Wallace
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wallace clear sky chart from 2005-11-05 to 2017-04-02.

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
20%
14550
12%
45130
4%
14505
27%
14505
14%
32865

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
11%
750
11%
2506
1%
746
22%
746
9%
1857
January16th to endNight
14%
779
14%
2562
3%
779
27%
779
11%
1859
February1st to 15thNight
14%
704
9%
2286
2%
701
22%
701
11%
1719
February16th to endNight
16%
631
9%
2028
3%
631
23%
631
10%
1548
March1st to 15thNight
17%
719
14%
2010
5%
719
25%
719
13%
1560
March16th to endNight
19%
756
13%
2100
5%
756
26%
756
15%
1603
April1st to 15thNight
19%
500
13%
1665
7%
500
26%
500
13%
1223
April16th to endNight
25%
495
15%
1503
8%
495
31%
495
17%
1063
May1st to 15thNight
22%
495
11%
1361
5%
495
26%
495
16%
1015
May16th to endNight
21%
513
10%
1368
2%
512
27%
512
20%
1004
June1st to 15thNight
23%
465
7%
1290
3%
465
25%
465
17%
977
June16th to endNight
31%
330
7%
1155
3%
330
36%
330
17%
791
July1st to 15thNight
33%
358
11%
1133
6%
358
39%
358
29%
699
July16th to endNight
29%
523
8%
1307
4%
490
33%
490
20%
955
August1st to 15thNight
33%
494
11%
1473
5%
490
36%
490
22%
1015
August16th to endNight
37%
525
13%
1638
7%
525
43%
525
24%
1059
September1st to 15thNight
29%
495
16%
1650
10%
495
38%
495
24%
1039
September16th to endNight
28%
621
21%
1828
12%
621
37%
621
26%
1159
October1st to 15thNight
24%
660
18%
1980
8%
660
33%
660
21%
1326
October16th to endNight
13%
707
12%
2131
2%
707
21%
707
11%
1586
November1st to 15thNight
17%
730
10%
2428
5%
730
23%
730
13%
1791
November16th to endNight
17%
750
10%
2520
4%
750
24%
750
9%
1903
December1st to 15thNight
8%
750
10%
2520
0%
750
18%
750
7%
1945
December16th to endNight
7%
800
7%
2688
1%
800
14%
800
6%
2169

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
19%9%46%5%3445%6%29%
46000
Night
19%10%46%6%35%446%28%
45297
TransparencyDay
55%412%19%7%
45686
Night
55%312%19%7%
45130
SeeingDay
25%16%31%18%6%
6853
Night
26%16%31%19%5%
14551

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
14%13%7%6%7%445%36%25%
1432
16th to endDay
12%11%5%9%7%45%45%6%28%
1659
February1st to 15thDay
16%12%5%7%6%45%445%27%
1575
16th to endDay
14%13%5%9%6%25%45%7%24%
1444
March1st to 15thDay
15%11%5%8%7%45%45%425%
1939
16th to endDay
15%15%7%8%6%2333429%
2124
April1st to 15thDay
18%11%46%6%35%346%28%
1986
16th to endDay
23%9%244335%46%32%
2126
May1st to 15thDay
21%8%36%5%345%6%5%28%
2261
16th to endDay
24%8%35%5%3435%6%29%
2394
June1st to 15thDay
29%7%45%6%3345%6%23%
2348
16th to endDay
23%6%35%6%2445%7%30%
2475
July1st to 15thDay
13%5%35%5%35%45%9%37%
2409
16th to endDay
17%8%36%6%35%5%5%7%30%
2456
August1st to 15thDay
16%6%36%5%36%46%8%32%
2145
16th to endDay
15%5%244235%6%8%42%
2211
September1st to 15thDay
21%5%245%2346%7%36%
1980
16th to endDay
17%6%24433347%41%
1800
October1st to 15thDay
21%8%25%5%24347%33%
1650
16th to endDay
22%12%47%6%345%46%22%
1741
November1st to 15thDay
23%12%46%5%33445%26%
1429
16th to endDay
15%14%6%8%6%445%5%8%20%
1440
December1st to 15thDay
20%16%6%8%6%35%5%45%16%
1440
16th to endDay
22%17%5%9%7%33435%16%
1536
January1st to 15thNight
16%13%6%7%6%35%44426%
2506
16th to endNight
14%11%5%8%7%35%345%29%
2562
February1st to 15thNight
18%13%47%7%35%45%5%25%
2285
16th to endNight
15%15%6%7%6%35%5%4423%
2028
March1st to 15thNight
18%11%5%9%6%35%5%45%25%
1998
16th to endNight
18%14%6%7%5%34435%28%
2100
April1st to 15thNight
21%13%46%42443428%
1665
16th to endNight
24%10%33414436%32%
1503
May1st to 15thNight
24%7%25%5%26%446%29%
1361
16th to endNight
20%8%26%5%35%45%9%29%
1366
June1st to 15thNight
25%8%37%5%14438%26%
1290
16th to endNight
20%6%25%4346%5%7%32%
1155
July1st to 15thNight
11%6%243245%8%9%39%
1207
16th to endNight
15%7%36%7%36%5%6%9%29%
1403
August1st to 15thNight
18%7%25%5%35%5%5%6%33%
1485
16th to endNight
17%5%25%42445%8%37%
1638
September1st to 15thNight
18%43432345%8%38%
1650
16th to endNight
16%6%1442445%5%43%
1828
October1st to 15thNight
19%5%25%5%3446%6%35%
1980
16th to endNight
27%10%36%6%24335%26%
2131
November1st to 15thNight
21%12%36%7%35%435%26%
2428
16th to endNight
20%15%46%5%35%446%24%
2520
December1st to 15thNight
21%14%47%7%35%45%6%19%
2520
16th to endNight
24%17%5%8%7%24335%16%
2688

