Wally's Corner
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wally's Corner clear sky chart from 2005-11-05 to 2017-09-22.

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
40%
16104
18%
46798
10%
16057
46%
16057
28%
29799

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
32%
900
14%
2560
8%
895
38%
895
22%
1785
January16th to endNight
27%
960
16%
2502
5%
960
34%
960
20%
1828
February1st to 15thNight
30%
879
12%
2288
4%
875
34%
875
22%
1659
February16th to endNight
34%
699
18%
1961
7%
699
42%
699
26%
1299
March1st to 15thNight
33%
588
17%
2028
11%
588
41%
588
23%
1280
March16th to endNight
29%
576
14%
2112
11%
576
35%
576
18%
1401
April1st to 15thNight
33%
539
16%
1814
12%
539
42%
539
23%
1153
April16th to endNight
30%
540
17%
1620
12%
540
40%
540
21%
1124
May1st to 15thNight
38%
540
17%
1620
10%
540
44%
540
29%
1005
May16th to endNight
41%
563
15%
1544
6%
561
46%
561
29%
1004
June1st to 15thNight
48%
540
16%
1317
6%
540
50%
540
36%
847
June16th to endNight
59%
540
21%
1260
8%
540
61%
540
52%
731
July1st to 15thNight
65%
510
19%
1223
6%
510
67%
510
53%
696
July16th to endNight
70%
564
22%
1559
14%
531
72%
531
51%
777
August1st to 15thNight
67%
539
22%
1610
20%
536
70%
536
42%
877
August16th to endNight
62%
573
25%
1719
25%
573
67%
573
42%
922
September1st to 15thNight
60%
540
23%
1894
22%
540
68%
540
38%
982
September16th to endNight
47%
513
27%
1891
18%
513
61%
513
33%
971
October1st to 15thNight
36%
621
27%
1941
17%
621
45%
621
31%
1108
October16th to endNight
36%
745
20%
2153
11%
745
43%
745
29%
1363
November1st to 15thNight
39%
875
24%
2316
11%
875
47%
875
34%
1456
November16th to endNight
34%
900
20%
2520
11%
900
41%
900
28%
1621
December1st to 15thNight
28%
900
11%
2520
4%
900
34%
900
19%
1822
December16th to endNight
27%
960
13%
2826
6%
960
34%
960
16%
2088

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%6%35%5%3445%7%40%
48077
Night
10%6%35%42445%7%45%
46971
Cloud CoverDay
12%6%35%5%3445%7%41%
48087
Night
10%6%35%42445%7%45%
46974
Cloud CoverDay
12%6%35%5%3445%7%41%
48088
Night
10%6%35%42445%7%45%
46975
Cloud CoverDay
12%6%35%5%3445%7%40%
48086
Night
10%6%35%42445%7%45%
46975
TransparencyDay
42%6%15%23%11%1
47768
Night
38%6%14%24%13%1
46798
SeeingDay
15%7%30%29%14%2
6102
Night
13%7%33%33%11%
16105

