Crane Point Nature Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Crane Point Nature Center clear sky chart from 2005-11-05 to 2018-03-11.

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
69%
16933
18%
49094
17%
16896
70%
16896
28%
31849

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
61%
776
17%
2522
19%
776
63%
776
25%
1603
January16th to endNight
60%
832
23%
2590
22%
832
64%
832
28%
1599
February1st to 15thNight
64%
761
26%
2290
23%
760
68%
760
33%
1374
February16th to endNight
74%
683
31%
1887
26%
683
77%
683
42%
1074
March1st to 15thNight
71%
764
23%
2101
19%
764
74%
764
39%
1253
March16th to endNight
71%
768
26%
2112
24%
768
72%
768
39%
1269
April1st to 15thNight
79%
718
22%
1976
20%
718
81%
718
43%
1141
April16th to endNight
74%
720
24%
1857
18%
720
75%
720
38%
1143
May1st to 15thNight
81%
719
24%
1799
18%
719
82%
719
51%
1019
May16th to endNight
68%
600
15%
1722
13%
600
68%
600
26%
1144
June1st to 15thNight
56%
540
8%
1620
8%
540
56%
540
15%
1225
June16th to endNight
74%
540
7%
1620
8%
540
74%
540
21%
1119
July1st to 15thNight
75%
510
6%
1530
6%
510
75%
510
23%
1022
July16th to endNight
81%
564
13%
1595
13%
531
81%
531
30%
972
August1st to 15thNight
77%
597
9%
1706
7%
594
77%
594
28%
1110
August16th to endNight
71%
764
7%
2101
7%
764
71%
764
22%
1520
September1st to 15thNight
69%
720
4%
1980
4%
720
69%
720
19%
1493
September16th to endNight
63%
717
6%
1980
6%
717
63%
717
16%
1534
October1st to 15thNight
66%
720
12%
2052
14%
720
66%
720
18%
1535
October16th to endNight
58%
768
15%
2304
16%
768
59%
768
19%
1645
November1st to 15thNight
65%
760
22%
2281
22%
760
68%
760
29%
1421
November16th to endNight
65%
780
24%
2340
25%
780
67%
780
28%
1505
December1st to 15thNight
67%
780
19%
2425
19%
780
69%
780
26%
1546
December16th to endNight
72%
832
24%
2704
25%
832
74%
832
31%
1583

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
5%4245%36%6%8%12%39%
49513
Night
6%425%5%36%6%7%11%39%
49295
TransparencyDay
34%10%19%21%11%2
49214
Night
37%9%17%21%12%2
49098
SeeingDay
9%7%20%33%27%
6679
Night
9%19%24%36%19%
16943

