Stettler
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stettler clear sky chart from 2005-11-05 to 2017-10-31.

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
41%
15409
11%
47306
7%
15383
45%
15383
19%
33320

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
33%
895
8%
2685
5%
895
36%
895
13%
2056
January16th to endNight
35%
892
15%
2812
8%
892
43%
892
16%
1994
February1st to 15thNight
40%
697
9%
2398
8%
696
43%
696
16%
1708
February16th to endNight
42%
632
12%
2028
11%
632
46%
632
17%
1451
March1st to 15thNight
39%
720
13%
2094
8%
720
44%
720
19%
1523
March16th to endNight
35%
768
8%
2109
3%
767
39%
767
16%
1641
April1st to 15thNight
36%
590
10%
1677
5%
590
40%
590
18%
1227
April16th to endNight
42%
540
12%
1620
9%
540
45%
540
21%
1134
May1st to 15thNight
45%
428
10%
1359
8%
428
48%
428
21%
934
May16th to endNight
42%
374
3%
1309
2%
374
43%
374
15%
932
June1st to 15thNight
38%
360
0%
1260
0%
360
38%
360
14%
902
June16th to endNight
49%
360
0%
1260
0%
360
49%
360
18%
860
July1st to 15thNight
57%
340
0%
1190
0%
340
57%
340
23%
747
July16th to endNight
59%
376
5%
1239
5%
354
60%
354
25%
752
August1st to 15thNight
61%
410
7%
1444
9%
408
63%
408
21%
928
August16th to endNight
62%
573
14%
1719
12%
573
63%
573
31%
1045
September1st to 15thNight
55%
612
15%
1782
11%
612
57%
612
30%
1121
September16th to endNight
52%
716
19%
1980
13%
716
57%
716
34%
1212
October1st to 15thNight
37%
720
14%
2130
8%
720
44%
720
22%
1458
October16th to endNight
40%
771
16%
2499
10%
771
48%
771
20%
1692
November1st to 15thNight
34%
875
15%
2450
9%
875
40%
875
21%
1741
November16th to endNight
30%
900
11%
2682
6%
900
34%
900
15%
2005
December1st to 15thNight
28%
900
9%
2700
5%
900
31%
900
12%
2139
December16th to endNight
35%
960
13%
2880
8%
960
39%
960
17%
2118

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
11%8%37%6%35%5%6%8%32%
48474
Night
9%9%47%6%35%5%6%8%31%
47460
TransparencyDay
48%8%17%19%5%
48124
Night
48%8%16%19%7%1
47314
SeeingDay
16%5%24%30%18%4
6237
Night
13%5%28%34%15%2
15423

By Month

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
6%13%6%9%8%47%5%5%7%24%
1253
16th to endDay
7%12%410%6%35%5%6%7%29%
1422
February1st to 15thDay
9%11%5%8%7%6%446%8%27%
1459
16th to endDay
6%14%7%9%7%36%6%48%24%
1446
March1st to 15thDay
9%11%48%8%47%6%5%6%25%
1866
16th to endDay
11%12%6%10%5%45%46%7%23%
2111
April1st to 15thDay
13%10%47%7%45%6%5%6%27%
2269
16th to endDay
16%9%37%5%445%5%7%30%
2340
May1st to 15thDay
10%8%36%7%36%6%5%7%33%
2590
16th to endDay
19%7%36%5%35%5%6%8%27%
2802
June1st to 15thDay
19%8%36%6%45%5%6%7%25%
2700
16th to endDay
14%7%35%5%45%6%6%10%31%
2700
July1st to 15thDay
12%415%5%35%5%6%9%39%
2700
16th to endDay
10%4245%35%5%6%8%44%
2846
August1st to 15thDay
13%6%15%425%5%6%10%38%
2505
16th to endDay
9%414435%5%6%10%44%
2483
September1st to 15thDay
14%7%25%5%33346%42%
2176
16th to endDay
9%6%25%42436%10%45%
1980
October1st to 15thDay
12%10%46%5%3435%6%36%
1827
16th to endDay
9%11%45%5%35%6%6%6%35%
1712
November1st to 15thDay
8%11%5%8%7%346%6%8%28%
1408
16th to endDay
8%8%5%11%9%46%46%6%28%
1275
December1st to 15thDay
9%14%6%13%9%6%7%435%18%
1260
16th to endDay
6%11%412%10%46%5%5%6%24%
1344
January1st to 15thNight
7%10%5%11%8%46%7%6%8%22%
2685
16th to endNight
5%12%49%7%46%5%5%7%31%
2812
February1st to 15thNight
6%9%5%10%8%46%5%5%7%30%
2392
16th to endNight
7%12%6%7%6%347%6%7%28%
2028
March1st to 15thNight
6%9%47%8%47%6%7%10%26%
2094
16th to endNight
8%12%6%9%6%45%6%7%8%21%
2109
April1st to 15thNight
12%10%38%7%45%5%7%8%26%
1677
16th to endNight
13%11%36%5%35%45%8%33%
1620
May1st to 15thNight
11%11%37%5%25%5%6%7%33%
1358
16th to endNight
21%6%27%5%345%5%7%29%
1309
June1st to 15thNight
16%7%46%7%35%6%7%7%27%
1260
16th to endNight
8%7%36%7%46%6%5%8%35%
1260
July1st to 15thNight
10%3245%35%6%8%11%37%
1260
16th to endNight
8%3244345%6%11%43%
1323
August1st to 15thNight
10%5%246%35%5%7%9%39%
1451
16th to endNight
8%325%5%345%7%9%45%
1719
September1st to 15thNight
12%424424437%46%
1782
16th to endNight
9%5%2442345%8%48%
1980
October1st to 15thNight
11%9%48%42445%8%35%
2130
16th to endNight
8%9%35%6%36%5%7%8%33%
2499
November1st to 15thNight
7%11%46%6%45%5%5%8%33%
2450
16th to endNight
6%11%6%10%7%36%45%7%27%
2682
December1st to 15thNight
8%13%7%11%8%46%45%7%22%
2700
16th to endNight
5%11%5%10%8%46%5%6%9%26%
2880

