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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 2017-02-18.

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%
14905
22%
44969
19%
14869
61%
14869
30%
27475

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
49%
588
20%
1763
18%
588
54%
588
25%
1155
March1st to 15thNight
51%
660
19%
1862
15%
660
57%
660
28%
1228
March16th to endNight
48%
704
19%
1936
13%
704
53%
704
28%
1285
April1st to 15thNight
45%
607
20%
1709
13%
607
49%
607
27%
1116
April16th to endNight
51%
495
23%
1485
16%
495
56%
495
29%
916
May1st to 15thNight
57%
494
25%
1484
19%
494
60%
494
32%
887
May16th to endNight
61%
513
17%
1541
15%
513
63%
513
32%
921
June1st to 15thNight
64%
495
21%
1485
20%
495
68%
495
36%
816
June16th to endNight
68%
398
27%
1388
28%
398
76%
398
52%
583
July1st to 15thNight
68%
424
20%
1354
20%
424
72%
424
38%
714
July16th to endNight
73%
522
24%
1467
22%
489
74%
489
45%
774
August1st to 15thNight
67%
494
30%
1476
20%
491
73%
491
44%
780
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%2443445%7%48%
45174
Night
7%7%25%42445%7%47%
45164
TransparencyDay
34%5%9%19%19%11%
44869
Night
36%5%10%20%17%9%
44970
SeeingDay
8%12%32%32%11%2
4498
Night
10%6%17%33%25%6%
14918

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%35%45%8%35%
1470
March1st to 15thDay
6%8%25%5%35%5%48%42%
1768
16th to endDay
8%9%25%6%35%6%6%9%35%
1936
April1st to 15thDay
8%8%35%426%5%5%7%40%
1908
16th to endDay
6%6%25%42436%8%49%
2145
May1st to 15thDay
6%4245%2435%10%48%
2136
16th to endDay
7%5%245%35%5%7%7%45%
2221
June1st to 15thDay
43134246%5%7%54%
2145
16th to endDay
21221123475%
2233
July1st to 15thDay
221322445%7%62%
2178
16th to endDay
321332445%7%61%
2285
August1st to 15thDay
21133245%6%8%59%
2145
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%12%36%5%2445%6%41%
1763
March1st to 15thNight
7%10%46%435%45%8%40%
1862
16th to endNight
5%9%36%435%6%7%7%39%
1936
April1st to 15thNight
10%8%25%5%24346%46%
1709
16th to endNight
9%6%345%2346%7%45%
1485
May1st to 15thNight
7%435%42445%8%48%
1484
16th to endNight
8%415%44446%10%45%
1540
June1st to 15thNight
431343446%7%55%
1485
16th to endNight
211222226%7%68%
1388
July1st to 15thNight
3214425%45%8%56%
1444
16th to endNight
421332446%8%58%
1575
August1st to 15thNight
321243446%9%57%
1485
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
49%415%21%7%
1470
March1st to 15thDay
40%6%14%23%14%1
1768
16th to endDay
45%6%12%22%9%3
1936
April1st to 15thDay
43%6%11%19%15%2
1908
16th to endDay
34%5%10%25%21%2
2145
May1st to 15thDay
32%5%7%24%22%6%
2136
16th to endDay
37%6%9%20%21%5%
2224
June1st to 15thDay
27%5%7%18%30%11%
2145
16th to endDay
14%2210%31%37%
2233
July1st to 15thDay
21%45%13%24%31%
2039
16th to endDay
22%35%12%22%33%
2130
August1st to 15thDay
21%5%5%15%21%29%
2130
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
42%5%12%28%9%1
1763
March1st to 15thNight
42%413%24%12%2
1862
16th to endNight
40%5%12%24%12%4
1936
April1st to 15thNight
40%49%23%16%5%
1709
16th to endNight
37%410%21%22%2
1485
May1st to 15thNight
33%5%7%21%26%5%
1485
16th to endNight
34%5%11%26%16%6%
1541
June1st to 15thNight
27%5%7%18%28%12%
1485
16th to endNight
16%2310%29%37%
1388
July1st to 15thNight
27%45%12%18%32%
1354
16th to endNight
23%46%12%20%32%
1467
August1st to 15thNight
23%5%6%15%21%27%
1476
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
6%18%43%25%5%1
195
March1st to 15thDay
13%13%43%24%4
210
16th to endDay
12%23%40%22%1
224
April1st to 15thDay
13%23%29%23%7%3
209
16th to endDay
12%25%31%23%7%
210
May1st to 15thDay
8%19%39%25%6%
228
16th to endDay
9%15%24%32%16%1
266
June1st to 15thDay
5%12%39%30%9%1
255
16th to endDay
37%39%35%10%3
255
July1st to 15thDay
15%34%42%14%1
245
16th to endDay
1341%43%7%1
271
August1st to 15thDay
46%30%42%13%2
255
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%6%21%34%22%3
588
March1st to 15thNight
10%7%21%37%18%5%
660
16th to endNight
10%9%25%33%16%4
704
April1st to 15thNight
15%11%23%28%17%3
607
16th to endNight
12%6%21%35%19%4
495
May1st to 15thNight
9%7%18%37%22%3
495
16th to endNight
10%5%17%30%30%6%
515
June1st to 15thNight
49%14%40%26%3
495
16th to endNight
3418%35%32%6%
398
July1st to 15thNight
5%314%31%38%6%
424
16th to endNight
4112%32%44%4
522
August1st to 15thNight
4119%40%30%3
494
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 2017-02-18 14:04:33. Version ac04

Copyright 2017 A. Danko


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