Mount Kobau Star Party
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mount Kobau Star Party clear sky chart from 2005-11-06 to 2024-01-11.

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
40%
22607
14%
74488
9%
22571
46%
22571
22%
48786

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 10thNight
29%
758
7%
2646
4%
756
33%
756
8%
2144
January11th to 20thNight
30%
724
8%
2532
5%
724
36%
724
12%
1940
January21st to endNight
35%
792
7%
2772
4%
792
39%
792
11%
2109
February1st to 10thNight
30%
720
9%
2452
5%
720
37%
720
14%
1789
February11th to 20thNight
35%
701
12%
2274
6%
700
43%
700
18%
1575
February21st to endNight
36%
592
13%
1788
8%
592
44%
592
19%
1249
March1st to 10thNight
37%
720
11%
2160
6%
720
43%
720
19%
1513
March11th to 20thNight
35%
720
15%
2069
7%
720
42%
720
23%
1421
March21st to endNight
31%
792
13%
2012
4%
792
36%
792
22%
1445
April1st to 10thNight
38%
720
14%
1800
4%
720
43%
720
29%
1218
April11th to 20thNight
34%
711
16%
1779
6%
711
40%
711
31%
1170
April21st to endNight
35%
427
18%
1507
12%
427
44%
427
25%
888
May1st to 10thNight
37%
360
18%
1440
13%
360
53%
360
29%
742
May11th to 20thNight
49%
354
14%
1416
16%
354
57%
354
29%
745
May21st to endNight
45%
388
10%
1552
11%
388
50%
388
22%
905
June1st to 10thNight
37%
360
8%
1364
5%
360
41%
360
24%
789
June11th to 20thNight
41%
360
8%
1139
2%
360
43%
360
31%
665
June21st to endNight
49%
360
12%
1164
3%
360
52%
360
43%
586
July1st to 10thNight
56%
350
11%
1266
7%
350
61%
350
42%
587
July11th to 20thNight
50%
348
17%
1392
14%
348
63%
348
44%
586
July21st to endNight
62%
394
25%
1488
29%
372
80%
372
60%
519
August1st to 10thNight
65%
358
24%
1424
30%
356
72%
356
42%
607
August11th to 20thNight
65%
390
33%
1458
31%
390
76%
390
55%
572
August21st to endNight
57%
770
29%
1958
16%
770
64%
770
55%
1021
September1st to 10thNight
54%
720
26%
1800
12%
720
60%
720
51%
983
September11th to 20thNight
59%
720
29%
1814
15%
720
64%
720
48%
1028
September21st to endNight
49%
720
24%
1998
15%
720
57%
720
39%
1148
October1st to 10thNight
47%
720
16%
2160
12%
720
54%
720
31%
1296
October11th to 20thNight
44%
720
19%
2196
12%
720
53%
720
27%
1379
October21st to endNight
40%
792
16%
2574
11%
792
49%
792
23%
1653
November1st to 10thNight
33%
740
11%
2475
8%
740
38%
740
15%
1750
November11th to 20thNight
32%
760
11%
2660
6%
760
39%
760
14%
1909
November21st to endNight
32%
760
8%
2660
3%
760
38%
760
12%
2026
December1st to 10thNight
33%
949
11%
2849
5%
949
39%
949
14%
2137
December11th to 20thNight
26%
949
4%
3507
2%
949
29%
949
7%
2949
December21st to endNight
26%
888
7%
4943
5%
879
34%
879
6%
3743

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
7%9%48%7%46%6%6%7%36%
74983
Night
5%9%47%7%46%6%6%7%39%
74702
TransparencyDay
43%6%15%22%12%3
74682
Night
45%5%16%21%11%2
74521
SeeingDay
14%18%32%25%9%2
13860
Night
13%8%31%32%14%1
22624

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 10thDay
5%14%7%13%10%49%6%6%8%20%
1519
11th to 20thDay
