Galena
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Galena clear sky chart from 2005-11-05 to 2018-01-20.

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
29%
16574
18%
48493
9%
16529
38%
16529
21%
31844

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
20%
975
13%
2716
4%
970
29%
970
16%
1963
January16th to endNight
15%
985
12%
2652
2%
985
23%
985
13%
1990
February1st to 15thNight
18%
878
14%
2288
3%
876
26%
876
16%
1636
February16th to endNight
21%
639
19%
1901
7%
639
32%
639
15%
1308
March1st to 15thNight
21%
672
16%
2112
7%
672
30%
672
16%
1390
March16th to endNight
20%
576
14%
2028
7%
576
29%
576
14%
1391
April1st to 15thNight
20%
539
17%
1797
8%
539
33%
539
16%
1183
April16th to endNight
25%
540
19%
1800
8%
540
39%
540
15%
1209
May1st to 15thNight
25%
540
17%
1483
6%
540
36%
540
21%
1042
May16th to endNight
31%
563
19%
1497
5%
561
43%
561
27%
939
June1st to 15thNight
35%
540
16%
1440
5%
540
42%
540
29%
893
June16th to endNight
36%
540
17%
1440
6%
540
42%
540
27%
920
July1st to 15thNight
57%
510
19%
1360
10%
510
60%
510
40%
774
July16th to endNight
52%
564
24%
1417
14%
531
61%
531
42%
795
August1st to 15thNight
62%
539
23%
1575
19%
536
67%
536
38%
864
August16th to endNight
56%
573
21%
1910
21%
573
62%
573
33%
1059
September1st to 15thNight
54%
540
28%
1800
25%
540
63%
540
36%
921
September16th to endNight
50%
657
28%
1935
18%
657
60%
657
33%
1100
October1st to 15thNight
35%
720
24%
2160
14%
720
43%
720
27%
1309
October16th to endNight
26%
768
20%
2373
9%
768
38%
768
21%
1517
November1st to 15thNight
26%
760
23%
2471
14%
760
37%
760
21%
1496
November16th to endNight
19%
941
18%
2696
7%
941
30%
941
18%
1804
December1st to 15thNight
16%
975
12%
2730
3%
975
24%
975
12%
2048
December16th to endNight
14%
1040
12%
2912
2%
1040
23%
1040
10%
2293

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
14%8%36%5%3445%7%37%
49044
Night
13%8%35%5%24446%40%
48661
Cloud CoverDay
14%8%36%5%2445%7%37%
49054
Night
13%8%35%5%24446%40%
48666
Cloud CoverDay
14%8%36%5%3445%7%37%
49052
Night
13%8%35%5%24446%40%
48666
TransparencyDay
46%412%23%11%1
48729
Night
44%312%23%14%1
48494
SeeingDay
16%20%28%20%10%3
6415
Night
15%24%25%23%9%1
16576

