Santa Margarita Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Santa Margarita Lake clear sky chart from 2005-11-05 to 2017-12-02.

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
74%
15951
33%
47829
29%
15914
78%
15914
49%
23928

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%
716
25%
2384
26%
716
67%
716
35%
1295
January16th to endNight
60%
768
28%
2496
28%
768
64%
768
33%
1406
February1st to 15thNight
64%
699
29%
2179
30%
698
68%
698
36%
1216
February16th to endNight
57%
632
27%
1895
27%
632
62%
632
32%
1130
March1st to 15thNight
64%
720
23%
2070
22%
720
69%
720
40%
1180
March16th to endNight
65%
768
24%
2043
19%
768
70%
768
41%
1200
April1st to 15thNight
62%
719
28%
1799
17%
719
66%
719
45%
1055
April16th to endNight
65%
720
30%
1800
14%
720
71%
720
54%
955
May1st to 15thNight
79%
719
26%
1799
17%
719
80%
719
57%
952
May16th to endNight
78%
434
34%
1558
32%
434
82%
434
51%
660
June1st to 15thNight
86%
360
34%
1440
40%
360
90%
360
56%
532
June16th to endNight
96%
360
41%
1440
51%
360
97%
360
76%
441
July1st to 15thNight
96%
376
36%
1396
41%
376
96%
376
72%
471
July16th to endNight
91%
564
40%
1593
34%
531
92%
531
67%
664
August1st to 15thNight
94%
672
39%
1746
27%
669
94%
669
75%
780
August16th to endNight
95%
764
45%
1910
30%
764
95%
764
79%
876
September1st to 15thNight
91%
720
42%
1800
33%
720
91%
720
70%
882
September16th to endNight
90%
716
48%
1926
44%
716
92%
716
77%
831
October1st to 15thNight
76%
720
33%
2148
34%
720
80%
720
53%
1026
October16th to endNight
78%
768
41%
2304
42%
768
83%
768
53%
1107
November1st to 15thNight
73%
760
35%
2400
35%
760
78%
760
50%
1133
November16th to endNight
71%
780
33%
2535
32%
780
76%
780
44%
1250
December1st to 15thNight
64%
728
29%
2480
29%
728
70%
728
33%
1373
December16th to endNight
55%
768
25%
2688
24%
768
63%
768
29%
1513

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%212212335%67%
48620
Night
6%312213335%65%
48019
TransparencyDay
20%36%19%28%20%
48307
Night
21%37%18%26%21%
47832
SeeingDay
7%8%22%36%19%4
6311
Night
7%38%31%37%11%
15962

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
11%5%13414446%53%
1552
16th to endDay
15%414422335%51%
1728
February1st to 15thDay
15%6%23312337%51%
1682
16th to endDay
17%5%23423345%45%
1579
March1st to 15thDay
10%31442445%9%48%
1889
16th to endDay
10%5%22324447%51%
2181
April1st to 15thDay
11%5%24314236%54%
2149
16th to endDay
6%212213346%63%
2160
May1st to 15thDay
3212212245%70%
2151
16th to endDay
322212236%72%
2550
June1st to 15thDay
221111246%73%
2520
16th to endDay
1111387%
2520
July1st to 15thDay
111111225%80%
2478
16th to endDay
11112235%78%
2468
August1st to 15thDay
111212483%
2205
16th to endDay
111112384%
2292
September1st to 15thDay
11111112483%
2160
16th to endDay
11111123479%
2034
October1st to 15thDay
5%212212235%69%
1809
16th to endDay
322322436%67%
1920
November1st to 15thDay
7%31321333463%
1787
16th to endDay
7%313323346%59%
1755
December1st to 15thDay
11%425%424345%49%
1515
16th to endDay
16%423412436%50%
1536
January1st to 15thNight
9%424323336%54%
2384
16th to endNight
12%5%24323335%53%
2496
February1st to 15thNight
10%5%1322435%6%54%
2170
16th to endNight
14%5%2441333452%
1895
March1st to 15thNight
8%4233235%47%54%
2070
16th to endNight
8%423225%45%8%53%
2043
April1st to 15thNight
9%413323235%60%
1799
16th to endNight
4321313336%66%
1800
May1st to 15thNight
3212212348%67%
1799
16th to endNight
322212346%71%
1557
June1st to 15thNight
1111112335%75%
1440
16th to endNight
112387%
1440
July1st to 15thNight
12225%82%
1479
16th to endNight
1112212479%
1701
August1st to 15thNight
111112384%
1755
16th to endNight
11122484%
1910
September1st to 15thNight
1212232379%
1800
16th to endNight
111212384%
1926
October1st to 15thNight
431322223371%
2148
16th to endNight
4213213335%69%
2304
November1st to 15thNight
4313213346%66%
2400
16th to endNight
5%323323447%60%
2535
December1st to 15thNight
10%42432345%6%53%
2480
16th to endNight
14%5%23323336%50%
2688

