Prince Albert
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Prince Albert clear sky chart from 2005-11-05 to 2018-03-21.

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
41%
16437
11%
49253
7%
16409
45%
16409
20%
34919

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
35%
970
11%
3006
8%
970
38%
970
15%
2240
January16th to endNight
29%
1040
12%
3055
7%
1040
34%
1040
14%
2336
February1st to 15thNight
39%
892
12%
2619
8%
892
43%
892
18%
1914
February16th to endNight
47%
684
13%
2192
10%
684
51%
684
19%
1564
March1st to 15thNight
42%
780
14%
2321
11%
780
44%
780
18%
1698
March16th to endNight
43%
698
15%
2085
11%
698
47%
698
19%
1506
April1st to 15thNight
43%
539
12%
1798
10%
539
47%
539
22%
1176
April16th to endNight
41%
540
14%
1482
10%
540
43%
540
22%
1052
May1st to 15thNight
45%
539
10%
1440
6%
539
47%
539
30%
942
May16th to endNight
43%
443
2%
1249
3%
442
44%
442
22%
883
June1st to 15thNight
49%
360
0%
1080
0%
360
49%
360
22%
726
June16th to endNight
47%
360
0%
1080
0%
360
47%
360
21%
755
July1st to 15thNight
59%
340
0%
1023
0%
340
59%
340
31%
607
July16th to endNight
60%
409
3%
1270
3%
385
61%
385
30%
734
August1st to 15thNight
63%
539
10%
1432
5%
536
65%
536
37%
879
August16th to endNight
56%
573
16%
1686
11%
573
60%
573
35%
984
September1st to 15thNight
53%
540
16%
1800
15%
540
56%
540
29%
1063
September16th to endNight
50%
590
20%
1958
18%
590
57%
590
30%
1134
October1st to 15thNight
39%
720
15%
2160
9%
720
44%
720
21%
1507
October16th to endNight
36%
941
15%
2507
7%
941
41%
941
22%
1813
November1st to 15thNight
32%
950
12%
2660
6%
950
36%
950
15%
2082
November16th to endNight
32%
975
9%
2912
4%
975
37%
975
14%
2265
December1st to 15thNight
33%
975
5%
3110
4%
975
36%
975
10%
2496
December16th to endNight
34%
1040
11%
3328
6%
1040
39%
1040
12%
2563

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
12%8%37%6%35%5%5%7%33%
49648
Night
10%9%47%6%35%5%5%7%33%
49392
TransparencyDay
48%7%17%20%5%
49291
Night
49%7%15%20%6%
49253
SeeingDay
16%6%25%29%17%4
6736
Night
15%425%35%16%2
16452

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
9%17%5%10%6%27%45%6%23%
1259
16th to endDay
10%13%49%7%35%45%8%26%
1520
February1st to 15thDay
7%8%6%9%8%5%7%8%7%7%24%
1587
16th to endDay
7%13%5%11%8%45%46%7%23%
1568
March1st to 15thDay
10%12%5%8%7%46%6%5%7%25%
1969
16th to endDay
10%13%5%8%6%36%5%46%28%
2265
April1st to 15thDay
10%10%47%6%35%45%8%34%
2150
16th to endDay
14%9%37%6%245%6%8%31%
2478
May1st to 15thDay
12%6%25%6%26%46%8%38%
2511
16th to endDay
18%435%435%5%6%7%34%
2864
June1st to 15thDay
18%7%36%6%35%5%7%7%26%
2880
16th to endDay
20%6%35%6%35%6%5%7%28%
2880
July1st to 15thDay
11%424435%5%6%9%41%
2874
16th to endDay
9%5%25%5%35%6%6%8%41%
2812
August1st to 15thDay
10%5%244345%7%9%40%
2520
16th to endDay
11%425%42335%10%45%
2513
September1st to 15thDay
10%6%25%5%24449%43%
2160
16th to endDay
12%5%245%3445%7%43%
2001
October1st to 15thDay
16%9%36%425%35%7%34%
1800
16th to endDay
16%10%36%6%3346%6%32%
1703
November1st to 15thDay
17%12%5%7%5%44346%27%
1528
16th to endDay
11%12%7%10%9%36%35%5%23%
1378
December1st to 15thDay
8%14%6%10%11%5%7%6%46%18%
1180
16th to endDay
9%12%7%13%8%5%5%345%23%
1248
January1st to 15thNight
7%14%6%9%7%35%45%7%26%
3006
16th to endNight
9%12%5%9%7%46%5%6%7%25%
3055
February1st to 15thNight
6%9%6%10%7%46%5%7%7%28%
2608
16th to endNight
6%9%5%11%8%45%5%5%7%31%
2192
March1st to 15thNight
11%11%48%5%35%6%6%6%30%
2321
16th to endNight
9%11%47%6%46%5%5%6%32%
2082
April1st to 15thNight
9%10%36%5%25%6%5%7%38%
1798
16th to endNight
18%8%45%425%446%35%
1482
May1st to 15thNight
11%5%25%5%25%45%7%41%
1439
16th to endNight
16%6%25%6%35%5%5%8%35%
1249
June1st to 15thNight
18%6%23425%5%7%7%34%
1080
16th to endNight
17%5%26%5%235%6%9%35%
1080
July1st to 15thNight
9%3144345%7%9%46%
1083
16th to endNight
8%323425%5%5%7%50%
1356
August1st to 15thNight
7%313435%5%6%7%50%
1440
16th to endNight
8%41432345%10%50%
1686
September1st to 15thNight
12%5%25%42335%6%50%
1800
16th to endNight
11%42442445%8%48%
1958
October1st to 15thNight
15%10%36%5%2445%5%36%
2160
16th to endNight
13%9%36%6%345%5%6%34%
2507
November1st to 15thNight
14%13%6%8%6%25%46%7%25%
2660
16th to endNight
9%12%5%8%8%46%5%5%7%25%
2912
December1st to 15thNight
10%12%6%11%9%5%6%5%5%6%20%
3110
16th to endNight
7%11%6%12%9%5%5%6%6%6%21%
3328

