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Old Tunnel State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Old Tunnel State Park clear sky chart from 2005-11-05 to 2018-01-12.

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%
15918
27%
48389
18%
15873
59%
15873
34%
27903

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
38%
953
28%
2472
12%
951
48%
951
34%
1545
January16th to endNight
38%
849
32%
2385
14%
849
51%
849
34%
1413
February1st to 15thNight
36%
704
28%
2107
13%
698
48%
698
31%
1207
February16th to endNight
27%
632
29%
1894
9%
632
43%
632
32%
1080
March1st to 15thNight
36%
586
28%
2026
15%
586
49%
586
27%
1173
March16th to endNight
36%
576
24%
2112
17%
576
48%
576
27%
1196
April1st to 15thNight
29%
539
23%
1977
13%
539
44%
539
27%
1112
April16th to endNight
31%
540
26%
1746
15%
540
47%
540
27%
1088
May1st to 15thNight
33%
539
23%
1619
14%
539
45%
539
30%
985
May16th to endNight
49%
562
24%
1684
21%
561
57%
561
31%
1040
June1st to 15thNight
70%
540
22%
1620
23%
540
75%
540
49%
816
June16th to endNight
69%
540
23%
1620
26%
540
71%
540
40%
914
July1st to 15thNight
75%
510
20%
1530
22%
510
78%
510
39%
873
July16th to endNight
81%
564
25%
1594
29%
531
84%
531
45%
845
August1st to 15thNight
88%
539
28%
1723
35%
536
88%
536
52%
811
August16th to endNight
75%
573
20%
1945
25%
573
75%
573
31%
1142
September1st to 15thNight
77%
540
19%
1980
24%
540
77%
540
30%
1134
September16th to endNight
65%
537
24%
1980
25%
537
68%
537
27%
1172
October1st to 15thNight
70%
540
31%
1980
31%
540
74%
540
38%
1000
October16th to endNight
58%
746
38%
2282
25%
746
67%
746
49%
1123
November1st to 15thNight
52%
819
27%
2339
16%
819
58%
819
37%
1368
November16th to endNight
49%
975
32%
2535
15%
975
58%
975
41%
1481
December1st to 15thNight
43%
975
29%
2535
16%
975
49%
975
33%
1601
December16th to endNight
36%
1040
24%
2704
11%
1040
44%
1040
29%
1784

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
12%5%24424447%46%
48938
Night
11%423323347%53%
48591
Cloud CoverDay
12%5%24424447%46%
48936
Night
10%5%23323347%53%
48591
TransparencyDay
37%5%9%19%18%9%
48636
Night
31%5%10%20%19%12%
48396
SeeingDay
13%5%20%30%24%6%
5725
Night
13%6%25%35%17%1
15923

By Month

Percentage Cloud Cover SW (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
14%5%15%32333450%
1710
16th to endDay
14%323223326%54%
1848
February1st to 15thDay
13%6%24322435%53%
1750
16th to endDay
14%6%23223445%52%
1580
March1st to 15thDay
18%6%23313335%47%
1932
16th to endDay
16%5%23323345%49%
2112
April1st to 15thDay
14%5%24423346%47%
1971
16th to endDay
14%5%34424446%45%
2211
May1st to 15thDay
17%6%345%25%45%6%38%
2331
16th to endDay
17%6%35%435%45%7%37%
2430
June1st to 15thDay
6%325%4345%6%10%47%
2340
16th to endDay
11%425%6%37%5%6%9%36%
2340
July1st to 15thDay
11%426%5%36%46%8%41%
2340
16th to endDay
8%324435%5%7%10%43%
2466
August1st to 15thDay
3112435%46%10%57%
2224
16th to endDay
8%425%6%46%5%7%8%38%
2256
September1st to 15thDay
12%5%25%6%35%5%5%7%39%
1980
16th to endDay
12%4245%35%5%5%6%42%
1980
October1st to 15thDay
10%5%24424336%52%
1980
16th to endDay
8%312212245%63%
1929
November1st to 15thDay
13%7%25%424346%43%
1846
16th to endDay
13%5%2231223457%
1755
December1st to 15thDay
18%6%24322335%46%
1755
16th to endDay
16%7%24413345%46%
1872
January1st to 15thNight
16%413313335%51%
2472
16th to endNight
14%423222245%52%
2385
February1st to 15thNight
12%6%2321223455%
2102
16th to endNight
12%424323246%53%
1894
March1st to 15thNight
14%5%24313345%51%
2026
16th to endNight
14%413323446%51%
2112
April1st to 15thNight
12%5%34313336%51%
1977
16th to endNight
14%6%24424235%49%
1746
May1st to 15thNight
13%5%2331345%6%48%
1619
16th to endNight
12%425%424348%47%
1683
June1st to 15thNight
311221335%8%64%
1620
16th to endNight
7%31332435%9%55%
1620
July1st to 15thNight
6%31341446%11%52%
1620
16th to endNight
432222345%10%57%
1702
August1st to 15thNight
211221345%9%65%
1733
16th to endNight
7%4145%2446%10%48%
1945
September1st to 15thNight
7%4245%35%5%5%8%48%
1980
16th to endNight
8%6%25%5%345%5%6%46%
1980
October1st to 15thNight
9%313222347%59%
1980
16th to endNight
8%312212235%66%
2282
November1st to 15thNight
11%423313336%54%
2339
16th to endNight
12%5%12212235%59%
2535
December1st to 15thNight
16%5%13312347%49%
2535
16th to endNight
15%7%24323335%47%
2704

