Lake Somerville State Park - Birch Creek Unit
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Somerville State Park - Birch Creek Unit clear sky chart from 2005-11-05 to 2017-09-22.

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
52%
15432
25%
46976
18%
15386
59%
15386
34%
27223

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
36%
896
25%
2327
11%
895
44%
895
30%
1510
January16th to endNight
35%
960
28%
2496
11%
960
45%
960
32%
1583
February1st to 15thNight
36%
717
26%
2118
12%
710
46%
710
28%
1301
February16th to endNight
27%
584
27%
1846
9%
584
41%
584
26%
1104
March1st to 15thNight
31%
540
26%
1980
14%
540
46%
540
23%
1189
March16th to endNight
36%
576
24%
2112
16%
576
48%
576
27%
1170
April1st to 15thNight
31%
539
22%
1977
12%
539
47%
539
26%
1121
April16th to endNight
35%
540
24%
1803
16%
540
49%
540
29%
1047
May1st to 15thNight
35%
539
22%
1619
15%
539
45%
539
31%
979
May16th to endNight
55%
563
27%
1685
23%
561
66%
561
39%
944
June1st to 15thNight
75%
540
22%
1620
25%
540
78%
540
49%
813
June16th to endNight
77%
540
20%
1620
23%
540
81%
540
39%
929
July1st to 15thNight
79%
510
21%
1530
25%
510
81%
510
43%
822
July16th to endNight
83%
564
21%
1594
25%
531
84%
531
44%
864
August1st to 15thNight
89%
539
29%
1610
33%
536
89%
536
57%
751
August16th to endNight
78%
573
19%
1965
23%
573
79%
573
30%
1146
September1st to 15thNight
79%
540
19%
1980
22%
540
80%
540
32%
1089
September16th to endNight
70%
513
27%
1891
29%
513
72%
513
31%
1037
October1st to 15thNight
71%
561
34%
1881
32%
561
73%
561
43%
931
October16th to endNight
60%
704
35%
2112
24%
704
66%
704
46%
1079
November1st to 15thNight
52%
700
28%
2100
19%
700
58%
700
33%
1234
November16th to endNight
47%
834
30%
2274
17%
834
55%
834
37%
1328
December1st to 15thNight
39%
900
26%
2340
14%
900
45%
900
28%
1576
December16th to endNight
38%
960
22%
2496
10%
960
44%
960
27%
1676

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
11%5%25%5%3445%7%43%
47893
Night
10%424324447%51%
47179
TransparencyDay
38%5%11%19%17%7%
47593
Night
32%5%12%21%18%10%
46984
SeeingDay
10%415%27%30%11%
5421
Night
12%6%24%35%20%1
15437

