Onekama-DS-Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Onekama-DS-Observatory clear sky chart from 2005-11-06 to 2024-01-14.

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
30%
24748
12%
74752
7%
24693
34%
24693
15%
56598

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
9%
950
3%
2648
1%
946
10%
946
4%
2414
January11th to 20thNight
12%
918
3%
2569
1%
918
13%
918
5%
2326
January21st to endNight
11%
990
2%
2772
1%
990
12%
990
4%
2565
February1st to 10thNight
11%
830
5%
2396
2%
830
14%
830
6%
2121
February11th to 20thNight
14%
700
7%
2099
2%
700
18%
700
7%
1775
February21st to endNight
17%
592
7%
1776
2%
592
22%
592
8%
1474
March1st to 10thNight
26%
720
14%
2160
7%
720
31%
720
16%
1572
March11th to 20thNight
29%
720
17%
2066
9%
720
36%
720
18%
1496
March21st to endNight
29%
684
17%
2070
10%
684
36%
684
18%
1465
April1st to 10thNight
23%
540
13%
1800
7%
540
31%
540
14%
1302
April11th to 20thNight
29%
533
17%
1724
12%
533
36%
533
18%
1199
April21st to endNight
33%
540
17%
1620
9%
540
41%
540
21%
1110
May1st to 10thNight
33%
540
15%
1620
8%
540
40%
540
21%
1111
May11th to 20thNight
37%
531
17%
1485
10%
531
44%
531
22%
1023
May21st to endNight
48%
583
14%
1552
8%
582
54%
582
32%
996
June1st to 10thNight
46%
540
15%
1440
8%
540
51%
540
30%
946
June11th to 20thNight
47%
540
15%
1440
9%
540
51%
540
30%
936
June21st to endNight
52%
540
15%
1440
9%
540
57%
540
32%
922
July1st to 10thNight
64%
525
16%
1400
11%
525
66%
525
41%
828
July11th to 20thNight
59%
522
18%
1392
11%
522
63%
522
37%
822
July21st to endNight
60%
591
18%
1487
13%
558
62%
558
36%
923
August1st to 10thNight
65%
537
20%
1489
16%
534
67%
534
33%
904
August11th to 20thNight
62%
534
23%
1598
19%
534
66%
534
36%
924
August21st to endNight
53%
594
19%
1944
16%
594
58%
594
28%
1162
September1st to 10thNight
54%
540
20%
1800
18%
540
57%
540
28%
1057
September11th to 20thNight
55%
697
24%
1957
18%
697
59%
697
33%
1225
September21st to endNight
46%
720
17%
1980
13%
720
48%
720
24%
1363
October1st to 10thNight
38%
720
19%
1980
13%
720
43%
720
23%
1370
October11th to 20thNight
26%
720
12%
2251
6%
720
33%
720
13%
1727
October21st to endNight
22%
792
10%
2574
7%
792
27%
792
11%
2027
November1st to 10thNight
24%
740
14%
2406
9%
740
32%
740
13%
1781
November11th to 20thNight
13%
760
9%
2470
5%
760
19%
760
8%
2041
November21st to endNight
16%
826
6%
2536
3%
826
19%
826
7%
2145
December1st to 10thNight
10%
950
2%
2660
1%
950
12%
950
5%
2394
December11th to 20thNight
11%
950
4%
3281
2%
949
13%
949
4%
2906
December21st to endNight
6%
1039
2%
4870
1%
1026
10%
1026
2%
4246

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
14%11%5%8%6%3445%7%33%
74826
Night
15%13%6%9%7%34446%28%
74946
TransparencyDay
51%6%11%20%10%1
74527
Night
58%6%10%17%8%1
74766
SeeingDay
20%14%31%23%10%3
14756
Night
22%12%28%27%11%1
24758

