Santa Rosa Mountain
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Santa Rosa Mountain clear sky chart from 2005-11-05 to 2017-10-31.

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
66%
16335
38%
47476
28%
16294
75%
16294
62%
20966

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
63%
717
33%
2327
29%
716
73%
716
48%
1081
January16th to endNight
55%
768
37%
2339
28%
768
68%
768
44%
1157
February1st to 15thNight
58%
700
37%
2111
28%
700
71%
700
54%
960
February16th to endNight
50%
632
35%
1895
28%
632
63%
632
43%
970
March1st to 15thNight
52%
720
35%
2142
27%
720
66%
720
53%
987
March16th to endNight
55%
768
37%
2070
22%
768
68%
768
57%
989
April1st to 15thNight
45%
719
37%
1799
14%
719
60%
719
57%
894
April16th to endNight
50%
720
40%
1800
15%
720
63%
720
68%
826
May1st to 15thNight
55%
547
40%
1626
22%
546
67%
546
70%
635
May16th to endNight
52%
562
39%
1685
21%
561
65%
561
72%
648
June1st to 15thNight
62%
540
36%
1620
23%
540
71%
540
79%
606
June16th to endNight
73%
540
38%
1620
28%
540
79%
540
83%
603
July1st to 15thNight
86%
510
33%
1530
28%
510
88%
510
72%
622
July16th to endNight
84%
579
34%
1607
28%
545
85%
545
64%
707
August1st to 15thNight
89%
717
38%
1790
23%
713
91%
713
81%
800
August16th to endNight
90%
764
44%
1910
31%
764
91%
764
76%
895
September1st to 15thNight
87%
720
39%
1890
30%
720
90%
720
74%
860
September16th to endNight
80%
716
50%
1980
40%
716
89%
716
86%
778
October1st to 15thNight
69%
720
42%
1980
31%
720
80%
720
74%
842
October16th to endNight
76%
768
47%
2304
42%
768
86%
768
69%
948
November1st to 15thNight
72%
700
38%
2275
35%
700
83%
700
65%
895
November16th to endNight
69%
720
41%
2340
39%
720
77%
720
59%
977
December1st to 15thNight
61%
720
35%
2340
32%
720
69%
720
47%
1080
December16th to endNight
54%
768
35%
2496
29%
768
65%
768
43%
1206

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
2212213345%70%
48272
Night
1212212335%72%
47674
TransparencyDay
14%15%13%26%38%
47969
Night
13%16%15%26%37%
47478
SeeingDay
5%11%29%33%16%3
6024
Night
35%20%32%29%8%
16343

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
2322333347%62%
1611
16th to endDay
5%41332346%6%58%
1884
February1st to 15thDay
3312314238%63%
1751
16th to endDay
3315%42446%8%55%
1579
March1st to 15thDay
2222214347%66%
1818
16th to endDay
121321345%7%66%
2151
April1st to 15thDay
1213323346%66%
2149
16th to endDay
111112337%76%
2160
May1st to 15thDay
1112112325%77%
2322
16th to endDay
1111123381%
2429
June1st to 15thDay
111235%81%
2340
16th to endDay
111111285%
2340
July1st to 15thDay
3212212445%69%
2340
16th to endDay
12133135%5%7%63%
2449
August1st to 15thDay
111213345%72%
2160
16th to endDay
121323345%71%
2292
September1st to 15thDay
21222334472%
2070
16th to endDay
1112122283%
1980
October1st to 15thDay
1121324377%
1980
16th to endDay
111213245%75%
1915
November1st to 15thDay
1212212335%72%
1584
16th to endDay
2312313346%67%
1620
December1st to 15thDay
5%31332445%8%57%
1620
16th to endDay
442332435%7%59%
1728
January1st to 15thNight
2313323446%63%
2327
16th to endNight
4314423336%61%
2339
February1st to 15thNight
1213313447%65%
2101
16th to endNight
32144345%5%7%56%
1895
March1st to 15thNight
1212224348%64%
2142
16th to endNight
11122235%5%7%65%
2070
April1st to 15thNight
1213212236%71%
1799
16th to endNight
1111223479%
1800
May1st to 15thNight
11111236%78%
1626
16th to endNight
1111112484%
1684
June1st to 15thNight
11112385%
1620
16th to endNight
11112188%
1620
July1st to 15thNight
11111133378%
1620
16th to endNight
1212222346%70%
1716
August1st to 15thNight
111123480%
1800
16th to endNight
2111222381%
1910
September1st to 15thNight
1121222479%
1890
16th to endNight
1111289%
1980
October1st to 15thNight
1112325%78%
1980
16th to endNight
11121222478%
2304
November1st to 15thNight
111213335%75%
2275
16th to endNight
2212212346%69%
2340
December1st to 15thNight
331332345%7%59%
2340
16th to endNight
441332345%7%59%
2496