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
57%7%13%16%4
1253
16th to endDay
50%7%14%16%8%1
1422
February1st to 15thDay
53%7%16%15%6%
1459
16th to endDay
56%6%14%15%6%
1446
March1st to 15thDay
54%9%15%14%4
1866
16th to endDay
57%8%14%15%3
2112
April1st to 15thDay
54%7%15%15%6%
2269
16th to endDay
51%7%15%17%7%1
2340
May1st to 15thDay
46%8%13%21%9%
2590
16th to endDay
53%8%15%16%6%
2807
June1st to 15thDay
54%7%14%18%3
2700
16th to endDay
45%10%21%18%3
2700
July1st to 15thDay
40%9%22%22%4
2541
16th to endDay
36%10%23%25%3
2667
August1st to 15thDay
39%10%25%18%4
2487
16th to endDay
33%8%24%25%8%
2483
September1st to 15thDay
42%5%16%23%9%2
2176
16th to endDay
35%7%18%27%8%2
1980
October1st to 15thDay
48%6%18%19%7%
1827
16th to endDay
46%8%15%22%6%
1712
November1st to 15thDay
50%7%16%18%4
1408
16th to endDay
54%8%16%13%5%1
1275
December1st to 15thDay
68%5%9%14%2
1260
16th to endDay
57%6%12%17%5%
1344
January1st to 15thNight
56%8%16%12%41
2685
16th to endNight
49%7%14%17%8%2
2812
February1st to 15thNight
51%7%14%17%8%
2403
16th to endNight
49%8%14%15%9%1
2028
March1st to 15thNight
48%10%17%18%5%
2094
16th to endNight
57%7%14%15%4
2112
April1st to 15thNight
52%7%15%17%7%
1677
16th to endNight
48%6%14%21%7%2
1620
May1st to 15thNight
47%5%12%23%10%1
1359
16th to endNight
52%7%11%19%6%1
1309
June1st to 15thNight
51%9%13%19%5%
1260
16th to endNight
45%10%19%18%5%
1260
July1st to 15thNight
36%11%22%24%5%
1190
16th to endNight
32%12%22%25%6%
1239
August1st to 15thNight
38%11%21%22%5%
1444
16th to endNight
33%7%21%27%8%1
1719
September1st to 15thNight
37%6%15%24%12%4
1782
16th to endNight
32%6%17%26%13%2
1980
October1st to 15thNight
45%6%17%21%8%
2130
16th to endNight
44%8%17%23%5%
2499
November1st to 15thNight
47%7%15%21%6%1
2450
16th to endNight
54%7%15%13%7%1
2682
December1st to 15thNight
61%7%12%15%3
2700
16th to endNight
52%7%15%19%4
2880

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
8%126%38%18%6%
60
16th to endDay
4326%28%26%10%
64
February1st to 15thDay
18%5%23%36%9%5%
71
16th to endDay
20%224%26%22%1
105
March1st to 15thDay
15%6%37%30%9%1
270
16th to endDay
18%7%33%28%11%1
288
April1st to 15thDay
16%13%27%28%11%1
269
16th to endDay
25%7%24%26%12%3
270
May1st to 15thDay
12%7%26%29%18%4
438
16th to endDay
22%320%27%18%7%
517
June1st to 15thDay
20%7%22%32%13%4
495
16th to endDay
13%5%25%30%19%4
495
July1st to 15thDay
13%215%36%27%5%
475
16th to endDay
11%421%33%24%5%
515
August1st to 15thDay
13%217%30%26%10%
351
16th to endDay
10%6%18%32%26%3
332
September1st to 15thDay
20%324%26%17%6%
315
16th to endDay
13%7%27%28%18%4
315
October1st to 15thDay
21%6%29%18%19%4
171
16th to endDay
17%6%26%31%15%2
144
November1st to 15thDay
17%234%32%13%
90
16th to endDay
12%7%31%19%19%9%
63
December1st to 15thDay
8%138%28%21%1
60
16th to endDay
17%26%39%14%3
64
January1st to 15thNight
12%8%33%30%14%1
900
16th to endNight
12%8%31%33%11%2
892
February1st to 15thNight
11%7%24%35%17%2
704
16th to endNight
13%426%35%17%2
632
March1st to 15thNight
9%5%31%36%15%2
720
16th to endNight
14%429%36%12%2
768
April1st to 15thNight
14%6%31%28%16%2
590
16th to endNight
19%5%24%35%12%2
540
May1st to 15thNight
16%5%24%35%16%2
429
16th to endNight
23%421%28%20%2
375
June1st to 15thNight
21%423%33%14%3
360
16th to endNight
13%323%32%25%1
360
July1st to 15thNight
12%217%42%22%
340
16th to endNight
10%220%41%23%1
376
August1st to 15thNight
16%13%34%31%3
410
16th to endNight
9%317%42%26%1
573
September1st to 15thNight
15%220%38%21%1
612
16th to endNight
12%425%38%16%2
716
October1st to 15thNight
16%332%30%15%2
720
16th to endNight
13%5%31%37%11%
771
November1st to 15thNight
14%6%34%32%9%2
875
16th to endNight
12%7%35%31%10%2
900
December1st to 15thNight
14%7%33%27%13%3
900
16th to endNight
11%332%32%15%3
960
Page generated at 2017-11-01 15:23:31. Version ac04

Copyright 2017 A. Danko


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