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 10thDay
14%19%12%15%13%5%43339%
1517
11th to 20thDay
17%19%12%18%10%5%42346%
1464
21st to endDay
13%20%14%16%13%5%5%3227%
1584
February1st to 10thDay
10%15%9%16%18%5%5%33312%
1558
11th to 20thDay
13%15%9%14%14%5%5%44315%
1748
21st to endDay
13%16%10%13%11%34435%18%
1480
March1st to 10thDay
14%12%6%9%10%45%5%5%5%27%
1800
11th to 20thDay
12%10%5%9%7%345%5%6%33%
1894
21st to endDay
17%11%5%7%6%3445%7%29%
2299
April1st to 10thDay
18%13%5%8%5%345%47%29%
2160
11th to 20thDay
21%12%35%43435%6%34%
2183
21st to endDay
16%10%46%5%35%46%7%33%
2340
May1st to 10thDay
15%8%26%5%3445%7%40%
2340
11th to 20thDay
15%7%35%5%3445%7%43%
2409
21st to endDay
11%425%446%6%6%8%45%
2725
June1st to 10thDay
12%5%245%35%6%5%7%46%
2520
11th to 20thDay
11%435%5%345%6%9%45%
2520
21st to endDay
12%5%25%4245%6%10%44%
2520
July1st to 10thDay
7%32433446%11%53%
2520
11th to 20thDay
10%323435%5%5%9%51%
2520
21st to endDay
8%424435%5%6%9%50%
2743
August1st to 10thDay
9%425%435%5%7%9%48%
2438
11th to 20thDay
11%4245%4445%8%48%
2303
21st to endDay
12%6%25%5%3446%8%46%
2408
September1st to 10thDay
15%5%25%6%45%447%44%
2160
11th to 20thDay
13%5%25%4235%6%9%46%
1985
21st to endDay
15%6%36%5%25%5%7%8%38%
1980
October1st to 10thDay
17%8%36%5%3445%7%38%
1980
11th to 20thDay
24%15%48%6%5%35%5%6%20%
1704
21st to endDay
26%14%49%7%335%45%20%
1782
November1st to 10thDay
18%17%46%435%35%7%28%
1672
11th to 20thDay
15%23%7%11%6%35%5%47%15%
1710
21st to endDay
20%23%9%10%6%3343416%
1639
December1st to 10thDay
15%23%16%17%6%343239%
1520
11th to 20thDay
15%22%10%16%10%443448%
1918
21st to endDay
21%21%10%11%9%444348%
2783
January1st to 10thNight
15%19%10%18%12%4422311%
2648
11th to 20thNight
15%20%10%16%11%4422311%
2569
21st to endNight
13%19%10%17%14%5%5%3237%
2772
February1st to 10thNight
11%17%9%16%15%5%434312%
2396
11th to 20thNight
13%14%7%16%12%46%445%17%
2098
21st to endNight
16%15%8%14%8%45%35%418%
1776
March1st to 10thNight
14%11%5%8%9%3445%6%31%
2160
11th to 20thNight
12%10%48%6%45%5%5%6%35%
2066
21st to endNight
17%9%48%6%35%45%6%34%
2070
April1st to 10thNight
19%10%5%8%6%2445%6%30%
1800
11th to 20thNight
21%8%36%6%24436%35%
1724
21st to endNight
17%8%46%6%345%46%37%
1620
May1st to 10thNight
15%7%37%6%36%5%6%7%35%
1620
11th to 20thNight
14%8%46%6%45%46%7%36%
1484
21st to endNight
12%5%25%435%5%6%9%45%
1551
June1st to 10thNight
13%6%26%5%345%5%8%43%
1440
11th to 20thNight
10%6%25%6%35%6%7%8%42%
1440
21st to endNight
11%5%25%5%445%5%9%46%
1440
July1st to 10thNight
9%4233245%6%8%54%
1440
11th to 20thNight
8%424435%6%6%8%50%
1440
21st to endNight
6%5%25%5%35%5%6%8%49%
1575
August1st to 10thNight
8%426%5%345%6%9%48%
1498
11th to 20thNight
9%414335%5%5%9%52%
1598
21st to endNight
11%6%35%5%3445%6%48%
1944
September1st to 10thNight
12%6%345%3446%6%48%
1800
11th to 20thNight
12%6%244245%5%7%48%
1957
21st to endNight
15%7%26%6%35%6%47%38%
1980
October1st to 10thNight
19%7%36%5%2435%6%41%
1980
11th to 20thNight
26%12%46%6%33446%26%
2251
21st to endNight
27%13%48%5%34445%23%
2574
November1st to 10thNight
15%16%5%8%6%2345%6%29%
2406
11th to 20thNight
16%23%8%10%6%25%43419%
2470
21st to endNight
18%21%9%11%5%34335%16%
2536
December1st to 10thNight
16%24%13%15%7%3332411%
2660
11th to 20thNight
15%23%10%16%9%3333411%
3279
21st to endNight
23%23%10%11%7%3433410%
4884

