Darwin
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Darwin clear sky chart from 2005-11-05 to 2017-10-31.

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
38%
16302
16%
47091
9%
16255
45%
16255
25%
31218

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
31%
900
13%
2550
7%
895
36%
895
19%
1821
January16th to endNight
26%
960
13%
2508
4%
960
32%
960
18%
1869
February1st to 15thNight
33%
879
13%
2288
4%
875
39%
875
23%
1620
February16th to endNight
33%
786
15%
2048
4%
786
40%
786
24%
1432
March1st to 15thNight
35%
542
14%
1982
10%
542
41%
542
20%
1288
March16th to endNight
34%
576
15%
2112
13%
576
41%
576
16%
1431
April1st to 15thNight
33%
539
18%
1812
14%
539
43%
539
23%
1177
April16th to endNight
30%
540
17%
1626
12%
540
39%
540
18%
1162
May1st to 15thNight
32%
540
14%
1533
7%
540
38%
540
23%
1063
May16th to endNight
42%
563
15%
1498
5%
561
47%
561
31%
955
June1st to 15thNight
48%
540
13%
1383
4%
540
51%
540
38%
867
June16th to endNight
56%
540
17%
1260
7%
540
59%
540
47%
786
July1st to 15thNight
60%
510
17%
1221
7%
510
62%
510
48%
718
July16th to endNight
66%
564
20%
1474
12%
531
67%
531
47%
799
August1st to 15thNight
66%
539
21%
1610
18%
536
70%
536
38%
915
August16th to endNight
60%
573
22%
1760
19%
573
67%
573
39%
974
September1st to 15thNight
58%
540
23%
1801
22%
540
66%
540
37%
949
September16th to endNight
42%
555
23%
1998
15%
555
54%
555
30%
1118
October1st to 15thNight
37%
720
23%
2160
13%
720
44%
720
31%
1315
October16th to endNight
34%
768
18%
2304
9%
768
41%
768
21%
1542
November1st to 15thNight
35%
868
20%
2425
10%
868
43%
868
26%
1599
November16th to endNight
29%
900
16%
2520
9%
900
35%
900
21%
1768
December1st to 15thNight
26%
900
11%
2520
4%
900
32%
900
17%
1904
December16th to endNight
23%
960
12%
2698
3%
960
32%
960
13%
2146

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
13%7%36%5%3445%7%37%
48643
Night
12%7%35%5%3445%6%42%
47257
Cloud CoverDay
13%7%36%5%3445%7%37%
48654
Night
12%7%35%5%3445%6%42%
47261
Cloud CoverDay
13%7%36%5%3445%7%37%
48652
Night
12%7%35%5%3445%6%41%
47261
TransparencyDay
44%7%14%23%9%
48328
Night
42%6%14%24%11%1
47091
SeeingDay
16%7%29%28%15%3
6272
Night
15%7%31%31%11%1
16303

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
9%10%6%9%7%47%5%5%8%26%
1376
16th to endDay
7%14%5%8%7%47%6%5%7%24%
1714
February1st to 15thDay
7%11%5%9%6%35%46%8%29%
1575
16th to endDay
9%9%5%9%9%5%6%46%6%28%
1434
March1st to 15thDay
14%10%5%7%6%24447%32%
1969
16th to endDay
16%9%38%5%35%45%7%31%
2112
April1st to 15thDay
17%7%36%5%2345%5%38%
2136
16th to endDay
24%11%35%5%33345%29%
2333
May1st to 15thDay
20%7%36%5%35%346%33%
2418
16th to endDay
15%5%35%6%345%6%8%36%
2617
June1st to 15thDay
14%6%34435%5%6%8%36%
2574
16th to endDay
9%3245%245%5%10%44%
2700
July1st to 15thDay
6%3234245%6%9%52%
2664
16th to endDay
5%3144345%7%10%50%
2590
August1st to 15thDay
9%5%25%5%35%5%7%8%41%
2340
16th to endDay
12%41442435%8%48%
2441
September1st to 15thDay
9%425%42445%7%49%
2157
16th to endDay
15%6%2432345%7%44%
1950
October1st to 15thDay
16%7%24433336%43%
1800
16th to endDay
18%9%35%423346%37%
1919
November1st to 15thDay
12%8%5%6%5%23347%39%
1432
16th to endDay
14%9%35%6%36%36%8%31%
1440
December1st to 15thDay
13%12%5%10%8%45%5%45%25%
1440
16th to endDay
17%17%7%9%6%23335%23%
1512
January1st to 15thNight
8%9%48%6%46%46%7%32%
2550
16th to endNight
10%12%5%8%6%345%5%7%29%
2508
February1st to 15thNight
8%11%46%5%45%446%37%
2285
16th to endNight
8%8%37%6%45%46%7%37%
2048
March1st to 15thNight
12%9%36%434346%40%
1970
16th to endNight
15%8%46%6%34346%36%
2112
April1st to 15thNight
15%9%26%32445%5%41%
1812
16th to endNight
23%10%3442334434%
1626
May1st to 15thNight
18%6%245%2445%5%41%
1533
16th to endNight
12%425%42446%8%44%
1496
June1st to 15thNight
12%31342336%8%48%
1383
16th to endNight
8%2143135%6%6%56%
1260
July1st to 15thNight
32234235%5%7%58%
1293
16th to endNight
5%21232345%9%58%
1575
August1st to 15thNight
6%32433435%7%54%
1620
16th to endNight
8%323313446%57%
1760
September1st to 15thNight
8%21431345%7%56%
1801
16th to endNight
11%5%14413346%52%
1998
October1st to 15thNight
14%6%14323336%50%
2160
16th to endNight
19%8%34323345%40%
2304
November1st to 15thNight
12%6%36%5%23446%44%
2425
16th to endNight
13%9%46%6%33445%38%
2520
December1st to 15thNight
11%10%5%8%7%45%346%31%
2520
16th to endNight
17%14%5%7%7%35%45%6%23%
2698

