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 2018-10-27.

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%
16505
12%
50919
5%
16460
27%
16460
15%
36891

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%
825
10%
2716
1%
821
21%
821
9%
2029
January16th to endNight
14%
848
14%
2775
3%
848
26%
848
11%
2017
February1st to 15thNight
14%
764
9%
2481
2%
761
22%
761
11%
1875
February16th to endNight
16%
683
10%
2195
3%
683
24%
683
10%
1665
March1st to 15thNight
16%
779
13%
2178
4%
779
23%
779
11%
1721
March16th to endNight
19%
819
13%
2275
5%
819
26%
819
15%
1748
April1st to 15thNight
18%
584
12%
1946
6%
584
26%
584
13%
1430
April16th to endNight
23%
578
14%
1754
7%
578
30%
578
16%
1261
May1st to 15thNight
20%
585
12%
1609
4%
585
27%
585
16%
1191
May16th to endNight
20%
609
10%
1624
3%
608
26%
608
20%
1180
June1st to 15thNight
23%
549
8%
1524
4%
549
26%
549
18%
1143
June16th to endNight
28%
390
9%
1365
3%
390
36%
390
18%
916
July1st to 15thNight
33%
428
11%
1353
6%
428
39%
428
29%
826
July16th to endNight
32%
613
11%
1547
6%
580
36%
580
23%
1094
August1st to 15thNight
33%
574
10%
1713
5%
570
37%
570
24%
1158
August16th to endNight
37%
621
14%
1938
7%
621
43%
621
25%
1242
September1st to 15thNight
30%
585
18%
1950
12%
585
40%
585
25%
1194
September16th to endNight
29%
735
20%
2161
11%
735
38%
735
25%
1383
October1st to 15thNight
24%
780
17%
2340
7%
780
33%
780
22%
1572
October16th to endNight
14%
821
14%
2467
4%
821
23%
821
13%
1791
November1st to 15thNight
17%
805
10%
2636
5%
805
23%
805
12%
1950
November16th to endNight
17%
825
11%
2730
4%
825
25%
825
10%
2053
December1st to 15thNight
8%
825
10%
2730
0%
825
18%
825
7%
2128
December16th to endNight
7%
880
8%
2912
1%
880
15%
880
6%
2324

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%9%46%5%3445%6%30%
52643
Night
19%10%46%6%35%446%29%
51086
TransparencyDay
54%412%20%8%
52329
Night
55%412%20%7%
50919
SeeingDay
24%17%32%18%6%
9098
Night
25%16%32%19%5%
16506

