Wallace
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wallace clear sky chart from 2005-11-06 to 2024-01-12.

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
18%
23613
12%
74279
4%
23544
27%
23544
14%
53940

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 10thNight
9%
850
10%
2649
1%
847
19%
847
9%
2019
January11th to 20thNight
12%
808
9%
2541
2%
808
20%
808
9%
1997
January21st to endNight
15%
796
16%
2583
4%
796
29%
796
12%
1832
February1st to 10thNight
12%
720
11%
2340
3%
720
22%
720
10%
1747
February11th to 20thNight
9%
703
10%
2276
1%
700
20%
700
8%
1735
February21st to endNight
18%
592
15%
1889
4%
592
30%
592
14%
1338
March1st to 10thNight
12%
720
15%
2026
4%
720
23%
720
11%
1592
March11th to 20thNight
18%
720
14%
1980
5%
720
25%
720
14%
1495
March21st to endNight
17%
774
13%
2160
4%
774
27%
774
15%
1652
April1st to 10thNight
15%
540
11%
1800
5%
540
22%
540
11%
1342
April11th to 20thNight
19%
534
16%
1719
8%
534
29%
534
15%
1202
April21st to endNight
21%
540
13%
1620
5%
540
28%
540
14%
1217
May1st to 10thNight
21%
540
13%
1508
5%
540
27%
540
15%
1131
May11th to 20thNight
21%
532
15%
1417
5%
532
29%
532
19%
1030
May21st to endNight
19%
583
11%
1551
2%
582
26%
582
22%
1106
June1st to 10thNight
20%
540
8%
1440
3%
540
24%
540
18%
1087
June11th to 20thNight
26%
400
14%
1300
6%
400
34%
400
20%
853
June21st to endNight
26%
360
8%
1260
3%
360
32%
360
15%
885
July1st to 10thNight
29%
350
11%
1225
5%
350
38%
350
24%
765
July11th to 20thNight
31%
517
11%
1387
6%
517
35%
517
26%
944
July21st to endNight
30%
590
11%
1486
5%
558
36%
558
22%
1069
August1st to 10thNight
33%
538
11%
1600
5%
534
38%
534
26%
1029
August11th to 20thNight
29%
532
12%
1596
5%
532
35%
532
21%
1078
August21st to endNight
38%
594
16%
1885
9%
594
46%
594
26%
1182
September1st to 10thNight
30%
540
16%
1800
8%
540
42%
540
26%
1094
September11th to 20thNight
31%
571
20%
1831
13%
571
42%
571
24%
1134
September21st to endNight
26%
720
19%
2058
9%
720
34%
720
24%
1365
October1st to 10thNight
27%
720
18%
2160
8%
720
36%
720
23%
1408
October11th to 20thNight
21%
720
17%
2160
6%
720
31%
720
19%
1482
October21st to endNight
13%
807
14%
2407
4%
807
23%
807
11%
1798
November1st to 10thNight
13%
830
11%
2552
3%
830
22%
830
12%
1906
November11th to 20thNight
15%
850
13%
2660
4%
850
24%
850
11%
1989
November21st to endNight
13%
850
9%
2660
2%
850
19%
850
9%
2043
December1st to 10thNight
8%
850
10%
2660
1%
850
17%
850
8%
2101
December11th to 20thNight
6%
850
8%
3242
1%
849
14%
849
6%
2612
December21st to endNight
8%
932
5%
4851
1%
907
16%
907
4%
3681

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
18%10%47%6%35%5%5%7%30%
75188
Night
19%11%47%6%35%45%6%29%
74528
TransparencyDay
55%412%20%9%1
74887
Night
56%312%20%8%1
74365
SeeingDay
26%19%33%17%5%1
16286
Night
26%17%32%19%5%
23616

