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 2019-07-16.

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%
18326
20%
54266
17%
18287
67%
18287
31%
33694

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
52%
837
21%
2717
18%
836
58%
836
26%
1677
January16th to endNight
46%
896
24%
2765
19%
896
54%
896
28%
1709
February1st to 15thNight
49%
821
23%
2465
18%
819
56%
819
32%
1499
February16th to endNight
58%
735
25%
2174
18%
735
65%
735
36%
1252
March1st to 15thNight
53%
840
30%
2310
16%
840
63%
840
43%
1280
March16th to endNight
59%
896
27%
2464
20%
896
64%
896
42%
1390
April1st to 15thNight
63%
838
23%
2306
17%
838
67%
838
44%
1285
April16th to endNight
62%
814
27%
2178
19%
814
67%
814
45%
1255
May1st to 15thNight
75%
629
27%
1889
22%
629
78%
629
44%
1013
May16th to endNight
74%
657
23%
1971
20%
657
75%
657
37%
1157
June1st to 15thNight
74%
630
13%
1890
11%
630
75%
630
28%
1235
June16th to endNight
80%
630
9%
1890
8%
630
80%
630
26%
1284
July1st to 15thNight
75%
600
6%
1800
6%
600
75%
600
19%
1332
July16th to endNight
78%
615
7%
1748
8%
582
78%
582
21%
1240
August1st to 15thNight
79%
575
4%
1819
5%
572
79%
572
24%
1254
August16th to endNight
70%
748
8%
2197
8%
748
70%
748
19%
1617
September1st to 15thNight
68%
780
7%
2145
7%
780
68%
780
18%
1600
September16th to endNight
66%
777
12%
2145
12%
777
66%
777
20%
1564
October1st to 15thNight
69%
780
25%
2165
24%
780
72%
780
34%
1331
October16th to endNight
57%
832
26%
2496
24%
832
63%
832
34%
1471
November1st to 15thNight
61%
820
28%
2461
24%
820
68%
820
38%
1397
November16th to endNight
54%
840
26%
2629
22%
840
61%
840
33%
1535
December1st to 15thNight
54%
840
24%
2730
21%
840
60%
840
29%
1634
December16th to endNight
60%
896
24%
2912
25%
896
63%
896
30%
1683

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%41%
55031
Night
6%425%5%35%5%6%10%44%
54472
TransparencyDay
35%10%17%18%13%4
54732
Night
33%9%17%20%14%4
54275
SeeingDay
8%315%25%27%19%
8182
Night
8%316%32%28%11%
18335

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
9%6%25%4245%7%9%41%
1881
16th to endDay
9%425%5%2445%7%47%
2159
February1st to 15thDay
9%5%25%42446%7%46%
2050
16th to endDay
6%32442345%8%54%
1870
March1st to 15thDay
331332446%8%58%
2310
16th to endDay
8%31342345%8%54%
2463
April1st to 15thDay
5%2144245%6%10%51%
2302
16th to endDay
5%2134245%5%7%56%
2398
May1st to 15thDay
43134245%6%10%53%
2721
16th to endDay
7%4235%36%6%7%10%43%
2847
June1st to 15thDay
8%5%25%5%47%6%9%11%32%
2730
16th to endDay
6%425%6%48%8%10%12%30%
2730
July1st to 15thDay
8%427%7%5%9%10%10%10%23%
2730
16th to endDay
6%5%37%8%5%8%10%10%12%21%
2676
August1st to 15thDay
6%426%8%5%9%9%11%13%22%
2378
16th to endDay
8%426%7%5%8%9%9%12%24%
2343
September1st to 15thDay
8%426%7%5%9%9%8%11%26%
2145
16th to endDay
7%437%8%47%7%8%11%28%
2145
October1st to 15thDay
4426%7%45%6%7%9%41%
2122
16th to endDay
8%5%23425%448%49%
2080
November1st to 15thDay
4315%435%46%8%51%
2057
16th to endDay
7%424435%45%7%50%
1988
December1st to 15thDay
7%5%35%445%46%9%42%
1890
16th to endDay
6%415%5%3445%9%48%
2016
January1st to 15thNight
8%6%25%6%45%5%5%9%41%
2717
16th to endNight
11%5%25%43446%7%43%
2765
February1st to 15thNight
9%6%25%42435%7%47%
2463
16th to endNight
6%324425%5%5%9%48%
2174
March1st to 15thNight
42134245%6%8%55%
2310
16th to endNight
5%314423447%56%
2464
April1st to 15thNight
5%2134245%6%9%54%
2306
16th to endNight
42134245%5%9%55%
2178
May1st to 15thNight
321432445%9%57%
1889
16th to endNight
5%3245%35%46%8%50%
1970
June1st to 15thNight
8%5%245%45%5%7%12%38%
1890
16th to endNight
5%414446%7%9%14%36%
1890
July1st to 15thNight
5%5%26%5%37%7%9%13%32%
1890
16th to endNight
4326%6%48%8%11%13%29%
1856
August1st to 15thNight
44245%36%8%10%14%35%
1830
16th to endNight
7%426%6%5%7%7%9%12%29%
2197
September1st to 15thNight
6%5%36%8%5%7%8%7%12%29%
2145
16th to endNight
7%5%37%7%5%7%7%7%11%28%
2145
October1st to 15thNight
4425%5%345%6%9%47%
2165
16th to endNight
8%4245%2446%8%48%
2496
November1st to 15thNight
43245%245%48%52%
2461
16th to endNight
7%4345%245%5%9%48%
2629
December1st to 15thNight
8%4246%35%5%6%8%44%
2730
16th to endNight
6%4245%35%5%6%8%46%
2912

