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Fremont
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fremont clear sky chart from 2005-11-05 to 2018-02-22.

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%
16031
26%
48940
24%
15995
70%
15995
38%
27326

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
64%
776
17%
2584
18%
776
66%
776
27%
1586
January16th to endNight
60%
832
23%
2704
25%
832
62%
832
26%
1707
February1st to 15thNight
61%
758
25%
2480
26%
758
65%
758
28%
1510
February16th to endNight
54%
660
24%
1979
22%
660
58%
660
27%
1277
March1st to 15thNight
55%
720
17%
2010
16%
720
57%
720
27%
1339
March16th to endNight
54%
768
19%
2085
15%
768
57%
768
30%
1366
April1st to 15thNight
56%
719
20%
1799
13%
719
58%
719
33%
1185
April16th to endNight
62%
720
24%
1800
13%
720
65%
720
46%
1047
May1st to 15thNight
70%
623
26%
1703
19%
623
72%
623
50%
898
May16th to endNight
69%
390
25%
1513
25%
390
73%
390
34%
744
June1st to 15thNight
74%
360
25%
1440
29%
360
79%
360
40%
652
June16th to endNight
86%
360
35%
1440
46%
360
88%
360
62%
505
July1st to 15thNight
89%
379
32%
1399
38%
379
89%
379
65%
507
July16th to endNight
79%
564
32%
1593
30%
531
80%
531
56%
717
August1st to 15thNight
77%
562
32%
1635
26%
559
77%
559
54%
777
August16th to endNight
81%
764
37%
1910
24%
764
81%
764
63%
971
September1st to 15thNight
83%
720
37%
1800
27%
720
83%
720
65%
901
September16th to endNight
78%
716
40%
1962
37%
716
80%
716
58%
962
October1st to 15thNight
74%
720
28%
2160
31%
720
77%
720
48%
1094
October16th to endNight
72%
768
33%
2304
36%
768
74%
768
42%
1239
November1st to 15thNight
69%
760
25%
2374
27%
760
72%
760
36%
1361
November16th to endNight
65%
780
23%
2624
25%
780
67%
780
31%
1492
December1st to 15thNight
61%
780
22%
2730
22%
780
65%
780
26%
1634
December16th to endNight
52%
832
20%
2912
18%
832
58%
832
23%
1855

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
7%5%23323346%58%
49315
Night
9%5%23323347%54%
49127
TransparencyDay
27%49%18%23%16%
49002
Night
29%49%18%21%16%
48941
SeeingDay
9%7%22%32%21%6%
6506
Night
10%211%32%34%8%
16043

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
15%6%2442345%7%44%
1682
16th to endDay
14%6%35%424436%43%
1872
February1st to 15thDay
15%8%24313347%44%
1714
16th to endDay
16%7%35%42345%7%40%
1641
March1st to 15thDay
13%7%36%4345%5%9%36%
1947
16th to endDay
11%6%36%5%36%5%5%6%40%
2138
April1st to 15thDay
14%7%35%423347%42%
2149
16th to endDay
8%413314246%57%
2160
May1st to 15thDay
4412212337%65%
2244
16th to endDay
7%6%33213336%58%
2597
June1st to 15thDay
5%5%13212336%61%
2520
16th to endDay
221111123377%
2520
July1st to 15thDay
131121122476%
2476
16th to endDay
121211123476%
2468
August1st to 15thDay
14321222473%
2316
16th to endDay
32212335%75%
2292
September1st to 15thDay
1312212235%74%
2160
16th to endDay
4312112245%70%
1996
October1st to 15thDay
4212313346%65%
1800
16th to endDay
6%5%13324336%59%
1920
November1st to 15thDay
8%5%2342445%7%50%
1815
16th to endDay
11%7%3442335%7%47%
1664
December1st to 15thDay
12%7%36%5%2344444%
1560
16th to endDay
17%6%3442345%8%39%
1664
January1st to 15thNight
14%5%2442346%8%42%
2584
16th to endNight
15%6%24424447%44%
2704
February1st to 15thNight
12%7%24435%45%6%45%
2468
16th to endNight
14%8%34423447%42%
1979
March1st to 15thNight
15%8%25%423347%43%
2010
16th to endNight
13%6%25%42435%7%44%
2085
April1st to 15thNight
11%6%244245%6%8%42%
1799
16th to endNight
7%312323347%59%
1800
May1st to 15thNight
45%13312348%59%
1703
16th to endNight
6%7%23322247%57%
1512
June1st to 15thNight
5%42321235%7%60%
1440
16th to endNight
1311111235%76%
1440
July1st to 15thNight
1212222236%72%
1482
16th to endNight
15%23413248%62%
1701
August1st to 15thNight
25%33422247%61%
1644
16th to endNight
424312247%65%
1910
September1st to 15thNight
2312212236%68%
1800
16th to endNight
3413212236%69%
1962
October1st to 15thNight
6%412312246%63%
2160
16th to endNight
6%414423346%57%
2304
November1st to 15thNight
8%5%24313348%53%
2374
16th to endNight
10%5%2342345%7%50%
2624
December1st to 15thNight
13%6%25%32435%6%46%
2730
16th to endNight
17%7%3432335%5%43%
2912

