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 2017-03-24.

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%
15856
15%
45152
13%
15818
66%
15818
25%
30684

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
67%
740
20%
2035
18%
740
69%
740
34%
1259
April1st to 15thNight
73%
658
22%
1737
19%
658
74%
658
42%
1007
April16th to endNight
69%
660
19%
1650
13%
660
71%
660
37%
1054
May1st to 15thNight
80%
659
22%
1649
14%
659
81%
659
42%
1003
May16th to endNight
68%
680
9%
1705
5%
680
68%
680
23%
1255
June1st to 15thNight
59%
495
9%
1485
8%
495
59%
495
15%
1143
June16th to endNight
73%
495
9%
1485
8%
495
73%
495
22%
1031
July1st to 15thNight
69%
465
5%
1395
4%
465
69%
465
17%
1016
July16th to endNight
78%
522
8%
1469
6%
489
79%
489
27%
951
August1st to 15thNight
76%
656
8%
1635
6%
652
76%
652
28%
1137
August16th to endNight
71%
700
6%
1750
4%
700
71%
700
23%
1290
September1st to 15thNight
66%
660
6%
1732
6%
660
66%
660
16%
1365
September16th to endNight
59%
657
6%
1826
6%
657
59%
657
14%
1457
October1st to 15thNight
63%
660
13%
1980
15%
660
63%
660
20%
1416
October16th to endNight
57%
704
15%
2112
16%
704
58%
704
22%
1461
November1st to 15thNight
61%
700
18%
2101
18%
700
63%
700
24%
1391
November16th to endNight
57%
720
17%
2160
18%
720
59%
720
22%
1488
December1st to 15thNight
58%
720
16%
2160
15%
720
60%
720
19%
1529
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%
45765
Night
7%425%6%35%6%7%11%37%
45355
TransparencyDay
41%13%18%16%8%1
45469
Night
39%11%19%18%9%1
45156
SeeingDay
9%210%24%30%22%
5588
Night
9%211%26%32%17%
15865

