Wilder Skies Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wilder Skies 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
26%
14885
18%
46802
7%
14853
38%
14853
20%
30536

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
15%
720
19%
2506
5%
716
33%
716
15%
1616
January16th to endNight
14%
768
20%
2688
4%
768
34%
768
15%
1705
February1st to 15thNight
14%
704
16%
2194
4%
701
29%
701
16%
1477
February16th to endNight
16%
631
22%
1893
6%
631
36%
631
17%
1244
March1st to 15thNight
16%
720
17%
2160
6%
720
29%
720
15%
1501
March16th to endNight
20%
768
23%
2023
7%
768
33%
768
20%
1371
April1st to 15thNight
20%
718
18%
1796
3%
718
29%
718
20%
1284
April16th to endNight
21%
600
18%
1680
4%
600
31%
600
20%
1145
May1st to 15thNight
22%
540
15%
1620
6%
540
31%
540
17%
1124
May16th to endNight
27%
402
12%
1524
6%
401
36%
401
15%
1016
June1st to 15thNight
30%
360
12%
1440
8%
360
43%
360
15%
960
June16th to endNight
33%
360
12%
1440
11%
360
42%
360
20%
893
July1st to 15thNight
46%
340
12%
1360
13%
340
51%
340
21%
827
July16th to endNight
46%
376
15%
1418
14%
354
54%
354
22%
846
August1st to 15thNight
45%
494
16%
1565
11%
492
50%
492
26%
970
August16th to endNight
51%
735
21%
1881
10%
735
55%
735
35%
1212
September1st to 15thNight
38%
720
20%
1853
8%
720
45%
720
32%
1197
September16th to endNight
46%
657
26%
1815
16%
657
54%
657
35%
1100
October1st to 15thNight
31%
660
23%
1845
10%
660
43%
660
25%
1186
October16th to endNight
23%
704
16%
2285
5%
704
37%
704
19%
1502
November1st to 15thNight
29%
700
21%
2277
11%
700
44%
700
22%
1447
November16th to endNight
23%
720
20%
2340
8%
720
38%
720
18%
1505
December1st to 15thNight
20%
720
17%
2511
5%
720
35%
720
16%
1624
December16th to endNight
14%
768
19%
2688
4%
768
31%
768
15%
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
16%6%25%43445%6%39%
47937
Night
16%6%25%424446%41%
46972
Cloud CoverDay
17%5%2443445%6%39%
47947
Night
16%6%24424446%41%
46977
TransparencyDay
43%6%11%21%14%2
47625
Night
43%5%11%21%15%2
46802
SeeingDay
21%14%31%21%9%2
5863
Night
21%13%33%23%6%
14885

By Month

Percentage Cloud Cover NE (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
15%8%25%435%445%40%
1432
16th to endDay
14%5%245%24445%44%
1536
February1st to 15thDay
16%6%36%435%6%5%7%33%
1666
16th to endDay
14%8%36%5%24425%40%
1580
March1st to 15thDay
21%7%3442445%6%36%
1790
16th to endDay
17%7%34423346%41%
2198
April1st to 15thDay
17%7%35%6%24446%38%
2152
16th to endDay
17%424424447%41%
2280
May1st to 15thDay
24%8%35%434446%31%
2332
16th to endDay
16%5%35%425%36%7%38%
2601
June1st to 15thDay
24%5%2343346%7%33%
2520
16th to endDay
15%4246%45%6%6%8%34%
2520
July1st to 15thDay
11%5%26%5%35%6%5%8%37%
2520
16th to endDay
12%5%25%5%36%6%6%8%39%
2654
August1st to 15thDay
11%5%26%5%36%5%6%8%38%
2373
16th to endDay
10%5%25%5%35%5%5%7%44%
2320
September1st to 15thDay
13%6%234245%46%45%
2096
16th to endDay
13%5%24324245%51%
1815
October1st to 15thDay
20%424424446%41%
1783
16th to endDay
16%6%245%335%46%43%
1586
November1st to 15thDay
20%6%2332334344%
1581
16th to endDay
16%5%2442445%444%
1620
December1st to 15thDay
17%6%25%5%2335%5%40%
1446
16th to endDay
21%9%2442445%5%36%
1536
January1st to 15thNight
16%7%35%424436%41%
2506
16th to endNight
15%9%35%423346%40%
2688
February1st to 15thNight
14%8%36%5%3436%6%38%
2193
16th to endNight
15%8%25%423346%40%
1893
March1st to 15thNight
18%7%35%325%446%37%
2147
16th to endNight
13%8%45%42433445%
2023
April1st to 15thNight
16%6%26%5%3445%6%38%
1796
16th to endNight
20%5%25%5%23345%40%
1680
May1st to 15thNight
21%7%25%5%2345%5%36%
1620
16th to endNight
18%7%25%43445%8%35%
1522
June1st to 15thNight
22%6%3442435%8%35%
1440
16th to endNight
15%424425%5%5%7%40%
1440
July1st to 15thNight
12%5%146%25%5%5%8%41%
1440
16th to endNight
11%5%246%35%5%5%8%42%
1514
August1st to 15thNight
10%3236%35%6%5%8%44%
1575
16th to endNight
12%3143345%5%9%45%
1881
September1st to 15thNight
13%41442345%6%47%
1853
16th to endNight
13%413313347%52%
1815
October1st to 15thNight
20%42432235%5%45%
1845
16th to endNight
19%7%24324346%40%
2285
November1st to 15thNight
17%6%24423345%45%
2277
16th to endNight
18%6%24324445%41%
2340
December1st to 15thNight
18%7%24424346%40%
2511
16th to endNight
17%8%36%32345%5%38%
2688

