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 2018-04-23.

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
41%
16490
21%
49398
14%
16447
48%
16447
25%
31901

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
21%
974
16%
2716
7%
970
29%
970
18%
1981
January16th to endNight
21%
888
18%
2718
8%
888
32%
888
18%
1875
February1st to 15thNight
19%
764
14%
2292
5%
761
28%
761
16%
1657
February16th to endNight
18%
683
15%
2049
5%
683
26%
683
16%
1474
March1st to 15thNight
23%
780
17%
2317
9%
780
29%
780
18%
1609
March16th to endNight
31%
790
15%
2246
8%
790
37%
790
20%
1595
April1st to 15thNight
33%
584
22%
1947
13%
584
46%
584
25%
1180
April16th to endNight
37%
558
21%
1777
14%
558
47%
558
25%
1136
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
60%
717
29%
1980
23%
717
64%
717
36%
1192
October1st to 15thNight
55%
720
32%
1980
24%
720
62%
720
37%
1143
October16th to endNight
40%
768
27%
2424
21%
768
50%
768
28%
1466
November1st to 15thNight
40%
760
27%
2471
21%
760
51%
760
29%
1462
November16th to endNight
35%
780
24%
2535
18%
780
45%
780
23%
1590
December1st to 15thNight
29%
780
15%
2535
9%
780
37%
780
17%
1752
December16th to endNight
20%
959
16%
2831
7%
959
29%
959
16%
2086

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
14%6%35%5%3445%7%39%
50114
Night
13%6%35%424447%42%
49584
TransparencyDay
43%5%11%22%14%2
49804
Night
41%5%10%22%16%3
49399
SeeingDay
16%9%23%22%17%9%
6392
Night
17%9%25%27%17%2
16494

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%
1552
16th to endDay
14%9%37%5%33346%37%
1852
February1st to 15thDay
17%10%5%8%5%22336%34%
1900
16th to endDay
16%8%47%6%3445%6%31%
1710
March1st to 15thDay
21%8%35%5%14335%37%
1973
16th to endDay
18%8%36%5%3446%7%31%
2339
April1st to 15thDay
14%7%26%5%33447%39%
2331
16th to endDay
16%6%35%5%3435%6%38%
2297
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%
2067
16th to endDay
11%5%25%5%34345%48%
1980
October1st to 15thDay
12%424423445%51%
1980
16th to endDay
16%425%33333448%
1797
November1st to 15thDay
14%5%23434445%47%
1717
16th to endDay
16%7%35%414345%44%
1755
December1st to 15thDay
21%10%46%422435%33%
1755
16th to endDay
19%12%46%333246%33%
1739
January1st to 15thNight
17%9%48%6%24345%32%
2716
16th to endNight
16%9%36%5%3445%6%35%
2718
February1st to 15thNight
19%9%46%5%34436%32%
2283
16th to endNight
16%10%48%6%34346%31%
2049
March1st to 15thNight
17%8%46%5%24435%37%
2317
16th to endNight
17%8%36%5%2445%6%34%
2246
April1st to 15thNight
15%6%2332445%7%44%
1947
16th to endNight
13%7%45%5%2435%6%41%
1777
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
9%4245%2345%6%51%
1980
October1st to 15thNight
9%414433246%53%
1980
16th to endNight
15%425%32333449%
2424
November1st to 15thNight
13%5%23423435%50%
2471
16th to endNight
16%7%24323345%44%
2535
December1st to 15thNight
20%8%45%5%33445%34%
2535
16th to endNight
21%11%37%433445%30%
2831

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
52%49%20%11%
1553
16th to endDay
48%39%27%8%1
1852
February1st to 15thDay
52%38%24%8%1
1902
16th to endDay
51%5%12%19%9%1
1710
March1st to 15thDay
49%49%19%15%1
1973
16th to endDay
51%6%11%22%7%
2340
April1st to 15thDay
44%5%9%23%16%1
2331
16th to endDay
45%49%23%13%3
2297
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
2067
16th to endDay
37%5%8%22%23%2
1980
October1st to 15thDay
34%48%25%23%2
1980
16th to endDay
39%47%26%19%2
1797
November1st to 15thDay
38%47%24%18%6%
1717
16th to endDay
42%36%25%19%1
1755
December1st to 15thDay
52%410%19%10%1
1755
16th to endDay
53%412%20%8%
1739
January1st to 15thNight
53%48%17%14%1
2716
16th to endNight
49%410%23%10%1
2718
February1st to 15thNight
54%39%20%9%1
2292
16th to endNight
53%412%18%9%1
2049
March1st to 15thNight
50%48%20%13%2
2317
16th to endNight
49%5%12%21%9%1
2246
April1st to 15thNight
38%411%22%19%3
1947
16th to endNight
42%48%25%14%5%
1777
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
32%5%8%23%24%5%
1980
October1st to 15thNight
31%39%24%26%4
1980
16th to endNight
38%37%25%20%4
2424
November1st to 15thNight
36%47%23%21%6%
2471
16th to endNight
42%38%23%19%2
2535
December1st to 15thNight
51%310%20%11%1
2535
16th to endNight
55%410%18%9%1
2831

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
30%13%36%11%7%1
135
16th to endDay
16%31%38%11%2
144
February1st to 15thDay
26%27%34%10%1
135
16th to endDay
30%15%41%9%3
120
March1st to 15thDay
26%17%40%13%1
158
16th to endDay
22%20%32%16%7%
352
April1st to 15thDay
21%15%28%23%10%1
330
16th to endDay
19%10%28%23%12%5%
289
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%33%15%
315
16th to endDay
12%314%21%30%16%
314
October1st to 15thDay
14%5%24%26%17%11%
315
16th to endDay
19%10%31%22%13%3
189
November1st to 15thDay
14%11%29%28%11%5%
135
16th to endDay
21%11%34%25%5%1
135
December1st to 15thDay
16%25%33%15%7%2
135
16th to endDay
32%20%36%6%3
144
January1st to 15thNight
22%16%33%23%4
975
16th to endNight
22%18%35%20%3
888
February1st to 15thNight
27%14%34%22%1
764
16th to endNight
22%15%39%20%2
683
March1st to 15thNight
22%14%34%24%4
780
16th to endNight
21%12%28%27%8%
790
April1st to 15thNight
19%9%35%24%10%
584
16th to endNight
16%9%30%29%12%1
558
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
11%216%27%35%6%
717
October1st to 15thNight
11%6%20%27%27%6%
720
16th to endNight
17%8%29%27%14%1
768
November1st to 15thNight
16%9%29%25%18%1
760
16th to endNight
21%14%25%27%10%
780
December1st to 15thNight
24%12%27%25%8%1
780
16th to endNight
29%12%31%22%3
959
Page generated at 2018-04-24 10:03:06. Version ac04

Copyright 2018 A. Danko


Otter Creek Observatory Clear Sky Chart |Charts Home