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%7%12%23%16%4
1882
16th to endDay
34%5%8%21%22%7%
2159
February1st to 15thDay
34%6%11%19%17%10%
2052
16th to endDay
27%6%14%19%24%8%
1870
March1st to 15thDay
22%5%14%27%21%8%
2310
16th to endDay
27%5%12%25%22%7%
2464
April1st to 15thDay
26%7%18%21%20%4
2302
16th to endDay
25%6%13%23%25%6%
2398
May1st to 15thDay
24%7%18%24%19%6%
2721
16th to endDay
33%9%15%22%16%1
2851
June1st to 15thDay
40%12%25%17%3
2730
16th to endDay
41%15%26%14%2
2730
July1st to 15thDay
47%19%25%5%1
2591
16th to endDay
46%19%23%10%
2521
August1st to 15thDay
42%21%28%6%
2365
16th to endDay
47%18%23%9%
2343
September1st to 15thDay
47%15%25%9%1
2145
16th to endDay
45%13%19%16%41
2145
October1st to 15thDay
36%10%11%18%17%6%
2122
16th to endDay
33%6%10%17%20%11%
2080
November1st to 15thDay
28%5%13%24%21%6%
2057
16th to endDay
32%6%11%20%18%10%
1988
December1st to 15thDay
37%5%13%21%16%4
1890
16th to endDay
31%6%15%24%17%5%
2016
January1st to 15thNight
38%5%12%23%15%3
2717
16th to endNight
37%5%9%20%19%6%
2765
February1st to 15thNight
34%5%10%18%19%10%
2472
16th to endNight
29%6%13%20%23%6%
2174
March1st to 15thNight
23%6%14%27%20%7%
2310
16th to endNight
26%5%12%25%22%7%
2464
April1st to 15thNight
24%6%19%25%19%4
2306
16th to endNight
24%6%13%24%26%5%
2178
May1st to 15thNight
22%6%16%27%20%6%
1890
16th to endNight
29%6%17%24%19%1
1972
June1st to 15thNight
37%9%27%21%5%
1890
16th to endNight
32%17%28%16%5%
1890
July1st to 15thNight
38%20%30%8%1
1800
16th to endNight
36%18%31%12%
1748
August1st to 15thNight
32%19%37%9%
1819
16th to endNight
41%17%27%12%1
2197
September1st to 15thNight
43%16%24%12%2
2145
16th to endNight
44%13%20%16%41
2145
October1st to 15thNight
30%9%15%20%18%6%
2165
16th to endNight
32%5%12%16%23%9%
2496
November1st to 15thNight
28%6%12%23%21%7%
2461
16th to endNight
31%6%12%21%16%10%
2629
December1st to 15thNight
34%7%13%24%16%3
2730
16th to endNight
32%6%13%24%16%5%
2912

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
15%10%31%28%12%1
180
16th to endDay
11%12%40%29%41
192
February1st to 15thDay
7%8%22%37%20%3
180
16th to endDay
7%330%34%21%2
189
March1st to 15thDay
45%38%33%16%1
390
16th to endDay
9%8%27%32%19%2
416
April1st to 15thDay
5%5%26%35%23%3
390
16th to endDay
6%317%40%26%5%
379
May1st to 15thDay
7%315%35%26%11%
408
16th to endDay
8%19%23%35%22%
459
June1st to 15thDay
14%15%23%30%25%
435
16th to endDay
6%310%36%42%
435
July1st to 15thDay
5%27%37%45%
425
16th to endDay
11%413%27%42%
391
August1st to 15thDay
9%38%32%45%
358
16th to endDay
10%39%33%43%
396
September1st to 15thDay
12%1415%33%34%
375
16th to endDay
7%216%41%31%
374
October1st to 15thDay
8%210%32%34%11%
375
16th to endDay
11%219%32%25%8%
400
November1st to 15thDay
4215%36%34%6%
385
16th to endDay
7%5%26%39%19%2
278
December1st to 15thDay
10%6%36%35%10%1
180
16th to endDay
5%5%21%38%25%4
192
January1st to 15thNight
11%5%22%37%20%1
840
16th to endNight
11%8%26%37%14%
896
February1st to 15thNight
13%426%36%17%
824
16th to endNight
8%422%42%20%
735
March1st to 15thNight
5%5%31%41%15%1
840
16th to endNight
7%323%44%19%1
896
April1st to 15thNight
5%421%43%23%1
838
16th to endNight
5%222%43%22%1
814
May1st to 15thNight
5%111%44%33%4
630
16th to endNight
6%9%35%38%9%
659
June1st to 15thNight
10%217%48%19%
630
16th to endNight
6%39%41%39%
630
July1st to 15thNight
7%37%41%40%
600
16th to endNight
437%40%43%
615
August1st to 15thNight
5%17%41%43%
575
16th to endNight
10%314%38%32%
748
September1st to 15thNight
7%15%18%41%25%
780
16th to endNight
10%6%24%41%16%
777
October1st to 15thNight
8%11%36%36%6%
780
16th to endNight
9%321%34%28%3
832
November1st to 15thNight
5%222%40%26%2
820
16th to endNight
7%425%41%18%1
840
December1st to 15thNight
9%424%38%22%1
840
16th to endNight
7%420%38%26%2
896
Page generated at 2019-07-17 08:53:10. Version ac04

Copyright 2019 A. Danko


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