Sparwood
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sparwood clear sky chart from 2005-11-05 to 2017-09-24.

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
31%
15164
9%
46880
6%
15131
34%
15131
15%
34745

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
13%
882
4%
2667
2%
877
15%
877
5%
2355
January16th to endNight
17%
768
7%
2688
6%
768
21%
768
8%
2208
February1st to 15thNight
18%
702
6%
2417
3%
698
22%
698
8%
1984
February16th to endNight
24%
632
8%
1935
5%
632
29%
632
11%
1554
March1st to 15thNight
20%
720
5%
2133
3%
720
23%
720
11%
1739
March16th to endNight
27%
768
5%
2069
1%
768
30%
768
12%
1675
April1st to 15thNight
33%
656
8%
1736
3%
656
36%
656
16%
1328
April16th to endNight
34%
540
10%
1620
7%
540
36%
540
17%
1151
May1st to 15thNight
42%
425
9%
1486
10%
425
44%
425
20%
951
May16th to endNight
45%
374
6%
1309
6%
374
46%
374
15%
932
June1st to 15thNight
42%
360
2%
1260
1%
360
43%
360
17%
871
June16th to endNight
46%
360
4%
1260
1%
360
48%
360
22%
786
July1st to 15thNight
62%
340
8%
1190
4%
340
64%
340
38%
581
July16th to endNight
61%
376
16%
1350
18%
354
68%
354
38%
633
August1st to 15thNight
67%
402
19%
1474
23%
400
73%
400
36%
734
August16th to endNight
57%
573
27%
1719
22%
573
60%
573
43%
869
September1st to 15thNight
56%
704
19%
1841
12%
704
58%
704
39%
1089
September16th to endNight
44%
692
16%
1914
11%
692
49%
692
29%
1231
October1st to 15thNight
37%
660
13%
1930
9%
660
41%
660
18%
1387
October16th to endNight
32%
704
10%
2288
7%
704
38%
704
14%
1715
November1st to 15thNight
17%
766
9%
2341
4%
766
22%
766
10%
1879
November16th to endNight
20%
900
5%
2673
3%
900
22%
900
9%
2222
December1st to 15thNight
14%
900
5%
2700
4%
900
16%
900
6%
2354
December16th to endNight
14%
960
5%
2880
2%
960
17%
960
6%
2517

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
9%12%5%8%7%35%5%5%6%29%
48076
Night
6%13%6%10%7%35%45%7%28%
47037
Cloud CoverDay
9%12%5%9%7%45%5%5%6%29%
48077
Night
6%12%6%10%7%35%5%5%7%29%
47040
TransparencyDay
54%7%14%15%6%
47737
Night
54%7%14%16%6%
46880
SeeingDay
19%21%29%19%8%1
5967
Night
14%13%33%26%11%1
15168

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
318%7%16%9%5%7%45%5%15%
1283
16th to endDay
414%10%13%9%36%5%6%7%18%
1536
February1st to 15thDay
5%16%9%14%8%45%5%5%7%18%
1446
16th to endDay
318%8%13%10%46%5%47%16%
1536
March1st to 15thDay
5%19%9%13%7%35%6%5%6%17%
1827
16th to endDay
10%26%8%12%7%4444412%
2153
April1st to 15thDay
10%21%6%10%7%45%5%5%6%16%
2212
16th to endDay
11%16%6%9%6%35%45%5%24%
2340
May1st to 15thDay
12%14%47%7%35%45%6%29%
2460
16th to endDay
21%11%48%7%3445%5%21%
2802
June1st to 15thDay
19%11%47%8%46%5%5%5%21%
2700
16th to endDay
14%7%37%7%46%5%6%6%31%
2700
July1st to 15thDay
7%4245%35%5%6%9%46%
2700
16th to endDay
43144345%5%8%53%
2723
August1st to 15thDay
6%424425%5%6%8%47%
2478
16th to endDay
6%5%14435%45%7%50%
2483
September1st to 15thDay
9%8%35%443345%45%
2118
16th to endDay
10%8%25%5%345%5%6%42%
1904
October1st to 15thDay
10%13%49%8%2446%7%26%
1697
16th to endDay
8%15%5%6%6%46%5%6%6%27%
1584
November1st to 15thDay
10%18%6%11%7%35%445%21%
1506
16th to endDay
5%17%10%12%9%4445%6%20%
1284
December1st to 15thDay
5%19%9%15%9%5%6%335%15%
1260
16th to endDay
315%10%17%11%45%446%15%
1344
January1st to 15thNight
5%20%11%18%10%45%435%10%
2667
16th to endNight
416%10%17%10%46%446%15%
2688
February1st to 15thNight
420%10%16%7%4435%7%15%
2406
16th to endNight
416%8%14%10%45%447%19%
1935
March1st to 15thNight
419%7%13%7%35%45%7%19%
2133
16th to endNight
7%18%7%9%5%45%5%6%7%22%
2066
April1st to 15thNight
9%12%5%7%7%345%6%8%28%
1736
16th to endNight
7%13%48%6%3445%6%35%
1620
May1st to 15thNight
8%12%35%4335%49%37%
1485
16th to endNight
17%7%37%5%26%47%8%29%
1309
June1st to 15thNight
13%7%35%5%35%6%6%8%33%
1260
16th to endNight
11%5%15%5%35%6%7%6%41%
1260
July1st to 15thNight
3223235%6%8%59%
1260
16th to endNight
221332446%8%61%
1444
August1st to 15thNight
4313324449%58%
1482
16th to endNight
431321245%7%63%
1719
September1st to 15thNight
7%42422335%6%56%
1841
16th to endNight
10%6%245%2335%9%45%
1914
October1st to 15thNight
10%10%46%5%35%5%5%7%33%
1930
16th to endNight
7%15%5%9%6%35%5%6%8%25%
2288
November1st to 15thNight
9%17%7%9%6%345%5%7%21%
2341
16th to endNight
5%18%8%16%11%44336%16%
2673
December1st to 15thNight
5%20%8%15%12%5%6%45%5%9%
2700
16th to endNight
319%11%19%10%5%6%436%10%
2880

