Prince Albert
Clear Sky Chart
History

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

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
40%
24049
11%
74672
7%
24017
44%
24017
20%
50950

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
32%
946
10%
2979
6%
946
37%
946
15%
2219
January11th to 20thNight
32%
905
12%
2713
8%
905
36%
905
15%
2052
January21st to endNight
28%
990
11%
2880
5%
990
34%
990
13%
2274
February1st to 10thNight
38%
900
13%
2520
8%
900
42%
900
19%
1854
February11th to 20thNight
39%
707
14%
2280
11%
707
44%
707
17%
1607
February21st to endNight
49%
592
19%
1884
14%
592
55%
592
23%
1253
March1st to 10thNight
42%
720
13%
2160
10%
720
44%
720
18%
1571
March11th to 20thNight
42%
720
17%
2044
11%
720
47%
720
21%
1443
March21st to endNight
47%
652
16%
2038
13%
652
51%
652
21%
1382
April1st to 10thNight
47%
540
15%
1800
12%
540
52%
540
25%
1122
April11th to 20thNight
37%
533
14%
1665
10%
533
42%
533
21%
1127
April21st to endNight
39%
540
13%
1440
7%
540
42%
540
23%
1023
May1st to 10thNight
42%
540
12%
1440
6%
540
45%
540
29%
952
May11th to 20thNight
48%
531
8%
1418
6%
531
50%
531
35%
879
May21st to endNight
45%
406
2%
1181
2%
405
46%
405
22%
822
June1st to 10thNight
45%
360
0%
1080
0%
360
45%
360
27%
681
June11th to 20thNight
41%
360
0%
1080
0%
360
41%
360
19%
768
June21st to endNight
53%
360
0%
1080
0%
360
53%
360
28%
690
July1st to 10thNight
60%
350
0%
1050
0%
350
60%
350
31%
627
July11th to 20thNight
53%
348
0%
1137
0%
348
53%
348
28%
689
July21st to endNight
63%
443
6%
1349
5%
419
65%
419
34%
742
August1st to 10thNight
61%
537
10%
1424
5%
534
64%
534
40%
847
August11th to 20thNight
59%
534
14%
1424
9%
534
62%
534
37%
878
August21st to endNight
52%
594
16%
1820
12%
594
56%
594
31%
1092
September1st to 10thNight
49%
540
16%
1800
14%
540
53%
540
28%
1057
September11th to 20thNight
48%
540
17%
1800
15%
540
55%
540
27%
1089
September21st to endNight
47%
617
22%
2033
18%
617
55%
617
31%
1166
October1st to 10thNight
39%
720
17%
2160
11%
720
44%
720
23%
1464
October11th to 20thNight
42%
780
16%
2220
8%
780
48%
780
25%
1475
October21st to endNight
30%
990
14%
2618
5%
990
36%
990
19%
1964
November1st to 10thNight
28%
925
11%
2590
6%
925
32%
925
13%
2071
November11th to 20thNight
29%
950
11%
2736
5%
950
34%
950
14%
2165
November21st to endNight
28%
950
9%
2850
3%
950
35%
950
15%
2158
December1st to 10thNight
34%
950
10%
3025
5%
950
40%
950
15%
2253
December11th to 20thNight
25%
950
9%
3705
3%
949
32%
949
9%
2799
December21st to endNight
37%
1029
8%
5249
7%
1026
41%
1026
13%
2695

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
11%8%47%6%45%5%6%8%35%
74512
Night
9%9%48%7%45%5%6%7%36%
75190
TransparencyDay
46%8%17%22%8%1
74185
Night
46%8%15%22%9%1
75035
SeeingDay
14%8%28%29%16%4
14651
Night
13%5%28%36%15%2
24073

