Nassau
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Nassau clear sky chart from 2005-11-05 to 2017-09-23.

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
0%
5184
0%
31622
0%
4237
0%
4237
23%
31874

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
0%
286
0%
1400
0%
235
0%
235
20%
1421
January16th to endNight
0%
301
0%
1308
0%
238
0%
238
26%
1415
February1st to 15thNight
0%
260
0%
1070
0%
189
0%
189
29%
1266
February16th to endNight
0%
204
0%
859
0%
124
0%
124
34%
1012
March1st to 15thNight
0%
285
0%
1121
0%
213
0%
213
27%
1256
March16th to endNight
0%
243
0%
1127
0%
159
0%
159
31%
1279
April1st to 15thNight
0%
183
0%
898
0%
126
0%
126
39%
1054
April16th to endNight
0%
232
0%
1007
0%
150
0%
150
30%
1158
May1st to 15thNight
0%
177
0%
869
0%
117
0%
117
38%
1083
May16th to endNight
0%
240
0%
1395
0%
231
0%
231
20%
1403
June1st to 15thNight
0%
225
0%
1579
0%
219
0%
219
15%
1444
June16th to endNight
0%
157
0%
1487
0%
149
0%
149
20%
1294
July1st to 15thNight
0%
108
0%
1310
0%
108
0%
108
20%
1152
July16th to endNight
0%
179
0%
1363
0%
126
0%
126
29%
1206
August1st to 15thNight
0%
118
0%
1351
0%
107
0%
107
27%
1215
August16th to endNight
0%
162
0%
1599
0%
156
0%
156
22%
1416
September1st to 15thNight
0%
148
0%
1528
0%
144
0%
144
21%
1343
September16th to endNight
0%
153
0%
1651
0%
141
0%
141
16%
1440
October1st to 15thNight
0%
188
0%
1592
0%
176
0%
176
16%
1478
October16th to endNight
0%
277
0%
1566
0%
247
0%
247
13%
1614
November1st to 15thNight
0%
280
0%
1421
0%
240
0%
240
16%
1518
November16th to endNight
0%
288
0%
1394
0%
243
0%
243
20%
1493
December1st to 15thNight
0%
247
0%
1407
0%
209
0%
209
19%
1450
December16th to endNight
0%
243
0%
1320
0%
190
0%
190
25%
1464

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
41%8%19%20%8%1
47785
Night
41%8%17%21%9%1
46797
SeeingDay
9%10%5%19%33%22%
6904
Night
9%15%419%32%17%
17080

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 15thDay
40%7%19%22%8%
1791
16th to endDay
34%5%16%27%14%1
1920
February1st to 15thDay
33%6%11%29%17%2
1769
16th to endDay
29%413%31%17%2
1738
March1st to 15thDay
35%6%14%24%17%1
1980
16th to endDay
30%6%17%29%13%3
2112
April1st to 15thDay
26%5%19%35%11%2
2105
16th to endDay
30%6%19%28%14%1
2160
May1st to 15thDay
22%7%19%32%15%2
2152
16th to endDay
50%7%19%18%3
2248
June1st to 15thDay
58%11%19%8%1
2160
16th to endDay
49%12%25%11%
2216
July1st to 15thDay
49%11%25%13%
2126
16th to endDay
42%13%27%15%
2132
August1st to 15thDay
41%11%28%16%1
2148
16th to endDay
48%12%25%12%
2292
September1st to 15thDay
48%15%25%9%
2160
16th to endDay
50%12%22%12%3
1889
October1st to 15thDay
55%7%19%11%4
1650
16th to endDay
52%6%11%18%8%1
1760
November1st to 15thDay
45%5%11%22%14%
1757
16th to endDay
40%7%14%20%14%3
1800
December1st to 15thDay
37%6%17%24%14%
1800
16th to endDay
31%7%12%28%20%
1920
January1st to 15thNight
43%6%16%23%10%
2148
16th to endNight
35%6%14%27%14%1
2304
February1st to 15thNight
33%6%11%27%17%4
2093
16th to endNight
28%5%15%33%14%2
1735
March1st to 15thNight
37%5%13%23%18%1
1980
16th to endNight
30%6%15%28%16%2
2112
April1st to 15thNight
24%5%18%35%13%2
1841
16th to endNight
33%6%15%26%14%2
1800
May1st to 15thNight
27%5%15%31%17%3
1800
16th to endNight
50%7%16%21%4
1870
June1st to 15thNight
58%9%20%9%2
1800
16th to endNight
44%13%27%14%
1742
July1st to 15thNight
44%13%25%16%
1583
16th to endNight
36%10%29%21%1
1773
August1st to 15thNight
35%11%28%21%3
1787
16th to endNight
46%10%26%15%1
1910
September1st to 15thNight
43%14%27%14%
1800
16th to endNight
48%12%25%10%2
1902
October1st to 15thNight
52%9%19%14%21
1980
16th to endNight
57%7%9%16%7%1
2112
November1st to 15thNight
51%7%9%20%11%
2101
16th to endNight
45%8%11%16%16%2
2160
December1st to 15thNight
44%6%14%21%13%
2160
16th to endNight
38%6%12%25%17%
2304

