Oak Hills Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Oak Hills Observatory clear sky chart from 2005-11-06 to 2024-01-16.

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
67%
24451
35%
74052
28%
24397
74%
24397
51%
35279

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
52%
757
29%
2457
22%
756
62%
756
36%
1274
January11th to 20thNight
50%
744
36%
2350
23%
744
67%
744
42%
1189
January21st to endNight
48%
792
36%
2376
23%
792
64%
792
35%
1280
February1st to 10thNight
53%
720
35%
2160
25%
720
67%
720
41%
1108
February11th to 20thNight
53%
700
34%
2098
26%
700
65%
700
42%
1085
February21st to endNight
47%
592
30%
1776
24%
592
58%
592
35%
989
March1st to 10thNight
49%
720
25%
2160
20%
720
59%
720
35%
1210
March11th to 20thNight
58%
720
26%
2093
23%
720
64%
720
42%
1126
March21st to endNight
51%
792
29%
2026
16%
792
61%
792
42%
1169
April1st to 10thNight
60%
720
32%
1800
19%
720
67%
720
47%
1013
April11th to 20thNight
55%
711
33%
1779
15%
711
63%
711
52%
951
April21st to endNight
64%
720
35%
1800
18%
720
70%
720
58%
935
May1st to 10thNight
65%
590
34%
1670
21%
590
70%
590
58%
791
May11th to 20thNight
68%
531
36%
1595
27%
531
71%
531
60%
714
May21st to endNight
66%
582
33%
1746
25%
582
70%
582
64%
747
June1st to 10thNight
75%
540
36%
1620
30%
540
77%
540
69%
671
June11th to 20thNight
80%
456
40%
1536
37%
456
84%
456
77%
535
June21st to endNight
91%
360
42%
1440
49%
360
94%
360
77%
432
July1st to 10thNight
96%
350
42%
1400
49%
350
97%
350
79%
416
July11th to 20thNight
85%
475
35%
1519
32%
475
86%
475
66%
616
July21st to endNight
86%
658
35%
1738
27%
622
86%
622
61%
826
August1st to 10thNight
86%
716
37%
1780
24%
712
87%
712
77%
819
August11th to 20thNight
90%
712
40%
1780
25%
712
91%
712
84%
780
August21st to endNight
91%
792
45%
1980
31%
792
92%
792
80%
898
September1st to 10thNight
87%
720
43%
1800
32%
720
88%
720
74%
842
September11th to 20thNight
88%
720
47%
1970
40%
720
92%
720
83%
798
September21st to endNight
81%
720
44%
1980
38%
720
88%
720
75%
844
October1st to 10thNight
75%
720
40%
1980
33%
720
82%
720
63%
931
October11th to 20thNight
74%
720
45%
2026
38%
720
82%
720
65%
900
October21st to endNight
66%
792
41%
2474
35%
792
78%
792
58%
1041
November1st to 10thNight
71%
740
37%
2405
36%
740
79%
740
55%
1029
November11th to 20thNight
67%
760
38%
2470
33%
760
79%
760
55%
1071
November21st to endNight
60%
760
35%
2470
29%
760
71%
760
42%
1210
December1st to 10thNight
55%
760
33%
2470
26%
760
66%
760
39%
1254
December11th to 20thNight
52%
760
30%
2944
25%
759
64%
759
27%
1626
December21st to endNight
47%
829
20%
4384
23%
817
61%
817
21%
2159

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
1212323346%72%
75353
Night
121332445%6%68%
74488
TransparencyDay
15%37%15%28%32%
75077
Night
17%48%14%27%30%
74287
SeeingDay
5%16%34%29%12%4
14545
Night
37%19%34%28%7%
24467

