Owl Hollow
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Owl Hollow 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
49%
24643
25%
74447
16%
24591
58%
24591
36%
42282

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
46%
948
29%
2647
16%
946
57%
946
40%
1466
January11th to 20thNight
38%
923
29%
2583
16%
923
49%
923
36%
1485
January21st to endNight
35%
843
27%
2625
14%
843
51%
843
34%
1500
February1st to 10thNight
35%
720
22%
2340
11%
720
48%
720
30%
1363
February11th to 20thNight
36%
703
23%
2104
12%
700
48%
700
31%
1252
February21st to endNight
36%
592
31%
1776
13%
592
51%
592
33%
1041
March1st to 10thNight
44%
720
24%
2160
13%
720
54%
720
36%
1221
March11th to 20thNight
47%
720
26%
2055
16%
720
53%
720
37%
1204
March21st to endNight
36%
626
22%
2012
11%
626
47%
626
27%
1234
April1st to 10thNight
35%
540
22%
1800
14%
540
48%
540
27%
1035
April11th to 20thNight
35%
533
20%
1777
13%
533
47%
533
25%
1079
April21st to endNight
39%
540
20%
1799
16%
540
48%
540
24%
1117
May1st to 10thNight
46%
540
18%
1620
16%
540
51%
540
25%
1065
May11th to 20thNight
48%
531
16%
1430
13%
531
50%
531
29%
933
May21st to endNight
47%
584
15%
1552
9%
582
52%
582
28%
1035
June1st to 10thNight
63%
540
18%
1440
13%
540
66%
540
43%
831
June11th to 20thNight
59%
540
22%
1440
13%
540
65%
540
42%
827
June21st to endNight
64%
540
24%
1440
17%
540
68%
540
44%
826
July1st to 10thNight
67%
525
16%
1400
13%
525
69%
525
38%
856
July11th to 20thNight
76%
522
26%
1392
22%
522
78%
522
46%
770
July21st to endNight
76%
591
24%
1488
21%
558
75%
558
40%
870
August1st to 10thNight
68%
537
16%
1556
16%
534
68%
534
32%
948
August11th to 20thNight
73%
534
26%
1778
28%
534
76%
534
41%
904
August21st to endNight
71%
594
28%
1980
32%
594
74%
594
40%
1027
September1st to 10thNight
65%
540
28%
1800
27%
540
71%
540
37%
933
September11th to 20thNight
65%
540
33%
1844
32%
540
71%
540
41%
924
September21st to endNight
60%
540
33%
1980
27%
540
70%
540
42%
930
October1st to 10thNight
52%
661
29%
2101
21%
661
60%
661
36%
1146
October11th to 20thNight
53%
720
33%
2160
18%
720
64%
720
49%
1079
October21st to endNight
49%
898
31%
2482
16%
898
57%
898
42%
1402
November1st to 10thNight
52%
925
29%
2405
15%
925
59%
925
46%
1346
November11th to 20thNight
48%
950
34%
2470
16%
950
58%
950
45%
1397
November21st to endNight
47%
950
29%
2565
15%
950
56%
950
42%
1460
December1st to 10thNight
41%
950
25%
2660
12%
950
52%
950
37%
1531
December11th to 20thNight
41%
948
30%
3080
14%
948
52%
948
34%
1666
December21st to endNight
40%
1035
18%
4706
12%
1026
51%
1026
22%
2579

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
6%5%25%4345%6%8%52%
74810
Night
6%5%35%43445%7%53%
74988
TransparencyDay
28%6%11%25%21%8%
74514
Night
29%6%12%26%21%7%
74806
SeeingDay
9%7%24%32%21%7%
14520
Night
8%6%29%41%14%1
24658