412%5%8%8%47%6%8%9%29%
1440
21st to endDay
411%6%9%8%47%5%6%8%31%
1584
February1st to 10thDay
411%5%8%9%6%7%8%6%8%28%
1504
11th to 20thDay
411%6%8%8%46%6%7%9%30%
1575
21st to endDay
312%7%12%9%6%6%8%7%7%23%
1467
March1st to 10thDay
414%6%9%8%5%7%6%7%7%26%
1800
11th to 20thDay
7%13%5%9%8%5%7%6%6%7%27%
1890
21st to endDay
8%15%6%12%8%48%6%7%7%21%
2344
April1st to 10thDay
8%15%5%8%9%5%6%6%6%7%25%
2160
11th to 20thDay
8%15%5%9%9%46%5%7%7%27%
2132
21st to endDay
7%11%48%7%5%6%6%6%8%32%
2449
May1st to 10thDay
9%9%37%6%46%6%6%8%35%
2520
11th to 20thDay
12%10%38%8%46%5%6%7%31%
2477
21st to endDay
16%10%49%7%5%7%5%5%7%27%
2723
June1st to 10thDay
16%8%47%6%46%6%5%6%31%
2589
11th to 20thDay
13%9%38%8%5%6%7%5%7%28%
2815
21st to endDay
11%6%36%7%46%6%5%8%39%
2788
July1st to 10thDay
6%6%36%7%5%6%5%6%6%45%
2653
11th to 20thDay
6%435%5%25%45%6%54%
2520
21st to endDay
43234245%5%6%60%
2741
August1st to 10thDay
5%325%5%3446%7%56%
2507
11th to 20thDay
5%323435%45%8%58%
2439
21st to endDay
6%5%25%6%46%5%6%7%48%
2397
September1st to 10thDay
7%425%5%34446%56%
2160
11th to 20thDay
8%6%36%7%345%47%46%
2145
21st to endDay
8%8%36%5%445%47%46%
1959
October1st to 10thDay
9%6%47%5%46%45%6%45%
1800
11th to 20thDay
8%7%47%5%45%5%6%7%41%
1764
21st to endDay
12%8%48%7%45%5%6%6%35%
1782
November1st to 10thDay
9%12%5%9%6%37%6%7%7%27%
1603
11th to 20thDay
413%5%8%8%48%5%6%7%31%
1520
21st to endDay
410%5%10%8%5%10%7%6%7%26%
1499
December1st to 10thDay
39%6%9%7%47%7%8%8%31%
1330
11th to 20thDay
38%5%9%10%6%13%9%7%7%23%
1682
21st to endDay
411%6%11%9%7%10%7%7%7%20%
2706
January1st to 10thNight
6%12%6%12%10%7%8%7%5%7%20%
2646
11th to 20thNight
5%11%6%11%10%47%6%6%8%27%
2532
21st to endNight
5%10%5%11%9%47%7%6%7%29%
2772
February1st to 10thNight
5%11%5%9%9%6%6%6%7%6%29%
2452
11th to 20thNight
411%47%7%46%7%6%8%37%
2272
21st to endNight
49%5%12%8%46%7%8%8%29%
1788
March1st to 10thNight
5%11%5%8%7%47%7%7%8%32%
2160
11th to 20thNight
5%9%49%8%46%7%6%7%34%
2068
21st to endNight
7%11%5%8%8%47%6%7%8%30%
2012
April1st to 10thNight
5%10%36%7%5%7%6%6%7%37%
1800
11th to 20thNight
5%10%46%6%47%6%6%6%39%
1779
21st to endNight
6%8%36%6%36%6%6%9%40%
1507
May1st to 10thNight
7%7%25%5%45%5%5%9%47%
1440
11th to 20thNight
7%5%25%7%35%5%8%11%42%
1416
21st to endNight
11%7%35%5%35%6%5%10%39%
1552
June1st to 10thNight
10%7%26%6%45%6%7%8%39%
1364
11th to 20thNight
9%7%25%437%5%6%8%45%
1139
21st to endNight
5%314435%7%7%9%53%
1164
July1st to 10thNight
4223435%45%6%60%
1303
11th to 20thNight
33233235%6%8%63%
1440
21st to endNight
3212222346%74%
1576
August1st to 10thNight
3313424447%63%
1432
11th to 20thNight
231232245%7%68%
1458
21st to endNight
4312325%5%6%9%60%
1958
September1st to 10thNight
5%4134245%47%61%
1800
11th to 20thNight
6%5%1443345%8%57%
1814
21st to endNight
6%6%245%345%6%8%50%
1998
October1st to 10thNight
8%6%25%6%45%5%5%6%46%
2160
11th to 20thNight
8%7%36%6%45%6%6%7%43%
2196
21st to endNight
10%8%36%5%45%6%7%8%39%
2574
November1st to 10thNight
