Loon Call Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Loon Call Observatory clear sky chart from 2005-11-05 to 2017-09-21.

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
29%
14725
14%
46920
8%
14693
36%
14693
17%
33245

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
7%
2506
2%
716
21%
716
6%
2025
January16th to endNight
19%
768
12%
2559
5%
768
27%
768
11%
1979
February1st to 15thNight
15%
704
10%
2287
3%
701
23%
701
10%
1751
February16th to endNight
19%
631
14%
2002
5%
631
30%
631
13%
1459
March1st to 15thNight
18%
720
14%
2025
6%
720
26%
720
15%
1505
March16th to endNight
28%
768
21%
2087
10%
768
37%
768
24%
1408
April1st to 15thNight
23%
718
15%
1796
5%
718
28%
718
19%
1338
April16th to endNight
30%
611
18%
1691
8%
611
38%
611
23%
1166
May1st to 15thNight
37%
402
17%
1482
13%
402
46%
402
18%
961
May16th to endNight
38%
374
14%
1497
11%
374
50%
374
20%
906
June1st to 15thNight
35%
360
10%
1440
7%
360
47%
360
17%
917
June16th to endNight
46%
360
10%
1440
12%
360
51%
360
19%
902
July1st to 15thNight
51%
340
15%
1360
19%
340
57%
340
28%
739
July16th to endNight
49%
377
14%
1419
13%
355
58%
355
27%
794
August1st to 15thNight
55%
539
15%
1609
10%
536
59%
536
31%
997
August16th to endNight
52%
660
20%
1806
10%
660
58%
660
35%
1113
September1st to 15thNight
45%
720
17%
1800
8%
720
49%
720
31%
1201
September16th to endNight
47%
681
22%
1881
14%
681
52%
681
29%
1225
October1st to 15thNight
31%
660
17%
1980
11%
660
40%
660
18%
1415
October16th to endNight
20%
704
11%
2137
4%
704
29%
704
12%
1659
November1st to 15thNight
28%
700
17%
2388
14%
700
36%
700
16%
1645
November16th to endNight
20%
720
12%
2520
6%
720
27%
720
10%
1917
December1st to 15thNight
13%
720
6%
2520
2%
720
18%
720
7%
2029
December16th to endNight
11%
768
8%
2688
2%
768
17%
768
7%
2194

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
18%10%37%5%34446%30%
47952
Night
16%9%46%5%24446%32%
47091
Cloud CoverDay
18%9%46%5%34446%31%
47962
Night
17%9%46%5%3445%6%33%
47096
TransparencyDay
53%5%10%18%10%1
47641
Night
51%6%11%19%10%
46920
SeeingDay
23%11%30%19%10%4
5404
Night
22%12%30%23%10%1
14726