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
59%5%12%16%6%
1259
16th to endDay
56%6%14%15%6%
1520
February1st to 15thDay
52%8%19%14%4
1587
16th to endDay
58%6%13%15%6%
1568
March1st to 15thDay
56%6%14%17%4
1969
16th to endDay
55%7%12%20%4
2266
April1st to 15thDay
47%7%15%20%6%1
2150
16th to endDay
49%7%15%19%6%1
2478
May1st to 15thDay
43%6%13%24%10%1
2511
16th to endDay
47%7%13%19%11%
2868
June1st to 15thDay
53%8%14%17%5%
2880
16th to endDay
52%8%15%17%4
2880
July1st to 15thDay
36%9%21%26%5%
2705
16th to endDay
40%9%24%21%3
2635
August1st to 15thDay
36%11%25%23%2
2504
16th to endDay
35%7%22%29%5%
2513
September1st to 15thDay
38%7%18%25%8%1
2160
16th to endDay
39%6%20%23%8%
2001
October1st to 15thDay
48%6%16%22%4
1800
16th to endDay
51%7%19%19%2
1703
November1st to 15thDay
58%6%13%16%4
1528
16th to endDay
62%6%16%12%2
1378
December1st to 15thDay
64%7%13%11%2
1180
16th to endDay
63%5%11%13%5%
1248
January1st to 15thNight
56%5%13%18%5%
3006
16th to endNight
57%7%13%15%6%
3055
February1st to 15thNight
52%7%16%19%5%
2619
16th to endNight
50%6%14%20%7%
2192
March1st to 15thNight
51%8%13%21%4
2321
16th to endNight
51%6%12%20%7%
2085
April1st to 15thNight
43%6%16%20%10%2
1798
16th to endNight
48%5%11%20%11%1
1482
May1st to 15thNight
39%5%12%23%16%2
1440
16th to endNight
48%5%10%18%15%2
1249
June1st to 15thNight
43%8%16%24%6%
1080
16th to endNight
44%10%18%17%7%
1080
July1st to 15thNight
30%9%22%28%8%
1023
16th to endNight
32%7%24%29%5%
1270
August1st to 15thNight
29%8%24%32%5%
1432
16th to endNight
30%6%23%30%8%
1686
September1st to 15thNight
35%5%15%29%10%2
1800
16th to endNight
33%5%17%30%12%
1958
October1st to 15thNight
48%5%14%25%4
2160
16th to endNight
48%6%17%20%5%
2507
November1st to 15thNight
58%7%11%17%4
2660
16th to endNight
57%8%17%13%2
2912
December1st to 15thNight
62%8%13%12%1
3110
16th to endNight
59%7%12%14%5%
3328

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
10%130%35%16%6%
90
16th to endDay
16%433%28%16%
111
February1st to 15thDay
6%231%43%16%
135
16th to endDay
16%20%34%20%7%
120
March1st to 15thDay
16%5%31%27%18%1
154
16th to endDay
19%7%29%26%14%2
311
April1st to 15thDay
14%8%36%28%8%2
269
16th to endDay
16%8%27%28%17%2
417
May1st to 15thDay
15%10%24%31%16%3
468
16th to endDay
16%8%23%23%21%6%
517
June1st to 15thDay
18%10%25%27%13%4
495
16th to endDay
21%6%22%25%18%5%
495
July1st to 15thDay
12%5%22%25%26%7%
475
16th to endDay
10%6%23%32%20%6%
515
August1st to 15thDay
16%315%29%23%12%
493
16th to endDay
13%6%23%34%18%4
409
September1st to 15thDay
16%8%27%30%14%1
315
16th to endDay
16%5%20%34%18%4
210
October1st to 15thDay
22%5%30%25%14%1
135
16th to endDay
25%229%27%11%3
144
November1st to 15thDay
22%5%31%28%11%1
135
16th to endDay
22%9%24%25%14%3
135
December1st to 15thDay
21%25%32%14%6%
92
16th to endDay
11%127%33%16%10%
96
January1st to 15thNight
14%5%26%38%13%1
975
16th to endNight
14%6%34%34%8%1
1040
February1st to 15thNight
10%427%37%17%2
900
16th to endNight
9%320%39%24%2
684
March1st to 15thNight
16%424%36%17%1
780
16th to endNight
15%426%32%18%3
699
April1st to 15thNight
14%5%28%33%15%1
539
16th to endNight
22%323%34%15%1
540
May1st to 15thNight
14%5%28%37%14%
540
16th to endNight
19%7%20%33%16%2
443
June1st to 15thNight
19%320%38%17%1
360
16th to endNight
20%220%36%18%2
360
July1st to 15thNight
10%320%39%25%1
340
16th to endNight
11%220%33%30%1
409
August1st to 15thNight
8%118%31%33%5%
539
16th to endNight
12%322%38%22%1
573
September1st to 15thNight
16%219%36%22%1
540
16th to endNight
12%326%40%15%
590
October1st to 15thNight
21%227%35%11%1
720
16th to endNight
20%5%27%34%12%
941
November1st to 15thNight
20%430%30%11%2
950
16th to endNight
14%6%31%34%10%2
975
December1st to 15thNight
15%325%35%17%2
975
16th to endNight
12%425%33%19%4
1040
Page generated at 2018-03-22 09:34:25. Version ac04

Copyright 2018 A. Danko


Prince Albert Clear Sky Chart |Charts Home