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 2005-11-05 to 2018-03-21.

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
36%
16735
15%
49153
10%
16693
41%
16693
20%
34760

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
18%
975
8%
2716
4%
970
22%
970
10%
2218
January16th to endNight
20%
1004
7%
2876
3%
1004
24%
1004
11%
2380
February1st to 15thNight
18%
761
10%
2406
3%
761
24%
761
10%
1902
February16th to endNight
22%
683
13%
2049
6%
683
29%
683
14%
1555
March1st to 15thNight
30%
780
16%
2288
10%
780
35%
780
19%
1620
March16th to endNight
33%
789
19%
2175
10%
789
40%
789
22%
1522
April1st to 15thNight
26%
539
12%
1797
8%
539
32%
539
18%
1232
April16th to endNight
34%
540
19%
1620
9%
540
42%
540
24%
1066
May1st to 15thNight
35%
540
14%
1620
7%
540
42%
540
21%
1136
May16th to endNight
47%
562
15%
1606
11%
561
51%
561
29%
1023
June1st to 15thNight
54%
540
15%
1440
10%
540
58%
540
34%
908
June16th to endNight
57%
540
15%
1440
11%
540
60%
540
33%
915
July1st to 15thNight
66%
510
17%
1360
14%
510
68%
510
41%
812
July16th to endNight
68%
564
20%
1445
17%
531
70%
531
41%
848
August1st to 15thNight
66%
539
21%
1609
18%
536
69%
536
36%
933
August16th to endNight
61%
573
21%
1793
18%
573
65%
573
33%
1040
September1st to 15thNight
60%
633
26%
1893
22%
633
64%
633
35%
1098
September16th to endNight
58%
717
24%
1980
19%
717
61%
717
34%
1220
October1st to 15thNight
45%
720
19%
2034
15%
720
50%
720
25%
1373
October16th to endNight
28%
768
16%
2455
10%
768
37%
768
17%
1746
November1st to 15thNight
36%
760
18%
2471
16%
760
41%
760
20%
1668
November16th to endNight
27%
780
14%
2535
9%
780
33%
780
14%
1875
December1st to 15thNight
17%
878
6%
2633
2%
878
21%
878
10%
2150
December16th to endNight
14%
1040
7%
2912
2%
1040
19%
1040
7%
2520

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%8%47%6%35%45%7%33%
49703
Night
15%9%46%5%34446%34%
49325
Cloud CoverDay
13%9%47%6%3445%7%33%
49712
Night
14%9%46%6%34446%34%
49330
TransparencyDay
49%6%11%19%10%1
49393
Night
49%6%11%19%11%1
49153
SeeingDay
17%7%26%25%15%7%
6537
Night
19%7%29%29%12%1
16739

By Month

Percentage Cloud Cover NE (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
17%15%7%10%9%5%5%5%45%14%
1552
16th to endDay
14%18%8%11%9%45%345%15%
1698
February1st to 15thDay
14%14%6%11%9%45%335%20%
1783
16th to endDay
14%13%6%11%6%26%5%45%22%
1710
March1st to 15thDay
14%11%48%7%2446%6%29%
1992
16th to endDay
17%10%47%5%2335%7%32%
2189
April1st to 15thDay
19%12%35%5%34345%31%
2151
16th to endDay
16%7%35%5%35%446%38%
2340
May1st to 15thDay
19%6%37%6%34447%33%
2331
16th to endDay
13%6%35%435%45%7%39%
2506
June1st to 15thDay
10%425%5%45%5%6%7%42%
2520
16th to endDay
9%336%6%36%6%7%10%37%
2520
July1st to 15thDay
7%4245%35%5%6%10%45%
2520
16th to endDay
7%425%5%35%6%6%9%42%
2625
August1st to 15thDay
9%425%6%35%5%6%8%41%
2340
16th to endDay
11%5%35%5%35%5%6%8%39%
2408
September1st to 15thDay
12%5%245%4445%7%43%
2055
16th to endDay
11%5%25%6%35%46%8%41%
1980
October1st to 15thDay
15%6%26%5%34446%38%
1926
16th to endDay
22%9%45%5%34446%29%
1767
November1st to 15thDay
15%10%25%6%33446%38%
1717
16th to endDay
16%15%47%6%34436%26%
1755
December1st to 15thDay
15%14%9%12%6%34445%19%
1654
16th to endDay
19%18%8%10%7%4434414%
1664
January1st to 15thNight
20%13%6%10%7%3444420%
2716
16th to endNight
12%13%9%12%7%5%5%45%6%17%
2876
February1st to 15thNight
14%15%6%9%7%35%5%4423%
2404
16th to endNight
15%11%5%8%7%35%447%25%
2049
March1st to 15thNight
15%10%46%6%24437%35%
2275
16th to endNight
14%7%46%4345%47%36%
2175
April1st to 15thNight
19%7%45%6%24446%34%
1797
16th to endNight
17%7%24434446%39%
1620
May1st to 15thNight
19%5%25%5%245%47%34%
1620
16th to endNight
12%6%25%43345%9%43%
1604
June1st to 15thNight
12%4245%3336%7%47%
1440
16th to endNight
8%415%425%5%6%11%43%
1440
July1st to 15thNight
7%3144245%5%10%51%
1440
16th to endNight
6%32332446%9%52%
1543
August1st to 15thNight
6%3145%345%6%8%50%
1620
16th to endNight
10%5%25%423447%50%
1793
September1st to 15thNight
11%413324346%52%
1893
16th to endNight
10%425%424447%48%
1980
October1st to 15thNight
18%6%25%433446%40%
2034
16th to endNight
21%8%26%5%34345%33%
2455
November1st to 15thNight
16%9%36%5%24445%37%
2471
16th to endNight
18%14%46%434446%28%
2535
December1st to 15thNight
18%16%6%9%7%34445%19%
2633
16th to endNight
21%15%8%11%7%35%435%14%
2912

