%
925
July21st to endNight
42%
394
11%
1486
13%
372
44%
372
16%
1001
August1st to 10thNight
50%
389
11%
1453
11%
387
52%
387
19%
952
August11th to 20thNight
43%
532
14%
1596
8%
532
47%
532
20%
1115
August21st to endNight
38%
711
17%
1899
8%
711
42%
711
24%
1316
September1st to 10thNight
38%
720
10%
1800
4%
720
40%
720
26%
1272
September11th to 20thNight
41%
720
16%
1970
10%
720
44%
720
26%
1311
September21st to endNight
35%
720
19%
1980
12%
720
41%
720
24%
1350
October1st to 10thNight
32%
720
17%
1980
10%
720
38%
720
21%
1422
October11th to 20thNight
25%
720
11%
2285
5%
720
32%
720
13%
1745
October21st to endNight
16%
792
10%
2574
4%
792
24%
792
10%
2018
November1st to 10thNight
18%
740
11%
2407
6%
740
25%
740
10%
1849
November11th to 20thNight
19%
760
14%
2470
9%
760
26%
760
10%
1925
November21st to endNight
16%
798
9%
2678
5%
798
21%
798
8%
2175
December1st to 10thNight
10%
850
4%
2850
1%
850
14%
850
4%
2475
December11th to 20thNight
11%
850
5%
3501
2%
848
15%
848
4%
3032
December21st to endNight
8%
852
4%
4908
1%
841
13%
841
2%
3845

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%12%5%8%6%35%45%6%26%
74651
Night
19%14%5%9%6%34445%26%
75365
TransparencyDay
59%6%10%16%8%1
74356
Night
60%6%10%16%7%1
75195
SeeingDay
28%19%29%17%6%1
14004
Night
26%17%29%21%7%1
22834

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 10thDay
15%19%10%13%11%46%5%3410%
1517
11th to 20thDay
16%19%8%14%9%3443317%
1520
21st to endDay
10%14%8%13%11%5%7%445%19%
1632
February1st to 10thDay
13%19%7%13%11%5%6%34316%
1479
11th to 20thDay
14%19%10%14%8%45%34416%
1748
21st to endDay
13%18%7%11%8%5%6%5%35%19%
1480
March1st to 10thDay
15%15%7%12%9%34345%23%
1797
11th to 20thDay
16%16%7%7%8%45%34427%
1895
21st to endDay
18%17%5%10%6%4343326%
2296
April1st to 10thDay
23%16%5%9%7%3433424%
2160
11th to 20thDay
19%15%35%425%345%34%
2212
21st to endDay
25%14%47%5%23346%27%
2340
May1st to 10thDay
24%10%47%5%34336%31%
2340
11th to 20thDay
21%10%36%5%3445%7%31%
2478
21st to endDay
20%9%36%6%45%5%6%8%28%
2725
June1st to 10thDay
29%8%35%5%25%5%5%7%25%
2618
11th to 20thDay
21%6%35%6%45%6%6%8%32%
2700
21st to endDay
24%8%47%6%45%5%5%6%26%
2617
July1st to 10thDay
19%7%36%6%36%5%6%7%32%
2520
11th to 20thDay
18%7%37%6%46%5%6%9%30%
2520
21st to endDay
22%7%36%5%36%5%6%8%30%
2744
August1st to 10thDay
22%6%37%6%46%5%7%9%27%
2458
11th to 20thDay
18%7%36%6%45%6%7%8%31%
2304
21st to endDay
21%6%25%5%35%6%5%7%35%
2453
September1st to 10thDay
20%6%25%5%3445%6%37%
2160
11th to 20thDay
22%7%25%32345%7%40%
1989
21st to endDay
21%7%35%5%345%6%8%35%
1980
October1st to 10thDay
23%11%36%5%3445%7%30%
1980
11th to 20thDay
21%14%47%6%445%5%5%24%
1673
21st to endDay
27%20%36%43434421%
1782
November1st to 10thDay
21%18%5%6%5%3434428%
1671
11th to 20thDay
18%17%8%10%6%24445%22%
1710
21st to endDay
19%19%6%11%7%3434419%
1497
December1st to 10thDay
21%22%9%12%7%3443313%
1330
11th to 20thDay
20%18%9%10%7%45%23420%
1668
21st to endDay
24%19%6%13%8%3432315%
2658
January1st to 10thNight
15%20%9%15%9%5%5%43312%
2649
11th to 20thNight
15%17%9%14%9%5%6%43315%
2660
21st to endNight
11%14%7%14%10%6%8%445%17%
2868
February1st to 10thNight
12%16%7%13%10%5%6%43420%
2476
11th to 20thNight
13%18%8%14%9%5%5%43319%
2098
21st to endNight
13%17%8%10%7%45%5%3424%
1776
March1st to 10thNight
15%16%8%9%7%3443425%
2150
11th to 20thNight
16%15%6%9%6%36%445%27%
2062
21st to endNight
17%15%5%9%5%34345%29%
2057
April1st to 10thNight
22%16%6%7%5%34345%27%
1800
11th to 20thNight
20%12%36%5%345%46%33%
1697
21st to endNight
23%13%46%5%3445%5%29%
1620
May1st to 10thNight
25%11%36%5%23446%30%
1620
11th to 20thNight
19%9%47%6%34446%34%
1429
21st to endNight
22%7%26%5%3445%7%35%
1550
June1st to 10thNight
27%9%35%5%4445%6%27%
1337
11th to 20thNight
21%6%35%425%46%8%35%
1260
21st to endNight
21%7%36%6%35%6%5%7%30%
1337
July1st to 10thNight
16%7%347%35%5%7%9%35%
1440
11th to 20thNight
16%6%36%5%45%6%8%8%33%
1440
21st to endNight
18%7%35%5%35%5%6%6%36%
1574
August1st to 10thNight
18%5%345%35%5%6%9%37%
1463
11th to 20thNight
17%7%25%436%5%5%7%37%
1596
21st to endNight
18%6%26%5%3345%6%41%
1899
September1st to 10thNight
19%7%26%5%345%6%7%38%
1800
11th to 20thNight
20%5%245%3345%6%44%
1970
21st to endNight
21%7%2343335%7%42%
1980
October1st to 10thNight
21%9%25%4345%46%36%
1980
11th to 20thNight
22%13%37%6%44445%27%
2285
21st to endNight
27%16%36%5%23445%24%
2574
November1st to 10thNight
21%16%5%7%5%3445%5%26%
2407
11th to 20thNight
19%15%7%9%6%23436%25%
2470
21st to endNight
17%19%8%11%7%3333421%
2678
December1st to 10thNight
21%19%9%12%8%4443313%
2850
11th to 20thNight
19%19%9%14%9%4433314%
3531
21st to endNight
24%21%5%9%6%3422321%
4982