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
30%46%21%22%13%
1552
16th to endDay
34%49%14%17%18%
1728
February1st to 15thDay
34%26%20%23%12%
1682
16th to endDay
39%39%22%20%4
1579
March1st to 15thDay
31%413%20%19%10%
1889
16th to endDay
31%412%24%19%6%
2181
April1st to 15thDay
31%411%25%21%6%
2149
16th to endDay
21%411%25%27%9%
2160
May1st to 15thDay
17%38%26%32%11%
2151
16th to endDay
15%29%33%30%7%
2554
June1st to 15thDay
13%48%21%30%21%
2520
16th to endDay
6%1211%38%39%
2520
July1st to 15thDay
9%229%29%45%
2332
16th to endDay
10%25%13%32%34%
2313
August1st to 15thDay
9%2113%35%37%
2189
16th to endDay
7%113%43%33%
2292
September1st to 15thDay
10%1216%32%35%
2160
16th to endDay
9%2122%37%25%
2034
October1st to 15thDay
18%35%19%26%25%
1809
16th to endDay
18%35%19%27%24%
1920
November1st to 15thDay
24%27%20%29%14%
1787
16th to endDay
25%47%19%28%15%
1755
December1st to 15thDay
35%39%16%21%12%
1515
16th to endDay
35%39%21%19%9%
1536
January1st to 15thNight
31%37%20%23%14%
2384
16th to endNight
33%39%13%20%19%
2496
February1st to 15thNight
30%37%20%25%11%
2181
16th to endNight
35%37%23%23%6%
1895
March1st to 15thNight
28%412%24%19%10%
2070
16th to endNight
27%5%15%20%22%8%
2043
April1st to 15thNight
27%311%29%21%7%
1799
16th to endNight
19%311%26%28%11%
1800
May1st to 15thNight
17%311%22%30%13%
1800
16th to endNight
16%37%28%32%11%
1558
June1st to 15thNight
12%39%19%29%26%
1440
16th to endNight
6%1210%35%44%
1440
July1st to 15thNight
6%2111%26%51%
1396
16th to endNight
10%2211%29%42%
1593
August1st to 15thNight
8%29%33%46%
1746
16th to endNight
7%28%38%42%
1910
September1st to 15thNight
11%3311%25%44%
1800
16th to endNight
7%1317%39%30%
1926
October1st to 15thNight
19%2420%26%26%
2148
16th to endNight
18%3419%27%26%
2304
November1st to 15thNight
19%28%22%28%18%
2400
16th to endNight
23%39%20%25%17%
2535
December1st to 15thNight
31%47%17%22%15%
2480
16th to endNight
34%311%19%19%10%
2688

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
19%11%32%23%12%
180
16th to endDay
15%13%27%26%16%
256
February1st to 15thDay
17%11%27%23%16%2
255
16th to endDay
20%16%28%24%7%2
238
March1st to 15thDay
10%16%37%25%9%
270
16th to endDay
14%15%26%32%9%1
288
April1st to 15thDay
17%14%34%22%8%2
269
16th to endDay
10%17%37%26%7%1
270
May1st to 15thDay
8%9%32%34%12%3
288
16th to endDay
5%10%26%39%14%3
330
June1st to 15thDay
27%20%44%21%3
315
16th to endDay
17%44%26%10%
315
July1st to 15thDay
29%44%32%10%
305
16th to endDay
16%44%34%12%
327
August1st to 15thDay
219%47%30%7%
315
16th to endDay
6%41%37%12%
332
September1st to 15thDay
4212%49%25%5%
315
16th to endDay
6%22%40%26%1
315
October1st to 15thDay
312%28%40%12%2
315
16th to endDay
5%8%23%38%22%2
336
November1st to 15thDay
7%7%19%33%26%5%
203
16th to endDay
8%10%28%29%19%3
135
December1st to 15thDay
12%14%24%36%13%
75
16th to endDay
18%10%34%21%14%
64
January1st to 15thNight
12%311%36%26%9%
720
16th to endNight
14%412%36%24%7%
768
February1st to 15thNight
12%5%9%34%28%8%
704
16th to endNight
15%7%12%37%22%5%
632
March1st to 15thNight
9%414%40%23%7%
720
16th to endNight
9%5%13%34%31%5%
768
April1st to 15thNight
9%6%15%36%27%5%
719
16th to endNight
5%6%15%29%33%9%
720
May1st to 15thNight
437%35%38%10%
720
16th to endNight
349%34%38%10%
435
June1st to 15thNight
316%33%46%8%
360
16th to endNight
128%56%11%
360
July1st to 15thNight
10%63%24%
376
16th to endNight
16%57%33%
564
August1st to 15thNight
117%60%19%
672
16th to endNight
14%63%20%
764
September1st to 15thNight
2123%54%18%
720
16th to endNight
1431%47%14%
716
October1st to 15thNight
6%28%33%38%10%
720
16th to endNight
6%18%33%38%11%
768
November1st to 15thNight
5%311%38%33%8%
760
16th to endNight
6%411%37%31%9%
780
December1st to 15thNight
12%410%37%30%5%
728
16th to endNight
15%6%14%37%20%4
768
Page generated at 2017-12-03 08:16:38. Version ac04

Copyright 2017 A. Danko


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