Olds
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Olds clear sky chart from 2005-11-05 to 2017-09-19.

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
42%
15171
12%
46806
8%
15143
46%
15143
20%
32469

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
11%
2685
7%
895
36%
895
14%
2062
January16th to endNight
36%
838
17%
2758
11%
838
44%
838
18%
1900
February1st to 15thNight
41%
700
12%
2427
12%
697
46%
697
16%
1694
February16th to endNight
42%
632
13%
1983
11%
632
46%
632
18%
1413
March1st to 15thNight
38%
720
13%
2121
8%
720
43%
720
19%
1542
March16th to endNight
37%
768
11%
2079
5%
767
41%
767
18%
1576
April1st to 15thNight
34%
623
11%
1703
5%
623
39%
623
18%
1274
April16th to endNight
37%
540
11%
1620
9%
540
39%
540
19%
1167
May1st to 15thNight
41%
401
9%
1382
8%
401
45%
401
21%
896
May16th to endNight
42%
374
4%
1309
2%
374
43%
374
17%
899
June1st to 15thNight
44%
360
0%
1260
0%
360
44%
360
14%
928
June16th to endNight
50%
360
0%
1260
0%
360
50%
360
19%
856
July1st to 15thNight
62%
340
0%
1190
0%
340
62%
340
21%
767
July16th to endNight
63%
376
7%
1261
6%
354
64%
354
28%
721
August1st to 15thNight
63%
384
7%
1456
11%
382
63%
382
22%
905
August16th to endNight
63%
573
16%
1719
15%
573
65%
573
34%
1007
September1st to 15thNight
56%
658
16%
1801
11%
658
57%
658
32%
1113
September16th to endNight
52%
671
19%
1856
12%
671
57%
671
36%
1140
October1st to 15thNight
44%
660
15%
1953
9%
660
50%
660
23%
1337
October16th to endNight
43%
704
15%
2288
11%
704
50%
704
22%
1523
November1st to 15thNight
35%
834
18%
2415
11%
834
42%
834
23%
1663
November16th to endNight
33%
900
12%
2700
7%
900
38%
900
18%
1964
December1st to 15thNight
35%
900
12%
2700
8%
900
38%
900
15%
2049
December16th to endNight
36%
960
16%
2880
10%
960
42%
960
19%
2073

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
10%8%47%6%35%5%6%8%32%
48042
Night
8%9%47%6%35%5%6%8%32%
46959
TransparencyDay
47%7%17%20%6%
47695
Night
47%7%15%20%7%1
46811
SeeingDay
15%5%24%32%17%5%
6047
Night
12%427%35%16%2
15182

