Stansbury Park Observatory Complex (SPOC)
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stansbury Park Observatory Complex (SPOC) clear sky chart from 2005-11-05 to 2017-08-12.

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
57%
15463
22%
46632
19%
15427
61%
15427
31%
28428

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
49%
716
15%
2327
15%
716
51%
716
19%
1596
January16th to endNight
51%
768
15%
2496
15%
768
53%
768
19%
1753
February1st to 15thNight
53%
698
13%
2285
15%
698
55%
698
21%
1559
February16th to endNight
48%
632
20%
1895
18%
632
53%
632
24%
1255
March1st to 15thNight
52%
720
20%
2031
15%
720
57%
720
29%
1322
March16th to endNight
48%
768
20%
2112
13%
768
53%
768
27%
1406
April1st to 15thNight
46%
662
19%
1864
12%
662
50%
662
28%
1199
April16th to endNight
50%
540
24%
1620
16%
540
56%
540
28%
1007
May1st to 15thNight
58%
539
23%
1619
18%
539
62%
539
34%
947
May16th to endNight
62%
561
19%
1685
18%
561
64%
561
33%
996
June1st to 15thNight
63%
540
20%
1620
19%
540
67%
540
37%
876
June16th to endNight
70%
434
29%
1514
31%
434
78%
434
53%
628
July1st to 15thNight
68%
465
19%
1485
19%
465
72%
465
37%
802
July16th to endNight
73%
564
24%
1593
22%
531
74%
531
43%
852
August1st to 15thNight
68%
527
28%
1575
20%
524
74%
524
44%
838
August16th to endNight
71%
525
34%
1575
26%
525
75%
525
46%
801
September1st to 15thNight
73%
647
31%
1799
23%
647
78%
647
48%
960
September16th to endNight
72%
656
36%
1815
30%
656
75%
656
53%
918
October1st to 15thNight
65%
660
30%
1911
23%
660
70%
660
41%
1067
October16th to endNight
63%
704
29%
2131
25%
704
67%
704
36%
1224
November1st to 15thNight
57%
700
23%
2275
23%
700
60%
700
28%
1369
November16th to endNight
57%
738
24%
2358
22%
738
61%
738
30%
1393
December1st to 15thNight
49%
900
12%
2520
10%
900
51%
900
24%
1756
December16th to endNight
39%
799
14%
2527
13%
799
42%
799
14%
1904

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%6%2442445%7%49%
47316
Night
7%7%25%42445%7%47%
46827
TransparencyDay
34%5%9%19%19%11%
47011
Night
36%5%10%21%17%9%
46633
SeeingDay
8%12%31%32%12%2
5190
Night
10%6%17%34%25%6%
15476

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
9%13%410%7%46%5%48%26%
1611
16th to endDay
9%14%5%6%8%45%6%5%8%25%
1728
February1st to 15thDay
10%11%48%5%3445%8%33%
1575
16th to endDay
6%12%5%7%5%36%5%5%7%34%
1579
March1st to 15thDay
6%8%26%5%35%5%48%44%
1929
16th to endDay
9%9%25%6%35%7%5%8%35%
2112
April1st to 15thDay
8%8%35%426%5%5%7%42%
2083
16th to endDay
7%7%25%42435%7%47%
2340
May1st to 15thDay
5%42442436%10%50%
2331
16th to endDay
7%4245%35%5%6%7%46%
2429
June1st to 15thDay
43134245%5%7%56%
2340
16th to endDay
212211235%76%
2436
July1st to 15thDay
221332445%8%61%
2376
16th to endDay
22133245%6%7%59%
2467
August1st to 15thDay
21133245%6%8%59%
2290
16th to endDay
22432235%6%64%
2275
September1st to 15thDay
221331345%6%65%
1828
16th to endDay
5%12312346%67%
1815
October1st to 15thDay
7%5%24335%5%5%7%50%
1719
16th to endDay
7%5%233245%5%8%51%
1738
November1st to 15thDay
10%6%23434437%47%
1584
16th to endDay
8%9%46%5%23437%43%
1587
December1st to 15thDay
11%13%5%7%5%3445%9%28%
1440
16th to endDay
12%17%5%7%6%45%45%7%23%
1704
January1st to 15thNight
12%10%47%6%35%447%33%
2327
16th to endNight
10%13%46%8%35%5%6%6%30%
2496
February1st to 15thNight
9%11%36%5%35%5%5%6%36%
2274
16th to endNight
5%13%46%5%2445%6%40%
1895
March1st to 15thNight
7%9%45%5%35%45%7%42%
2031
16th to endNight
6%9%36%435%6%7%7%39%
2112
April1st to 15thNight
9%8%25%423346%47%
1864
16th to endNight
10%6%245%235%5%7%44%
1620
May1st to 15thNight
7%435%42445%7%50%
1619
16th to endNight
8%41444445%9%47%
1684
June1st to 15thNight
431342446%7%57%
1620
16th to endNight
11221225%7%69%
1514
July1st to 15thNight
3215%435%45%8%54%
1575
16th to endNight
421333446%8%56%
1701
August1st to 15thNight
32124345%6%9%56%
1584
16th to endNight
321432345%7%61%
1575
September1st to 15thNight
3214333347%62%
1799
16th to endNight
5%212212235%69%
1815
October1st to 15thNight
6%423324346%57%
1911
16th to endNight
7%5%2432345%6%53%
2131
November1st to 15thNight
9%9%25%414347%47%
2275
16th to endNight
7%8%335%2345%7%48%
2358
December1st to 15thNight
12%11%35%5%2445%7%37%
2520
16th to endNight
14%15%6%7%5%25%446%26%
2527