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
34244345%5%8%59%
1708
11th to 20thDay
331222345%8%65%
1734
21st to endDay
4425%42445%6%60%
1980
February1st to 10thDay
2324424447%66%
1800
11th to 20thDay
2225%324447%64%
1750
21st to endDay
23245%35%5%47%60%
1480
March1st to 10thDay
2424436%6%6%9%55%
1800
11th to 20thDay
232343447%8%62%
1866
21st to endDay
12133246%7%7%64%
2326
April1st to 10thDay
222322435%8%65%
2160
11th to 20thDay
1112213446%74%
2129
21st to endDay
2111222348%74%
2160
May1st to 10thDay
111121236%8%74%
2287
11th to 20thDay
1111212348%77%
2301
21st to endDay
1112212246%77%
2530
June1st to 10thDay
111212237%79%
2340
11th to 20thDay
11122489%
2416
21st to endDay
111211212386%
2520
July1st to 10thDay
1112212335%81%
2520
11th to 20thDay
1112222346%77%
2386
21st to endDay
111232345%7%70%
2473
August1st to 10thDay
211121222383%
2149
11th to 20thDay
111113236%81%
2122
21st to endDay
111212336%79%
2376
September1st to 10thDay
112222246%77%
2160
11th to 20thDay
11122488%
1989
21st to endDay
111122235%82%
1980
October1st to 10thDay
1113313346%76%
1980
11th to 20thDay
111122232481%
1930
21st to endDay
111212237%80%
1882
November1st to 10thDay
1112324346%73%
1674
11th to 20thDay
121321335%6%73%
1710
21st to endDay
2213434448%65%
1710
December1st to 10thDay
321343445%9%61%
1710
11th to 20thDay
2426%5%35%6%7%10%49%
2169
21st to endDay
4425%7%47%5%6%8%48%
3146
January1st to 10thNight
2325%5%35%5%5%7%58%
2457
11th to 20thNight
24134345%5%7%62%
2350
21st to endNight
4335%434447%60%
2376
February1st to 10thNight
2325%42445%5%64%
2160
11th to 20thNight
23245%335%5%6%63%
2098
21st to endNight
2225%5%35%5%6%8%57%
1776
March1st to 10thNight
13245%46%6%9%8%53%
2160
11th to 20thNight
12135%45%6%6%8%58%
2093
21st to endNight
1225%5%45%5%6%8%59%
2026
April1st to 10thNight
1314335%5%6%9%61%
1800
11th to 20thNight
1212435%45%8%65%
1779
21st to endNight
21123235%7%6%70%
1800
May1st to 10thNight
1121448%9%69%
1670
11th to 20thNight
1122136%6%8%71%
1594
21st to endNight
11121246%7%74%
1746
June1st to 10thNight
1221245%5%78%
1620
11th to 20thNight
1111335%85%
1536
21st to endNight
1111223486%
1440
July1st to 10thNight
11122488%
1440
11th to 20thNight
112323335%78%
1570
21st to endNight
2113323345%73%
1840
August1st to 10thNight
111112222483%
1790
11th to 20thNight
11111123485%
1780
21st to endNight
11111223483%
1980
September1st to 10thNight
111221222482%
1800
11th to 20thNight
111223486%
1970
21st to endNight
111111333382%
1980
October1st to 10thNight
2112323246%75%
1980
11th to 20thNight
113212335%79%
2026
21st to endNight
11222245%5%76%
2474
November1st to 10thNight
1111323446%72%
2405
11th to 20thNight
11232336%7%71%
2470
21st to endNight
2214435%5%6%8%61%
2470
December1st to 10thNight
33244235%6%9%59%
2470
11th to 20thNight
3325%436%6%7%10%50%
3041
21st to endNight
3325%7%5%7%7%8%7%47%
4521

