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 2017-08-12.

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%
15641
22%
46544
15%
15602
58%
15602
29%
28890

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
34%
716
21%
2327
11%
716
47%
716
23%
1423
January16th to endNight
33%
768
23%
2469
14%
768
46%
768
24%
1519
February1st to 15thNight
35%
703
24%
2108
12%
700
48%
700
27%
1294
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%
527
11%
1575
10%
524
72%
524
22%
1106
August16th to endNight
64%
605
12%
1808
12%
605
64%
605
20%
1305
September1st to 15thNight
62%
660
13%
1815
13%
660
62%
660
22%
1286
September16th to endNight
55%
657
16%
1815
13%
657
58%
657
23%
1271
October1st to 15thNight
58%
660
29%
1867
25%
660
64%
660
35%
1122
October16th to endNight
55%
704
31%
2112
26%
704
64%
704
34%
1204
November1st to 15thNight
51%
700
31%
2101
24%
700
61%
700
37%
1173
November16th to endNight
43%
720
28%
2331
19%
720
56%
720
32%
1308
December1st to 15thNight
42%
720
24%
2340
17%
720
52%
720
26%
1426
December16th to endNight
44%
768
22%
2496
17%
768
53%
768
24%
1559

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%36%6%35%5%5%7%38%
47416
Night
9%5%25%5%3446%8%45%
46748
TransparencyDay
42%6%11%17%14%7%
47117
Night
35%6%13%19%15%8%
46551
SeeingDay
13%5%17%22%25%14%
5494
Night
12%6%21%32%22%4
15649

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
12%7%25%32445%7%42%
1611
16th to endDay
14%6%34333346%45%
1752
February1st to 15thDay
15%6%345%23446%44%
1750
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
11%6%48%9%5%8%9%7%9%18%
2288
16th to endDay
14%7%49%8%47%6%6%9%21%
2025
September1st to 15thDay
12%6%38%8%5%6%6%7%9%25%
1815
16th to endDay
17%7%37%6%46%6%5%6%26%
1815
October1st to 15thDay
12%6%26%5%23447%44%
1763
16th to endDay
9%42443445%5%52%
1760
November1st to 15thDay
8%5%1432335%6%54%
1757
16th to endDay
10%5%24423335%52%
1628
December1st to 15thDay
13%6%35%5%44446%42%
1620
16th to endDay
12%6%35%6%3445%6%40%
1728
January1st to 15thNight
11%5%3443445%6%44%
2327
16th to endNight
13%6%25%414445%46%
2469
February1st to 15thNight
14%4245%23345%48%
2103
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%30%
1586
16th to endNight
9%6%26%6%46%7%8%11%30%
1808
September1st to 15thNight
9%5%27%7%35%5%8%11%32%
1815
16th to endNight
12%8%26%6%345%6%8%33%
1815
October1st to 15thNight
10%5%24423347%50%
1867
16th to endNight
7%3145%23446%54%
2112
November1st to 15thNight
9%423424348%53%
2101
16th to endNight
9%5%24323436%52%
2331
December1st to 15thNight
13%6%3432435%7%44%
2340
16th to endNight
13%6%25%5%2445%6%43%
2496

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%
1612
16th to endDay
39%36%19%20%10%
1752
February1st to 15thDay
41%37%13%20%14%
1752
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%18%11%2
2275
16th to endDay
56%10%16%12%21
2025
September1st to 15thDay
52%10%14%12%7%2
1815
16th to endDay
54%8%10%13%10%3
1815
October1st to 15thDay
40%37%19%17%11%
1763
16th to endDay
32%45%18%23%15%
1760
November1st to 15thDay
30%26%21%25%12%
1757
16th to endDay
35%38%17%22%13%
1628
December1st to 15thDay
42%49%19%16%8%
1620
16th to endDay
44%311%19%12%8%
1728
January1st to 15thNight
39%49%17%18%10%
2327
16th to endNight
39%47%13%22%12%
2469
February1st to 15thNight
38%36%15%20%15%
2112
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
38%15%26%15%3
1575
16th to endNight
43%13%21%16%4
1808
September1st to 15thNight
41%12%21%14%7%1
1815
16th to endNight
46%7%14%19%9%3
1815
October1st to 15thNight
34%410%20%18%11%
1867
16th to endNight
30%5%6%18%22%16%
2112
November1st to 15thNight
30%37%21%23%12%
2101
16th to endNight
32%39%18%20%14%
2331
December1st to 15thNight
39%411%21%16%7%
2340
16th to endNight
40%410%21%12%9%
2496

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%13%36%10%11%6%
90
16th to endDay
20%17%33%19%8%
96
February1st to 15thDay
24%16%36%15%6%
90
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
17%26%17%31%24%
297
16th to endDay
13%15%17%37%24%
268
September1st to 15thDay
15%35%20%32%22%
255
16th to endDay
22%19%22%28%15%
254
October1st to 15thDay
16%5%17%30%24%5%
255
16th to endDay
11%5%22%28%25%6%
272
November1st to 15thDay
15%428%28%15%8%
265
16th to endDay
10%11%39%24%9%5%
98
December1st to 15thDay
12%11%42%20%12%2
90
16th to endDay
19%6%28%30%12%3
96
January1st to 15thNight
15%12%32%28%10%1
720
16th to endNight
16%12%32%30%7%
768
February1st to 15thNight
17%13%29%30%8%
704
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%13%
527
16th to endNight
12%25%25%39%13%
605
September1st to 15thNight
11%26%28%40%10%
660
16th to endNight
17%311%32%30%4
657
October1st to 15thNight
13%119%35%27%3
660
16th to endNight
8%6%22%35%25%1
704
November1st to 15thNight
10%5%26%37%19%1
700
16th to endNight
13%7%31%30%16%1
720
December1st to 15thNight
15%10%26%31%15%1
720
16th to endNight
16%10%23%32%17%
768
Page generated at 2017-08-13 14:16:46. Version ac04

Copyright 2017 A. Danko


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