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 10thDay
17%15%8%10%7%445%35%22%
1516
11th to 20thDay
18%15%7%9%8%46%45%5%20%
1448
21st to endDay
12%10%5%10%9%44446%30%
1769
February1st to 10thDay
17%12%5%8%7%45%345%29%
1620
11th to 20thDay
18%14%5%8%7%345%45%26%
1573
21st to endDay
10%13%6%9%5%36%46%8%30%
1366
March1st to 10thDay
15%15%6%8%7%45%45%5%26%
1930
11th to 20thDay
12%11%6%10%9%36%5%5%5%28%
1980
21st to endDay
18%17%7%8%6%3333429%
2196
April1st to 10thDay
21%12%48%6%35%446%27%
2160
11th to 20thDay
21%10%46%5%345%47%32%
2190
21st to endDay
22%11%36%5%446%5%7%28%
2340
May1st to 10thDay
25%10%46%5%445%5%6%27%
2452
11th to 20thDay
21%9%26%5%345%5%7%34%
2478
21st to endDay
21%9%35%5%3446%7%33%
2724
June1st to 10thDay
26%8%36%6%345%5%8%25%
2520
11th to 20thDay
22%7%35%5%3445%8%33%
2672
21st to endDay
23%8%36%6%35%45%6%31%
2700
July1st to 10thDay
16%5%25%6%35%5%6%9%38%
2683
11th to 20thDay
12%7%36%6%45%5%6%9%38%
2520
21st to endDay
18%8%36%6%35%6%5%7%33%
2744
August1st to 10thDay
13%6%36%5%36%5%7%9%38%
2327
11th to 20thDay
16%6%36%5%45%6%6%9%34%
2304
21st to endDay
15%5%25%42446%8%45%
2469
September1st to 10thDay
17%5%25%43447%8%42%
2160
11th to 20thDay
18%7%26%5%35%45%7%38%
2126
21st to endDay
19%7%345%3345%8%40%
1900
October1st to 10thDay
19%7%36%5%35%5%5%8%35%
1800
11th to 20thDay
19%11%46%5%45%5%6%8%28%
1800
21st to endDay
19%12%48%7%345%5%6%26%
1949
November1st to 10thDay
21%13%46%6%35%5%46%27%
1523
11th to 20thDay
16%15%6%9%6%5%5%5%46%24%
1520
21st to endDay
16%16%6%7%6%45%5%5%8%23%
1520
December1st to 10thDay
21%17%5%9%6%35%5%5%5%18%
1520
11th to 20thDay
21%18%7%11%8%4444417%
1906
21st to endDay
19%14%9%11%6%3444420%
2783
January1st to 10thNight
17%16%6%10%7%445%4423%
2649
11th to 20thNight
18%13%7%10%7%46%445%23%
2541
21st to endNight
12%12%6%9%7%35%45%6%30%
2583
February1st to 10thNight
18%13%5%9%6%35%45%427%
2340
11th to 20thNight
18%13%5%9%8%45%446%23%
2273
21st to endNight
12%14%6%8%6%346%5%6%30%
1889
March1st to 10thNight
17%15%6%9%6%36%435%26%
2017
11th to 20thNight
15%11%7%9%7%345%5%5%28%
1979
21st to endNight
18%15%5%8%6%35%345%29%
2160
April1st to 10thNight
22%13%5%7%5%45%5%45%25%
1800
11th to 20thNight
22%11%45%425%5%45%33%
1719
21st to endNight
24%12%46%6%25%446%27%
1620
May1st to 10thNight
26%9%26%5%36%446%29%
1508
11th to 20thNight
24%8%26%6%34446%33%
1416
21st to endNight
18%9%26%435%5%5%9%33%
1550
June1st to 10thNight
25%9%37%6%24448%28%
1440
11th to 20thNight
19%8%36%424448%38%
1300
21st to endNight
22%7%26%5%45%6%6%7%32%
1260
July1st to 10thNight
15%6%35%435%6%7%9%38%
1260
11th to 20thNight
12%7%26%5%36%6%7%9%36%
1434
21st to endNight
15%8%37%7%46%5%6%9%30%
1573
August1st to 10thNight
14%6%25%6%35%5%6%8%39%
1611
11th to 20thNight
16%8%36%6%446%6%7%34%
1596
21st to endNight
14%6%25%435%5%7%9%39%
1885
September1st to 10thNight
14%5%36%435%5%6%8%42%
1800
11th to 20thNight
18%6%35%43345%6%42%
1831
21st to endNight
18%7%25%5%345%5%7%40%
2058
October1st to 10thNight
19%6%25%5%3446%7%39%
2160
11th to 20thNight
19%8%36%6%35%47%7%32%
2160
21st to endNight
27%10%37%6%35%445%27%
2407
November1st to 10thNight
21%14%47%7%34435%28%
2552
11th to 20thNight
19%13%5%7%8%46%5%45%24%
2660
21st to endNight
22%16%47%6%35%446%23%
2660
December1st to 10thNight
23%16%5%8%7%35%45%5%18%
2660
11th to 20thNight
21%18%6%10%7%45%335%19%
3293
21st to endNight
25%15%5%12%5%34335%21%
4884

