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Carp Library / Diefenbunker
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Carp Library / Diefenbunker clear sky chart from 2005-11-06 to 2024-01-16.

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
30%
22582
15%
74781
9%
22540
38%
22540
17%
52350

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
14%
760
9%
2649
3%
757
22%
757
8%
2103
January11th to 20thNight
17%
741
9%
2591
5%
741
23%
741
8%
2021
January21st to endNight
22%
792
15%
2688
8%
792
32%
792
14%
1911
February1st to 10thNight
17%
720
10%
2340
4%
720
25%
720
10%
1781
February11th to 20thNight
17%
702
14%
2275
4%
700
29%
700
13%
1642
February21st to endNight
24%
592
16%
1780
8%
592
35%
592
15%
1299
March1st to 10thNight
21%
720
16%
2147
8%
720
30%
720
15%
1588
March11th to 20thNight
22%
720
17%
1979
7%
720
32%
720
17%
1428
March21st to endNight
28%
792
22%
2070
9%
792
37%
792
21%
1429
April1st to 10thNight
21%
720
16%
1800
5%
720
27%
720
19%
1319
April11th to 20thNight
26%
711
19%
1775
7%
711
32%
711
21%
1266
April21st to endNight
28%
608
17%
1688
7%
608
35%
608
19%
1223
May1st to 10thNight
35%
360
19%
1440
16%
360
44%
360
17%
916
May11th to 20thNight
33%
354
23%
1416
18%
354
50%
354
20%
867
May21st to endNight
38%
389
14%
1551
11%
388
50%
388
25%
892
June1st to 10thNight
40%
360
11%
1440
11%
360
48%
360
19%
915
June11th to 20thNight
43%
360
14%
1440
18%
360
52%
360
22%
828
June21st to endNight
41%
360
12%
1440
15%
360
50%
360
19%
895
July1st to 10thNight
50%
350
15%
1400
20%
350
59%
350
27%
776
July11th to 20thNight
53%
348
17%
1392
24%
348
59%
348
25%
791
July21st to endNight
54%
394
16%
1486
19%
372
59%
372
25%
824
August1st to 10thNight
51%
406
17%
1470
15%
404
58%
404
25%
866
August11th to 20thNight
59%
534
19%
1598
14%
534
63%
534
35%
970
August21st to endNight
48%
789
19%
1977
8%
789
52%
789
33%
1283
September1st to 10thNight
48%
720
18%
1800
9%
720
50%
720
34%
1173
September11th to 20thNight
52%
720
23%
1800
14%
720
55%
720
37%
1144
September21st to endNight
43%
720
22%
2041
16%
720
49%
720
28%
1325
October1st to 10thNight
37%
720
18%
2160
12%
720
45%
720
21%
1460
October11th to 20thNight
27%
720
15%
2160
8%
720
37%
720
17%
1560
October21st to endNight
25%
792
14%
2509
8%
792
34%
792
14%
1846
November1st to 10thNight
29%
740
17%
2410
12%
740
37%
740
18%
1643
November11th to 20thNight
22%
760
17%
2660
10%
760
34%
760
14%
1895
November21st to endNight
20%
760
11%
2660
5%
760
28%
760
10%
1998
December1st to 10thNight
18%
760
9%
2660
5%
760
24%
760
8%
2125
December11th to 20thNight
18%
759
12%
3243
6%
759
28%
759
9%
2426
December21st to endNight
13%
829
6%
4846
2%
817
20%
817
4%
3922

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
17%9%47%6%35%5%5%7%33%
74756
Night
17%10%47%6%35%45%6%32%
75036
TransparencyDay
51%311%22%11%1
74461
Night
53%310%21%11%1
74865
SeeingDay
23%12%30%21%10%3
13356
Night
23%10%28%28%10%1
22591

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
