Cluny
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cluny clear sky chart from 2005-11-06 to 2024-01-12.

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
43%
23534
14%
74579
9%
23504
48%
23504
22%
49021

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
36%
946
12%
2836
8%
946
40%
946
17%
2085
January11th to 20thNight
37%
910
14%
2730
8%
910
42%
910
20%
1930
January21st to endNight
35%
825
18%
2805
11%
825
45%
825
17%
1926
February1st to 10thNight
39%
720
13%
2479
12%
720
43%
720
16%
1732
February11th to 20thNight
36%
702
13%
2273
11%
700
41%
700
17%
1616
February21st to endNight
43%
592
15%
1858
13%
592
48%
592
21%
1269
March1st to 10thNight
39%
720
15%
2147
12%
720
42%
720
19%
1541
March11th to 20thNight
40%
720
17%
1980
9%
720
47%
720
23%
1381
March21st to endNight
39%
792
9%
2178
4%
792
42%
792
19%
1617
April1st to 10thNight
38%
635
14%
1734
6%
635
44%
635
21%
1258
April11th to 20thNight
40%
533
15%
1601
11%
533
44%
533
21%
1120
April21st to endNight
41%
540
12%
1620
9%
540
45%
540
22%
1093
May1st to 10thNight
42%
514
9%
1511
7%
514
46%
514
21%
1040
May11th to 20thNight
51%
354
14%
1239
14%
354
55%
354
25%
749
May21st to endNight
41%
389
6%
1358
4%
388
44%
388
17%
933
June1st to 10thNight
44%
360
2%
1260
1%
360
45%
360
18%
854
June11th to 20thNight
40%
360
1%
1260
0%
360
40%
360
16%
882
June21st to endNight
56%
360
1%
1260
0%
360
56%
360
29%
720
July1st to 10thNight
64%
350
3%
1225
1%
350
64%
350
29%
711
July11th to 20thNight
56%
348
6%
1218
5%
348
58%
348
28%
718
July21st to endNight
65%
394
15%
1311
16%
372
71%
372
41%
632
August1st to 10thNight
58%
378
13%
1444
16%
376
62%
376
25%
820
August11th to 20thNight
63%
534
17%
1602
15%
534
66%
534
38%
894
August21st to endNight
60%
594
22%
1782
16%
594
64%
594
37%
1004
September1st to 10thNight
56%
580
18%
1712
13%
580
58%
580
31%
1052
September11th to 20thNight
53%
720
19%
1980
13%
720
57%
720
33%
1250
September21st to endNight
48%
720
22%
1980
14%
720
54%
720
35%
1199
October1st to 10thNight
48%
720
20%
2092
12%
720
55%
720
27%
1343
October11th to 20thNight
43%
720
18%
2240
9%
720
52%
720
27%
1413
October21st to endNight
38%
792
17%
2574
10%
792
46%
792
21%
1686
November1st to 10thNight
35%
884
16%
2549
9%
884
42%
884
21%
1782
November11th to 20thNight
34%
950
18%
2669
9%
950
43%
950
24%
1816
November21st to endNight
38%
950
13%
2850
8%
950
43%
950
22%
1956
December1st to 10thNight
38%
950
15%
2850
9%
950
42%
950
19%
2006
December11th to 20thNight
37%
949
12%
3465
6%
949
42%
949
16%
2336
December21st to endNight
35%
1029
11%
4907
8%
1026
41%
1026
14%
2657

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
9%8%37%6%45%5%6%8%38%
74629
Night
7%8%48%7%46%6%6%9%37%
75092
TransparencyDay
41%9%16%23%10%2
74311
Night
42%9%16%22%11%2
74928
SeeingDay
11%7%25%31%20%6%
14266
Night
11%6%29%36%16%2
23557

