Freeport
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Freeport clear sky chart from 2005-11-05 to 2017-12-02.

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
65%
16800
15%
47766
13%
16762
67%
16762
25%
32303

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
58%
716
13%
2327
14%
716
60%
716
21%
1580
January16th to endNight
55%
768
19%
2496
18%
768
61%
768
24%
1607
February1st to 15thNight
54%
702
23%
2085
20%
701
59%
701
27%
1352
February16th to endNight
59%
631
21%
1735
17%
631
63%
631
32%
1103
March1st to 15thNight
63%
720
22%
1980
17%
720
67%
720
33%
1247
March16th to endNight
68%
768
22%
2112
20%
768
70%
768
35%
1292
April1st to 15thNight
73%
718
21%
1895
18%
718
74%
718
42%
1090
April16th to endNight
70%
720
20%
1800
13%
720
72%
720
38%
1145
May1st to 15thNight
79%
719
21%
1799
13%
719
80%
719
42%
1087
May16th to endNight
70%
743
11%
1864
8%
743
70%
743
25%
1343
June1st to 15thNight
58%
540
8%
1620
8%
540
58%
540
14%
1263
June16th to endNight
74%
540
10%
1620
8%
540
74%
540
23%
1113
July1st to 15thNight
71%
510
5%
1530
4%
510
71%
510
18%
1090
July16th to endNight
79%
564
8%
1595
6%
531
79%
531
28%
1024
August1st to 15thNight
76%
716
8%
1785
6%
712
76%
712
29%
1229
August16th to endNight
70%
764
7%
1910
5%
764
70%
764
23%
1406
September1st to 15thNight
67%
720
6%
1890
6%
720
67%
720
18%
1460
September16th to endNight
61%
717
8%
1992
9%
717
61%
717
15%
1565
October1st to 15thNight
63%
720
12%
2160
14%
720
63%
720
20%
1554
October16th to endNight
58%
768
15%
2304
16%
768
59%
768
22%
1589
November1st to 15thNight
62%
760
17%
2281
17%
760
64%
760
25%
1497
November16th to endNight
58%
780
19%
2340
19%
780
60%
780
23%
1588
December1st to 15thNight
59%
728
16%
2183
15%
728
61%
728
19%
1537
December16th to endNight
64%
768
19%
2463
20%
768
65%
768
26%
1542

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
8%5%36%7%47%7%8%11%27%
48666
Night
7%425%6%35%6%7%11%37%
47969
TransparencyDay
41%13%18%16%8%1
48370
Night
38%11%19%19%9%1
47770
SeeingDay
8%19%24%31%23%
6590
Night
9%211%26%33%17%
16809

By Month

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
10%7%46%7%37%7%8%11%25%
1611
16th to endDay
9%5%35%6%46%6%7%9%34%
1728
February1st to 15thDay
9%5%35%6%2446%11%39%
1769
16th to endDay
6%425%5%45%7%7%11%38%
1738
March1st to 15thDay
5%325%7%38%6%8%11%35%
1980
16th to endDay
6%425%5%47%6%8%12%35%
2111
April1st to 15thDay
5%4245%35%7%9%13%38%
2053
16th to endDay
6%3245%47%6%9%12%36%
2160
May1st to 15thDay
4313435%6%8%12%44%
2152
16th to endDay
9%6%36%9%48%8%9%11%21%
2256
June1st to 15thDay
12%7%48%8%5%8%7%9%11%17%
2340
16th to endDay
10%5%37%7%5%8%9%10%11%20%
2340
July1st to 15thDay
8%7%48%8%5%9%8%8%11%20%
2340
16th to endDay
5%5%37%7%48%9%11%13%21%
2453
August1st to 15thDay
7%5%25%8%5%8%9%9%13%23%
2160
16th to endDay
9%6%48%9%5%8%8%9%13%17%
2292
September1st to 15thDay
8%6%37%9%5%10%9%10%12%16%
2067
16th to endDay
11%8%310%9%5%8%8%9%10%15%
1968
October1st to 15thDay
10%6%36%7%47%8%10%12%21%
1800
16th to endDay
12%5%36%7%46%7%6%11%27%
1920
November1st to 15thDay
7%5%25%7%47%6%7%10%33%
1907
16th to endDay
11%5%36%7%37%5%7%9%32%
1950
December1st to 15thDay
11%6%37%6%46%6%7%10%27%
1814
16th to endDay
8%5%26%6%5%6%6%9%10%32%
1757
January1st to 15thNight
10%5%35%5%36%6%7%11%33%
2327
16th to endNight
8%435%5%45%6%6%10%40%
2496
February1st to 15thNight
9%5%25%6%25%45%7%43%
2078
16th to endNight
6%4246%35%5%7%9%43%
1735
March1st to 15thNight
43145%45%6%7%10%45%
1980
16th to endNight
4214435%6%6%10%49%
2112
April1st to 15thNight
6%21332446%10%54%
1895
16th to endNight
6%413435%6%7%12%46%
1800
May1st to 15thNight
4313425%5%7%11%51%
1799
16th to endNight
8%5%345%45%7%9%11%33%
1864
June1st to 15thNight
12%7%37%7%46%7%8%10%24%
1620
16th to endNight
6%4246%37%7%9%13%34%
1620
July1st to 15thNight
8%435%5%26%7%10%13%31%
1620
16th to endNight
43245%36%6%9%12%41%
1703
August1st to 15thNight
4425%6%25%6%8%15%37%
1797
16th to endNight
7%425%7%46%7%8%15%31%
1910
September1st to 15thNight
7%5%36%8%46%7%9%13%27%
1890
16th to endNight
8%6%38%8%5%6%7%9%10%25%
1992
October1st to 15thNight
9%6%37%7%36%6%8%10%30%
2160
16th to endNight
12%6%36%6%45%46%8%35%
2304
November1st to 15thNight
7%435%5%36%6%6%9%39%
2281
16th to endNight
8%426%7%46%5%7%10%35%
2340
December1st to 15thNight
8%6%36%7%36%6%6%10%33%
2183
16th to endNight
7%5%35%5%25%6%6%11%40%
2463