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
83%46%6%1
1518
11th to 20thDay
85%4442
1464
21st to endDay
86%4441
1584
February1st to 10thDay
78%5%6%10%1
1558
11th to 20thDay
74%5%8%9%4
1758
21st to endDay
70%5%8%11%41
1480
March1st to 10thDay
58%6%12%16%7%1
1800
11th to 20thDay
50%8%12%19%10%2
1894
21st to endDay
54%6%12%20%7%1
2299
April1st to 10thDay
54%6%10%19%11%
2160
11th to 20thDay
51%5%8%19%15%2
2183
21st to endDay
49%6%12%17%14%2
2340
May1st to 10thDay
44%410%27%12%2
2340
11th to 20thDay
41%5%12%22%16%3
2413
21st to endDay
35%8%14%27%14%2
2725
June1st to 10thDay
35%7%12%28%16%3
2520
11th to 20thDay
35%6%14%25%18%1
2520
21st to endDay
34%7%17%27%15%1
2520
July1st to 10thDay
26%7%14%32%19%2
2451
11th to 20thDay
28%8%15%30%17%2
2445
21st to endDay
30%7%14%29%18%2
2591
August1st to 10thDay
31%7%16%34%11%1
2423
11th to 20thDay
33%6%16%30%13%1
2303
21st to endDay
36%7%14%26%16%2
2408
September1st to 10thDay
41%6%12%27%13%1
2160
11th to 20thDay
35%9%15%30%11%1
1985
21st to endDay
43%7%15%26%9%
1980
October1st to 10thDay
47%5%12%24%11%
1980
11th to 20thDay
65%7%10%15%4
1704
21st to endDay
67%6%11%11%4
1782
November1st to 10thDay
57%6%9%20%8%
1672
11th to 20thDay
70%6%11%9%4
1710
21st to endDay
73%5%11%8%3
1639
December1st to 10thDay
83%45%7%2
1520
11th to 20thDay
80%5%9%5%1
1915
21st to endDay
80%6%7%5%1
2783
January1st to 10thNight
82%46%6%1
2648
11th to 20thNight
81%47%6%2
2569
21st to endNight
84%46%5%1
2772
February1st to 10thNight
78%5%5%10%3
2396
11th to 20thNight
73%48%11%4
2099
21st to endNight
70%5%9%12%4
1776
March1st to 10thNight
53%6%13%21%8%
2160
11th to 20thNight
49%8%11%19%11%2
2066
21st to endNight
51%5%10%23%9%1
2070
April1st to 10thNight
55%6%8%20%11%1
1800
11th to 20thNight
51%5%9%19%13%3
1724
21st to endNight
48%411%20%13%3
1620
May1st to 10thNight
47%6%11%21%12%2
1620
11th to 20thNight
46%6%10%20%15%3
1485
21st to endNight
35%7%14%26%16%2
1552
June1st to 10thNight
39%7%11%27%15%2
1440
11th to 20thNight
36%8%12%24%18%2
1440
21st to endNight
36%7%13%26%16%2
1440
July1st to 10thNight
26%8%14%29%19%4
1400
11th to 20thNight
29%7%14%27%20%3
1392
21st to endNight
32%7%14%28%17%2
1487
August1st to 10thNight
32%8%15%31%11%2
1489
11th to 20thNight
29%6%16%31%17%1
1598
21st to endNight
36%6%13%26%17%1
1944
September1st to 10thNight
35%6%12%24%21%1
1800
11th to 20thNight
34%8%13%32%13%1
1957
21st to endNight
45%6%14%25%9%1
1980
October1st to 10thNight
46%5%9%26%13%1
1980
11th to 20thNight
60%5%11%18%6%1
2251
21st to endNight
64%5%11%14%5%
2574
November1st to 10thNight
56%7%10%18%8%1
2406
11th to 20thNight
70%5%10%10%5%1
2470
21st to endNight
71%6%12%9%2
2536
December1st to 10thNight
80%5%7%7%2
2660
11th to 20thNight
79%5%9%5%2
3281
21st to endNight
79%5%11%41
4884