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
15%8%26%425%345%41%
1432
16th to endDay
15%5%2443445%6%43%
1536
February1st to 15thDay
16%6%35%436%46%7%34%
1666
16th to endDay
14%8%36%5%34435%40%
1580
March1st to 15thDay
21%6%3442445%6%36%
1800
16th to endDay
18%6%34323436%41%
2198
April1st to 15thDay
17%7%35%5%24446%38%
2152
16th to endDay
18%4245%2445%6%41%
2280
May1st to 15thDay
25%7%25%424446%31%
2332
16th to endDay
17%425%5%2445%7%39%
2601
June1st to 15thDay
25%5%2443345%7%33%
2520
16th to endDay
15%425%6%46%6%6%7%34%
2520
July1st to 15thDay
12%5%25%5%46%5%5%8%37%
2520
16th to endDay
12%5%245%36%5%6%8%39%
2654
August1st to 15thDay
12%425%6%45%5%5%8%38%
2373
16th to endDay
11%425%435%5%5%6%45%
2320
September1st to 15thDay
14%5%144235%46%46%
2096
16th to endDay
13%5%24223335%51%
1815
October1st to 15thDay
20%424414446%41%
1783
16th to endDay
16%5%244235%46%43%
1586
November1st to 15thDay
21%6%2332334444%
1581
16th to endDay
17%5%2433445%444%
1620
December1st to 15thDay
17%6%35%5%2435%5%40%
1446
16th to endDay
22%7%244245%45%36%
1536
January1st to 15thNight
16%8%245%24336%40%
2506
16th to endNight
15%9%3442335%5%41%
2688
February1st to 15thNight
14%8%36%43435%5%38%
2186
16th to endNight
16%9%34424346%41%
1893
March1st to 15thNight
18%7%35%42445%6%37%
2160
16th to endNight
14%8%36%324335%44%
2022
April1st to 15thNight
16%7%26%6%3445%5%38%
1796
16th to endNight
20%5%25%5%23345%41%
1680
May1st to 15thNight
22%6%25%5%23345%37%
1620
16th to endNight
17%7%35%5%3345%7%36%
1522
June1st to 15thNight
23%6%24423347%35%
1440
16th to endNight
15%4245%26%5%5%7%40%
1440
July1st to 15thNight
13%4245%35%46%9%40%
1440
16th to endNight
11%435%6%35%5%48%42%
1514
August1st to 15thNight
10%3245%36%5%5%8%44%
1575
16th to endNight
13%31342446%8%46%
1881
September1st to 15thNight
14%41442435%6%47%
1853
16th to endNight
14%423213337%52%
1815
October1st to 15thNight
20%423322345%45%
1845
16th to endNight
20%7%24423346%40%
2285
November1st to 15thNight
17%6%2442335%445%
2277
16th to endNight
19%6%24424446%41%
2340
December1st to 15thNight
18%7%25%424436%40%
2511
16th to endNight
17%8%36%32345%6%37%
2688