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
7%5%25%5%46%6%8%12%34%
2033
April1st to 15thDay
5%4245%35%7%9%13%38%
1881
16th to endDay
6%3245%47%6%9%12%36%
1980
May1st to 15thDay
4313445%6%8%12%44%
1972
16th to endDay
10%6%37%9%48%8%9%10%19%
2063
June1st to 15thDay
12%6%47%8%5%8%7%8%11%18%
2145
16th to endDay
10%6%37%6%48%9%10%12%20%
2145
July1st to 15thDay
8%7%48%7%5%9%7%8%10%20%
2145
16th to endDay
6%5%37%7%48%9%11%13%21%
2272
August1st to 15thDay
8%6%26%8%5%8%9%9%13%21%
1980
16th to endDay
9%6%48%9%5%8%8%9%13%17%
2100
September1st to 15thDay
8%6%37%10%6%10%9%10%11%14%
1895
16th to endDay
11%8%310%9%5%8%8%9%10%14%
1804
October1st to 15thDay
10%6%36%7%47%8%10%12%22%
1650
16th to endDay
12%5%36%7%5%6%7%6%11%26%
1760
November1st to 15thDay
8%5%35%7%47%6%7%10%32%
1757
16th to endDay
11%6%37%7%37%5%7%9%31%
1800
December1st to 15thDay
11%6%37%6%46%6%7%10%27%
1800
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
4214436%6%6%10%48%
2035
April1st to 15thNight
6%21332446%9%54%
1737
16th to endNight
6%4234246%7%12%45%
1650
May1st to 15thNight
4312425%5%7%12%50%
1649
16th to endNight
9%5%35%6%46%7%9%11%31%
1705
June1st to 15thNight
12%6%37%7%46%8%7%10%25%
1485
16th to endNight
6%4246%47%7%9%12%34%
1485
July1st to 15thNight
9%5%35%5%35%7%10%13%30%
1485
16th to endNight
43246%46%6%9%12%40%
1577
August1st to 15thNight
4325%6%25%6%9%16%36%
1647
16th to endNight
7%425%6%46%7%8%15%31%
1750
September1st to 15thNight
7%5%36%9%46%7%10%13%25%
1732
16th to endNight
8%6%49%9%5%6%7%8%9%23%
1826
October1st to 15thNight
9%6%37%7%35%6%8%10%31%
1980
16th to endNight
12%6%36%6%45%46%8%34%
2112
November1st to 15thNight
8%436%5%36%6%6%9%38%
2101
16th to endNight
8%426%7%46%6%7%11%33%
2160
December1st to 15thNight
9%6%36%7%36%6%6%10%33%
2160
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
34%10%19%20%13%2
2034
April1st to 15thDay
27%10%23%24%12%1
1881
16th to endDay
31%9%18%21%17%2
1980
May1st to 15thDay
24%9%22%26%14%2
1972
16th to endDay
46%14%19%15%4
2067
June1st to 15thDay
49%15%18%13%2
2145
16th to endDay
44%20%22%11%
2145
July1st to 15thDay
48%18%23%7%
2006
16th to endDay
38%21%27%10%1
2118
August1st to 15thDay
41%20%26%10%
1968
16th to endDay
48%19%22%8%
2100
September1st to 15thDay
50%23%16%8%1
1895
16th to endDay
53%18%16%7%3
1804
October1st to 15thDay
43%14%17%14%9%
1650
16th to endDay
46%9%14%14%12%2
1760
November1st to 15thDay
41%9%15%17%14%2
1757
16th to endDay
45%8%12%15%15%3
1800
December1st to 15thDay
47%9%15%15%10%1
1800
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%10%16%25%14%2
2035
April1st to 15thNight
24%9%22%27%14%2
1737
16th to endNight
30%9%19%19%17%3
1650
May1st to 15thNight
25%9%17%27%17%2
1650
16th to endNight
43%12%21%18%4
1707
June1st to 15thNight
51%13%18%13%3
1485
16th to endNight
37%16%29%15%1
1485
July1st to 15thNight
42%17%27%11%1
1395
16th to endNight
31%14%35%15%1
1469
August1st to 15thNight
32%17%33%16%
1635
16th to endNight
39%16%31%11%
1750
September1st to 15thNight
45%20%21%11%1
1732
16th to endNight
51%16%17%9%3
1826
October1st to 15thNight
44%11%17%15%9%
1980
16th to endNight
47%6%14%18%11%2
2112
November1st to 15thNight
40%9%13%19%14%2
2101
16th to endNight
44%9%12%17%12%3
2160
December1st to 15thNight
45%11%14%18%9%1
2160
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
6%219%42%25%3
260
April1st to 15thDay
7%114%34%35%6%
210
16th to endDay
6%113%33%38%6%
210
May1st to 15thDay
5%7%27%39%18%
228
16th to endDay
8%5%17%37%29%
267
June1st to 15thDay
11%1316%35%31%
255
16th to endDay
7%39%25%54%
255
July1st to 15thDay
7%26%27%55%
245
16th to endDay
6%18%35%47%
270
August1st to 15thDay
9%16%39%41%
253
16th to endDay
11%36%26%51%
268
September1st to 15thDay
10%112%30%44%
255
16th to endDay
11%49%24%49%
254
October1st to 15thDay
10%8%21%42%16%
255
16th to endDay
13%114%33%26%11%
272
November1st to 15thDay
8%112%33%32%11%
265
16th to endDay
7%321%34%30%2
270
December1st to 15thDay
14%215%32%32%2
270
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%216%40%29%4
740
April1st to 15thNight
5%210%37%39%4
658
16th to endNight
7%113%37%37%2
660
May1st to 15thNight
5%6%35%42%10%
660
16th to endNight
10%17%25%36%18%
682
June1st to 15thNight
12%15%17%37%26%
495
16th to endNight
7%38%34%45%
495
July1st to 15thNight
9%39%33%42%
465
16th to endNight
417%33%52%
522
August1st to 15thNight
5%18%39%44%
656
16th to endNight
8%128%30%48%
700
September1st to 15thNight
9%311%29%45%
660
16th to endNight
11%49%32%40%
657
October1st to 15thNight
11%17%20%40%17%
660
16th to endNight
16%112%25%32%12%
704
November1st to 15thNight
9%315%30%34%7%
700
16th to endNight
8%320%30%33%3
720
December1st to 15thNight
10%316%34%31%3
720
16th to endNight
9%314%30%34%8%
768
Page generated at 2017-03-25 12:39:44. Version ac04

Copyright 2017 A. Danko


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