By Month

Percentage Cloud Cover NW (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
6%8%5%10%8%5%6%6%7%9%30%
1329
11th to 20thDay
5%9%5%10%8%5%5%7%8%8%30%
1270
21st to endDay
6%10%5%10%7%48%6%8%8%27%
1566
February1st to 10thDay
6%11%5%10%8%5%7%6%6%8%28%
1480
11th to 20thDay
7%12%5%9%9%5%7%5%6%9%25%
1575
21st to endDay
413%6%10%9%5%6%7%5%7%27%
1394
March1st to 10thDay
5%12%5%12%10%46%5%5%7%29%
1813
11th to 20thDay
7%9%5%9%7%46%5%6%8%33%
1979
21st to endDay
9%13%5%8%8%45%6%6%8%29%
2178
April1st to 10thDay
9%10%5%10%8%5%5%6%6%7%29%
2222
11th to 20thDay
10%11%48%6%45%6%6%8%32%
2310
21st to endDay
11%9%47%8%46%6%6%7%32%
2340
May1st to 10thDay
13%10%47%7%46%6%5%8%32%
2446
11th to 20thDay
8%6%27%6%35%6%7%8%41%
2654
21st to endDay
18%7%36%6%35%45%9%33%
2917
June1st to 10thDay
14%7%35%6%36%6%8%8%33%
2700
11th to 20thDay
16%8%37%5%46%5%7%8%30%
2700
21st to endDay
8%425%5%36%6%7%9%45%
2700
July1st to 10thDay
6%4245%45%7%7%11%45%
2700
11th to 20thDay
8%424435%5%6%10%49%
2700
21st to endDay
4313325%5%6%8%59%
2925
August1st to 10thDay
7%5%25%435%5%6%9%49%
2486
11th to 20thDay
7%324445%5%6%9%51%
2299
21st to endDay
8%4244345%6%10%51%
2574
September1st to 10thDay
9%6%25%435%447%51%
2246
11th to 20thDay
14%7%25%5%2446%7%45%
1980
21st to endDay
9%6%35%5%3446%10%46%
1980
October1st to 10thDay
12%9%37%6%34446%42%
1868
11th to 20thDay
8%6%37%5%35%5%6%8%43%
1716
21st to endDay
7%9%38%6%5%6%6%6%7%37%
1782
November1st to 10thDay
11%15%5%9%5%445%6%8%30%
1510
11th to 20thDay
6%11%5%8%8%46%46%7%36%
1506
21st to endDay
5%11%5%7%7%45%6%7%9%36%
1330
December1st to 10thDay
7%12%5%10%9%5%6%5%5%7%29%
1330
11th to 20thDay
311%6%11%7%47%6%6%9%31%
1682
21st to endDay
38%47%5%35%5%6%8%47%
2442
January1st to 10thNight
411%6%9%11%5%7%6%7%9%26%
2836
11th to 20thNight
5%11%5%9%7%47%6%7%9%30%
2730
21st to endNight
5%11%49%9%46%5%6%8%31%
2805
February1st to 10thNight
5%9%5%11%9%5%6%6%6%8%30%
2479
11th to 20thNight
6%11%6%9%8%46%6%7%7%28%
2272
21st to endNight
49%6%11%7%46%5%6%8%33%
1858
March1st to 10thNight
5%10%6%10%9%46%5%6%9%30%
2147
11th to 20thNight
5%10%5%9%7%45%6%7%9%33%
1980
21st to endNight
7%13%5%9%6%5%6%6%6%9%27%
2178
April1st to 10thNight
7%10%5%9%8%46%6%7%9%29%
1734
11th to 20thNight
8%11%48%8%37%5%6%9%31%
1601
21st to endNight
9%8%47%6%5%6%6%8%8%34%
1620
May1st to 10thNight
10%12%46%6%35%5%7%8%34%
1511
11th to 20thNight
11%5%36%5%46%5%6%9%42%
1239
21st to endNight
15%8%46%5%36%5%6%8%32%
1358
June1st to 10thNight
14%7%37%6%46%5%8%8%33%
1260
11th to 20thNight
11%7%37%8%5%7%6%7%7%30%
1260
21st to endNight
7%5%25%6%45%6%6%8%47%
1260
July1st to 10thNight
7%425%6%45%6%7%10%45%
1260
11th to 20thNight
7%5%246%45%7%7%11%45%
1260
21st to endNight
32244345%6%10%57%
1388
August1st to 10thNight
5%436%7%35%6%5%9%46%
1452
11th to 20thNight
5%324435%5%7%10%50%
1602
21st to endNight
7%5%25%4345%6%9%51%
1782
September1st to 10thNight
9%6%25%5%346%5%7%47%
1712
11th to 20thNight
12%6%25%42445%7%48%
1980
21st to endNight
8%5%245%345%6%9%49%
1980
October1st to 10thNight
11%8%35%5%36%46%8%42%
2092
11th to 20thNight
10%8%26%6%35%6%6%9%41%
2240
21st to endNight
6%8%38%7%46%5%7%9%36%
2574
November1st to 10thNight
9%13%47%6%45%5%7%8%33%
2549
11th to 20thNight
5%10%37%7%46%6%7%9%35%
2669
21st to endNight
6%9%48%8%45%6%7%9%34%
2850
December1st to 10thNight
6%11%5%11%8%5%5%5%5%8%32%
2850
11th to 20thNight
39%5%11%8%5%6%5%7%10%32%
3510
21st to endNight
48%46%7%46%5%5%8%44%
5214

