Yamabushi Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Yamabushi Observatory 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
47%
15606
23%
47005
15%
15562
56%
15562
28%
29028

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
29%
720
24%
2327
11%
716
45%
716
20%
1432
January16th to endNight
25%
768
25%
2496
10%
768
44%
768
21%
1529
February1st to 15thNight
30%
704
27%
2111
10%
700
48%
700
26%
1279
February16th to endNight
25%
631
26%
1893
9%
631
41%
631
25%
1160
March1st to 15thNight
33%
720
25%
2031
12%
720
44%
720
28%
1269
March16th to endNight
37%
768
22%
2112
11%
768
45%
768
30%
1311
April1st to 15thNight
41%
688
25%
1946
14%
688
50%
688
34%
1140
April16th to endNight
47%
540
25%
1662
15%
540
56%
540
31%
988
May1st to 15thNight
49%
540
20%
1620
11%
540
56%
540
30%
1004
May16th to endNight
58%
561
20%
1683
15%
561
61%
561
30%
1044
June1st to 15thNight
64%
540
16%
1620
13%
540
65%
540
31%
1018
June16th to endNight
72%
540
16%
1620
13%
540
73%
540
34%
990
July1st to 15thNight
67%
510
11%
1530
9%
510
68%
510
25%
1026
July16th to endNight
72%
564
16%
1595
13%
531
74%
531
27%
1042
August1st to 15thNight
64%
539
16%
1609
16%
536
65%
536
25%
1082
August16th to endNight
65%
588
17%
1891
17%
588
66%
588
22%
1284
September1st to 15thNight
63%
720
18%
1980
16%
720
64%
720
27%
1318
September16th to endNight
56%
693
24%
1914
18%
693
62%
693
30%
1238
October1st to 15thNight
51%
660
31%
1853
24%
660
59%
660
33%
1124
October16th to endNight
53%
704
34%
2112
25%
704
66%
704
39%
1151
November1st to 15thNight
52%
700
32%
2224
26%
700
62%
700
37%
1193
November16th to endNight
39%
720
28%
2340
18%
720
53%
720
29%
1340
December1st to 15thNight
38%
720
24%
2340
16%
720
49%
720
24%
1429
December16th to endNight
32%
768
22%
2496
14%
768
44%
768
19%
1637

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
13%5%25%5%35%5%5%7%42%
47914
Night
13%42442445%7%45%
47204
TransparencyDay
39%6%11%20%17%5%
47615
Night
36%5%11%20%19%6%
47007
SeeingDay
16%6%18%23%22%12%
5471
Night
15%8%21%29%21%3
15608

By Month

Percentage Cloud Cover SE (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
17%5%24323435%45%
1611
16th to endDay
19%5%24213345%46%
1728
February1st to 15thDay
15%5%24334445%46%
1747
16th to endDay
17%6%25%423345%45%
1580
March1st to 15thDay
15%42442335%6%46%
1926
16th to endDay
17%41442445%6%44%
2111
April1st to 15thDay
12%5%25%43445%6%46%
2011
16th to endDay
10%4235%2445%7%48%
2296
May1st to 15thDay
11%5%25%435%5%6%7%43%
2331
16th to endDay
11%425%5%46%5%6%9%39%
2431
June1st to 15thDay
8%5%25%7%5%7%6%7%10%33%
2340
16th to endDay
4215%6%47%7%8%11%39%
2340
July1st to 15thDay
9%6%25%6%48%7%8%11%29%
2340
16th to endDay
7%426%6%5%8%7%7%10%32%
2465
August1st to 15thDay
10%5%27%7%47%7%7%9%30%
2340
16th to endDay
13%6%37%7%46%7%6%8%27%
2295
September1st to 15thDay
12%5%36%5%45%5%5%7%38%
1980
16th to endDay
18%5%1432346%6%42%
1905
October1st to 15thDay
14%5%2322324455%
1777
16th to endDay
11%42441222460%
1760
November1st to 15thDay
12%31332343456%
1632
16th to endDay
16%423313346%50%
1620
December1st to 15thDay
19%5%34423445%42%
1620
16th to endDay
25%6%24422235%39%
1728
January1st to 15thNight
17%6%2342433447%
2327
16th to endNight
17%5%24323446%45%
2496
February1st to 15thNight
14%5%23423336%50%
2103
16th to endNight
16%424423345%47%
1893
March1st to 15thNight
14%4244235%45%49%
2031
16th to endNight
13%5%14424347%47%
2112
April1st to 15thNight
13%31332335%8%51%
1946
16th to endNight
11%424424447%49%
1662
May1st to 15thNight
12%414435%46%9%42%
1619
16th to endNight
7%425%6%35%47%9%44%
1682
June1st to 15thNight
7%3345%36%6%7%12%39%
1620
16th to endNight
6%315%5%35%6%7%13%41%
1620
July1st to 15thNight
6%6%35%7%37%5%8%10%35%
1620
16th to endNight
6%225%6%47%6%9%14%33%
1703
August1st to 15thNight
11%5%25%446%5%9%11%32%
1620
16th to endNight
11%5%25%446%6%9%10%32%
1891
September1st to 15thNight
10%5%245%45%5%8%8%38%
1980
16th to endNight
14%424425%45%7%44%
1914
October1st to 15thNight
14%42432344452%
1853
16th to endNight
10%32332434459%
2112
November1st to 15thNight
12%313313235%58%
2224
16th to endNight
15%313413345%51%
2340
December1st to 15thNight
16%5%3442434446%
2340
16th to endNight
21%6%24424346%39%
2496

