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 2017-09-16.

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
36%
15254
12%
46737
9%
15215
39%
15215
17%
34159

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
13%
898
6%
2526
2%
895
16%
895
7%
2186
January16th to endNight
17%
769
6%
2497
3%
769
21%
769
7%
2131
February1st to 15thNight
16%
701
6%
2287
2%
701
21%
701
8%
1875
February16th to endNight
25%
631
8%
1931
4%
631
30%
631
11%
1538
March1st to 15thNight
26%
720
12%
2034
8%
720
29%
720
15%
1581
March16th to endNight
35%
768
16%
2112
11%
768
39%
768
21%
1518
April1st to 15thNight
35%
650
14%
1820
7%
650
41%
650
21%
1296
April16th to endNight
40%
540
19%
1620
11%
540
46%
540
24%
1069
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%
661
19%
1826
15%
661
59%
661
30%
1179
October1st to 15thNight
42%
660
16%
1941
13%
660
45%
660
21%
1318
October16th to endNight
22%
704
9%
2156
5%
704
27%
704
12%
1674
November1st to 15thNight
32%
700
17%
2285
15%
700
36%
700
16%
1627
November16th to endNight
22%
720
9%
2520
7%
720
25%
720
8%
2034
December1st to 15thNight
13%
720
3%
2520
2%
720
14%
720
6%
2162
December16th to endNight
11%
897
4%
2817
1%
897
15%
897
5%
2482

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%
48006
Night
16%10%5%7%6%34446%30%
46915
Cloud CoverDay
14%9%47%5%3445%7%32%
48016
Night
16%10%5%7%6%34446%30%
46919
TransparencyDay
50%6%13%18%9%1
47703
Night
53%6%11%17%9%1
46737
SeeingDay
17%6%22%27%18%6%
5739
Night
20%7%27%29%13%1
15261

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%10%11%9%33335%13%
1411
16th to endDay
14%17%8%13%11%45%33411%
1724
February1st to 15thDay
16%14%7%10%8%45%435%17%
1575
16th to endDay
14%14%7%12%7%35%5%45%20%
1539
March1st to 15thDay
16%12%6%10%7%24445%25%
1915
16th to endDay
15%9%5%7%5%35%447%30%
2112
April1st to 15thDay
17%11%45%42445%8%32%
2136
16th to endDay
16%8%35%42335%7%39%
2340
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
15%425%425%45%8%41%
1824
October1st to 15thDay
17%6%36%6%35%46%6%32%
1689
16th to endDay
29%13%36%5%24335%23%
1713
November1st to 15thDay
17%12%47%435%45%6%29%
1570
16th to endDay
18%18%7%10%7%35%445%16%
1440
December1st to 15thDay
19%21%9%12%6%3433311%
1440
16th to endDay
20%23%8%13%6%344339%
1404
January1st to 15thNight
22%15%9%11%8%4433413%
2526
16th to endNight
15%17%9%11%9%45%43414%
2497
February1st to 15thNight
16%16%5%11%9%35%44417%
2285
16th to endNight
16%12%6%10%8%45%445%21%
1931
March1st to 15thNight
17%10%6%8%8%34445%26%
2022
16th to endNight
16%8%46%6%34446%34%
2112
April1st to 15thNight
21%8%44424446%34%
1820
16th to endNight
13%8%35%5%24447%38%
1620
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
13%5%245%345%46%44%
1826
October1st to 15thNight
17%7%36%5%3335%6%37%
1941
16th to endNight
27%10%38%7%23445%22%
2156
November1st to 15thNight
16%12%47%5%2435%6%30%
2285
16th to endNight
22%18%6%8%5%24345%19%
2520
December1st to 15thNight
21%19%8%10%6%35%33313%
2520
16th to endNight
21%18%9%12%7%35%33311%
2817