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
11%15%8%32%29%2
270
16th to endDay
9%13%11%36%24%3
288
February1st to 15thDay
8%12%12%31%31%3
266
16th to endDay
6%13%8%41%28%1
239
March1st to 15thDay
7%12%14%33%28%4
270
16th to endDay
10%11%9%34%27%6%
288
April1st to 15thDay
7%11%5%35%37%3
270
16th to endDay
7%12%8%34%34%2
270
May1st to 15thDay
310%223%45%14%
288
16th to endDay
12%10%8%41%25%
331
June1st to 15thDay
13%10%6%41%27%
315
16th to endDay
6%9%6%29%47%
315
July1st to 15thDay
7%7%237%45%
305
16th to endDay
7%10%130%50%
326
August1st to 15thDay
6%6%236%49%
313
16th to endDay
12%6%5%28%47%
332
September1st to 15thDay
7%6%2423%55%
315
16th to endDay
8%7%326%54%
283
October1st to 15thDay
18%8%114%37%19%
255
16th to endDay
26%8%5%23%25%11%
272
November1st to 15thDay
11%10%5%24%35%12%
265
16th to endDay
10%11%14%29%31%2
270
December1st to 15thDay
11%12%7%25%35%6%
270
16th to endDay
6%12%6%20%45%8%
288
January1st to 15thNight
13%18%7%25%30%4
720
16th to endNight
8%18%11%31%27%1
768
February1st to 15thNight
6%17%12%28%31%2
704
16th to endNight
6%16%8%34%31%1
631
March1st to 15thNight
9%18%11%29%26%4
720
16th to endNight
5%17%9%32%30%5%
768
April1st to 15thNight
317%433%38%2
718
16th to endNight
8%18%5%32%32%2
720
May1st to 15thNight
5%17%226%38%10%
720
16th to endNight
13%18%15%37%15%
749
June1st to 15thNight
13%17%7%35%25%
720
16th to endNight
6%17%6%36%33%
662
July1st to 15thNight
6%12%437%39%
563
16th to endNight
5%17%330%42%
753
August1st to 15thNight
6%9%433%45%
719
16th to endNight
11%9%6%34%38%
764
September1st to 15thNight
8%10%1427%47%
720
16th to endNight
12%9%228%46%
689
October1st to 15thNight
15%10%19%38%23%
660
16th to endNight
22%10%6%18%26%14%
704
November1st to 15thNight
16%15%7%25%28%6%
700
16th to endNight
13%18%8%25%30%4
720
December1st to 15thNight
10%18%5%24%36%4
720
16th to endNight
7%18%5%24%36%8%
768
Page generated at 2017-09-24 09:15:47. Version ac04

Copyright 2017 A. Danko


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