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
5%10%5%10%8%5%6%5%5%7%28%
1376
16th to endDay
9%12%7%10%6%45%5%47%25%
1719
February1st to 15thDay
11%11%49%8%35%35%6%29%
1575
16th to endDay
9%9%46%5%36%5%6%7%35%
1523
March1st to 15thDay
15%10%45%424448%35%
1921
16th to endDay
17%10%37%5%245%5%6%30%
2112
April1st to 15thDay
16%6%35%42445%7%38%
2130
16th to endDay
24%9%25%424345%32%
2340
May1st to 15thDay
17%6%35%5%3435%6%36%
2331
16th to endDay
18%6%26%5%2445%7%34%
2571
June1st to 15thDay
16%5%34424448%40%
2640
16th to endDay
8%31342446%8%51%
2700
July1st to 15thDay
6%31342346%10%53%
2661
16th to endDay
5%2133345%6%9%54%
2500
August1st to 15thDay
9%425%6%35%6%6%8%41%
2340
16th to endDay
8%425%42335%6%52%
2483
September1st to 15thDay
12%4245%23346%50%
2064
16th to endDay
11%324313346%54%
1881
October1st to 15thDay
13%6%24423335%49%
1678
16th to endDay
15%7%24323336%46%
1716
November1st to 15thDay
8%7%26%42445%7%47%
1541
16th to endDay
13%9%36%435%45%8%36%
1440
December1st to 15thDay
11%12%410%6%45%45%6%29%
1440
16th to endDay
14%9%6%9%9%5%5%5%5%6%23%
1395
January1st to 15thNight
7%7%37%7%45%5%6%8%35%
2560
16th to endNight
8%10%5%8%5%345%5%8%33%
2502
February1st to 15thNight
10%10%48%6%34446%36%
2285
16th to endNight
7%7%36%6%3446%8%41%
1961
March1st to 15thNight
12%7%36%424447%42%
2016
16th to endNight
13%8%47%5%2345%6%37%
2112
April1st to 15thNight
14%6%2443345%6%43%
1814
16th to endNight
19%7%35%5%2335%5%37%
1620
May1st to 15thNight
14%5%24324346%48%
1620
16th to endNight
12%6%245%145%5%7%44%
1542
June1st to 15thNight
10%5%24424448%48%
1317
16th to endNight
5%222225%5%7%61%
1260
July1st to 15thNight
3312323348%64%
1296
16th to endNight
31121346%10%62%
1666
August1st to 15thNight
4212335%46%10%55%
1620
16th to endNight
7%223313347%59%
1719
September1st to 15thNight
8%31432335%6%58%
1894
16th to endNight
8%422223347%56%
1891
October1st to 15thNight
13%423313436%53%
1941
16th to endNight
15%7%24423346%47%
2153
November1st to 15thNight
8%5%25%433446%50%
2316
16th to endNight
10%6%25%434446%46%
2520
December1st to 15thNight
10%11%48%5%345%47%33%
2520
16th to endNight
15%10%48%6%3445%6%29%
2826

Percentage Cloud Cover NW (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
5%10%6%10%8%46%5%48%29%
1377
16th to endDay
8%13%8%8%7%35%5%5%7%25%
1719
February1st to 15thDay
11%10%410%7%45%445%30%
1575
16th to endDay
9%10%36%5%26%46%8%35%
1523
March1st to 15thDay
14%10%5%5%423447%36%
1932
16th to endDay
18%9%46%5%25%45%6%30%
2110
April1st to 15thDay
16%7%245%2445%8%38%
2130
16th to endDay
24%8%25%434345%32%
2340
May1st to 15thDay
17%6%26%5%2446%6%36%
2331
16th to endDay
18%6%36%5%2446%7%34%
2571
June1st to 15thDay
16%5%245%34448%40%
2640
16th to endDay
8%31443446%7%51%
2700
July1st to 15thDay
6%31342446%10%53%
2661
16th to endDay
5%21332446%10%54%
2500
August1st to 15thDay
8%425%5%25%7%7%9%42%
2340
16th to endDay
8%42442345%7%52%
2483
September1st to 15thDay
12%5%145%23346%50%
2064
16th to endDay
11%313323346%55%
1881
October1st to 15thDay
13%6%24323335%49%
1678
16th to endDay
15%7%24422345%47%
1716
November1st to 15thDay
8%6%35%5%2436%7%47%
1541
16th to endDay
12%9%45%435%45%8%36%
1440
December1st to 15thDay
11%11%410%6%3445%6%30%
1440
16th to endDay
14%9%6%10%8%5%5%446%24%
1395
January1st to 15thNight
6%7%47%8%35%5%6%8%35%
2560
16th to endNight
8%9%5%8%5%35%45%8%33%
2502
February1st to 15thNight
10%11%48%5%34346%36%
2278
16th to endNight
6%8%36%6%3446%7%41%
1961
March1st to 15thNight
12%7%37%424346%42%
2028
16th to endNight
13%9%46%5%2436%6%37%
2110
April1st to 15thNight
14%6%244245%5%6%43%
1814
16th to endNight
19%7%36%5%23345%37%
1620
May1st to 15thNight
14%5%2332435%7%48%
1619
16th to endNight
12%6%2442445%8%44%
1543
June1st to 15thNight
9%42432445%8%48%
1317
16th to endNight
5%2122225%5%7%61%
1260
July1st to 15thNight
421131335%7%64%
1296
16th to endNight
31121235%6%10%62%
1666
August1st to 15thNight
4113325%5%5%9%56%
1620
16th to endNight
7%314223447%59%
1719
September1st to 15thNight
8%213323446%59%
1894
16th to endNight
8%413223446%57%
1891
October1st to 15thNight
14%423312336%52%
1941
16th to endNight
15%6%24323346%47%
2153
November1st to 15thNight
8%5%25%424446%50%
2316
16th to endNight
9%6%25%5%34447%46%
2520
December1st to 15thNight
10%10%47%6%25%45%7%33%
2520
16th to endNight
15%10%47%6%4446%6%30%
2826