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
18%38%16%27%25%
1612
16th to endDay
23%28%16%24%25%
1884
February1st to 15thDay
19%17%16%27%27%
1751
16th to endDay
23%27%19%26%19%
1579
March1st to 15thDay
16%6%17%30%28%
1818
16th to endDay
15%27%18%34%21%
2151
April1st to 15thDay
16%1417%36%22%
2149
16th to endDay
7%15%20%32%32%
2160
May1st to 15thDay
10%1214%31%38%
2322
16th to endDay
7%1414%35%37%
2432
June1st to 15thDay
6%29%22%57%
2340
16th to endDay
7%1311%75%
2340
July1st to 15thDay
13%249%20%48%
2201
16th to endDay
16%48%17%23%30%
2295
August1st to 15thDay
12%1310%21%49%
2146
16th to endDay
13%25%8%23%45%
2292
September1st to 15thDay
13%25%9%22%47%
2070
16th to endDay
9%16%26%55%
1980
October1st to 15thDay
10%2213%26%44%
1980
16th to endDay
11%5%10%22%49%
1915
November1st to 15thDay
14%1415%31%33%
1584
16th to endDay
16%7%13%27%34%
1620
December1st to 15thDay
22%19%20%20%25%
1620
16th to endDay
23%210%20%25%17%
1728
January1st to 15thNight
19%26%17%26%27%
2327
16th to endNight
23%28%15%21%28%
2339
February1st to 15thNight
16%28%18%23%30%
2112
16th to endNight
24%29%19%24%20%
1895
March1st to 15thNight
16%27%17%28%27%
2142
16th to endNight
14%28%19%30%24%
2070
April1st to 15thNight
14%17%20%35%20%
1799
16th to endNight
8%16%19%32%32%
1800
May1st to 15thNight
7%15%16%32%36%
1627
16th to endNight
6%5%16%35%34%
1685
June1st to 15thNight
5%211%20%58%
1620
16th to endNight
5%49%78%
1620
July1st to 15thNight
9%128%20%56%
1530
16th to endNight
13%19%15%26%33%
1607
August1st to 15thNight
7%1312%24%51%
1790
16th to endNight
9%128%26%50%
1910
September1st to 15thNight
9%249%24%50%
1890
16th to endNight
48%27%58%
1980
October1st to 15thNight
8%15%12%32%40%
1980
16th to endNight
9%1312%21%50%
2304
November1st to 15thNight
11%15%13%31%36%
2275
16th to endNight
14%16%16%26%34%
2340
December1st to 15thNight
20%29%18%23%25%
2340
16th to endNight
22%211%19%24%19%
2496

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
17%11%27%34%8%
90
16th to endDay
12%15%31%30%7%1
252
February1st to 15thDay
8%15%32%32%9%1
266
16th to endDay
13%24%32%21%7%
238
March1st to 15thDay
11%18%30%25%12%1
270
16th to endDay
10%19%35%23%11%
288
April1st to 15thDay
10%24%33%20%9%1
269
16th to endDay
7%23%40%20%7%2
270
May1st to 15thDay
5%16%35%33%5%3
288
16th to endDay
316%38%26%12%2
330
June1st to 15thDay
212%34%32%14%4
315
16th to endDay
25%30%33%23%4
315
July1st to 15thDay
2117%45%26%5%
305
16th to endDay
3115%40%29%11%
327
August1st to 15thDay
2219%45%22%8%
315
16th to endDay
1120%43%23%9%
332
September1st to 15thDay
1233%41%16%3
315
16th to endDay
46%28%42%14%2
315
October1st to 15thDay
311%32%39%12%
315
16th to endDay
49%23%33%27%2
243
November1st to 15thDay
412%16%26%32%7%
90
16th to endDay
13%8%26%30%20%1
90
December1st to 15thDay
6%7%21%42%20%2
90
16th to endDay
11%13%26%34%14%
96
January1st to 15thNight
45%18%33%25%13%
720
16th to endNight
8%6%21%29%26%7%
768
February1st to 15thNight
45%23%32%23%10%
704
16th to endNight
6%8%29%27%20%6%
632
March1st to 15thNight
5%6%28%31%20%6%
720
16th to endNight
5%8%28%28%22%6%
768
April1st to 15thNight
5%13%32%27%16%4
719
16th to endNight
312%31%27%18%6%
720
May1st to 15thNight
28%29%37%17%3
547
16th to endNight
110%34%32%18%2
563
June1st to 15thNight
5%30%42%19%1
540
16th to endNight
1122%47%25%2
540
July1st to 15thNight
16%48%37%4
510
16th to endNight
25%39%46%5%
579
August1st to 15thNight
5%38%45%8%
717
16th to endNight
3328%53%11%
764
September1st to 15thNight
16%34%47%9%
720
16th to endNight
1114%34%34%12%
716
October1st to 15thNight
1422%32%29%8%
720
16th to endNight
2314%29%33%16%
768
November1st to 15thNight
2317%32%31%12%
700
16th to endNight
3319%28%29%15%
720
December1st to 15thNight
6%5%19%30%27%10%
720
16th to endNight
8%6%24%27%24%7%
768
Page generated at 2017-11-01 14:23:35. Version ac04

Copyright 2017 A. Danko


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