7%12%5%8%6%5%7%5%6%7%33%
2475
11th to 20thNight
6%11%48%7%5%7%6%6%8%33%
2660
21st to endNight
311%6%12%8%5%9%7%6%6%27%
2660
December1st to 10thNight
310%6%10%8%5%6%7%6%6%32%
2849
11th to 20thNight
412%6%12%8%5%12%7%6%6%21%
3510
21st to endNight
413%7%12%10%5%8%5%5%6%24%
4976

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 10thDay
69%6%13%6%5%
1519
11th to 20thDay
57%8%15%15%32
1440
21st to endDay
58%415%17%5%
1584
February1st to 10thDay
52%7%18%16%6%1
1504
11th to 20thDay
48%9%20%18%6%
1584
21st to endDay
51%8%17%16%8%
1467
March1st to 10thDay
49%8%20%15%7%2
1800
11th to 20thDay
48%8%18%20%6%
1890
21st to endDay
53%7%19%15%5%1
2344
April1st to 10thDay
49%7%15%19%8%1
2160
11th to 20thDay
47%6%14%21%10%2
2132
21st to endDay
42%6%15%24%11%2
2449
May1st to 10thDay
38%5%17%27%11%1
2520
11th to 20thDay
42%5%19%24%8%1
2480
21st to endDay
49%5%14%23%8%1
2724
June1st to 10thDay
47%5%14%19%11%5%
2589
11th to 20thDay
46%5%16%24%9%1
2815
21st to endDay
36%5%16%25%16%3
2788
July1st to 10thDay
31%5%12%25%20%7%
2581
11th to 20thDay
25%410%26%27%9%
2445
21st to endDay
17%47%27%35%9%
2589
August1st to 10thDay
23%411%30%22%10%
2490
11th to 20thDay
20%313%33%25%6%
2439
21st to endDay
27%414%34%18%2
2397
September1st to 10thDay
25%315%30%23%4
2160
11th to 20thDay
32%6%14%25%21%4
2145
21st to endDay
34%5%18%26%15%2
1959
October1st to 10thDay
35%5%16%31%12%
1800
11th to 20thDay
39%6%21%24%11%
1764
21st to endDay
48%6%16%24%6%
1782
November1st to 10thDay
53%9%16%15%7%
1603
11th to 20thDay
56%7%15%15%5%2
1520
21st to endDay
58%7%15%14%6%1
1499
December1st to 10thDay
57%7%16%17%3
1330
11th to 20thDay
68%5%13%11%4
1684
21st to endDay
66%6%11%12%4
2706
January1st to 10thNight
70%412%10%4
2646
11th to 20thNight
62%5%14%15%31
2532
21st to endNight
62%415%13%5%
2772
February1st to 10thNight
55%6%17%14%6%2
2452
11th to 20thNight
49%6%17%20%7%
2274
21st to endNight
48%7%18%18%8%1
1788
March1st to 10thNight
49%7%19%15%9%1
2160
11th to 20thNight
45%6%18%22%8%
2069
21st to endNight
48%6%19%20%6%1
2012
April1st to 10thNight
39%7%19%25%9%1
1800
11th to 20thNight
37%7%19%23%13%1
1779
21st to endNight
38%5%16%28%13%1
1507
May1st to 10thNight
31%419%30%15%1
1440
11th to 20thNight
33%425%28%10%1
1416
21st to endNight
39%6%19%28%8%1
1552
June1st to 10thNight
37%5%14%29%12%3
1364
11th to 20thNight
34%5%18%30%13%1
1139
21st to endNight
23%5%21%28%19%4
1164
July1st to 10thNight
23%314%31%20%9%
1266
11th to 20thNight
18%414%28%28%8%
1392
21st to endNight
10%39%31%37%11%
1488
August1st to 10thNight
20%410%28%28%10%
1424
11th to 20thNight
14%314%34%30%6%
1458
21st to endNight
18%314%38%22%3
1958
September1st to 10thNight
21%415%32%24%5%
1800
11th to 20thNight
25%315%28%24%5%
1814
21st to endNight
29%418%32%14%3
1998
October1st to 10thNight
36%417%30%12%1
2160
11th to 20thNight
39%5%18%26%12%
2196
21st to endNight
44%5%18%26%7%
2574
November1st to 10thNight
51%7%18%16%7%1
2475
11th to 20thNight
54%7%17%15%6%2
2660
21st to endNight
62%415%13%6%
