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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 2019-09-17.

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%
18215
22%
54928
19%
18179
62%
18179
31%
33374

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%
836
15%
2717
14%
836
54%
836
20%
1851
January16th to endNight
51%
896
14%
2912
15%
896
53%
896
19%
2031
February1st to 15thNight
52%
818
15%
2675
15%
818
55%
818
21%
1822
February16th to endNight
47%
736
20%
2207
18%
736
51%
736
22%
1501
March1st to 15thNight
50%
840
19%
2370
15%
840
56%
840
27%
1576
March16th to endNight
49%
896
19%
2464
13%
896
53%
896
28%
1630
April1st to 15thNight
46%
772
19%
2174
12%
772
50%
772
27%
1411
April16th to endNight
52%
624
23%
1872
16%
624
57%
624
29%
1156
May1st to 15thNight
60%
629
24%
1889
19%
629
63%
629
33%
1109
May16th to endNight
61%
657
17%
1973
16%
657
63%
657
31%
1197
June1st to 15thNight
66%
630
22%
1890
22%
630
69%
630
40%
992
June16th to endNight
68%
506
28%
1766
28%
506
77%
506
53%
736
July1st to 15thNight
69%
547
21%
1747
21%
547
73%
547
38%
931
July16th to endNight
73%
660
23%
1881
21%
627
74%
627
44%
1004
August1st to 15thNight
67%
620
28%
1854
19%
617
73%
617
43%
982
August16th to endNight
72%
669
35%
2007
28%
669
76%
669
48%
1013
September1st to 15thNight
74%
824
31%
2291
24%
824
79%
824
50%
1196
September16th to endNight
73%
780
36%
2157
29%
780
75%
780
52%
1103
October1st to 15thNight
63%
780
29%
2259
23%
780
68%
780
39%
1278
October16th to endNight
66%
832
31%
2519
28%
832
70%
832
39%
1395
November1st to 15thNight
58%
820
25%
2665
25%
820
61%
820
28%
1598
November16th to endNight
57%
861
23%
2751
21%
861
61%
861
29%
1644
December1st to 15thNight
52%
1050
14%
2940
12%
1050
53%
1050
25%
2022
December16th to endNight
41%
932
14%
2948
13%
932
43%
932
15%
2196

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%244345%5%7%48%
55732
Night
7%7%25%42445%7%47%
55123
TransparencyDay
34%5%9%19%19%10%
55427
Night
35%5%10%21%17%9%
54929
SeeingDay
9%11%29%32%14%3
7962
Night
10%5%16%34%25%6%
18228

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%6%48%26%
1881
16th to endDay
10%14%5%7%7%45%6%48%25%
2016
February1st to 15thDay
10%11%47%5%3445%8%32%
1845
16th to endDay
6%13%5%8%6%36%5%5%7%31%
1839
March1st to 15thDay
6%8%26%5%35%5%5%8%40%
2250
16th to endDay
9%9%25%6%35%7%5%8%35%
2464
April1st to 15thDay
11%9%35%5%36%5%5%6%39%
2431
16th to endDay
7%6%2442435%7%49%
2693
May1st to 15thDay
6%42442445%10%49%
2721
16th to endDay
8%5%245%35%5%7%7%44%
2845
June1st to 15thDay
43134245%47%58%
2730
16th to endDay
212211235%75%
2842
July1st to 15thDay
221332445%8%60%
2772
16th to endDay
22133245%6%7%59%
2883
August1st to 15thDay
22133245%6%8%59%
2680
16th to endDay
22422345%6%65%
2899
September1st to 15thDay
22132135%46%67%
2326
16th to endDay
6%22213335%67%
2157
October1st to 15thDay
7%5%143345%5%7%50%
2031
16th to endDay
6%4133245%5%7%54%
2054
November1st to 15thDay
9%7%23434437%47%
1854
16th to endDay
9%9%36%5%23447%43%
1851
December1st to 15thDay
10%12%5%8%5%3445%8%31%
1680
16th to endDay
12%16%5%8%6%35%45%6%24%
1988
January1st to 15thNight
11%10%37%6%35%5%5%7%33%
2717
16th to endNight
10%13%35%7%35%5%6%6%31%
2912
February1st to 15thNight
9%11%36%5%35%5%5%7%37%
2664
16th to endNight
5%14%5%7%5%2445%6%37%
2207
March1st to 15thNight
7%10%35%5%35%447%40%
2370
16th to endNight
7%9%36%435%6%7%7%39%
2464
April1st to 15thNight
11%9%25%423346%45%
2174
16th to endNight
9%6%245%235%5%7%46%
1872
May1st to 15thNight
6%434425%46%8%49%
1889
16th to endNight
9%415%5%445%6%9%44%
1972
June1st to 15thNight
431342345%7%59%
1890
16th to endNight
11231335%7%68%
1766
July1st to 15thNight
3214435%5%5%8%54%
1837
16th to endNight
421343446%8%55%
1989
August1st to 15thNight
321242447%9%56%
1863
16th to endNight
221332346%7%61%
2007
September1st to 15thNight
3213323347%64%
2291
16th to endNight
6%212213235%69%
2157
October1st to 15thNight
7%413423346%57%
2259
16th to endNight
6%41432345%7%56%
2519
November1st to 15thNight
9%8%25%41435%6%47%
2665
16th to endNight
8%7%345%2345%7%46%
2751
December1st to 15thNight
11%11%35%5%2445%6%38%
2940
16th to endNight
14%15%5%7%5%25%446%27%
2948

