Caledon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Caledon clear sky chart from 2005-11-05 to 2017-11-30.

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%
15116
14%
47582
8%
15078
36%
15078
18%
32913

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
9%
719
8%
2461
2%
716
17%
716
7%
1937
January16th to endNight
15%
768
10%
2496
3%
768
23%
768
9%
1932
February1st to 15thNight
11%
701
10%
2287
1%
701
21%
701
10%
1735
February16th to endNight
14%
631
12%
2012
3%
631
25%
631
11%
1476
March1st to 15thNight
18%
720
13%
1980
5%
720
25%
720
14%
1470
March16th to endNight
25%
768
20%
2112
8%
768
36%
768
22%
1439
April1st to 15thNight
22%
718
14%
1829
4%
718
29%
718
20%
1333
April16th to endNight
30%
546
19%
1626
7%
546
40%
546
24%
1060
May1st to 15thNight
39%
504
17%
1584
11%
504
47%
504
23%
1044
May16th to endNight
40%
374
17%
1497
12%
374
54%
374
27%
822
June1st to 15thNight
40%
360
13%
1440
10%
360
51%
360
21%
834
June16th to endNight
48%
360
15%
1276
14%
360
56%
360
28%
730
July1st to 15thNight
56%
340
18%
1278
20%
340
64%
340
34%
655
July16th to endNight
52%
503
16%
1535
12%
471
57%
471
31%
892
August1st to 15thNight
57%
539
17%
1609
11%
536
62%
536
35%
933
August16th to endNight
52%
612
23%
1758
12%
612
59%
612
34%
1061
September1st to 15thNight
48%
720
20%
1827
9%
720
54%
720
35%
1165
September16th to endNight
50%
717
23%
1995
15%
717
54%
717
32%
1225
October1st to 15thNight
32%
720
17%
2160
12%
720
39%
720
22%
1460
October16th to endNight
18%
768
12%
2304
5%
768
28%
768
14%
1698
November1st to 15thNight
28%
760
16%
2580
13%
760
35%
760
16%
1773
November16th to endNight
20%
780
10%
2728
5%
780
27%
780
11%
2024
December1st to 15thNight
13%
720
6%
2520
2%
720
17%
720
8%
1990
December16th to endNight
9%
768
6%
2688
1%
768
14%
768
6%
2225

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
14%8%47%6%35%5%5%7%31%
48813
Night
13%8%36%6%3445%7%35%
47761
Cloud CoverDay
14%8%36%6%35%5%5%7%32%
48823
Night
14%7%36%5%3445%7%36%
47765
TransparencyDay
50%7%13%18%9%
48511
Night
47%7%13%20%10%1
47582
SeeingDay
17%15%30%21%10%4
5806
Night
18%15%31%23%9%1
15121