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
60%412%14%8%
1433
16th to endDay
58%38%17%11%
1659
February1st to 15thDay
60%211%18%6%
1578
16th to endDay
59%312%16%7%1
1444
March1st to 15thDay
61%38%17%7%
1950
16th to endDay
60%29%17%7%1
2124
April1st to 15thDay
58%36%16%12%2
1986
16th to endDay
53%49%19%12%1
2126
May1st to 15thDay
56%5%9%18%8%
2261
16th to endDay
55%5%12%20%6%
2398
June1st to 15thDay
61%312%16%5%
2348
16th to endDay
54%313%20%6%
2475
July1st to 15thDay
42%5%16%25%9%
2256
16th to endDay
52%5%15%21%4
2289
August1st to 15thDay
49%5%13%22%7%
2132
16th to endDay
39%5%18%28%8%
2211
September1st to 15thDay
46%414%23%10%
1980
16th to endDay
43%310%30%11%
1800
October1st to 15thDay
50%411%24%9%
1650
16th to endDay
61%311%17%5%
1741
November1st to 15thDay
59%312%17%7%
1429
16th to endDay
59%5%13%15%6%
1440
December1st to 15thDay
66%211%16%2
1440
16th to endDay
69%29%12%5%
1536
January1st to 15thNight
59%311%16%7%
2506
16th to endNight
57%311%21%7%
2562
February1st to 15thNight
61%310%14%9%
2286
16th to endNight
63%210%14%7%
2028
March1st to 15thNight
61%38%17%8%
2010
16th to endNight
59%28%19%9%1
2100
April1st to 15thNight
58%37%17%11%1
1665
16th to endNight
52%39%18%14%1
1503
May1st to 15thNight
56%311%19%7%1
1361
16th to endNight
52%415%20%6%
1368
June1st to 15thNight
56%413%18%5%
1290
16th to endNight
48%7%15%21%6%
1155
July1st to 15thNight
36%6%21%26%7%
1133
16th to endNight
50%6%16%18%6%
1307
August1st to 15thNight
48%417%23%5%
1473
16th to endNight
43%419%26%6%
1638
September1st to 15thNight
42%414%28%9%
1650
16th to endNight
41%314%29%10%
1828
October1st to 15thNight
45%312%27%9%
1980
16th to endNight
58%29%20%7%
2131
November1st to 15thNight
58%314%16%6%
2428
16th to endNight
60%413%17%4
2520
December1st to 15thNight
62%411%18%3
2520
16th to endNight
69%28%14%4
2688

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%27%31%16%3
240
16th to endDay
19%25%37%14%3
256
February1st to 15thDay
25%21%31%17%2
236
16th to endDay
23%19%30%19%6%
212
March1st to 15thDay
21%25%32%16%3
266
16th to endDay
26%25%27%16%4
288
April1st to 15thDay
26%27%29%10%4
214
16th to endDay
20%21%31%17%7%
210
May1st to 15thDay
29%15%26%16%9%2
352
16th to endDay
30%13%33%17%3
439
June1st to 15thDay
36%10%25%20%6%
420
16th to endDay
29%8%28%22%7%2
420
July1st to 15thDay
17%8%37%25%10%1
400
16th to endDay
23%7%32%24%11%
443
August1st to 15thDay
22%334%27%9%1
253
16th to endDay
16%6%34%26%12%3
268
September1st to 15thDay
23%9%32%26%7%
255
16th to endDay
19%13%36%24%5%
245
October1st to 15thDay
24%14%32%16%11%1
225
16th to endDay
27%26%28%11%5%
240
November1st to 15thDay
33%17%25%14%5%2
235
16th to endDay
31%21%28%12%5%
240
December1st to 15thDay
35%22%30%11%
240
16th to endDay
30%26%29%10%1
256
January1st to 15thNight
24%24%32%15%2
750
16th to endNight
23%22%33%15%3
779
February1st to 15thNight
27%17%34%18%1
704
16th to endNight
24%21%30%18%5%
631
March1st to 15thNight
23%21%30%20%3
720
16th to endNight
27%17%28%17%7%
756
April1st to 15thNight
29%18%27%17%6%
500
16th to endNight
30%12%29%22%5%
495
May1st to 15thNight
30%11%30%18%7%1
495
16th to endNight
25%12%36%20%5%
513
June1st to 15thNight
28%9%33%23%5%
465
16th to endNight
22%8%32%27%7%1
330
July1st to 15thNight
16%5%41%29%6%
358
16th to endNight
19%6%37%28%7%
523
August1st to 15thNight
20%5%34%27%11%1
494
16th to endNight
20%6%31%31%8%1
525
September1st to 15thNight
21%7%37%26%7%
495
16th to endNight
21%11%35%25%5%
621
October1st to 15thNight
22%13%33%21%8%
660
16th to endNight
35%19%27%13%3
707
November1st to 15thNight
29%17%30%15%5%1
730
16th to endNight
28%22%26%17%4
750
December1st to 15thNight
32%22%29%11%3
750
16th to endNight
33%23%27%10%3
800
Page generated at 2017-04-03 02:35:07. Version ac04

Copyright 2017 A. Danko


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