By Month

Percentage Cloud Cover NE (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%12%6%8%6%36%5%47%28%
1552
16th to endDay
12%13%6%11%6%34346%26%
1676
February1st to 15thDay
14%14%5%6%6%24346%30%
1575
16th to endDay
14%10%36%7%3434435%
1572
March1st to 15thDay
16%10%35%42345%7%35%
1847
16th to endDay
17%11%45%5%2445%7%31%
2196
April1st to 15thDay
18%9%5%6%5%24447%30%
2151
16th to endDay
22%9%35%5%2434434%
2160
May1st to 15thDay
19%9%36%5%245%6%7%28%
2466
16th to endDay
14%7%36%5%35%45%7%35%
2617
June1st to 15thDay
13%6%26%6%35%35%7%38%
2520
16th to endDay
10%5%25%435%6%6%8%40%
2520
July1st to 15thDay
7%5%145%25%5%7%9%45%
2520
16th to endDay
7%425%6%35%5%7%10%39%
2655
August1st to 15thDay
6%5%25%6%45%6%6%9%41%
2373
16th to endDay
12%5%25%43445%7%44%
2292
September1st to 15thDay
12%413433346%50%
2160
16th to endDay
11%6%25%42345%7%46%
2010
October1st to 15thDay
17%6%345%23335%44%
1800
16th to endDay
18%7%25%423446%40%
1849
November1st to 15thDay
14%7%36%424445%40%
1717
16th to endDay
17%10%46%323235%41%
1592
December1st to 15thDay
18%13%39%5%34435%29%
1560
16th to endDay
19%17%5%9%5%23436%23%
1664
January1st to 15thNight
12%10%5%7%6%34435%33%
2716
16th to endNight
12%12%5%10%6%34445%29%
2652
February1st to 15thNight
11%10%5%8%5%3434436%
2285
16th to endNight
13%10%47%433445%37%
1901
March1st to 15thNight
16%9%44424345%39%
2099
16th to endNight
18%9%46%5%24437%32%
2028
April1st to 15thNight
18%8%35%424446%37%
1797
16th to endNight
19%10%25%424345%37%
1800
May1st to 15thNight
18%6%35%425%46%8%34%
1483
16th to endNight
9%5%244345%6%10%42%
1496
June1st to 15thNight
11%5%23325%5%5%9%45%
1440
16th to endNight
9%5%245%35%5%6%9%42%
1440
July1st to 15thNight
6%31222446%9%55%
1440
16th to endNight
6%2135%2445%10%53%
1513
August1st to 15thNight
43235%2445%9%53%
1584
16th to endNight
8%425%423347%53%
1910
September1st to 15thNight
8%314323247%58%
1800
16th to endNight
7%4135%2445%8%51%
1935
October1st to 15thNight
13%5%24423345%48%
2160
16th to endNight
16%8%25%423345%43%
2373
November1st to 15thNight
13%6%245%23336%47%
2471
16th to endNight
18%7%25%5%23346%39%
2696
December1st to 15thNight
18%11%48%6%34335%29%
2730
16th to endNight
20%12%6%8%5%2444424%
2912

Percentage Cloud Cover SW (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%11%7%7%6%35%5%47%28%
1552
16th to endDay
12%13%6%11%6%34446%26%
1676
February1st to 15thDay
13%15%5%6%6%25%336%30%
1575
16th to endDay
14%11%36%7%34345%35%
1572
March1st to 15thDay
17%9%35%5%23447%35%
1857
16th to endDay
18%11%45%5%3445%7%30%
2196
April1st to 15thDay
17%10%5%7%5%2445%6%30%
2151
16th to endDay
22%9%35%5%2434434%
2160
May1st to 15thDay
18%10%36%5%25%5%5%7%28%
2466
16th to endDay
14%7%36%5%35%45%7%35%
2617
June1st to 15thDay
13%6%26%5%35%45%7%38%
2520
16th to endDay
10%5%35%5%35%6%6%8%40%
2520
July1st to 15thDay
7%4145%25%5%7%10%45%
2520
16th to endDay
7%5%25%6%25%5%7%10%39%
2655
August1st to 15thDay
6%5%25%6%45%5%6%8%41%
2373
16th to endDay
12%5%245%25%45%8%44%
2292
September1st to 15thDay
13%41342335%6%49%
2160
16th to endDay
11%6%25%423447%46%
2010
October1st to 15thDay
17%6%345%23245%44%
1800
16th to endDay
18%8%25%323446%40%
1849
November1st to 15thDay
13%8%36%4245%46%39%
1717
16th to endDay
16%10%46%422335%41%
1592
December1st to 15thDay
18%13%39%5%3433429%
1560
16th to endDay
19%18%5%9%5%23436%23%
1664
January1st to 15thNight
12%11%5%7%6%44435%33%
2716
16th to endNight
12%12%5%10%6%34445%29%
2652
February1st to 15thNight
11%10%5%8%6%34345%36%
2278
16th to endNight
13%10%46%433445%37%
1901
March1st to 15thNight
16%9%44424335%39%
2112
16th to endNight
17%9%46%5%24447%32%
2028
April1st to 15thNight
18%9%35%424446%37%
1797
16th to endNight
20%9%25%5%24345%37%
1800
May1st to 15thNight
17%7%25%425%46%9%34%
1482
16th to endNight
9%5%25%4345%6%10%42%
1496
June1st to 15thNight
11%5%2332445%9%45%
1440
16th to endNight
9%5%145%35%5%6%9%42%
1440
July1st to 15thNight
6%31232446%10%54%
1440
16th to endNight
6%2134245%5%10%53%
1513
August1st to 15thNight
5%3235%2445%9%53%
1584
16th to endNight
8%425%424337%53%
1910
September1st to 15thNight
8%313323347%58%
1800
16th to endNight
8%3235%2445%8%51%
1935
October1st to 15thNight
13%5%15%423346%48%
2160
16th to endNight
16%8%25%424345%42%
2373
November1st to 15thNight
13%6%25%5%23346%47%
2471
16th to endNight
17%7%25%5%23446%39%
2696
December1st to 15thNight
18%12%48%6%25%345%29%
2730
16th to endNight
20%13%6%8%5%34435%24%
2912

