Sundre
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sundre clear sky chart from 2005-11-05 to 2017-12-01.

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%
15464
12%
47770
8%
15433
45%
15433
20%
32873

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
31%
898
11%
2685
7%
895
35%
895
14%
2024
January16th to endNight
34%
825
18%
2745
12%
825
42%
825
18%
1878
February1st to 15thNight
39%
699
12%
2442
10%
696
44%
696
16%
1693
February16th to endNight
42%
632
13%
1970
12%
632
47%
632
20%
1368
March1st to 15thNight
35%
720
13%
2133
7%
720
42%
720
20%
1518
March16th to endNight
36%
768
13%
2064
4%
767
41%
767
21%
1489
April1st to 15thNight
34%
635
12%
1715
5%
635
38%
635
18%
1272
April16th to endNight
33%
540
10%
1620
7%
540
37%
540
16%
1193
May1st to 15thNight
43%
383
10%
1379
10%
383
48%
383
20%
891
May16th to endNight
46%
374
3%
1309
2%
374
47%
374
18%
907
June1st to 15thNight
43%
360
0%
1260
0%
360
43%
360
15%
926
June16th to endNight
51%
360
0%
1260
0%
360
51%
360
19%
859
July1st to 15thNight
60%
340
0%
1190
0%
340
60%
340
24%
742
July16th to endNight
63%
376
8%
1276
6%
354
65%
354
27%
743
August1st to 15thNight
62%
372
8%
1444
11%
370
63%
370
21%
897
August16th to endNight
62%
573
17%
1719
15%
573
64%
573
35%
1000
September1st to 15thNight
57%
675
16%
1806
10%
675
58%
675
33%
1143
September16th to endNight
50%
716
19%
1980
11%
716
55%
716
32%
1250
October1st to 15thNight
41%
720
14%
2134
9%
720
46%
720
22%
1474
October16th to endNight
42%
768
17%
2496
11%
768
51%
768
22%
1637
November1st to 15thNight
32%
890
17%
2623
9%
890
40%
890
21%
1815
November16th to endNight
31%
975
14%
2925
5%
975
39%
975
18%
2075
December1st to 15thNight
33%
905
12%
2715
8%
905
36%
905
16%
2025
December16th to endNight
34%
960
15%
2880
8%
960
40%
960
18%
2054

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%47%6%35%5%6%7%32%
48685
Night
8%9%47%6%35%5%6%7%34%
47924
TransparencyDay
48%9%16%18%7%1
48339
Night
45%8%15%20%8%1
47774
SeeingDay
17%7%28%28%13%4
6252
Night
12%6%29%34%15%2
15473