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
48%8%15%21%7%2
1329
11th to 20thDay
46%10%15%21%5%2
1270
21st to endDay
49%10%17%15%9%1
1566
February1st to 10thDay
52%9%15%15%8%1
1480
11th to 20thDay
52%9%15%17%6%1
1584
21st to endDay
52%9%12%15%11%
1394
March1st to 10thDay
53%7%17%16%7%
1813
11th to 20thDay
46%9%15%20%9%1
1980
21st to endDay
49%9%19%17%5%1
2178
April1st to 10thDay
50%9%14%17%9%
2222
11th to 20thDay
47%7%14%22%8%1
2310
21st to endDay
48%8%15%19%9%1
2340
May1st to 10thDay
48%9%14%20%9%1
2446
11th to 20thDay
37%9%16%26%11%1
2658
21st to endDay
48%8%14%21%8%1
2918
June1st to 10thDay
43%10%16%21%8%1
2700
11th to 20thDay
48%10%16%18%7%2
2700
21st to endDay
32%9%21%27%9%2
2700
July1st to 10thDay
28%12%21%28%10%2
2626
11th to 20thDay
29%10%20%28%13%1
2619
21st to endDay
20%9%20%32%19%2
2762
August1st to 10thDay
30%9%18%29%11%2
2469
11th to 20thDay
27%9%22%30%11%2
2299
21st to endDay
27%7%21%28%16%2
2574
September1st to 10thDay
32%7%15%27%15%5%
2246
11th to 20thDay
38%7%14%27%13%2
1980
21st to endDay
34%8%16%28%11%3
1980
October1st to 10thDay
42%7%15%26%9%1
1868
11th to 20thDay
37%8%15%27%11%2
1716
21st to endDay
42%9%15%23%11%1
1782
November1st to 10thDay
51%8%13%19%8%2
1510
11th to 20thDay
46%7%15%24%9%
1506
21st to endDay
42%8%18%21%9%2
1330
December1st to 10thDay
52%9%13%15%8%3
1330
11th to 20thDay
47%9%16%23%5%1
1684
21st to endDay
33%7%13%24%18%4
2442
January1st to 10thNight
51%10%13%17%7%2
2836
11th to 20thNight
46%9%17%18%7%2
2730
21st to endNight
48%7%14%17%12%2
2805
February1st to 10thNight
49%8%13%18%9%1
2479
11th to 20thNight
50%8%13%18%10%1
2273
21st to endNight
46%7%14%19%11%2
1858
March1st to 10thNight
48%9%14%21%7%1
2147
11th to 20thNight
45%7%16%19%11%2
1980
21st to endNight
50%10%17%17%6%1
2178
April1st to 10thNight
48%8%14%18%12%1
1734
11th to 20thNight
46%8%14%21%9%1
1601
21st to endNight
42%10%16%22%9%2
1620
May1st to 10thNight
44%10%13%21%11%1
1511
11th to 20thNight
37%8%15%24%14%2
1239
21st to endNight
46%10%15%19%8%2
1358
June1st to 10thNight
46%9%15%21%9%1
1260
11th to 20thNight
46%12%17%17%7%1
1260
21st to endNight
30%10%21%28%10%1
1260
July1st to 10thNight
31%10%21%26%11%2
1225
11th to 20thNight
30%12%18%26%12%2
1218
21st to endNight
19%9%20%31%19%3
1311
August1st to 10thNight
31%11%19%25%11%2
1444
11th to 20thNight
25%8%20%30%15%1
1602
21st to endNight
27%7%16%28%17%5%
1782
September1st to 10thNight
33%8%15%23%15%5%
1712
11th to 20thNight
34%8%13%27%13%5%
1980
21st to endNight
31%8%17%26%15%4
1980
October1st to 10thNight
38%7%15%23%13%2
2092
11th to 20thNight
38%8%17%24%11%3
2240
21st to endNight
41%9%16%24%9%1
2574
November1st to 10thNight
47%8%14%20%10%1
2549
11th to 20thNight
41%9%17%20%12%1
2669
21st to endNight
43%9%18%19%9%2
2850
December1st to 10thNight
49%7%13%20%9%2
2850
11th to 20thNight
44%11%20%19%5%1
3507
21st to endNight
36%7%13%25%15%4
5214