By Month

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 10thDay
27%25%5%24348%56%
1518
11th to 20thDay
36%46%5%3446%7%52%
1472
21st to endDay
27%46%5%345%6%7%52%
1746
February1st to 10thDay
47%5%6%7%35%6%5%6%47%
1620
11th to 20thDay
36%37%435%5%7%6%51%
1741
21st to endDay
29%46%5%35%5%46%52%
1480
March1st to 10thDay
46%45%435%5%5%7%54%
1800
11th to 20thDay
6%6%25%5%35%5%5%7%50%
1903
21st to endDay
6%8%26%6%35%5%6%9%44%
2343
April1st to 10thDay
8%7%24435%5%5%7%49%
2160
11th to 20thDay
11%8%26%5%35%5%6%8%42%
2131
21st to endDay
10%7%35%435%5%7%8%43%
2160
May1st to 10thDay
14%6%35%4346%6%7%43%
2340
11th to 20thDay
13%6%26%5%35%5%6%10%39%
2463
21st to endDay
8%5%25%6%36%6%6%10%44%
2724
June1st to 10thDay
6%3244245%8%11%52%
2520
11th to 20thDay
7%3235%345%6%10%53%
2520
21st to endDay
3314435%6%7%9%55%
2520
July1st to 10thDay
7%324435%5%8%9%50%
2520
11th to 20thDay
3213435%5%8%10%55%
2520
21st to endDay
43245%46%7%7%10%47%
2742
August1st to 10thDay
4325%5%45%7%8%11%46%
2372
11th to 20thDay
33134345%7%10%57%
2123
21st to endDay
5%313436%5%6%9%56%
2376
September1st to 10thDay
5%41332445%9%61%
2160
11th to 20thDay
6%2133335%5%7%61%
2114
21st to endDay
7%412323345%65%
1980
October1st to 10thDay
9%6%13322347%59%
1854
11th to 20thDay
6%41332335%6%66%
1800
21st to endDay
7%6%24323346%61%
1854
November1st to 10thDay
342432446%8%59%
1673
11th to 20thDay
46%2342445%8%58%
1710
21st to endDay
27%35%424447%58%
1611
December1st to 10thDay
35%37%5%245%5%8%52%
1520
11th to 20thDay
47%35%5%3445%8%52%
1926
21st to endDay
310%37%6%4445%7%48%
2794
January1st to 10thNight
36%34424447%57%
2647
11th to 20thNight
36%35%43446%7%55%
2583
21st to endNight
37%37%6%3445%6%53%
2625
February1st to 10thNight
37%47%5%35%5%5%7%49%
2340
11th to 20thNight
47%36%5%45%5%6%7%48%
2104
21st to endNight
49%46%6%23345%53%
1776
March1st to 10thNight
46%37%5%3345%7%53%
2160
11th to 20thNight
7%6%34424447%53%
2055
21st to endNight
7%7%46%5%35%46%7%45%
2012
April1st to 10thNight
8%6%36%5%345%5%7%50%
1800
11th to 20thNight
12%7%36%5%34447%46%
1777
21st to endNight
13%7%35%5%345%5%8%42%
1799
May1st to 10thNight
14%6%245%36%6%6%9%40%
1620
11th to 20thNight
17%5%25%32345%9%43%
1429
21st to endNight
9%5%26%5%46%6%6%9%42%
1552
June1st to 10thNight
6%323325%5%7%11%51%
1440
11th to 20thNight
6%3233245%7%9%55%
1440
21st to endNight
5%324435%6%8%8%53%
1440
July1st to 10thNight
7%425%5%35%5%6%8%49%
1440
11th to 20thNight
3214335%6%8%10%55%
1440
21st to endNight
4424436%6%7%10%49%
1576
August1st to 10thNight
5%425%6%36%6%9%10%43%
1564
11th to 20thNight
43245%3445%8%57%
1778
21st to endNight
44244345%6%9%54%
1980
September1st to 10thNight
6%435%335%45%8%54%
1800
11th to 20thNight
7%41342446%6%59%
1844
21st to endNight
7%31332345%5%63%
1980
October1st to 10thNight
10%425%42335%7%56%
2101
11th to 20thNight
7%313313346%65%
2160
21st to endNight
8%5%24423346%58%
2482
November1st to 10thNight
443443345%7%59%
2405
11th to 20thNight
45%2433445%6%59%
2470
21st to endNight
47%3442445%6%57%
2565
December1st to 10thNight
36%45%5%2445%7%55%
2660
11th to 20thNight
46%345%3445%7%56%
3271
21st to endNight
5%8%46%5%345%5%7%48%
4873

