Fox Park Public Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fox Park Public Observatory clear sky chart from 2005-11-06 to 2024-01-11.

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
35%
24544
15%
74635
10%
24487
40%
24487
19%
53041

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 10thNight
18%
950
10%
2648
4%
946
23%
946
10%
2147
January11th to 20thNight
18%
905
7%
2533
3%
905
21%
905
10%
2101
January21st to endNight
20%
940
6%
2722
3%
940
22%
940
10%
2267
February1st to 10thNight
16%
720
7%
2318
3%
720
21%
720
8%
1886
February11th to 20thNight
20%
700
13%
2099
6%
700
27%
700
12%
1630
February21st to endNight
16%
592
13%
1776
3%
592
25%
592
14%
1333
March1st to 10thNight
28%
720
16%
2160
9%
720
34%
720
19%
1503
March11th to 20thNight
29%
720
21%
1998
9%
720
38%
720
23%
1363
March21st to endNight
28%
788
17%
2174
8%
788
35%
788
19%
1566
April1st to 10thNight
25%
540
14%
1800
9%
540
32%
540
19%
1213
April11th to 20thNight
29%
533
19%
1687
10%
533
39%
533
21%
1136
April21st to endNight
34%
540
17%
1620
8%
540
41%
540
23%
1078
May1st to 10thNight
35%
540
13%
1620
7%
540
40%
540
21%
1142
May11th to 20thNight
37%
531
18%
1593
10%
531
45%
531
24%
1054
May21st to endNight
52%
583
14%
1631
11%
582
55%
582
30%
1046
June1st to 10thNight
55%
540
16%
1440
12%
540
60%
540
36%
890
June11th to 20thNight
52%
540
16%
1440
12%
540
56%
540
33%
916
June21st to endNight
57%
540
18%
1440
13%
540
61%
540
34%
899
July1st to 10thNight
68%
525
17%
1400
14%
525
71%
525
42%
826
July11th to 20thNight
63%
522
21%
1392
18%
522
66%
522
41%
833
July21st to endNight
66%
591
21%
1529
16%
558
69%
558
40%
904
August1st to 10thNight
68%
537
21%
1600
18%
534
71%
534
36%
937
August11th to 20thNight
63%
534
22%
1598
18%
534
66%
534
33%
948
August21st to endNight
60%
594
22%
1892
20%
594
63%
594
33%
1090
September1st to 10thNight
58%
589
22%
1849
20%
589
62%
589
30%
1118
September11th to 20thNight
62%
720
29%
1980
24%
720
65%
720
38%
1161
September21st to endNight
49%
720
21%
1980
16%
720
52%
720
29%
1292
October1st to 10thNight
46%
720
21%
1980
16%
720
50%
720
29%
1294
October11th to 20thNight
30%
720
14%
2177
8%
720
38%
720
18%
1574
October21st to endNight
26%
792
15%
2574
9%
792
35%
792
16%
1866
November1st to 10thNight
34%
740
20%
2406
16%
740
41%
740
22%
1579
November11th to 20thNight
25%
760
14%
2470
9%
760
32%
760
14%
1791
November21st to endNight
24%
760
14%
2470
8%
760
31%
760
14%
1832
December1st to 10thNight
16%
808
7%
2518
3%
808
19%
808
9%
2063
December11th to 20thNight
16%
949
7%
3256
2%
948
21%
948
9%
2614
December21st to endNight
13%
1041
4%
4865
1%
1026
19%
1026
4%
4149

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
14%10%47%6%45%5%5%7%34%
74853
Night
15%10%47%6%3445%7%33%
74863
TransparencyDay
49%6%12%20%11%1
74558
Night
50%6%12%19%11%1
74679
SeeingDay
18%11%28%24%14%6%
14584
Night
19%9%30%29%12%1
24553

