GaLunLaTi Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the GaLunLaTi Observatory 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
46%
15447
23%
47012
15%
15404
55%
15404
27%
29116

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
24%
720
23%
2327
9%
716
40%
716
20%
1465
January16th to endNight
24%
768
24%
2418
10%
768
40%
768
21%
1566
February1st to 15thNight
26%
704
24%
2112
8%
701
42%
701
24%
1308
February16th to endNight
21%
631
23%
1893
8%
631
35%
631
22%
1216
March1st to 15thNight
29%
720
21%
2090
11%
720
38%
720
25%
1327
March16th to endNight
36%
768
21%
2112
13%
768
42%
768
28%
1354
April1st to 15thNight
39%
590
25%
1848
15%
590
51%
590
30%
1062
April16th to endNight
47%
540
25%
1728
16%
540
57%
540
32%
992
May1st to 15thNight
49%
540
21%
1620
12%
540
58%
540
29%
1003
May16th to endNight
62%
561
22%
1682
15%
561
67%
561
34%
1005
June1st to 15thNight
72%
540
16%
1620
14%
540
74%
540
32%
989
June16th to endNight
76%
540
17%
1620
15%
540
77%
540
36%
955
July1st to 15thNight
72%
510
14%
1530
12%
510
74%
510
28%
983
July16th to endNight
73%
564
16%
1595
15%
531
74%
531
26%
1050
August1st to 15thNight
74%
539
19%
1681
21%
536
74%
536
30%
1045
August16th to endNight
66%
573
19%
1910
21%
573
68%
573
23%
1264
September1st to 15thNight
64%
678
17%
1938
16%
678
65%
678
27%
1295
September16th to endNight
59%
689
26%
1903
19%
689
65%
689
32%
1186
October1st to 15thNight
53%
660
33%
1815
25%
660
60%
660
38%
1054
October16th to endNight
49%
704
32%
2118
25%
704
59%
704
35%
1192
November1st to 15thNight
47%
700
29%
2276
23%
700
58%
700
34%
1232
November16th to endNight
37%
720
27%
2340
17%
720
51%
720
27%
1372
December1st to 15thNight
29%
720
22%
2340
11%
720
43%
720
22%
1492
December16th to endNight
29%
768
19%
2496
12%
768
38%
768
18%
1709

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
12%5%25%5%35%5%5%7%40%
47886
Night
11%5%2443445%7%45%
47211
TransparencyDay
40%7%12%18%17%4
47587
Night
36%6%11%20%19%5%
47014
SeeingDay
14%7%21%23%20%12%
5335
Night
14%9%24%27%20%3
15449

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
17%8%24433345%43%
1611
16th to endDay
15%7%25%424345%43%
1803
February1st to 15thDay
16%6%24324346%42%
1750
16th to endDay
18%5%36%425%335%41%
1580
March1st to 15thDay
16%6%26%5%33447%40%
1869
16th to endDay
15%6%25%42435%6%41%
2111
April1st to 15thDay
11%5%25%435%45%6%45%
2109
16th to endDay
11%424435%447%45%
2229
May1st to 15thDay
10%5%25%5%35%45%8%42%
2331
16th to endDay
7%5%26%6%35%6%6%9%40%
2431
June1st to 15thDay
7%5%25%6%48%7%8%10%33%
2340
16th to endDay
5%4145%36%6%7%11%43%
2340
July1st to 15thDay
9%5%25%7%47%7%7%10%31%
2340
16th to endDay
6%425%7%5%8%8%7%12%29%
2465
August1st to 15thDay
6%425%6%48%8%10%11%32%
2265
16th to endDay
11%6%27%8%5%8%6%6%9%26%
2292
September1st to 15thDay
11%5%26%6%45%6%7%9%35%
2009
16th to endDay
14%5%2433445%6%43%
1894
October1st to 15thDay
11%5%23423445%53%
1815
16th to endDay
12%5%1332333457%
1752
November1st to 15thDay
13%423313235%55%
1582
16th to endDay
14%43432335%6%48%
1620
December1st to 15thDay
17%6%26%42445%5%41%
1620
16th to endDay
22%10%34423435%34%
1728
January1st to 15thNight
17%7%2432345%6%41%
2327
16th to endNight
17%7%34323346%41%
2418
February1st to 15thNight
14%6%14334346%47%
2103
16th to endNight
16%5%35%43435%5%43%
1893
March1st to 15thNight
13%6%3442445%7%44%
2090
16th to endNight
10%6%25%434346%47%
2112
April1st to 15thNight
10%41442335%10%49%
1848
16th to endNight
8%5%243335%5%7%51%
1728
May1st to 15thNight
9%4245%35%5%6%7%45%
1619
16th to endNight
5%414445%5%7%9%47%
1682
June1st to 15thNight
3325%5%25%6%8%11%44%
1620
16th to endNight
3224435%6%6%12%47%
1620
July1st to 15thNight
6%425%5%47%6%8%11%38%
1620
16th to endNight
5%425%5%47%7%8%12%36%
1703
August1st to 15thNight
4425%5%45%5%8%12%41%
1692
16th to endNight
11%5%25%5%25%5%7%10%37%
1910
September1st to 15thNight
9%5%25%6%4447%9%40%
1938
16th to endNight
10%415%42445%7%48%
1903
October1st to 15thNight
10%413323346%56%
1815
16th to endNight
8%5%2342223359%
2118
November1st to 15thNight
10%423323335%57%
2276
16th to endNight
13%5%1442325%5%50%
2340
December1st to 15thNight
14%6%35%424346%42%
2340
16th to endNight
20%8%35%42345%6%35%
2496

