Nassau
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Nassau clear sky chart from 2005-11-06 to 2024-01-14.

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
0%
4771
0%
48842
0%
4142
0%
4142
28%
48939

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 10thNight
0%
184
0%
1246
0%
157
0%
157
32%
1368
January11th to 20thNight
0%
202
0%
1391
0%
170
0%
170
26%
1443
January21st to endNight
0%
229
0%
1371
0%
183
0%
183
30%
1475
February1st to 10thNight
0%
164
0%
1060
0%
132
0%
132
36%
1254
February11th to 20thNight
0%
168
0%
935
0%
120
0%
120
40%
1164
February21st to endNight
0%
92
0%
670
0%
74
0%
74
46%
892
March1st to 10thNight
0%
208
0%
940
0%
142
0%
142
37%
1192
March11th to 20thNight
0%
127
0%
906
0%
86
0%
86
44%
1114
March21st to endNight
0%
159
0%
999
0%
121
0%
121
41%
1266
April1st to 10thNight
0%
75
0%
817
0%
57
0%
57
52%
1004
April11th to 20thNight
0%
131
0%
1055
0%
121
0%
121
39%
1109
April21st to endNight
0%
104
0%
931
0%
81
0%
81
39%
1124
May1st to 10thNight
0%
91
0%
904
0%
79
0%
79
45%
1085
May11th to 20thNight
0%
168
0%
1269
0%
162
0%
162
25%
1291
May21st to endNight
0%
171
0%
1381
0%
169
0%
169
25%
1403
June1st to 10thNight
0%
166
0%
1574
0%
165
0%
165
15%
1454
June11th to 20thNight
0%
72
0%
1505
0%
72
0%
72
21%
1366
June21st to endNight
0%
55
0%
1475
0%
55
0%
55
25%
1204
July1st to 10thNight
0%
39
0%
1280
0%
39
0%
39
24%
1053
July11th to 20thNight
0%
68
0%
1416
0%
68
0%
68
30%
1188
July21st to endNight
0%
44
0%
1441
0%
38
0%
38
35%
1204
August1st to 10thNight
0%
62
0%
1368
0%
62
0%
62
32%
1187
August11th to 20thNight
0%
39
0%
1417
0%
38
0%
38
33%
1168
August21st to endNight
0%
94
0%
1654
0%
93
0%
93
25%
1424
September1st to 10thNight
0%
80
0%
1489
0%
77
0%
77
25%
1294
September11th to 20thNight
0%
56
0%
1459
0%
55
0%
55
28%
1250
September21st to endNight
0%
87
0%
1764
0%
87
0%
87
18%
1541
October1st to 10thNight
0%
132
0%
1670
0%
127
0%
127
20%
1549
October11th to 20thNight
0%
141
0%
1623
0%
138
0%
138
19%
1542
October21st to endNight
0%
215
0%
1604
0%
196
0%
196
20%
1695
November1st to 10thNight
0%
213
0%
1410
0%
179
0%
179
23%
1492
November11th to 20thNight
0%
199
0%
1549
0%
183
0%
183
19%
1641
November21st to endNight
0%
177
0%
1408
0%
157
0%
157
27%
1488
December1st to 10thNight
0%
141
0%
1270
0%
118
0%
118
31%
1385
December11th to 20thNight
0%
200
0%
1670
0%
170
0%
170
21%
1787
December21st to endNight
0%
218
0%
2921
0%
171
0%
171
16%
2843

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
TransparencyDay
37%10%20%22%10%1
75111
Night
38%9%19%22%11%1
74145
SeeingDay
7%29%25%38%19%
16099
Night
8%29%26%39%17%
26196

