Pigeon Lake Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pigeon Lake Observatory clear sky chart from 2005-11-06 to 2024-01-14.

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
34%
24750
17%
74656
9%
24694
42%
24694
22%
50138

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
18%
950
14%
2648
3%
946
27%
946
18%
1896
January11th to 20thNight
20%
920
12%
2575
4%
920
28%
920
14%
1974
January21st to endNight
20%
990
13%
2772
3%
990
28%
990
16%
2047
February1st to 10thNight
19%
900
14%
2372
2%
900
28%
900
17%
1720
February11th to 20thNight
22%
705
19%
2103
6%
704
34%
704
18%
1431
February21st to endNight
18%
592
18%
1776
3%
592
31%
592
18%
1218
March1st to 10thNight
28%
720
16%
2160
7%
720
36%
720
20%
1462
March11th to 20thNight
29%
717
20%
2126
9%
717
40%
717
24%
1373
March21st to endNight
36%
594
19%
1980
14%
594
44%
594
19%
1358
April1st to 10thNight
25%
540
15%
1800
7%
540
36%
540
18%
1230
April11th to 20thNight
33%
533
19%
1775
15%
533
41%
533
20%
1189
April21st to endNight
35%
540
17%
1648
9%
540
43%
540
23%
1109
May1st to 10thNight
35%
540
15%
1601
9%
540
40%
540
22%
1108
May11th to 20thNight
38%
531
20%
1416
11%
531
45%
531
24%
990
May21st to endNight
50%
583
15%
1552
9%
582
53%
582
30%
1012
June1st to 10thNight
51%
540
16%
1440
9%
540
55%
540
34%
908
June11th to 20thNight
47%
540
17%
1440
9%
540
51%
540
33%
912
June21st to endNight
57%
540
16%
1440
9%
540
61%
540
36%
893
July1st to 10thNight
68%
525
17%
1400
10%
525
71%
525
43%
823
July11th to 20thNight
60%
522
19%
1392
11%
522
64%
522
39%
823
July21st to endNight
61%
591
22%
1487
14%
558
65%
558
41%
887
August1st to 10thNight
65%
537
22%
1423
17%
534
68%
534
39%
862
August11th to 20thNight
64%
534
22%
1672
18%
534
70%
534
36%
945
August21st to endNight
60%
594
21%
1980
22%
594
64%
594
33%
1119
September1st to 10thNight
55%
540
22%
1800
20%
540
61%
540
32%
1020
September11th to 20thNight
56%
635
29%
1895
23%
635
63%
635
36%
1092
September21st to endNight
44%
720
22%
1980
14%
720
49%
720
30%
1264
October1st to 10thNight
43%
720
22%
2034
14%
720
49%
720
30%
1275
October11th to 20thNight
31%
720
17%
2214
9%
720
41%
720
22%
1477
October21st to endNight
31%
792
15%
2574
9%
792
39%
792
19%
1734
November1st to 10thNight
30%
740
25%
2406
14%
740
45%
740
25%
1452
November11th to 20thNight
21%
760
17%
2470
7%
760
34%
760
15%
1682
November21st to endNight
23%
907
18%
2617
7%
907
33%
907
20%
1778
December1st to 10thNight
18%
950
13%
2660
2%
950
27%
950
15%
1941
December11th to 20thNight
17%
950
13%
3207
2%
948
26%
948
13%
2361
December21st to endNight
13%
1038
8%
4821
2%
1026
23%
1026
7%
3773

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
13%8%36%5%35%5%6%8%38%
74809
Night
14%8%36%5%3445%7%39%
74975
TransparencyDay
44%7%13%23%12%1
74510
Night
45%6%12%23%13%2
74795
SeeingDay
16%11%31%26%12%4
14762
Night
17%10%31%29%12%1
24761

By Month

Percentage Cloud Cover SE (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
12%12%5%6%5%35%5%6%8%34%