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
9%16%6%9%9%45%5%6%6%24%
1183
11th to 20thDay
8%13%6%13%7%47%45%7%25%
1260
21st to endDay
9%15%5%11%7%46%5%5%8%23%
1475
February1st to 10thDay
8%8%5%10%9%5%7%8%8%8%24%
1449
11th to 20thDay
7%12%6%9%7%46%6%6%8%30%
1575
21st to endDay
5%11%5%12%8%5%6%6%6%8%29%
1372
March1st to 10thDay
9%12%6%9%9%6%8%7%5%7%23%
1800
11th to 20thDay
8%12%5%8%7%46%5%6%8%31%
1915
21st to endDay
9%12%5%9%7%46%6%47%31%
2317
April1st to 10thDay
7%10%47%6%46%5%6%9%37%
2160
11th to 20thDay
12%10%47%7%35%5%6%8%31%
2244
21st to endDay
12%9%47%7%446%7%8%33%
2520
May1st to 10thDay
13%6%25%7%36%5%7%8%38%
2520
11th to 20thDay
9%6%35%6%46%6%6%8%41%
2478
21st to endDay
18%6%35%5%45%5%6%7%35%
3091
June1st to 10thDay
15%7%36%6%46%5%7%8%33%
2880
11th to 20thDay
22%7%46%6%46%5%6%7%26%
2880
21st to endDay
15%6%36%6%36%7%6%8%36%
2880
July1st to 10thDay
9%5%25%5%36%6%7%10%42%
2880
11th to 20thDay
10%5%25%5%45%6%7%9%42%
2782
21st to endDay
8%5%25%5%35%6%6%9%46%
2887
August1st to 10thDay
9%5%35%5%35%6%8%10%43%
2507
11th to 20thDay
9%5%25%5%3446%10%46%
2477
21st to endDay
13%6%26%5%3445%9%43%
2533
September1st to 10thDay
11%6%26%6%35%5%5%9%43%
2160
11th to 20thDay
12%8%36%6%45%5%6%8%37%
2160
21st to endDay
10%5%25%6%345%5%7%47%
1923
October1st to 10thDay
15%9%35%5%25%46%8%39%
1800
11th to 20thDay
11%8%36%5%445%6%7%41%
1722
21st to endDay
13%11%5%9%8%345%5%6%30%
1736
November1st to 10thDay
16%16%6%8%7%4446%6%24%
1488
11th to 20thDay
11%13%5%12%9%5%7%446%25%
1444
21st to endDay
9%14%9%11%8%35%46%6%25%
1330
December1st to 10thDay
5%11%5%10%11%5%8%7%46%27%
1155
11th to 20thDay
9%14%7%12%8%46%6%5%7%22%
1439
21st to endDay
5%7%49%7%5%5%46%5%44%
2090
January1st to 10thNight
7%12%6%11%10%46%5%6%8%26%
2979
11th to 20thNight
7%14%7%10%8%46%5%6%7%26%
2713
21st to endNight
9%13%5%11%9%5%7%6%6%6%23%
2880
February1st to 10thNight
6%9%6%11%9%46%6%7%8%28%
2520
11th to 20thNight
5%10%5%12%7%5%7%5%7%7%31%
2279
21st to endNight
5%7%49%8%45%7%7%7%36%
1884
March1st to 10thNight
10%9%5%9%7%46%7%7%7%29%
2160
11th to 20thNight
9%11%47%6%36%5%6%7%35%
2044
21st to endNight
8%10%47%6%46%6%6%7%36%
2038
April1st to 10thNight
5%10%36%6%36%6%6%9%40%
1800
11th to 20thNight
13%9%5%7%5%35%6%5%8%35%
1665
21st to endNight
14%8%46%6%46%5%6%7%35%
1440
May1st to 10thNight
10%7%37%5%36%5%6%8%40%
1440
11th to 20thNight
9%6%245%25%5%5%9%48%
1418
21st to endNight
18%6%25%6%45%5%6%7%36%
1181
June1st to 10thNight
13%5%245%35%7%6%7%42%
1080
11th to 20thNight
21%7%36%5%245%7%8%32%
1080
21st to endNight
12%7%244245%6%9%43%
1080
July1st to 10thNight
8%324445%6%8%9%46%
1080
11th to 20thNight
13%425%435%5%7%8%45%
1174
21st to endNight
6%324425%5%5%7%56%
1428
August1st to 10thNight
6%3135%35%5%7%8%53%
1432
11th to 20thNight
8%4244345%7%8%50%
1424
21st to endNight
10%6%25%43445%9%48%
1820
September1st to 10thNight
10%5%26%5%345%5%7%48%
1800
11th to 20thNight
14%6%244245%6%7%46%
1800
21st to endNight
8%4345%345%6%10%48%
2033
October1st to 10thNight
14%9%46%6%2445%7%39%
2160
11th to 20thNight
8%9%36%5%45%6%6%6%42%
2220
21st to endNight
12%12%49%7%45%5%5%7%31%
2618
November1st to 10thNight
16%15%6%7%7%35%5%5%7%24%
2590
11th to 20thNight
9%12%7%13%8%46%6%6%7%23%
2736
21st to endNight
8%12%6%9%9%5%6%6%47%28%
2850
December1st to 10thNight
6%10%6%11%8%5%6%7%6%7%27%
3025
11th to 20thNight
9%12%5%12%10%5%6%5%6%7%22%
3753
21st to endNight
47%37%6%446%6%6%47%
5566