16%16%5%11%9%35%45%5%22%
1517
11th to 20thDay
18%14%5%11%7%46%345%23%
1480
21st to endDay
12%15%6%9%8%5%5%5%5%6%25%
1665
February1st to 10thDay
14%15%5%10%8%45%5%6%5%23%
1620
11th to 20thDay
13%14%5%9%6%35%446%29%
1573
21st to endDay
19%13%48%7%26%5%5%5%25%
1475
March1st to 10thDay
15%11%5%8%8%45%5%45%30%
1807
11th to 20thDay
16%11%5%7%7%46%446%31%
1980
21st to endDay
19%10%35%5%3445%5%37%
2286
April1st to 10thDay
23%9%36%5%34446%33%
2160
11th to 20thDay
22%7%36%5%33445%37%
2134
21st to endDay
22%10%36%6%345%45%32%
2286
May1st to 10thDay
19%7%37%6%35%45%5%35%
2520
11th to 20thDay
15%7%46%6%35%45%6%39%
2478
21st to endDay
16%5%35%6%45%5%6%6%39%
2725
June1st to 10thDay
20%7%46%5%46%5%5%7%30%
2520
11th to 20thDay
14%6%25%5%36%6%6%8%40%
2520
21st to endDay
17%7%35%6%45%6%7%7%32%
2520
July1st to 10thDay
11%5%25%5%36%6%7%9%40%
2520
11th to 20thDay
11%6%35%5%45%5%7%9%40%
2520
21st to endDay
11%5%25%5%36%5%7%10%40%
2744
August1st to 10thDay
10%5%26%5%46%6%6%8%40%
2455
11th to 20thDay
11%5%27%6%46%6%6%8%40%
2287
21st to endDay
13%6%36%5%35%5%6%9%40%
2376
September1st to 10thDay
13%5%35%6%35%5%5%8%42%
2160
11th to 20thDay
12%5%25%5%345%6%9%45%
2160
21st to endDay
15%6%25%5%35%6%6%7%39%
1917
October1st to 10thDay
19%7%46%5%4446%7%35%
1800
11th to 20thDay
22%8%36%6%36%5%5%7%29%
1800
21st to endDay
26%8%47%6%35%446%27%
1846
November1st to 10thDay
15%8%46%6%45%5%6%7%34%
1667
11th to 20thDay
19%11%47%6%46%5%5%6%28%
1520
21st to endDay
20%12%48%8%47%6%5%5%21%
1520
December1st to 10thDay
20%18%5%9%8%45%5%5%6%16%
1520
11th to 20thDay
21%13%5%8%7%35%5%46%24%
1906
21st to endDay
28%15%7%11%6%2422319%
2772
January1st to 10thNight
17%16%6%11%8%45%5%46%18%
2649
11th to 20thNight
17%15%6%10%8%35%44423%
2591
21st to endNight
12%14%6%9%6%35%45%6%30%
2688
February1st to 10thNight
14%14%5%11%9%46%5%5%6%22%
2340
11th to 20thNight
14%12%5%11%8%3445%5%30%
2273
21st to endNight
16%12%48%7%45%46%6%29%
1780
March1st to 10thNight
16%13%5%9%7%45%445%29%
2137
11th to 20thNight
16%11%5%7%7%24345%35%
1979
21st to endNight
17%7%46%6%35%45%5%39%
2070
April1st to 10thNight
20%9%37%6%35%346%34%
1800
11th to 20thNight
19%9%36%6%34446%36%
1775
21st to endNight
20%9%37%6%44446%32%
1688
May1st to 10thNight
21%7%35%5%345%6%7%36%
1440
11th to 20thNight
17%8%35%4345%5%7%40%
1415
21st to endNight
13%6%26%5%335%5%8%45%
1550
June1st to 10thNight
15%6%37%6%35%6%7%8%34%
1440
11th to 20thNight
14%5%26%5%3446%8%43%
1440
21st to endNight
17%8%35%5%35%5%6%8%38%
1440
July1st to 10thNight
10%5%26%5%35%5%5%8%46%
1440
11th to 20thNight
12%5%35%5%35%5%6%9%43%
1440
21st to endNight
9%6%246%46%5%6%9%44%
1574
August1st to 10thNight
8%6%47%6%445%6%9%43%
1480
11th to 20thNight
9%5%35%6%35%5%6%9%46%
1598
21st to endNight
11%5%36%5%35%46%8%45%
1977
September1st to 10thNight
11%5%35%6%35%5%5%6%46%
1800
11th to 20thNight
15%42443435%7%48%
1800
21st to endNight
17%5%26%5%2445%7%43%
2041
October1st to 10thNight
17%7%35%6%35%45%6%37%
2160
11th to 20thNight
