Cluny
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cluny clear sky chart from 2005-11-05 to 2018-10-08.

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%
16612
13%
50950
9%
16585
47%
16585
22%
34488

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
36%
970
9%
2910
6%
970
38%
970
15%
2194
January16th to endNight
36%
921
18%
3001
11%
921
45%
921
20%
2028
February1st to 15thNight
42%
758
12%
2584
12%
756
45%
756
16%
1796
February16th to endNight
43%
684
12%
2173
12%
684
45%
684
19%
1535
March1st to 15thNight
39%
780
15%
2265
9%
780
44%
780
20%
1608
March16th to endNight
35%
832
9%
2288
3%
832
40%
832
17%
1741
April1st to 15thNight
37%
652
10%
1835
5%
652
40%
652
18%
1368
April16th to endNight
43%
579
14%
1737
10%
579
48%
579
23%
1169
May1st to 15thNight
46%
500
12%
1544
11%
500
49%
500
24%
999
May16th to endNight
42%
407
6%
1421
5%
406
44%
406
17%
965
June1st to 15thNight
45%
390
1%
1365
1%
390
45%
390
17%
952
June16th to endNight
52%
390
1%
1365
0%
390
52%
390
23%
854
July1st to 15thNight
60%
370
3%
1295
1%
370
61%
370
27%
767
July16th to endNight
62%
408
11%
1358
11%
386
67%
386
35%
714
August1st to 15thNight
64%
462
12%
1606
15%
460
66%
460
29%
926
August16th to endNight
60%
621
21%
1863
16%
621
64%
621
39%
1027
September1st to 15thNight
56%
679
18%
1953
13%
679
59%
679
32%
1221
September16th to endNight
51%
776
20%
2145
13%
776
55%
776
34%
1331
October1st to 15thNight
43%
752
17%
2207
9%
752
49%
752
23%
1495
October16th to endNight
44%
768
19%
2490
11%
768
53%
768
24%
1585
November1st to 15thNight
36%
923
17%
2633
9%
923
43%
923
22%
1806
November16th to endNight
34%
975
13%
2867
8%
975
40%
975
21%
2018
December1st to 15thNight
35%
975
11%
2925
7%
975
39%
975
17%
2123
December16th to endNight
35%
1040
14%
3120
8%
1040
41%
1040
17%
2266

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%36%6%35%5%5%8%36%
52222
Night
7%8%47%6%35%5%6%8%35%
51097
Cloud CoverDay
9%8%36%6%35%5%6%8%36%
52223
Night
7%8%47%6%35%5%6%8%35%
51100
TransparencyDay
43%7%16%21%8%1
51873
Night
44%7%15%20%9%1
50950
SeeingDay
13%6%24%30%19%5%
7416
Night
11%5%29%34%16%2
16624

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 15thDay
8%10%5%8%9%45%6%6%8%26%
1358
16th to endDay
7%9%5%9%6%45%5%7%8%29%
1586
February1st to 15thDay
9%12%48%7%46%5%5%7%29%
1609
16th to endDay
5%13%6%10%8%5%5%6%5%8%24%
1584
March1st to 15thDay
7%11%5%10%9%36%45%7%28%
2025
16th to endDay
10%14%5%9%7%345%6%7%25%
2287
April1st to 15thDay
11%11%5%9%7%446%5%6%26%
2440
16th to endDay
13%9%36%7%35%5%5%7%32%
2498
May1st to 15thDay
11%7%36%5%35%5%5%7%38%
2734
16th to endDay
17%7%36%5%35%5%5%8%31%
3042
June1st to 15thDay
14%7%35%5%36%6%7%8%31%
2925
16th to endDay
11%5%25%435%5%6%8%37%
2925
July1st to 15thDay
7%424435%5%6%10%45%
2925
16th to endDay
5%213325%5%6%9%53%
3076
August1st to 15thDay
8%5%243345%6%9%44%
2599
16th to endDay
7%213435%45%9%51%
2691
September1st to 15thDay
12%6%25%333335%49%
2336
16th to endDay
12%6%2442335%9%43%
2145
October1st to 15thDay
12%8%37%6%34347%37%
1922
16th to endDay
8%7%36%5%46%5%5%6%39%
1731
November1st to 15thDay
8%12%5%8%7%45%46%7%30%
1543
16th to endDay
6%12%5%7%6%35%46%7%34%
1420
December1st to 15thDay
6%13%6%11%9%35%45%6%24%
1365
16th to endDay
410%6%9%7%47%6%6%9%26%
1456
January1st to 15thNight
5%11%5%9%9%5%7%6%6%8%23%
2910
16th to endNight
5%11%48%7%35%5%6%8%33%
3001
February1st to 15thNight
7%9%49%8%45%5%5%7%31%
2573
16th to endNight
5%9%6%10%7%35%5%7%7%30%
2173
March1st to 15thNight
5%10%5%8%7%45%5%6%9%30%
2265
16th to endNight
9%13%5%9%6%45%5%6%7%25%
2285
April1st to 15thNight
9%11%5%8%8%36%5%6%7%28%
1835
16th to endNight
10%8%36%6%36%5%6%8%34%
1737
May1st to 15thNight
10%9%36%5%245%5%7%39%
1543
16th to endNight
17%6%35%435%46%9%32%
1421
June1st to 15thNight
14%7%36%6%36%6%8%6%30%
1365
16th to endNight
7%5%25%7%5%5%6%7%8%39%
1365
July1st to 15thNight
6%4245%45%5%6%10%43%
1365
16th to endNight
43134245%5%11%52%
1442
August1st to 15thNight
4325%5%35%6%5%9%46%
1614
16th to endNight
7%31442346%9%52%
1863
September1st to 15thNight
12%5%15%424446%48%
1953
16th to endNight
10%42442445%9%47%
2145
October1st to 15thNight
11%8%35%6%35%45%7%37%
2207
16th to endNight
8%7%26%5%25%5%6%9%38%
2490
November1st to 15thNight
6%10%36%6%45%5%6%8%35%
2633
16th to endNight
6%11%47%7%45%5%6%8%32%
2867
December1st to 15thNight
5%10%5%12%8%45%5%5%8%28%
2925
16th to endNight
5%11%5%10%9%45%5%5%8%27%
3120