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 10thDay
78%47%8%3
1518
11th to 20thDay
73%46%11%5%1
1520
21st to endDay
67%5%7%12%8%1
1632
February1st to 10thDay
75%45%9%6%1
1479
11th to 20thDay
74%37%9%5%1
1757
21st to endDay
68%5%6%13%5%2
1480
March1st to 10thDay
64%6%7%13%7%2
1800
11th to 20thDay
61%5%9%13%11%2
1895
21st to endDay
64%47%14%9%2
2296
April1st to 10thDay
66%48%13%8%2
2160
11th to 20thDay
54%5%9%19%12%1
2212
21st to endDay
61%5%7%15%9%3
2340
May1st to 10thDay
57%47%18%12%2
2340
11th to 20thDay
52%7%12%18%10%1
2482
21st to endDay
54%8%12%16%10%1
2725
June1st to 10thDay
57%7%10%19%6%1
2618
11th to 20thDay
50%7%12%21%9%1
2700
21st to endDay
59%7%10%17%7%
2617
July1st to 10thDay
49%8%15%21%7%
2450
11th to 20thDay
50%8%14%22%6%
2445
21st to endDay
53%9%13%19%6%
2591
August1st to 10thDay
52%7%18%20%2
2444
11th to 20thDay
49%9%16%18%9%
2304
21st to endDay
48%7%14%21%10%
2453
September1st to 10thDay
47%7%14%21%10%1
2160
11th to 20thDay
45%6%11%26%12%
1989
21st to endDay
47%7%12%24%10%1
1980
October1st to 10thDay
53%7%13%19%8%
1980
11th to 20thDay
61%7%12%15%4
1673
21st to endDay
69%49%12%6%1
1782
November1st to 10thDay
61%6%10%16%7%
1671
11th to 20thDay
67%5%8%13%6%1
1710
21st to endDay
69%5%11%12%2
1497
December1st to 10thDay
78%46%8%4
1330
11th to 20thDay
70%5%6%12%7%1
1668
21st to endDay
77%45%8%6%1
2658
January1st to 10thNight
78%47%8%3
2649
11th to 20thNight
76%5%6%8%41
2660
21st to endNight
69%5%8%11%5%2
2868
February1st to 10thNight
70%5%7%12%6%1
2476
11th to 20thNight
72%47%10%6%1
2100
21st to endNight
65%5%6%14%10%1
1776
March1st to 10thNight
63%5%7%15%8%1
2160
11th to 20thNight
60%6%8%12%11%2
2063
21st to endNight
59%5%8%18%8%3
2057
April1st to 10thNight
62%38%14%12%1
1800
11th to 20thNight
52%6%10%21%10%2
1697
21st to endNight
56%6%11%16%9%2
1620
May1st to 10thNight
56%49%17%13%1
1620
11th to 20thNight
52%5%11%19%11%1
1430
21st to endNight
49%8%12%19%11%1
1551
June1st to 10thNight
57%6%12%19%7%
1337
11th to 20thNight
47%7%11%23%10%2
1260
21st to endNight
53%8%11%19%8%
1337
July1st to 10thNight
43%10%18%20%9%
1400
11th to 20thNight
44%11%15%21%8%
1392
21st to endNight
48%8%15%21%7%
1486
August1st to 10thNight
43%10%20%23%4
1453
11th to 20thNight
45%10%16%21%7%
1596
21st to endNight
44%7%14%25%10%
1899
September1st to 10thNight
45%6%16%24%9%
1800
11th to 20thNight
41%7%14%28%9%1
1970
21st to endNight
43%7%12%26%11%1
1980
October1st to 10thNight
49%6%11%22%12%
1980
11th to 20thNight
58%6%12%18%5%
2285
21st to endNight
64%5%10%13%7%1
2574
November1st to 10thNight
62%5%11%15%6%1
2407
11th to 20thNight
62%6%10%13%8%1
2470
21st to endNight
68%5%11%12%4
2678
December1st to 10thNight
77%47%8%3
2850
11th to 20thNight
75%6%6%8%5%
3532
21st to endNight
70%48%13%5%
4982

