Otter Creek Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Otter Creek Observatory clear sky chart from 2005-11-05 to 2017-09-15.

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
42%
15613
21%
46749
14%
15570
49%
15570
25%
30139

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
20%
899
16%
2506
7%
895
28%
895
17%
1832
January16th to endNight
20%
820
18%
2509
8%
820
31%
820
18%
1745
February1st to 15thNight
19%
704
15%
2112
5%
701
29%
701
16%
1518
February16th to endNight
18%
631
16%
1893
6%
631
27%
631
17%
1340
March1st to 15thNight
23%
720
16%
2139
9%
720
29%
720
18%
1496
March16th to endNight
32%
729
15%
2073
8%
729
38%
729
20%
1451
April1st to 15thNight
34%
539
22%
1797
13%
539
47%
539
26%
1075
April16th to endNight
38%
540
21%
1719
13%
540
47%
540
25%
1097
May1st to 15thNight
39%
539
16%
1619
10%
539
45%
539
21%
1117
May16th to endNight
57%
561
20%
1684
15%
561
61%
561
28%
1073
June1st to 15thNight
64%
540
20%
1504
16%
540
68%
540
39%
881
June16th to endNight
67%
540
22%
1440
16%
540
70%
540
40%
851
July1st to 15thNight
64%
510
17%
1360
14%
510
66%
510
33%
870
July16th to endNight
72%
564
24%
1535
21%
531
75%
531
38%
888
August1st to 15thNight
76%
539
25%
1649
25%
536
77%
536
40%
906
August16th to endNight
76%
573
24%
1910
26%
573
78%
573
38%
1006
September1st to 15thNight
64%
619
26%
1879
25%
619
66%
619
33%
1111
September16th to endNight
58%
657
27%
1815
20%
657
62%
657
34%
1113
October1st to 15thNight
55%
660
33%
1815
24%
660
61%
660
38%
1044
October16th to endNight
39%
704
25%
2222
20%
704
49%
704
28%
1347
November1st to 15thNight
42%
700
28%
2276
22%
700
53%
700
30%
1315
November16th to endNight
33%
720
22%
2340
16%
720
43%
720
21%
1492
December1st to 15thNight
28%
720
15%
2340
9%
720
35%
720
16%
1654
December16th to endNight
21%
885
16%
2613
7%
885
30%
885
16%
1917

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
13%6%35%5%3445%7%39%
47973
Night
13%6%35%42445%7%42%
46935
TransparencyDay
43%5%11%22%14%2
47663
Night
41%5%10%22%16%3
46750
SeeingDay
15%8%22%23%18%10%
5666
Night
17%9%25%27%18%2
15617

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
19%9%39%42434433%
1432
16th to endDay
15%9%37%5%34346%36%
1709
February1st to 15thDay
16%10%5%7%5%23346%34%
1750
16th to endDay
14%8%48%6%3445%7%32%
1580
March1st to 15thDay
22%8%35%5%24335%36%
1821
16th to endDay
16%7%36%5%3446%7%32%
2159
April1st to 15thDay
13%7%26%5%34447%40%
2151
16th to endDay
16%6%25%5%3435%6%39%
2241
May1st to 15thDay
19%7%35%5%3445%7%33%
2331
16th to endDay
9%6%26%6%36%6%7%8%36%
2431
June1st to 15thDay
8%425%6%35%5%5%8%44%
2453
16th to endDay
6%425%5%446%7%9%42%
2520
July1st to 15thDay
13%5%25%5%35%47%10%36%
2520
16th to endDay
8%424446%6%8%10%39%
2525
August1st to 15thDay
7%5%25%5%35%5%7%9%41%
2298
16th to endDay
8%5%245%45%5%6%9%43%
2292
September1st to 15thDay
14%5%245%34449%40%
2056
16th to endDay
12%5%35%5%34346%45%
1815
October1st to 15thDay
11%424422435%52%
1815
16th to endDay
17%425%33233448%
1647
November1st to 15thDay
13%423434345%49%
1582
16th to endDay
17%7%35%414335%42%
1620
December1st to 15thDay
22%10%46%422435%31%
1620
16th to endDay
18%12%46%333345%34%
1605
January1st to 15thNight
17%9%49%6%23345%32%
2506
16th to endNight
17%10%36%5%3445%6%34%
2509
February1st to 15thNight
19%9%45%5%34445%32%
2103
16th to endNight
15%9%48%6%24346%33%
1893
March1st to 15thNight
17%8%46%5%24445%36%
2139
16th to endNight
15%8%36%5%2445%7%35%
2073
April1st to 15thNight
13%6%2342445%7%45%
1797
16th to endNight
13%6%45%5%2435%6%41%
1719
May1st to 15thNight
16%6%36%5%34447%37%
1619
16th to endNight
7%326%6%45%6%7%8%42%
1682
June1st to 15thNight
6%32442346%10%50%
1504
16th to endNight
4324425%6%6%13%46%
1440
July1st to 15thNight
9%5%244245%49%46%
1440
16th to endNight
7%2134245%7%10%49%
1641
August1st to 15thNight
5%413425%45%10%52%
1660
16th to endNight
432442446%11%51%
1910
September1st to 15thNight
13%424323447%49%
1879
16th to endNight
10%5%245%2345%6%49%
1815
October1st to 15thNight
9%414433246%54%
1815
16th to endNight
16%425%32333449%
2222
November1st to 15thNight
12%5%23423435%52%
2276
16th to endNight
17%7%24423345%43%
2340
December1st to 15thNight
22%9%45%5%23345%32%
2340
16th to endNight
21%10%37%433345%31%
2613