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%11%6%8%5%35%35%7%34%
1253
16th to endDay
5%12%6%9%6%35%5%6%7%30%
1491
February1st to 15thDay
5%11%5%8%7%445%5%9%31%
1421
16th to endDay
411%6%8%7%37%7%7%7%27%
1503
March1st to 15thDay
410%6%9%7%36%5%6%7%31%
1827
16th to endDay
7%13%6%9%7%36%7%6%8%23%
2153
April1st to 15thDay
11%14%6%8%7%36%6%5%6%23%
2233
16th to endDay
14%13%47%6%35%5%5%8%26%
2340
May1st to 15thDay
12%8%46%6%35%6%6%8%30%
2568
16th to endDay
22%7%36%6%35%5%7%8%23%
2802
June1st to 15thDay
21%7%46%6%36%6%6%6%24%
2700
16th to endDay
16%6%36%6%46%6%7%7%27%
2700
July1st to 15thDay
13%425%5%37%6%7%9%34%
2700
16th to endDay
10%3245%36%6%7%8%39%
2804
August1st to 15thDay
15%4144345%7%8%38%
2508
16th to endDay
11%325%5%25%5%6%9%43%
2483
September1st to 15thDay
15%7%1442345%5%44%
2152
16th to endDay
10%6%246%35%447%43%
1980
October1st to 15thDay
15%8%37%435%46%7%34%
1822
16th to endDay
7%8%46%7%35%5%6%8%34%
1728
November1st to 15thDay
6%11%49%7%46%5%47%33%
1548
16th to endDay
6%11%5%7%6%345%5%8%34%
1365
December1st to 15thDay
5%13%6%11%6%5%7%5%5%6%26%
1260
16th to endDay
312%48%8%35%6%6%7%32%
1344
January1st to 15thNight
413%6%10%8%45%6%5%6%27%
2685
16th to endNight
5%12%5%8%6%35%5%6%8%32%
2745
February1st to 15thNight
6%11%49%7%45%5%6%7%31%
2432
16th to endNight
411%48%7%47%45%7%33%
1970
March1st to 15thNight
410%5%7%6%47%6%7%8%29%
2133
16th to endNight
6%10%5%8%6%45%5%7%9%31%
2064
April1st to 15thNight
11%12%48%6%35%5%5%8%29%
1715
16th to endNight
11%11%48%7%35%45%7%29%
1620
May1st to 15thNight
12%10%26%425%5%5%7%36%
1378
16th to endNight
20%7%25%425%5%5%8%32%
1309
June1st to 15thNight
19%7%46%6%36%5%6%6%29%
1260
16th to endNight
12%6%35%6%36%5%6%8%35%
1260
July1st to 15thNight
9%5%25%435%5%7%10%39%
1260
16th to endNight
10%313416%5%9%7%47%
1363
August1st to 15thNight
11%3246%346%6%8%41%
1452
16th to endNight
9%41343435%8%51%
1719
September1st to 15thNight
14%415%42335%6%48%
1806
16th to endNight
12%423425%46%7%46%
1980
October1st to 15thNight
11%8%36%6%24448%36%
2134
16th to endNight
8%8%36%5%35%5%6%8%37%
2496
November1st to 15thNight
6%10%5%7%6%25%6%6%8%35%
2623
16th to endNight
410%5%9%8%45%5%6%7%32%
2925
December1st to 15thNight
412%6%10%8%45%5%5%7%28%
2715
16th to endNight
312%49%8%45%5%7%7%30%
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
48%6%13%22%6%2
1253
16th to endDay
50%7%12%17%9%3
1491
February1st to 15thDay
47%8%15%18%7%2
1421
16th to endDay
50%8%15%16%7%
1503
March1st to 15thDay
48%9%16%16%7%
1827
16th to endDay
55%9%15%13%4
2154
April1st to 15thDay
60%7%13%13%5%
2233
16th to endDay
54%9%14%14%6%1
2340
May1st to 15thDay
48%9%17%16%8%
2568
16th to endDay
55%9%16%12%5%
2807
June1st to 15thDay
57%8%15%14%21
2700
16th to endDay
51%9%17%16%4
2700
July1st to 15thDay
44%11%20%18%4
2541
16th to endDay
38%11%20%21%6%
2628
August1st to 15thDay
40%10%21%21%5%
2491
16th to endDay
35%10%20%25%7%1
2483
September1st to 15thDay
40%6%17%21%11%2
2152
16th to endDay
38%6%15%25%11%2
1980
October1st to 15thDay
47%8%16%18%9%
1822
16th to endDay
43%9%15%21%9%
1728
November1st to 15thDay
49%9%13%18%8%
1548
16th to endDay
44%8%17%17%8%2
1365
December1st to 15thDay
56%7%11%15%8%
1260
16th to endDay
46%8%13%17%12%1
1344
January1st to 15thNight
53%9%11%15%6%2
2685
16th to endNight
46%7%12%19%10%3
2745
February1st to 15thNight
47%9%11%19%9%2
2443
16th to endNight
49%5%12%19%12%1
1970
March1st to 15thNight
47%8%18%18%6%
2133
16th to endNight
47%8%17%18%7%
2067
April1st to 15thNight
52%7%14%17%8%
1715
16th to endNight
53%7%14%19%41
1620
May1st to 15thNight
44%6%16%21%10%
1379
16th to endNight
49%6%18%18%41
1309
June1st to 15thNight
53%8%14%16%6%
1260
16th to endNight
44%9%18%19%5%1
1260
July1st to 15thNight
37%9%21%25%6%
1190
16th to endNight
30%11%19%28%9%
1276
August1st to 15thNight
36%12%21%23%5%
1444
16th to endNight
31%6%20%28%11%2
1719
September1st to 15thNight
34%6%17%21%15%3
1806
16th to endNight
34%7%17%24%12%4
1980
October1st to 15thNight
45%8%15%20%8%1
2134
16th to endNight
41%8%17%23%8%
2496
November1st to 15thNight
44%9%12%22%11%1
2623
16th to endNight
48%8%15%16%7%3
2925
December1st to 15thNight
53%8%12%18%6%
2715
16th to endNight
49%7%12%20%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
10%125%31%18%13%
60
16th to endDay
15%321%29%20%9%
64
February1st to 15thDay
14%10%31%25%12%6%
64
16th to endDay
11%8%30%36%11%1
162
March1st to 15thDay
10%16%43%21%7%
270
16th to endDay
14%16%40%20%5%2
288
April1st to 15thDay
20%17%30%23%7%
269
16th to endDay
25%11%25%28%8%1
270
May1st to 15thDay
15%9%27%28%15%4
372
16th to endDay
24%5%19%29%16%4
517
June1st to 15thDay
21%8%26%28%10%4
495
16th to endDay
18%424%31%16%4
495
July1st to 15thDay
18%321%28%23%4
475
16th to endDay
10%5%28%32%17%4
473
August1st to 15thDay
16%329%30%13%6%
315
16th to endDay
12%5%34%33%11%3
332
September1st to 15thDay
24%425%28%11%5%
315
16th to endDay
15%10%27%26%14%5%
315
October1st to 15thDay
22%8%29%23%10%3
214
16th to endDay
16%7%29%26%16%3
144
November1st to 15thDay
15%6%25%35%13%3
129
16th to endDay
11%12%33%22%13%7%
90
December1st to 15thDay
6%10%38%20%18%6%
60
16th to endDay
46%35%28%17%7%
64
January1st to 15thNight
10%9%35%32%10%1
900
16th to endNight
10%8%34%33%11%1
825
February1st to 15thNight
9%9%27%33%16%3
704
16th to endNight
8%332%33%18%3
632
March1st to 15thNight
8%5%39%34%10%2
720
16th to endNight
11%6%34%32%12%1
768
April1st to 15thNight
14%8%31%31%14%
635
16th to endNight
17%8%28%33%11%
540
May1st to 15thNight
16%6%25%36%14%
384
16th to endNight
23%416%34%20%1
375
June1st to 15thNight
21%421%34%16%2
360
16th to endNight
13%223%36%21%2
360
July1st to 15thNight
12%116%42%24%1
340
16th to endNight
12%218%41%24%1
376
August1st to 15thNight
14%29%36%33%3
372
16th to endNight
10%217%43%24%1
573
September1st to 15thNight
17%217%34%24%4
675
16th to endNight
13%425%35%17%3
716
October1st to 15thNight
17%428%32%15%2
720
16th to endNight
11%5%31%38%11%1
768
November1st to 15thNight
11%8%36%30%11%2
890
16th to endNight
10%7%40%31%7%2
975
December1st to 15thNight
9%7%36%32%12%1
905
16th to endNight
7%6%35%33%14%3
960
Page generated at 2017-12-02 07:14:15. Version ac04

Copyright 2017 A. Danko


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