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
24%48%20%26%17%
1709
11th to 20thDay
19%5%9%14%32%20%
1734
21st to endDay
29%38%16%24%20%
1980
February1st to 10thDay
21%46%16%25%27%
1800
11th to 20thDay
23%36%13%30%23%
1760
21st to endDay
25%49%16%26%20%
1480
March1st to 10thDay
27%410%17%24%18%
1800
11th to 20thDay
22%49%19%27%19%
1866
21st to endDay
20%6%10%23%26%14%
2326
April1st to 10thDay
21%48%23%28%16%
2160
11th to 20thDay
16%37%19%31%23%
2132
21st to endDay
14%39%21%37%16%
2160
May1st to 10thDay
12%410%21%31%22%
2287
11th to 20thDay
10%29%18%39%21%
2304
21st to endDay
12%37%20%41%17%
2530
June1st to 10thDay
10%26%14%35%33%
2340
11th to 20thDay
5%2410%29%51%
2416
21st to endDay
8%14422%61%
2520
July1st to 10thDay
8%246%17%63%
2451
11th to 20thDay
10%37%14%25%41%
2314
21st to endDay
13%5%9%16%28%30%
2336
August1st to 10thDay
7%26%7%21%57%
2135
11th to 20thDay
7%2413%24%50%
2122
21st to endDay
9%25%7%29%48%
2376
September1st to 10thDay
10%36%8%23%50%
2160
11th to 20thDay
5%149%30%52%
1989
21st to endDay
8%2411%31%44%
1980
October1st to 10thDay
13%35%14%26%38%
1980
11th to 20thDay
10%25%10%31%42%
1930
21st to endDay
10%3410%28%44%
1882
November1st to 10thDay
15%36%14%33%30%
1674
11th to 20thDay
15%38%12%27%35%
1710
21st to endDay
21%37%13%26%29%
1710
December1st to 10thDay
23%49%18%23%23%
1710
11th to 20thDay
29%9%12%14%23%14%
2168
21st to endDay
33%7%8%21%20%11%
3146
January1st to 10thNight
25%5%9%16%27%17%
2457
11th to 20thNight
22%6%8%15%27%22%
2350
21st to endNight
27%410%14%25%21%
2376
February1st to 10thNight
25%28%14%23%28%
2160
11th to 20thNight
23%47%15%27%24%
2099
21st to endNight
27%7%7%15%23%21%
1776
March1st to 10thNight
27%6%11%17%21%17%
2160
11th to 20thNight
22%7%10%16%26%18%
2093
21st to endNight
25%5%11%21%26%12%
2026
April1st to 10thNight
22%5%10%23%23%17%
1800
11th to 20thNight
18%5%9%20%28%21%
1779
21st to endNight
16%49%19%36%16%
1800
May1st to 10thNight
13%5%10%21%28%22%
1670
11th to 20thNight
14%310%19%37%17%
1595
21st to endNight
12%312%22%38%14%
1746
June1st to 10thNight
10%26%15%33%33%
1620
11th to 20thNight
6%2411%30%47%
1536
21st to endNight
6%15%421%63%
1440
July1st to 10thNight
5%138%17%66%
1400
11th to 20thNight
11%36%13%24%42%
1519
21st to endNight
14%47%16%29%30%
1738
August1st to 10thNight
8%248%25%53%
1780
11th to 20thNight
5%25%11%27%50%
1780
21st to endNight
7%248%31%49%
1980
September1st to 10thNight
9%36%5%27%51%
1800
11th to 20thNight
5%147%34%48%
1970
21st to endNight
8%2410%30%45%
1980
October1st to 10thNight
14%25%13%28%37%
1980
11th to 20thNight
11%3310%33%40%
2026
21st to endNight
13%26%8%25%46%
2474
November1st to 10thNight
15%36%12%32%31%
2405
11th to 20thNight
15%37%12%28%35%
2470
21st to endNight
22%5%8%15%22%28%
2470
December1st to 10thNight
24%5%7%14%24%25%
2470
11th to 20thNight
28%9%10%15%24%14%
3041
21st to endNight
27%8%12%19%24%10%
4521