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
43%49%15%22%4
1612
16th to endDay
43%36%19%20%5%
1803
February1st to 15thDay
42%48%19%21%2
1752
16th to endDay
44%47%19%19%4
1580
March1st to 15thDay
44%5%9%15%20%4
1869
16th to endDay
43%5%12%20%15%3
2112
April1st to 15thDay
39%5%10%19%19%5%
2109
16th to endDay
36%7%10%20%21%4
2229
May1st to 15thDay
39%7%11%20%17%3
2331
16th to endDay
37%9%15%21%13%3
2435
June1st to 15thDay
42%12%15%20%8%1
2340
16th to endDay
31%9%18%23%14%2
2340
July1st to 15thDay
42%12%18%16%8%1
2201
16th to endDay
41%14%17%16%8%1
2310
August1st to 15thDay
38%14%18%17%9%1
2252
16th to endDay
50%12%12%12%9%1
2292
September1st to 15thDay
42%10%15%14%13%4
2009
16th to endDay
39%6%12%18%18%4
1894
October1st to 15thDay
33%5%8%17%25%9%
1815
16th to endDay
33%36%17%30%10%
1752
November1st to 15thDay
32%26%16%33%8%
1582
16th to endDay
37%47%15%27%6%
1620
December1st to 15thDay
44%49%19%16%5%
1620
16th to endDay
53%39%15%14%4
1728
January1st to 15thNight
41%49%18%21%4
2327
16th to endNight
43%45%19%20%6%
2418
February1st to 15thNight
39%37%20%19%8%
2112
16th to endNight
42%45%20%22%4
1893
March1st to 15thNight
39%5%11%19%17%7%
2090
16th to endNight
38%5%9%25%18%3
2112
April1st to 15thNight
31%5%10%23%22%6%
1848
16th to endNight
31%6%11%23%21%7%
1728
May1st to 15thNight
34%8%14%19%21%2
1620
16th to endNight
30%8%15%26%16%3
1684
June1st to 15thNight
29%11%21%24%11%1
1620
16th to endNight
27%10%21%21%16%3
1620
July1st to 15thNight
32%12%19%20%11%2
1530
16th to endNight
35%12%19%19%10%2
1595
August1st to 15thNight
32%10%18%23%12%1
1681
16th to endNight
39%11%17%16%13%1
1910
September1st to 15thNight
38%10%17%16%13%4
1938
16th to endNight
33%8%10%23%19%5%
1903
October1st to 15thNight
29%5%10%19%26%9%
1815
16th to endNight
31%35%15%31%13%
2118
November1st to 15thNight
30%37%17%29%12%
2276
16th to endNight
35%5%6%18%26%8%
2340
December1st to 15thNight
42%5%8%19%19%5%
2340
16th to endNight
49%5%8%16%17%3
2496

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%21%36%16%31
90
16th to endDay
20%30%41%34
96
February1st to 15thDay
23%21%44%8%2
90
16th to endDay
29%14%39%16%
81
March1st to 15thDay
21%20%32%19%41
159
16th to endDay
16%13%33%23%11%1
288
April1st to 15thDay
17%14%30%20%16%1
270
16th to endDay
13%5%26%29%20%4
270
May1st to 15thDay
11%11%26%23%13%13%
288
16th to endDay
11%419%32%18%14%
331
June1st to 15thDay
10%113%25%24%24%
315
16th to endDay
8%17%23%24%24%
315
July1st to 15thDay
8%39%25%26%27%
305
16th to endDay
9%6%21%36%24%
326
August1st to 15thDay
14%19%25%29%19%
313
16th to endDay
14%18%28%27%18%
332
September1st to 15thDay
13%413%19%28%19%
315
16th to endDay
17%218%23%28%9%
283
October1st to 15thDay
17%323%22%25%7%
255
16th to endDay
17%6%21%22%26%5%
247
November1st to 15thDay
25%13%26%21%11%2
90
16th to endDay
12%12%41%21%10%3
90
December1st to 15thDay
21%20%35%18%4
90
16th to endDay
32%14%33%14%5%
96
January1st to 15thNight
23%18%29%20%7%
720
16th to endNight
21%16%34%24%2
768
February1st to 15thNight
19%17%33%26%2
704
16th to endNight
20%17%37%22%2
631
March1st to 15thNight
18%15%35%23%6%
720
16th to endNight
14%13%30%27%13%
768
April1st to 15thNight
13%12%31%27%12%
590
16th to endNight
11%10%28%32%16%1
540
May1st to 15thNight
10%5%26%31%22%3
540
16th to endNight
7%319%31%32%5%
563
June1st to 15thNight
4111%34%35%12%
540
16th to endNight
418%32%42%10%
540
July1st to 15thNight
7%9%25%44%12%
510
16th to endNight
6%7%27%45%11%
564
August1st to 15thNight
5%7%32%43%9%
539
16th to endNight
12%9%26%41%9%
573
September1st to 15thNight
12%111%27%36%10%
678
16th to endNight
13%217%32%30%3
689
October1st to 15thNight
12%5%23%30%22%5%
660
16th to endNight
10%10%24%29%21%3
704
November1st to 15thNight
12%8%27%26%22%1
700
16th to endNight
15%16%28%26%12%
720
December1st to 15thNight
18%13%34%23%8%
720
16th to endNight
23%16%28%23%7%
768
Page generated at 2017-09-24 09:15:52. Version ac04

Copyright 2017 A. Danko


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