1517
11th to 20thDay
15%14%5%11%7%345%46%25%
1464
21st to endDay
12%14%7%10%7%35%5%5%6%27%
1584
February1st to 10thDay
11%12%6%9%5%345%5%7%33%
1584
11th to 20thDay
13%11%46%6%25%5%46%38%
1741
21st to endDay
13%12%5%7%6%45%45%7%32%
1480
March1st to 10thDay
14%11%46%5%45%447%36%
1800
11th to 20thDay
12%11%6%6%5%3446%7%37%
1849
21st to endDay
17%11%47%7%345%5%6%30%
2376
April1st to 10thDay
14%13%5%7%5%36%5%5%6%30%
2160
11th to 20thDay
19%9%36%5%45%5%5%6%34%
2134
21st to endDay
18%8%47%5%345%5%6%33%
2312
May1st to 10thDay
16%8%26%6%35%5%7%7%34%
2357
11th to 20thDay
15%6%35%5%35%5%5%7%40%
2479
21st to endDay
11%6%35%6%45%5%6%8%42%
2725
June1st to 10thDay
11%6%25%5%25%46%9%45%
2520
11th to 20thDay
12%6%245%345%6%9%43%
2520
21st to endDay
10%5%35%5%35%5%6%9%45%
2520
July1st to 10thDay
6%3245%36%5%8%11%47%
2520
11th to 20thDay
7%5%245%35%5%7%8%48%
2520
21st to endDay
7%425%5%46%5%6%10%48%
2743
August1st to 10thDay
7%426%5%35%6%6%10%44%
2507
11th to 20thDay
9%425%6%346%6%10%44%
2225
21st to endDay
12%6%26%6%25%46%7%45%
2376
September1st to 10thDay
11%5%36%6%35%46%8%42%
2160
11th to 20thDay
12%425%5%35%46%8%46%
2045
21st to endDay
11%6%37%5%45%5%6%8%40%
1980
October1st to 10thDay
15%6%35%5%35%446%44%
1922
11th to 20thDay
23%8%36%7%45%45%7%28%
1746
21st to endDay
16%9%38%6%45%45%6%33%
1782
November1st to 10thDay
13%7%35%435%5%5%8%42%
1672
11th to 20thDay
11%10%5%8%7%36%6%5%7%32%
1710
21st to endDay
17%10%37%5%35%45%6%36%
1558
December1st to 10thDay
13%12%48%6%5%6%46%8%30%
1520
11th to 20thDay
13%13%47%5%36%5%6%8%29%
1918
21st to endDay
18%19%7%10%7%34445%19%
2783
January1st to 10thNight
12%12%6%8%7%34445%35%
2648
11th to 20thNight
15%13%6%8%7%36%446%29%
2575
21st to endNight
13%12%5%9%6%46%5%5%6%29%
2772
February1st to 10thNight
12%14%48%6%45%445%35%
2372
11th to 20thNight
11%9%38%7%445%5%6%38%
2103
21st to endNight
16%14%46%424346%37%
1776
March1st to 10thNight
13%9%36%6%3446%7%39%
2160
11th to 20thNight
12%7%35%5%35%5%5%7%42%
2126
21st to endNight
18%8%36%5%36%45%6%36%
1980
April1st to 10thNight
16%10%45%5%35%45%7%35%
1800
11th to 20thNight
20%8%36%42445%6%38%
1775
21st to endNight
17%8%46%6%2445%7%37%
1648
May1st to 10thNight
16%6%36%7%45%45%9%34%
1601
11th to 20thNight
17%6%36%6%35%5%5%7%38%
1416
21st to endNight
13%4344345%6%10%43%
1551
June1st to 10thNight
10%5%25%435%5%6%7%47%
1440
11th to 20thNight
12%5%25%43445%9%46%
1440
21st to endNight
8%5%25%425%5%7%9%49%
1440
July1st to 10thNight
8%3244345%5%9%54%
1440
11th to 20thNight
6%425%435%5%6%9%52%
1440
21st to endNight
5%325%6%2446%8%54%
1575
August1st to 10thNight
7%424435%5%6%10%50%
1432
11th to 20thNight
8%42443446%8%53%
1672
21st to endNight
11%4244345%5%7%52%
1980
September1st to 10thNight
9%425%5%3445%8%52%
1800
11th to 20thNight
12%41343335%6%55%
1895
21st to endNight
12%7%35%5%3445%7%45%
1980
October1st to 10thNight
13%5%36%434445%49%
2034
11th to 20thNight
16%8%26%5%35%5%6%7%38%
2214
21st to endNight
16%9%36%5%3446%8%36%
2574
November1st to 10thNight
