Galliano
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Galliano 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
63%
15049
22%
47304
20%
15009
67%
15009
31%
28222

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
47%
719
23%
2148
13%
716
55%
716
29%
1342
January16th to endNight
42%
768
24%
2304
14%
768
49%
768
26%
1482
February1st to 15thNight
50%
702
24%
2112
15%
701
56%
701
30%
1303
February16th to endNight
45%
631
22%
1893
13%
631
52%
631
28%
1187
March1st to 15thNight
47%
594
24%
2034
18%
594
54%
594
27%
1198
March16th to endNight
60%
576
23%
2049
21%
576
66%
576
30%
1123
April1st to 15thNight
59%
539
27%
1797
24%
539
65%
539
33%
999
April16th to endNight
63%
540
27%
1800
27%
540
68%
540
35%
972
May1st to 15thNight
72%
539
20%
1799
23%
539
75%
539
35%
982
May16th to endNight
76%
561
21%
1869
24%
561
77%
561
33%
1042
June1st to 15thNight
77%
540
14%
1800
17%
540
77%
540
28%
1086
June16th to endNight
73%
540
13%
1647
15%
540
73%
540
28%
1043
July1st to 15thNight
80%
510
13%
1539
14%
510
80%
510
30%
956
July16th to endNight
80%
564
9%
1772
13%
531
79%
531
24%
1137
August1st to 15thNight
84%
539
14%
1788
17%
536
84%
536
31%
1044
August16th to endNight
76%
573
14%
1910
16%
573
76%
573
22%
1252
September1st to 15thNight
74%
540
18%
1800
19%
540
75%
540
26%
1091
September16th to endNight
74%
678
26%
1941
24%
678
74%
678
33%
1209
October1st to 15thNight
76%
720
29%
2091
26%
720
78%
720
45%
1127
October16th to endNight
65%
768
32%
2304
27%
768
69%
768
39%
1273
November1st to 15thNight
66%
700
33%
2100
30%
700
69%
700
37%
1201
November16th to endNight
60%
720
32%
2235
27%
720
67%
720
37%
1245
December1st to 15thNight
54%
720
25%
2268
21%
720
59%
720
28%
1393
December16th to endNight
46%
768
21%
2304
16%
768
50%
768
24%
1535

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
9%5%25%5%35%5%7%9%39%
48401
Night
8%42442446%9%47%
47517
TransparencyDay
35%9%15%19%13%5%
48117
Night
32%7%15%20%16%6%
47307
SeeingDay
10%110%21%33%22%
5312
Night
10%314%27%31%13%
15055

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
11%5%26%435%47%7%41%
1790
16th to endDay
15%7%35%424335%44%
1920
February1st to 15thDay
11%5%2442445%7%47%
1750
16th to endDay
13%6%34434447%42%
1580
March1st to 15thDay
12%6%25%41445%8%44%
1935
16th to endDay
7%5%245%2445%8%49%
2171
April1st to 15thDay
8%4135%345%6%9%46%
2151
16th to endDay
7%425%5%35%46%8%46%
2160
May1st to 15thDay
6%425%425%5%7%11%43%
2151
16th to endDay
5%425%4346%8%11%43%
2244
June1st to 15thDay
7%5%36%8%37%7%9%11%30%
2160
16th to endDay
5%437%7%5%8%8%10%12%26%
2307
July1st to 15thDay
6%435%7%48%10%11%13%25%
2325
16th to endDay
8%5%38%8%48%8%8%11%22%
2276
August1st to 15thDay
7%5%36%8%5%8%7%10%13%22%
2160
16th to endDay
10%6%37%7%37%7%9%9%26%
2292
September1st to 15thDay
9%426%6%46%8%7%11%31%
2160
16th to endDay
7%5%26%6%45%6%7%9%37%
2007
October1st to 15thDay
5%32342445%9%52%
1866
16th to endDay
5%31342445%8%56%
1919
November1st to 15thDay
7%5%2432335%8%52%
1758
16th to endDay
7%41442245%6%55%
1716
December1st to 15thDay
11%5%24335%46%7%44%
1683
16th to endDay
17%7%35%5%25%446%36%
1920
January1st to 15thNight
13%5%26%324448%45%
2148
16th to endNight
13%6%35%424346%44%
2304
February1st to 15thNight
11%4245%25%35%6%47%
2103
16th to endNight
13%5%35%334336%47%
1893
March1st to 15thNight
11%5%24433447%47%
2034
16th to endNight
7%42442445%6%52%
2049
April1st to 15thNight
8%32442445%7%52%
1797
16th to endNight
5%4244335%6%7%52%
1800
May1st to 15thNight
42234246%7%10%50%
1799
16th to endNight
5%32442446%9%51%
1869
June1st to 15thNight
5%325%5%346%9%11%43%
1800
16th to endNight
6%5%35%5%35%5%6%11%41%
1647
July1st to 15thNight
3424425%6%7%12%45%
1629
16th to endNight
5%325%5%37%7%9%13%38%
1892
August1st to 15thNight
32134346%8%14%47%
1800
16th to endNight
7%4245%46%6%8%11%39%
1910
September1st to 15thNight
7%3235%25%7%9%12%39%
1800
16th to endNight
7%4244346%6%11%45%
1941
October1st to 15thNight
431332345%7%60%
2091
16th to endNight
8%3133245%46%56%
2304
November1st to 15thNight
8%42442435%7%53%
2100
16th to endNight
6%423424445%56%
2235
December1st to 15thNight
11%5%3442435%7%46%
2268
16th to endNight
14%6%36%5%25%46%7%37%
2304