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
5%11%5%10%8%46%5%5%7%28%
1376
16th to endDay
8%13%7%10%7%45%5%47%25%
1719
February1st to 15thDay
11%10%49%9%45%346%29%
1575
16th to endDay
9%9%46%5%27%5%6%7%34%
1523
March1st to 15thDay
14%10%45%424448%35%
1932
16th to endDay
17%10%37%5%2445%6%30%
2112
April1st to 15thDay
16%6%3442445%8%38%
2130
16th to endDay
24%9%25%424346%32%
2340
May1st to 15thDay
17%6%35%5%3435%6%36%
2331
16th to endDay
18%6%26%5%245%5%7%34%
2571
June1st to 15thDay
16%5%34425%45%8%40%
2640
16th to endDay
8%3134345%6%8%51%
2700
July1st to 15thDay
6%31332446%9%53%
2661
16th to endDay
5%2133345%6%9%54%
2500
August1st to 15thDay
8%425%5%35%6%6%9%41%
2340
16th to endDay
8%42442435%6%52%
2483
September1st to 15thDay
12%4245%23345%50%
2064
16th to endDay
11%323313346%55%
1881
October1st to 15thDay
13%6%24433336%48%
1678
16th to endDay
15%7%24422346%46%
1716
November1st to 15thDay
8%7%26%5%1435%7%47%
1541
16th to endDay
12%9%36%435%45%8%36%
1440
December1st to 15thDay
11%11%5%9%7%35%45%6%29%
1440
16th to endDay
14%9%6%9%9%5%5%45%6%23%
1395
January1st to 15thNight
7%7%47%7%45%5%6%8%35%
2560
16th to endNight
8%10%5%8%5%345%5%8%33%
2502
February1st to 15thNight
11%10%48%6%33446%36%
2278
16th to endNight
7%7%36%6%3446%7%41%
1961
March1st to 15thNight
12%7%36%424447%42%
2028
16th to endNight
13%9%46%5%2345%6%37%
2112
April1st to 15thNight
14%6%244335%5%6%43%
1814
16th to endNight
19%7%45%5%23345%37%
1620
May1st to 15thNight
14%5%24324347%47%
1619
16th to endNight
12%6%2441446%7%44%
1542
June1st to 15thNight
10%5%24424449%48%
1317
16th to endNight
5%223135%5%6%61%
1260
July1st to 15thNight
3312322447%64%
1296
16th to endNight
31121346%10%62%
1666
August1st to 15thNight
421233446%10%55%
1620
16th to endNight
7%213313347%59%
1719
September1st to 15thNight
8%314323346%58%
1894
16th to endNight
8%413224347%56%
1891
October1st to 15thNight
13%5%33313436%52%
1941
16th to endNight
15%7%23423346%47%
2153
November1st to 15thNight
8%5%25%424446%50%
2316
16th to endNight
10%6%25%434446%46%
2520
December1st to 15thNight
10%11%48%5%25%5%47%33%
2520
16th to endNight
15%10%48%6%3445%6%29%
2826

