Cape Orion Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cape Orion Observatory clear sky chart from 2005-11-06 to 2024-01-15.

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
46%
23987
21%
74382
14%
23931
55%
23931
25%
46855

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
28%
760
23%
2459
11%
757
44%
757
23%
1489
January11th to 20thNight
30%
740
24%
2404
11%
740
46%
740
22%
1506
January21st to endNight
25%
792
27%
2574
11%
792
45%
792
24%
1530
February1st to 10thNight
33%
720
25%
2196
12%
720
47%
720
27%
1333
February11th to 20thNight
25%
703
23%
2098
8%
699
40%
699
22%
1357
February21st to endNight
25%
592
22%
1776
10%
592
37%
592
21%
1171
March1st to 10thNight
34%
720
26%
2052
14%
720
44%
720
28%
1260
March11th to 20thNight
32%
720
21%
1980
8%
720
42%
720
25%
1298
March21st to endNight
34%
792
20%
2178
9%
792
43%
792
24%
1431
April1st to 10thNight
38%
720
25%
1980
13%
720
48%
720
32%
1196
April11th to 20thNight
45%
586
25%
1781
14%
586
55%
586
30%
1054
April21st to endNight
54%
540
28%
1620
19%
540
61%
540
34%
957
May1st to 10thNight
50%
540
19%
1620
8%
540
59%
540
30%
994
May11th to 20thNight
49%
531
13%
1593
8%
531
53%
531
23%
1069
May21st to endNight
60%
582
17%
1744
14%
582
61%
582
25%
1151
June1st to 10thNight
62%
540
14%
1620
12%
540
63%
540
23%
1092
June11th to 20thNight
67%
540
14%
1620
11%
540
69%
540
31%
1024
June21st to endNight
72%
540
14%
1620
11%
540
73%
540
28%
1060
July1st to 10thNight
62%
525
9%
1575
8%
525
62%
525
20%
1140
July11th to 20thNight
66%
522
10%
1566
7%
522
67%
522
21%
1121
July21st to endNight
68%
591
13%
1672
11%
558
69%
558
24%
1169
August1st to 10thNight
63%
537
11%
1600
10%
534
64%
534
22%
1116
August11th to 20thNight
60%
534
17%
1598
14%
534
62%
534
21%
1148
August21st to endNight
63%
620
15%
1999
16%
620
63%
620
21%
1366
September1st to 10thNight
64%
720
17%
1980
14%
720
65%
720
26%
1340
September11th to 20thNight
55%
720
18%
1980
15%
720
57%
720
24%
1370
September21st to endNight
57%
720
24%
1980
18%
720
62%
720
30%
1267
October1st to 10thNight
55%
720
26%
1980
20%
720
61%
720
34%
1215
October11th to 20thNight
51%
720
28%
2151
22%
720
59%
720
32%
1279
October21st to endNight
53%
792
32%
2376
24%
792
65%
792
37%
1328
November1st to 10thNight
53%
740
28%
2324
24%
740
61%
740
34%
1301
November11th to 20thNight
42%
760
27%
2470
20%
760
55%
760
30%
1415
November21st to endNight
43%
760
26%
2470
18%
760
54%
760
27%
1483
December1st to 10thNight
35%
760
24%
2470
14%
760
49%
760
21%
1600
December11th to 20thNight
38%
759
29%
2892
18%
758
51%
758
25%
1603
December21st to endNight
31%
829
15%
4384
12%
817
42%
817
12%
2622

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
15%5%245%35%5%6%8%43%
74912
Night
16%5%2443445%7%45%
74888
TransparencyDay
38%8%12%19%17%5%
74635
Night
38%7%11%19%19%6%
74684
SeeingDay
18%10%23%24%17%8%
13879
Night
17%8%22%30%19%4
23997

