Saddleback Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Saddleback Observatory clear sky chart from 2005-11-05 to 2017-09-21.

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
54%
15159
26%
46909
20%
15122
61%
15122
33%
26405

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
39%
719
19%
2506
14%
716
49%
716
24%
1504
January16th to endNight
35%
768
23%
2499
15%
768
47%
768
20%
1598
February1st to 15thNight
38%
699
21%
2265
15%
696
48%
696
20%
1448
February16th to endNight
41%
632
23%
1895
16%
632
50%
632
21%
1257
March1st to 15thNight
36%
720
14%
2079
8%
720
42%
720
19%
1463
March16th to endNight
38%
768
18%
2046
10%
768
44%
768
22%
1403
April1st to 15thNight
39%
719
18%
1799
7%
719
44%
719
24%
1278
April16th to endNight
50%
720
22%
1800
9%
720
55%
720
35%
1115
May1st to 15thNight
49%
525
24%
1605
15%
525
57%
525
37%
843
May16th to endNight
59%
374
20%
1496
22%
374
63%
374
28%
792
June1st to 15thNight
64%
360
24%
1440
28%
360
71%
360
37%
667
June16th to endNight
79%
360
33%
1440
43%
360
84%
360
55%
532
July1st to 15thNight
90%
340
33%
1360
45%
340
92%
340
67%
443
July16th to endNight
90%
451
40%
1485
44%
423
91%
423
73%
523
August1st to 15thNight
86%
568
36%
1641
30%
565
87%
565
65%
730
August16th to endNight
86%
764
44%
1910
27%
764
87%
764
77%
875
September1st to 15thNight
84%
720
42%
1800
27%
720
87%
720
74%
843
September16th to endNight
68%
680
42%
1837
32%
680
76%
680
62%
876
October1st to 15thNight
58%
660
30%
1980
27%
660
66%
660
42%
1019
October16th to endNight
57%
704
32%
2112
27%
704
66%
704
41%
1084
November1st to 15thNight
53%
700
24%
2275
20%
700
61%
700
28%
1320
November16th to endNight
41%
720
23%
2431
18%
720
51%
720
25%
1393
December1st to 15thNight
37%
720
20%
2520
13%
720
48%
720
18%
1602
December16th to endNight
30%
768
21%
2688
12%
768
44%
768
15%
1797

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
10%7%12212335%58%
47953
Night
10%7%12213335%55%
47097
TransparencyDay
29%37%19%23%16%
47631
Night
31%38%19%22%14%
46919
SeeingDay
18%19%32%17%8%2
5817
Night
16%8%15%28%25%4
15167

