Somerton Creek
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Somerton Creek 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
41%
15825
21%
47849
13%
15788
50%
15788
26%
30293

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
27%
717
22%
2351
10%
716
42%
716
20%
1465
January16th to endNight
23%
768
22%
2496
9%
768
41%
768
22%
1575
February1st to 15thNight
20%
701
20%
2264
8%
701
36%
701
22%
1407
February16th to endNight
22%
631
27%
1893
11%
631
40%
631
26%
1127
March1st to 15thNight
28%
720
22%
2001
11%
720
40%
720
28%
1288
March16th to endNight
30%
768
20%
2082
11%
768
38%
768
26%
1388
April1st to 15thNight
27%
718
21%
1796
6%
718
36%
718
30%
1195
April16th to endNight
35%
720
20%
1800
7%
720
40%
720
32%
1182
May1st to 15thNight
37%
666
15%
1746
5%
666
43%
666
26%
1209
May16th to endNight
57%
414
19%
1537
17%
414
61%
414
26%
904
June1st to 15thNight
61%
360
17%
1440
18%
360
64%
360
23%
843
June16th to endNight
61%
360
17%
1440
18%
360
65%
360
23%
860
July1st to 15thNight
63%
406
13%
1426
14%
406
65%
406
23%
906
July16th to endNight
64%
564
16%
1595
12%
531
69%
531
30%
1019
August1st to 15thNight
61%
587
13%
1657
9%
584
61%
584
27%
1113
August16th to endNight
61%
764
18%
1910
11%
764
62%
764
28%
1325
September1st to 15thNight
57%
720
23%
1800
15%
720
60%
720
30%
1212
September16th to endNight
49%
717
18%
1964
14%
717
53%
717
24%
1369
October1st to 15thNight
48%
720
24%
2160
21%
720
55%
720
27%
1373
October16th to endNight
43%
768
32%
2304
22%
768
58%
768
34%
1327
November1st to 15thNight
42%
760
23%
2372
15%
760
53%
760
29%
1437
November16th to endNight
41%
780
26%
2581
20%
780
52%
780
27%
1533
December1st to 15thNight
34%
728
19%
2546
12%
728
45%
728
21%
1593
December16th to endNight
29%
768
23%
2688
13%
768
44%
768
21%
1643

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
13%5%25%5%3445%7%41%
48577
Night
13%5%2442445%7%44%
48039
Cloud CoverDay
13%5%25%5%35%45%7%41%
48587
Night
13%5%2442445%7%44%
48043
TransparencyDay
40%6%11%20%16%3
48285
Night
38%6%11%21%17%4
47849
SeeingDay
17%8%24%25%18%6%
6102
Night
16%8%28%31%13%1
15832

By Month

Percentage Cloud Cover NE (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
16%7%24333446%44%
1585
16th to endDay
16%5%2432435%5%46%
1728
February1st to 15thDay
16%5%245%24436%45%
1595
16th to endDay
15%424434448%43%
1580
March1st to 15thDay
14%6%24313346%48%
1945
16th to endDay
18%6%24424335%44%
2140
April1st to 15thDay
12%42332435%7%51%
2152
16th to endDay
11%5%25%5%25%5%46%44%
2160
May1st to 15thDay
14%6%25%5%35%45%6%39%
2215
16th to endDay
11%5%25%5%25%6%5%8%41%
2575
June1st to 15thDay
9%5%24437%5%6%9%41%
2520
16th to endDay
7%5%25%6%46%6%6%12%36%
2520
July1st to 15thDay
8%415%5%47%6%7%11%36%
2444
16th to endDay
5%5%36%7%47%5%7%11%33%
2465
August1st to 15thDay
10%6%37%6%46%6%7%9%32%
2280
16th to endDay
11%5%26%6%47%6%7%10%31%
2292
September1st to 15thDay
13%425%5%345%6%8%39%
2160
16th to endDay
20%7%36%6%33447%31%
1993
October1st to 15thDay
19%6%25%422246%43%
1800
16th to endDay
11%324423335%55%
1920
November1st to 15thDay
17%5%24324235%47%
1815
16th to endDay
13%413423345%53%
1706
December1st to 15thDay
14%425%424446%45%
1451
16th to endDay
20%5%2442335%5%42%
1536
January1st to 15thNight
14%6%2432445%7%43%
2351
16th to endNight
16%5%25%423445%44%
2496
February1st to 15thNight
18%5%24323436%44%
2263
16th to endNight
13%6%23324345%49%
1893
March1st to 15thNight
14%413425%436%48%
1989
16th to endNight
16%5%24424446%43%
2082
April1st to 15thNight
11%5%345%34446%47%
1796
16th to endNight
15%324423447%47%
1800
May1st to 15thNight
13%6%2443446%8%39%
1746
16th to endNight
10%4134345%5%9%46%
1535
June1st to 15thNight
9%4145%35%46%11%41%
1440
16th to endNight
6%415%6%35%6%8%10%41%
1440
July1st to 15thNight
6%426%6%35%6%8%10%39%
1512
16th to endNight
7%4245%26%6%8%11%39%
1703
August1st to 15thNight
8%6%37%6%246%6%10%37%
1668
16th to endNight
10%6%26%5%35%5%7%10%37%
1910
September1st to 15thNight
12%5%25%5%3345%7%43%
1800
16th to endNight
16%6%35%5%3345%7%37%
1964
October1st to 15thNight
17%5%24424345%46%
2160
16th to endNight
12%413422336%54%
2304
November1st to 15thNight
17%423323345%49%
2372
16th to endNight
13%424324346%48%
2581
December1st to 15thNight
14%6%345%24447%42%
2546
16th to endNight
17%7%24423346%44%
2688

