Port Franks
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Port Franks clear sky chart from 2005-11-05 to 2018-04-23.

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
35%
16136
12%
49438
9%
16097
39%
16097
17%
36203

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
14%
973
6%
2737
3%
970
17%
970
8%
2344
January16th to endNight
17%
833
6%
2705
3%
833
21%
833
7%
2294
February1st to 15thNight
16%
761
6%
2482
2%
761
21%
761
8%
2036
February16th to endNight
24%
683
9%
2090
4%
683
29%
683
11%
1661
March1st to 15thNight
26%
780
12%
2204
8%
780
30%
780
15%
1700
March16th to endNight
36%
832
17%
2288
11%
832
40%
832
22%
1636
April1st to 15thNight
34%
704
14%
1972
7%
704
39%
704
20%
1419
April16th to endNight
40%
558
20%
1672
12%
558
46%
558
25%
1099
May1st to 15thNight
47%
540
15%
1620
11%
540
51%
540
24%
1085
May16th to endNight
52%
456
16%
1579
16%
456
57%
456
26%
940
June1st to 15thNight
54%
360
14%
1325
16%
360
59%
360
25%
806
June16th to endNight
62%
360
16%
1260
18%
360
66%
360
29%
730
July1st to 15thNight
67%
415
18%
1265
21%
415
69%
415
37%
713
July16th to endNight
69%
564
15%
1563
14%
531
70%
531
32%
943
August1st to 15thNight
65%
539
16%
1609
14%
536
65%
536
29%
999
August16th to endNight
61%
573
22%
1719
16%
573
65%
573
33%
1026
September1st to 15thNight
56%
708
18%
1905
13%
708
59%
708
29%
1247
September16th to endNight
57%
717
21%
1980
16%
717
59%
717
30%
1272
October1st to 15thNight
42%
720
15%
2118
13%
720
45%
720
21%
1446
October16th to endNight
23%
768
10%
2352
6%
768
29%
768
12%
1811
November1st to 15thNight
31%
760
15%
2481
14%
760
35%
760
15%
1796
November16th to endNight
22%
780
9%
2730
6%
780
26%
780
9%
2188
December1st to 15thNight
13%
780
3%
2730
1%
780
15%
780
6%
2333
December16th to endNight
11%
972
4%
3052
1%
972
15%
972
5%
2679

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
14%9%47%5%3445%7%32%
50063
Night
16%10%5%7%6%34446%30%
49616
Cloud CoverDay
14%9%47%6%3445%7%32%
50073
Night
16%11%5%7%6%34446%30%
49620
TransparencyDay
50%6%13%18%9%1
49760
Night
53%6%11%17%9%1
49438
SeeingDay
18%6%23%26%17%6%
6425
Night
20%8%27%28%13%1
16143

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 15thDay
19%16%9%11%10%44325%13%
1529
16th to endDay
15%16%8%13%11%45%33412%
1868
February1st to 15thDay
16%15%7%10%9%45%43417%
1710
16th to endDay
15%14%6%11%7%35%445%20%
1666
March1st to 15thDay
15%13%6%10%6%24445%25%
2075
16th to endDay
15%9%5%7%5%35%447%31%
2288
April1st to 15thDay
18%11%45%42445%8%31%
2315
16th to endDay
16%8%25%42335%7%40%
2402
May1st to 15thDay
17%5%36%5%33449%37%
2331
16th to endDay
12%5%25%425%5%5%7%43%
2536
June1st to 15thDay
11%4245%25%46%9%41%
2633
16th to endDay
10%425%4245%6%9%42%
2700
July1st to 15thDay
8%4244245%6%9%47%
2616
16th to endDay
8%424435%5%7%10%43%
2495
August1st to 15thDay
9%5%25%5%35%5%6%9%40%
2340
16th to endDay
11%5%25%5%245%6%8%43%
2483
September1st to 15thDay
13%5%25%5%35%5%6%8%38%
2040
16th to endDay
14%425%435%45%8%41%
1980
October1st to 15thDay
17%7%37%6%3446%6%32%
1842
16th to endDay
27%13%36%5%24336%23%
1869
November1st to 15thDay
18%12%48%425%35%6%28%
1704
16th to endDay
18%18%6%10%7%35%445%16%
1560
December1st to 15thDay
18%21%8%12%6%3433312%
1560
16th to endDay
20%22%9%13%7%344338%
1521
January1st to 15thNight
22%14%8%10%8%4433413%
2737
16th to endNight
15%16%9%11%9%45%5%3415%
2705
February1st to 15thNight
16%15%6%11%9%35%44417%
2480
16th to endNight
17%12%6%9%8%35%445%21%
2090
March1st to 15thNight
16%11%6%7%8%3445%5%27%
2192
16th to endNight
15%8%47%6%34345%35%
2288
April1st to 15thNight
22%8%44424446%32%
1972
16th to endNight
14%8%35%5%24347%39%
1672
May1st to 15thNight
16%6%26%5%3445%9%35%
1620
16th to endNight
11%5%24435%45%7%46%
1577
June1st to 15thNight
11%435%5%35%5%5%8%41%
1325
16th to endNight
9%4245%345%7%7%46%
1260
July1st to 15thNight
6%324434448%53%
1341
16th to endNight
8%3234345%6%8%48%
1670
August1st to 15thNight
8%5%15%5%25%6%6%8%44%
1620
16th to endNight
10%5%24423336%50%
1719
September1st to 15thNight
13%6%145%3445%6%44%
1905
16th to endNight
12%5%25%5%345%46%44%
1980
October1st to 15thNight
17%7%26%5%33346%37%
2118
16th to endNight
26%9%38%6%23445%23%
2352
November1st to 15thNight
17%12%48%5%2435%6%28%
2481
16th to endNight
21%18%5%8%5%24345%19%
2730
December1st to 15thNight
20%19%8%10%6%35%33313%
2730
16th to endNight
21%19%8%13%7%35%33311%
3052