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%8%18%15%3
1882
16th to endDay
53%7%16%14%7%
2016
February1st to 15thDay
51%7%12%19%8%
1845
16th to endDay
53%5%14%19%6%
1839
March1st to 15thDay
41%7%14%22%12%1
2250
16th to endDay
46%6%13%22%8%2
2464
April1st to 15thDay
46%6%11%19%14%2
2431
16th to endDay
35%5%11%23%21%2
2693
May1st to 15thDay
31%6%6%27%22%5%
2721
16th to endDay
37%6%10%20%19%4
2848
June1st to 15thDay
23%5%7%19%31%11%
2730
16th to endDay
13%3313%32%34%
2842
July1st to 15thDay
21%45%14%25%28%
2633
16th to endDay
22%46%12%24%29%
2728
August1st to 15thDay
21%5%5%16%23%27%
2665
16th to endDay
20%4315%33%21%
2899
September1st to 15thDay
18%5%5%17%30%22%
2326
16th to endDay
20%45%20%30%18%
2157
October1st to 15thDay
34%46%24%24%4
2031
16th to endDay
28%6%11%27%23%2
2054
November1st to 15thDay
37%5%12%25%16%2
1854
16th to endDay
42%5%13%24%13%
1851
December1st to 15thDay
50%7%18%19%4
1680
16th to endDay
58%7%11%17%4
1988
January1st to 15thNight
47%6%16%21%6%1
2717
16th to endNight
48%7%16%17%8%1
2912
February1st to 15thNight
45%7%14%21%10%
2675
16th to endNight
46%5%10%26%9%1
2207
March1st to 15thNight
42%412%25%12%2
2370
16th to endNight
40%5%12%25%12%3
2464
April1st to 15thNight
40%410%24%16%4
2174
16th to endNight
37%5%10%22%22%2
1872
May1st to 15thNight
31%6%6%25%24%5%
1890
16th to endNight
34%6%11%25%16%5%
1973
June1st to 15thNight
24%5%7%20%28%13%
1890
16th to endNight
15%3413%28%34%
1766
July1st to 15thNight
27%45%13%19%29%
1747
16th to endNight
24%47%13%20%29%
1881
August1st to 15thNight
23%5%6%16%21%26%
1854
16th to endNight
21%4412%31%25%
2007
September1st to 15thNight
21%3416%27%26%
2291
16th to endNight
20%3416%30%24%
2157
October1st to 15thNight
29%38%25%25%7%
2259
16th to endNight
27%5%8%26%28%4
2519
November1st to 15thNight
36%5%9%24%18%5%
2665
16th to endNight
36%5%11%28%15%2
2751
December1st to 15thNight
44%6%17%22%8%
2940
16th to endNight
57%5%12%18%5%
2948

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%7%20%27%22%3
180
16th to endDay
22%6%20%33%13%3
192
February1st to 15thDay
15%17%21%28%14%2
180
16th to endDay
9%17%40%26%4
342
March1st to 15thDay
11%15%37%26%7%
390
16th to endDay
15%21%33%22%5%
416
April1st to 15thDay
20%18%28%23%7%1
389
16th to endDay
15%21%27%24%10%
378
May1st to 15thDay
8%13%37%25%12%3
408
16th to endDay
11%14%23%30%16%3
458
June1st to 15thDay
411%33%32%13%3
435
16th to endDay
29%35%34%13%4
435
July1st to 15thDay
2426%43%19%4
425
16th to endDay
3231%45%14%3
455
August1st to 15thDay
45%29%43%14%3
419
16th to endDay
4326%40%20%4
460
September1st to 15thDay
5%7%27%35%19%5%
435
16th to endDay
8%7%23%36%18%5%
380
October1st to 15thDay
9%14%32%24%16%2
261
16th to endDay
7%8%20%35%26%1
192
November1st to 15thDay
10%8%26%27%20%7%
180
16th to endDay
22%12%15%26%17%6%
180
December1st to 15thDay
15%7%25%35%10%5%
180
16th to endDay
20%9%21%36%10%
192
January1st to 15thNight
15%6%13%35%22%6%
840
16th to endNight
16%7%13%31%23%7%
896
February1st to 15thNight
14%5%16%39%19%5%
824
16th to endNight
12%6%20%36%21%2
736
March1st to 15thNight
11%7%20%37%19%4
840
16th to endNight
11%8%23%36%14%4
896
April1st to 15thNight
16%10%21%31%16%2
772
16th to endNight
12%6%20%36%18%4
624
May1st to 15thNight
8%6%17%38%24%4
630
16th to endNight
11%5%15%30%31%7%
659
June1st to 15thNight
5%8%13%38%29%4
630
16th to endNight
2419%35%31%5%
506
July1st to 15thNight
5%314%30%38%7%
547
16th to endNight
5%112%33%43%3
660
August1st to 15thNight
4219%39%32%3
620
16th to endNight
3215%34%36%7%
669
September1st to 15thNight
3213%34%34%10%
824
16th to endNight
6%412%30%31%15%
780
October1st to 15thNight
9%5%16%35%25%9%
780
16th to endNight
8%415%31%29%10%
832
November1st to 15thNight
13%7%14%32%23%8%
820
16th to endNight
11%6%16%35%20%9%
861
December1st to 15thNight
16%5%16%37%19%3
1050
16th to endNight
20%8%18%35%15%2
932
Page generated at 2019-09-17 19:12:17. Version ac04

Copyright 2019 A. Danko


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