Percentage Cloud Cover SE (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
16%7%24223437%44%
1585
16th to endDay
16%5%23323445%45%
1728
February1st to 15thDay
15%6%24435%336%45%
1595
16th to endDay
15%424424448%44%
1580
March1st to 15thDay
14%6%24323436%49%
1956
16th to endDay
18%6%24424335%43%
2139
April1st to 15thDay
13%423323347%50%
2152
16th to endDay
12%5%15%5%3445%5%45%
2160
May1st to 15thDay
16%5%35%5%34447%39%
2215
16th to endDay
11%5%26%425%5%6%9%40%
2575
June1st to 15thDay
9%4145%46%6%7%9%40%
2520
16th to endDay
8%415%6%36%5%7%12%36%
2520
July1st to 15thDay
8%425%6%46%7%7%11%36%
2444
16th to endDay
6%5%36%7%47%7%7%10%33%
2465
August1st to 15thDay
11%6%36%6%45%6%7%9%31%
2280
16th to endDay
11%5%26%6%47%6%6%10%31%
2292
September1st to 15thDay
13%5%25%6%25%5%6%8%39%
2160
16th to endDay
20%7%35%6%35%446%31%
1993
October1st to 15thDay
19%7%34323336%42%
1800
16th to endDay
12%424423325%55%
1920
November1st to 15thDay
18%424324345%47%
1815
16th to endDay
14%314323345%52%
1706
December1st to 15thDay
14%5%25%41435%6%45%
1451
16th to endDay
19%7%24323345%42%
1536
January1st to 15thNight
14%6%2442445%6%43%
2351
16th to endNight
16%5%35%423445%44%
2496
February1st to 15thNight
18%6%24323436%44%
2256
16th to endNight
12%5%23423446%49%
1893
March1st to 15thNight
14%413425%345%47%
2001
16th to endNight
17%5%245%2435%5%43%
2082
April1st to 15thNight
10%6%245%24446%47%
1796
16th to endNight
15%415%42335%6%46%
1800
May1st to 15thNight
13%6%245%245%6%8%38%
1745
16th to endNight
10%42433445%8%46%
1535
June1st to 15thNight
10%4245%345%6%11%41%
1440
16th to endNight
6%3245%35%5%7%11%42%
1440
July1st to 15thNight
6%435%6%35%7%8%9%38%
1512
16th to endNight
7%3245%36%6%9%11%38%
1703
August1st to 15thNight
8%5%37%6%335%7%10%38%
1668
16th to endNight
10%6%26%5%3448%10%37%
1910
September1st to 15thNight
12%6%2443445%7%43%
1800
16th to endNight
17%5%36%5%2435%7%37%
1964
October1st to 15thNight
16%6%24423445%46%
2160
16th to endNight
13%413322345%54%
2304
November1st to 15thNight
17%413323346%48%
2372
16th to endNight
14%424323446%48%
2581
December1st to 15thNight
14%6%25%434346%42%
2546
16th to endNight
18%7%23323346%44%
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
40%5%8%20%20%4
1586
16th to endDay
39%49%22%19%5%
1728
February1st to 15thDay
41%37%23%20%5%
1598
16th to endDay
38%5%10%21%20%3
1580
March1st to 15thDay
37%5%9%22%19%5%
1956
16th to endDay
43%5%8%19%19%4
2140
April1st to 15thDay
33%49%25%20%6%
2152
16th to endDay
38%7%10%17%18%7%
2160
May1st to 15thDay
44%6%12%21%13%1
2215
16th to endDay
39%8%12%24%12%2
2579
June1st to 15thDay
37%9%13%23%14%1
2520
16th to endDay
39%9%14%21%13%2
2520
July1st to 15thDay
38%12%16%19%10%2
2301
16th to endDay
41%9%16%19%10%2
2310
August1st to 15thDay
45%10%12%18%11%1
2267
16th to endDay
45%10%13%17%11%2
2292
September1st to 15thDay
42%8%12%17%16%3
2160
16th to endDay
52%5%10%15%14%
1993
October1st to 15thDay
44%36%22%20%3
1800
16th to endDay
33%45%23%27%5%
1920
November1st to 15thDay
40%49%21%20%4
1815
16th to endDay
33%48%23%23%6%
1706
December1st to 15thDay