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 15thDay
18%17%8%12%11%3323412%
1529
16th to endDay
14%16%8%14%11%45%33412%
1868
February1st to 15thDay
16%15%7%10%9%44435%17%
1710
16th to endDay
15%14%6%12%7%35%5%4420%
1666
March1st to 15thDay
16%13%6%9%7%24445%24%
2086
16th to endDay
15%9%5%7%5%35%35%6%31%
2287
April1st to 15thDay
18%12%45%42445%8%30%
2315
16th to endDay
16%8%35%423347%39%
2402
May1st to 15thDay
16%6%35%5%24449%37%
2331
16th to endDay
12%5%344345%5%7%42%
2536
June1st to 15thDay
11%4245%25%5%5%9%42%
2633
16th to endDay
10%425%435%5%5%9%42%
2700
July1st to 15thDay
8%4244245%6%9%47%
2616
16th to endDay
8%424435%5%6%10%43%
2495
August1st to 15thDay
9%425%6%35%5%6%10%40%
2340
16th to endDay
11%5%25%42446%8%42%
2483
September1st to 15thDay
13%7%245%25%5%6%7%39%
2040
16th to endDay
14%426%43445%8%41%
1980
October1st to 15thDay
17%7%36%6%3446%6%32%
1842
16th to endDay
26%14%36%5%24346%23%
1869
November1st to 15thDay
18%12%47%5%24446%28%
1704
16th to endDay
18%18%7%10%6%35%345%16%
1560
December1st to 15thDay
18%21%9%13%6%35%33312%
1560
16th to endDay
20%21%9%13%7%344338%
1521
January1st to 15thNight
21%14%8%11%8%45%33413%
2737
16th to endNight
14%16%9%11%9%44435%14%
2705
February1st to 15thNight
16%15%6%11%8%36%5%4417%
2473
16th to endNight
17%12%6%9%8%45%5%45%21%
2090
March1st to 15thNight
16%11%6%8%7%34345%27%
2204
16th to endNight
15%8%48%6%34346%35%
2288
April1st to 15thNight
21%9%35%424446%32%
1972
16th to endNight
14%8%25%5%25%347%39%
1672
May1st to 15thNight
16%6%26%5%3445%8%35%
1619
16th to endNight
11%5%24435%45%7%46%
1577
June1st to 15thNight
10%5%35%5%25%46%8%41%
1325
16th to endNight
9%424425%5%6%7%46%
1260
July1st to 15thNight
6%324434448%53%
1341
16th to endNight
7%424435%5%6%8%48%
1670
August1st to 15thNight
8%5%15%5%35%6%6%8%44%
1620
16th to endNight
10%5%24423336%51%
1719
September1st to 15thNight
13%6%145%24446%44%
1905
16th to endNight
12%5%25%5%245%46%44%
1980
October1st to 15thNight
17%7%36%6%33345%37%
2118
16th to endNight
25%10%38%6%24445%23%
2352
November1st to 15thNight
17%13%38%5%24346%28%
2481
16th to endNight
21%17%6%8%5%24345%19%
2730
December1st to 15thNight
20%19%9%10%7%3443313%
2730
16th to endNight
20%18%9%13%7%3443311%
3052