22%8%45%6%45%45%7%30%
2160
21st to endNight
23%10%46%6%45%5%46%28%
2509
November1st to 10thNight
19%10%36%5%33446%35%
2410
11th to 20thNight
19%10%47%6%36%5%5%6%29%
2660
21st to endNight
22%12%49%6%45%45%7%23%
2660
December1st to 10thNight
21%16%5%9%7%46%5%5%6%17%
2660
11th to 20thNight
21%14%5%9%6%3443426%
3288
21st to endNight
31%17%410%5%3433418%
4884

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
66%29%16%7%
1518
11th to 20thDay
66%28%14%10%1
1480
21st to endDay
61%311%15%9%1
1665
February1st to 10thDay
62%39%19%5%2
1620
11th to 20thDay
57%312%18%10%1
1582
21st to endDay
60%39%15%11%1
1475
March1st to 10thDay
57%310%18%11%1
1810
11th to 20thDay
55%210%16%13%3
1980
21st to endDay
50%37%20%15%5%
2286
April1st to 10thDay
54%26%20%14%3
2160
11th to 20thDay
51%26%23%16%2
2134
21st to endDay
56%27%15%15%4
2286
May1st to 10thDay
51%27%21%15%4
2520
11th to 20thDay
46%37%23%18%3
2482
21st to endDay
46%412%22%13%3
2725
June1st to 10thDay
53%410%21%12%1
2520
11th to 20thDay
42%412%26%14%3
2520
21st to endDay
49%413%22%11%1
2520
July1st to 10thDay
38%412%30%14%1
2450
11th to 20thDay
39%415%30%12%1
2445
21st to endDay
40%414%30%11%
2591
August1st to 10thDay
40%417%27%11%
2441
11th to 20thDay
41%416%28%10%1
2287
21st to endDay
40%414%29%13%1
2376
September1st to 10thDay
41%314%30%12%
2160
11th to 20thDay
37%413%33%13%1
2160
21st to endDay
44%414%29%9%
1917
October1st to 10thDay
49%312%24%11%1
1800
11th to 20thDay
56%314%18%8%1
1800
21st to endDay
59%312%17%8%1
1846
November1st to 10thDay
49%314%26%7%1
1667
11th to 20thDay
58%413%16%9%1
1520
21st to endDay
65%412%11%7%1
1520
December1st to 10thDay
70%310%12%41
1520
11th to 20thDay
63%313%15%6%
1906
21st to endDay
73%27%15%3
2772
January1st to 10thNight
68%39%14%6%
2649
11th to 20thNight
66%39%13%8%1
2591
21st to endNight
56%38%20%12%1
2688
February1st to 10thNight
63%39%17%7%1
2340
11th to 20thNight
58%211%20%9%1
2275
21st to endNight
57%39%20%11%1
1780
March1st to 10thNight
59%28%18%11%2
2147
11th to 20thNight
53%39%19%13%3
1980
21st to endNight
48%28%21%16%5%
2070
April1st to 10thNight
54%37%19%16%2
1800
11th to 20thNight
50%36%22%17%2
1775
21st to endNight
54%36%16%16%4
1688
May1st to 10thNight
49%36%21%16%5%
1440
11th to 20thNight
45%36%26%18%3
1416
21st to endNight
39%316%21%19%3
1551
June1st to 10thNight
46%413%25%10%2
1440
11th to 20thNight
40%311%26%18%2
1440
21st to endNight
44%5%13%23%14%1
1440
July1st to 10thNight
35%412%28%18%3
1400
11th to 20thNight
38%411%33%13%
1392
21st to endNight
37%416%29%15%
1486
August1st to 10thNight
39%418%25%13%1
1470
11th to 20thNight
35%417%31%12%
1598
21st to endNight
38%415%31%12%
1977
September1st to 10thNight
38%411%31%14%1
1800
11th to 20thNight
36%313%36%10%2
1800
21st to endNight
42%311%33%10%
2041
October1st to 10thNight
48%410%25%13%1
2160
11th to 20thNight
55%311%22%9%
2160
21st to endNight
58%412%17%8%
2509
November1st to 10thNight
51%313%23%9%1
2410
11th to 20thNight
56%311%19%10%1
2660
