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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 2018-02-14.

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
58%
16209
22%
48906
19%
16173
62%
16173
31%
29727

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
51%
776
14%
2522
14%
776
53%
776
20%
1713
January16th to endNight
51%
832
14%
2704
15%
832
53%
832
19%
1882
February1st to 15thNight
53%
754
13%
2467
14%
754
56%
754
21%
1676
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%
539
28%
1611
19%
536
74%
536
43%
864
August16th to endNight
72%
573
36%
1719
29%
573
76%
573
46%
875
September1st to 15thNight
74%
706
29%
1963
22%
706
79%
706
49%
1041
September16th to endNight
72%
716
37%
1980
31%
716
75%
716
51%
1024
October1st to 15thNight
65%
720
29%
2085
23%
720
69%
720
41%
1154
October16th to endNight
65%
768
32%
2325
28%
768
69%
768
38%
1300
November1st to 15thNight
57%
760
23%
2470
23%
760
60%
760
28%
1486
November16th to endNight
57%
800
24%
2555
22%
800
62%
800
29%
1523
December1st to 15thNight
52%
975
14%
2730
12%
975
53%
975
26%
1861
December16th to endNight
41%
865
14%
2737
13%
865
43%
865
15%
2038

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%
49145
Night
7%7%25%42445%7%47%
49101
TransparencyDay
34%5%9%19%19%10%
48840
Night
35%5%10%21%17%9%
48907
SeeingDay
9%11%30%32%13%2
5804
Night
10%6%17%34%25%6%
16222

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%12%49%7%46%5%48%27%
1746
16th to endDay
9%13%5%6%8%45%6%5%8%25%
1872
February1st to 15thDay
10%11%48%5%3445%8%32%
1693
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%
2340
16th to endDay
22432345%6%64%
2483
September1st to 15thDay
221331345%6%65%
1994
16th to endDay
6%22313346%65%
1980
October1st to 15thDay
7%4143345%5%7%52%
1875
16th to endDay
7%5%133245%47%53%
1896
November1st to 15thDay
10%7%23434437%46%
1719
16th to endDay
8%9%46%5%23447%43%
1719
December1st to 15thDay
10%12%5%7%5%3445%8%31%
1560
16th to endDay
12%16%5%7%6%35%45%6%24%
1846
January1st to 15thNight
12%10%47%6%35%447%33%
2522
16th to endNight
10%13%46%7%35%5%6%6%31%
2704
February1st to 15thNight
9%11%36%5%35%5%5%6%37%
2456
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%
1620
16th to endNight
321432346%7%61%
1719
September1st to 15thNight
3213323347%62%
1963
16th to endNight
6%212212235%67%
1980
October1st to 15thNight
5%413324346%58%
2085
16th to endNight
6%42432345%7%55%
2325
November1st to 15thNight
9%9%25%414347%47%
2470
16th to endNight
7%8%345%2345%7%46%
2555
December1st to 15thNight
11%10%35%42345%6%39%
2730
16th to endNight
14%15%6%7%5%25%446%27%
2737

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
52%7%18%16%4
1747
16th to endDay
52%7%15%14%8%1
1872
February1st to 15thDay
50%7%13%18%8%
1693
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%28%
2325
16th to endDay
21%4416%31%22%
2483
September1st to 15thDay
20%5%5%18%28%21%
1994
16th to endDay
21%5%5%21%30%16%
1980
October1st to 15thDay
32%46%25%25%4
1875
16th to endDay
28%6%11%26%24%2
1896
November1st to 15thDay
38%5%12%24%16%2
1719
16th to endDay
40%5%14%25%12%
1719
December1st to 15thDay
49%7%18%19%5%
1560
16th to endDay
58%7%12%17%4
1846
January1st to 15thNight
47%6%17%21%6%1
2522
16th to endNight
47%7%15%18%8%1
2704
February1st to 15thNight
45%7%15%21%10%
2467
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%6%6%15%21%27%
1611
16th to endNight
22%4412%30%26%
1719
September1st to 15thNight
22%35%16%25%26%
1963
16th to endNight
21%3417%30%22%
1980
October1st to 15thNight
27%38%26%25%8%
2085
16th to endNight
27%5%7%24%29%4
2325
November1st to 15thNight
37%5%9%23%17%6%
2470
16th to endNight
35%5%12%28%15%2
2555
December1st to 15thNight
43%6%17%23%8%
2730
16th to endNight
57%5%13%17%5%
2737

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
18%10%20%25%22%2
135
16th to endDay
18%7%17%38%14%3
144
February1st to 15thDay
15%10%20%34%16%3
130
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%29%44%14%2
315
16th to endDay
4424%40%21%4
332
September1st to 15thDay
5%8%28%36%14%6%
315
16th to endDay
10%6%20%39%18%4
315
October1st to 15thDay
6%13%32%25%19%2
210
16th to endDay
9%9%21%34%24%2
144
November1st to 15thDay
8%10%24%28%19%8%
135
16th to endDay
19%15%17%28%15%2
135
December1st to 15thDay
16%6%29%31%9%6%
135
16th to endDay
19%9%19%37%13%
144
January1st to 15thNight
15%7%13%34%23%6%
780
16th to endNight
15%7%13%30%24%7%
832
February1st to 15thNight
14%316%40%19%5%
760
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
539
16th to endNight
4215%31%38%8%
573
September1st to 15thNight
3213%34%34%11%
706
16th to endNight
6%411%29%31%16%
716
October1st to 15thNight
7%5%16%35%25%9%
720
16th to endNight
8%5%16%30%28%10%
768
November1st to 15thNight
13%7%15%30%24%8%
760
16th to endNight
10%7%17%36%19%8%
800
December1st to 15thNight
16%5%17%36%19%3
975
16th to endNight
20%8%18%34%15%2
865
Page generated at 2018-02-15 08:58:49. Version ac04

Copyright 2018 A. Danko


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