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
22%21%34%15%6%1
270
11th to 20thDay
29%17%36%15%2
249
21st to endDay
24%20%34%20%21
264
February1st to 10thDay
22%32%33%10%3
240
11th to 20thDay
23%27%37%12%1
240
21st to endDay
28%30%36%6%1
198
March1st to 10thDay
25%29%33%12%1
240
11th to 20thDay
25%16%30%20%9%
334
21st to endDay
30%16%28%19%6%1
462
April1st to 10thDay
27%17%34%18%41
420
11th to 20thDay
29%19%27%14%7%3
412
21st to endDay
25%16%27%22%9%1
420
May1st to 10thDay
21%19%35%17%7%2
423
11th to 20thDay
18%10%38%24%8%3
555
21st to endDay
14%11%33%28%12%3
679
June1st to 10thDay
14%11%34%27%10%4
630
11th to 20thDay
16%10%35%27%9%3
630
21st to endDay
16%8%32%28%13%3
630
July1st to 10thDay
8%6%31%34%16%5%
621
11th to 20thDay
11%9%28%33%14%5%
618
21st to endDay
10%5%34%32%14%5%
684
August1st to 10thDay
11%6%26%31%19%8%
557
11th to 20thDay
13%6%20%30%20%10%
439
21st to endDay
16%8%25%29%18%4
495
September1st to 10thDay
19%8%26%26%15%7%
450
11th to 20thDay
12%8%26%32%17%5%
450
21st to endDay
19%13%24%25%14%6%
450
October1st to 10thDay
21%17%23%23%13%3
450
11th to 20thDay
34%15%32%15%4
302
21st to endDay
37%17%30%11%4
297
November1st to 10thDay
31%16%30%17%5%
270
11th to 20thDay
26%23%36%11%3
270
21st to endDay
31%24%30%12%3
270
December1st to 10thDay
32%20%31%13%31
270
11th to 20thDay
31%24%31%11%3
270
21st to endDay
36%23%28%10%3
297
January1st to 10thNight
25%19%32%18%5%1
950
11th to 20thNight
25%17%32%20%6%
918
21st to endNight
22%13%36%22%6%
990
February1st to 10thNight
21%16%35%24%4
830
11th to 20thNight
22%19%32%22%5%
703
21st to endNight
27%17%32%20%3
592
March1st to 10thNight
19%14%33%25%8%1
720
11th to 20thNight
18%15%34%25%7%
720
21st to endNight
23%11%30%28%8%1
684
April1st to 10thNight
24%12%33%24%6%1
540
11th to 20thNight
26%9%31%25%8%1
533
21st to endNight
21%10%31%29%9%1
540
May1st to 10thNight
20%8%31%31%10%1
540
11th to 20thNight
18%7%31%29%14%1
531
21st to endNight
15%6%26%35%18%1
584
June1st to 10thNight
15%427%38%15%1
540
11th to 20thNight
12%7%26%37%16%2
540
21st to endNight
12%422%41%20%1
540
July1st to 10thNight
12%218%42%24%2
525
11th to 20thNight
8%422%39%25%2
522
21st to endNight
8%422%39%24%3
591
August1st to 10thNight
11%216%48%22%2
537
11th to 20thNight
11%417%36%28%5%
534
21st to endNight
14%5%21%39%20%2
594
September1st to 10thNight
14%6%21%34%22%4
540
11th to 20thNight
14%8%21%33%21%3
697
21st to endNight
19%10%19%30%19%3
720
October1st to 10thNight
22%10%23%29%14%1
720
11th to 20thNight
34%12%23%25%6%1
720
21st to endNight
36%11%26%21%6%1
792
November1st to 10thNight
26%14%30%24%6%1
740
11th to 20thNight
30%18%30%18%4
760
21st to endNight
31%16%29%21%4
826
December1st to 10thNight
30%20%30%17%3
950
11th to 20thNight
30%19%31%15%41
950
21st to endNight
31%16%33%17%2
1045
Page generated at 2024-01-11 04:22:38. Version ac07

Copyright 2024 Attilla Danko


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