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
14%14%6%10%7%45%5%5%5%18%
1474
16th to endDay
10%15%8%12%8%45%5%5%5%16%
1728
February1st to 15thDay
12%14%6%12%9%45%45%5%19%
1575
16th to endDay
16%13%49%6%35%46%6%24%
1459
March1st to 15thDay
13%11%48%9%45%45%5%28%
1968
16th to endDay
13%9%47%6%345%45%34%
2112
April1st to 15thDay
18%10%35%6%34446%31%
2124
16th to endDay
17%9%36%423346%38%
2340
May1st to 15thDay
16%7%35%6%35%446%35%
2364
16th to endDay
11%5%36%5%35%5%5%8%39%
2618
June1st to 15thDay
14%6%25%5%245%6%8%37%
2520
16th to endDay
12%4246%36%5%8%10%36%
2679
July1st to 15thDay
8%425%5%46%6%6%9%38%
2601
16th to endDay
10%5%36%5%36%7%6%9%34%
2525
August1st to 15thDay
8%5%26%6%47%5%7%8%36%
2340
16th to endDay
10%6%26%5%46%6%6%9%34%
2432
September1st to 15thDay
13%6%36%6%35%448%37%
2132
16th to endDay
13%6%36%6%3445%7%37%
1965
October1st to 15thDay
19%8%37%6%35%446%32%
1800
16th to endDay
24%11%47%5%3445%5%22%
1920
November1st to 15thDay
13%10%5%6%6%35%5%6%7%30%
1603
16th to endDay
15%12%6%8%6%35%5%6%7%21%
1558
December1st to 15thDay
15%16%7%10%8%35%45%6%15%
1440
16th to endDay
19%14%6%9%7%36%47%5%14%
1536
January1st to 15thNight
18%12%5%8%6%45%5%5%6%20%
2461
16th to endNight
11%10%6%10%8%45%5%5%7%21%
2496
February1st to 15thNight
12%11%48%8%45%5%5%7%26%
2285
16th to endNight
11%10%5%9%7%45%45%6%27%
2012
March1st to 15thNight
16%8%47%6%35%447%31%
1968
16th to endNight
13%7%36%5%2444442%
2112
April1st to 15thNight
17%8%35%445%45%6%35%
1829
16th to endNight
11%7%35%6%3445%6%42%
1626
May1st to 15thNight
14%5%245%35%5%5%8%40%
1584
16th to endNight
11%424423447%49%
1495
June1st to 15thNight
11%4246%35%5%6%8%42%
1440
16th to endNight
8%4244345%6%8%48%
1276
July1st to 15thNight
5%213433447%57%
1356
16th to endNight
7%324435%5%5%9%48%
1641
August1st to 15thNight
6%4135%245%6%7%51%
1620
16th to endNight
8%4245%35%346%52%
1758
September1st to 15thNight
11%4135%2446%6%49%
1827
16th to endNight
12%5%1442335%7%49%
1995
October1st to 15thNight
17%6%35%5%2435%6%38%
2160
16th to endNight
18%8%37%7%345%5%7%28%
2304
November1st to 15thNight
16%7%35%6%345%5%7%33%
2580
16th to endNight
16%10%36%6%35%5%5%8%26%
2728
December1st to 15thNight
19%13%5%7%6%36%46%6%20%
2520
16th to endNight
19%13%7%10%8%35%5%5%5%14%
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
15%15%6%7%7%45%5%5%6%19%
1474
16th to endDay
11%16%7%10%10%45%45%6%16%
1728
February1st to 15thDay
13%14%6%12%7%36%446%19%
1575
16th to endDay
17%12%48%6%245%5%6%25%
1459
March1st to 15thDay
15%10%47%8%35%45%5%29%
1979
16th to endDay
13%9%47%5%35%45%435%
2111
April1st to 15thDay
18%10%36%5%35%45%6%31%
2124
16th to endDay
18%8%35%423336%39%
2340
May1st to 15thDay
17%6%25%6%35%5%46%36%
2364
16th to endDay
11%5%26%5%35%5%5%7%41%
2618
June1st to 15thDay
14%5%25%5%345%6%8%38%
2520
16th to endDay
12%5%245%45%5%6%10%37%
2679
July1st to 15thDay
9%425%5%45%5%6%9%40%
2601
16th to endDay
11%5%26%5%36%7%6%9%35%
2525
August1st to 15thDay
9%426%7%46%6%5%8%38%
2340
16th to endDay
12%5%25%5%45%6%6%9%36%
2432
September1st to 15thDay
13%7%25%5%4445%7%38%
2132
16th to endDay
14%5%36%5%3445%7%38%
1965
October1st to 15thDay
20%7%26%6%3345%5%33%
1800
16th to endDay
25%10%37%5%345%5%6%22%
1920
November1st to 15thDay
14%10%36%6%345%5%8%30%
1603
16th to endDay
16%12%6%8%6%25%5%5%7%22%
1558
December1st to 15thDay
16%16%7%10%8%36%445%17%
1440
16th to endDay
20%14%6%7%6%35%5%6%7%15%
1536
January1st to 15thNight
20%12%5%8%6%35%5%5%5%21%
2461
16th to endNight
12%11%7%9%7%45%45%6%23%
2496
February1st to 15thNight
13%11%5%8%7%45%5%5%6%27%
2278
16th to endNight
12%11%48%8%35%45%6%28%
2012
March1st to 15thNight
18%7%37%7%345%47%31%
1980
16th to endNight
13%8%35%5%24435%43%
2112
April1st to 15thNight
17%8%35%435%35%6%35%
1829
16th to endNight
12%7%35%5%2445%6%42%
1626
May1st to 15thNight
15%4245%345%5%7%40%
1583
16th to endNight
12%32442335%7%50%
1495
June1st to 15thNight
12%4146%345%5%9%42%
1440
16th to endNight
9%41442446%8%47%
1276
July1st to 15thNight
5%2134335%46%58%
1356
16th to endNight
7%314435%5%5%9%49%
1641
August1st to 15thNight
6%31442347%7%52%
1620
16th to endNight
9%324424446%52%
1758
September1st to 15thNight
11%42342446%6%49%
1827
16th to endNight
12%42442435%6%49%