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
14%5%25%31433450%
1710
16th to endDay
13%423323335%54%
1848
February1st to 15thDay
13%6%24312345%52%
1750
16th to endDay
14%5%23213345%51%
1580
March1st to 15thDay
17%6%23322336%47%
1932
16th to endDay
15%5%24323435%49%
2110
April1st to 15thDay
13%6%24334346%47%
1971
16th to endDay
14%6%24424346%45%
2211
May1st to 15thDay
16%6%35%5%245%46%38%
2331
16th to endDay
16%7%35%43445%7%36%
2430
June1st to 15thDay
44245%345%7%10%47%
2340
16th to endDay
9%436%6%37%6%6%9%36%
2340
July1st to 15thDay
9%435%5%35%5%6%8%41%
2340
16th to endDay
7%3245%36%5%7%10%43%
2466
August1st to 15thDay
3213435%45%10%57%
2224
16th to endDay
8%5%26%7%46%5%6%8%37%
2256
September1st to 15thDay
11%5%36%5%35%5%6%7%39%
1980
16th to endDay
12%5%25%5%45%5%5%6%42%
1980
October1st to 15thDay
9%5%24434346%51%
1980
16th to endDay
8%413222245%63%
1929
November1st to 15thDay
13%7%26%43435%7%42%
1846
16th to endDay
11%6%23312235%56%
1755
December1st to 15thDay
17%8%24413235%46%
1755
16th to endDay
15%7%24323345%46%
1872
January1st to 15thNight
15%414313335%51%
2472
16th to endNight
14%5%23223245%52%
2385
February1st to 15thNight
11%6%2331323456%
2102
16th to endNight
11%6%24313346%53%
1894
March1st to 15thNight
13%5%24322345%51%
2026
16th to endNight
13%5%13323346%52%
2112
April1st to 15thNight
10%6%24323346%51%
1977
16th to endNight
13%6%34324325%49%
1746
May1st to 15thNight
11%6%34313447%48%
1619
16th to endNight
10%6%35%32435%8%47%
1683
June1st to 15thNight
311311435%8%64%
1620
16th to endNight
6%31332335%10%55%
1620
July1st to 15thNight
6%31242446%11%52%
1620
16th to endNight
422322346%10%57%
1702
August1st to 15thNight
111221345%9%65%
1733
16th to endNight
6%4145%2446%9%47%
1945
September1st to 15thNight
6%4235%25%46%8%48%
1980
16th to endNight
8%7%245%245%5%7%46%
1980
October1st to 15thNight
9%313323337%59%
1980
16th to endNight
8%312213235%66%
2282
November1st to 15thNight
10%5%24323246%55%
2339
16th to endNight
10%6%12222235%59%
2535
December1st to 15thNight
14%7%23323247%49%
2535
16th to endNight
15%7%2432333447%
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
37%35%19%21%14%
1711
16th to endDay
33%26%14%26%16%
1848
February1st to 15thDay
34%36%13%23%18%
1751
16th to endDay
35%3418%22%15%
1580
March1st to 15thDay
39%47%14%19%14%
1932
16th to endDay
38%47%17%20%11%
2112
April1st to 15thDay
39%47%15%19%13%
1971
16th to endDay
40%5%7%18%17%11%
2211
May1st to 15thDay
45%6%8%14%18%6%
2331
16th to endDay
46%7%9%16%16%3
2434
June1st to 15thDay
30%6%12%22%21%5%
2340
16th to endDay
42%6%11%20%15%3
2340
July1st to 15thDay
38%7%13%26%11%2
2201
16th to endDay
30%9%18%28%11%
2311
August1st to 15thDay
21%7%15%37%16%1
2210
16th to endDay
40%9%13%23%9%2
2256
September1st to 15thDay
43%6%10%18%17%4
1980
16th to endDay
40%7%9%16%17%8%
1980
October1st to 15thDay
33%5%11%18%20%10%
1980
16th to endDay
24%35%15%28%21%
1929
November1st to 15thDay
41%48%18%17%10%
1846
16th to endDay
32%3415%22%21%
1755
December1st to 15thDay
42%35%15%21%11%