Percentage Cloud Cover SW (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%10%6%9%7%37%5%48%26%
1376
16th to endDay
7%14%5%8%7%47%6%6%7%24%
1714
February1st to 15thDay
7%11%5%9%7%36%46%8%29%
1575
16th to endDay
9%9%5%9%8%46%46%6%28%
1434
March1st to 15thDay
14%11%5%7%5%24447%32%
1980
16th to endDay
16%8%38%6%25%45%7%31%
2112
April1st to 15thDay
17%7%36%5%2345%6%37%
2136
16th to endDay
24%11%36%5%33345%29%
2333
May1st to 15thDay
20%7%36%5%35%346%33%
2418
16th to endDay
14%6%25%5%35%5%6%8%36%
2617
June1st to 15thDay
14%7%34435%5%6%8%36%
2574
16th to endDay
9%4245%345%6%10%43%
2700
July1st to 15thDay
6%3134245%6%9%52%
2664
16th to endDay
5%3144345%7%10%49%
2590
August1st to 15thDay
9%5%25%5%345%7%8%41%
2340
16th to endDay
12%5%1442435%8%47%
2441
September1st to 15thDay
9%425%43445%7%49%
2157
16th to endDay
15%6%2432445%7%43%
1950
October1st to 15thDay
17%7%24433346%43%
1800
16th to endDay
18%9%35%42335%6%37%
1919
November1st to 15thDay
12%8%5%6%5%2335%7%39%
1432
16th to endDay
14%9%36%6%36%46%8%31%
1440
December1st to 15thDay
13%12%5%9%8%36%45%5%25%
1440
16th to endDay
17%17%8%9%5%2434423%
1512
January1st to 15thNight
8%8%5%8%7%46%46%7%31%
2550
16th to endNight
10%12%5%8%6%345%6%7%29%
2508
February1st to 15thNight
8%11%5%6%5%45%446%37%
2278
16th to endNight
8%7%37%6%45%47%6%37%
2048
March1st to 15thNight
12%9%46%424446%40%
1982
16th to endNight
15%9%47%6%24346%36%
2112
April1st to 15thNight
15%8%26%32445%5%41%
1812
16th to endNight
23%9%34414345%34%
1626
May1st to 15thNight
18%6%245%235%45%40%
1532
16th to endNight
12%425%42446%8%44%
1496
June1st to 15thNight
12%41342336%9%48%
1383
16th to endNight
8%2133235%6%6%56%
1260
July1st to 15thNight
32234235%5%8%58%
1293
16th to endNight
5%21232345%8%58%
1575
August1st to 15thNight
6%32433445%7%54%
1620
16th to endNight
8%323313436%57%
1760
September1st to 15thNight
8%21332345%7%56%
1801
16th to endNight
11%5%24413346%52%
1998
October1st to 15thNight
14%6%24323336%50%
2160
16th to endNight
19%8%25%323345%40%
2304
November1st to 15thNight
12%6%36%5%22446%43%
2425
16th to endNight
12%9%46%6%33346%38%
2520
December1st to 15thNight
11%10%5%8%7%45%346%31%
2520
16th to endNight
17%14%5%7%7%3445%6%23%
2698