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
19%5%23324346%50%
1706
11th to 20thDay
19%6%24423445%46%
1662
21st to endDay
18%424333445%51%
1782
February1st to 10thDay
17%5%345%2345%7%45%
1760
11th to 20thDay
22%424423446%44%
1748
21st to endDay
22%6%25%43334443%
1480
March1st to 10thDay
18%42432345%6%50%
1908
11th to 20thDay
21%5%24425%5%5%7%41%
1980
21st to endDay
20%5%245%35%5%5%6%40%
2178
April1st to 10thDay
14%3243346%6%8%47%
1980
11th to 20thDay
15%3246%35%5%47%46%
2142
21st to endDay
13%4244245%5%7%51%
2340
May1st to 10thDay
12%5%246%35%5%5%8%46%
2340
11th to 20thDay
16%6%25%5%46%5%6%8%38%
2301
21st to endDay
13%426%5%35%5%7%10%39%
2531
June1st to 10thDay
13%5%35%6%46%7%8%10%34%
2340
11th to 20thDay
8%4246%48%7%8%11%38%
2340
21st to endDay
9%315%6%5%7%8%8%11%37%
2340
July1st to 10thDay
10%6%37%8%48%8%9%10%29%
2340
11th to 20thDay
10%5%26%7%5%8%8%9%11%29%
2340
21st to endDay
7%436%7%5%9%8%9%11%31%
2547
August1st to 10thDay
13%5%26%7%47%8%7%10%31%
2327
11th to 20thDay
12%425%6%5%7%6%7%11%34%
2303
21st to endDay
13%6%36%6%46%7%8%8%33%
2334
September1st to 10thDay
11%5%26%6%46%6%7%8%39%
1980
11th to 20thDay
16%5%25%6%37%5%5%9%38%
1980
21st to endDay
17%5%24435%45%7%45%
1980
October1st to 10thDay
16%423323346%55%
1980
11th to 20thDay
15%413413345%57%
1807
21st to endDay
15%41431333458%
1980
November1st to 10thDay
14%41431234460%
1749
11th to 20thDay
16%423323346%55%
1710
21st to endDay
17%32442345%6%50%
1710
December1st to 10thDay
24%5%35%43336%5%40%
1710
11th to 20thDay
19%423423446%50%
2153
21st to endDay
25%41232335%7%45%
3124
January1st to 10thNight
21%424433345%49%
2459
11th to 20thNight
19%5%24434446%46%
2404
21st to endNight
17%6%2442334450%
2574
February1st to 10thNight
17%5%24424446%49%
2196
11th to 20thNight
22%5%2433335%5%44%
2098
21st to endNight
22%425%5%34447%40%
1776
March1st to 10thNight
16%5%24424347%49%
2052
11th to 20thNight
17%5%25%5%3445%6%45%
1980
21st to endNight
19%5%25%42445%6%44%
2178
April1st to 10thNight
14%424424445%53%
1980
11th to 20thNight
15%424423446%52%
1781
21st to endNight
12%424423447%53%
1620
May1st to 10thNight
13%325%435%5%6%7%48%
1620
11th to 20thNight
16%5%35%5%36%5%5%8%39%
1592
21st to endNight
14%5%25%6%445%6%8%40%
1744
June1st to 10thNight
11%5%36%5%46%7%8%8%37%
1620
11th to 20thNight
9%4246%35%7%5%11%43%
1620
21st to endNight
9%3246%36%6%8%12%41%
1620
July1st to 10thNight
12%6%36%7%46%6%8%11%30%
1620
11th to 20thNight
10%5%25%7%47%6%10%13%30%
1620
21st to endNight
7%5%37%6%46%9%8%10%35%
1771
August1st to 10thNight
14%6%35%6%45%7%7%10%33%
1611
11th to 20thNight
15%6%46%5%46%6%6%10%33%
1598
21st to endNight
13%5%46%7%45%6%7%10%34%
1999
September1st to 10thNight
13%5%35%6%46%5%7%9%38%
1980
11th to 20thNight
18%6%26%435%5%5%7%39%
1980
21st to endNight
16%425%6%24446%47%
1980
October1st to 10thNight
16%414423446%53%
1980
11th to 20thNight
15%334423445%53%
2151
21st to endNight
15%313323345%58%
2376
November1st to 10thNight
15%32431333458%
2324
11th to 20thNight
17%5%24323335%53%
2470
21st to endNight
18%4234245%5%6%47%
2470
December1st to 10thNight
22%5%34434346%43%
2470
11th to 20thNight
17%5%23323335%54%
3042
21st to endNight
25%5%2442445%7%39%
4532