Percentage Cloud Cover SW (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
216%7%16%10%5%7%5%46%16%
1283
16th to endDay
313%8%14%9%5%6%5%6%7%19%
1536
February1st to 15thDay
5%14%8%14%8%5%5%5%6%6%18%
1446
16th to endDay
316%8%13%9%46%5%5%6%17%
1536
March1st to 15thDay
5%19%8%12%8%5%445%7%18%
1827
16th to endDay
9%25%8%12%8%45%44413%
2154
April1st to 15thDay
9%19%7%10%8%46%5%5%6%16%
2212
16th to endDay
10%16%7%8%7%45%5%45%24%
2340
May1st to 15thDay
10%15%48%6%35%45%6%28%
2460
16th to endDay
20%11%5%9%6%35%446%21%
2802
June1st to 15thDay
18%10%5%8%8%46%5%5%5%21%
2700
16th to endDay
13%7%38%7%46%5%6%6%31%
2700
July1st to 15thDay
6%425%426%5%6%8%45%
2700
16th to endDay
4324435%5%5%8%52%
2723
August1st to 15thDay
6%425%5%35%6%6%9%46%
2478
16th to endDay
7%314425%5%5%7%50%
2483
September1st to 15thDay
9%7%37%434346%44%
2118
16th to endDay
10%8%25%5%335%5%6%42%
1904
October1st to 15thDay
11%12%5%10%7%3446%7%26%
1697
16th to endDay
8%13%47%7%36%5%7%8%27%
1584
November1st to 15thDay
9%16%7%9%7%36%5%46%21%
1506
16th to endDay
416%9%11%9%5%5%447%20%
1284
December1st to 15thDay
5%20%7%14%11%6%6%335%15%
1260
16th to endDay
214%7%17%12%5%5%45%7%15%
1344
January1st to 15thNight
418%10%18%10%5%6%5%35%11%
2667
16th to endNight
314%10%15%12%37%5%46%16%
2688
February1st to 15thNight
419%9%16%8%35%45%8%15%
2406
16th to endNight
314%7%15%10%5%6%447%19%
1935
March1st to 15thNight
418%7%12%9%35%45%7%19%
2133
16th to endNight
7%16%7%9%7%46%5%5%6%23%
2069
April1st to 15thNight
8%12%48%6%35%6%6%8%29%
1736
16th to endNight
6%13%48%6%3445%6%35%
1620
May1st to 15thNight
8%11%45%5%2346%8%37%
1485
16th to endNight
16%8%36%425%5%6%8%29%
1309
June1st to 15thNight
12%7%36%5%35%6%6%7%33%
1260
16th to endNight
10%5%245%36%6%7%7%40%
1260
July1st to 15thNight
23124335%5%8%58%
1260
16th to endNight
2113324449%61%
1444
August1st to 15thNight
33133235%48%57%
1482
16th to endNight
431231336%7%62%
1719
September1st to 15thNight
6%414324345%56%
1841
16th to endNight
10%6%25%42345%8%45%
1914
October1st to 15thNight
9%10%36%6%45%6%5%8%33%
1930
16th to endNight
6%13%5%10%7%35%5%6%9%25%
2288
November1st to 15thNight
9%18%5%8%7%45%6%6%7%21%
2341
16th to endNight
5%17%8%15%9%5%6%445%17%
2673
December1st to 15thNight
419%8%15%11%5%8%5%46%10%
2700
16th to endNight
216%11%19%11%5%6%5%36%10%
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
67%10%11%7%2
1283
16th to endDay
63%10%11%9%31
1536
February1st to 15thDay
64%8%13%8%4
1446
16th to endDay
67%7%12%9%2
1536
March1st to 15thDay
65%8%14%9%1
1827
16th to endDay
75%6%10%5%1
2154
April1st to 15thDay
66%7%14%8%2
2212
16th to endDay
60%7%16%14%
2340
May1st to 15thDay
54%7%15%16%5%
2460
16th to endDay
64%6%15%9%3
2807
June1st to 15thDay
62%7%10%13%5%
2700
16th to endDay
51%8%14%17%8%
2700
July1st to 15thDay
34%7%16%25%15%1
2541
16th to endDay
28%6%12%29%18%3
2554
August1st to 15thDay
31%8%18%28%10%2
2461
16th to endDay
30%7%17%28%13%2
2483
September1st to 15thDay
39%5%14%23%14%2
2118
16th to endDay
41%7%17%22%9%1
1904
October1st to 15thDay
54%9%15%14%5%
1697
16th to endDay
53%10%18%14%2
1584
November1st to 15thDay
