Windy Hill 5 Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Windy Hill 5 Observatory clear sky chart from 2005-11-05 to 2017-09-24.

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
63%
15896
20%
47052
16%
15857
66%
15857
30%
29421

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
51%
717
17%
2327
14%
716
57%
716
24%
1474
January16th to endNight
48%
768
24%
2370
19%
768
55%
768
28%
1463
February1st to 15thNight
46%
701
24%
2105
17%
699
54%
699
32%
1283
February16th to endNight
54%
631
24%
1866
16%
631
62%
631
34%
1104
March1st to 15thNight
52%
720
29%
1980
15%
720
63%
720
43%
1102
March16th to endNight
60%
768
26%
2112
21%
768
63%
768
41%
1203
April1st to 15thNight
63%
718
22%
1976
17%
718
67%
718
45%
1087
April16th to endNight
62%
705
27%
1887
19%
705
67%
705
43%
1113
May1st to 15thNight
76%
539
28%
1619
24%
539
80%
539
46%
848
May16th to endNight
75%
561
24%
1683
21%
561
77%
561
38%
975
June1st to 15thNight
72%
540
11%
1620
9%
540
73%
540
26%
1094
June16th to endNight
79%
540
9%
1620
8%
540
79%
540
26%
1105
July1st to 15thNight
75%
510
6%
1530
6%
510
75%
510
20%
1128
July16th to endNight
79%
564
7%
1595
8%
531
80%
531
23%
1114
August1st to 15thNight
79%
539
4%
1708
5%
536
79%
536
24%
1174
August16th to endNight
71%
690
8%
2027
9%
690
71%
690
19%
1483
September1st to 15thNight
68%
720
7%
1980
7%
720
68%
720
18%
1479
September16th to endNight
65%
693
11%
1914
11%
693
66%
693
20%
1406
October1st to 15thNight
70%
660
25%
1831
23%
660
73%
660
34%
1127
October16th to endNight
56%
704
25%
2112
23%
704
62%
704
33%
1265
November1st to 15thNight
59%
700
29%
2101
25%
700
67%
700
38%
1191
November16th to endNight
53%
720
26%
2253
22%
720
60%
720
33%
1317
December1st to 15thNight
53%
720
23%
2340
21%
720
58%
720
27%
1423
December16th to endNight
57%
768
24%
2496
24%
768
61%
768
29%
1463

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
7%425%5%36%6%7%9%40%
47859
Night
6%425%5%35%5%6%10%43%
47258
TransparencyDay
36%10%17%18%13%4
47560
Night
33%9%17%19%14%4
47061
SeeingDay
9%213%23%28%22%
5760
Night
8%316%32%28%11%
15905

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
10%6%26%5%245%7%9%39%
1611
16th to endDay
10%4245%2445%7%47%
1851
February1st to 15thDay
10%5%2432446%6%48%
1750
16th to endDay
7%3245%2245%7%53%
1606
March1st to 15thDay
331332446%8%57%
1980
16th to endDay
8%31342345%9%53%
2111
April1st to 15thDay
5%2145%345%6%10%50%
1972
16th to endDay
6%2134245%5%8%54%
2082
May1st to 15thDay
32123235%6%10%56%
2331
16th to endDay
6%3235%36%6%7%10%43%
2431
June1st to 15thDay
9%6%25%5%37%6%9%11%30%
2340
16th to endDay
7%425%6%49%8%10%12%27%
2340
July1st to 15thDay
8%426%7%5%10%10%10%9%23%
2340
16th to endDay
6%5%37%8%5%8%10%10%12%21%
2465
August1st to 15thDay
6%426%8%5%9%9%11%13%22%
2237
16th to endDay
8%426%7%5%8%9%9%12%23%
2162
September1st to 15thDay
9%5%36%7%5%9%9%8%10%25%
1980
16th to endDay
7%5%37%8%47%7%8%11%26%
1905
October1st to 15thDay
5%326%6%45%5%7%9%42%
1796
16th to endDay
9%5%24425%448%48%
1760
November1st to 15thDay
5%415%5%35%46%8%50%
1757
16th to endDay
7%414435%447%50%
1704
December1st to 15thDay
8%5%36%445%46%8%42%
1620
16th to endDay
6%425%5%3445%9%48%
1728
January1st to 15thNight
9%6%25%6%46%5%6%9%38%
2327
16th to endNight
11%5%25%43446%8%43%
2370
February1st to 15thNight
10%7%25%414346%48%
2103
16th to endNight
6%424425%5%5%9%47%
1866
March1st to 15thNight
4213425%5%7%7%55%
1980
16th to endNight
5%414423448%54%
2112
April1st to 15thNight
5%2133235%6%9%55%
1976
16th to endNight
4313425%5%5%9%53%
1887
May1st to 15thNight
321332345%9%59%
1619
16th to endNight
43245%35%46%9%51%
1682
June1st to 15thNight
9%5%25%6%45%5%7%11%36%
1620
16th to endNight
5%4145%46%7%9%14%36%
1620
July1st to 15thNight
5%426%5%37%7%9%13%32%
1620
16th to endNight
4326%5%48%8%11%13%30%
1703
August1st to 15thNight
44245%36%8%10%14%35%
1719
16th to endNight
8%425%6%5%7%7%8%12%30%
2027
September1st to 15thNight
6%5%36%7%5%7%8%7%12%28%
1980
16th to endNight
8%5%37%8%5%7%6%7%11%28%
1914
October1st to 15thNight
5%4245%345%6%9%47%
1831
16th to endNight
9%5%245%2446%8%46%
2112
November1st to 15thNight
5%4245%24448%52%
2101
16th to endNight
7%4345%245%49%48%
2253
December1st to 15thNight
8%5%35%5%35%5%5%8%43%
2340
16th to endNight
6%4245%35%5%6%8%46%
2496