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
14%9%2433245%7%42%
1432
16th to endDay
16%13%23313337%41%
1722
February1st to 15thDay
18%10%23222336%43%
1590
16th to endDay
15%19%32213335%37%
1579
March1st to 15thDay
16%15%34333337%34%
1878
16th to endDay
15%15%1342345%7%37%
2178
April1st to 15thDay
15%15%2332345%6%37%
2149
16th to endDay
12%8%13223346%50%
2160
May1st to 15thDay
8%413312348%57%
2341
16th to endDay
12%6%144135%45%49%
2615
June1st to 15thDay
9%423312335%59%
2520
16th to endDay
3111122480%
2520
July1st to 15thDay
111122383%
2520
16th to endDay
2111111285%
2580
August1st to 15thDay
2111122282%
2308
16th to endDay
111112286%
2292
September1st to 15thDay
2111222479%
2160
16th to endDay
5%2111223474%
1913
October1st to 15thDay
10%32212335%63%
1650
16th to endDay
11%5%13312346%56%
1759
November1st to 15thDay
11%7%13323446%50%
1584
16th to endDay
14%11%23324345%46%
1527
December1st to 15thDay
19%9%3431345%6%38%
1440
16th to endDay
20%13%24423345%36%
1536
January1st to 15thNight
12%10%24323347%45%
2506
16th to endNight
14%13%23223335%44%
2499
February1st to 15thNight
16%9%134235%5%7%41%
2262
16th to endNight
16%14%23213445%40%
1895
March1st to 15thNight
15%15%3342445%6%34%
2079
16th to endNight
15%14%12223436%43%
2046
April1st to 15thNight
13%13%24414446%38%
1799
16th to endNight
11%7%13223346%53%
1800
May1st to 15thNight
9%312323335%61%
1605
16th to endNight
10%5%13323436%54%
1496
June1st to 15thNight
8%412212236%65%
1440
16th to endNight
31122222377%
1440
July1st to 15thNight
111111112383%
1440
16th to endNight
111112284%
1587
August1st to 15thNight
31121223477%
1650
16th to endNight
11122383%
1910
September1st to 15thNight
11121123481%
1800
16th to endNight
4112223475%
1837
October1st to 15thNight
9%313212235%65%
1980
16th to endNight
10%41121235%7%59%
2112
November1st to 15thNight
11%5%2331345%6%51%
2275
16th to endNight
11%8%23324347%49%
2431
December1st to 15thNight
19%8%22313446%41%
2520
16th to endNight
19%14%23323336%38%
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
41%5%10%21%16%4
1432
16th to endDay
44%37%16%17%10%
1722
February1st to 15thDay
42%311%19%18%4
1590
16th to endDay
49%38%24%12%2
1579
March1st to 15thDay
51%210%15%14%5%
1878
16th to endDay
47%414%19%10%3
2178
April1st to 15thDay
47%313%19%13%1
2149
16th to endDay
35%412%25%18%4
2160
May1st to 15thDay
27%310%30%23%4
2341
16th to endDay
36%410%26%18%3
2619
June1st to 15thDay
28%39%19%23%15%
2520
16th to endDay
10%1419%40%24%
2520
July1st to 15thDay
7%1211%29%47%
2371
16th to endDay
9%1212%24%49%
2419
August1st to 15thDay
9%2214%30%41%
2292
16th to endDay
6%1116%36%37%
2292
September1st to 15thDay
11%2214%36%33%
2160
16th to endDay
14%35%27%30%18%
1913
October1st to 15thDay
24%35%27%28%10%
1650
16th to endDay
29%28%23%23%12%
1759
November1st to 15thDay
35%310%23%18%7%
1584
16th to endDay
40%37%22%20%5%
1527
December1st to 15thDay
46%48%19%18%2
1440
16th to endDay
50%48%12%18%5%
1536
January1st to 15thNight
40%310%19%19%5%
2506
16th to endNight
44%36%14%18%12%
2499
February1st to 15thNight
42%48%21%16%6%
2274
16th to endNight
45%48%23%14%4
1895
March1st to 15thNight
50%49%15%13%6%
2079
16th to endNight
43%6%12%20%13%4
2046
April1st to 15thNight
45%5%12%21%12%2
1799
16th to endNight
32%413%29%17%3
1800
May1st to 15thNight
26%312%27%25%6%
1606
16th to endNight
33%413%28%16%4
1496
June1st to 15thNight
22%5%10%21%24%15%
1440
16th to endNight
13%25%17%36%25%
1440
July1st to 15thNight
8%1210%26%50%
1360
16th to endNight
7%1212%22%52%
1485
August1st to 15thNight
13%2211%29%41%
1641
16th to endNight
7%1215%33%38%
1910
September1st to 15thNight
9%2313%37%35%
1800
16th to endNight
14%2422%36%20%
1837
October1st to 15thNight
24%26%24%29%12%
1980
16th to endNight
23%39%24%27%11%
2112
November1st to 15thNight
32%6%9%22%19%9%
2275
16th to endNight
35%38%24%20%6%
2431
December1st to 15thNight
43%48%17%21%3
2520
16th to endNight
49%36%13%20%5%
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
45%13%30%8%3
60
16th to endDay
33%15%24%16%10%
250
February1st to 15thDay
32%13%28%17%6%1
239
16th to endDay
34%17%28%14%4
238
March1st to 15thDay
39%21%18%11%7%2
270
16th to endDay
31%25%23%14%4
288
April1st to 15thDay
34%24%25%10%21
269
16th to endDay
26%28%27%12%31
270
May1st to 15thDay
18%27%33%14%32
288
16th to endDay
20%21%26%15%10%5%
330
June1st to 15thDay
18%20%35%16%6%3
315
16th to endDay
6%18%43%18%8%6%
315
July1st to 15thDay
212%50%20%9%4
305
16th to endDay
113%48%20%10%5%
327
August1st to 15thDay
419%41%19%9%6%
315
16th to endDay
117%41%20%13%6%
332
September1st to 15thDay
314%38%25%14%2
315
16th to endDay
9%19%36%24%6%2
276
October1st to 15thDay
14%21%29%20%10%2
255
16th to endDay
22%22%25%21%8%
271
November1st to 15thDay
12%13%21%16%32%4
90
16th to endDay
20%20%24%22%13%
75
December1st to 15thDay
46%16%18%11%5%1
60
16th to endDay
25%15%20%29%9%
64
January1st to 15thNight
20%8%25%27%13%4
720
16th to endNight
23%13%21%22%15%2
768
February1st to 15thNight
24%10%18%29%14%1
704
16th to endNight
28%9%15%29%13%3
632
March1st to 15thNight
26%11%18%22%17%3
720
16th to endNight
27%14%16%20%19%1
768
April1st to 15thNight
23%11%18%28%15%2
719
16th to endNight
18%9%18%30%17%5%
720
May1st to 15thNight
11%12%21%27%22%3
526
16th to endNight
14%5%12%28%33%6%
375
June1st to 15thNight
10%5%14%28%36%3
360
16th to endNight
4210%38%40%4
360
July1st to 15thNight
2435%51%5%
340
16th to endNight
430%54%9%
451
August1st to 15thNight
3432%48%9%
568
16th to endNight
17%39%41%8%
764
September1st to 15thNight
218%33%45%8%
720
16th to endNight
5%5%17%28%31%12%
680
October1st to 15thNight
11%10%14%26%31%5%
660
16th to endNight
14%9%15%28%25%6%
704
November1st to 15thNight
15%9%17%29%24%4
700
16th to endNight
19%14%20%23%19%2
720
December1st to 15thNight
27%12%18%28%11%1
720
16th to endNight
31%13%19%23%10%1
768
Page generated at 2017-09-22 04:35:32. Version ac04

Copyright 2017 A. Danko


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