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
59%5%13%18%5%
1183
11th to 20thDay
58%8%13%13%6%1
1260
21st to endDay
59%5%12%13%9%1
1475
February1st to 10thDay
51%9%18%14%9%
1449
11th to 20thDay
50%7%14%20%9%
1584
21st to endDay
52%7%14%17%9%
1372
March1st to 10thDay
56%9%13%16%5%
1800
11th to 20thDay
50%8%13%21%7%
1916
21st to endDay
51%8%14%21%7%
2317
April1st to 10thDay
41%8%16%23%11%1
2160
11th to 20thDay
49%7%15%19%7%2
2244
21st to endDay
47%8%15%21%7%1
2520
May1st to 10thDay
42%7%13%26%12%
2520
11th to 20thDay
38%8%13%26%12%2
2482
21st to endDay
47%7%14%20%11%1
3091
June1st to 10thDay
47%8%16%20%8%1
2880
11th to 20thDay
54%9%13%16%6%1
2880
21st to endDay
44%9%17%24%6%
2880
July1st to 10thDay
34%11%21%27%6%
2801
11th to 20thDay
37%10%23%24%5%
2696
21st to endDay
34%10%25%26%4
2726
August1st to 10thDay
32%12%23%28%4
2491
11th to 20thDay
34%10%26%24%6%
2477
21st to endDay
38%8%18%31%5%
2533
September1st to 10thDay
38%8%18%24%10%2
2160
11th to 20thDay
43%9%18%24%6%
2160
21st to endDay
35%7%19%26%11%1
1923
October1st to 10thDay
43%8%17%25%7%
1800
11th to 20thDay
42%7%16%26%7%1
1722
21st to endDay
54%8%16%19%4
1736
November1st to 10thDay
60%7%13%15%4
1488
11th to 20thDay
61%8%14%13%3
1444
21st to endDay
60%5%15%14%5%
1330
December1st to 10thDay
56%8%12%16%7%1
1155
11th to 20thDay
58%8%17%12%4
1440
21st to endDay
41%7%12%17%21%2
2090
January1st to 10thNight
56%7%14%17%6%
2979
11th to 20thNight
57%6%13%16%7%1
2713
21st to endNight
60%7%11%13%8%1
2880
February1st to 10thNight
51%8%15%17%9%
2520
11th to 20thNight
50%7%14%20%9%
2280
21st to endNight
44%7%14%24%11%
1884
March1st to 10thNight
49%10%12%23%6%1
2160
11th to 20thNight
47%8%15%20%9%1
2044
21st to endNight
45%7%13%23%10%1
2038
April1st to 10thNight
39%7%16%23%14%1
1800
11th to 20thNight
46%6%13%18%14%3
1665
21st to endNight
47%7%14%22%10%1
1440
May1st to 10thNight
40%6%12%25%15%2
1440
11th to 20thNight
33%7%13%22%22%3
1418
21st to endNight
47%7%11%21%14%1
1181
June1st to 10thNight
37%9%17%26%9%2
1080
11th to 20thNight
48%9%18%16%9%
1080
21st to endNight
36%10%19%25%9%1
1080
July1st to 10thNight
28%12%22%28%9%1
1050
11th to 20thNight
34%9%21%30%6%
1137
21st to endNight
26%9%25%33%6%
1349
August1st to 10thNight
26%8%24%34%7%
1424
11th to 20thNight
30%9%23%31%8%
1424
21st to endNight
33%8%21%29%9%
1820
September1st to 10thNight
34%7%18%27%11%3
1800
11th to 20thNight
36%7%17%30%9%
1800
21st to endNight
31%8%17%29%15%1
2033
October1st to 10thNight
45%7%14%27%7%
2160
11th to 20thNight
41%7%17%24%9%
2220
21st to endNight
52%8%14%19%8%
2618
November1st to 10thNight
60%8%11%15%5%1
2590
11th to 20thNight
59%8%15%14%3
2736
21st to endNight
55%8%17%16%3
2850
December1st to 10thNight
54%9%14%18%5%
3025
11th to 20thNight
59%8%14%15%5%
3751
21st to endNight
35%7%14%26%16%2
5566