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
53%49%20%11%
1433
16th to endDay
49%410%27%8%1
1709
February1st to 15thDay
52%38%25%9%1
1752
16th to endDay
50%5%13%20%9%
1580
March1st to 15thDay
50%410%19%14%1
1821
16th to endDay
50%6%11%22%8%
2160
April1st to 15thDay
43%5%8%22%17%1
2151
16th to endDay
44%410%23%12%3
2241
May1st to 15thDay
49%6%11%19%11%
2331
16th to endDay
41%8%14%18%13%2
2435
June1st to 15thDay
36%6%11%24%17%2
2453
16th to endDay
34%8%12%20%19%3
2520
July1st to 15thDay
41%7%13%18%13%4
2371
16th to endDay
34%8%16%23%13%2
2369
August1st to 15thDay
35%8%13%23%16%2
2285
16th to endDay
36%6%13%21%18%4
2292
September1st to 15thDay
41%5%9%20%17%4
2056
16th to endDay
39%47%20%24%3
1815
October1st to 15thDay
33%48%25%24%3
1815
16th to endDay
39%37%26%19%2
1647
November1st to 15thDay
36%47%24%19%7%
1582
16th to endDay
44%37%24%18%1
1620
December1st to 15thDay
54%410%19%9%2
1620
16th to endDay
52%412%21%8%
1605
January1st to 15thNight
53%48%18%13%1
2506
16th to endNight
50%410%23%9%1
2509
February1st to 15thNight
54%39%21%9%1
2112
16th to endNight
52%313%20%10%
1893
March1st to 15thNight
50%49%20%12%3
2139
16th to endNight
47%5%13%21%9%1
2073
April1st to 15thNight
37%5%11%21%20%3
1797
16th to endNight
42%48%25%13%5%
1719
May1st to 15thNight
47%6%9%23%11%1
1620
16th to endNight
35%9%12%20%18%3
1684
June1st to 15thNight
28%6%14%24%21%3
1504
16th to endNight
26%8%16%22%20%6%
1440
July1st to 15thNight
35%6%13%23%17%3
1360
16th to endNight
26%9%14%28%18%2
1535
August1st to 15thNight
25%7%15%26%21%3
1649
16th to endNight
25%7%16%26%20%4
1910
September1st to 15thNight
33%5%9%23%21%6%
1879
16th to endNight
34%48%21%24%5%
1815
October1st to 15thNight
31%38%24%27%5%
1815
16th to endNight
39%37%26%19%4
2222
November1st to 15thNight
34%47%23%23%7%
2276
16th to endNight
44%38%23%17%2
2340
December1st to 15thNight
54%311%18%10%1
2340
16th to endNight
54%410%18%9%1
2613

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
34%16%34%6%6%1
90
16th to endDay
14%39%35%8%2
96
February1st to 15thDay
20%36%31%11%1
90
16th to endDay
19%18%46%11%3
81
March1st to 15thDay
31%19%31%14%2
111
16th to endDay
18%18%35%18%8%1
288
April1st to 15thDay
19%13%28%25%11%1
270
16th to endDay
19%10%30%21%13%5%
270
May1st to 15thDay
24%11%27%18%10%6%
288
16th to endDay
17%6%26%22%14%12%
331
June1st to 15thDay
10%417%30%24%11%
428
16th to endDay
9%6%26%26%20%10%
495
July1st to 15thDay
14%318%29%21%12%
475
16th to endDay
6%110%29%30%21%
385
August1st to 15thDay
10%29%25%29%23%
313
16th to endDay
11%212%25%28%19%
332
September1st to 15thDay
16%211%19%34%15%
311
16th to endDay
14%314%24%27%15%
254
October1st to 15thDay
12%5%24%28%16%11%
255
16th to endDay
20%9%30%24%13%
137
November1st to 15thDay
8%8%25%33%14%8%
90
16th to endDay
27%14%32%21%4
90
December1st to 15thDay
22%17%35%15%5%3
90
16th to endDay
29%22%37%7%3
96
January1st to 15thNight
22%17%33%23%3
900
16th to endNight
22%18%34%20%3
820
February1st to 15thNight
26%14%35%22%1
704
16th to endNight
21%15%39%21%1
631
March1st to 15thNight
21%14%34%24%4
720
16th to endNight
19%12%29%28%9%
729
April1st to 15thNight
17%10%35%25%11%
539
16th to endNight
16%9%30%30%12%1
540
May1st to 15thNight
18%6%25%30%17%
540
16th to endNight
8%221%35%25%7%
563
June1st to 15thNight
8%117%39%29%3
540
16th to endNight
6%116%39%33%2
540
July1st to 15thNight
12%111%31%39%3
510
16th to endNight
7%9%30%41%10%
564
August1st to 15thNight
7%16%32%43%8%
539
16th to endNight
6%8%34%45%5%
573
September1st to 15thNight
14%112%29%35%7%
619
16th to endNight
12%316%29%34%5%
657
October1st to 15thNight
11%6%21%27%27%6%
660
16th to endNight
18%9%29%28%14%
704
November1st to 15thNight
15%9%28%26%19%1
700
16th to endNight
22%15%25%27%9%
720
December1st to 15thNight
26%12%27%23%8%1
720
16th to endNight
29%12%31%22%3
885
Page generated at 2017-09-16 00:58:31. Version ac04

Copyright 2017 A. Danko


Otter Creek Observatory Clear Sky Chart | Charts Home