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
41%49%15%24%5%
1612
16th to endDay
39%27%19%22%8%
1728
February1st to 15thDay
39%38%20%23%4
1749
16th to endDay
41%35%22%20%7%
1580
March1st to 15thDay
38%39%20%20%7%
1926
16th to endDay
39%410%23%17%4
2112
April1st to 15thDay
37%39%20%22%6%
2011
16th to endDay
34%5%8%21%22%6%
2296
May1st to 15thDay
38%5%12%20%19%3
2331
16th to endDay
38%7%13%23%14%2
2435
June1st to 15thDay
40%9%19%20%8%1
2340
16th to endDay
33%10%16%23%13%2
2340
July1st to 15thDay
40%11%17%20%7%2
2201
16th to endDay
40%11%18%19%8%1
2310
August1st to 15thDay
45%9%13%19%9%1
2327
16th to endDay
50%8%14%14%9%1
2295
September1st to 15thDay
42%8%10%18%16%2
1980
16th to endDay
39%6%11%20%17%4
1905
October1st to 15thDay
32%310%19%26%7%
1777
16th to endDay
30%2419%30%11%
1760
November1st to 15thDay
30%36%16%30%11%
1632
16th to endDay
35%37%17%28%7%
1620
December1st to 15thDay
44%37%19%15%9%
1620
16th to endDay
49%27%18%14%7%
1728
January1st to 15thNight
41%26%16%25%6%
2327
16th to endNight
41%2418%23%9%
2496
February1st to 15thNight
37%36%20%23%9%
2112
16th to endNight
38%36%22%22%6%
1893
March1st to 15thNight
37%49%17%21%9%
2031
16th to endNight
35%5%10%21%21%5%
2112
April1st to 15thNight
31%39%24%22%7%
1946
16th to endNight
34%5%8%22%19%9%
1662
May1st to 15thNight
36%5%14%20%19%2
1620
16th to endNight
33%8%13%27%13%2
1684
June1st to 15thNight
33%9%20%24%10%1
1620
16th to endNight
31%9%18%25%13%2
1620
July1st to 15thNight
39%10%20%20%6%2
1530
16th to endNight
34%12%22%20%8%2
1595
August1st to 15thNight
40%8%17%21%9%
1609
16th to endNight
40%11%18%17%10%1
1891
September1st to 15thNight
38%9%15%17%15%3
1980
16th to endNight
37%6%11%21%15%5%
1914
October1st to 15thNight
34%49%18%25%8%
1853
16th to endNight
28%25%18%30%13%
2112
November1st to 15thNight
29%35%17%30%14%
2224
16th to endNight
34%35%18%27%10%
2340
December1st to 15thNight
40%38%20%18%8%
2340
16th to endNight
46%39%15%18%6%
2496

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
27%8%36%18%6%1
90
16th to endDay
21%29%34%12%2
96
February1st to 15thDay
17%17%46%17%
90
16th to endDay
27%13%39%17%2
81
March1st to 15thDay
18%15%27%27%8%1
216
16th to endDay
18%12%29%25%13%1
288
April1st to 15thDay
18%9%25%21%20%3
270
16th to endDay
13%427%27%19%7%
270
May1st to 15thDay
12%11%29%18%14%13%
288
16th to endDay
16%6%16%22%21%16%
331
June1st to 15thDay
10%5%8%28%27%20%
315
16th to endDay
7%117%24%22%26%
315
July1st to 15thDay
10%29%23%29%23%
305
16th to endDay
7%17%24%36%23%
326
August1st to 15thDay
17%5%26%29%20%
313
16th to endDay
17%310%19%30%18%
332
September1st to 15thDay
14%212%18%33%17%
315
16th to endDay
22%211%23%27%13%
287
October1st to 15thDay
22%219%27%20%7%
255
16th to endDay
14%6%18%26%27%7%
272
November1st to 15thDay
25%11%17%25%15%4
140
16th to endDay
15%6%24%33%15%4
90
December1st to 15thDay
30%12%31%17%8%
90
16th to endDay
41%8%30%13%5%1
96
January1st to 15thNight
23%16%26%26%8%
720
16th to endNight
21%17%32%25%3
768
February1st to 15thNight
18%15%31%29%4
704
16th to endNight
18%18%33%25%3
631
March1st to 15thNight
17%13%31%31%6%
720
16th to endNight
16%10%30%28%13%
768
April1st to 15thNight
15%11%30%27%13%1
688
16th to endNight
12%7%25%31%21%1
540
May1st to 15thNight
12%5%25%32%20%3
540
16th to endNight
10%316%29%35%5%
563
June1st to 15thNight
9%114%31%32%10%
540
16th to endNight
7%19%34%36%11%
540
July1st to 15thNight
10%15%28%42%11%
510
16th to endNight
5%17%30%43%11%
564
August1st to 15thNight
14%17%27%38%10%
539
16th to endNight
14%17%25%39%11%
588
September1st to 15thNight
12%19%26%40%8%
720
16th to endNight
18%114%32%29%3
693
October1st to 15thNight
16%5%19%27%26%5%
660
16th to endNight
12%6%22%32%23%2
704
November1st to 15thNight
13%6%22%33%21%1
700
16th to endNight
17%10%27%27%15%1
720
December1st to 15thNight
18%13%23%32%11%1
720
16th to endNight
24%12%25%31%7%
768
Page generated at 2017-09-25 09:02:17. Version ac04

Copyright 2017 A. Danko


Yamabushi Observatory Clear Sky Chart | Charts Home