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
38%7%13%22%14%3
1612
16th to endDay
34%5%8%21%22%7%
1851
February1st to 15thDay
34%5%9%18%19%11%
1752
16th to endDay
28%6%13%17%23%9%
1606
March1st to 15thDay
23%5%13%28%21%7%
1980
16th to endDay
28%5%13%25%21%7%
2112
April1st to 15thDay
27%7%17%21%19%5%
1972
16th to endDay
26%6%14%22%25%4
2082
May1st to 15thDay
20%7%17%26%20%6%
2331
16th to endDay
32%9%17%24%14%1
2435
June1st to 15thDay
43%11%23%17%3
2340
16th to endDay
43%15%25%13%2
2340
July1st to 15thDay
48%19%23%5%2
2201
16th to endDay
46%19%23%10%
2310
August1st to 15thDay
43%21%28%7%
2224
16th to endDay
47%18%23%10%
2162
September1st to 15thDay
48%15%23%10%1
1980
16th to endDay
47%12%19%14%41
1905
October1st to 15thDay
35%9%11%17%17%7%
1796
16th to endDay
34%6%10%17%20%10%
1760
November1st to 15thDay
30%5%10%23%22%7%
1757
16th to endDay
32%6%11%19%17%11%
1704
December1st to 15thDay
38%5%14%20%16%4
1620
16th to endDay
33%5%14%21%19%5%
1728
January1st to 15thNight
41%6%13%23%12%3
2327
16th to endNight
37%5%10%19%19%7%
2370
February1st to 15thNight
35%47%18%21%12%
2112
16th to endNight
31%6%13%18%22%7%
1866
March1st to 15thNight
24%6%13%28%20%6%
1980
16th to endNight
27%5%13%24%20%7%
2112
April1st to 15thNight
23%6%19%25%19%5%
1976
16th to endNight
26%6%13%23%25%4
1887
May1st to 15thNight
21%6%15%29%20%6%
1620
16th to endNight
28%7%18%26%17%1
1684
June1st to 15thNight
40%9%24%19%5%
1620
16th to endNight
33%16%27%17%5%
1620
July1st to 15thNight
38%20%30%8%1
1530
16th to endNight
35%18%32%13%1
1595
August1st to 15thNight
32%19%37%10%
1708
16th to endNight
41%17%27%12%1
2027
September1st to 15thNight
44%16%24%12%2
1980
16th to endNight
44%13%21%14%41
1914
October1st to 15thNight
30%9%14%17%19%7%
1831
16th to endNight
34%411%15%23%9%
2112
November1st to 15thNight
29%5%11%22%22%9%
2101
16th to endNight
31%6%12%21%15%11%
2253
December1st to 15thNight
36%7%13%22%15%3
2340
16th to endNight
34%6%12%21%18%6%
2496

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%28%25%14%1
90
16th to endDay
11%15%34%30%6%2
96
February1st to 15thDay
7%15%28%27%16%3
90
16th to endDay
11%5%41%28%13%
107
March1st to 15thDay
5%5%37%31%18%2
270
16th to endDay
9%7%25%32%21%3
288
April1st to 15thDay
5%426%33%26%3
270
16th to endDay
7%214%41%27%7%
270
May1st to 15thDay
5%314%33%28%14%
288
16th to endDay
5%8%25%34%25%
331
June1st to 15thDay
17%25%18%29%26%
315
16th to endDay
6%49%33%45%
315
July1st to 15thDay
5%25%34%51%
305
16th to endDay
12%311%25%45%
326
August1st to 15thDay
10%36%30%48%
313
16th to endDay
10%49%34%41%
332
September1st to 15thDay
12%1413%33%33%
315
16th to endDay
9%216%42%28%
287
October1st to 15thDay
7%27%35%34%12%
255
16th to endDay
11%218%31%26%8%
272
November1st to 15thDay
6%315%33%35%6%
265
16th to endDay
9%227%36%20%3
174
December1st to 15thDay
12%332%40%12%
90
16th to endDay
47%18%39%26%4
96
January1st to 15thNight
11%6%22%37%20%1
720
16th to endNight
11%8%25%38%16%
768
February1st to 15thNight
14%5%27%35%15%
704
16th to endNight
8%5%25%42%17%
631
March1st to 15thNight
5%431%41%15%1
720
16th to endNight
7%322%45%19%2
768
April1st to 15thNight
5%5%20%45%22%1
718
16th to endNight
6%221%42%24%1
705
May1st to 15thNight
4111%43%34%4
540
16th to endNight
5%9%35%39%9%
563
June1st to 15thNight
11%219%47%18%
540
16th to endNight
6%311%40%37%
540
July1st to 15thNight
7%26%41%40%
510
16th to endNight
437%40%43%
564
August1st to 15thNight
5%27%39%44%
539
16th to endNight
10%315%38%31%
690
September1st to 15thNight
8%15%19%40%24%
720
16th to endNight
10%16%25%39%15%
693
October1st to 15thNight
8%10%38%35%7%
660
16th to endNight
10%220%33%28%4
704
November1st to 15thNight
5%323%39%26%2
700
16th to endNight
7%425%39%20%1
720
December1st to 15thNight
10%423%38%22%1
720
16th to endNight
7%421%39%23%2
768
Page generated at 2017-09-25 09:02:25. Version ac04

Copyright 2017 A. Danko


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