By Month

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 10thDay
33%9%15%29%14%1
1896
11th to 20thDay
38%6%17%24%12%2
1831
21st to endDay
33%7%17%26%15%2
1980
February1st to 10thDay
30%6%12%31%19%2
1800
11th to 20thDay
27%6%14%28%22%3
1871
21st to endDay
23%410%31%29%3
1628
March1st to 10thDay
31%6%11%29%21%2
1980
11th to 20thDay
25%6%16%36%14%3
1980
21st to endDay
25%7%14%31%21%2
2178
April1st to 10thDay
21%6%20%40%12%2
2089
11th to 20thDay
30%7%23%28%11%1
2134
21st to endDay
28%8%19%29%15%2
2160
May1st to 10thDay
22%9%20%30%16%3
2160
11th to 20thDay
45%10%19%22%5%
2128
21st to endDay
47%8%18%18%8%
2336
June1st to 10thDay
60%11%19%8%1
2160
11th to 20thDay
47%15%23%14%1
2160
21st to endDay
44%14%32%10%
2245
July1st to 10thDay
39%12%33%16%
2245
11th to 20thDay
40%13%33%14%
2096
21st to endDay
37%15%32%15%1
2220
August1st to 10thDay
36%12%31%19%2
2136
11th to 20thDay
35%15%35%14%
2126
21st to endDay
45%13%29%12%1
2376
September1st to 10thDay
44%16%27%12%2
2160
11th to 20thDay
39%15%27%17%2
2159
21st to endDay
48%14%23%13%2
1877
October1st to 10thDay
47%10%23%15%41
1800
11th to 20thDay
48%9%16%20%7%
1800
21st to endDay
44%9%13%19%13%2
1980
November1st to 10thDay
37%7%13%26%15%2
1857
11th to 20thDay
45%7%14%20%11%2
1900
21st to endDay
33%9%16%24%16%1
1900
December1st to 10thDay
30%6%17%31%16%
1900
11th to 20thDay
38%7%11%22%18%5%
2387
21st to endDay
40%10%15%19%14%1
3476
January1st to 10thNight
34%7%14%29%15%1
2270
11th to 20thNight
41%7%15%24%12%1
2207
21st to endNight
35%8%15%27%14%2
2376
February1st to 10thNight
30%7%12%31%19%1
2160
11th to 20thNight
29%6%12%28%21%4
1981
21st to endNight
23%6%12%29%27%3
1628
March1st to 10thNight
32%5%11%27%23%3
1980
11th to 20thNight
24%7%15%34%18%2
1980
21st to endNight
28%6%12%30%22%3
2178
April1st to 10thNight
19%6%18%39%14%3
1868
11th to 20thNight
31%7%22%25%14%2
1775
21st to endNight
30%7%14%30%16%2
1800
May1st to 10thNight
27%6%17%29%18%3
1800
11th to 20thNight
46%9%17%24%5%
1771
21st to endNight
46%8%17%20%9%
1939
June1st to 10thNight
58%10%19%10%3
1800
11th to 20thNight
45%15%24%15%1
1800
21st to endNight
39%13%34%14%
1712
July1st to 10thNight
35%15%31%18%1
1575
11th to 20thNight
36%12%34%18%
1736
21st to endNight
29%13%36%21%2
1858
August1st to 10thNight
35%10%32%20%3
1778
11th to 20thNight
29%15%36%19%1
1774
21st to endNight
40%13%30%16%1
1980
September1st to 10thNight
38%15%29%16%2
1800
11th to 20thNight
37%12%32%17%2
1800
21st to endNight
47%14%24%13%2
2075
October1st to 10thNight
46%11%20%18%31
2160
11th to 20thNight
48%10%18%18%6%1
2160
21st to endNight
48%9%11%19%12%2
2376
November1st to 10thNight
42%9%12%23%12%1
2221
11th to 20thNight
51%7%10%19%11%2
2280
21st to endNight
38%10%14%21%15%1
2280
December1st to 10thNight
33%8%14%28%16%
2280
11th to 20thNight
42%8%10%23%16%2
2807
21st to endNight
49%8%13%18%11%1
4180