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
7%13%5%8%5%36%447%32%
1253
16th to endDay
6%10%6%11%6%35%5%7%7%29%
1476
February1st to 15thDay
7%12%5%8%7%5%5%46%8%28%
1435
16th to endDay
5%11%7%9%6%37%7%6%7%25%
1488
March1st to 15thDay
5%11%5%9%9%47%6%6%5%28%
1839
16th to endDay
9%13%7%9%7%45%5%6%7%24%
2138
April1st to 15thDay
10%13%6%7%6%45%5%6%7%24%
2245
16th to endDay
14%10%5%7%6%25%5%5%8%28%
2340
May1st to 15thDay
10%9%36%6%46%5%7%8%32%
2568
16th to endDay
19%6%36%6%35%6%5%8%26%
2802
June1st to 15thDay
17%8%36%7%46%6%6%8%25%
2700
16th to endDay
12%6%46%7%46%6%7%8%29%
2700
July1st to 15thDay
11%6%15%5%35%6%7%10%36%
2700
16th to endDay
8%324435%5%8%10%42%
2822
August1st to 15thDay
13%5%25%435%6%6%8%39%
2495
16th to endDay
10%314435%6%7%7%45%
2483
September1st to 15thDay
14%6%245%23446%45%
2157
16th to endDay
9%5%25%435%46%8%43%
1849
October1st to 15thDay
13%9%36%5%36%5%6%7%32%
1675
16th to endDay
7%8%48%6%35%46%8%34%
1584
November1st to 15thDay
7%13%5%8%7%35%5%6%6%30%
1429
16th to endDay
6%11%5%9%6%35%5%5%6%32%
1260
December1st to 15thDay
6%12%6%12%8%5%6%5%5%6%24%
1260
16th to endDay
410%5%11%8%47%6%5%8%28%
1344
January1st to 15thNight
6%12%6%10%10%47%5%5%7%24%
2685
16th to endNight
5%13%48%6%46%5%6%8%30%
2758
February1st to 15thNight
7%11%5%10%6%5%5%45%7%30%
2418
16th to endNight
5%12%6%8%7%48%5%5%6%30%
1983
March1st to 15thNight
5%9%5%9%7%46%7%7%10%27%
2121
16th to endNight
6%12%6%9%8%46%6%6%8%25%
2079
April1st to 15thNight
10%12%5%7%7%46%6%5%7%27%
1703
16th to endNight
13%11%37%7%35%5%5%6%30%
1620
May1st to 15thNight
12%7%45%5%26%6%7%9%34%
1381
16th to endNight
18%7%35%5%246%5%8%31%
1309
June1st to 15thNight
16%8%47%436%7%7%9%24%
1260
16th to endNight
12%6%36%6%446%6%8%32%
1260
July1st to 15thNight
7%6%25%6%47%7%7%9%35%
1260
16th to endNight
7%5%13335%5%7%10%45%
1346
August1st to 15thNight
8%5%35%6%45%5%6%8%40%
1464
16th to endNight
6%5%24425%5%5%8%48%
1719
September1st to 15thNight
12%5%25%42345%7%46%
1801
16th to endNight
10%42342437%8%47%
1856
October1st to 15thNight
11%7%36%6%35%45%7%35%
1953
16th to endNight
7%9%36%6%35%5%7%9%34%
2288
November1st to 15thNight
7%9%47%6%35%5%6%8%35%
2415
16th to endNight
5%11%6%11%7%45%45%7%29%
2700
December1st to 15thNight
5%13%6%11%7%46%5%5%6%26%
2700
16th to endNight
312%5%9%8%45%5%5%8%29%
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
50%5%13%21%6%1
1253
16th to endDay
51%7%13%14%9%3
1476
February1st to 15thDay
51%6%14%18%6%1
1435
16th to endDay
54%7%13%18%6%
1488
March1st to 15thDay
53%6%16%16%6%
1839
16th to endDay
56%7%13%17%5%
2139
April1st to 15thDay
56%6%15%15%5%
2245
16th to endDay
52%5%15%17%6%1
2340
May1st to 15thDay
45%5%17%20%10%
2568
16th to endDay
52%7%17%16%5%
2807
June1st to 15thDay
53%8%14%18%3
2700
16th to endDay
48%9%17%20%3
2700
July1st to 15thDay
40%9%25%21%4
2541
16th to endDay
34%9%24%24%6%
2645
August1st to 15thDay
38%9%25%22%5%
2478
16th to endDay
32%8%23%26%8%1
2483
September1st to 15thDay
39%418%21%12%2
2157
16th to endDay
36%6%14%28%11%2
1849
October1st to 15thDay
47%7%15%20%7%
1675
16th to endDay
46%6%14%24%8%
1584
November1st to 15thDay