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
41%6%10%15%19%6%
1791
16th to endDay
42%47%18%18%8%
1920
February1st to 15thDay
35%6%10%18%21%8%
1752
16th to endDay
40%6%11%17%19%5%
1580
March1st to 15thDay
36%7%12%22%15%5%
1935
16th to endDay
31%6%15%23%16%5%
2173
April1st to 15thDay
31%8%15%19%17%7%
2151
16th to endDay
31%7%16%25%14%4
2160
May1st to 15thDay
29%7%19%24%12%7%
2151
16th to endDay
28%9%18%26%16%1
2248
June1st to 15thDay
38%11%17%21%9%
2160
16th to endDay
39%14%20%17%7%
2307
July1st to 15thDay
36%18%24%18%1
2187
16th to endDay
46%15%21%13%2
2133
August1st to 15thDay
40%18%24%14%2
2148
16th to endDay
44%14%21%13%5%
2292
September1st to 15thDay
38%13%19%15%10%2
2160
16th to endDay
36%9%16%18%14%3
2007
October1st to 15thDay
25%8%14%21%20%10%
1866
16th to endDay
25%5%8%20%25%14%
1919
November1st to 15thDay
30%5%9%26%20%7%
1758
16th to endDay
29%5%9%17%24%13%
1716
December1st to 15thDay
37%8%12%23%13%5%
1683
16th to endDay
46%5%11%18%13%4
1920
January1st to 15thNight
37%5%10%16%20%9%
2148
16th to endNight
41%48%14%19%11%
2304
February1st to 15thNight
37%49%18%20%10%
2112
16th to endNight
38%5%9%15%19%11%
1893
March1st to 15thNight
36%5%11%20%19%6%
2034
16th to endNight
31%5%14%21%19%7%
2049
April1st to 15thNight
29%6%13%23%16%10%
1797
16th to endNight
28%6%13%26%19%5%
1800
May1st to 15thNight
25%9%15%27%15%6%
1800
16th to endNight
29%7%15%25%19%1
1871
June1st to 15thNight
31%11%16%25%14%
1800
16th to endNight
35%9%23%21%9%
1647
July1st to 15thNight
30%12%30%22%3
1539
16th to endNight
32%15%30%17%3
1772
August1st to 15thNight
24%15%32%24%3
1788
16th to endNight
36%14%23%18%5%2
1910
September1st to 15thNight
33%10%21%16%13%3
1800
16th to endNight
31%10%17%21%14%5%
1941
October1st to 15thNight
23%5%12%22%21%13%
2091
16th to endNight
28%48%17%25%16%
2304
November1st to 15thNight
30%48%23%24%7%
2100
16th to endNight
29%5%7%18%24%14%
2235
December1st to 15thNight
37%6%11%23%16%5%
2268
16th to endNight
43%6%10%18%14%6%
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
22%418%40%14%
90
16th to endDay
16%10%33%31%8%
96
February1st to 15thDay
6%435%31%17%4
90
16th to endDay
13%323%40%18%
81
March1st to 15thDay
27%331%26%11%
90
16th to endDay
10%322%29%29%3
157
April1st to 15thDay
12%418%38%25%
270
16th to endDay
9%217%34%28%7%
270
May1st to 15thDay
8%214%31%35%6%
288
16th to endDay
8%18%26%35%19%
331
June1st to 15thDay
13%5%13%40%25%
315
16th to endDay
8%412%41%32%
462
July1st to 15thDay
5%37%38%45%
461
16th to endDay
8%110%34%45%
326
August1st to 15thDay
9%6%32%50%
313
16th to endDay
9%16%11%28%42%
332
September1st to 15thDay
11%5%17%32%32%
315
16th to endDay
7%5%15%49%21%
314
October1st to 15thDay
5%9%25%46%12%
201
16th to endDay
8%213%34%34%6%
144
November1st to 15thDay
16%411%32%27%7%
90
16th to endDay
6%220%42%22%6%
90
December1st to 15thDay
12%8%18%41%16%2
90
16th to endDay
29%223%23%20%
96
January1st to 15thNight
15%6%24%39%12%1
720
16th to endNight
16%8%26%33%14%
768
February1st to 15thNight
14%5%24%34%19%1
704
16th to endNight
16%5%28%35%14%
631
March1st to 15thNight
13%5%26%32%20%1
594
16th to endNight
9%5%18%31%32%2
576
April1st to 15thNight
9%420%36%27%1
539
16th to endNight
7%220%36%30%2
540
May1st to 15thNight
415%36%39%3
540
16th to endNight
7%17%26%45%11%
563
June1st to 15thNight
5%414%54%20%
540
16th to endNight
7%1411%41%34%
540
July1st to 15thNight
427%35%50%
510
16th to endNight
5%1441%47%
564
August1st to 15thNight
31436%53%
539
16th to endNight
8%39%39%38%
573
September1st to 15thNight
9%1310%41%33%
540
16th to endNight
10%317%51%17%
678
October1st to 15thNight
6%18%31%40%12%
720
16th to endNight
10%315%29%33%7%
768
November1st to 15thNight
10%213%35%31%6%
700
16th to endNight
8%420%37%25%3
720
December1st to 15thNight
13%6%17%37%23%2
720
16th to endNight
17%6%22%34%16%2
768
Page generated at 2017-11-01 16:23:37. Version ac04

Copyright 2017 A. Danko


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