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%6%6%7%445%36%25%
1552
16th to endDay
13%12%49%7%45%445%28%
1797
February1st to 15thDay
16%13%5%7%6%34445%27%
1710
16th to endDay
14%13%6%8%6%25%45%7%25%
1563
March1st to 15thDay
16%13%5%8%7%45%45%424%
2101
16th to endDay
16%14%7%8%5%2333429%
2301
April1st to 15thDay
18%11%47%6%35%346%27%
2333
16th to endDay
22%9%25%4335%46%30%
2479
May1st to 15thDay
21%9%37%5%345%5%5%29%
2673
16th to endDay
23%8%35%5%3335%6%30%
2842
June1st to 15thDay
28%7%345%3345%7%25%
2775
16th to endDay
22%6%35%5%24447%31%
2925
July1st to 15thDay
12%5%245%35%45%9%38%
2847
16th to endDay
16%7%36%6%35%5%5%7%32%
2876
August1st to 15thDay
15%6%25%5%35%46%8%35%
2488
16th to endDay
14%5%1443346%8%43%
2615
September1st to 15thDay
19%5%2442346%7%39%
2340
16th to endDay
18%6%24423347%40%
2127
October1st to 15thDay
21%8%26%424447%33%
1950
16th to endDay
20%11%47%6%34446%25%
2014
November1st to 15thDay
22%13%36%5%34445%26%
1551
16th to endDay
14%14%6%8%5%4445%8%21%
1560
December1st to 15thDay
21%17%6%8%6%345%45%16%
1560
16th to endDay
21%16%5%9%7%34435%17%
1664
January1st to 15thNight
15%13%6%8%6%35%44425%
2716
16th to endNight
15%11%5%8%7%35%345%29%
2775
February1st to 15thNight
18%13%47%7%35%445%25%
2480
16th to endNight
16%15%6%7%6%35%5%4424%
2195
March1st to 15thNight
18%13%5%9%6%35%5%4423%
2166
16th to endNight
18%14%5%7%5%3433427%
2275
April1st to 15thNight
20%13%47%5%24435%28%
1946
16th to endNight
23%10%34425%446%30%
1754
May1st to 15thNight
26%8%25%5%25%445%30%
1609
16th to endNight
20%8%26%43435%9%31%
1622
June1st to 15thNight
25%9%27%5%14438%28%
1524
16th to endNight
19%6%25%4345%5%7%34%
1365
July1st to 15thNight
11%6%244245%7%9%40%
1427
16th to endNight
14%6%25%6%36%5%6%9%31%
1643
August1st to 15thNight
16%6%25%5%35%5%6%7%35%
1725
16th to endNight
15%5%25%4245%6%8%38%
1938
September1st to 15thNight
17%42443345%8%40%
1950
16th to endNight
16%6%15%425%5%5%6%41%
2161
October1st to 15thNight
19%5%25%5%3446%6%35%
2340
16th to endNight
25%9%25%6%24345%29%
2467
November1st to 15thNight
21%12%36%7%35%435%26%
2636
16th to endNight
19%15%46%5%35%446%23%
2730
December1st to 15thNight
22%14%47%6%35%446%18%
2730
16th to endNight
23%16%5%9%7%35%335%17%
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
59%5%11%14%8%
1553
16th to endDay
59%38%16%11%
1797
February1st to 15thDay
60%210%17%7%
1713
16th to endDay
58%312%16%7%1
1563
March1st to 15thDay
63%38%17%6%
2112
16th to endDay
61%29%17%7%1
2301
April1st to 15thDay
58%37%15%12%1
2333
16th to endDay
54%410%18%11%
2479
May1st to 15thDay
56%49%19%8%
2673
16th to endDay
54%5%11%21%7%
2846
June1st to 15thDay
59%312%18%6%
2775
16th to endDay
52%313%21%7%
2925
July1st to 15thDay
40%5%15%26%10%
2694
16th to endDay
50%5%15%22%5%
2709
August1st to 15thDay
46%6%15%23%8%
2475
16th to endDay
38%5%17%28%9%
2615
September1st to 15thDay
44%414%25%11%
2340
16th to endDay
43%411%28%11%
2127
October1st to 15thDay
50%412%24%8%
1950
16th to endDay
57%311%20%6%
2014
November1st to 15thDay
59%312%17%6%
1551
16th to endDay
58%414%16%5%
1560
December1st to 15thDay
67%211%15%3
1560
16th to endDay
68%29%13%5%
1664
January1st to 15thNight
60%411%16%7%
2716
16th to endNight
57%310%21%7%
2775
February1st to 15thNight
61%310%14%9%
2481
16th to endNight
62%210%15%8%1
2195
March1st to 15thNight
63%37%16%7%
2178
16th to endNight
60%27%17%10%1
2275
April1st to 15thNight
57%38%17%11%1
1946
16th to endNight
53%49%17%13%1
1754
May1st to 15thNight
56%310%21%8%
1609
16th to endNight
51%415%20%7%
1624
June1st to 15thNight
56%412%20%7%
1524
16th to endNight
47%6%15%22%7%
1365
July1st to 15thNight
35%6%20%28%8%
1353
16th to endNight
47%6%17%21%6%
1547
August1st to 15thNight
46%419%23%6%
1713
16th to endNight
42%5%17%27%7%
1938
September1st to 15thNight
40%413%30%11%
1950
16th to endNight
41%314%28%11%
2161
October1st to 15thNight
46%313%27%9%
2340
16th to endNight
55%210%22%8%
2467
November1st to 15thNight
58%314%16%7%
2636
16th to endNight
59%5%13%17%4
2730
December1st to 15thNight
64%410%17%3
2730
16th to endNight
68%27%15%5%
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%29%31%15%3
285
16th to endDay
21%27%34%13%2
304
February1st to 15thDay
27%22%30%16%2
281
16th to endDay
22%21%32%17%5%
251
March1st to 15thDay
24%26%30%13%3
323
16th to endDay
26%23%29%15%3
352
April1st to 15thDay
24%30%33%8%3
330
16th to endDay
21%21%32%17%5%
319
May1st to 15thDay
30%18%28%12%7%2
494
16th to endDay
28%16%31%19%3
599
June1st to 15thDay
34%12%27%19%6%
570
16th to endDay
26%11%32%22%6%1
570
July1st to 15thDay
16%9%40%23%10%
550
16th to endDay
21%6%33%27%10%
593
August1st to 15thDay
17%5%36%27%10%2
358
16th to endDay
14%7%34%29%11%2
396
September1st to 15thDay
19%10%34%26%6%1
375
16th to endDay
21%13%33%24%5%
356
October1st to 15thDay
24%15%34%14%9%1
315
16th to endDay
24%28%28%13%4
323
November1st to 15thDay
32%19%25%15%6%1
280
16th to endDay
30%22%30%10%5%
285
December1st to 15thDay
37%22%28%11%
285
16th to endDay
28%29%29%10%1
304
January1st to 15thNight
23%25%32%14%2
825
16th to endNight
23%22%33%16%3
848
February1st to 15thNight
28%17%33%18%1
764
16th to endNight
24%21%30%18%5%
683
March1st to 15thNight
24%21%30%19%3
780
16th to endNight
27%17%28%19%6%
819
April1st to 15thNight
27%19%29%17%6%
584
16th to endNight
30%12%30%20%5%
578
May1st to 15thNight
31%12%30%17%7%
585
16th to endNight
25%12%36%19%4
609
June1st to 15thNight
28%9%33%23%5%
549
16th to endNight
21%10%34%26%6%1
390
July1st to 15thNight
15%5%42%29%7%
428
16th to endNight
17%6%37%30%7%
613
August1st to 15thNight
18%5%35%28%10%1
574
16th to endNight
18%6%33%30%9%1
621
September1st to 15thNight
19%7%37%27%7%
585
16th to endNight
20%12%34%25%6%
735
October1st to 15thNight
22%12%34%21%7%
780
16th to endNight
33%19%28%14%3
821
November1st to 15thNight
29%17%30%15%5%
805
16th to endNight
27%23%26%18%4
825
December1st to 15thNight
34%22%29%10%3
825
16th to endNight
32%24%28%10%3
880
Page generated at 2018-10-28 09:41:00. Version ac04

Copyright 2018 A. Danko


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