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
20%18%5%8%5%24335%22%
1432
16th to endDay
15%15%6%12%7%45%33420%
1664
February1st to 15thDay
14%15%5%12%8%34445%20%
1575
16th to endDay
16%16%6%7%6%3443426%
1470
March1st to 15thDay
16%12%48%7%44246%26%
1924
16th to endDay
14%10%46%5%24435%38%
2136
April1st to 15thDay
22%11%45%423335%31%
2152
16th to endDay
21%9%25%5%13336%37%
2280
May1st to 15thDay
20%8%45%5%34346%33%
2469
16th to endDay
15%6%35%5%345%5%7%36%
2618
June1st to 15thDay
22%8%26%5%45%45%7%29%
2520
16th to endDay
16%7%25%5%35%5%6%9%32%
2520
July1st to 15thDay
15%5%25%5%35%46%8%36%
2520
16th to endDay
11%6%26%5%46%5%6%9%33%
2651
August1st to 15thDay
12%6%37%6%46%6%5%7%32%
2340
16th to endDay
14%6%26%5%35%5%6%7%36%
2384
September1st to 15thDay
17%6%25%43435%7%39%
2160
16th to endDay
16%6%25%5%24347%41%
1869
October1st to 15thDay
22%8%35%6%34447%30%
1650
16th to endDay
30%11%26%6%23335%22%
1735
November1st to 15thDay
18%8%47%5%25%45%6%32%
1467
16th to endDay
23%15%6%7%5%3444421%
1440
December1st to 15thDay
20%20%7%10%6%33235%16%
1440
16th to endDay
22%18%7%9%6%2332419%
1536
January1st to 15thNight
20%15%6%9%7%2444418%
2506
16th to endNight
14%15%6%9%7%35%45%5%23%
2559
February1st to 15thNight
13%14%5%9%7%36%5%5%6%22%
2285
16th to endNight
14%14%36%6%35%5%5%6%28%
2002
March1st to 15thNight
18%10%48%6%2434431%
2013
16th to endNight
14%7%35%424445%41%
2087
April1st to 15thNight
20%8%45%5%24445%33%
1796
16th to endNight
17%7%245%24447%38%
1691
May1st to 15thNight
19%6%245%25%5%47%36%
1482
16th to endNight
12%4245%35%45%6%43%
1495
June1st to 15thNight
16%5%36%425%5%5%8%36%
1440
16th to endNight
12%5%246%46%5%48%38%
1440
July1st to 15thNight
8%4245%25%447%50%
1440
16th to endNight
9%4234245%5%9%47%
1515
August1st to 15thNight
8%5%244345%6%9%46%
1620
16th to endNight
8%425%425%45%8%49%
1806
September1st to 15thNight
14%425%32445%7%44%
1800
16th to endNight
18%42432335%5%47%
1881
October1st to 15thNight
20%7%26%6%34447%33%
1980
16th to endNight
24%10%46%5%245%5%6%23%
2137
November1st to 15thNight
17%9%36%5%25%45%6%33%
2388
16th to endNight
21%13%47%5%35%45%5%23%
2520
December1st to 15thNight
21%17%6%8%5%24445%18%
2520
16th to endNight
22%16%7%10%6%2343418%
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
21%17%6%7%43433422%
1432
16th to endDay
14%15%7%12%7%4443421%
1664
February1st to 15thDay
14%16%6%11%8%34445%20%
1575
16th to endDay
16%17%5%7%6%3433426%
1470
March1st to 15thDay
17%12%49%7%44346%26%
1935
16th to endDay
14%10%46%434345%38%
2135
April1st to 15thDay
23%11%45%423335%31%
2152
16th to endDay
21%9%35%423236%37%
2280
May1st to 15thDay
20%7%36%5%34446%32%
2469
16th to endDay
15%6%26%5%3445%8%36%
2618
June1st to 15thDay
22%7%36%5%35%447%29%
2520
16th to endDay
17%6%25%5%35%5%6%9%32%
2520
July1st to 15thDay
14%5%25%5%35%5%6%9%35%
2520
16th to endDay
12%5%36%6%35%5%7%8%33%
2651
August1st to 15thDay
13%6%26%7%36%6%5%7%32%
2340
16th to endDay
13%6%27%5%35%5%7%7%37%
2384
September1st to 15thDay
17%5%35%5%2345%6%40%
2160
16th to endDay
16%6%36%424247%41%
1869
October1st to 15thDay
22%8%26%5%24447%30%
1650
16th to endDay
30%11%35%5%33345%23%
1735
November1st to 15thDay
18%7%46%6%34445%33%
1467
16th to endDay
23%16%5%7%5%23445%21%
1440
December1st to 15thDay
20%19%7%10%7%3333417%
1440
16th to endDay
22%18%7%8%6%3333418%
1536
January1st to 15thNight
20%15%7%8%6%3434419%
2506
16th to endNight
14%14%6%9%7%3445%5%23%
2559
February1st to 15thNight
13%14%6%9%6%35%5%5%6%23%
2278
16th to endNight
15%13%47%6%345%5%5%28%
2002
March1st to 15thNight
18%11%46%7%3433431%
2025
16th to endNight
15%7%45%424445%41%
2087
April1st to 15thNight
20%9%35%5%34446%33%
1796
16th to endNight
17%7%25%43445%7%38%
1691
May1st to 15thNight
19%6%15%434447%37%
1482
16th to endNight
12%5%25%5%35%446%43%
1495
June1st to 15thNight
16%5%36%5%35%5%5%8%36%
1440
16th to endNight
13%5%245%36%5%5%8%38%
1440
July1st to 15thNight
9%2245%34448%49%
1440
16th to endNight
10%324325%46%9%48%
1515
August1st to 15thNight
9%5%145%3446%8%46%
1620
16th to endNight
9%32443445%7%49%
1806
September1st to 15thNight
14%5%2442446%7%44%
1800
16th to endNight
17%5%23323445%47%
1881
October1st to 15thNight