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
46%9%17%17%8%
1612
16th to endDay
41%8%12%20%14%1
1728
February1st to 15thDay
36%6%12%25%15%1
1772
16th to endDay
32%9%18%23%13%2
1738
March1st to 15thDay
33%11%16%23%12%1
1980
16th to endDay
33%10%19%20%13%2
2112
April1st to 15thDay
26%10%23%25%12%1
2053
16th to endDay
31%9%18%21%17%2
2160
May1st to 15thDay
24%9%21%26%14%4
2152
16th to endDay
44%13%19%17%4
2260
June1st to 15thDay
51%15%18%12%2
2340
16th to endDay
44%21%22%11%
2340
July1st to 15thDay
46%19%24%8%
2201
16th to endDay
38%22%27%10%1
2299
August1st to 15thDay
40%19%25%13%1
2148
16th to endDay
47%19%22%10%
2292
September1st to 15thDay
49%22%18%8%1
2067
16th to endDay
53%18%16%7%3
1968
October1st to 15thDay
43%14%17%14%8%
1800
16th to endDay
45%9%14%14%12%3
1920
November1st to 15thDay
40%9%15%18%14%2
1907
16th to endDay
45%8%11%16%15%3
1950
December1st to 15thDay
47%9%15%15%10%1
1814
16th to endDay
39%10%14%19%14%1
1757
January1st to 15thNight
42%10%17%20%9%
2327
16th to endNight
38%9%15%21%13%2
2496
February1st to 15thNight
39%7%9%23%16%4
2086
16th to endNight
33%8%18%23%12%2
1735
March1st to 15thNight
32%8%16%23%15%2
1980
16th to endNight
29%9%16%26%15%2
2112
April1st to 15thNight
23%8%22%27%14%2
1895
16th to endNight
30%9%19%20%17%3
1800
May1st to 15thNight
25%8%17%26%17%4
1800
16th to endNight
41%12%20%21%4
1866
June1st to 15thNight
52%14%18%12%3
1620
16th to endNight
36%16%30%15%1
1620
July1st to 15thNight
40%17%27%12%1
1530
16th to endNight
30%15%37%15%1
1595
August1st to 15thNight
31%17%31%17%1
1785
16th to endNight
39%16%30%12%
1910
September1st to 15thNight
43%19%22%13%1
1890
16th to endNight
49%17%17%11%4
1992
October1st to 15thNight
44%12%17%15%9%
2160
16th to endNight
46%7%14%17%12%2
2304
November1st to 15thNight
39%9%13%20%14%2
2281
16th to endNight
43%8%12%18%13%3
2340
December1st to 15thNight
45%11%13%18%9%1
2183
16th to endNight
37%8%17%20%14%1
2463

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
21%5%20%31%22%
90
16th to endDay
15%8%23%31%17%3
96
February1st to 15thDay
8%8%18%38%21%4
206
16th to endDay
5%5%22%44%21%
239
March1st to 15thDay
4319%47%21%3
270
16th to endDay
5%219%41%26%3
288
April1st to 15thDay
5%116%38%32%4
270
16th to endDay
5%111%40%35%5%
270
May1st to 15thDay
5%19%30%39%14%
288
16th to endDay
7%5%18%41%27%
331
June1st to 15thDay
14%1416%33%29%
315
16th to endDay
6%310%26%53%
315
July1st to 15thDay
6%16%28%56%
305
16th to endDay
6%18%33%50%
326
August1st to 15thDay
7%16%42%40%
313
16th to endDay
11%39%26%48%
332
September1st to 15thDay
10%211%28%46%
315
16th to endDay
10%410%26%47%
314
October1st to 15thDay
11%7%22%41%16%
315
16th to endDay
12%213%32%27%11%
336
November1st to 15thDay
7%11%33%36%10%
325
16th to endDay
7%320%37%29%2
330
December1st to 15thDay
14%214%33%32%2
276
16th to endDay
9%4427%44%10%
125
January1st to 15thNight
11%417%33%28%4
720
16th to endNight
10%6%19%39%22%1
768
February1st to 15thNight
9%422%38%22%2
704
16th to endNight
8%419%42%24%
631
March1st to 15thNight
5%319%41%25%3
720
16th to endNight
6%116%41%29%4
768
April1st to 15thNight
5%210%38%38%4
718
16th to endNight
7%112%39%36%2
720
May1st to 15thNight
5%6%35%42%9%
720
16th to endNight
10%17%24%38%17%
745
June1st to 15thNight
13%15%17%36%25%
540
16th to endNight
6%38%35%44%
540
July1st to 15thNight
9%38%35%42%
510
16th to endNight
5%16%34%52%
564
August1st to 15thNight
6%17%40%43%
716
16th to endNight
9%28%30%47%
764
September1st to 15thNight
9%410%28%46%
720
16th to endNight
11%410%33%40%
717
October1st to 15thNight
11%17%19%41%17%
720
16th to endNight
15%112%25%32%11%
768
November1st to 15thNight
8%315%29%35%6%
760
16th to endNight
8%319%32%33%3
780
December1st to 15thNight
10%316%34%32%3
728
16th to endNight
9%314%30%34%8%
768
Page generated at 2017-12-03 11:16:40. Version ac04

Copyright 2017 A. Danko


Freeport Clear Sky Chart |Charts Home