1755
16th to endDay
40%37%14%22%10%
1872
January1st to 15thNight
34%3417%21%17%
2472
16th to endNight
34%25%15%24%18%
2385
February1st to 15thNight
33%25%12%22%22%
2112
16th to endNight
33%36%15%23%17%
1894
March1st to 15thNight
36%47%14%20%16%
2026
16th to endNight
34%5%9%16%20%12%
2112
April1st to 15thNight
35%48%17%17%17%
1977
16th to endNight
39%5%8%17%17%13%
1746
May1st to 15thNight
35%6%11%20%16%10%
1620
16th to endNight
35%6%13%25%14%4
1685
June1st to 15thNight
18%7%14%29%25%4
1620
16th to endNight
26%7%16%29%16%3
1620
July1st to 15thNight
25%9%19%31%13%1
1530
16th to endNight
20%8%26%31%11%1
1594
August1st to 15thNight
16%6%20%39%17%
1723
16th to endNight
30%9%21%26%9%2
1945
September1st to 15thNight
32%7%15%21%17%5%
1980
16th to endNight
36%6%13%18%16%8%
1980
October1st to 15thNight
25%5%13%24%18%11%
1980
16th to endNight
21%26%17%28%22%
2282
November1st to 15thNight
31%5%9%22%19%12%
2339
16th to endNight
28%37%16%21%22%
2535
December1st to 15thNight
36%47%17%21%12%
2535
16th to endNight
40%36%14%21%13%
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
20%10%39%20%7%1
123
16th to endDay
15%12%39%22%9%
96
February1st to 15thDay
12%21%31%27%6%1
90
16th to endDay
19%7%41%28%2
81
March1st to 15thDay
23%10%37%16%12%
90
16th to endDay
11%7%36%31%11%2
96
April1st to 15thDay
15%15%42%23%3
90
16th to endDay
14%14%37%26%6%
321
May1st to 15thDay
18%9%37%26%6%
468
16th to endDay
22%7%26%28%13%2
517
June1st to 15thDay
5%116%44%28%3
495
16th to endDay
11%214%35%29%8%
495
July1st to 15thDay
8%10%38%33%7%
475
16th to endDay
6%430%46%11%
515
August1st to 15thDay
4330%44%16%
379
16th to endDay
11%110%33%27%15%
296
September1st to 15thDay
35%19%48%22%
135
16th to endDay
14%319%47%14%
135
October1st to 15thDay
410%28%37%18%
135
16th to endDay
12%418%35%25%3
144
November1st to 15thDay
27%5%25%24%11%4
135
16th to endDay
20%7%28%22%14%5%
135
December1st to 15thDay
23%8%25%24%14%3
135
16th to endDay
27%14%28%25%4
144
January1st to 15thNight
18%9%28%34%8%
956
16th to endNight
17%8%31%33%8%
849
February1st to 15thNight
17%13%30%31%6%
704
16th to endNight
15%10%44%26%2
632
March1st to 15thNight
17%8%33%34%5%
586
16th to endNight
15%9%36%32%4
576
April1st to 15thNight
13%8%43%30%2
539
16th to endNight
14%10%41%26%7%
540
May1st to 15thNight
13%9%40%31%5%
540
16th to endNight
11%6%28%38%13%
563
June1st to 15thNight
222%50%22%
540
16th to endNight
6%19%47%23%1
540
July1st to 15thNight
6%110%45%33%2
510
16th to endNight
46%46%39%3
564
August1st to 15thNight
2238%49%5%
539
16th to endNight
8%5%38%40%6%
573
September1st to 15thNight
8%5%36%41%6%
540
16th to endNight
10%110%38%33%5%
537
October1st to 15thNight
10%213%41%28%4
540
16th to endNight
9%424%32%26%3
746
November1st to 15thNight
12%5%24%36%19%2
819
16th to endNight
15%6%25%35%14%1
975
December1st to 15thNight
19%8%26%34%10%1
975
16th to endNight
19%9%29%32%8%
1040
Page generated at 2018-01-12 21:01:33. Version ac04

Copyright 2018 A. Danko


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