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
44%5%10%24%11%3
1433
16th to endDay
39%5%13%24%14%1
1536
February1st to 15thDay
47%6%13%19%12%
1669
16th to endDay
46%5%8%21%14%3
1580
March1st to 15thDay
48%5%11%19%11%3
1800
16th to endDay
43%49%20%15%6%
2198
April1st to 15thDay
46%5%10%19%15%2
2152
16th to endDay
42%5%9%19%19%3
2280
May1st to 15thDay
53%5%7%18%12%2
2332
16th to endDay
44%6%12%21%12%2
2605
June1st to 15thDay
49%6%12%20%9%1
2520
16th to endDay
44%9%12%19%13%
2520
July1st to 15thDay
42%8%10%21%14%1
2371
16th to endDay
40%7%14%21%12%3
2487
August1st to 15thDay
41%7%14%22%12%1
2359
16th to endDay
37%6%11%27%16%2
2320
September1st to 15thDay
37%7%10%22%20%2
2096
16th to endDay
35%28%25%25%2
1815
October1st to 15thDay
43%5%8%23%14%3
1783
16th to endDay
40%6%12%23%15%1
1586
November1st to 15thDay
43%413%22%14%1
1581
16th to endDay
41%5%12%21%16%1
1620
December1st to 15thDay
44%5%15%17%16%
1446
16th to endDay
49%7%12%18%12%
1536
January1st to 15thNight
45%411%22%13%2
2506
16th to endNight
44%411%20%15%2
2688
February1st to 15thNight
45%5%13%20%11%2
2194
16th to endNight
44%49%22%15%2
1893
March1st to 15thNight
48%5%10%20%13%2
2160
16th to endNight
43%48%18%19%5%
2023
April1st to 15thNight
46%5%9%18%17%2
1796
16th to endNight
45%5%8%19%16%4
1680
May1st to 15thNight
48%5%10%18%14%2
1620
16th to endNight
46%8%13%18%11%1
1524
June1st to 15thNight
48%7%11%21%9%1
1440
16th to endNight
39%9%12%22%15%1
1440
July1st to 15thNight
38%8%12%25%13%
1360
16th to endNight
38%7%15%25%10%2
1418
August1st to 15thNight
36%8%13%22%16%1
1565
16th to endNight
33%7%12%27%18%
1881
September1st to 15thNight
36%5%12%24%19%1
1853
16th to endNight
33%46%25%27%2
1815
October1st to 15thNight
40%412%22%16%3
1845
16th to endNight
45%5%13%22%13%
2285
November1st to 15thNight
41%5%11%20%18%3
2277
16th to endNight
43%5%12%21%14%2
2340
December1st to 15thNight
45%5%13%22%12%
2511
16th to endNight
46%5%12%22%12%
2688

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%30%28%18%3
60
16th to endDay
28%18%42%10%
64
February1st to 15thDay
25%21%34%14%3
212
16th to endDay
22%23%32%15%5%
239
March1st to 15thDay
29%22%27%16%3
270
16th to endDay
23%24%30%13%6%1
288
April1st to 15thDay
25%16%35%12%8%
270
16th to endDay
21%16%35%17%5%2
270
May1st to 15thDay
35%14%26%15%6%1
288
16th to endDay
21%10%34%24%7%1
331
June1st to 15thDay
25%11%31%21%9%
315
16th to endDay
17%11%38%25%5%2
315
July1st to 15thDay
16%10%31%29%11%1
305
16th to endDay
12%7%31%30%12%4
326
August1st to 15thDay
11%9%32%29%14%2
313
16th to endDay
12%6%31%27%15%6%
332
September1st to 15thDay
18%8%31%23%12%5%
311
16th to endDay
15%8%25%24%13%12%
254
October1st to 15thDay
21%9%25%24%13%5%
255
16th to endDay
20%16%32%25%6%
240
November1st to 15thDay
26%11%29%20%9%2
235
16th to endDay
25%17%28%18%9%1
240
December1st to 15thDay
22%34%25%13%3
66
16th to endDay
34%26%26%10%1
64
January1st to 15thNight
22%18%38%17%1
720
16th to endNight
23%19%37%17%1
768
February1st to 15thNight
20%19%41%17%1
704
16th to endNight
23%21%34%17%2
631
March1st to 15thNight
24%19%36%17%2
720
16th to endNight
19%21%35%19%4
768
April1st to 15thNight
22%20%34%18%3
718
16th to endNight
22%17%35%18%6%
600
May1st to 15thNight
26%14%32%21%4
540
16th to endNight
21%9%37%26%5%
402
June1st to 15thNight
25%5%34%27%6%
360
16th to endNight
17%240%34%5%
360
July1st to 15thNight
13%430%40%10%
340
16th to endNight
11%331%39%13%
376
August1st to 15thNight
12%331%41%11%
494
16th to endNight
13%325%39%16%1
735
September1st to 15thNight
16%6%33%29%12%
720
16th to endNight
17%6%26%27%20%2
657
October1st to 15thNight
23%11%29%22%10%1
660
16th to endNight
26%14%32%19%6%
704
November1st to 15thNight
21%12%32%22%9%1
700
16th to endNight
24%17%29%19%7%1
720
December1st to 15thNight
25%17%33%19%4
720
16th to endNight
26%18%38%14%2
768
Page generated at 2017-09-16 00:58:32. Version ac04

Copyright 2017 A. Danko


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