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 15thDay
17%15%7%9%9%45%5%45%14%
1552
16th to endDay
14%17%8%10%9%35%345%15%
1698
February1st to 15thDay
14%14%6%11%9%5%5%335%20%
1783
16th to endDay
14%13%6%11%6%35%5%45%22%
1710
March1st to 15thDay
14%10%5%8%6%3445%7%28%
2002
16th to endDay
17%10%47%5%3335%7%31%
2188
April1st to 15thDay
19%12%36%5%34436%30%
2151
16th to endDay
16%7%26%5%35%447%37%
2340
May1st to 15thDay
18%7%36%5%34447%33%
2331
16th to endDay
12%6%35%5%35%45%7%39%
2506
June1st to 15thDay
10%5%25%6%35%5%5%7%42%
2520
16th to endDay
9%426%6%35%7%7%9%37%
2520
July1st to 15thDay
7%4145%346%6%9%45%
2520
16th to endDay
7%5%25%435%6%7%9%42%
2625
August1st to 15thDay
8%5%25%6%45%5%6%9%40%
2340
16th to endDay
11%5%25%5%345%6%8%39%
2408
September1st to 15thDay
11%5%245%35%46%7%42%
2055
16th to endDay
11%5%25%5%25%46%8%41%
1980
October1st to 15thDay
15%7%36%5%24446%38%
1926
16th to endDay
21%10%35%6%34436%29%
1767
November1st to 15thDay
15%10%35%6%33436%37%
1717
16th to endDay
16%15%5%7%6%34446%27%
1755
December1st to 15thDay
15%13%9%12%7%34435%19%
1654
16th to endDay
19%18%8%11%5%4434415%
1664
January1st to 15thNight
19%13%6%9%8%3434420%
2716
16th to endNight
11%13%9%11%8%45%45%6%18%
2876
February1st to 15thNight
14%15%5%9%8%45%44423%
2397
16th to endNight
15%10%6%8%7%35%45%6%25%
2049
March1st to 15thNight
15%9%46%5%24346%35%
2288
16th to endNight
14%8%36%425%5%48%35%
2175
April1st to 15thNight
19%7%45%5%345%46%34%
1797
16th to endNight
17%7%3443435%6%39%
1620
May1st to 15thNight
19%6%25%6%3445%7%34%
1619
16th to endNight
11%6%25%42445%9%43%
1604
June1st to 15thNight
12%42443335%7%47%
1440
16th to endNight
8%3245%245%7%10%43%
1440
July1st to 15thNight
7%41342346%9%51%
1440
16th to endNight
6%32342446%9%53%
1543
August1st to 15thNight
5%4245%3447%8%49%
1620
16th to endNight
9%4245%2335%7%50%
1793
September1st to 15thNight
11%413423347%52%
1893
16th to endNight
10%425%424448%48%
1980
October1st to 15thNight
17%6%35%43345%6%40%
2034
16th to endNight
21%9%36%5%34346%32%
2455
November1st to 15thNight
15%10%36%424445%37%
2471
16th to endNight
18%13%46%5%34445%28%
2535
December1st to 15thNight
18%15%7%9%7%34435%19%
2633
16th to endNight
20%16%7%11%7%3444414%
2912