62%10%13%11%2
1506
16th to endDay
63%8%15%6%6%
1284
December1st to 15thDay
71%6%9%10%2
1260
16th to endDay
68%7%9%10%4
1344
January1st to 15thNight
76%5%7%6%21
2667
16th to endNight
67%7%10%8%5%1
2688
February1st to 15thNight
69%5%11%9%4
2417
16th to endNight
64%6%10%14%4
1935
March1st to 15thNight
63%7%16%10%1
2133
16th to endNight
59%9%17%10%2
2069
April1st to 15thNight
52%9%17%14%5%
1736
16th to endNight
49%7%18%20%3
1620
May1st to 15thNight
43%6%22%19%8%
1486
16th to endNight
50%9%19%16%4
1309
June1st to 15thNight
46%9%18%18%7%
1260
16th to endNight
37%9%19%24%8%
1260
July1st to 15thNight
20%7%22%31%14%3
1190
16th to endNight
19%7%15%32%20%3
1350
August1st to 15thNight
23%7%17%36%12%2
1474
16th to endNight
20%5%16%38%17%2
1719
September1st to 15thNight
29%5%15%30%16%2
1841
16th to endNight
36%6%20%22%12%1
1914
October1st to 15thNight
47%9%17%18%5%
1930
16th to endNight
54%8%16%17%3
2288
November1st to 15thNight
60%9%11%13%4
2341
16th to endNight
68%5%10%8%41
2673
December1st to 15thNight
74%6%8%7%2
2700
16th to endNight
75%5%8%6%3
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%10%35%25%11%10%
60
16th to endDay
17%25%34%10%7%4
64
February1st to 15thDay
11%20%47%15%4
69
16th to endDay
12%31%31%18%41
195
March1st to 15thDay
27%38%26%6%
270
16th to endDay
28%30%28%11%1
288
April1st to 15thDay
24%26%31%15%2
269
16th to endDay
25%27%27%13%5%1
270
May1st to 15thDay
24%23%28%16%6%1
306
16th to endDay
27%12%23%20%13%2
517
June1st to 15thDay
21%22%23%18%12%1
495
16th to endDay
14%21%26%24%10%2
495
July1st to 15thDay
10%12%28%29%16%1
475
16th to endDay
9%19%40%19%8%2
392
August1st to 15thDay
9%14%35%27%9%3
315
16th to endDay
12%17%38%21%7%3
332
September1st to 15thDay
22%26%25%17%6%1
315
16th to endDay
19%25%32%15%5%
288
October1st to 15thDay
27%23%24%19%5%
178
16th to endDay
20%14%32%22%6%3
96
November1st to 15thDay
32%20%30%16%1
90
16th to endDay
17%14%31%14%14%9%
64
December1st to 15thDay
21%18%28%25%6%
60
16th to endDay
6%20%42%25%41
64
January1st to 15thNight
16%19%43%16%3
882
16th to endNight
10%14%47%21%5%
768
February1st to 15thNight
15%11%42%23%7%
704
16th to endNight
10%11%39%28%8%1
632
March1st to 15thNight
18%17%37%21%5%
720
16th to endNight
18%14%31%26%7%
768
April1st to 15thNight
13%18%27%29%10%1
656
16th to endNight
14%15%27%28%13%
540
May1st to 15thNight
16%12%22%30%15%1
426
16th to endNight
21%8%19%26%23%2
375
June1st to 15thNight
13%13%25%28%17%1
360
16th to endNight
13%8%26%31%17%1
360
July1st to 15thNight
5%7%22%38%24%1
340
16th to endNight
28%22%40%24%1
376
August1st to 15thNight
5%5%16%39%30%2
402
16th to endNight
6%12%21%34%24%1
573
September1st to 15thNight
9%8%20%30%23%7%
704
16th to endNight
13%11%25%29%17%3
692
October1st to 15thNight
18%10%26%32%10%1
660
16th to endNight
14%11%30%33%9%
704
November1st to 15thNight
21%18%38%17%3
766
16th to endNight
16%17%39%20%41
900
December1st to 15thNight
16%14%46%18%4
900
16th to endNight
10%16%46%21%4
960
Page generated at 2017-09-25 06:02:26. Version ac04

Copyright 2017 A. Danko


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