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
39%6%12%17%15%8%
1682
16th to endDay
41%6%8%12%19%10%
1872
February1st to 15thDay
39%5%9%18%22%5%
1714
16th to endDay
43%5%9%24%13%3
1641
March1st to 15thDay
44%5%11%17%15%5%
1947
16th to endDay
42%7%13%17%16%2
2138
April1st to 15thDay
42%413%18%18%2
2149
16th to endDay
26%413%25%22%7%
2160
May1st to 15thDay
20%49%29%28%8%
2244
16th to endDay
28%411%26%23%5%
2601
June1st to 15thDay
23%5%9%20%24%15%
2520
16th to endDay
11%25%16%34%30%
2520
July1st to 15thDay
12%15%8%23%48%
2330
16th to endDay
10%25%10%26%44%
2313
August1st to 15thDay
14%25%12%29%36%
2300
16th to endDay
11%25%15%36%28%
2292
September1st to 15thDay
13%26%14%31%32%
2160
16th to endDay
16%26%23%32%19%
1996
October1st to 15thDay
20%39%19%23%22%
1800
16th to endDay
25%410%20%23%15%
1920
November1st to 15thDay
32%5%12%24%18%6%
1815
16th to endDay
36%5%9%19%25%3
1664
December1st to 15thDay
42%410%15%17%8%
1560
16th to endDay
43%6%12%15%18%4
1664
January1st to 15thNight
38%5%13%19%15%7%
2584
16th to endNight
39%6%9%12%16%13%
2704
February1st to 15thNight
38%5%9%18%20%8%
2480
16th to endNight
41%5%11%24%15%2
1979
March1st to 15thNight
42%5%12%18%15%5%
2010
16th to endNight
39%6%14%17%17%5%
2085
April1st to 15thNight
36%6%15%21%16%3
1799
16th to endNight
25%414%25%22%8%
1800
May1st to 15thNight
21%410%21%29%12%
1704
16th to endNight
27%411%26%23%6%
1513
June1st to 15thNight
21%5%10%21%23%18%
1440
16th to endNight
11%1413%34%34%
1440
July1st to 15thNight
11%15%7%21%52%
1399
16th to endNight
17%18%9%20%41%
1593
August1st to 15thNight
20%1410%25%37%
1635
16th to endNight
16%15%10%31%33%
1910
September1st to 15thNight
15%2412%27%37%
1800
16th to endNight
17%25%21%30%22%
1962
October1st to 15thNight
22%38%20%22%23%
2160
16th to endNight
27%38%19%23%16%
2304
November1st to 15thNight
30%5%12%25%17%7%
2374
16th to endNight
33%410%22%20%7%
2624
December1st to 15thNight
38%5%10%14%19%11%
2730
16th to endNight
42%5%11%16%17%6%
2912

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
24%320%31%17%3
220
16th to endDay
15%5%20%30%22%6%
304
February1st to 15thDay
14%8%22%28%20%5%
282
16th to endDay
19%9%26%25%15%2
264
March1st to 15thDay
19%9%27%23%15%4
270
16th to endDay
14%14%35%23%10%2
288
April1st to 15thDay
18%17%30%21%10%1
269
16th to endDay
9%20%30%27%9%2
270
May1st to 15thDay
8%10%35%29%12%2
288
16th to endDay
11%11%22%32%13%8%
330
June1st to 15thDay
5%10%31%33%15%4
315
16th to endDay
1319%41%24%9%
315
July1st to 15thDay
3113%47%24%9%
305
16th to endDay
114%38%31%12%
327
August1st to 15thDay
217%42%26%10%
315
16th to endDay
213%40%31%11%
332
September1st to 15thDay
2114%40%31%9%
315
16th to endDay
45%19%33%26%9%
315
October1st to 15thDay
5%7%23%34%21%6%
315
16th to endDay
9%5%21%29%25%8%
336
November1st to 15thDay
11%121%28%26%11%
231
16th to endDay
9%7%14%32%33%1
114
December1st to 15thDay
12%421%26%26%8%
90
16th to endDay
12%9%15%26%29%7%
96
January1st to 15thNight
16%210%33%29%7%
780
16th to endNight
17%310%33%26%9%
832
February1st to 15thNight
14%312%34%28%6%
764
16th to endNight
16%414%38%21%5%
660
March1st to 15thNight
17%413%30%29%5%
720
16th to endNight
15%317%36%23%3
768
April1st to 15thNight
12%5%17%39%21%4
719
16th to endNight
8%319%35%26%6%
720
May1st to 15thNight
6%15%37%32%6%
624
16th to endNight
9%28%36%35%7%
391
June1st to 15thNight
6%9%40%39%3
360
16th to endNight
26%36%49%4
360
July1st to 15thNight
2124%61%9%
379
16th to endNight
3316%56%18%
564
August1st to 15thNight
5%424%52%13%
562
16th to endNight
25%29%49%12%
764
September1st to 15thNight
5%5%23%51%14%
720
16th to endNight
5%8%27%44%13%
716
October1st to 15thNight
7%110%34%36%10%
720
16th to endNight
7%18%29%36%16%
768
November1st to 15thNight
9%110%34%34%9%
760
16th to endNight
13%111%34%30%9%
780
December1st to 15thNight
15%312%35%25%8%
780
16th to endNight
19%417%33%21%4
832
Page generated at 2018-02-23 08:21:30. Version ac04

Copyright 2018 A. Danko


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