By Month

Percentage Cloud Cover SE (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 10thDay
16%14%7%10%9%5%6%6%46%17%
1517
11th to 20thDay
15%16%8%11%10%46%5%5%6%14%
1440
21st to endDay
15%19%9%11%11%45%33416%
1632
February1st to 10thDay
14%15%6%11%10%6%5%5%46%19%
1638
11th to 20thDay
15%11%6%13%10%45%345%25%
1748
21st to endDay
15%15%6%11%7%36%5%45%24%
1480
March1st to 10thDay
13%11%6%8%7%45%5%6%7%29%
1800
11th to 20thDay
13%12%5%8%7%2345%7%33%
1961
21st to endDay
18%12%48%5%45%347%30%
2198
April1st to 10thDay
18%13%46%6%345%5%6%29%
2160
11th to 20thDay
17%10%36%5%45%447%35%
2222
21st to endDay
17%9%37%6%46%447%34%
2340
May1st to 10thDay
17%8%47%6%45%45%7%34%
2340
11th to 20thDay
18%7%36%5%24448%37%
2301
21st to endDay
12%7%35%5%45%5%6%8%40%
2641
June1st to 10thDay
11%5%25%5%35%6%6%8%44%
2520
11th to 20thDay
11%425%7%345%5%8%44%
2520
21st to endDay
9%5%26%6%45%6%8%9%40%
2520
July1st to 10thDay
7%4235%35%6%7%9%48%
2520
11th to 20thDay
9%5%25%5%346%7%9%45%
2520
21st to endDay
6%5%26%5%45%7%8%9%45%
2699
August1st to 10thDay
9%5%25%6%45%7%7%10%41%
2327
11th to 20thDay
10%5%26%6%46%5%6%9%41%
2303
21st to endDay
10%6%25%6%35%6%6%8%43%
2462
September1st to 10thDay
12%6%35%6%46%5%6%8%40%
2093
11th to 20thDay
11%5%25%435%46%8%47%
1980
21st to endDay
12%7%36%6%45%5%6%8%38%
1980
October1st to 10thDay
14%7%36%5%35%5%5%7%40%
1980
11th to 20thDay
18%9%48%7%345%6%6%30%
1778
21st to endDay
22%12%36%7%44447%26%
1782
November1st to 10thDay
12%11%35%6%345%46%40%
1672
11th to 20thDay
14%14%5%8%8%4445%7%26%
1710
21st to endDay
19%14%5%8%6%3445%5%28%
1710
December1st to 10thDay
13%16%9%12%8%45%445%19%
1658
11th to 20thDay
14%16%7%11%6%46%5%5%5%19%
1918
21st to endDay
22%22%8%12%6%4444411%
2783
January1st to 10thNight
17%13%6%11%10%45%446%20%
2648
11th to 20thNight
16%18%8%10%7%44445%19%
2533
21st to endNight
12%14%10%13%9%46%445%17%
2722
February1st to 10thNight
16%16%6%10%10%5%5%44419%
2318
11th to 20thNight
13%13%6%10%9%5%6%5%5%5%25%
2098
21st to endNight
18%12%5%9%6%35%45%7%27%
1776
March1st to 10thNight
15%9%5%7%6%3445%6%36%
2160
11th to 20thNight
12%10%47%5%25%5%47%39%
1998
21st to endNight
19%9%48%5%34446%34%
2174
April1st to 10thNight
15%10%46%6%345%46%36%
1800
11th to 20thNight
19%8%36%5%2445%7%37%
1687
21st to endNight
19%7%345%35%45%8%37%
1620
May1st to 10thNight
16%7%37%7%445%5%8%34%
1620
11th to 20thNight
19%8%25%43445%8%39%
1592
21st to endNight
10%5%25%445%5%7%10%41%
1630
June1st to 10thNight
12%425%435%5%6%9%47%
1440
11th to 20thNight
11%5%35%43446%9%46%
1440
21st to endNight
9%5%25%5%345%6%10%46%
1440
July1st to 10thNight
7%4134245%7%10%52%
1440
11th to 20thNight
8%5%244245%6%9%51%
1440
21st to endNight
5%435%5%25%5%7%9%52%
1619
August1st to 10thNight
6%5%245%345%6%10%49%
1611
11th to 20thNight
9%4247%345%8%7%48%
1598
21st to endNight
9%5%25%5%3446%7%50%
1892
September1st to 10thNight
10%5%26%6%345%5%8%47%
1849
11th to 20thNight
11%5%23424447%53%
1980
21st to endNight
13%6%35%5%35%447%44%
1980
October1st to 10thNight
16%6%35%43345%7%44%
1980
11th to 20thNight
19%10%46%6%4445%5%32%
2177
21st to endNight
22%10%37%6%35%45%6%30%
2574
November1st to 10thNight
14%10%37%5%24446%41%
2406
11th to 20thNight
14%13%5%8%6%45%5%5%7%27%
2470
21st to endNight
18%14%5%7%5%35%5%5%6%28%
2470
December1st to 10thNight
16%16%8%12%8%35%5%46%18%
2518
11th to 20thNight
14%16%7%14%8%45%445%20%
3279
21st to endNight
25%21%6%10%6%34445%12%
4884

