Oracle State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Oracle State Park clear sky chart from 2005-11-05 to 2018-01-20.

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
71%
16045
35%
48447
29%
16007
78%
16007
49%
23926

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
69%
778
32%
2522
29%
776
76%
776
44%
1239
January16th to endNight
64%
788
36%
2561
33%
788
73%
788
37%
1343
February1st to 15thNight
66%
700
35%
2221
31%
700
77%
700
47%
1074
February16th to endNight
59%
632
37%
1829
31%
632
68%
632
43%
979
March1st to 15thNight
61%
720
38%
1980
28%
720
71%
720
49%
1033
March16th to endNight
67%
768
38%
2112
26%
768
77%
768
55%
1046
April1st to 15thNight
59%
674
34%
1933
21%
674
71%
674
49%
959
April16th to endNight
64%
540
45%
1791
34%
540
80%
540
65%
675
May1st to 15thNight
68%
539
39%
1619
28%
539
79%
539
62%
696
May16th to endNight
69%
561
41%
1684
30%
561
77%
561
67%
698
June1st to 15thNight
79%
540
34%
1620
28%
540
82%
540
66%
695
June16th to endNight
82%
540
31%
1620
27%
540
84%
540
57%
747
July1st to 15thNight
81%
510
20%
1530
17%
510
81%
510
39%
868
July16th to endNight
78%
564
17%
1593
15%
531
78%
531
30%
1009
August1st to 15thNight
86%
539
24%
1611
23%
536
86%
536
41%
904
August16th to endNight
84%
576
30%
1858
32%
576
84%
576
39%
999
September1st to 15thNight
77%
720
29%
1980
25%
720
78%
720
42%
1158
September16th to endNight
79%
716
43%
1980
32%
716
84%
716
63%
941
October1st to 15thNight
75%
720
39%
2100
29%
720
82%
720
62%
955
October16th to endNight
82%
768
45%
2304
38%
768
88%
768
65%
998
November1st to 15thNight
76%
760
41%
2280
34%
760
83%
760
58%
1043
November16th to endNight
70%
780
39%
2480
37%
780
76%
780
48%
1192
December1st to 15thNight
64%
780
36%
2535
33%
780
71%
780
43%
1261
December16th to endNight
61%
832
35%
2704
33%
832
69%
832
38%
1414

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
321232345%6%64%
49078
Night
2212323346%66%
48643
TransparencyDay
21%4412%28%28%
48773
Night
20%3414%28%28%
48449
SeeingDay
6%11%26%33%17%4
5779
Night
4414%35%33%7%
16054

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 15thDay
3214424347%62%
1746
16th to endDay
4323323345%62%
1766
February1st to 15thDay
3313222445%65%
1640
16th to endDay
4213425%346%61%
1644
March1st to 15thDay
323433337%64%
1980
16th to endDay
222212235%73%
2112
April1st to 15thDay
1112213445%71%
2015
16th to endDay
1111213480%
2166
May1st to 15thDay
1121334377%
2331
16th to endDay
11111122479%
2429
June1st to 15thDay
11111213478%
2340
16th to endDay
1111212346%71%
2340
July1st to 15thDay
4213436%6%9%10%46%
2340
16th to endDay
6%425%6%46%7%9%11%33%
2467
August1st to 15thDay
6%4245%36%7%7%10%43%
2340
16th to endDay
43145%36%5%7%9%48%
2339
September1st to 15thDay
6%3235%35%5%6%7%49%
1980
16th to endDay
31122333471%
1980
October1st to 15thDay
211212335%74%
1860
16th to endDay
12212345%75%
1920
November1st to 15thDay
112212346%72%
1909
16th to endDay
2212223235%71%
1807
December1st to 15thDay
431333335%6%61%
1755
16th to endDay
32134235%6%7%58%
1872
January1st to 15thNight
3312323346%64%
2522
16th to endNight
5%3135%2345%6%59%
2561
February1st to 15thNight
3212313346%66%
2210
16th to endNight
32124245%5%6%60%
1829
March1st to 15thNight
2212314346%66%
1980
16th to endNight
2111123245%72%
2112
April1st to 15thNight
222224445%69%
1933
16th to endNight
1111112384%
1791
May1st to 15thNight
1112247%76%
1619
16th to endNight
2111112383%
1684
June1st to 15thNight
1111222480%
1620
16th to endNight
112213335%73%
1620
July1st to 15thNight
23135%26%6%8%11%48%
1620
16th to endNight
34245%47%7%10%14%35%
1701
August1st to 15thNight
3212335%7%7%11%51%
1620
16th to endNight
2113435%5%7%12%51%
1858
September1st to 15thNight
3315%42446%7%55%
1980
16th to endNight
112112335%75%
1980
October1st to 15thNight
11121233475%
2100
16th to endNight
11211123478%
2304
November1st to 15thNight
112213236%73%
2280
16th to endNight
4112323345%68%
2480
December1st to 15thNight
421332335%6%62%
2535
16th to endNight
4214424446%58%
2704