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
5%10%6%11%7%5%6%5%5%7%29%
1376
16th to endDay
8%13%7%10%7%36%5%47%26%
1719
February1st to 15thDay
11%10%49%8%35%5%46%29%
1575
16th to endDay
9%9%46%5%36%5%6%8%34%
1523
March1st to 15thDay
15%10%45%424448%35%
1932
16th to endDay
17%10%47%6%245%5%6%30%
2110
April1st to 15thDay
16%7%25%42445%7%38%
2130
16th to endDay
24%9%25%424345%32%
2340
May1st to 15thDay
18%7%25%5%3445%6%37%
2331
16th to endDay
18%6%26%5%2446%7%34%
2571
June1st to 15thDay
16%6%24334448%39%
2640
16th to endDay
8%3144245%6%8%51%
2700
July1st to 15thDay
6%31332446%10%53%
2661
16th to endDay
5%2133345%6%10%54%
2500
August1st to 15thDay
8%415%5%45%6%7%8%41%
2340
16th to endDay
8%42442335%7%51%
2483
September1st to 15thDay
12%5%24423346%50%
2064
16th to endDay
12%423323347%54%
1881
October1st to 15thDay
14%6%24423345%49%
1678
16th to endDay
15%7%24422336%46%
1716
November1st to 15thDay
8%6%26%5%23448%47%
1541
16th to endDay
13%8%36%435%45%8%36%
1440
December1st to 15thDay
11%11%5%9%6%45%45%6%29%
1440
16th to endDay
14%9%5%9%9%5%5%5%5%6%23%
1395
January1st to 15thNight
7%7%47%8%45%5%6%8%35%
2560
16th to endNight
8%10%5%8%5%345%5%9%33%
2502
February1st to 15thNight
10%10%47%6%33346%36%
2278
16th to endNight
7%7%36%6%345%6%8%40%
1961
March1st to 15thNight
12%7%45%42345%7%42%
2028
16th to endNight
14%8%46%5%235%5%6%37%
2112
April1st to 15thNight
14%6%2442345%6%43%
1814
16th to endNight
19%7%36%423346%37%
1620
May1st to 15thNight
14%5%2331435%7%47%
1619
16th to endNight
13%5%2442446%8%44%
1542
June1st to 15thNight
10%5%23424448%48%
1317
16th to endNight
5%2122135%5%7%61%
1260
July1st to 15thNight
3212323348%64%
1296
16th to endNight
3112135%6%9%62%
1666
August1st to 15thNight
4213335%45%10%55%
1620
16th to endNight
7%31321335%6%59%
1719
September1st to 15thNight
8%314323446%58%
1894
16th to endNight
8%423223347%56%
1891
October1st to 15thNight
14%433313336%53%
1941
16th to endNight
15%7%24423336%47%
2153
November1st to 15thNight
8%5%25%434446%50%
2316
16th to endNight
10%6%25%434447%45%
2520
December1st to 15thNight
10%11%48%6%35%5%47%32%
2520
16th to endNight
15%10%48%7%3445%6%29%
2826