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
18%6%3342334445%
1611
16th to endDay
17%5%24412245%49%
1728
February1st to 15thDay
16%7%3432223448%
1747
16th to endDay
15%8%26%433335%43%
1628
March1st to 15thDay
21%8%25%324345%39%
1980
16th to endDay
14%7%35%423335%46%
2110
April1st to 15thDay
12%5%36%5%34448%40%
1971
16th to endDay
12%5%36%5%3445%6%42%
2154
May1st to 15thDay
10%6%36%6%35%5%6%7%37%
2331
16th to endDay
11%5%35%6%445%7%8%37%
2430
June1st to 15thDay
33246%47%7%8%9%43%
2340
16th to endDay
6%5%35%6%48%7%8%10%33%
2340
July1st to 15thDay
6%325%7%47%6%8%11%35%
2340
16th to endDay
5%326%7%46%6%7%12%37%
2466
August1st to 15thDay
32143246%5%10%54%
2340
16th to endDay
6%425%6%46%6%8%10%37%
2231
September1st to 15thDay
7%426%6%36%5%5%9%40%
1980
16th to endDay
7%4245%45%6%5%7%44%
1881
October1st to 15thDay
8%42342445%7%51%
1736
16th to endDay
9%31321233463%
1760
November1st to 15thDay
9%6%25%4235%5%7%48%
1758
16th to endDay
14%6%13333335%52%
1683
December1st to 15thDay
19%8%25%5%23335%40%
1620
16th to endDay
17%7%35%5%34345%39%
1728
January1st to 15thNight
16%6%24413335%47%
2327
16th to endNight
17%5%23313336%48%
2496
February1st to 15thNight
13%7%34312235%51%
2115
16th to endNight
13%5%24323335%50%
1846
March1st to 15thNight
17%6%24313336%45%
1980
16th to endNight
10%5%24424446%51%
2112
April1st to 15thNight
8%424425%45%7%47%
1977
16th to endNight
11%5%24423346%49%
1803
May1st to 15thNight
7%326%43446%10%44%
1619
16th to endNight
3313326%5%6%10%51%
1683
June1st to 15thNight
21123235%5%10%61%
1620
16th to endNight
3214325%6%8%10%51%
1620
July1st to 15thNight
5%2123145%6%10%55%
1620
16th to endNight
321332446%13%54%
1702
August1st to 15thNight
21222335%12%62%
1620
16th to endNight
5%314436%5%7%11%45%
1965
September1st to 15thNight
7%314425%5%5%10%50%
1980
16th to endNight
8%31343346%8%50%
1891
October1st to 15thNight
6%313323346%61%
1881
16th to endNight
8%31221233465%
2112
November1st to 15thNight
9%5%24423346%52%
2100
16th to endNight
11%5%23323235%55%
2274
December1st to 15thNight
16%7%34423346%43%
2340
16th to endNight
16%7%24423345%44%
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
41%46%16%19%11%
1612
16th to endDay
39%25%15%22%14%
1728
February1st to 15thDay
39%36%16%20%14%
1748
16th to endDay
44%26%15%19%11%
1628
March1st to 15thDay
48%36%11%21%9%
1980
16th to endDay
41%36%16%24%6%
2112
April1st to 15thDay
42%5%6%18%15%11%
1971
16th to endDay
42%47%18%18%8%
2154
May1st to 15thDay
44%5%10%16%14%8%
2331
16th to endDay
41%6%12%20%15%3
2434
June1st to 15thDay
33%7%12%24%19%3
2340
16th to endDay
41%10%13%21%11%1
2340
July1st to 15thDay
37%8%17%24%10%
2201
16th to endDay
34%9%22%25%7%
2311
August1st to 15thDay
25%8%18%32%13%1
2326
16th to endDay
39%8%18%21%8%1
2231
September1st to 15thDay
39%8%13%19%14%4
1980
16th to endDay
37%6%10%19%17%8%
1881
October1st to 15thDay
32%49%19%17%16%
1736
16th to endDay
25%3417%29%19%
1760
November1st to 15thDay
34%410%20%18%10%
1758
16th to endDay
34%38%13%22%18%
1683
December1st to 15thDay
47%28%15%16%8%
1620
16th to endDay
46%39%14%17%8%
1728
January1st to 15thNight
40%25%16%20%14%
2327
16th to endNight
37%3415%22%15%
2496
February1st to 15thNight
38%35%13%20%17%
2125
16th to endNight
37%45%17%19%15%
1846
March1st to 15thNight
40%48%14%20%12%
1980
16th to endNight
33%5%11%17%21%9%
2112
April1st to 15thNight
34%5%10%17%18%13%
1977
16th to endNight
36%311%21%16%10%
1803
May1st to 15thNight
34%6%12%22%15%8%
1620
16th to endNight
26%6%16%29%16%3
1685
June1st to 15thNight
19%6%16%30%24%3
1620
16th to endNight
25%9%20%29%13%2
1620
July1st to 15thNight
22%7%23%34%11%
1530
16th to endNight
20%9%30%30%8%
1594
August1st to 15thNight
14%5%26%36%15%1
1610
16th to endNight
29%10%23%26%7%1
1965
September1st to 15thNight
29%7%20%24%12%6%
1980
16th to endNight
30%7%14%20%17%10%
1891
October1st to 15thNight
24%311%25%19%15%
1881
16th to endNight
24%25%17%28%22%
2112
November1st to 15thNight
34%49%21%20%10%
2100
16th to endNight
31%47%14%22%20%
2274
December1st to 15thNight
43%47%19%17%9%
2340
16th to endNight
43%45%16%19%11%
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
18%433%32%10%1
90
16th to endDay
16%15%41%15%8%2
96
February1st to 15thDay
14%15%34%22%13%
90
16th to endDay
18%12%40%16%11%1
81
March1st to 15thDay
26%14%35%12%11%
90
16th to endDay
11%9%28%35%13%2
96
April1st to 15thDay
10%12%34%26%14%2
90
16th to endDay
15%7%33%27%15%
264
May1st to 15thDay
11%8%34%31%11%1
468
16th to endDay
14%425%33%19%2
517
June1st to 15thDay
5%9%40%35%7%
495
16th to endDay
8%17%30%38%13%
495
July1st to 15thDay
41431%42%15%
475
16th to endDay
41222%48%20%
515
August1st to 15thDay
5%218%52%21%
493
16th to endDay
11%1421%30%29%
271
September1st to 15thDay
415%15%42%30%
135
16th to endDay
3314%42%35%
108
October1st to 15thDay
2236%45%13%
90
16th to endDay
19%10%25%34%10%
96
November1st to 15thDay
15%324%34%15%6%
90
16th to endDay
23%10%26%24%8%6%
90
December1st to 15thDay
26%5%20%25%13%8%
90
16th to endDay
22%15%31%21%7%1
96
January1st to 15thNight
20%8%28%32%9%
900
16th to endNight
20%10%30%31%6%
960
February1st to 15thNight
18%11%29%34%5%
717
16th to endNight
18%10%42%23%5%
584
March1st to 15thNight
18%9%37%29%5%
540
16th to endNight
11%10%39%32%6%
576
April1st to 15thNight
9%10%43%32%4
539
16th to endNight
14%7%40%28%9%
540
May1st to 15thNight
9%7%42%33%6%
540
16th to endNight
3331%43%17%
563
June1st to 15thNight
314%53%26%1
540
16th to endNight
219%49%32%3
540
July1st to 15thNight
46%46%38%3
510
16th to endNight
4345%41%4
564
August1st to 15thNight
1247%43%5%
539
16th to endNight
6%435%47%5%
573
September1st to 15thNight
6%5%32%48%6%
540
16th to endNight
10%8%27%46%6%
513
October1st to 15thNight
7%213%41%31%4
561
16th to endNight
9%5%21%32%27%3
704
November1st to 15thNight
12%5%24%35%21%1
700
16th to endNight
14%7%26%34%17%1
834
December1st to 15thNight
20%9%26%32%11%
900
16th to endNight
21%9%27%31%10%
960
Page generated at 2017-09-23 05:43:36. Version ac04

Copyright 2017 A. Danko


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