39%5%9%22%17%5%
1451
16th to endDay
43%49%22%15%4
1536
January1st to 15thNight
40%5%9%18%19%6%
2351
16th to endNight
42%48%21%17%5%
2496
February1st to 15thNight
41%37%20%20%5%
2264
16th to endNight
35%49%24%19%6%
1893
March1st to 15thNight
38%5%10%22%17%5%
2001
16th to endNight
41%5%9%21%18%3
2082
April1st to 15thNight
37%6%11%18%20%5%
1796
16th to endNight
38%410%20%19%6%
1800
May1st to 15thNight
41%8%13%21%12%2
1746
16th to endNight
33%10%16%25%13%2
1537
June1st to 15thNight
36%8%16%24%13%1
1440
16th to endNight
33%11%15%20%14%2
1440
July1st to 15thNight
36%12%16%21%11%1
1426
16th to endNight
31%12%17%25%11%2
1595
August1st to 15thNight
39%9%19%17%13%
1657
16th to endNight
39%9%14%24%10%1
1910
September1st to 15thNight
39%7%15%17%16%3
1800
16th to endNight
44%7%10%15%19%1
1964
October1st to 15thNight
40%5%8%21%21%3
2160
16th to endNight
32%47%22%26%7%
2304
November1st to 15thNight
37%410%18%23%5%
2372
16th to endNight
36%5%6%22%22%7%
2581
December1st to 15thNight
41%6%10%19%17%4
2546
16th to endNight
41%411%22%16%4
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
23%20%43%12%
86
16th to endDay
26%32%29%12%
96
February1st to 15thDay
18%29%35%12%3
112
16th to endDay
17%17%39%18%5%
239
March1st to 15thDay
17%18%34%20%8%
270
16th to endDay
20%15%31%21%9%2
288
April1st to 15thDay
17%12%34%18%12%3
270
16th to endDay
15%7%35%24%14%3
270
May1st to 15thDay
22%12%31%21%9%2
288
16th to endDay
17%420%28%23%5%
331
June1st to 15thDay
14%5%19%29%26%5%
315
16th to endDay
11%323%35%20%5%
315
July1st to 15thDay
10%116%37%27%6%
305
16th to endDay
8%11%37%30%12%
326
August1st to 15thDay
14%115%30%26%11%
313
16th to endDay
12%11%28%32%14%
332
September1st to 15thDay
17%318%26%18%16%
315
16th to endDay
27%316%21%21%9%
314
October1st to 15thDay
25%6%20%22%18%6%
315
16th to endDay
11%8%29%22%20%5%
336
November1st to 15thDay
21%5%28%25%15%3
303
16th to endDay
16%15%26%22%16%2
236
December1st to 15thDay
19%17%34%14%12%1
63
16th to endDay
28%17%25%25%4
64
January1st to 15thNight
17%17%33%25%6%
720
16th to endNight
20%13%37%25%1
768
February1st to 15thNight
21%14%39%22%1
704
16th to endNight
18%17%38%22%2
631
March1st to 15thNight
17%13%37%26%5%
720
16th to endNight
21%9%34%26%7%
768
April1st to 15thNight
14%13%42%22%5%
718
16th to endNight
17%8%35%29%8%
720
May1st to 15thNight
16%8%33%32%7%
666
16th to endNight
11%420%47%14%
415
June1st to 15thNight
9%220%47%19%1
360
16th to endNight
7%23%48%20%
360
July1st to 15thNight
10%16%47%22%2
406
16th to endNight
7%115%40%31%3
564
August1st to 15thNight
11%13%46%26%2
587
16th to endNight
12%111%38%32%3
764
September1st to 15thNight
15%116%35%26%3
720
16th to endNight
20%416%32%23%1
717
October1st to 15thNight
19%322%30%20%2
720
16th to endNight
15%8%30%25%18%2
768
November1st to 15thNight
19%6%26%31%13%2
760
16th to endNight
16%11%28%28%14%
780
December1st to 15thNight
18%9%30%30%10%
728
16th to endNight
22%12%31%27%5%
768
Page generated at 2017-12-03 11:16:41. Version ac04

Copyright 2017 A. Danko


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