12%6%245%25%447%48%
2406
11th to 20thNight
15%8%37%7%45%6%5%7%34%
2470
21st to endNight
16%9%35%44445%5%40%
2617
December1st to 10thNight
14%10%47%7%35%5%5%7%32%
2660
11th to 20thNight
14%11%5%8%6%45%5%5%6%31%
3279
21st to endNight
22%17%5%8%6%34345%22%
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
48%6%14%21%10%1
1518
11th to 20thDay
61%6%10%15%8%
1464
21st to endDay
58%6%11%17%8%
1584
February1st to 10thDay
51%412%22%10%1
1584
11th to 20thDay
48%5%11%21%13%2
1751
21st to endDay
52%5%10%19%11%2
1480
March1st to 10thDay
49%6%13%21%10%2
1800
11th to 20thDay
47%5%13%19%13%3
1849
21st to endDay
53%6%13%19%8%1
2376
April1st to 10thDay
52%7%13%17%11%
2160
11th to 20thDay
51%6%9%21%12%2
2134
21st to endDay
51%6%12%19%11%2
2312
May1st to 10thDay
46%7%13%23%10%1
2357
11th to 20thDay
43%8%11%24%12%2
2483
21st to endDay
40%7%12%24%14%2
2725
June1st to 10thDay
36%6%12%28%15%2
2520
11th to 20thDay
38%7%13%25%16%1
2520
21st to endDay
34%8%15%26%15%2
2520
July1st to 10thDay
29%8%13%32%15%3
2451
11th to 20thDay
31%8%14%26%17%3
2445
21st to endDay
29%9%15%27%17%4
2591
August1st to 10thDay
32%10%16%29%11%2
2492
11th to 20thDay
34%8%15%28%12%2
2225
21st to endDay
37%7%13%25%17%1
2376
September1st to 10thDay
39%8%11%26%14%1
2160
11th to 20thDay
35%7%14%32%12%1
2045
21st to endDay
41%7%13%30%10%
1980
October1st to 10thDay
41%5%11%28%13%1
1922
11th to 20thDay
54%6%11%19%9%1
1746
21st to endDay
52%6%13%18%11%
1782
November1st to 10thDay
40%7%12%24%15%2
1672
11th to 20thDay
50%6%14%21%8%1
1710
21st to endDay
49%5%14%22%7%1
1558
December1st to 10thDay
51%6%16%21%6%
1520
11th to 20thDay
51%6%16%17%7%3
1915
21st to endDay
68%49%13%5%
2783
January1st to 10thNight
52%312%18%14%1
2648
11th to 20thNight
58%6%11%17%7%1
2575
21st to endNight
55%5%12%18%10%1
2772
February1st to 10thNight
52%49%22%11%2
2372
11th to 20thNight
47%5%10%22%13%2
2104
21st to endNight
50%412%19%13%2
1776
March1st to 10thNight
46%6%14%22%11%2
2160
11th to 20thNight
40%6%12%23%16%2
2126
21st to endNight
50%5%9%24%11%2
1980
April1st to 10thNight
48%6%9%18%17%2
1800
11th to 20thNight
47%5%8%21%16%3
1775
21st to endNight
45%5%12%21%15%2
1648
May1st to 10thNight
47%6%13%21%11%1
1601
11th to 20thNight
45%7%9%23%13%2
1417
21st to endNight
37%8%13%25%15%2
1552
June1st to 10thNight
34%6%12%29%17%1
1440
11th to 20thNight
36%6%11%26%19%2
1440
21st to endNight
31%8%16%25%16%3
1440
July1st to 10thNight
26%7%13%31%19%3
1400
11th to 20thNight
28%7%13%29%19%4
1392
21st to endNight
27%8%14%29%18%4
1487
August1st to 10thNight
28%8%15%30%15%3
1423
11th to 20thNight
29%7%16%31%17%1
1672
21st to endNight
31%6%12%28%20%2
1980
September1st to 10thNight
31%7%13%25%23%2
1800
11th to 20thNight
30%6%10%36%16%1
1895
21st to endNight
38%5%11%30%15%1
1980
October1st to 10thNight
38%5%10%30%17%2
2034
11th to 20thNight
45%5%14%21%13%1
2214
21st to endNight
47%6%14%21%12%
2574
November1st to 10thNight
37%5%12%26%18%2
2406
11th to 20thNight
49%6%13%19%12%1
2470
21st to endNight