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 10thDay
65%410%13%8%
1517
11th to 20thDay
66%49%13%7%
1448
21st to endDay
58%38%17%14%1
1769
February1st to 10thDay
60%211%16%10%1
1620
11th to 20thDay
62%39%17%8%1
1581
21st to endDay
54%211%18%11%2
1366
March1st to 10thDay
62%36%19%9%1
1934
11th to 20thDay
60%39%17%8%2
1980
21st to endDay
63%27%17%8%2
2196
April1st to 10thDay
61%38%15%10%3
2160
11th to 20thDay
54%37%21%13%1
2190
21st to endDay
58%410%17%9%1
2340
May1st to 10thDay
61%48%18%9%1
2452
11th to 20thDay
52%410%23%11%1
2482
21st to endDay
52%5%13%22%8%1
2724
June1st to 10thDay
59%312%20%6%
2520
11th to 20thDay
52%311%24%9%1
2672
21st to endDay
55%413%18%9%1
2700
July1st to 10thDay
42%5%17%26%10%1
2608
11th to 20thDay
43%5%17%25%9%1
2444
21st to endDay
51%5%15%22%7%
2591
August1st to 10thDay
42%6%16%28%8%
2314
11th to 20thDay
48%416%25%7%
2304
21st to endDay
39%416%29%12%
2469
September1st to 10thDay
41%415%28%12%1
2160
11th to 20thDay
47%312%25%12%1
2126
21st to endDay
45%310%28%13%1
1900
October1st to 10thDay
48%311%28%10%
1800
11th to 20thDay
54%414%22%6%
1800
21st to endDay
58%311%19%8%
1949
November1st to 10thDay
59%49%19%8%
1523
11th to 20thDay
59%312%19%7%
1520
21st to endDay
59%5%14%16%7%
1520
December1st to 10thDay
67%212%15%4
1520
11th to 20thDay
71%37%14%41
1905
21st to endDay
69%114%11%41
2783
January1st to 10thNight
63%210%18%6%
2649
11th to 20thNight
64%411%13%7%1
2541
21st to endNight
55%311%22%9%1
2583
February1st to 10thNight
60%310%14%11%2
2340
11th to 20thNight
63%39%14%10%1
2276
21st to endNight
56%29%19%12%1
1889
March1st to 10thNight
64%36%16%9%1
2026
11th to 20thNight
58%310%18%9%2
1980
21st to endNight
60%28%18%11%2
2160
April1st to 10thNight
60%49%14%11%3
1800
11th to 20thNight
54%37%23%12%1
1719
21st to endNight
59%49%16%12%1
1620
May1st to 10thNight
58%38%19%10%1
1508
11th to 20thNight
54%39%24%9%1
1417
21st to endNight
48%5%17%21%8%1
1551
June1st to 10thNight
56%411%21%7%
1440
11th to 20thNight
47%312%25%11%1
1300
21st to endNight
51%7%14%18%9%1
1260
July1st to 10thNight
41%5%21%26%6%1
1225
11th to 20thNight
43%6%17%25%8%
1387
21st to endNight
51%5%17%20%7%
1486
August1st to 10thNight
42%5%19%28%7%
1600
11th to 20thNight
48%419%23%5%
1596
21st to endNight
41%418%28%9%
1885
September1st to 10thNight
40%414%31%11%
1800
11th to 20thNight
42%313%27%13%1
1831
21st to endNight
45%412%28%12%
2058
October1st to 10thNight
44%313%27%13%
2160
11th to 20thNight
49%313%28%6%
2160
21st to endNight
59%310%19%9%
2407
November1st to 10thNight
59%313%16%8%1
2552
11th to 20thNight
59%312%17%8%
2660
21st to endNight
62%414%17%4
2660
December1st to 10thNight
66%310%16%4
2660
11th to 20thNight
68%37%17%5%
3295
21st to endNight
68%114%12%41
4884