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
53%7%18%15%3
1612
16th to endDay
52%7%15%14%8%1
1728
February1st to 15thDay
50%7%12%19%8%
1575
16th to endDay
50%5%14%21%7%
1579
March1st to 15thDay
39%6%15%23%14%1
1929
16th to endDay
46%5%12%22%9%3
2112
April1st to 15thDay
42%6%10%21%16%2
2083
16th to endDay
36%5%9%24%21%2
2340
May1st to 15thDay
30%5%7%26%23%6%
2331
16th to endDay
36%5%9%21%21%4
2432
June1st to 15thDay
26%5%7%19%30%11%
2340
16th to endDay
13%2310%31%38%
2436
July1st to 15thDay
21%45%13%24%30%
2237
16th to endDay
23%46%12%22%31%
2312
August1st to 15thDay
21%6%5%15%21%29%
2275
16th to endDay
21%4415%31%23%
2275
September1st to 15thDay
20%5%5%17%30%20%
1828
16th to endDay
19%45%20%31%17%
1815
October1st to 15thDay
34%5%7%27%21%4
1719
16th to endDay
30%6%11%26%23%1
1738
November1st to 15thDay
38%5%12%23%16%3
1584
16th to endDay
41%5%13%24%13%
1587
December1st to 15thDay
51%7%19%18%3
1440
16th to endDay
59%7%12%16%31
1704
January1st to 15thNight
48%6%16%21%5%1
2327
16th to endNight
48%7%14%17%9%2
2496
February1st to 15thNight
46%7%13%22%10%
2285
16th to endNight
44%5%11%27%10%1
1895
March1st to 15thNight
41%413%25%13%2
2031
16th to endNight
41%6%11%25%12%3
2112
April1st to 15thNight
39%49%24%17%4
1864
16th to endNight
38%5%10%22%21%2
1620
May1st to 15thNight
31%5%6%23%26%5%
1620
16th to endNight
33%5%10%26%17%6%
1685
June1st to 15thNight
26%5%7%19%28%12%
1620
16th to endNight
15%2311%28%37%
1514
July1st to 15thNight
28%4412%18%31%
1485
16th to endNight
24%5%6%12%20%30%
1593
August1st to 15thNight
23%5%5%15%21%27%
1575
16th to endNight
22%35%12%29%26%
1575
September1st to 15thNight
23%3416%27%25%
1799
16th to endNight
20%2417%30%24%
1815
October1st to 15thNight
28%39%27%24%7%
1911
16th to endNight
29%6%7%24%28%3
2131
November1st to 15thNight
37%5%10%23%17%6%
2275
16th to endNight
35%5%12%28%15%2
2358
December1st to 15thNight
45%6%17%22%7%
2520
16th to endNight
58%5%12%17%5%
2527

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
22%8%25%25%16%1
90
16th to endDay
21%7%13%35%18%3
96
February1st to 15thDay
16%6%18%32%22%3
90
16th to endDay
9%19%42%23%41
238
March1st to 15thDay
10%14%38%27%7%
270
16th to endDay
15%22%36%22%3
288
April1st to 15thDay
13%23%30%22%8%2
269
16th to endDay
17%23%29%23%6%
270
May1st to 15thDay
6%18%39%25%8%
288
16th to endDay
8%15%23%32%16%2
330
June1st to 15thDay
5%13%37%30%11%1
315
16th to endDay
26%37%35%13%4
315
July1st to 15thDay
428%43%18%4
305
16th to endDay
2337%44%9%2
327
August1st to 15thDay
45%30%43%13%2
300
16th to endDay
45%28%42%15%3
268
September1st to 15thDay
49%34%39%9%2
255
16th to endDay
6%7%20%41%18%5%
255
October1st to 15thDay
8%12%27%25%22%3
159
16th to endDay
12%11%23%32%17%2
96
November1st to 15thDay
8%11%15%24%26%13%
90
16th to endDay
22%15%24%26%7%3
90
December1st to 15thDay
22%8%35%28%4
90
16th to endDay
19%12%16%37%13%
96
January1st to 15thNight
15%7%14%34%22%5%
720
16th to endNight
15%8%13%29%25%7%
768
February1st to 15thNight
14%316%38%20%6%
704
16th to endNight
11%7%21%34%21%3
632
March1st to 15thNight
10%7%21%37%19%4
720
16th to endNight
11%8%25%34%15%4
768
April1st to 15thNight
15%11%22%30%17%3
662
16th to endNight
13%6%21%36%18%4
540
May1st to 15thNight
8%7%18%38%21%4
540
16th to endNight
10%415%30%30%7%
563
June1st to 15thNight
49%15%40%27%3
540
16th to endNight
2417%37%32%5%
434
July1st to 15thNight
6%313%30%39%7%
465
16th to endNight
5%112%32%44%4
564
August1st to 15thNight
4118%39%32%3
527
16th to endNight
4216%33%36%7%
525
September1st to 15thNight
3314%36%33%8%
647
16th to endNight
5%412%28%31%17%
656
October1st to 15thNight
7%5%15%34%26%9%
660
16th to endNight
9%5%17%28%28%10%
704
November1st to 15thNight
13%7%14%28%25%9%
700
16th to endNight
10%7%18%35%19%9%
738
December1st to 15thNight
17%5%18%37%18%3
900
16th to endNight
20%9%20%31%15%3
799
Page generated at 2017-08-13 12:16:39. Version ac04

Copyright 2017 A. Danko


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