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 10thDay
68%7%11%12%3
1518
11th to 20thDay
71%7%11%7%4
1440
21st to endDay
73%48%10%4
1632
February1st to 10thDay
66%7%10%12%5%
1638
11th to 20thDay
63%49%15%8%1
1758
21st to endDay
63%5%10%14%6%1
1480
March1st to 10thDay
54%6%13%18%8%1
1800
11th to 20thDay
50%5%12%18%13%2
1961
21st to endDay
56%5%10%18%10%1
2198
April1st to 10thDay
56%411%19%10%
2160
11th to 20thDay
49%5%11%19%14%2
2222
21st to endDay
49%6%11%17%14%2
2340
May1st to 10thDay
50%6%12%21%10%1
2340
11th to 20thDay
47%7%11%19%14%1
2305
21st to endDay
41%8%13%24%13%1
2641
June1st to 10thDay
37%7%13%26%16%2
2520
11th to 20thDay
37%7%13%22%19%2
2520
21st to endDay
38%9%13%22%16%2
2520
July1st to 10thDay
31%8%13%27%17%5%
2451
11th to 20thDay
34%7%13%25%18%2
2445
21st to endDay
32%8%14%25%18%3
2549
August1st to 10thDay
36%9%14%27%12%2
2314
11th to 20thDay
38%8%14%25%12%2
2303
21st to endDay
36%8%13%25%16%3
2462
September1st to 10thDay
41%7%13%23%15%2
2093
11th to 20thDay
35%6%12%31%15%1
1980
21st to endDay
42%6%13%23%15%
1980
October1st to 10thDay
42%7%10%25%14%2
1980
11th to 20thDay
54%6%12%19%9%
1778
21st to endDay
58%6%11%16%7%1
1782
November1st to 10thDay
44%7%13%21%14%1
1672
11th to 20thDay
58%6%11%17%7%1
1710
21st to endDay
59%5%14%16%6%1
1710
December1st to 10thDay
68%6%11%11%3
1658
11th to 20thDay
66%7%12%12%3
1915
21st to endDay
78%5%8%6%3
2783
January1st to 10thNight
65%6%10%14%5%
2648
11th to 20thNight
67%6%12%10%5%
2533
21st to endNight
69%5%10%10%5%1
2722
February1st to 10thNight
67%6%9%12%5%1
2318
11th to 20thNight
61%6%9%16%8%1
2099
21st to endNight
57%6%12%16%8%2
1776
March1st to 10thNight
50%5%12%22%10%1
2160
11th to 20thNight
44%6%11%22%15%2
1998
21st to endNight
51%5%9%22%10%2
2174
April1st to 10thNight
47%6%12%21%14%1
1800
11th to 20thNight
46%6%11%17%17%2
1687
21st to endNight
45%5%13%20%13%3
1620
May1st to 10thNight
49%7%11%20%11%2
1620
11th to 20thNight
44%6%9%19%19%3
1593
21st to endNight
37%8%14%25%14%2
1631
June1st to 10thNight
33%6%12%29%17%3
1440
11th to 20thNight
34%8%14%25%17%2
1440
21st to endNight
32%8%14%26%18%2
1440
July1st to 10thNight
26%8%14%29%19%5%
1400
11th to 20thNight
29%6%14%29%20%2
1392
21st to endNight
27%8%16%24%21%4
1529
August1st to 10thNight
29%8%15%30%16%2
1600
11th to 20thNight
31%8%13%29%16%2
1598
21st to endNight
32%6%12%25%22%3
1892
September1st to 10thNight
35%7%11%27%18%2
1849
11th to 20thNight
30%5%11%32%20%2
1980
21st to endNight
39%7%12%26%15%1
1980
October1st to 10thNight
41%5%10%25%17%1
1980
11th to 20thNight
53%6%11%19%11%1
2177
21st to endNight
55%5%10%20%9%1
2574
November1st to 10thNight
44%6%11%24%14%1
2406
11th to 20thNight
54%7%13%18%7%1
2470
21st to endNight
56%6%13%19%5%
2470
December1st to 10thNight
67%7%10%11%5%
2518
11th to 20thNight
66%5%12%11%5%
3281
21st to endNight
75%6%10%7%3
4884