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 10thDay
29%25%29%14%2
370
11th to 20thDay
28%25%28%15%3
343
21st to endDay
20%28%36%13%3
374
February1st to 10thDay
28%27%32%12%1
340
11th to 20thDay
33%27%28%11%1
336
21st to endDay
23%26%31%15%5%
280
March1st to 10thDay
26%27%33%12%21
400
11th to 20thDay
25%25%33%14%4
420
21st to endDay
31%24%30%12%2
462
April1st to 10thDay
32%31%28%7%2
420
11th to 20thDay
30%26%30%11%3
412
21st to endDay
29%20%31%15%4
420
May1st to 10thDay
35%20%29%10%5%1
535
11th to 20thDay
27%19%31%18%5%1
624
21st to endDay
28%16%37%16%3
680
June1st to 10thDay
34%13%31%17%5%
630
11th to 20thDay
27%13%35%20%5%1
630
21st to endDay
27%13%31%21%7%1
630
July1st to 10thDay
20%11%40%21%7%1
620
11th to 20thDay
16%9%43%24%9%
618
21st to endDay
21%10%35%27%7%
684
August1st to 10thDay
13%6%41%31%7%1
446
11th to 20thDay
22%10%32%24%10%2
439
21st to endDay
17%11%33%29%8%2
495
September1st to 10thDay
16%16%40%19%7%2
450
11th to 20thDay
25%17%28%24%5%
450
21st to endDay
23%17%32%20%7%2
410
October1st to 10thDay
22%16%34%19%7%2
360
11th to 20thDay
23%21%32%18%6%1
360
21st to endDay
27%25%31%13%41
396
November1st to 10thDay
30%24%30%12%41
365
11th to 20thDay
33%24%30%8%41
370
21st to endDay
33%26%28%10%2
370
December1st to 10thDay
37%22%30%9%2
370
11th to 20thDay
36%28%27%9%
370
21st to endDay
27%30%29%13%1
407
January1st to 10thNight
28%23%32%14%3
850
11th to 20thNight
27%24%31%15%3
808
21st to endNight
20%24%34%18%31
796
February1st to 10thNight
28%20%32%18%2
720
11th to 20thNight
31%25%30%12%2
703
21st to endNight
19%21%35%20%5%
592
March1st to 10thNight
26%21%34%16%2
720
11th to 20thNight
24%20%30%20%6%1
720
21st to endNight
26%20%31%17%5%
774
April1st to 10thNight
30%21%29%17%3
540
11th to 20thNight
30%16%31%16%7%
534
21st to endNight
32%13%29%20%6%1
540
May1st to 10thNight
32%15%29%18%6%1
540
11th to 20thNight
29%11%33%21%6%
532
21st to endNight
23%13%42%19%3
583
June1st to 10thNight
29%12%33%21%4
540
11th to 20thNight
22%12%36%24%6%
400
21st to endNight
24%10%32%26%6%1
360
July1st to 10thNight
20%6%41%26%7%
350
11th to 20thNight
16%7%42%30%5%
517
21st to endNight
19%7%36%31%7%
590
August1st to 10thNight
16%6%39%29%8%1
538
11th to 20thNight
18%7%37%28%8%1
532
21st to endNight
16%8%32%34%9%1
594
September1st to 10thNight
16%9%41%27%6%1
540
11th to 20thNight
22%9%32%28%8%
571
21st to endNight
23%14%34%24%6%1
720
October1st to 10thNight
24%11%33%25%7%
720
11th to 20thNight
23%16%36%18%7%1
720
21st to endNight
34%20%28%15%3
807
November1st to 10thNight
31%20%30%14%4
830
11th to 20thNight
28%24%28%15%4
850
21st to endNight
32%23%27%16%2
850
December1st to 10thNight
34%20%30%13%3
850
11th to 20thNight
32%26%29%10%3
850
21st to endNight
32%24%29%12%21
935
Page generated at 2024-01-09 08:14:45. Version ac07

Copyright 2024 Attilla Danko


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