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
71%6%9%9%2
1553
16th to endDay
72%5%10%9%3
1698
February1st to 15thDay
68%48%13%4
1785
16th to endDay
63%5%9%14%5%
1710
March1st to 15thDay
54%6%13%16%8%
2002
16th to endDay
51%411%21%8%1
2189
April1st to 15thDay
55%49%19%11%
2151
16th to endDay
45%6%12%17%14%3
2340
May1st to 15thDay
50%6%11%20%9%1
2331
16th to endDay
43%6%12%25%11%1
2510
June1st to 15thDay
38%7%12%24%15%1
2520
16th to endDay
40%8%13%20%16%1
2520
July1st to 15thDay
33%7%12%24%19%3
2371
16th to endDay
35%7%14%24%15%2
2460
August1st to 15thDay
38%7%13%25%12%2
2327
16th to endDay
39%7%11%24%14%2
2408
September1st to 15thDay
38%6%11%26%16%1
2055
16th to endDay
39%5%12%27%15%
1980
October1st to 15thDay
46%5%10%23%12%1
1926
16th to endDay
55%6%11%18%7%
1767
November1st to 15thDay
47%5%11%21%11%1
1717
16th to endDay
59%5%13%16%5%
1755
December1st to 15thDay
66%5%11%11%3
1654
16th to endDay
73%49%8%2
1664
January1st to 15thNight
66%5%10%11%5%
2716
16th to endNight
66%6%13%9%3
2876
February1st to 15thNight
63%5%9%14%5%
2406
16th to endNight
57%6%11%16%6%1
2049
March1st to 15thNight
50%5%11%19%11%1
2288
16th to endNight
46%6%11%23%11%1
2175
April1st to 15thNight
49%5%11%18%14%
1797
16th to endNight
44%5%12%18%15%3
1620
May1st to 15thNight
47%6%10%20%11%2
1620
16th to endNight
38%6%13%23%15%2
1606
June1st to 15thNight
34%6%13%28%16%1
1440
16th to endNight
33%9%16%23%16%1
1440
July1st to 15thNight
28%6%12%29%20%2
1360
16th to endNight
26%7%15%25%21%2
1445
August1st to 15thNight
29%7%13%29%17%2
1609
16th to endNight
33%5%11%27%19%3
1793
September1st to 15thNight
31%5%10%29%21%1
1893
16th to endNight
34%5%12%28%18%
1980
October1st to 15thNight
44%5%10%22%16%1
2034
16th to endNight
52%410%22%8%
2455
November1st to 15thNight
47%5%11%21%11%1
2471
16th to endNight
56%6%12%19%5%
2535
December1st to 15thNight
66%5%11%10%5%
2633
16th to endNight
72%6%9%8%2
2912

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
16%11%45%19%6%
135
16th to endDay
28%9%43%15%2
144
February1st to 15thDay
26%15%45%11%
135
16th to endDay
23%17%36%17%5%
120
March1st to 15thDay
24%11%36%20%6%
187
16th to endDay
24%5%27%28%11%2
311
April1st to 15thDay
24%8%30%27%7%2
270
16th to endDay
20%8%31%20%13%5%
270
May1st to 15thDay
23%9%26%23%11%5%
288
16th to endDay
17%7%27%24%15%6%
406
June1st to 15thDay
14%428%31%14%6%
495
16th to endDay
12%6%30%29%13%6%
495
July1st to 15thDay
8%422%30%23%10%
475
16th to endDay
9%223%30%23%10%
485
August1st to 15thDay
10%115%27%22%22%
313
16th to endDay
14%317%20%28%16%
332
September1st to 15thDay
12%316%23%26%17%
315
16th to endDay
13%414%24%27%14%
314
October1st to 15thDay
19%7%20%30%17%4
315
16th to endDay
23%10%31%27%6%
183
November1st to 15thDay
17%11%29%29%9%2
135
16th to endDay
28%15%37%11%6%
135
December1st to 15thDay
24%22%34%12%5%
135
16th to endDay
26%28%33%9%1
144
January1st to 15thNight
26%12%34%20%5%1
975
16th to endNight
17%11%35%30%5%
1004
February1st to 15thNight
22%11%38%22%3
764
16th to endNight
21%11%36%25%4
683
March1st to 15thNight
21%11%32%27%7%
780
16th to endNight
16%9%34%28%9%1
789
April1st to 15thNight
21%9%35%25%6%
539
16th to endNight
21%6%35%25%10%1
540
May1st to 15thNight
22%431%31%8%1
540
16th to endNight
13%329%34%17%1
563
June1st to 15thNight
13%223%43%15%
540
16th to endNight
10%222%41%21%1
540
July1st to 15thNight
10%115%44%25%3
510
16th to endNight
7%116%43%28%2
564
August1st to 15thNight
7%15%45%26%4
539
16th to endNight
11%118%35%28%5%
573
September1st to 15thNight
14%216%34%27%4
633
16th to endNight
13%417%29%29%5%
717
October1st to 15thNight
21%423%31%17%2
720
16th to endNight
24%10%32%24%8%
768
November1st to 15thNight
21%8%27%31%9%
760
16th to endNight
23%12%31%25%6%
780
December1st to 15thNight
27%11%34%22%4
878
16th to endNight
29%10%35%21%2
1040
Page generated at 2018-03-22 11:34:20. Version ac04

Copyright 2018 A. Danko


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