Stephen C. Foster State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stephen C. Foster State Park clear sky chart from 2005-11-05 to 2018-02-14.

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
51%
16376
22%
48781
15%
16337
59%
16337
29%
30234

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
33%
776
21%
2522
10%
776
47%
776
23%
1551
January16th to endNight
34%
832
24%
2675
15%
832
47%
832
24%
1639
February1st to 15thNight
35%
759
22%
2276
11%
756
47%
756
26%
1419
February16th to endNight
35%
631
26%
1882
13%
631
47%
631
29%
1135
March1st to 15thNight
38%
720
27%
1980
13%
720
50%
720
34%
1182
March16th to endNight
42%
768
25%
2112
12%
768
51%
768
35%
1235
April1st to 15thNight
41%
718
24%
1976
13%
718
49%
718
34%
1185
April16th to endNight
52%
642
30%
1764
19%
642
59%
642
41%
987
May1st to 15thNight
55%
539
26%
1619
16%
539
62%
539
37%
906
May16th to endNight
72%
561
22%
1682
17%
561
74%
561
36%
988
June1st to 15thNight
66%
540
14%
1620
10%
540
68%
540
25%
1076
June16th to endNight
72%
540
13%
1620
11%
540
73%
540
25%
1091
July1st to 15thNight
74%
510
11%
1530
10%
510
75%
510
29%
1002
July16th to endNight
71%
564
10%
1595
10%
531
72%
531
24%
1107
August1st to 15thNight
72%
539
11%
1609
10%
536
73%
536
23%
1124
August16th to endNight
64%
660
12%
1973
13%
660
64%
660
20%
1413
September1st to 15thNight
61%
720
12%
1980
12%
720
61%
720
22%
1403
September16th to endNight
58%
717
17%
1980
15%
717
60%
717
24%
1367
October1st to 15thNight
58%
720
28%
2037
24%
720
63%
720
34%
1230
October16th to endNight
55%
768
33%
2304
27%
768
65%
768
35%
1298
November1st to 15thNight
51%
760
30%
2281
23%
760
61%
760
38%
1262
November16th to endNight
43%
780
29%
2525
20%
780
57%
780
33%
1413
December1st to 15thNight
42%
780
24%
2535
16%
780
53%
780
27%
1532
December16th to endNight
44%
832
22%
2704
17%
832
53%
832
24%
1689

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
10%5%26%6%35%5%5%7%38%
49281
Night
9%5%245%3446%8%45%
48985
TransparencyDay
42%6%12%17%14%6%
48982
Night
35%6%13%19%15%8%
48788
SeeingDay
13%5%18%23%24%14%
6149
Night
12%6%21%32%23%4
16384

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 15thDay
13%6%25%32445%7%42%
1746
16th to endDay
14%6%34323346%46%
1898
February1st to 15thDay
15%6%345%23446%43%
1883
16th to endDay
14%6%245%2223450%
1589
March1st to 15thDay
9%414424446%51%
1980
16th to endDay
11%5%25%424447%46%
2111
April1st to 15thDay
10%425%435%446%47%
1972
16th to endDay
8%4146%36%5%5%7%46%
2205
May1st to 15thDay
7%3246%45%5%6%8%46%
2331
16th to endDay
8%5%26%6%46%6%6%8%37%
2431
June1st to 15thDay
11%437%7%47%7%7%9%29%
2340
16th to endDay
8%5%37%10%48%6%8%9%26%
2340
July1st to 15thDay
7%6%38%9%5%8%7%7%9%25%
2340
16th to endDay
8%6%49%9%6%9%7%7%9%23%
2465
August1st to 15thDay
10%6%49%9%5%8%9%7%9%18%
2340
16th to endDay
13%7%38%8%47%6%7%9%21%
2210
September1st to 15thDay
13%6%37%8%5%7%6%7%9%25%
1980
16th to endDay
15%6%37%6%46%6%5%6%29%
1980
October1st to 15thDay
12%6%26%5%24447%42%
1923
16th to endDay
9%32442445%5%53%
1920
November1st to 15thDay
8%5%14323346%55%
1907
16th to endDay
10%5%24424335%53%
1763
December1st to 15thDay
13%6%35%5%34346%42%
1755
16th to endDay
12%6%35%6%34446%40%
1872
January1st to 15thNight
12%5%3443445%6%44%
2522
16th to endNight
13%6%25%5%14445%46%
2675
February1st to 15thNight
14%5%25%5%23346%46%
2271
16th to endNight
13%5%24424346%48%
1882
March1st to 15thNight
8%5%15%41435%9%50%
1980
16th to endNight
9%423423336%56%
2112
April1st to 15thNight
9%5%2432345%6%52%
1976
16th to endNight
7%31432335%7%56%
1764
May1st to 15thNight
6%314425%448%53%
1619
16th to endNight
6%314425%6%7%10%47%
1682
June1st to 15thNight
9%325%7%45%6%9%10%34%
1620
16th to endNight
7%3246%46%6%7%13%35%
1620
July1st to 15thNight
5%5%15%6%36%8%10%13%34%
1620
16th to endNight
4435%8%37%7%9%12%32%
1703
August1st to 15thNight
5%435%7%47%8%9%12%31%
1620
16th to endNight
9%6%26%6%46%7%8%11%30%
1973
September1st to 15thNight
10%5%26%7%35%5%8%11%32%
1980
16th to endNight
11%7%26%5%345%7%8%35%
1980
October1st to 15thNight
9%5%24424347%50%
2037
16th to endNight
7%3145%23445%56%
2304
November1st to 15thNight
8%41342435%7%54%
2281
16th to endNight
9%5%24323436%53%
2525
December1st to 15thNight
13%5%3432445%7%45%
2535
16th to endNight
13%6%25%5%2446%6%43%
2704