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%10%49%9%46%5%6%8%26%
1358
16th to endDay
7%9%410%7%36%5%7%9%28%
1586
February1st to 15thDay
9%12%48%7%45%5%6%8%28%
1609
16th to endDay
412%7%10%7%5%5%7%6%7%24%
1584
March1st to 15thDay
6%11%6%10%9%46%45%6%28%
2025
16th to endDay
10%14%5%8%7%35%5%6%8%24%
2288
April1st to 15thDay
10%11%6%8%7%35%5%5%7%27%
2440
16th to endDay
13%9%46%6%35%45%7%32%
2498
May1st to 15thDay
11%8%36%5%35%5%5%8%37%
2734
16th to endDay
17%6%26%5%345%6%8%30%
3042
June1st to 15thDay
14%8%35%5%35%6%6%8%31%
2925
16th to endDay
11%6%35%5%35%5%7%9%37%
2925
July1st to 15thDay
7%324435%6%6%10%45%
2925
16th to endDay
5%213325%5%6%9%54%
3076
August1st to 15thDay
7%5%244345%6%9%45%
2599
16th to endDay
6%31442447%8%52%
2691
September1st to 15thDay
11%5%35%434435%49%
2336
16th to endDay
11%7%25%42345%9%43%
2145
October1st to 15thDay
12%7%38%6%34346%38%
1922
16th to endDay
7%7%37%5%45%5%6%8%38%
1731
November1st to 15thDay
8%11%5%7%7%45%5%5%7%30%
1543
16th to endDay
6%12%5%6%6%35%46%7%34%
1420
December1st to 15thDay
7%12%6%12%9%3445%8%24%
1365
16th to endDay
411%6%9%7%38%6%7%8%26%
1456
January1st to 15thNight
5%11%5%8%10%5%7%6%7%9%22%
2910
16th to endNight
5%11%5%8%6%35%46%8%33%
3001
February1st to 15thNight
7%9%49%8%446%5%7%31%
2573
16th to endNight
5%9%5%11%7%26%5%6%8%30%
2173
March1st to 15thNight
5%10%5%8%6%45%6%7%9%30%
2265
16th to endNight
8%13%5%9%6%36%5%6%7%25%
2288
April1st to 15thNight
9%11%49%6%47%46%8%28%
1835
16th to endNight
10%8%26%6%35%6%6%9%33%
1737
May1st to 15thNight
9%9%35%6%245%5%7%39%
1543
16th to endNight
16%7%45%5%25%5%5%8%33%
1421
June1st to 15thNight
14%7%35%6%46%6%7%7%30%
1365
16th to endNight
7%5%25%7%36%6%6%8%39%
1365
July1st to 15thNight
7%315%5%35%6%6%10%43%
1365
16th to endNight
423415%5%6%11%52%
1442
August1st to 15thNight
4325%6%345%6%10%47%
1614
16th to endNight
6%41432346%8%52%
1863
September1st to 15thNight
11%6%13424446%48%
1953
16th to endNight
10%41443445%9%47%
2145
October1st to 15thNight
10%8%36%5%35%5%5%7%37%
2207
16th to endNight
8%7%26%435%6%6%10%38%
2490
November1st to 15thNight
6%9%46%6%36%5%6%8%36%
2633
16th to endNight
6%10%47%7%45%5%6%8%32%
2867
December1st to 15thNight
5%10%5%12%8%45%46%7%28%
2925
16th to endNight
5%11%5%10%9%45%5%6%8%27%
3120