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
37%5%7%20%23%7%
1707
11th to 20thDay
43%47%18%22%7%
1662
21st to endDay
36%46%22%24%9%
1782
February1st to 10thDay
41%5%8%20%19%7%
1760
11th to 20thDay
41%5%9%18%21%6%
1758
21st to endDay
46%48%14%18%10%
1480
March1st to 10thDay
36%5%8%19%22%11%
1908
11th to 20thDay
43%6%9%16%17%8%
1980
21st to endDay
43%7%10%20%18%3
2178
April1st to 10thDay
33%7%11%21%22%6%
1980
11th to 20thDay
38%6%8%18%21%9%
2142
21st to endDay
32%6%11%27%20%4
2340
May1st to 10thDay
35%8%14%20%19%5%
2340
11th to 20thDay
43%11%14%19%12%2
2305
21st to endDay
38%10%15%22%14%1
2531
June1st to 10thDay
39%13%17%21%7%2
2340
11th to 20thDay
34%12%20%21%11%2
2340
21st to endDay
37%13%16%19%11%3
2340
July1st to 10thDay
43%14%17%17%8%1
2275
11th to 20thDay
41%15%21%13%6%3
2271
21st to endDay
39%15%20%18%8%
2405
August1st to 10thDay
44%12%17%21%6%
2314
11th to 20thDay
42%12%20%19%7%1
2303
21st to endDay
42%12%17%17%9%2
2334
September1st to 10thDay
39%11%14%17%16%3
1980
11th to 20thDay
42%9%12%17%18%2
1980
21st to endDay
37%6%11%21%18%7%
1980
October1st to 10thDay
32%6%10%19%27%7%
1980
11th to 20thDay
31%49%22%23%11%
1807
21st to endDay
31%46%20%27%12%
1980
November1st to 10thDay
30%47%18%29%12%
1749
11th to 20thDay
32%47%21%27%9%
1710
21st to endDay
35%5%7%19%26%8%
1710
December1st to 10thDay
47%46%18%18%7%
1710
11th to 20thDay
35%47%19%22%13%
2150
21st to endDay
38%5%9%20%24%4
3124
January1st to 10thNight
40%38%17%25%7%
2459
11th to 20thNight
41%5%8%17%24%5%
2404
21st to endNight
39%35%18%26%8%
2574
February1st to 10thNight
37%410%21%21%7%
2196
11th to 20thNight
42%46%19%23%6%
2099
21st to endNight
44%49%16%18%9%
1776
March1st to 10thNight
36%5%7%18%22%12%
2052
11th to 20thNight
40%6%11%15%20%7%
1980
21st to endNight
42%5%9%20%20%4
2178
April1st to 10thNight
33%5%10%21%25%6%
1980
11th to 20thNight
34%5%7%21%23%10%
1781
21st to endNight
32%6%11%26%21%3
1620
May1st to 10thNight
34%8%14%22%20%3
1620
11th to 20thNight
41%10%15%20%13%1
1593
21st to endNight
39%11%13%24%12%2
1745
June1st to 10thNight
40%12%17%20%10%2
1620
11th to 20thNight
34%10%21%22%12%1
1620
21st to endNight
32%15%19%18%12%4
1620
July1st to 10thNight
44%13%19%15%8%1
1575
11th to 20thNight
40%17%22%14%6%2
1566
21st to endNight
38%15%21%18%6%1
1672
August1st to 10thNight
43%11%21%18%7%
1600
11th to 20thNight
44%12%16%16%10%1
1598
21st to endNight
43%11%17%20%6%3
1999
September1st to 10thNight
40%10%14%20%12%4
1980
11th to 20thNight
43%9%14%17%16%2
1980
21st to endNight
38%6%10%20%20%6%
1980
October1st to 10thNight
33%6%12%15%27%6%
1980
11th to 20thNight
33%6%9%21%21%10%
2151
21st to endNight
30%46%21%28%12%
2376
November1st to 10thNight
31%48%18%27%12%
2324
11th to 20thNight
35%45%16%28%12%
2470
21st to endNight
36%6%6%20%25%7%
2470
December1st to 10thNight
45%47%18%19%7%
2470
11th to 20thNight
35%48%17%27%9%
3044
21st to endNight
43%6%8%20%18%5%
4532