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
8%4245%35%5%6%12%41%
1746
16th to endDay
6%425%5%36%6%8%9%41%
1983
February1st to 15thDay
6%4333245%6%9%50%
1900
16th to endDay
321232445%11%57%
1869
March1st to 15thDay
2313325%5%7%12%51%
2096
16th to endDay
321342445%10%55%
2111
April1st to 15thDay
22122245%6%12%55%
1972
16th to endDay
43133135%6%11%55%
2100
May1st to 15thDay
321322345%10%59%
2152
16th to endDay
7%5%245%37%6%8%12%36%
2398
June1st to 15thDay
9%7%37%8%47%8%9%11%22%
2340
16th to endDay
6%425%6%5%7%8%10%15%26%
2340
July1st to 15thDay
4425%5%48%8%11%16%26%
2340
16th to endDay
33146%48%8%11%17%29%
2465
August1st to 15thDay
3426%8%47%9%10%14%26%
2224
16th to endDay
6%426%7%47%9%10%13%26%
2101
September1st to 15thDay
6%427%7%5%8%10%11%12%21%
1980
16th to endDay
8%7%36%7%47%8%10%12%23%
1980
October1st to 15thDay
8%5%27%7%5%7%7%8%12%28%
1905
16th to endDay
10%7%35%5%36%6%8%9%32%
1920
November1st to 15thDay
6%4234245%7%8%50%
1907
16th to endDay
6%4245%25%5%5%8%47%
1950
December1st to 15thDay
7%5%24435%5%6%11%43%
1862
16th to endDay
3224425%7%8%12%46%
1872
January1st to 15thNight
7%5%25%5%346%8%12%36%
2522
16th to endNight
6%5%245%35%6%6%10%42%
2590
February1st to 15thNight
7%324435%5%6%8%48%
2283
16th to endNight
33134245%6%8%54%
1887
March1st to 15thNight
3314435%5%6%9%51%
2101
16th to endNight
3315%5%25%46%9%51%
2112
April1st to 15thNight
3213325%5%6%10%52%
1976
16th to endNight
5%3244245%7%9%49%
1857
May1st to 15thNight
221432336%10%59%
1799
16th to endNight
9%426%5%36%5%8%9%37%
1721
June1st to 15thNight
10%8%38%9%47%5%6%10%23%
1620
16th to endNight
4325%7%5%8%8%10%14%28%
1620
July1st to 15thNight
3326%6%47%7%9%15%33%
1620
16th to endNight
23245%47%7%10%15%37%
1703
August1st to 15thNight
3425%6%37%7%9%15%34%
1717
16th to endNight
6%5%26%8%5%7%8%8%12%28%
2101
September1st to 15thNight
6%5%26%8%5%8%9%9%12%25%
1980
16th to endNight
7%8%38%8%5%8%6%8%10%23%
1980
October1st to 15thNight
9%5%26%7%5%8%8%8%11%25%
2052
16th to endNight
11%8%37%6%46%6%7%8%30%
2304
November1st to 15thNight
8%424435%6%5%10%44%
2281
16th to endNight
8%4245%35%5%7%10%42%
2340
December1st to 15thNight
7%5%25%5%35%5%7%9%42%
2425
16th to endNight
6%324435%5%7%11%45%
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
36%8%16%23%12%3
1747
16th to endDay
36%7%15%21%15%3
1983
February1st to 15thDay
29%6%11%30%17%4
1902
16th to endDay
21%5%13%32%21%5%
1869
March1st to 15thDay
26%6%15%30%19%2
2096
16th to endDay
24%7%16%29%18%3
2112
April1st to 15thDay
21%5%17%36%16%1
1972
16th to endDay
22%7%16%32%19%2
2100
May1st to 15thDay
21%6%18%32%16%4
2152
16th to endDay
36%9%20%25%7%
2402
June1st to 15thDay
50%11%21%13%2
2340
16th to endDay
39%15%33%10%
2340
July1st to 15thDay
38%16%33%11%
2201
16th to endDay
31%16%35%14%1
2310
August1st to 15thDay
37%16%27%17%2
2211
16th to endDay
40%16%28%13%
2101
September1st to 15thDay
46%17%24%10%
1980
16th to endDay
45%15%24%11%2
1980
October1st to 15thDay
46%10%15%18%6%2
1905
16th to endDay
44%7%13%19%10%3
1920
November1st to 15thDay
32%6%11%24%23%2
1907
16th to endDay
34%7%11%17%23%6%
1950
December1st to 15thDay
35%9%13%20%19%2
1862
16th to endDay
29%7%12%29%19%2
1872
January1st to 15thNight
39%8%15%24%9%2
2522
16th to endNight
36%7%14%23%15%2
2590
February1st to 15thNight
33%6%10%27%16%5%
2292
16th to endNight
27%5%13%23%22%7%
1887
March1st to 15thNight
29%6%13%26%20%2
2101
16th to endNight
29%6%13%27%18%4
2112
April1st to 15thNight
26%6%15%31%17%2
1976
16th to endNight
30%7%12%27%19%2
1857
May1st to 15thNight
20%6%15%33%19%3
1800
16th to endNight
39%8%15%25%9%
1723
June1st to 15thNight
53%10%20%11%3
1620
16th to endNight
38%15%33%12%
1620
July1st to 15thNight
35%15%34%13%
1530
16th to endNight
29%12%35%19%2
1595
August1st to 15thNight
33%13%30%21%1
1706
16th to endNight
41%14%28%15%
2101
September1st to 15thNight
45%15%28%10%1
1980
16th to endNight
51%13%21%11%2
1980
October1st to 15thNight
49%11%16%14%6%1
2052
16th to endNight
50%6%10%17%11%3
2304
November1st to 15thNight
36%7%11%24%18%1
2281
16th to endNight
37%8%11%17%20%4
2340
December1st to 15thNight
39%7%14%19%16%2
2425
16th to endNight
33%6%12%28%17%1
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%318%28%26%1
135
16th to endDay
14%420%39%17%3
144
February1st to 15thDay
15%40%37%5%
135
16th to endDay
6%114%35%38%3
279
March1st to 15thDay
9%114%44%28%1
312
16th to endDay
7%213%37%32%6%
288
April1st to 15thDay
47%38%44%4
270
16th to endDay
8%6%37%45%2
270
May1st to 15thDay
45%28%50%11%
288
16th to endDay
7%211%46%31%
331
June1st to 15thDay
16%412%30%35%
315
16th to endDay
7%6%25%59%
315
July1st to 15thDay
5%1230%58%
305
16th to endDay
7%1326%60%
326
August1st to 15thDay
7%2131%56%
313
16th to endDay
10%25%25%55%
332
September1st to 15thDay
12%3419%60%
315
16th to endDay
12%1422%57%
314
October1st to 15thDay
12%5%19%40%21%
315
16th to endDay
18%212%19%33%13%
336
November1st to 15thDay
9%19%25%39%13%
325
16th to endDay
10%18%33%33%5%
330
December1st to 15thDay
16%110%26%37%7%
242
16th to endDay
36%18%55%15%
144
January1st to 15thNight
10%315%30%36%4
780
16th to endNight
9%320%33%30%3
832
February1st to 15thNight
9%117%37%32%2
764
16th to endNight
5%212%37%37%4
683
March1st to 15thNight
5%14%41%35%3
764
16th to endNight
5%115%37%35%5%
768
April1st to 15thNight
5%8%39%42%4
718
16th to endNight
6%10%38%39%3
720
May1st to 15thNight
45%32%47%10%
720
16th to endNight
12%5%18%44%18%
602
June1st to 15thNight
16%415%33%30%
540
16th to endNight
5%28%34%49%
540
July1st to 15thNight
6%2436%50%
510
16th to endNight
33329%59%
564
August1st to 15thNight
5%1337%52%
597
16th to endNight
8%36%30%50%
764
September1st to 15thNight
10%26%29%50%
720
16th to endNight
13%36%28%47%
717
October1st to 15thNight
11%5%17%42%21%
720
16th to endNight
17%19%20%35%16%
768
November1st to 15thNight
10%111%29%37%9%
760
16th to endNight
11%111%33%36%6%
780
December1st to 15thNight
12%210%32%37%5%
780
16th to endNight
8%19%30%40%9%
832
Page generated at 2018-03-12 13:28:15. Version ac04

Copyright 2018 A. Danko


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