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
73%6%9%8%2
1530
16th to endDay
73%6%10%6%2
1868
February1st to 15thDay
71%5%8%11%3
1712
16th to endDay
64%7%10%10%5%1
1666
March1st to 15thDay
61%5%11%12%7%
2086
16th to endDay
52%6%12%19%8%1
2288
April1st to 15thDay
51%6%13%18%9%
2315
16th to endDay
45%414%19%13%2
2402
May1st to 15thDay
45%5%12%21%12%1
2331
16th to endDay
40%6%12%23%13%2
2540
June1st to 15thDay
37%8%14%26%12%1
2633
16th to endDay
37%8%13%23%15%
2700
July1st to 15thDay
31%6%13%28%17%2
2464
16th to endDay
34%8%17%23%13%2
2339
August1st to 15thDay
37%8%17%23%12%1
2327
16th to endDay
37%7%15%25%11%1
2483
September1st to 15thDay
42%7%15%22%11%
2040
16th to endDay
39%6%14%28%10%
1980
October1st to 15thDay
48%7%12%18%11%1
1842
16th to endDay
61%5%13%13%5%
1869
November1st to 15thDay
54%5%14%17%7%
1704
16th to endDay
69%7%11%9%1
1560
December1st to 15thDay
73%6%10%7%1
1560
16th to endDay
80%5%7%5%1
1521
January1st to 15thNight
72%5%8%10%3
2737
16th to endNight
70%7%10%9%1
2705
February1st to 15thNight
67%7%9%11%3
2482
16th to endNight
63%5%11%13%5%
2090
March1st to 15thNight
59%5%9%17%7%
2204
16th to endNight
49%5%10%21%10%1
2288
April1st to 15thNight
52%411%19%11%
1972
16th to endNight
44%49%18%18%4
1672
May1st to 15thNight
45%5%12%21%12%3
1620
16th to endNight
36%6%12%24%15%3
1579
June1st to 15thNight
37%8%13%25%15%
1325
16th to endNight
33%7%14%24%18%1
1260
July1st to 15thNight
28%6%9%30%21%3
1265
16th to endNight
32%7%16%23%17%2
1563
August1st to 15thNight
35%8%13%27%12%2
1609
16th to endNight
33%6%12%29%16%2
1719
September1st to 15thNight
38%7%14%24%13%1
1905
16th to endNight
38%5%13%27%14%
1980
October1st to 15thNight
45%7%12%19%14%
2118
16th to endNight
61%413%13%6%
2352
November1st to 15thNight
53%6%12%17%8%1
2481
16th to endNight
66%5%12%12%2
2730
December1st to 15thNight
73%5%11%6%2
2730
16th to endNight
75%6%9%6%2
3052

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
20%20%35%16%6%
130
16th to endDay
35%9%37%18%
144
February1st to 15thDay
27%14%44%13%
135
16th to endDay
19%16%45%17%1
120
March1st to 15thDay
28%12%28%22%7%
271
16th to endDay
21%6%29%29%11%1
352
April1st to 15thDay
26%10%25%25%10%1
330
16th to endDay
22%7%28%21%13%6%
289
May1st to 15thDay
21%427%26%15%4
288
16th to endDay
16%222%29%21%7%
331
June1st to 15thDay
13%322%34%20%5%
428
16th to endDay
14%321%36%18%5%
495
July1st to 15thDay
11%220%32%23%9%
475
16th to endDay
8%115%34%30%9%
355
August1st to 15thDay
13%11%30%27%16%
313
16th to endDay
14%415%21%27%17%
332
September1st to 15thDay
12%418%20%27%16%
315
16th to endDay
14%315%24%26%15%
314
October1st to 15thDay
20%6%22%27%18%4
315
16th to endDay
29%9%31%23%6%
285
November1st to 15thDay
25%9%24%22%15%3
132
16th to endDay
26%18%35%15%21
90
December1st to 15thDay
26%30%18%23%1
90
16th to endDay
25%26%32%16%
96
January1st to 15thNight
28%12%35%17%4
975
16th to endNight
23%10%36%24%5%
833
February1st to 15thNight
23%10%38%23%3
764
16th to endNight
22%10%33%27%5%
683
March1st to 15thNight
22%7%32%28%7%
780
16th to endNight
19%5%31%31%10%1
832
April1st to 15thNight
25%10%25%30%7%
704
16th to endNight
17%5%30%32%11%1
558
May1st to 15thNight
17%422%39%15%1
540
16th to endNight
13%324%39%17%2
458
June1st to 15thNight
11%222%45%17%
360
16th to endNight
10%217%44%23%1
360
July1st to 15thNight
8%15%44%26%4
415
16th to endNight
9%112%45%28%2
564
August1st to 15thNight
10%12%38%34%3
539
16th to endNight
12%215%32%32%4
573
September1st to 15thNight
15%416%31%24%7%
708
16th to endNight
14%217%31%25%7%
717
October1st to 15thNight
19%5%23%29%18%1
720
16th to endNight
30%11%30%21%5%
768
November1st to 15thNight
24%10%28%24%11%
760
16th to endNight
28%14%28%20%7%
780
December1st to 15thNight
29%16%34%15%3
780
16th to endNight
29%13%36%16%3
972
Page generated at 2018-04-24 10:03:05. Version ac04

Copyright 2018 A. Danko


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