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
25%4312%31%22%
1747
16th to endDay
26%3216%27%23%
1766
February1st to 15thDay
22%3314%28%28%
1640
16th to endDay
24%4114%33%21%
1644
March1st to 15thDay
22%37%36%29%
1980
16th to endDay
17%2110%37%30%
2112
April1st to 15thDay
16%37%40%30%
2015
16th to endDay
11%119%30%45%
2166
May1st to 15thDay
13%218%30%43%
2331
16th to endDay
11%218%32%43%
2432
June1st to 15thDay
12%2424%55%
2340
16th to endDay
15%327%21%50%
2340
July1st to 15thDay
29%8%13%16%14%17%
2201
16th to endDay
40%9%18%21%8%1
2312
August1st to 15thDay
35%8%9%18%19%9%
2325
16th to endDay
30%7%11%17%21%11%
2339
September1st to 15thDay
33%5%7%19%18%15%
1980
16th to endDay
17%4110%35%29%
1980
October1st to 15thDay
15%3213%30%34%
1860
16th to endDay
12%3210%30%39%
1920
November1st to 15thDay
14%3114%37%29%
1909
16th to endDay
18%2111%30%34%
1807
December1st to 15thDay
25%3317%31%19%
1755
16th to endDay
25%5%419%31%13%
1872
January1st to 15thNight
22%4312%31%24%
2522
16th to endNight
28%3116%29%20%
2561
February1st to 15thNight
20%3315%26%29%
2221
16th to endNight
24%4214%33%20%
1829
March1st to 15thNight
20%3110%31%31%
1980
16th to endNight
17%3112%36%28%
2112
April1st to 15thNight
19%319%41%25%
1933
16th to endNight
8%210%33%44%
1791
May1st to 15thNight
10%3110%33%39%
1620
16th to endNight
10%119%28%48%
1685
June1st to 15thNight
11%215%20%59%
1620
16th to endNight
15%325%19%53%
1620
July1st to 15thNight
27%6%15%17%15%17%
1530
16th to endNight
35%8%21%22%8%2
1593
August1st to 15thNight
25%7%14%20%18%13%
1611
16th to endNight
26%6%14%18%21%13%
1858
September1st to 15thNight
27%6%8%22%20%15%
1980
16th to endNight
13%3213%36%30%
1980
October1st to 15thNight
14%2215%28%37%
2100
16th to endNight
12%2212%28%41%
2304
November1st to 15thNight
15%3115%34%29%
2280
16th to endNight
20%3311%25%35%
2480
December1st to 15thNight
24%2317%31%20%
2535
16th to endNight
27%35%17%28%17%
2704

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
8%9%26%42%11%1
135
16th to endDay
8%11%28%31%16%4
109
February1st to 15thDay
9%10%25%40%12%1
155
16th to endDay
8%26%35%22%6%
238
March1st to 15thDay
8%24%32%18%13%2
270
16th to endDay
6%26%29%23%10%2
288
April1st to 15thDay
9%26%31%20%8%3
269
16th to endDay
7%26%38%19%5%1
270
May1st to 15thDay
6%19%43%17%11%2
288
16th to endDay
314%39%31%9%
330
June1st to 15thDay
49%40%29%12%3
315
16th to endDay
5%231%37%21%1
315
July1st to 15thDay
5%16%48%25%3
305
16th to endDay
9%13%38%26%11%
327
August1st to 15thDay
8%27%41%29%9%
315
16th to endDay
429%45%29%8%
332
September1st to 15thDay
9%319%43%18%6%
315
16th to endDay
49%28%38%15%3
315
October1st to 15thDay
48%29%34%18%4
195
16th to endDay
322%36%33%3
144
November1st to 15thDay
213%21%38%21%2
135
16th to endDay
212%27%32%22%2
135
December1st to 15thDay
5%9%25%38%19%1
135
16th to endDay
6%15%20%35%18%4
144
January1st to 15thNight
5%316%44%25%5%
780
16th to endNight
7%7%16%38%24%4
788
February1st to 15thNight
45%18%36%29%4
704
16th to endNight
5%9%23%40%19%2
632
March1st to 15thNight
5%9%21%35%22%5%
720
16th to endNight
36%19%36%27%5%
768
April1st to 15thNight
49%22%40%21%1
674
16th to endNight
29%23%38%22%3
540
May1st to 15thNight
26%20%39%27%3
540
16th to endNight
16%21%37%27%4
563
June1st to 15thNight
1213%44%33%3
540
16th to endNight
127%39%42%6%
540
July1st to 15thNight
4428%53%8%
510
16th to endNight
41319%54%16%
564
August1st to 15thNight
21216%60%17%
539
16th to endNight
2222%54%17%
576
September1st to 15thNight
5%27%24%46%13%
720
16th to endNight
2112%33%38%11%
716
October1st to 15thNight
1215%39%34%6%
720
16th to endNight
228%38%36%11%
768
November1st to 15thNight
1414%41%32%6%
760
16th to endNight
45%16%36%30%7%
780
December1st to 15thNight
7%5%17%35%30%3
780
16th to endNight
6%7%17%38%23%6%
832
Page generated at 2018-01-21 10:19:29. Version ac04

Copyright 2018 A. Danko


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