20%7%26%5%3435%6%33%
1980
16th to endNight
24%11%36%5%2445%6%24%
2137
November1st to 15thNight
18%9%35%6%3445%6%33%
2388
16th to endNight
22%12%46%5%44446%24%
2520
December1st to 15thNight
21%17%5%8%5%24445%19%
2520
16th to endNight
22%15%7%9%7%2343419%
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
65%5%9%12%7%
1433
16th to endDay
67%37%10%8%1
1664
February1st to 15thDay
66%6%9%12%5%
1577
16th to endDay
62%48%12%12%
1470
March1st to 15thDay
59%314%14%6%1
1935
16th to endDay
48%46%19%15%4
2136
April1st to 15thDay
56%37%17%12%2
2152
16th to endDay
49%37%21%15%2
2280
May1st to 15thDay
51%5%8%18%13%1
2469
16th to endDay
45%7%11%20%13%1
2622
June1st to 15thDay
54%6%9%19%9%
2520
16th to endDay
47%6%13%19%11%1
2520
July1st to 15thDay
41%7%11%26%12%
2371
16th to endDay
46%8%12%21%9%
2484
August1st to 15thDay
48%8%12%20%10%
2327
16th to endDay
43%6%13%25%9%
2384
September1st to 15thDay
43%7%10%25%12%
2160
16th to endDay
43%6%10%28%10%
1869
October1st to 15thDay
54%5%10%17%11%
1650
16th to endDay
64%5%9%13%5%
1735
November1st to 15thDay
52%5%12%18%9%1
1467
16th to endDay
64%6%9%11%6%1
1440
December1st to 15thDay
71%5%10%9%3
1440
16th to endDay
70%46%12%6%
1536
January1st to 15thNight
67%5%9%10%5%
2506
16th to endNight
61%5%7%14%9%
2559
February1st to 15thNight
61%5%12%13%6%
2287
16th to endNight
54%5%11%18%9%
2002
March1st to 15thNight
56%411%18%9%1
2025
16th to endNight
44%49%21%17%2
2087
April1st to 15thNight
52%46%19%13%2
1796
16th to endNight
44%6%9%20%16%2
1691
May1st to 15thNight
45%6%9%18%16%3
1482
16th to endNight
40%6%11%23%15%2
1497
June1st to 15thNight
44%6%13%21%13%
1440
16th to endNight
42%7%13%23%12%
1440
July1st to 15thNight
30%8%11%29%18%1
1360
16th to endNight
32%8%15%29%13%
1419
August1st to 15thNight
33%8%17%26%12%
1609
16th to endNight
32%7%14%31%13%
1806
September1st to 15thNight
37%6%16%25%12%
1800
16th to endNight
38%6%11%32%10%
1881
October1st to 15thNight
51%5%9%21%12%
1980
16th to endNight
59%6%11%14%7%
2137
November1st to 15thNight
49%6%13%19%10%
2388
16th to endNight
60%5%11%15%5%
2520
December1st to 15thNight
66%6%11%12%3
2520
16th to endNight
69%47%10%6%
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
35%18%25%18%3
60
16th to endDay
44%9%32%11%1
85
February1st to 15thDay
35%20%40%4
90
16th to endDay
38%13%34%11%2
129
March1st to 15thDay
26%15%33%20%4
270
16th to endDay
24%15%34%13%8%3
288
April1st to 15thDay
27%16%34%14%7%
270
16th to endDay
27%17%25%17%10%1
270
May1st to 15thDay
33%9%28%15%6%6%
288
16th to endDay
19%15%36%16%8%3
331
June1st to 15thDay
25%8%35%19%10%
315
16th to endDay
23%8%31%23%9%3
315
July1st to 15thDay
15%9%26%27%16%4
305
16th to endDay
13%9%31%24%14%5%
326
August1st to 15thDay
12%429%30%14%7%
313
16th to endDay
18%327%25%13%11%
332
September1st to 15thDay
14%7%27%19%17%12%
315
16th to endDay
19%8%23%24%14%10%
275
October1st to 15thDay
25%10%28%20%11%4
255
16th to endDay
38%13%27%15%5%
267
November1st to 15thDay
20%12%31%23%9%1
121
16th to endDay
35%20%28%13%3
60
December1st to 15thDay
30%26%23%18%1
60
16th to endDay
40%29%25%31
64
January1st to 15thNight
32%18%27%15%4
720
16th to endNight
22%14%34%22%41
768
February1st to 15thNight
22%18%36%19%2
704
16th to endNight
23%18%33%19%5%
631
March1st to 15thNight
27%16%32%19%3
720
16th to endNight
20%14%31%21%10%1
768
April1st to 15thNight
26%14%30%22%5%
718
16th to endNight
21%13%30%22%11%
611
May1st to 15thNight
22%8%26%26%13%
402
16th to endNight
14%7%35%29%12%
375
June1st to 15thNight
19%8%31%28%11%
360
16th to endNight
14%6%27%40%10%
360
July1st to 15thNight
7%429%39%17%1
340
16th to endNight
10%232%36%17%1
377
August1st to 15thNight
11%322%33%25%3
539
16th to endNight
10%426%30%24%3
660
September1st to 15thNight
15%5%28%27%18%3
720
16th to endNight
20%6%22%25%20%4
681
October1st to 15thNight
24%10%28%22%12%1
660
16th to endNight
31%14%28%19%6%
704
November1st to 15thNight
21%12%31%23%10%1
700
16th to endNight
30%14%26%19%7%1
720
December1st to 15thNight
30%19%31%14%3
720
16th to endNight
30%14%35%15%2
768
Page generated at 2017-09-22 07:35:31. Version ac04

Copyright 2017 A. Danko


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