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
26%5%13%34%19%4
1519
11th to 20thDay
30%5%12%28%21%4
1472
21st to endDay
30%5%15%27%18%5%
1746
February1st to 10thDay
36%6%12%27%15%5%
1620
11th to 20thDay
31%5%11%28%21%5%
1751
21st to endDay
32%5%9%27%20%6%
1480
March1st to 10thDay
29%5%11%25%23%6%
1800
11th to 20thDay
32%6%13%24%21%6%
1903
21st to endDay
35%6%15%26%14%4
2343
April1st to 10thDay
32%6%14%24%16%9%
2160
11th to 20thDay
38%6%11%22%17%6%
2134
21st to endDay
36%6%11%27%19%2
2160
May1st to 10thDay
38%8%12%26%13%2
2340
11th to 20thDay
39%8%14%24%13%1
2467
21st to endDay
34%9%15%24%14%4
2724
June1st to 10thDay
24%8%19%25%17%7%
2520
11th to 20thDay
26%7%9%22%22%13%
2520
21st to endDay
22%7%10%25%23%12%
2520
July1st to 10thDay
27%8%12%21%21%11%
2451
11th to 20thDay
21%7%11%23%24%13%
2445
21st to endDay
27%9%13%25%18%7%
2590
August1st to 10thDay
28%10%15%24%15%8%
2356
11th to 20thDay
22%6%10%25%25%12%
2123
21st to endDay
23%5%9%22%27%14%
2376
September1st to 10thDay
20%5%7%23%26%19%
2160
11th to 20thDay
21%5%9%20%28%16%
2114
21st to endDay
22%46%23%36%9%
1980
October1st to 10thDay
26%410%22%28%10%
1854
11th to 20thDay
20%410%27%27%13%
1800
21st to endDay
25%49%28%21%12%
1854
November1st to 10thDay
23%5%12%26%24%10%
1673
11th to 20thDay
25%48%28%28%6%
1710
21st to endDay
27%310%23%27%9%
1611
December1st to 10thDay
29%6%12%29%19%6%
1520
11th to 20thDay
30%49%26%28%3
1924
21st to endDay
35%6%8%26%20%4
2794
January1st to 10thNight
27%412%30%22%5%
2647
11th to 20thNight
28%6%11%24%26%5%
2583
21st to endNight
32%5%10%30%19%4
2625
February1st to 10thNight
34%5%14%25%17%4
2340
11th to 20thNight
34%5%11%27%19%4
2104
21st to endNight
34%47%25%22%8%
1776
March1st to 10thNight
29%5%10%24%25%6%
2160
11th to 20thNight
31%5%9%24%27%4
2055
21st to endNight
38%5%14%25%15%3
2012
April1st to 10thNight
34%5%11%25%19%7%
1800
11th to 20thNight
39%5%11%23%17%4
1777
21st to endNight
40%7%9%23%19%2
1799
May1st to 10thNight
38%10%13%24%14%1
1620
11th to 20thNight
38%7%18%24%11%1
1430
21st to endNight
36%11%18%20%9%6%
1552
June1st to 10thNight
25%7%24%27%13%5%
1440
11th to 20thNight
24%8%13%23%20%12%
1440
21st to endNight
25%6%12%28%23%6%
1440
July1st to 10thNight
31%7%13%26%19%5%
1400
11th to 20thNight
21%8%12%28%20%10%
1392
21st to endNight
27%8%16%29%15%5%
1488
August1st to 10thNight
31%9%20%22%12%5%
1556
11th to 20thNight
24%6%13%25%21%11%
1778
21st to endNight
24%7%11%26%23%10%
1980
September1st to 10thNight
27%5%10%20%24%15%
1800
11th to 20thNight
23%5%10%24%24%13%
1844
21st to endNight
22%5%8%25%30%11%
1980
October1st to 10thNight
27%6%11%22%25%10%
2101
11th to 20thNight
21%411%26%25%13%
2160
21st to endNight
28%310%25%23%11%
2482
November1st to 10thNight
24%5%11%23%26%10%
2405
11th to 20thNight
25%410%28%26%7%
2470
21st to endNight
28%49%25%28%7%
2565
December1st to 10thNight
28%6%12%28%18%7%
2660
11th to 20thNight
28%47%32%25%3
3272
21st to endNight
33%6%9%27%20%4
4873