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
14%5%33%28%14%6%
180
11th to 20thDay
12%5%29%36%16%2
160
21st to endDay
13%8%32%32%14%
216
February1st to 10thDay
9%6%31%36%16%2
240
11th to 20thDay
9%5%28%39%18%1
240
21st to endDay
7%333%32%17%8%
198
March1st to 10thDay
10%6%28%39%16%1
240
11th to 20thDay
11%5%37%30%13%4
356
21st to endDay
13%10%33%27%15%2
462
April1st to 10thDay
10%10%34%30%11%5%
420
11th to 20thDay
15%11%30%28%12%4
450
21st to endDay
13%11%34%27%14%2
600
May1st to 10thDay
14%8%27%32%16%4
603
11th to 20thDay
12%10%26%28%19%4
625
21st to endDay
17%9%23%26%20%4
679
June1st to 10thDay
16%10%29%27%14%3
630
11th to 20thDay
23%12%25%22%13%4
630
21st to endDay
16%7%22%29%19%6%
630
July1st to 10thDay
10%6%26%29%22%6%
621
11th to 20thDay
10%9%26%30%19%5%
618
21st to endDay
8%7%24%30%23%8%
684
August1st to 10thDay
12%6%22%31%22%7%
626
11th to 20thDay
10%9%21%32%20%8%
615
21st to endDay
17%7%24%33%15%3
523
September1st to 10thDay
15%13%30%28%12%2
450
11th to 20thDay
17%7%29%32%13%2
450
21st to endDay
12%13%27%30%17%2
293
October1st to 10thDay
17%9%29%28%16%2
270
11th to 20thDay
15%10%34%27%10%4
270
21st to endDay
17%11%31%26%14%1
297
November1st to 10thDay
21%8%29%29%9%3
270
11th to 20thDay
13%11%43%25%8%
270
21st to endDay
16%7%40%25%9%3
270
December1st to 10thDay
10%7%27%32%18%5%
187
11th to 20thDay
14%6%34%36%10%1
180
21st to endDay
9%333%27%19%10%
198
January1st to 10thNight
13%5%30%37%14%1
950
11th to 20thNight
14%6%30%39%11%1
905
21st to endNight
15%7%33%36%8%1
990
February1st to 10thNight
10%430%38%15%2
900
11th to 20thNight
9%5%29%36%18%3
711
21st to endNight
8%422%40%24%3
592
March1st to 10thNight
13%427%36%19%2
720
11th to 20thNight
12%6%31%37%13%1
720
21st to endNight
13%427%36%16%3
652
April1st to 10thNight
9%5%30%38%16%2
540
11th to 20thNight
17%7%31%29%15%1
533
21st to endNight
17%5%27%39%11%1
540
May1st to 10thNight
14%6%30%35%13%1
540
11th to 20thNight
11%8%26%36%17%1
531
21st to endNight
20%6%19%36%17%2
406
June1st to 10thNight
16%428%35%15%1
360
11th to 20thNight
21%6%22%31%19%3
360
21st to endNight
16%322%40%18%1
360
July1st to 10thNight
9%421%43%23%1
350
11th to 20thNight
16%422%35%21%2
348
21st to endNight
6%422%36%30%2
443
August1st to 10thNight
6%422%37%28%4
537
11th to 20thNight
11%321%37%25%4
534
21st to endNight
12%425%37%21%1
594
September1st to 10thNight
13%5%25%37%19%2
540
11th to 20thNight
18%5%21%40%15%1
540
21st to endNight
9%6%32%39%12%
617
October1st to 10thNight
18%5%29%36%10%2
720
11th to 20thNight
14%6%29%36%14%1
780
21st to endNight
19%7%31%31%11%1
990
November1st to 10thNight
22%6%31%31%8%2
925
11th to 20thNight
14%7%33%32%12%2
950
21st to endNight
12%8%36%33%9%1
950
December1st to 10thNight
11%5%30%35%17%3
950
11th to 20thNight
13%7%32%31%14%2
950
21st to endNight
12%426%36%18%4
1045
Page generated at 2024-01-08 10:14:15. Version ac07

Copyright 2024 Attilla Danko


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