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%11%7%7%6%36%446%29%
1552
16th to endDay
13%13%6%11%5%34446%25%
1676
February1st to 15thDay
13%15%5%7%6%25%345%30%
1575
16th to endDay
15%9%36%7%34335%35%
1572
March1st to 15thDay
16%10%45%42345%7%35%
1857
16th to endDay
18%10%5%5%5%3435%7%30%
2194
April1st to 15thDay
17%10%47%5%3445%6%30%
2151
16th to endDay
22%9%35%5%23345%34%
2160
May1st to 15thDay
19%9%36%5%35%46%7%28%
2466
16th to endDay
15%6%36%5%35%45%7%35%
2617
June1st to 15thDay
13%6%25%6%35%5%5%7%38%
2520
16th to endDay
10%5%25%5%346%6%8%41%
2520
July1st to 15thDay
7%4145%345%7%10%45%
2520
16th to endDay
7%5%25%5%35%5%6%10%40%
2655
August1st to 15thDay
6%5%246%46%5%7%8%40%
2373
16th to endDay
12%5%245%345%5%6%44%
2292
September1st to 15thDay
13%413424347%49%
2160
16th to endDay
12%6%25%42335%7%47%
2010
October1st to 15thDay
17%7%245%23335%44%
1800
16th to endDay
19%7%25%322445%40%
1849
November1st to 15thDay
13%9%36%5%24446%39%
1717
16th to endDay
15%11%46%413335%40%
1592
December1st to 15thDay
18%13%39%5%34435%29%
1560
16th to endDay
19%17%6%8%5%235%35%23%
1664
January1st to 15thNight
12%12%5%7%6%34445%33%
2716
16th to endNight
11%12%6%9%7%35%445%29%
2652
February1st to 15thNight
11%11%5%8%6%34335%36%
2278
16th to endNight
13%11%46%434436%36%
1901
March1st to 15thNight
16%10%35%434335%39%
2112
16th to endNight
18%9%36%6%33446%32%
2028
April1st to 15thNight
18%8%35%5%14346%37%
1797
16th to endNight
20%8%25%424345%37%
1800
May1st to 15thNight
17%7%35%335%46%8%34%
1482
16th to endNight
9%5%25%4245%7%10%42%
1496
June1st to 15thNight
12%5%233345%5%9%46%
1440
16th to endNight
9%5%24435%5%7%8%43%
1440
July1st to 15thNight
6%2133235%6%10%54%
1440
16th to endNight
6%2144335%6%9%53%
1513
August1st to 15thNight
5%3235%2445%9%53%
1584
16th to endNight
9%4245%23336%53%
1910
September1st to 15thNight
8%313323337%58%
1800
16th to endNight
8%4134345%5%8%51%
1935
October1st to 15thNight
13%6%24423346%47%
2160
16th to endNight
16%8%25%422345%42%
2373
November1st to 15thNight
12%7%25%5%24245%47%
2471
16th to endNight
17%7%35%5%2435%5%39%
2696
December1st to 15thNight
18%12%48%6%34345%29%
2730
16th to endNight
20%13%6%8%5%35%44424%
2912