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
53%5%14%18%8%
1377
16th to endDay
57%7%14%16%4
1719
February1st to 15thDay
55%5%14%18%6%
1576
16th to endDay
46%8%16%17%10%
1523
March1st to 15thDay
47%7%14%23%6%
1932
16th to endDay
53%7%13%20%4
2112
April1st to 15thDay
43%6%14%25%8%1
2130
16th to endDay
53%5%12%19%8%
2340
May1st to 15thDay
46%7%13%20%10%
2331
16th to endDay
47%7%13%20%10%
2575
June1st to 15thDay
42%8%14%23%9%1
2640
16th to endDay
29%8%17%28%14%3
2700
July1st to 15thDay
26%6%18%30%14%3
2505
16th to endDay
24%7%18%28%18%2
2344
August1st to 15thDay
36%9%17%23%11%1
2326
16th to endDay
31%5%14%30%14%3
2483
September1st to 15thDay
35%6%13%27%16%1
2064
16th to endDay
30%5%13%33%16%
1881
October1st to 15thDay
37%5%12%25%17%1
1678
16th to endDay
39%416%25%12%
1716
November1st to 15thDay
36%415%24%18%1
1541
16th to endDay
45%6%17%20%9%
1440
December1st to 15thDay
54%5%15%16%7%
1440
16th to endDay
60%5%12%14%6%1
1395
January1st to 15thNight
45%7%14%21%11%
2560
16th to endNight
47%8%16%19%7%
2502
February1st to 15thNight
49%5%13%21%9%
2288
16th to endNight
39%7%14%22%12%2
1961
March1st to 15thNight
41%5%16%25%8%1
2028
16th to endNight
46%6%14%24%7%
2112
April1st to 15thNight
40%7%14%25%12%
1814
16th to endNight
47%6%11%21%11%1
1620
May1st to 15thNight
36%5%14%25%15%2
1620
16th to endNight
37%8%15%23%14%
1544
June1st to 15thNight
33%6%17%26%14%1
1317
16th to endNight
20%6%15%28%25%3
1260
July1st to 15thNight
20%5%17%32%19%4
1223
16th to endNight
16%7%17%31%21%4
1559
August1st to 15thNight
23%7%15%31%18%1
1610
16th to endNight
25%5%15%28%19%5%
1719
September1st to 15thNight
25%5%14%30%20%2
1894
16th to endNight
26%6%12%33%19%1
1891
October1st to 15thNight
33%412%26%20%2
1941
16th to endNight
38%414%26%14%1
2153
November1st to 15thNight
34%413%23%20%2
2316
16th to endNight
38%5%17%25%12%
2520
December1st to 15thNight
49%6%16%19%7%
2520
16th to endNight
54%6%13%16%8%
2826

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
12%12%45%23%6%
90
16th to endDay
26%5%35%25%8%
96
February1st to 15thDay
18%18%36%21%4
90
16th to endDay
13%16%35%23%9%1
81
March1st to 15thDay
24%15%33%25%1
90
16th to endDay
21%6%40%15%13%2
96
April1st to 15thDay
20%12%33%26%6%1
249
16th to endDay
30%14%28%17%7%2
450
May1st to 15thDay
21%10%30%26%10%1
468
16th to endDay
21%8%30%26%10%2
517
June1st to 15thDay
14%8%28%28%16%3
495
16th to endDay
6%6%36%34%14%1
495
July1st to 15thDay
7%326%38%19%4
475
16th to endDay
5%226%42%20%2
515
August1st to 15thDay
8%223%37%24%3
493
16th to endDay
10%326%31%23%4
523
September1st to 15thDay
11%5%28%31%18%5%
219
16th to endDay
17%6%29%26%15%3
108
October1st to 15thDay
14%7%35%31%6%4
90
16th to endDay
16%9%39%22%11%
96
November1st to 15thDay
38%24%44%15%3
90
16th to endDay
44%7%24%14%8%
90
December1st to 15thDay
21%15%41%12%10%
90
16th to endDay
22%22%33%19%1
96
January1st to 15thNight
10%10%38%31%7%1
900
16th to endNight
12%11%39%30%5%
960
February1st to 15thNight
16%9%36%28%7%1
880
16th to endNight
10%8%39%29%10%1
699
March1st to 15thNight
15%8%36%31%7%
588
16th to endNight
16%10%36%27%8%
576
April1st to 15thNight
18%10%33%32%5%
539
16th to endNight
22%11%32%23%8%1
540
May1st to 15thNight
18%6%34%30%8%
540
16th to endNight
16%5%31%35%10%
563
June1st to 15thNight
12%6%28%37%14%
540
16th to endNight
5%328%49%12%
540
July1st to 15thNight
5%23%46%22%
510
16th to endNight
322%51%20%
564
August1st to 15thNight
4120%47%25%
539
16th to endNight
8%322%39%24%2
573
September1st to 15thNight
9%225%40%17%3
540
16th to endNight
10%6%32%32%15%2
513
October1st to 15thNight
14%9%36%28%9%
621
16th to endNight
20%6%31%32%8%
745
November1st to 15thNight
12%9%34%33%9%
875
16th to endNight
13%10%38%28%9%
900
December1st to 15thNight
16%10%35%32%4
900
16th to endNight
20%8%33%28%8%
960
Page generated at 2017-09-23 05:43:47. Version ac04

Copyright 2017 A. Danko


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