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 10thDay
7%416%32%35%6%
460
11th to 20thDay
10%5%19%32%29%6%
433
21st to endDay
6%6%18%44%25%1
462
February1st to 10thDay
6%414%35%38%2
420
11th to 20thDay
4214%35%38%7%
416
21st to endDay
6%212%34%39%7%
346
March1st to 10thDay
5%322%43%25%3
420
11th to 20thDay
4217%36%38%3
420
21st to endDay
5%214%37%35%7%
462
April1st to 10thDay
429%44%38%4
420
11th to 20thDay
7%211%46%33%2
412
21st to endDay
5%28%42%39%3
420
May1st to 10thDay
7%16%31%48%7%
423
11th to 20thDay
14%18%31%40%6%
447
21st to endDay
10%3417%47%18%
485
June1st to 10thDay
14%25%21%41%17%
450
11th to 20thDay
8%1413%36%38%
450
21st to endDay
337%41%45%
450
July1st to 10thDay
3128%39%46%
445
11th to 20thDay
5%7%48%40%
444
21st to endDay
3138%40%44%
488
August1st to 10thDay
5%15%48%40%
446
11th to 20thDay
327%40%47%
439
21st to endDay
7%313%41%36%
495
September1st to 10thDay
6%148%32%49%
450
11th to 20thDay
5%129%29%54%
450
21st to endDay
9%15%11%37%37%
450
October1st to 10thDay
10%15%21%44%18%
450
11th to 20thDay
12%25%22%38%21%
450
21st to endDay
12%29%26%41%10%
495
November1st to 10thDay
6%313%29%38%11%
455
11th to 20thDay
8%311%30%37%10%
460
21st to endDay
6%212%33%37%8%
460
December1st to 10thDay
7%212%32%39%9%
460
11th to 20thDay
10%313%29%40%7%
460
21st to endDay
8%315%31%37%6%
506
January1st to 10thNight
8%313%33%37%6%
760
11th to 20thNight
11%314%38%33%2
736
21st to endNight
6%5%18%38%31%2
792
February1st to 10thNight
7%313%42%33%3
720
11th to 20thNight
5%316%38%35%4
703
21st to endNight
5%29%38%43%4
592
March1st to 10thNight
6%320%40%28%3
720
11th to 20thNight
3213%42%36%4
720
21st to endNight
6%113%42%34%5%
792
April1st to 10thNight
218%44%43%3
720
11th to 20thNight
6%210%38%41%2
711
21st to endNight
5%18%46%39%1
720
May1st to 10thNight
5%16%31%47%10%
720
11th to 20thNight
13%29%34%38%5%
709
21st to endNight
13%36%17%46%15%
778
June1st to 10thNight
15%35%19%43%15%
720
11th to 20thNight
7%1310%45%35%
720
21st to endNight
5%39%45%37%
632
July1st to 10thNight
5%127%44%42%
525
11th to 20thNight
7%29%44%37%
692
21st to endNight
4126%39%49%
787
August1st to 10thNight
6%128%43%41%
717
11th to 20thNight
329%40%45%
710
21st to endNight
8%1211%42%35%
792
September1st to 10thNight
6%15%8%33%48%
720
11th to 20thNight
5%128%33%52%
720
21st to endNight
8%1313%37%39%
720
October1st to 10thNight
13%15%16%44%22%
720
11th to 20thNight
12%26%21%39%21%
720
21st to endNight
15%210%25%36%12%
792
November1st to 10thNight
10%315%29%35%8%
740
11th to 20thNight
12%311%29%38%7%
760
21st to endNight
8%214%35%36%6%
760
December1st to 10thNight
7%110%31%45%6%
760
11th to 20thNight
11%213%29%39%6%
760
21st to endNight
8%414%31%35%8%
836
Page generated at 2024-01-11 13:32:00. Version ac07

Copyright 2024 Attilla Danko


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