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
5%8%27%37%18%6%
270
11th to 20thDay
10%8%33%36%13%1
252
21st to endDay
412%40%38%5%2
264
February1st to 10thDay
7%11%41%35%41
240
11th to 20thDay
6%10%38%38%7%2
240
21st to endDay
6%13%38%33%10%1
198
March1st to 10thDay
5%11%33%32%15%4
240
11th to 20thDay
11%14%28%32%13%2
343
21st to endDay
11%12%35%32%9%2
462
April1st to 10thDay
14%14%31%27%11%2
420
11th to 20thDay
18%19%30%21%11%2
412
21st to endDay
16%15%25%25%15%5%
420
May1st to 10thDay
17%9%23%30%17%4
603
11th to 20thDay
19%7%21%28%19%6%
625
21st to endDay
11%6%25%29%21%8%
679
June1st to 10thDay
7%5%18%32%26%13%
630
11th to 20thDay
7%427%33%24%4
630
21st to endDay
5%322%35%28%7%
630
July1st to 10thDay
9%111%33%37%10%
621
11th to 20thDay
3214%33%33%14%
618
21st to endDay
5%114%28%39%12%
684
August1st to 10thDay
6%213%32%36%10%
499
11th to 20thDay
3418%34%25%15%
437
21st to endDay
4218%33%33%11%
495
September1st to 10thDay
7%317%37%26%10%
450
11th to 20thDay
6%319%27%32%13%
404
21st to endDay
10%220%27%23%17%
270
October1st to 10thDay
11%6%20%22%24%17%
270
11th to 20thDay
48%29%34%14%11%
270
21st to endDay
9%9%26%32%19%5%
297
November1st to 10thDay
5%10%26%35%16%8%
270
11th to 20thDay
7%10%29%36%14%3
270
21st to endDay
9%7%28%40%13%3
270
December1st to 10thDay
6%13%29%34%16%2
270
11th to 20thDay
7%8%40%36%8%
270
21st to endDay
9%14%31%33%11%2
297
January1st to 10thNight
6%9%32%39%12%2
950
11th to 20thNight
7%9%39%35%9%1
923
21st to endNight
8%5%44%36%6%1
843
February1st to 10thNight
7%8%43%34%8%
720
11th to 20thNight
7%9%40%39%5%
704
21st to endNight
6%10%41%38%4
592
March1st to 10thNight
6%8%34%43%9%
720
11th to 20thNight
9%8%32%40%11%
720
21st to endNight
10%8%40%35%7%1
626
April1st to 10thNight
11%11%37%35%5%
540
11th to 20thNight
15%10%35%33%6%1
533
21st to endNight
17%9%30%32%12%
540
May1st to 10thNight
16%9%24%36%14%1
540
11th to 20thNight
20%424%36%13%2
531
21st to endNight
11%330%39%16%1
584
June1st to 10thNight
7%422%42%24%1
540
11th to 20thNight
8%326%48%14%
540
21st to endNight
6%320%51%20%
540
July1st to 10thNight
7%214%46%30%1
525
11th to 20thNight
3113%51%30%2
522
21st to endNight
6%29%49%34%1
591
August1st to 10thNight
8%213%46%29%2
537
11th to 20thNight
4113%54%26%1
534
21st to endNight
4313%50%29%1
594
September1st to 10thNight
8%418%46%23%2
540
11th to 20thNight
9%418%44%23%3
540
21st to endNight
8%324%43%20%2
540
October1st to 10thNight
13%7%23%35%20%2
661
11th to 20thNight
9%5%30%39%16%1
720
21st to endNight
10%8%27%41%12%1
898
November1st to 10thNight
6%6%32%43%12%1
925
11th to 20thNight
8%9%31%45%7%1
950
21st to endNight
6%8%33%41%11%1
950
December1st to 10thNight
6%8%38%41%6%
950
11th to 20thNight
7%7%36%42%7%1
950
21st to endNight
8%11%34%40%8%1
1045
Page generated at 2024-01-12 05:31:53. Version ac07

Copyright 2024 Attilla Danko


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