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
9%11%6%9%7%46%5%5%8%26%
1376
16th to endDay
7%14%5%9%7%47%6%5%7%24%
1714
February1st to 15thDay
7%11%5%9%7%35%5%6%8%29%
1575
16th to endDay
9%9%5%9%9%46%46%6%28%
1434
March1st to 15thDay
13%11%5%7%6%24347%32%
1980
16th to endDay
16%8%38%6%25%45%7%31%
2110
April1st to 15thDay
17%7%36%5%1345%5%38%
2136
16th to endDay
24%11%36%5%33345%29%
2333
May1st to 15thDay
19%7%46%5%35%446%32%
2418
16th to endDay
14%6%35%6%35%5%6%8%36%
2617
June1st to 15thDay
14%7%34435%5%6%8%36%
2574
16th to endDay
9%4245%345%6%10%43%
2700
July1st to 15thDay
6%3133245%6%9%52%
2664
16th to endDay
5%3144345%7%10%49%
2590
August1st to 15thDay
9%5%25%5%35%5%7%8%41%
2340
16th to endDay
12%5%2442435%8%47%
2441
September1st to 15thDay
9%425%43445%7%49%
2157
16th to endDay
15%6%25%32445%7%43%
1950
October1st to 15thDay
16%7%25%433336%43%
1800
16th to endDay
18%9%35%42335%6%37%
1919
November1st to 15thDay
12%8%5%6%5%2335%7%39%
1432
16th to endDay
14%9%36%6%35%46%8%31%
1440
December1st to 15thDay
13%12%5%10%7%45%5%5%5%25%
1440
16th to endDay
17%16%8%9%6%23345%23%
1512
January1st to 15thNight
8%8%5%8%7%46%46%7%31%
2550
16th to endNight
10%12%5%8%6%345%6%7%29%
2508
February1st to 15thNight
8%12%5%5%5%44446%37%
2278
16th to endNight
8%7%37%6%45%46%7%37%
2048
March1st to 15thNight
12%9%46%5%24446%40%
1982
16th to endNight
15%8%46%6%34346%36%
2112
April1st to 15thNight
15%8%36%32445%5%41%
1812
16th to endNight
23%10%3442434434%
1626
May1st to 15thNight
18%6%25%5%24445%40%
1532
16th to endNight
12%42442446%8%44%
1496
June1st to 15thNight
12%41342435%9%48%
1383
16th to endNight
8%21331446%7%55%
1260
July1st to 15thNight
32144235%5%8%57%
1293
16th to endNight
5%21332345%8%58%
1575
August1st to 15thNight
6%32443445%7%54%
1620
16th to endNight
8%324323446%57%
1760
September1st to 15thNight
7%31332345%7%56%
1801
16th to endNight
11%5%1432335%6%52%
1998
October1st to 15thNight
14%6%24323336%50%
2160
16th to endNight
18%9%25%323345%40%
2304
November1st to 15thNight
12%6%36%5%3345%6%43%
2425
16th to endNight
13%9%46%6%3335%6%38%
2520
December1st to 15thNight
11%10%5%8%7%45%446%31%
2520
16th to endNight
17%14%5%7%7%3445%6%23%
2698

