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 2017-05-01.

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
49%
15147
24%
45649
16%
15104
57%
15104
28%
28040

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%
497
24%
1494
15%
497
63%
497
33%
881
May16th to endNight
60%
513
21%
1538
16%
513
64%
513
33%
942
June1st to 15thNight
67%
495
18%
1485
14%
495
69%
495
31%
933
June16th to endNight
76%
495
16%
1485
15%
495
77%
495
32%
909
July1st to 15thNight
70%
465
11%
1395
9%
465
71%
465
25%
941
July16th to endNight
75%
522
14%
1469
13%
489
76%
489
28%
966
August1st to 15thNight
72%
494
17%
1488
18%
491
72%
491
26%
997
August16th to endNight
62%
539
16%
1764
16%
539
63%
539
21%
1199
September1st to 15thNight
66%
660
19%
1815
17%
660
67%
660
25%
1245
September16th to endNight
56%
657
22%
1815
16%
657
61%
657
26%
1208
October1st to 15thNight
55%
660
31%
1834
25%
660
63%
660
36%
1112
October16th to endNight
54%
704
34%
2112
26%
704
65%
704
37%
1160
November1st to 15thNight
53%
700
31%
2212
26%
700
63%
700
36%
1185
November16th to endNight
43%
720
28%
2340
19%
720
57%
720
31%
1311
December1st to 15thNight
38%
720
25%
2340
17%
720
50%
720
25%
1425
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
13%5%245%35%5%5%7%42%
46099
Night
12%42443445%7%46%
45851
TransparencyDay
40%5%10%19%18%6%
45800
Night
36%5%10%19%20%8%
45654
SeeingDay
15%5%19%23%23%12%
4903
Night
14%7%21%29%22%4
15151

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%5%3445%7%45%
2138
16th to endDay
9%315%6%46%5%6%9%42%
2223
June1st to 15thDay
10%425%6%46%6%7%11%35%
2145
16th to endDay
42245%46%6%7%11%43%
2145
July1st to 15thDay
10%5%36%6%5%8%7%7%10%28%
2145
16th to endDay
7%437%7%5%9%9%9%10%25%
2283
August1st to 15thDay
10%5%247%47%7%8%11%30%
2129
16th to endDay
14%6%36%7%36%6%7%8%28%
2075
September1st to 15thDay
12%5%26%5%36%5%7%10%34%
1815
16th to endDay
16%6%26%6%3435%6%38%
1815
October1st to 15thDay
15%413322336%53%
1794
16th to endDay
11%41322334459%
1760
November1st to 15thDay
12%413323336%54%
1643
16th to endDay
14%424323345%50%
1620
December1st to 15thDay
15%5%25%423445%45%
1620
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%4143346%6%8%47%
1493
16th to endNight
8%415%5%335%7%8%45%
1538
June1st to 15thNight
7%4235%45%5%7%10%41%
1485
16th to endNight
43145%37%5%9%12%40%
1485
July1st to 15thNight
8%3245%47%8%9%12%32%
1485
16th to endNight
6%3245%47%8%9%13%34%
1577
August1st to 15thNight
7%415%8%46%5%7%11%36%
1499
16th to endNight
12%425%6%36%5%6%11%32%
1764
September1st to 15thNight
8%5%26%5%47%6%7%8%37%
1815
16th to endNight
13%5%25%5%35%5%5%6%42%
1815
October1st to 15thNight
13%413323336%52%
1834
16th to endNight
10%313324345%58%
2112
November1st to 15thNight
10%413323246%57%
2212
16th to endNight
13%323423335%54%
2340
December1st to 15thNight
15%5%24423346%46%
2340
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
37%5%13%20%19%4
2138
16th to endDay
37%6%12%25%14%2
2227
June1st to 15thDay
42%7%14%24%10%1
2145
16th to endDay
32%8%18%21%16%3
2145
July1st to 15thDay
47%8%18%15%6%3
2006
16th to endDay
46%10%16%18%6%
2128
August1st to 15thDay
44%10%16%19%8%1
2116
16th to endDay
52%7%15%13%10%1
2075
September1st to 15thDay
44%7%13%16%14%3
1815
16th to endDay
45%48%18%17%4
1815
October1st to 15thDay
34%38%20%25%8%
1794
16th to endDay
29%25%15%31%15%
1760
November1st to 15thDay
31%36%16%28%14%
1643
16th to endDay
37%26%16%26%9%
1620
December1st to 15thDay
40%48%18%18%8%
1620
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%15%19%21%5%
1494
16th to endNight
33%7%14%26%15%3
1540
June1st to 15thNight
34%8%17%25%13%
1485
16th to endNight
32%8%21%19%13%3
1485
July1st to 15thNight
39%11%21%18%6%3
1395
16th to endNight
35%11%23%18%8%1
1469
August1st to 15thNight
40%8%18%21%9%1
1488
16th to endNight
44%9%18%16%10%1
1764
September1st to 15thNight
41%9%14%15%15%3
1815
16th to endNight
41%6%9%17%17%6%
1815
October1st to 15thNight
33%48%17%25%10%
1834
16th to endNight
28%3415%31%16%
2112
November1st to 15thNight
29%26%16%29%15%
2212
16th to endNight
33%26%16%27%13%
2340
December1st to 15thNight
39%37%20%21%8%
2340
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
13%6%26%21%16%15%
229
16th to endDay
10%18%21%28%19%
267
June1st to 15thDay
12%111%22%29%21%
255
16th to endDay
317%27%28%30%
255
July1st to 15thDay
11%10%19%33%25%
245
16th to endDay
5%6%18%42%26%
270
August1st to 15thDay
16%6%22%33%20%
253
16th to endDay
15%5%22%35%20%
268
September1st to 15thDay
15%110%18%35%18%
255
16th to endDay
19%216%33%18%8%
254
October1st to 15thDay
22%320%23%23%7%
255
16th to endDay
11%6%17%30%25%8%
272
November1st to 15thDay
27%5%30%18%16%1
151
16th to endDay
12%10%27%33%12%4
90
December1st to 15thDay
21%14%32%22%10%
90
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%324%33%24%2
498
16th to endNight
10%117%32%32%6%
515
June1st to 15thNight
8%13%35%33%8%
495
16th to endNight
47%33%41%12%
495
July1st to 15thNight
10%7%29%38%13%
465
16th to endNight
6%7%27%45%12%
522
August1st to 15thNight
9%6%28%45%10%
494
16th to endNight
14%16%24%41%11%
539
September1st to 15thNight
11%10%24%40%12%
660
16th to endNight
16%114%31%31%3
657
October1st to 15thNight
16%220%29%26%5%
660
16th to endNight
10%7%22%32%24%2
704
November1st to 15thNight
12%7%21%34%22%2
700
16th to endNight
14%10%27%30%16%1
720
December1st to 15thNight
16%11%28%28%13%1
720
16th to endNight
24%11%25%30%9%
768
Page generated at 2017-05-02 08:43:26. Version ac04

Copyright 2017 A. Danko


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