Country View Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Country View Observatory clear sky chart from 2005-11-05 to 2017-12-02.

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
50%
15880
24%
47846
16%
15837
58%
15837
29%
29366

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
27%
720
24%
2327
10%
716
45%
716
22%
1424
January16th to endNight
29%
768
24%
2454
12%
768
44%
768
22%
1521
February1st to 15thNight
33%
703
26%
2109
11%
700
48%
700
26%
1285
February16th to endNight
27%
631
26%
1893
10%
631
43%
631
26%
1165
March1st to 15thNight
34%
720
26%
2037
12%
720
46%
720
30%
1241
March16th to endNight
41%
768
23%
2112
13%
768
48%
768
31%
1287
April1st to 15thNight
44%
688
25%
1946
17%
688
51%
688
35%
1139
April16th to endNight
50%
540
29%
1689
18%
540
60%
540
36%
927
May1st to 15thNight
55%
539
23%
1620
15%
539
62%
539
33%
953
May16th to endNight
60%
561
22%
1682
17%
561
64%
561
32%
1031
June1st to 15thNight
67%
540
17%
1620
14%
540
69%
540
30%
1024
June16th to endNight
74%
540
16%
1620
15%
540
75%
540
32%
1006
July1st to 15thNight
72%
510
11%
1530
9%
510
73%
510
25%
1029
July16th to endNight
75%
564
14%
1595
13%
531
76%
531
28%
1057
August1st to 15thNight
71%
539
16%
1624
17%
536
71%
536
25%
1102
August16th to endNight
63%
588
17%
1925
18%
588
63%
588
22%
1294
September1st to 15thNight
65%
720
18%
1980
17%
720
66%
720
27%
1342
September16th to endNight
59%
717
24%
1980
19%
717
64%
717
29%
1288
October1st to 15thNight
56%
720
31%
2001
24%
720
63%
720
36%
1207
October16th to endNight
54%
768
36%
2304
27%
768
66%
768
38%
1250
November1st to 15thNight
54%
760
30%
2402
25%
760
64%
760
36%
1300
November16th to endNight
44%
780
29%
2535
20%
780
58%
780
31%
1413
December1st to 15thNight
38%
728
25%
2365
17%
728
50%
728
25%
1444
December16th to endNight
34%
768
22%
2496
15%
768
44%
768
20%
1637

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
12%5%25%5%35%5%5%7%42%
48590
Night
11%42442445%7%46%
48048
TransparencyDay
40%5%10%18%18%5%
48291
Night
36%5%10%19%20%8%
47851
SeeingDay
15%5%19%23%23%12%
5729
Night
14%7%21%29%22%4
15884

