South Park Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the South Park Observatory clear sky chart from 2005-11-05 to 2017-09-20.

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
50%
15916
27%
46908
16%
15874
61%
15874
42%
24701

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
39%
891
31%
2500
14%
889
54%
889
48%
1207
January16th to endNight
41%
768
34%
2496
19%
768
61%
768
48%
1130
February1st to 15thNight
36%
698
27%
2264
13%
696
53%
696
41%
1112
February16th to endNight
36%
632
34%
1894
12%
632
59%
632
47%
926
March1st to 15thNight
43%
720
29%
2079
13%
720
56%
720
44%
1079
March16th to endNight
37%
701
28%
2045
11%
701
52%
701
42%
1092
April1st to 15thNight
40%
539
25%
1798
14%
539
56%
539
39%
887
April16th to endNight
40%
540
24%
1800
16%
540
55%
540
33%
986
May1st to 15thNight
45%
539
19%
1629
13%
539
54%
539
29%
1003
May16th to endNight
54%
563
18%
1498
10%
561
61%
561
36%
889
June1st to 15thNight
62%
540
25%
1440
17%
540
67%
540
53%
728
June16th to endNight
72%
540
25%
1440
21%
540
75%
540
52%
753
July1st to 15thNight
75%
510
17%
1360
16%
510
75%
510
33%
862
July16th to endNight
75%
564
16%
1495
15%
531
76%
531
32%
912
August1st to 15thNight
72%
539
16%
1653
15%
536
73%
536
29%
987
August16th to endNight
72%
573
23%
1910
25%
573
74%
573
32%
1093
September1st to 15thNight
70%
540
26%
1800
24%
540
75%
540
33%
997
September16th to endNight
63%
526
33%
1823
26%
526
73%
526
42%
892
October1st to 15thNight
50%
660
32%
1980
17%
660
62%
660
46%
1015
October16th to endNight
55%
704
34%
2112
18%
704
68%
704
47%
1052
November1st to 15thNight
49%
869
34%
2269
17%
869
59%
869
52%
1167
November16th to endNight
45%
900
35%
2415
16%
900
58%
900
53%
1185
December1st to 15thNight
35%
900
25%
2520
10%
900
49%
900
43%
1300
December16th to endNight
36%
960
26%
2688
11%
960
49%
960
40%
1447

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
44244345%6%7%52%
47934
Night
231332345%8%61%
47088
TransparencyDay
30%7%13%24%18%5%
47616
Night
21%6%15%29%20%5%
46908
SeeingDay
10%13%25%27%17%5%
5820
Night
48%30%37%16%2
15926