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
52%8%14%18%41
1358
16th to endDay
47%8%14%18%7%2
1586
February1st to 15thDay
53%7%15%15%7%
1609
16th to endDay
52%9%14%16%6%
1584
March1st to 15thDay
53%7%18%14%5%
2025
16th to endDay
55%7%15%15%5%
2288
April1st to 15thDay
54%7%13%15%7%
2440
16th to endDay
49%6%14%19%8%1
2498
May1st to 15thDay
43%7%14%23%11%
2734
16th to endDay
48%8%15%19%7%
3047
June1st to 15thDay
47%9%16%18%7%1
2925
16th to endDay
40%9%18%23%7%1
2925
July1st to 15thDay
31%9%20%28%9%
2766
16th to endDay
24%9%21%29%13%1
2897
August1st to 15thDay
33%9%21%27%8%1
2582
16th to endDay
26%6%20%30%13%1
2691
September1st to 15thDay
37%5%13%25%14%4
2336
16th to endDay
37%6%13%27%10%3
2145
October1st to 15thDay
45%5%15%24%8%
1922
16th to endDay
41%7%16%24%8%
1731
November1st to 15thDay
51%7%14%18%6%
1543
16th to endDay
46%7%16%20%7%1
1420
December1st to 15thDay
57%7%12%15%5%
1365
16th to endDay
51%7%15%16%7%
1456
January1st to 15thNight
54%8%15%15%5%1
2910
16th to endNight
45%6%15%17%11%2
3001
February1st to 15thNight
50%6%13%19%9%
2584
16th to endNight
49%7%13%18%10%
2173
March1st to 15thNight
47%8%17%19%6%
2265
16th to endNight
54%7%14%16%6%
2288
April1st to 15thNight
52%7%14%16%8%
1835
16th to endNight
43%7%14%23%9%2
1737
May1st to 15thNight
41%7%13%24%12%1
1544
16th to endNight
46%9%15%18%8%1
1421
June1st to 15thNight
48%9%14%18%8%1
1365
16th to endNight
38%9%20%23%7%
1365
July1st to 15thNight
33%9%18%27%9%1
1295
16th to endNight
24%9%19%30%13%2
1358
August1st to 15thNight
30%10%21%26%10%1
1606
16th to endNight
27%5%16%30%16%4
1863
September1st to 15thNight
35%6%12%23%16%5%
1953
16th to endNight
33%6%16%25%14%3
2145
October1st to 15thNight
44%6%15%19%11%1
2207
16th to endNight
38%8%17%25%8%
2490
November1st to 15thNight
44%7%15%20%10%1
2633
16th to endNight
46%8%18%16%8%1
2867
December1st to 15thNight
52%7%15%19%5%
2925
16th to endNight
52%6%15%18%6%
3120

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
11%315%30%22%17%
90
16th to endDay
9%5%25%28%23%8%
96
February1st to 15thDay
19%6%22%33%13%5%
112
16th to endDay
13%421%36%17%4
165
March1st to 15thDay
13%7%33%31%7%6%
330
16th to endDay
13%8%37%24%13%3
352
April1st to 15thDay
13%11%31%27%14%1
329
16th to endDay
19%7%23%27%16%4
318
May1st to 15thDay
14%6%24%28%21%5%
473
16th to endDay
19%419%28%22%5%
597
June1st to 15thDay
15%6%28%28%18%2
570
16th to endDay
11%426%32%18%4
570
July1st to 15thDay
8%420%34%24%7%
550
16th to endDay
6%423%33%22%8%
585
August1st to 15thDay
8%316%34%26%10%
359
16th to endDay
8%6%16%32%25%10%
396
September1st to 15thDay
17%7%20%29%18%5%
375
16th to endDay
18%9%24%27%15%5%
375
October1st to 15thDay
19%6%25%25%16%5%
206
16th to endDay
9%9%30%28%18%3
144
November1st to 15thDay
17%9%33%22%15%2
135
16th to endDay
12%5%33%33%7%7%
103
December1st to 15thDay
12%7%37%22%14%5%
90
16th to endDay
13%428%33%18%2
96
January1st to 15thNight
10%7%30%33%14%2
975
16th to endNight
10%7%33%33%12%1
921
February1st to 15thNight
9%8%25%34%17%4
764
16th to endNight
9%427%37%18%3
684
March1st to 15thNight
8%434%33%15%3
780
16th to endNight
14%6%30%33%14%
832
April1st to 15thNight
14%7%29%34%12%1
652
16th to endNight
15%6%27%35%14%1
579
May1st to 15thNight
12%6%27%35%16%1
501
16th to endNight
20%5%24%28%20%
407
June1st to 15thNight
19%424%36%13%1
390
16th to endNight
8%325%39%21%1
390
July1st to 15thNight
8%221%41%24%1
370
16th to endNight
7%123%41%23%2
408
August1st to 15thNight
6%320%39%28%2
462
16th to endNight
8%420%40%23%1
621
September1st to 15thNight
13%320%37%22%2
679
16th to endNight
12%426%34%18%3
776
October1st to 15thNight
16%426%33%15%3
752
16th to endNight
11%6%31%37%12%1
768
November1st to 15thNight
11%9%35%30%10%2
923
16th to endNight
11%7%35%32%10%2
975
December1st to 15thNight
11%6%31%31%17%1
975
16th to endNight
10%5%33%34%13%3
1040
Page generated at 2018-10-09 08:39:16. Version ac04

Copyright 2018 A. Danko


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