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 10thDay
23%16%34%20%7%1
270
11th to 20thDay
20%13%43%17%5%1
240
21st to endDay
27%16%34%18%5%
264
February1st to 10thDay
26%20%34%18%2
240
11th to 20thDay
25%18%40%15%2
240
21st to endDay
26%27%33%12%2
198
March1st to 10thDay
21%20%43%13%4
240
11th to 20thDay
21%13%32%25%8%
401
21st to endDay
27%14%28%24%5%2
462
April1st to 10thDay
24%11%33%24%7%1
420
11th to 20thDay
25%17%28%17%8%5%
412
21st to endDay
20%14%32%20%12%2
420
May1st to 10thDay
24%13%26%24%9%3
423
11th to 20thDay
19%11%27%23%14%6%
447
21st to endDay
16%6%25%26%19%8%
595
June1st to 10thDay
12%7%27%32%16%5%
630
11th to 20thDay
14%5%28%31%17%6%
630
21st to endDay
12%7%28%31%16%6%
630
July1st to 10thDay
8%419%31%23%15%
621
11th to 20thDay
11%6%24%28%21%10%
618
21st to endDay
8%425%32%23%9%
640
August1st to 10thDay
9%418%28%21%21%
446
11th to 20thDay
13%414%28%29%11%
439
21st to endDay
12%422%25%25%13%
495
September1st to 10thDay
15%6%21%24%23%11%
450
11th to 20thDay
11%5%17%24%28%14%
450
21st to endDay
16%12%19%24%18%11%
450
October1st to 10thDay
19%8%28%22%16%8%
450
11th to 20thDay
21%18%26%26%8%1
419
21st to endDay
29%16%32%18%31
297
November1st to 10thDay
16%18%34%24%7%1
270
11th to 20thDay
24%20%34%17%5%
270
21st to endDay
29%16%38%12%6%
270
December1st to 10thDay
24%25%30%13%7%
270
11th to 20thDay
22%20%41%13%4
270
21st to endDay
25%22%35%14%3
297
January1st to 10thNight
21%14%35%22%6%1
950
11th to 20thNight
24%13%35%23%5%1
905
21st to endNight
19%11%36%29%5%
940
February1st to 10thNight
26%12%37%23%2
720
11th to 20thNight
21%14%36%25%3
703
21st to endNight
24%13%40%19%3
592
March1st to 10thNight
20%13%34%26%7%1
720
11th to 20thNight
18%12%36%27%6%1
720
21st to endNight
23%10%32%26%8%
788
April1st to 10thNight
17%12%39%25%6%1
540
11th to 20thNight
23%9%35%24%8%1
533
21st to endNight
22%6%34%29%8%1
540
May1st to 10thNight
21%6%32%32%9%1
540
11th to 20thNight
22%5%31%30%11%1
531
21st to endNight
12%327%35%21%2
584
June1st to 10thNight
13%324%45%15%1
540
11th to 20thNight
13%424%39%19%1
540
21st to endNight
10%420%42%22%1
540
July1st to 10thNight
8%216%41%28%5%
525
11th to 20thNight
11%217%42%25%3
522
21st to endNight
6%218%47%25%2
591
August1st to 10thNight
9%115%44%28%3
537
11th to 20thNight
9%117%38%30%5%
534
21st to endNight
11%319%37%28%4
594
September1st to 10thNight
11%318%38%25%4
589
11th to 20thNight
13%416%36%27%4
720
21st to endNight
17%6%22%27%23%5%
720
October1st to 10thNight
19%5%24%32%19%1
720
11th to 20thNight
23%12%29%27%8%1
720
21st to endNight
26%11%33%23%7%
792
November1st to 10thNight
20%10%30%30%9%1
740
11th to 20thNight
21%14%35%23%6%1
760
21st to endNight
24%12%34%26%4
760
December1st to 10thNight
24%15%34%21%6%
808
11th to 20thNight
23%14%36%23%4
950
21st to endNight
31%12%34%21%1
1045
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