51%7%13%18%7%1
1429
16th to endDay
50%6%15%17%7%1
1260
December1st to 15thDay
59%6%12%15%5%
1260
16th to endDay
51%6%14%17%9%
1344
January1st to 15thNight
57%7%11%15%5%2
2685
16th to endNight
49%6%12%19%9%3
2758
February1st to 15thNight
51%6%13%19%8%1
2429
16th to endNight
52%411%17%11%1
1983
March1st to 15thNight
49%9%16%18%6%
2121
16th to endNight
54%6%13%19%5%1
2082
April1st to 15thNight
53%7%13%16%8%
1703
16th to endNight
52%5%13%21%5%1
1620
May1st to 15thNight
43%7%16%20%11%
1382
16th to endNight
48%7%18%18%6%1
1309
June1st to 15thNight
52%9%15%16%5%
1260
16th to endNight
46%8%18%20%5%
1260
July1st to 15thNight
39%10%20%24%4
1190
16th to endNight
32%8%22%27%8%
1261
August1st to 15thNight
38%9%23%22%6%
1456
16th to endNight
31%6%21%27%10%2
1719
September1st to 15thNight
35%5%17%23%13%3
1801
16th to endNight
33%5%17%26%12%4
1856
October1st to 15thNight
46%6%14%22%8%1
1953
16th to endNight
43%7%17%22%7%
2288
November1st to 15thNight
45%7%13%22%10%1
2415
16th to endNight
51%7%15%15%7%3
2700
December1st to 15thNight
57%6%12%18%4
2700
16th to endNight
50%6%12%21%7%1
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
11%6%26%25%20%10%
60
16th to endDay
12%123%29%20%12%
64
February1st to 15thDay
16%419%35%16%7%
67
16th to endDay
14%225%38%17%2
147
March1st to 15thDay
10%6%41%31%9%
270
16th to endDay
13%5%36%31%11%2
288
April1st to 15thDay
19%10%26%28%13%1
269
16th to endDay
23%8%27%25%12%2
270
May1st to 15thDay
11%11%25%28%18%5%
387
16th to endDay
19%5%16%32%22%4
517
June1st to 15thDay
19%5%24%34%13%3
495
16th to endDay
12%6%24%33%17%6%
495
July1st to 15thDay
15%318%33%24%6%
475
16th to endDay
9%422%35%21%7%
491
August1st to 15thDay
14%319%33%18%10%
315
16th to endDay
10%324%37%18%5%
332
September1st to 15thDay
23%324%25%17%6%
315
16th to endDay
10%9%27%33%13%5%
268
October1st to 15thDay
18%7%30%28%11%3
153
16th to endDay
16%413%41%18%5%
96
November1st to 15thDay
19%325%37%10%4
89
16th to endDay
13%6%21%30%15%13%
60
December1st to 15thDay
16%333%23%16%6%
60
16th to endDay
7%425%31%28%3
64
January1st to 15thNight
12%7%32%33%12%1
900
16th to endNight
11%6%33%34%12%2
838
February1st to 15thNight
10%8%25%35%18%2
704
16th to endNight
9%427%35%19%3
632
March1st to 15thNight
9%334%35%14%2
720
16th to endNight
12%428%39%13%2
768
April1st to 15thNight
16%8%27%31%14%1
623
16th to endNight
18%6%25%36%12%
540
May1st to 15thNight
14%430%32%17%
402
16th to endNight
22%420%34%16%1
375
June1st to 15thNight
19%420%35%16%2
360
16th to endNight
15%419%37%21%1
360
July1st to 15thNight
12%213%42%28%
340
16th to endNight
9%218%46%22%1
376
August1st to 15thNight
11%29%38%34%3
384
16th to endNight
9%216%41%28%
573
September1st to 15thNight
16%217%37%22%3
658
16th to endNight
13%326%35%17%3
671
October1st to 15thNight
16%226%36%16%2
660
16th to endNight
12%429%40%12%1
704
November1st to 15thNight
11%7%35%31%11%2
834
16th to endNight
10%5%37%32%12%2
900
December1st to 15thNight
13%5%29%34%14%2
900
16th to endNight
9%333%34%15%3
960
Page generated at 2017-09-20 02:49:54. Version ac04

Copyright 2017 A. Danko


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