2660
December1st to 10thNight
58%5%16%17%4
2849
11th to 20thNight
72%5%10%9%4
3507
21st to endNight
66%412%12%5%1
4976

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 10thDay
17%14%32%23%12%3
180
11th to 20thDay
21%13%28%23%14%1
160
21st to endDay
27%15%25%27%5%1
176
February1st to 10thDay
11%21%48%17%1
224
11th to 20thDay
16%19%41%19%4
335
21st to endDay
9%20%40%23%7%1
341
March1st to 10thDay
19%25%31%19%5%1
420
11th to 20thDay
16%22%32%20%9%1
420
21st to endDay
20%24%31%18%6%2
462
April1st to 10thDay
23%23%30%17%5%2
420
11th to 20thDay
19%27%26%18%7%2
412
21st to endDay
13%27%30%19%8%3
420
May1st to 10thDay
12%23%32%23%8%2
423
11th to 20thDay
17%15%29%24%12%3
448
21st to endDay
16%14%30%26%10%3
485
June1st to 10thDay
17%20%33%24%6%1
519
11th to 20thDay
14%20%30%27%8%1
745
21st to endDay
7%15%36%28%12%2
718
July1st to 10thDay
7%15%34%33%10%1
576
11th to 20thDay
7%18%34%30%9%2
444
21st to endDay
314%36%33%11%3
487
August1st to 10thDay
412%31%35%13%5%
447
11th to 20thDay
5%12%30%33%17%3
437
21st to endDay
7%18%32%29%8%6%
495
September1st to 10thDay
9%17%35%25%10%4
450
11th to 20thDay
13%17%30%25%12%4
450
21st to endDay
15%20%33%20%8%3
450
October1st to 10thDay
14%19%32%21%11%3
450
11th to 20thDay
16%19%27%23%11%3
414
21st to endDay
22%18%30%22%6%2
297
November1st to 10thDay
24%15%31%25%5%
237
11th to 20thDay
21%17%34%20%6%2
180
21st to endDay
16%18%34%20%10%2
180
December1st to 10thDay
21%13%24%26%12%4
180
11th to 20thDay
19%14%36%19%9%2
180
21st to endDay
17%10%36%27%8%2
198
January1st to 10thNight
19%10%32%28%10%2
760
11th to 20thNight
18%7%35%28%10%2
724
21st to endNight
17%6%32%31%12%1
792
February1st to 10thNight
16%7%36%31%9%1
720
11th to 20thNight
12%7%35%32%13%1
704
21st to endNight
12%8%33%32%14%1
592
March1st to 10thNight
14%9%31%31%14%1
720
11th to 20thNight
11%11%34%28%14%1
720
21st to endNight
10%11%35%32%10%1
792
April1st to 10thNight
12%9%31%33%14%1
720
11th to 20thNight
10%9%39%28%12%2
711
21st to endNight
8%13%38%30%9%1
427
May1st to 10thNight
8%9%40%32%11%1
360
11th to 20thNight
8%6%29%34%21%2
354
21st to endNight
11%7%28%39%15%
389
June1st to 10thNight
11%9%36%30%14%
360
11th to 20thNight
12%8%32%38%10%
360
21st to endNight
6%5%34%38%17%
360
July1st to 10thNight
5%5%29%44%17%1
350
11th to 20thNight
35%37%37%18%
348
21st to endNight
26%28%44%20%1
394
August1st to 10thNight
5%420%46%25%1
358
11th to 20thNight
3325%43%25%2
390
21st to endNight
5%5%28%38%23%2
770
September1st to 10thNight
5%8%27%36%23%2
720
11th to 20thNight
9%5%20%33%30%3
720
21st to endNight
11%7%27%35%18%3
720
October1st to 10thNight
14%8%24%33%19%2
720
11th to 20thNight
14%8%26%35%14%3
720
21st to endNight
19%8%28%31%11%2
792
November1st to 10thNight
21%9%31%31%7%
740
11th to 20thNight
21%10%32%23%12%2
760
21st to endNight
19%9%31%26%12%3
760
December1st to 10thNight
17%6%33%32%11%1
949
11th to 20thNight
21%10%34%28%6%1
950
21st to endNight
19%11%35%29%7%
898
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