1995
October1st to 15thNight
18%6%25%433446%39%
2160
16th to endNight
19%8%36%6%3446%7%29%
2304
November1st to 15thNight
16%8%35%5%35%46%7%34%
2580
16th to endNight
18%9%37%5%35%45%7%27%
2728
December1st to 15thNight
20%12%5%7%6%345%5%7%21%
2520
16th to endNight
20%13%8%10%7%45%445%15%
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%7%11%10%5%
1475
16th to endDay
67%7%10%9%4
1728
February1st to 15thDay
64%7%11%12%2
1577
16th to endDay
58%7%12%12%7%1
1459
March1st to 15thDay
56%6%13%15%7%
1979
16th to endDay
50%5%11%17%13%1
2112
April1st to 15thDay
52%5%10%19%10%
2124
16th to endDay
46%411%20%14%1
2340
May1st to 15thDay
48%6%10%21%12%
2364
16th to endDay
40%7%15%21%13%1
2622
June1st to 15thDay
41%7%14%23%12%
2520
16th to endDay
40%8%16%21%12%
2679
July1st to 15thDay
37%8%13%23%15%1
2450
16th to endDay
43%9%13%21%10%1
2369
August1st to 15thDay
41%9%15%18%12%1
2327
16th to endDay
40%8%15%23%9%1
2432
September1st to 15thDay
43%7%15%22%10%1
2132
16th to endDay
43%6%11%27%9%
1965
October1st to 15thDay
52%6%10%19%9%1
1800
16th to endDay
60%8%13%12%4
1920
November1st to 15thDay
50%8%15%17%7%
1603
16th to endDay
58%8%15%11%4
1558
December1st to 15thDay
67%8%12%9%1
1440
16th to endDay
66%10%11%8%2
1536
January1st to 15thNight
63%6%12%10%6%
2461
16th to endNight
60%7%14%13%4
2496
February1st to 15thNight
55%9%12%17%5%
2287
16th to endNight
55%6%14%15%7%
2012
March1st to 15thNight
53%6%12%19%7%
1980
16th to endNight
44%5%10%21%15%2
2112
April1st to 15thNight
48%6%11%18%14%
1829
16th to endNight
41%5%11%20%17%2
1626
May1st to 15thNight
41%7%10%23%15%1
1584
16th to endNight
33%5%15%27%14%3
1497
June1st to 15thNight
37%7%14%22%17%1
1440
16th to endNight
34%6%13%28%16%
1276
July1st to 15thNight
26%6%11%28%23%2
1278
16th to endNight
31%8%14%27%15%3
1535
August1st to 15thNight
28%8%19%28%13%1
1609
16th to endNight
32%6%10%31%17%1
1758
September1st to 15thNight
33%7%15%28%15%
1827
16th to endNight
34%5%13%33%12%
1995
October1st to 15thNight
44%6%11%22%13%
2160
16th to endNight
52%7%16%16%7%
2304
November1st to 15thNight
47%7%13%19%10%1
2580
16th to endNight
54%8%17%14%4
2728
December1st to 15thNight
61%8%15%11%3
2520
16th to endNight
69%6%12%9%2
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
19%34%32%8%4
67
16th to endDay
31%30%28%10%
96
February1st to 15thDay
20%40%32%7%
90
16th to endDay
24%34%34%6%
81
March1st to 15thDay
20%23%32%18%5%
269
16th to endDay
21%17%34%16%8%1
288
April1st to 15thDay
21%21%31%17%6%1
270
16th to endDay
21%22%26%15%9%4
270
May1st to 15thDay
21%12%30%19%10%5%
288
16th to endDay
12%12%35%23%10%3
331
June1st to 15thDay
15%15%30%25%10%1
315
16th to endDay
14%12%35%26%9%2
474
July1st to 15thDay
10%8%31%30%13%6%
384
16th to endDay
10%6%31%30%14%7%
326
August1st to 15thDay
9%5%26%29%18%10%
313
16th to endDay
13%7%23%25%18%12%
332
September1st to 15thDay
12%6%25%25%17%12%
315
16th to endDay
15%8%21%21%21%12%
314
October1st to 15thDay
22%13%30%15%12%4
315
16th to endDay
26%23%28%16%4
336
November1st to 15thDay
13%28%31%21%31
118
16th to endDay
20%26%41%8%3
90
December1st to 15thDay
18%43%25%10%3
60
16th to endDay
31%42%25%1
64
January1st to 15thNight
26%26%32%11%2
720
16th to endNight
16%19%38%19%5%
768
February1st to 15thNight
18%26%37%14%3
704
16th to endNight
19%21%38%17%3
631
March1st to 15thNight
22%23%32%19%2
720
16th to endNight
17%17%36%19%8%
768
April1st to 15thNight
21%17%35%21%3
718
16th to endNight
15%14%35%25%8%1
546
May1st to 15thNight
16%8%29%31%12%2
504
16th to endNight
13%6%34%29%15%
375
June1st to 15thNight
14%9%29%34%11%
360
16th to endNight
10%5%32%36%15%
360
July1st to 15thNight
6%328%40%20%1
340
16th to endNight
9%329%36%19%1
503
August1st to 15thNight
7%225%40%22%2
539
16th to endNight
12%326%28%25%3
612
September1st to 15thNight
13%7%25%26%21%5%
720
16th to endNight
14%8%20%29%20%5%
717
October1st to 15thNight
21%10%31%20%13%2
720
16th to endNight
24%19%33%19%3
768
November1st to 15thNight
19%16%30%22%8%1
760
16th to endNight
23%22%29%19%5%
780
December1st to 15thNight
27%24%31%14%2
720
16th to endNight
27%20%34%14%2
768
Page generated at 2017-12-01 12:13:47. Version ac04

Copyright 2017 A. Danko


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