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
16%6%2341434447%
1611
16th to endDay
18%5%23424335%45%
1767
February1st to 15thDay
15%425%424446%45%
1750
16th to endDay
17%6%23423446%45%
1580
March1st to 15thDay
14%5%14424346%47%
1923
16th to endDay
14%5%24424445%46%
2111
April1st to 15thDay
12%425%424446%48%
2011
16th to endDay
10%4234335%5%6%51%
2268
May1st to 15thDay
10%425%43445%7%47%
2331
16th to endDay
9%415%6%46%5%5%8%41%
2431
June1st to 15thDay
10%5%25%6%46%6%7%10%34%
2340
16th to endDay
5%325%5%46%6%7%11%41%
2340
July1st to 15thDay
9%5%36%6%5%8%7%7%10%30%
2340
16th to endDay
7%437%7%5%8%9%9%10%26%
2465
August1st to 15thDay
11%6%25%7%47%6%8%10%28%
2322
16th to endDay
13%5%36%7%37%6%6%8%29%
2265
September1st to 15thDay
12%5%26%436%5%6%9%36%
1980
16th to endDay
15%5%25%6%3435%6%41%
1980
October1st to 15thDay
14%5%13312336%52%
1957
16th to endDay
11%4232333460%
1920
November1st to 15thDay
12%323323337%54%
1783
16th to endDay
13%425%423345%50%
1755
December1st to 15thDay
15%5%25%423446%45%
1632
16th to endDay
23%6%25%424235%37%
1728
January1st to 15thNight
16%5%24424345%47%
2327
16th to endNight
17%6%2432333446%
2454
February1st to 15thNight
15%424423246%48%
2103
16th to endNight
14%424423445%47%
1893
March1st to 15thNight
11%4245%23446%50%
2037
16th to endNight
13%5%13333347%50%
2112
April1st to 15thNight
13%323323439%50%
1946
16th to endNight
7%314424448%52%
1689
May1st to 15thNight
7%4243345%6%7%49%
1619
16th to endNight
8%4146%336%7%8%45%
1682
June1st to 15thNight
7%4245%45%5%7%10%41%
1620
16th to endNight
5%3245%36%5%9%13%39%
1620
July1st to 15thNight
8%3245%37%8%9%12%33%
1620
16th to endNight
5%3245%48%8%9%12%34%
1703
August1st to 15thNight
7%415%8%46%6%7%11%35%
1635
16th to endNight
12%5%25%6%36%5%6%11%34%
1925
September1st to 15thNight
8%5%25%5%46%5%7%8%38%
1980
16th to endNight
12%425%5%25%5%5%6%44%
1980
October1st to 15thNight
12%413323336%53%
2001
16th to endNight
9%313324345%58%
2304
November1st to 15thNight
10%413323246%56%
2402
16th to endNight
12%323423336%54%
2535
December1st to 15thNight
14%5%24423346%46%
2365
16th to endNight
20%6%25%424345%39%
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
40%38%15%26%5%
1612
16th to endDay
41%26%16%24%8%
1767
February1st to 15thDay
40%25%21%22%7%
1752
16th to endDay
40%35%18%24%7%
1580
March1st to 15thDay
38%48%19%20%9%
1923
16th to endDay
39%5%9%20%20%5%
2112
April1st to 15thDay
36%38%21%20%9%
2011
16th to endDay
32%5%9%20%24%7%
2268
May1st to 15thDay
36%412%19%21%4
2331
16th to endDay
38%6%12%24%14%2
2435
June1st to 15thDay
43%7%13%23%10%1
2340
16th to endDay
34%8%17%20%15%2
2340
July1st to 15thDay
45%8%19%16%6%2
2201
16th to endDay
45%10%15%19%7%1
2310
August1st to 15thDay
46%10%15%18%7%
2309
16th to endDay
51%7%15%13%10%1
2265
September1st to 15thDay
43%7%12%16%16%3
1980
16th to endDay
42%49%19%18%4
1980
October1st to 15thDay
34%38%20%25%7%
1957
16th to endDay
28%25%15%31%16%
1920
November1st to 15thDay
31%37%16%27%13%
1783
16th to endDay
36%36%15%27%9%
1755
December1st to 15thDay
40%49%18%18%8%
1632
16th to endDay
50%27%16%15%7%
1728
January1st to 15thNight
40%25%18%25%7%
2327
16th to endNight
42%25%16%22%11%
2454
February1st to 15thNight
39%2419%22%12%
2112
16th to endNight
38%36%18%23%10%
1893
March1st to 15thNight
35%38%19%21%10%
2037
16th to endNight
34%39%21%21%8%
2112
April1st to 15thNight
32%27%25%21%9%
1946
16th to endNight
29%411%21%21%11%
1689
May1st to 15thNight
32%5%14%19%22%5%
1620
16th to endNight
33%7%13%25%15%3
1684
June1st to 15thNight
35%8%17%25%12%
1620
16th to endNight
33%8%21%20%13%3
1620
July1st to 15thNight
37%12%21%18%6%3
1530
16th to endNight
35%12%22%18%8%2
1595
August1st to 15thNight
40%9%18%20%9%1
1624
16th to endNight
43%9%18%17%11%1
1925
September1st to 15thNight
40%9%14%15%17%4
1980
16th to endNight
39%6%10%18%19%5%
1980
October1st to 15thNight
33%47%18%25%10%
2001
16th to endNight
27%4415%32%16%
2304
November1st to 15thNight
29%37%16%28%14%
2402
16th to endNight
33%27%16%26%13%
2535
December1st to 15thNight
39%37%19%21%8%
2365
16th to endNight
47%37%17%17%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%16%37%13%10%2
90
16th to endDay
20%31%32%6%9%
96
February1st to 15thDay
22%20%38%15%3
90
16th to endDay
23%11%50%12%2
81
March1st to 15thDay
20%11%28%26%10%1
213
16th to endDay
13%9%33%25%17%
288
April1st to 15thDay
20%11%23%21%20%2
270
16th to endDay
13%324%30%22%5%
270
May1st to 15thDay
14%7%25%21%16%13%
288
16th to endDay
11%318%25%25%16%
331
June1st to 15thDay
13%110%22%28%22%
315
16th to endDay
7%111%28%25%26%
315
July1st to 15thDay
10%8%18%36%26%
305
16th to endDay
6%7%19%40%25%
326
August1st to 15thDay
16%7%23%32%19%
313
16th to endDay
13%7%25%33%19%
332
September1st to 15thDay
15%212%20%32%16%
315
16th to endDay
15%214%30%22%13%
314
October1st to 15thDay
21%321%21%22%9%
315
16th to endDay
10%8%19%31%22%7%
336
November1st to 15thDay
23%328%22%18%1
201
16th to endDay
10%8%28%37%13%2
135
December1st to 15thDay
20%13%32%21%11%
94
16th to endDay
40%9%23%18%6%1
96
January1st to 15thNight
20%15%30%23%9%
720
16th to endNight
21%14%29%28%5%
768
February1st to 15thNight
18%12%29%33%5%
704
16th to endNight
17%15%34%28%3
631
March1st to 15thNight
15%12%35%27%8%
720
16th to endNight
18%9%26%29%15%
768
April1st to 15thNight
15%10%27%29%16%
688
16th to endNight
10%5%27%34%20%2
540
May1st to 15thNight
10%424%33%24%2
540
16th to endNight
9%117%33%31%6%
563
June1st to 15thNight
9%12%35%33%8%
540
16th to endNight
6%7%32%40%12%
540
July1st to 15thNight
9%7%26%40%15%
510
16th to endNight
6%7%27%45%12%
564
August1st to 15thNight
9%6%27%45%10%
539
16th to endNight
14%16%24%41%11%
588
September1st to 15thNight
11%11%25%39%11%
720
16th to endNight
14%113%29%35%4
717
October1st to 15thNight
15%220%30%25%6%
720
16th to endNight
10%7%23%32%24%2
768
November1st to 15thNight
12%6%20%34%23%2
760
16th to endNight
13%10%26%30%17%1
780
December1st to 15thNight
16%10%28%28%14%1
728
16th to endNight
24%11%25%30%9%
768
Page generated at 2017-12-03 11:16:38. Version ac04

Copyright 2017 A. Danko


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