21st to endNight
61%413%16%6%
2660
December1st to 10thNight
69%39%15%4
2660
11th to 20thNight
63%29%17%7%1
3288
21st to endNight
74%27%13%4
4884

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
22%20%35%18%41
180
11th to 20thDay
31%17%31%18%4
170
21st to endDay
19%18%37%21%4
212
February1st to 10thDay
32%23%32%13%1
240
11th to 20thDay
30%24%38%8%1
240
21st to endDay
33%19%31%14%3
341
March1st to 10thDay
27%16%33%20%4
420
11th to 20thDay
28%17%33%18%31
420
21st to endDay
34%15%26%17%6%1
462
April1st to 10thDay
32%17%29%15%6%1
420
11th to 20thDay
34%13%25%15%11%3
412
21st to endDay
32%15%30%15%7%1
420
May1st to 10thDay
26%12%31%21%7%3
423
11th to 20thDay
20%15%32%21%8%4
447
21st to endDay
19%12%33%21%13%1
485
June1st to 10thDay
26%9%31%22%9%3
450
11th to 20thDay
17%12%31%26%12%3
450
21st to endDay
20%10%30%26%12%3
450
July1st to 10thDay
13%427%36%17%4
445
11th to 20thDay
13%6%31%29%16%5%
444
21st to endDay
15%6%30%29%16%4
488
August1st to 10thDay
14%5%27%30%19%5%
446
11th to 20thDay
14%325%31%19%9%
439
21st to endDay
17%9%27%23%16%9%
495
September1st to 10thDay
16%9%27%22%17%9%
450
11th to 20thDay
14%6%26%25%19%9%
450
21st to endDay
18%9%31%21%16%5%
450
October1st to 10thDay
24%11%25%20%14%5%
450
11th to 20thDay
28%17%27%19%8%2
450
21st to endDay
32%14%25%22%6%
428
November1st to 10thDay
27%14%30%20%9%1
361
11th to 20thDay
31%17%32%13%6%2
180
21st to endDay
29%18%36%12%5%1
180
December1st to 10thDay
33%11%38%16%3
180
11th to 20thDay
31%23%34%9%3
180
21st to endDay
29%21%35%11%41
198
January1st to 10thNight
28%13%34%21%5%
760
11th to 20thNight
29%16%27%22%7%1
741
21st to endNight
19%11%35%28%6%
792
February1st to 10thNight
23%15%35%23%4
720
11th to 20thNight
22%15%38%21%4
703
21st to endNight
26%16%28%26%4
592
March1st to 10thNight
23%13%33%27%3
720
11th to 20thNight
24%15%32%22%6%
720
21st to endNight
24%14%27%26%8%
792
April1st to 10thNight
26%13%30%25%6%
720
11th to 20thNight
26%15%28%22%9%
711
21st to endNight
26%10%28%27%8%
608
May1st to 10thNight
23%7%26%31%11%1
360
11th to 20thNight
22%8%30%30%9%1
354
21st to endNight
15%5%37%29%14%
389
June1st to 10thNight
18%332%36%11%
360
11th to 20thNight
18%6%24%36%15%1
360
21st to endNight
20%426%35%14%1
360
July1st to 10thNight
11%327%42%17%1
350
11th to 20thNight
14%322%45%15%1
348
21st to endNight
10%423%45%16%2
394
August1st to 10thNight
11%320%42%22%
406
11th to 20thNight
12%216%41%26%3
534
21st to endNight
13%5%23%38%19%2
789
September1st to 10thNight
14%428%32%19%3
720
11th to 20thNight
18%5%21%33%20%4
720
21st to endNight
20%7%24%28%20%2
720
October1st to 10thNight
23%9%23%28%15%2
720
11th to 20thNight
28%9%28%27%7%1
720
21st to endNight
28%12%27%27%6%
792
November1st to 10thNight
27%11%25%28%9%1
740
11th to 20thNight
25%14%32%18%9%1
760
21st to endNight
31%13%26%23%7%
760
December1st to 10thNight
30%13%30%22%5%
760
11th to 20thNight
28%15%28%22%5%1
760
21st to endNight
35%12%28%20%4
836
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