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
26%19%37%15%3
270
11th to 20thDay
30%19%30%18%4
254
21st to endDay
23%27%35%11%3
264
February1st to 10thDay
23%20%39%15%3
240
11th to 20thDay
38%18%37%8%
240
21st to endDay
34%21%36%8%2
198
March1st to 10thDay
21%17%34%21%7%
348
11th to 20thDay
23%20%32%19%6%1
420
21st to endDay
24%19%28%22%6%1
462
April1st to 10thDay
21%14%28%24%10%2
420
11th to 20thDay
15%16%33%22%12%2
412
21st to endDay
19%10%25%26%15%5%
420
May1st to 10thDay
12%14%31%26%9%7%
423
11th to 20thDay
19%6%20%25%21%9%
447
21st to endDay
16%6%17%27%20%13%
485
June1st to 10thDay
15%416%31%20%13%
450
11th to 20thDay
8%6%15%28%24%19%
450
21st to endDay
10%320%31%21%14%
450
July1st to 10thDay
10%411%26%30%20%
445
11th to 20thDay
8%212%26%31%22%
444
21st to endDay
5%110%30%32%21%
488
August1st to 10thDay
17%314%21%25%19%
446
11th to 20thDay
10%310%28%31%17%
439
21st to endDay
16%311%24%31%15%
495
September1st to 10thDay
10%216%27%33%13%
450
11th to 20thDay
16%414%22%34%11%
450
21st to endDay
18%6%14%31%24%7%
450
October1st to 10thDay
21%5%18%29%19%9%
450
11th to 20thDay
16%8%24%32%18%3
450
21st to endDay
18%8%26%29%15%4
495
November1st to 10thDay
21%7%29%26%14%3
347
11th to 20thDay
18%19%31%27%5%
270
21st to endDay
14%11%38%24%10%1
270
December1st to 10thDay
28%17%32%19%4
270
11th to 20thDay
24%14%36%21%5%1
270
21st to endDay
31%15%32%15%42
297
January1st to 10thNight
21%14%33%26%6%
760
11th to 20thNight
21%12%32%28%6%
740
21st to endNight
21%14%36%26%3
792
February1st to 10thNight
18%13%32%33%5%
720
11th to 20thNight
23%16%33%25%3
703
21st to endNight
22%15%33%26%4
592
March1st to 10thNight
17%12%33%34%4
720
11th to 20thNight
17%12%33%28%9%1
720
21st to endNight
20%12%29%29%10%
792
April1st to 10thNight
15%13%28%33%10%
720
11th to 20thNight
16%11%25%32%15%2
586
21st to endNight
13%7%21%37%21%2
540
May1st to 10thNight
13%7%23%33%22%1
540
11th to 20thNight
17%5%19%31%24%5%
531
21st to endNight
16%210%29%34%9%
584
June1st to 10thNight
13%212%33%34%7%
540
11th to 20thNight
9%214%29%32%15%
540
21st to endNight
9%111%33%38%8%
540
July1st to 10thNight
12%28%24%42%13%
525
11th to 20thNight
11%27%23%41%16%
522
21st to endNight
7%18%28%44%12%
591
August1st to 10thNight
17%17%24%39%12%
537
11th to 20thNight
15%39%27%36%10%
534
21st to endNight
14%37%26%39%12%
620
September1st to 10thNight
13%311%28%37%10%
720
11th to 20thNight
19%213%26%34%6%
720
21st to endNight
17%214%35%28%4
720
October1st to 10thNight
17%5%18%27%26%7%
720
11th to 20thNight
15%6%22%33%20%3
720
21st to endNight
16%7%20%37%18%3
792
November1st to 10thNight
16%6%20%35%19%3
740
11th to 20thNight
18%9%25%34%13%1
760
21st to endNight
19%8%25%33%13%1
760
December1st to 10thNight
24%11%25%32%8%1
760
11th to 20thNight
20%8%29%33%9%1
760
21st to endNight
28%10%26%31%5%
836
Page generated at 2024-01-12 16:17:47. Version ac07

Copyright 2024 Attilla Danko


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