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
40%310%16%18%10%
1747
16th to endDay
38%26%19%22%10%
1898
February1st to 15thDay
42%37%12%19%13%
1885
16th to endDay
39%26%15%22%13%
1589
March1st to 15thDay
33%38%21%23%9%
1980
16th to endDay
36%411%16%20%10%
2112
April1st to 15thDay
36%5%8%17%22%10%
1972
16th to endDay
35%5%8%20%19%10%
2205
May1st to 15thDay
34%5%10%21%19%8%
2331
16th to endDay
40%6%12%21%14%4
2435
June1st to 15thDay
47%8%16%18%8%
2340
16th to endDay
48%11%17%15%6%
2340
July1st to 15thDay
49%10%23%14%2
2201
16th to endDay
53%9%19%13%3
2310
August1st to 15thDay
55%11%19%11%2
2327
16th to endDay
56%10%16%12%2
2210
September1st to 15thDay
52%10%15%12%7%2
1980
16th to endDay
52%8%11%14%10%3
1980
October1st to 15thDay
41%48%18%17%10%
1923
16th to endDay
31%45%17%23%16%
1920
November1st to 15thDay
30%36%23%24%11%
1907
16th to endDay
34%38%17%24%12%
1763
December1st to 15thDay
42%49%18%15%9%
1755
16th to endDay
44%311%20%12%7%
1872
January1st to 15thNight
39%48%17%19%10%
2522
16th to endNight
39%37%13%22%12%
2675
February1st to 15thNight
39%37%15%19%14%
2280
16th to endNight
36%38%17%19%13%
1882
March1st to 15thNight
32%412%21%19%10%
1980
16th to endNight
31%311%20%21%11%
2112
April1st to 15thNight
31%5%10%18%22%10%
1976
16th to endNight
27%412%24%21%10%
1764
May1st to 15thNight
28%6%14%25%17%9%
1620
16th to endNight
28%8%15%27%14%4
1684
June1st to 15thNight
38%11%19%20%9%
1620
16th to endNight
37%12%21%20%6%1
1620
July1st to 15thNight
34%12%29%20%3
1530
16th to endNight
37%14%25%18%3
1595
August1st to 15thNight
37%15%27%15%3
1609
16th to endNight
42%13%22%16%3
1973
September1st to 15thNight
42%12%21%14%7%1
1980
16th to endNight
44%7%15%20%8%3
1980
October1st to 15thNight
34%410%20%18%10%
2037
16th to endNight
30%46%18%23%16%
2304
November1st to 15thNight
29%37%22%24%11%
2281
16th to endNight
32%38%18%22%13%
2525
December1st to 15thNight
38%412%21%15%7%
2535
16th to endNight
40%411%21%12%8%
2704

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%14%41%9%7%4
135
16th to endDay
18%20%31%20%8%
144
February1st to 15thDay
23%16%36%17%5%
130
16th to endDay
10%16%43%26%3
90
March1st to 15thDay
14%12%29%29%13%
270
16th to endDay
14%7%30%24%17%4
288
April1st to 15thDay
17%10%23%24%20%3
270
16th to endDay
8%5%21%27%24%12%
270
May1st to 15thDay
7%5%29%24%21%11%
288
16th to endDay
8%310%26%32%18%
331
June1st to 15thDay
13%47%20%30%24%
315
16th to endDay
11%1418%37%26%
315
July1st to 15thDay
5%1218%34%37%
305
16th to endDay
11%3318%37%26%
326
August1st to 15thDay
16%26%17%32%24%
313
16th to endDay
13%16%16%35%26%
332
September1st to 15thDay
16%38%22%29%19%
315
16th to endDay
18%18%24%31%15%
314
October1st to 15thDay
14%420%28%23%8%
315
16th to endDay
11%5%24%29%23%5%
336
November1st to 15thDay
13%425%32%16%7%
325
16th to endDay
9%11%32%29%11%4
143
December1st to 15thDay
17%10%37%22%11%1
135
16th to endDay
19%6%31%31%9%2
144
January1st to 15thNight
15%12%32%27%9%1
780
16th to endNight
16%12%32%31%7%
832
February1st to 15thNight
17%13%29%31%8%
760
16th to endNight
16%12%31%34%4
631
March1st to 15thNight
11%12%33%31%10%
720
16th to endNight
12%8%32%30%15%
768
April1st to 15thNight
11%10%32%33%12%
718
16th to endNight
9%6%26%40%16%
642
May1st to 15thNight
5%427%42%18%1
540
16th to endNight
7%210%41%33%4
563
June1st to 15thNight
10%27%38%35%6%
540
16th to endNight
8%6%32%41%11%
540
July1st to 15thNight
7%328%42%16%
510
16th to endNight
5%1429%45%14%
564
August1st to 15thNight
6%1326%48%14%
539
16th to endNight
12%35%24%39%14%
660
September1st to 15thNight
12%17%28%39%10%
720
16th to endNight
16%210%31%33%4
717
October1st to 15thNight
13%120%34%27%3
720
16th to endNight
8%6%24%35%24%1
768
November1st to 15thNight
10%5%26%37%19%1
760
16th to endNight
13%7%30%30%17%1
780
December1st to 15thNight
16%9%26%31%15%1
780
16th to endNight
16%9%23%32%17%
832
Page generated at 2018-02-15 10:58:41. Version ac04

Copyright 2018 A. Danko


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