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
19%17%9%12%9%33235%13%
1411
16th to endDay
14%17%8%14%11%45%33411%
1724
February1st to 15thDay
16%15%7%10%8%5%5%5%35%17%
1575
16th to endDay
14%14%6%12%7%35%5%4419%
1539
March1st to 15thDay
16%12%6%9%7%2445%5%24%
1926
16th to endDay
15%9%6%7%5%35%35%7%30%
2111
April1st to 15thDay
17%12%35%42445%8%31%
2136
16th to endDay
16%8%35%424347%39%
2340
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
15%325%43445%8%41%
1824
October1st to 15thDay
17%7%36%6%3446%6%32%
1689
16th to endDay
28%14%36%5%24335%22%
1713
November1st to 15thDay
17%11%47%425%446%30%
1570
16th to endDay
18%18%7%11%6%45%345%15%
1440
December1st to 15thDay
19%21%9%12%6%35%33311%
1440
16th to endDay
20%21%9%13%6%334339%
1404
January1st to 15thNight
22%15%8%11%8%4433313%
2526
16th to endNight
15%17%9%11%9%4443414%
2497
February1st to 15thNight
16%15%6%11%8%36%5%4417%
2278
16th to endNight
16%11%6%9%8%45%5%45%20%
1931
March1st to 15thNight
17%10%6%8%7%34345%26%
2034
16th to endNight
16%8%47%6%34346%34%
2112
April1st to 15thNight
21%9%34424446%33%
1820
16th to endNight
13%8%25%5%25%45%7%39%
1620
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%245%345%5%6%44%
1826
October1st to 15thNight
16%7%36%6%33346%37%
1941
16th to endNight
26%10%38%6%24445%22%
2156
November1st to 15thNight
16%12%47%5%24346%30%
2285
16th to endNight
21%18%6%8%5%23345%18%
2520
December1st to 15thNight
20%19%9%10%6%3433313%
2520
16th to endNight
21%18%9%13%6%3343311%
2817

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
72%6%9%8%2
1412
16th to endDay
75%6%9%6%2
1724
February1st to 15thDay
70%5%9%10%2
1577
16th to endDay
65%7%10%10%4
1539
March1st to 15thDay
61%5%12%12%7%
1926
16th to endDay
52%6%13%18%7%1
2112
April1st to 15thDay
50%6%13%18%10%
2136
16th to endDay
45%414%19%13%2
2340
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
40%6%14%27%10%
1824
October1st to 15thDay
48%7%13%18%11%1
1689
16th to endDay
62%5%13%12%4
1713
November1st to 15thDay
53%6%14%17%8%
1570
16th to endDay
70%7%11%9%1
1440
December1st to 15thDay
75%7%10%6%
1440
16th to endDay
79%6%7%5%1
1404
January1st to 15thNight
73%5%7%9%3
2526
16th to endNight
71%7%9%9%1
2497
February1st to 15thNight
66%7%10%11%3
2287
16th to endNight
63%6%12%12%4
1931
March1st to 15thNight
59%5%10%17%5%1
2034
16th to endNight
50%5%11%21%10%1
2112
April1st to 15thNight
50%411%20%11%1
1820
16th to endNight
44%410%19%17%3
1620
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%6%13%26%14%
1826
October1st to 15thNight
45%7%12%19%14%1
1941
16th to endNight
62%5%13%13%5%
2156
November1st to 15thNight
51%6%12%18%8%1
2285
16th to endNight
67%5%11%12%2
2520
December1st to 15thNight
74%5%11%6%2
2520
16th to endNight
75%6%8%6%2
2817

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
17%24%35%16%5%1
87
16th to endDay
40%10%31%17%
96
February1st to 15thDay
24%16%42%16%
90
16th to endDay
13%16%45%22%2
81
March1st to 15thDay
27%13%27%25%5%
216
16th to endDay
22%6%30%26%12%1
288
April1st to 15thDay
25%9%23%27%12%1
270
16th to endDay
22%7%29%20%13%6%
270
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
15%415%28%26%11%
257
October1st to 15thDay
18%6%22%28%20%3
255
16th to endDay
31%9%30%22%4
225
November1st to 15thDay
18%10%20%31%15%3
88
16th to endDay
23%26%30%15%31
60
December1st to 15thDay
30%28%20%20%1
60
16th to endDay
23%28%35%12%
64
January1st to 15thNight
29%13%35%16%4
900
16th to endNight
23%10%35%25%5%
769
February1st to 15thNight
23%10%37%24%3
704
16th to endNight
21%10%32%28%6%
631
March1st to 15thNight
22%8%32%28%7%
720
16th to endNight
19%5%32%30%11%1
768
April1st to 15thNight
24%9%26%31%8%
650
16th to endNight
17%5%31%32%12%2
540
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
15%218%33%24%6%
661
October1st to 15thNight
19%5%24%30%18%1
660
16th to endNight
31%11%31%21%4
704
November1st to 15thNight
22%10%30%24%11%1
700
16th to endNight
29%14%27%20%7%
720
December1st to 15thNight
29%15%35%15%3
720
16th to endNight
30%13%36%17%3
897
Page generated at 2017-09-17 12:05:41. Version ac04

Copyright 2017 A. Danko


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