46%5%16%24%8%1
2617
December1st to 10thNight
52%7%13%21%7%1
2660
11th to 20thNight
53%6%12%17%10%1
3281
21st to endNight
65%5%9%15%6%
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
19%16%32%27%6%1
270
11th to 20thDay
20%16%35%23%42
249
21st to endDay
18%12%35%27%6%1
264
February1st to 10thDay
15%23%43%16%3
240
11th to 20thDay
18%28%35%15%5%
240
21st to endDay
25%22%39%12%2
198
March1st to 10thDay
21%17%47%14%2
240
11th to 20thDay
26%12%32%20%8%2
271
21st to endDay
26%13%32%22%6%1
462
April1st to 10thDay
24%13%34%22%8%
420
11th to 20thDay
24%19%28%17%9%3
412
21st to endDay
22%14%29%21%11%2
420
May1st to 10thDay
21%11%37%20%8%2
440
11th to 20thDay
18%12%34%23%10%3
625
21st to endDay
14%9%30%27%15%6%
679
June1st to 10thDay
11%9%33%33%11%3
630
11th to 20thDay
13%8%30%32%13%4
630
21st to endDay
12%7%30%34%13%4
630
July1st to 10thDay
7%424%36%21%8%
621
11th to 20thDay
10%7%28%33%16%7%
618
21st to endDay
6%432%33%17%8%
684
August1st to 10thDay
8%225%40%16%8%
626
11th to 20thDay
11%320%31%25%10%
442
21st to endDay
14%7%20%29%22%7%
495
September1st to 10thDay
15%9%22%29%18%7%
450
11th to 20thDay
12%323%35%19%8%
450
21st to endDay
16%12%25%23%18%5%
450
October1st to 10thDay
20%9%28%26%13%3
392
11th to 20thDay
23%18%30%21%8%
270
21st to endDay
21%17%40%15%6%1
297
November1st to 10thDay
17%14%36%22%9%2
270
11th to 20thDay
16%21%37%19%7%
270
21st to endDay
21%16%37%20%5%
270
December1st to 10thDay
21%19%38%17%4
270
11th to 20thDay
23%20%36%13%6%1
270
21st to endDay
28%19%36%13%5%
297
January1st to 10thNight
19%15%39%23%5%
950
11th to 20thNight
20%15%34%24%6%1
920
21st to endNight
19%11%37%26%7%
990
February1st to 10thNight
20%16%36%24%41
900
11th to 20thNight
18%16%36%23%6%
708
21st to endNight
23%15%37%20%31
592
March1st to 10thNight
18%13%33%25%10%1
720
11th to 20thNight
16%11%39%26%6%1
717
21st to endNight
20%8%28%32%11%1
594
April1st to 10thNight
20%9%40%24%7%
540
11th to 20thNight
24%8%30%26%10%1
533
21st to endNight
20%7%30%29%12%1
540
May1st to 10thNight
19%6%32%33%9%1
540
11th to 20thNight
20%7%29%32%11%1
531
21st to endNight
14%5%22%39%18%2
584
June1st to 10thNight
12%5%25%41%16%1
540
11th to 20thNight
14%425%35%19%2
540
21st to endNight
9%423%43%21%1
540
July1st to 10thNight
9%216%42%29%2
525
11th to 20thNight
6%322%38%28%2
522
21st to endNight
5%223%45%24%2
591
August1st to 10thNight
9%115%43%28%3
537
11th to 20thNight
9%217%37%29%6%
534
21st to endNight
11%318%38%25%4
594
September1st to 10thNight
10%324%32%25%6%
540
11th to 20thNight
13%421%33%23%6%
635
21st to endNight
15%9%24%28%20%4
720
October1st to 10thNight
16%7%29%27%20%2
720
11th to 20thNight
21%11%31%26%10%
720
21st to endNight
22%11%31%25%10%1
792
November1st to 10thNight
15%11%38%26%9%1
740
11th to 20thNight
22%14%35%22%6%
760
21st to endNight
22%14%35%21%7%
907
December1st to 10thNight
21%15%38%21%5%1
950
11th to 20thNight
22%14%36%20%7%1
950
21st to endNight
26%14%36%20%3
1045
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