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 10thDay
29%26%33%12%
180
11th to 20thDay
34%23%31%11%21
180
21st to endDay
22%30%34%12%11
188
February1st to 10thDay
36%29%25%7%3
197
11th to 20thDay
29%33%30%6%2
416
21st to endDay
30%27%27%14%1
346
March1st to 10thDay
26%28%31%11%3
420
11th to 20thDay
30%26%27%12%41
420
21st to endDay
31%23%24%14%7%1
462
April1st to 10thDay
39%18%26%11%5%1
420
11th to 20thDay
34%23%24%13%5%1
412
21st to endDay
37%20%27%10%41
420
May1st to 10thDay
34%19%29%14%41
423
11th to 20thDay
28%17%30%19%41
447
21st to endDay
21%23%32%18%5%
485
June1st to 10thDay
34%17%29%15%6%
548
11th to 20thDay
24%16%27%23%10%
630
21st to endDay
24%16%31%18%9%1
547
July1st to 10thDay
20%13%33%26%8%
445
11th to 20thDay
20%15%36%20%8%1
444
21st to endDay
23%13%32%26%5%1
488
August1st to 10thDay
22%13%29%24%10%1
446
11th to 20thDay
20%10%29%28%10%2
439
21st to endDay
26%16%23%19%11%5%
495
September1st to 10thDay
20%14%31%21%9%4
450
11th to 20thDay
26%10%26%20%13%5%
450
21st to endDay
21%16%29%22%8%5%
450
October1st to 10thDay
27%18%24%18%10%3
450
11th to 20thDay
30%16%29%14%9%1
376
21st to endDay
42%18%24%14%2
396
November1st to 10thDay
36%17%28%15%4
365
11th to 20thDay
28%22%30%13%6%1
370
21st to endDay
31%24%27%15%3
241
December1st to 10thDay
38%22%24%12%4
180
11th to 20thDay
35%29%23%9%3
180
21st to endDay
38%27%24%9%21
198
January1st to 10thNight
26%26%33%13%2
760
11th to 20thNight
26%26%32%14%3
760
21st to endNight
20%25%35%17%3
820
February1st to 10thNight
22%28%34%14%3
720
11th to 20thNight
25%25%35%14%2
703
21st to endNight
27%20%35%17%2
592
March1st to 10thNight
26%20%35%17%2
720
11th to 20thNight
28%22%30%16%5%
720
21st to endNight
27%17%27%23%5%1
792
April1st to 10thNight
32%18%28%17%4
720
11th to 20thNight
28%13%31%22%6%
633
21st to endNight
31%18%28%18%5%
540
May1st to 10thNight
31%14%31%18%5%1
540
11th to 20thNight
23%12%33%26%5%1
368
21st to endNight
22%11%34%27%6%
389
June1st to 10thNight
30%8%28%26%7%
360
11th to 20thNight
22%6%26%34%11%
360
21st to endNight
21%11%26%30%11%
360
July1st to 10thNight
18%5%35%29%11%1
350
11th to 20thNight
16%5%29%36%11%1
348
21st to endNight
20%6%25%38%11%
394
August1st to 10thNight
19%422%39%17%1
389
11th to 20thNight
17%6%27%32%17%1
532
21st to endNight
21%9%25%29%14%2
711
September1st to 10thNight
21%8%28%31%11%1
720
11th to 20thNight
23%9%23%27%16%2
720
21st to endNight
23%10%28%26%12%1
720
October1st to 10thNight
25%12%27%25%11%1
720
11th to 20thNight
29%14%27%20%8%2
720
21st to endNight
35%17%28%17%3
792
November1st to 10thNight
32%16%28%19%5%
740
11th to 20thNight
28%20%29%15%8%1
760
21st to endNight
29%22%26%17%41
798
December1st to 10thNight
33%22%27%14%4
850
11th to 20thNight
30%25%25%15%4
850
21st to endNight
34%24%26%13%3
863
Page generated at 2024-01-24 09:37:29. Version ac07

Copyright 2024 Attilla Danko


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