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
55%6%13%17%7%
1377
16th to endDay
56%7%16%16%3
1714
February1st to 15thDay
51%7%15%19%5%
1576
16th to endDay
54%6%13%18%6%
1434
March1st to 15thDay
51%6%14%19%6%
1980
16th to endDay
52%6%14%23%2
2112
April1st to 15thDay
46%5%12%22%10%1
2136
16th to endDay
56%5%11%16%8%1
2333
May1st to 15thDay
52%6%12%20%7%
2418
16th to endDay
44%7%13%22%10%
2621
June1st to 15thDay
42%9%15%23%8%
2574
16th to endDay
33%8%17%27%10%1
2700
July1st to 15thDay
27%7%17%28%16%2
2508
16th to endDay
27%9%18%26%15%1
2428
August1st to 15thDay
37%10%15%25%9%2
2326
16th to endDay
33%6%17%28%13%1
2441
September1st to 15thDay
33%6%15%32%11%
2157
16th to endDay
40%5%13%31%8%
1950
October1st to 15thDay
42%412%26%12%1
1800
16th to endDay
47%414%22%9%
1919
November1st to 15thDay
44%5%13%21%14%1
1432
16th to endDay
49%7%17%16%7%1
1440
December1st to 15thDay
60%7%12%13%5%
1440
16th to endDay
64%410%14%5%
1512
January1st to 15thNight
49%6%13%21%8%
2550
16th to endNight
52%6%15%19%6%
2508
February1st to 15thNight
47%5%16%20%10%
2288
16th to endNight
44%6%15%21%11%
2048
March1st to 15thNight
45%5%16%23%8%
1982
16th to endNight
49%5%13%25%4
2112
April1st to 15thNight
44%5%10%26%12%1
1812
16th to endNight
52%48%17%14%2
1626
May1st to 15thNight
44%7%12%21%11%1
1533
16th to endNight
36%6%16%23%14%2
1498
June1st to 15thNight
32%5%16%30%12%2
1383
16th to endNight
25%7%15%29%18%3
1260
July1st to 15thNight
24%5%17%32%17%2
1221
16th to endNight
21%6%17%32%17%4
1474
August1st to 15thNight
28%6%14%30%16%3
1610
16th to endNight
26%6%16%29%17%3
1760
September1st to 15thNight
26%5%15%32%19%
1801
16th to endNight
32%5%13%32%14%1
1998
October1st to 15thNight
36%411%29%16%2
2160
16th to endNight
45%5%13%22%12%1
2304
November1st to 15thNight
40%5%12%23%15%1
2425
16th to endNight
46%6%17%18%9%1
2520
December1st to 15thNight
54%7%12%19%6%
2520
16th to endNight
61%6%11%14%5%
2698

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%7%34%25%10%2
90
16th to endDay
23%10%33%27%5%
96
February1st to 15thDay
13%18%40%23%4
90
16th to endDay
19%9%37%25%7%
81
March1st to 15thDay
26%7%33%30%2
90
16th to endDay
29%8%27%27%8%
96
April1st to 15thDay
18%14%29%25%10%1
255
16th to endDay
30%9%30%19%9%1
443
May1st to 15thDay
23%10%32%23%8%2
468
16th to endDay
20%5%32%26%11%3
517
June1st to 15thDay
15%6%30%28%16%2
495
16th to endDay
11%5%33%31%15%3
495
July1st to 15thDay
8%6%23%31%22%6%
475
16th to endDay
7%422%34%25%3
515
August1st to 15thDay
10%222%33%27%3
493
16th to endDay
14%324%31%20%5%
481
September1st to 15thDay
9%5%26%36%15%6%
312
16th to endDay
21%7%28%27%8%6%
135
October1st to 15thDay
14%11%38%18%11%5%
135
16th to endDay
22%11%35%15%13%1
144
November1st to 15thDay
310%25%44%13%3
90
16th to endDay
36%5%38%14%4
90
December1st to 15thDay
18%12%30%31%7%
90
16th to endDay
36%11%34%15%2
96
January1st to 15thNight
12%12%35%29%9%1
900
16th to endNight
16%10%36%30%5%
960
February1st to 15thNight
14%10%33%32%8%1
880
16th to endNight
12%9%38%28%9%1
786
March1st to 15thNight
17%7%35%28%10%
542
16th to endNight
18%9%30%29%10%1
576
April1st to 15thNight
19%7%36%27%9%
539
16th to endNight
27%8%28%26%8%1
540
May1st to 15thNight
20%9%34%27%8%
540
16th to endNight
16%6%30%32%11%1
563
June1st to 15thNight
14%430%38%12%
540
16th to endNight
8%230%44%14%
540
July1st to 15thNight
5%128%41%22%1
510
16th to endNight
6%122%46%21%1
564
August1st to 15thNight
8%216%43%27%1
539
16th to endNight
8%222%38%24%3
573
September1st to 15thNight
9%325%37%21%3
540
16th to endNight
12%7%33%27%16%2
555
October1st to 15thNight
19%6%33%26%12%1
720
16th to endNight
24%8%27%30%7%
768
November1st to 15thNight
16%9%32%30%10%
868
16th to endNight
17%11%34%26%9%
900
December1st to 15thNight
18%8%36%29%6%
900
16th to endNight
23%9%30%28%6%
960
Page generated at 2017-11-01 16:23:29. Version ac04

Copyright 2017 A. Danko


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