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
54%414%17%9%
1553
16th to endDay
58%314%16%6%
1676
February1st to 15thDay
56%212%20%7%
1576
16th to endDay
51%410%23%8%1
1572
March1st to 15thDay
48%316%20%9%
1857
16th to endDay
53%412%22%6%1
2196
April1st to 15thDay
53%310%22%9%
2151
16th to endDay
53%39%20%11%1
2160
May1st to 15thDay
53%412%20%8%
2466
16th to endDay
47%5%10%20%13%1
2621
June1st to 15thDay
43%5%11%23%15%
2520
16th to endDay
38%6%13%25%14%1
2520
July1st to 15thDay
33%5%16%27%14%2
2371
16th to endDay
36%6%16%24%13%2
2488
August1st to 15thDay
37%5%13%27%14%1
2358
16th to endDay
38%412%27%14%2
2292
September1st to 15thDay
34%38%32%18%1
2160
16th to endDay
37%311%31%15%
2010
October1st to 15thDay
43%210%25%16%
1800
16th to endDay
45%313%25%11%
1849
November1st to 15thDay
45%311%25%11%1
1717
16th to endDay
47%318%23%5%
1592
December1st to 15thDay
58%313%16%6%
1560
16th to endDay
63%312%12%7%
1664
January1st to 15thNight
52%311%18%12%
2716
16th to endNight
56%314%16%8%
2652
February1st to 15thNight
50%312%22%10%
2288
16th to endNight
48%412%23%9%2
1901
March1st to 15thNight
47%213%21%12%1
2112
16th to endNight
52%314%21%7%1
2028
April1st to 15thNight
47%210%23%13%2
1797
16th to endNight
49%29%20%13%3
1800
May1st to 15thNight
46%5%13%22%11%
1483
16th to endNight
35%5%14%25%16%2
1498
June1st to 15thNight
34%413%25%19%1
1440
16th to endNight
36%5%12%22%19%4
1440
July1st to 15thNight
25%413%33%18%3
1360
16th to endNight
25%417%30%19%2
1417
August1st to 15thNight
28%413%32%19%2
1575
16th to endNight
32%312%29%17%4
1910
September1st to 15thNight
27%29%30%27%1
1800
16th to endNight
30%410%33%18%2
1935
October1st to 15thNight
38%210%25%21%2
2160
16th to endNight
43%212%24%14%1
2373
November1st to 15thNight
39%311%25%17%3
2471
16th to endNight
46%213%26%10%
2696
December1st to 15thNight
57%211%19%7%
2730
16th to endNight
63%311%13%6%
2912

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
20%24%34%15%5%
135
16th to endDay
24%14%34%14%10%
109
February1st to 15thDay
21%33%28%12%4
90
16th to endDay
24%24%32%11%6%1
81
March1st to 15thDay
28%26%33%8%2
90
16th to endDay
27%22%25%15%6%2
180
April1st to 15thDay
22%27%24%19%5%
270
16th to endDay
25%24%23%15%8%1
270
May1st to 15thDay
19%29%27%16%41
429
16th to endDay
17%28%24%19%6%2
517
June1st to 15thDay
12%20%35%20%8%2
495
16th to endDay
10%23%35%18%8%4
495
July1st to 15thDay
7%12%30%26%14%8%
475
16th to endDay
8%17%28%25%14%6%
515
August1st to 15thDay
8%10%23%28%22%6%
493
16th to endDay
14%10%21%25%17%9%
332
September1st to 15thDay
9%10%25%28%18%7%
315
16th to endDay
12%13%23%26%19%4
296
October1st to 15thDay
22%17%32%15%8%2
135
16th to endDay
25%19%35%16%2
144
November1st to 15thDay
17%20%25%23%8%3
135
16th to endDay
32%19%35%8%4
135
December1st to 15thDay
22%26%31%14%2
135
16th to endDay
27%27%36%9%
144
January1st to 15thNight
14%30%27%19%6%
975
16th to endNight
16%28%29%20%3
985
February1st to 15thNight
16%31%26%19%5%
880
16th to endNight
17%30%26%19%5%
639
March1st to 15thNight
18%29%25%19%6%
672
16th to endNight
17%29%27%18%6%
576
April1st to 15thNight
20%30%25%20%3
539
16th to endNight
22%25%23%21%6%
540
May1st to 15thNight
17%25%28%21%6%
540
16th to endNight
10%23%29%26%9%
563
June1st to 15thNight
13%21%25%30%9%
540
16th to endNight
11%21%28%27%11%
540
July1st to 15thNight
8%13%17%35%21%3
510
16th to endNight
6%17%20%32%22%1
564
August1st to 15thNight
412%12%39%28%2
539
16th to endNight
11%10%16%32%23%4
573
September1st to 15thNight
8%12%20%32%21%5%
540
16th to endNight
9%15%19%32%20%2
657
October1st to 15thNight
16%16%27%23%15%1
720
16th to endNight
18%22%28%22%7%
768
November1st to 15thNight
15%27%26%21%8%
760
16th to endNight
17%31%28%15%6%
941
December1st to 15thNight
22%31%25%16%3
975
16th to endNight
22%28%26%18%3
1040
Page generated at 2018-01-21 11:19:27. Version ac04

Copyright 2018 A. Danko


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