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

2017-09-12
.

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%
15572
11%
46652
7%
15544
45%
15544
19%
33124

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
34%
895
10%
2774
7%
895
37%
895
15%
2084
January16th to endNight
29%
960
12%
2820
7%
960
34%
960
15%
2143
February1st to 15thNight
39%
822
11%
2414
8%
822
42%
822
17%
1785
February16th to endNight
45%
632
13%
2025
10%
632
49%
632
18%
1464
March1st to 15thNight
40%
720
13%
2142
10%
720
42%
720
17%
1584
March16th to endNight
43%
674
15%
2019
11%
674
47%
674
19%
1450
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%
530
16%
1766
15%
530
57%
530
29%
1036
September16th to endNight
49%
540
20%
1794
16%
540
56%
540
30%
1034
October1st to 15thNight
38%
660
16%
1980
10%
660
44%
660
21%
1378
October16th to endNight
37%
862
14%
2297
7%
862
42%
862
22%
1658
November1st to 15thNight
32%
875
13%
2450
7%
875
37%
875
16%
1898
November16th to endNight
33%
900
9%
2688
4%
900
37%
900
14%
2098
December1st to 15thNight
33%
900
5%
2871
4%
900
35%
900
9%
2351
December16th to endNight
31%
960
9%
3072
6%
960
36%
960
11%
2423

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%36%6%35%5%5%7%33%
48059
Night
11%9%47%6%35%5%5%7%33%
46791
TransparencyDay
48%7%17%20%5%
47702
Night
49%7%15%20%6%
46652
SeeingDay
16%6%25%28%17%4
6204
Night
15%425%35%16%2
15587

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%18%5%10%7%27%45%6%23%
1161
16th to endDay
10%13%49%7%35%45%8%27%
1403
February1st to 15thDay
8%9%6%9%8%47%8%6%7%22%
1461
16th to endDay
8%14%6%11%8%35%46%6%23%
1449
March1st to 15thDay
10%13%5%8%7%46%6%5%7%24%
1818
16th to endDay
10%13%5%8%6%36%5%46%28%
2204
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%44%
2113
16th to endDay
12%5%245%3445%7%43%
1835
October1st to 15thDay
16%9%46%425%35%7%33%
1650
16th to endDay
16%10%36%6%3346%6%32%
1562
November1st to 15thDay
18%12%5%7%433347%28%
1408
16th to endDay
11%12%8%10%9%46%345%23%
1272
December1st to 15thDay
8%14%6%11%11%5%6%6%46%17%
1089
16th to endDay
9%13%7%13%8%5%5%335%22%
1152
January1st to 15thNight
8%14%6%9%7%35%447%26%
2774
16th to endNight
9%11%5%9%7%46%5%6%7%25%
2820
February1st to 15thNight
6%10%6%10%7%45%5%7%7%27%
2403
16th to endNight
6%10%5%11%8%45%5%5%7%29%
2025
March1st to 15thNight
12%11%48%6%346%6%6%29%
2142
16th to endNight
9%10%47%6%46%5%5%6%32%
2016
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
11%5%25%42335%6%50%
1766
16th to endNight
11%42432445%8%48%
1794
October1st to 15thNight
15%10%36%42445%5%37%
1980
16th to endNight
14%10%45%6%245%5%6%34%
2297
November1st to 15thNight
15%13%5%7%5%25%46%7%26%
2450
16th to endNight
10%12%6%8%7%46%5%47%25%
2688
December1st to 15thNight
10%12%6%12%9%5%6%5%5%6%18%
2871
16th to endNight
8%11%7%13%9%5%5%5%6%6%20%
3072

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
60%5%12%16%4
1161
16th to endDay
54%6%15%16%6%
1403
February1st to 15thDay
55%8%18%13%4
1461
16th to endDay
58%6%12%15%6%
1449
March1st to 15thDay
57%6%15%16%4
1818
16th to endDay
55%6%12%20%4
2205
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%26%8%1
2113
16th to endDay
38%6%19%25%8%
1835
October1st to 15thDay
50%6%15%22%5%
1650
16th to endDay
51%7%18%20%1
1562
November1st to 15thDay
56%6%13%17%4
1408
16th to endDay
62%5%16%12%2
1272
December1st to 15thDay
65%7%13%11%2
1089
16th to endDay
66%5%11%13%2
1152
January1st to 15thNight
57%5%13%18%4
2774
16th to endNight
56%7%13%15%6%
2820
February1st to 15thNight
53%7%15%18%5%
2414
16th to endNight
52%6%12%20%8%
2025
March1st to 15thNight
52%8%13%20%4
2142
16th to endNight
50%6%12%21%7%
2019
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%16%29%10%2
1766
16th to endNight
33%6%17%30%11%
1794
October1st to 15thNight
48%6%14%25%5%
1980
16th to endNight
48%6%18%21%5%
2297
November1st to 15thNight
56%7%11%17%5%
2450
16th to endNight
58%8%16%13%3
2688
December1st to 15thNight
65%8%12%11%1
2871
16th to endNight
62%7%12%13%4
3072

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
330%38%20%8%
60
16th to endDay
12%439%29%13%1
74
February1st to 15thDay
7%224%46%18%
90
16th to endDay
24%124%25%14%8%
81
March1st to 15thDay
18%439%24%12%
108
16th to endDay
18%8%31%27%14%
288
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%9%27%30%15%2
300
16th to endDay
13%7%24%38%13%1
159
October1st to 15thDay
28%428%20%16%1
90
16th to endDay
27%127%23%15%5%
96
November1st to 15thDay
22%5%38%23%8%1
90
16th to endDay
25%6%22%18%21%5%
90
December1st to 15thDay
21%22%29%16%9%
61
16th to endDay
17%125%37%10%7%
64
January1st to 15thNight
15%5%25%38%13%1
900
16th to endNight
14%6%34%35%7%1
960
February1st to 15thNight
11%326%36%18%2
830
16th to endNight
10%320%37%24%2
632
March1st to 15thNight
16%425%35%16%1
720
16th to endNight
14%426%33%17%2
675
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
15%319%37%22%1
530
16th to endNight
12%328%40%14%
540
October1st to 15thNight
21%226%35%11%2
660
16th to endNight
20%5%26%33%12%
862
November1st to 15thNight
21%429%30%11%2
875
16th to endNight
14%6%30%35%11%2
900
December1st to 15thNight
16%323%34%18%3
900
16th to endNight
13%425%32%19%4
960
Page generated at 2017-09-13 05:39:11. Version ac04

Copyright 2017 A. Danko


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