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
9%23%33%28%7%1
270
11th to 20thDay
10%19%33%28%9%1
322
21st to endDay
12%29%29%21%8%1
462
February1st to 10thDay
6%28%31%24%9%2
420
11th to 20thDay
11%27%35%21%5%1
415
21st to endDay
10%31%34%21%4
346
March1st to 10thDay
11%32%35%14%8%
420
11th to 20thDay
10%25%35%21%8%1
420
21st to endDay
11%30%35%18%5%
462
April1st to 10thDay
8%21%36%22%11%2
420
11th to 20thDay
7%28%38%16%8%2
412
21st to endDay
5%24%33%23%9%5%
420
May1st to 10thDay
5%21%38%24%9%4
423
11th to 20thDay
218%42%25%8%4
448
21st to endDay
5%15%39%27%8%5%
485
June1st to 10thDay
216%35%28%13%6%
450
11th to 20thDay
19%40%31%13%6%
450
21st to endDay
28%35%36%11%7%
450
July1st to 10thDay
1437%36%14%8%
446
11th to 20thDay
1228%42%17%9%
444
21st to endDay
1129%38%18%13%
487
August1st to 10thDay
2439%31%14%10%
447
11th to 20thDay
2232%35%17%13%
437
21st to endDay
2231%39%16%10%
495
September1st to 10thDay
2336%37%17%5%
450
11th to 20thDay
28%38%33%16%2
450
21st to endDay
215%31%32%17%3
450
October1st to 10thDay
414%35%32%15%1
450
11th to 20thDay
311%37%32%15%2
450
21st to endDay
316%35%30%15%2
397
November1st to 10thDay
317%27%37%14%1
270
11th to 20thDay
319%32%29%13%4
270
21st to endDay
5%17%33%29%13%3
270
December1st to 10thDay
6%19%33%32%9%1
270
11th to 20thDay
7%22%29%28%13%1
270
21st to endDay
11%26%30%23%9%1
297
January1st to 10thNight
7%13%23%33%19%5%
760
11th to 20thNight
5%11%30%32%18%4
744
21st to endNight
10%14%23%32%18%3
792
February1st to 10thNight
6%13%24%33%19%5%
720
11th to 20thNight
5%14%25%34%17%5%
704
21st to endNight
6%14%32%30%16%3
592
March1st to 10thNight
5%15%27%34%18%2
720
11th to 20thNight
311%25%32%23%6%
720
21st to endNight
412%28%34%19%3
792
April1st to 10thNight
49%22%38%22%5%
720
11th to 20thNight
311%28%32%22%4
711
21st to endNight
37%25%35%23%7%
720
May1st to 10thNight
17%26%42%21%4
590
11th to 20thNight
16%22%36%29%6%
531
21st to endNight
26%25%36%26%5%
584
June1st to 10thNight
1419%41%31%5%
540
11th to 20thNight
117%43%35%4
456
21st to endNight
115%39%45%9%
360
July1st to 10thNight
329%56%13%
350
11th to 20thNight
28%33%49%8%
475
21st to endNight
116%33%48%11%
658
August1st to 10thNight
219%31%44%14%
716
11th to 20thNight
16%27%50%16%
712
21st to endNight
25%27%50%17%
792
September1st to 10thNight
127%28%47%15%
720
11th to 20thNight
110%35%40%13%
720
21st to endNight
1314%33%38%11%
720
October1st to 10thNight
2416%43%29%5%
720
11th to 20thNight
2417%36%32%9%
720
21st to endNight
19%20%33%24%12%
792
November1st to 10thNight
28%16%38%28%8%
740
11th to 20thNight
26%23%37%25%8%
760
21st to endNight
48%24%36%22%6%
760
December1st to 10thNight
6%10%25%35%20%5%
760
11th to 20thNight
6%13%25%34%20%3
760
21st to endNight
7%16%26%33%16%3
836
Page generated at 2024-01-13 16:28:30. Version ac07

Copyright 2024 Attilla Danko


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