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
32222345%9%62%
1448
16th to endDay
31242445%6%63%
1728
February1st to 15thDay
42332346%7%61%
1596
16th to endDay
21442446%8%59%
1580
March1st to 15thDay
14234245%7%9%56%
1878
16th to endDay
25%2433445%9%52%
2178
April1st to 15thDay
25%24435%46%9%52%
2150
16th to endDay
39%25%5%35%5%6%7%45%
2160
May1st to 15thDay
7%7%35%6%36%5%6%7%41%
2316
16th to endDay
6%6%245%35%6%7%8%42%
2616
June1st to 15thDay
5%3235%36%5%6%8%49%
2520
16th to endDay
4213435%5%6%7%54%
2520
July1st to 15thDay
10%5%15%6%36%7%7%7%38%
2520
16th to endDay
9%5%26%6%45%7%6%8%36%
2567
August1st to 15thDay
11%5%26%7%46%5%6%7%36%
2298
16th to endDay
8%325%6%46%7%7%6%42%
2292
September1st to 15thDay
9%4145%3445%7%49%
2160
16th to endDay
5%313424345%61%
1903
October1st to 15thDay
431242445%7%59%
1650
16th to endDay
231331335%7%62%
1753
November1st to 15thDay
212222346%70%
1583
16th to endDay
213212247%70%
1542
December1st to 15thDay
324314349%62%
1440
16th to endDay
31342346%10%59%
1536
January1st to 15thNight
112223348%68%
2500
16th to endNight
213112245%72%
2496
February1st to 15thNight
224324347%65%
2254
16th to endNight
32331335%7%65%
1894
March1st to 15thNight
41321335%9%63%
2079
16th to endNight
25%24312346%63%
2045
April1st to 15thNight
5%23213448%62%
1798
16th to endNight
5%7%24323347%56%
1800
May1st to 15thNight
7%8%34323348%49%
1628
16th to endNight
7%6%2232346%10%52%
1497
June1st to 15thNight
22122123410%66%
1440
16th to endNight
3112135%6%8%63%
1440
July1st to 15thNight
6%3134246%8%9%47%
1440
16th to endNight
6%313436%8%6%9%46%
1598
August1st to 15thNight
6%5%234246%6%9%48%
1662
16th to endNight
6%3144245%6%8%50%
1910
September1st to 15thNight
7%3134245%5%8%52%
1800
16th to endNight
4313323346%64%
1823
October1st to 15thNight
4212323336%66%
1980
16th to endNight
242321235%6%65%
2112
November1st to 15thNight
211212347%71%
2269
16th to endNight
312212447%69%
2415
December1st to 15thNight
313313348%65%
2520
16th to endNight
314323349%62%
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
18%7%22%31%17%3
1449
16th to endDay
21%417%32%19%4
1728
February1st to 15thDay
22%5%20%32%14%3
1597
16th to endDay
22%7%14%28%22%4
1580
March1st to 15thDay
23%7%14%29%21%2
1878
16th to endDay
29%7%13%29%16%4
2178
April1st to 15thDay
29%7%14%26%16%5%
2150
16th to endDay
37%8%12%24%15%2
2160
May1st to 15thDay
42%7%12%22%15%
2316
16th to endDay
38%8%13%22%13%3
2620
June1st to 15thDay
30%7%12%16%22%10%
2520
16th to endDay
26%6%9%22%23%11%
2520
July1st to 15thDay
41%9%12%15%13%8%
2371
16th to endDay
43%10%15%17%9%4
2407
August1st to 15thDay
45%9%12%13%12%5%
2283
16th to endDay
37%9%11%22%15%3
2292
September1st to 15thDay
34%6%11%17%19%10%
2160
16th to endDay
26%5%9%25%28%4
1903
October1st to 15thDay
25%6%9%24%28%5%
1650
16th to endDay
22%48%29%29%5%
1753
November1st to 15thDay
15%5%14%26%27%10%
1583
16th to endDay
15%411%33%26%7%
1542
December1st to 15thDay
20%7%17%33%17%2
1440
16th to endDay
21%7%21%27%16%5%
1536
January1st to 15thNight
14%5%21%34%19%3
2500
16th to endNight
15%416%32%24%6%
2496
February1st to 15thNight
20%5%16%38%15%3
2264
16th to endNight
18%413%35%23%4
1894
March1st to 15thNight
19%6%12%34%23%3
2079
16th to endNight
23%5%13%35%18%3
2045
April1st to 15thNight
21%5%15%32%20%4
1798
16th to endNight
29%5%14%31%16%2
1800
May1st to 15thNight
35%6%14%26%15%1
1629
16th to endNight
28%8%18%26%14%3
1498
June1st to 15thNight
16%5%17%26%21%12%
1440
16th to endNight
16%7%13%24%23%13%
1440
July1st to 15thNight
30%11%16%20%13%7%
1360
16th to endNight
29%12%24%21%9%3
1495
August1st to 15thNight
31%10%18%18%15%5%
1653
16th to endNight
29%8%17%23%17%3
1910
September1st to 15thNight
29%7%14%22%16%9%
1800
16th to endNight
22%5%11%32%24%3
1823
October1st to 15thNight
20%5%11%28%27%7%
1980
16th to endNight
19%411%29%30%4
2112
November1st to 15thNight
14%6%12%28%28%10%
2269
16th to endNight
14%412%34%27%7%
2415
December1st to 15thNight
18%6%22%31%19%2
2520
16th to endNight
21%7%19%30%18%3
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
5%25%23%21%17%6%
90
16th to endDay
410%37%34%11%2
96
February1st to 15thDay
6%35%27%25%4
90
16th to endDay
132%25%24%14%1
81
March1st to 15thDay
8%26%32%22%10%
168
16th to endDay
7%31%37%18%5%
288
April1st to 15thDay
7%30%34%17%7%1
269
16th to endDay
17%32%27%17%5%
270
May1st to 15thDay
13%15%29%26%10%2
378
16th to endDay
12%11%25%28%17%4
517
June1st to 15thDay
7%12%23%30%20%5%
495
16th to endDay
46%22%33%24%8%
495
July1st to 15thDay
14%310%31%27%12%
475
16th to endDay
11%116%29%30%11%
426
August1st to 15thDay
19%223%30%17%6%
315
16th to endDay
13%6%19%29%23%7%
332
September1st to 15thDay
13%9%29%25%16%5%
315
16th to endDay
5%11%28%29%16%8%
168
October1st to 15thDay
317%16%28%25%7%
90
16th to endDay
10%10%18%32%25%3
96
November1st to 15thDay
113%23%30%21%11%
90
16th to endDay
7%27%37%21%5%
90
December1st to 15thDay
6%26%33%30%3
90
16th to endDay
215%45%28%5%3
96
January1st to 15thNight
15%39%30%11%2
894
16th to endNight
111%39%37%8%1
768
February1st to 15thNight
111%44%35%6%
704
16th to endNight
110%44%37%5%
632
March1st to 15thNight
210%38%39%8%1
720
16th to endNight
48%43%36%5%
701
April1st to 15thNight
310%40%37%7%
539
16th to endNight
8%9%35%35%9%1
540
May1st to 15thNight
11%6%28%38%13%1
540
16th to endNight
9%5%23%40%17%3
563
June1st to 15thNight
3323%45%20%2
540
16th to endNight
3117%45%27%4
540
July1st to 15thNight
7%15%38%41%5%
510
16th to endNight
6%1435%45%6%
564
August1st to 15thNight
10%5%38%39%5%
539
16th to endNight
8%8%37%38%6%
573
September1st to 15thNight
6%110%46%27%7%
540
16th to endNight
4321%39%24%5%
526
October1st to 15thNight
4434%37%15%3
660
16th to endNight
46%28%41%15%3
704
November1st to 15thNight
111%34%38%12%1
869
16th to endNight
211%36%38%9%1
900
December1st to 15thNight
214%41%34%6%
900
16th to endNight
114%40%33%8%1
960
Page generated at 2017-09-21 05:18:23. Version ac04

Copyright 2017 A. Danko


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