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
35%28%32%19%13%
180
11th to 20thDay
6%9%27%33%18%7%
163
21st to endDay
9%6%24%38%19%5%
176
February1st to 10thDay
11%10%30%33%13%3
178
11th to 20thDay
10%8%25%36%17%3
240
21st to endDay
7%6%27%36%17%7%
260
March1st to 10thDay
10%9%33%29%15%5%
420
11th to 20thDay
9%7%28%35%16%5%
420
21st to endDay
10%9%34%25%15%7%
462
April1st to 10thDay
11%15%30%27%14%3
420
11th to 20thDay
11%10%27%29%17%6%
412
21st to endDay
15%9%27%28%16%4
420
May1st to 10thDay
15%8%23%26%21%7%
505
11th to 20thDay
13%6%21%32%22%6%
625
21st to endDay
18%5%19%28%22%8%
679
June1st to 10thDay
15%6%24%29%22%4
630
11th to 20thDay
16%7%31%29%14%3
630
21st to endDay
9%422%34%23%8%
630
July1st to 10thDay
8%418%34%25%10%
621
11th to 20thDay
11%320%36%22%7%
618
21st to endDay
5%319%35%28%10%
671
August1st to 10thDay
8%421%34%23%10%
447
11th to 20thDay
8%418%30%29%10%
437
21st to endDay
9%7%18%31%22%13%
495
September1st to 10thDay
13%6%26%29%21%5%
450
11th to 20thDay
16%6%20%30%23%5%
450
21st to endDay
14%10%26%30%15%5%
450
October1st to 10thDay
16%8%22%25%21%8%
338
11th to 20thDay
10%6%32%29%16%7%
270
21st to endDay
12%14%30%29%11%3
297
November1st to 10thDay
19%7%27%32%13%3
270
11th to 20thDay
12%9%34%28%15%2
264
21st to endDay
7%5%33%30%16%9%
180
December1st to 10thDay
11%6%32%31%13%8%
180
11th to 20thDay
8%8%34%33%13%2
180
21st to endDay
8%6%22%34%24%6%
198
January1st to 10thNight
8%8%31%36%15%2
950
11th to 20thNight
10%6%34%34%13%2
910
21st to endNight
11%9%32%32%14%3
825
February1st to 10thNight
7%8%30%34%17%4
720
11th to 20thNight
10%6%33%36%13%1
704
21st to endNight
8%425%37%22%4
592
March1st to 10thNight
9%431%37%15%4
720
11th to 20thNight
8%7%31%37%15%2
720
21st to endNight
13%7%27%35%16%2
792
April1st to 10thNight
11%7%28%36%15%1
635
11th to 20thNight
13%6%29%38%13%1
533
21st to endNight
14%7%28%38%12%1
540
May1st to 10thNight
14%7%27%34%17%1
514
11th to 20thNight
12%426%38%19%2
354
21st to endNight
18%5%26%32%17%2
389
June1st to 10thNight
19%5%23%39%12%2
360
11th to 20thNight
16%6%29%35%14%1
360
21st to endNight
9%324%39%23%2
360
July1st to 10thNight
8%418%43%25%1
350
11th to 20thNight
10%323%41%21%1
348
21st to endNight
5%224%43%25%2
394
August1st to 10thNight
8%5%19%40%26%2
378
11th to 20thNight
7%320%45%22%2
534
21st to endNight
9%5%20%43%23%1
594
September1st to 10thNight
12%323%41%20%2
580
11th to 20thNight
15%421%36%23%2
720
21st to endNight
10%5%30%34%18%3
720
October1st to 10thNight
14%426%36%16%3
720
11th to 20thNight
13%431%35%14%3
720
21st to endNight
10%8%34%35%13%1
792
November1st to 10thNight
14%7%34%32%11%1
884
11th to 20thNight
10%9%38%30%11%3
950
21st to endNight
9%6%33%37%13%2
950
December1st to 10thNight
10%6%32%33%16%3
950
11th to 20thNight
8%7%34%37%12%2
950
21st to endNight
11%5%31%37%13%3
1045
Page generated at 2024-01-09 14:24:23. Version ac07

Copyright 2024 Attilla Danko


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