Lennox and Addington Dark Sky Viewing Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lennox and Addington Dark Sky Viewing Area clear sky chart from 2005-11-05 to 2017-12-20.

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%
15099
14%
48083
8%
15068
37%
15068
18%
33527

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
8%
2506
2%
716
22%
716
7%
1983
January16th to endNight
18%
768
12%
2577
5%
768
26%
768
11%
1947
February1st to 15thNight
15%
704
11%
2287
3%
701
24%
701
12%
1734
February16th to endNight
20%
631
14%
1979
5%
631
32%
631
14%
1450
March1st to 15thNight
19%
720
15%
2048
6%
720
29%
720
16%
1506
March16th to endNight
29%
768
21%
2070
9%
768
37%
768
24%
1396
April1st to 15thNight
21%
718
16%
1796
5%
718
27%
718
19%
1303
April16th to endNight
31%
642
18%
1722
7%
642
38%
642
24%
1173
May1st to 15thNight
37%
384
17%
1464
15%
384
46%
384
18%
940
May16th to endNight
36%
374
15%
1497
12%
374
50%
374
22%
894
June1st to 15thNight
33%
360
11%
1440
8%
360
45%
360
17%
924
June16th to endNight
44%
360
10%
1440
12%
360
51%
360
21%
882
July1st to 15thNight
48%
340
15%
1360
21%
340
55%
340
29%
740
July16th to endNight
56%
376
15%
1418
16%
354
62%
354
28%
776
August1st to 15thNight
54%
518
16%
1589
11%
516
59%
516
31%
976
August16th to endNight
51%
683
23%
1829
10%
683
57%
683
37%
1102
September1st to 15thNight
47%
720
19%
1800
9%
720
52%
720
32%
1183
September16th to endNight
51%
717
24%
1977
16%
717
56%
717
30%
1264
October1st to 15thNight
35%
720
16%
2160
12%
720
41%
720
20%
1488
October16th to endNight
23%
768
13%
2349
6%
768
31%
768
13%
1761
November1st to 15thNight
30%
760
18%
2560
13%
760
38%
760
18%
1733
November16th to endNight
20%
780
13%
2730
7%
780
29%
780
10%
2032
December1st to 15thNight
14%
780
6%
2730
2%
780
20%
780
8%
2138
December16th to endNight
12%
788
9%
2755
2%
788
20%
788
8%
2202

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
17%9%36%5%34446%33%
48769
Night
17%9%36%5%24446%34%
48253
Cloud CoverDay
17%9%36%5%34446%33%
48779
Night
17%9%36%5%24446%34%
48258
TransparencyDay
50%6%11%19%10%1
48457
Night
49%6%11%20%10%1
48083
SeeingDay
22%12%28%21%9%4
5719
Night
22%11%30%24%10%1
15100

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%16%5%7%5%2433426%
1432
16th to endDay
14%15%6%10%7%4444323%
1647
February1st to 15thDay
13%15%49%9%45%5%4423%
1575
16th to endDay
18%13%6%7%6%35%33426%
1494
March1st to 15thDay
16%13%410%6%34445%26%
1900
16th to endDay
16%8%36%5%23335%40%
2154
April1st to 15thDay
22%11%45%424235%33%
2152
16th to endDay
19%8%35%422446%38%
2247
May1st to 15thDay
18%8%35%6%2445%7%33%
2487
16th to endDay
14%6%35%5%3445%7%38%
2618
June1st to 15thDay
22%6%25%5%35%46%8%29%
2520
16th to endDay
17%6%25%6%35%5%5%8%32%
2520
July1st to 15thDay
12%5%25%5%25%5%6%9%37%
2520
16th to endDay
10%6%36%6%37%5%7%8%34%
2654
August1st to 15thDay
11%6%35%6%35%6%5%9%36%
2358
16th to endDay
13%6%16%5%345%5%7%39%
2360
September1st to 15thDay
15%5%35%324447%43%
2160
16th to endDay
16%5%3442335%7%44%
1983
October1st to 15thDay
21%8%25%435%446%34%
1800
16th to endDay
26%10%36%5%34445%26%
1875
November1st to 15thDay
17%7%46%5%4445%6%33%
1625
16th to endDay
23%11%5%6%5%24346%26%
1560
December1st to 15thDay
20%14%5%8%5%34445%21%
1560
16th to endDay
22%16%7%7%6%3434421%
1568
January1st to 15thNight
21%13%5%9%7%35%435%21%
2506
16th to endNight
14%14%5%10%7%25%45%5%25%
2577
February1st to 15thNight
14%13%5%8%7%345%6%6%24%
2285
16th to endNight
16%12%46%5%345%46%29%
1979
March1st to 15thNight
19%10%46%5%34445%32%
2036
16th to endNight
15%7%35%5%23345%42%
2070
April1st to 15thNight
21%8%36%324445%35%
1796
16th to endNight
16%5%25%435%45%6%40%
1722
May1st to 15thNight
20%7%334235%48%37%
1464
16th to endNight
12%426%5%35%45%7%43%
1495
June1st to 15thNight
16%6%36%6%2445%8%36%
1440
16th to endNight
14%5%245%246%5%9%39%
1440
July1st to 15thNight
8%4245%15%5%5%8%48%
1440
16th to endNight
9%3243235%7%8%49%
1514
August1st to 15thNight
9%5%144345%6%7%46%
1599
16th to endNight
8%42442345%8%50%
1829
September1st to 15thNight
14%5%2432335%6%47%
1800
16th to endNight
14%42332345%5%49%
1977
October1st to 15thNight
18%7%26%424446%37%
2160
16th to endNight
23%9%36%5%34445%28%
2349
November1st to 15thNight
17%9%44434446%35%
2560
16th to endNight
22%10%37%435%446%27%
2730
December1st to 15thNight
21%14%5%6%6%3435%5%23%
2730
16th to endNight
22%14%6%8%6%2433420%
2755

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
20%16%47%6%2433426%
1432
16th to endDay
14%15%6%11%7%45%34423%
1647
February1st to 15thDay
13%14%5%10%9%35%435%23%
1575
16th to endDay
18%14%6%7%6%3443426%
1494
March1st to 15thDay
17%13%5%9%7%34445%26%
1911
16th to endDay
16%8%36%5%23335%40%
2153
April1st to 15thDay
22%11%35%423235%33%
2152
16th to endDay
19%8%35%423346%38%
2247
May1st to 15thDay
18%8%35%5%3445%6%33%
2487
16th to endDay
14%5%35%6%3445%7%38%
2618
June1st to 15thDay
22%6%35%435%46%8%30%
2520
16th to endDay
17%6%26%6%35%45%8%33%
2520
July1st to 15thDay
12%425%5%35%5%6%8%39%
2520
16th to endDay
11%6%27%5%36%6%7%8%34%
2654
August1st to 15thDay
11%6%25%6%45%5%5%9%36%
2358
16th to endDay
13%5%15%5%3446%7%40%
2360
September1st to 15thDay
15%5%34324446%43%
2160
16th to endDay
16%5%2432345%7%44%
1983
October1st to 15thDay
21%7%26%434446%34%
1800
16th to endDay
26%10%36%5%24445%25%
1875
November1st to 15thDay
17%8%36%5%35%46%5%33%
1625
16th to endDay
24%11%46%5%33346%26%
1560
December1st to 15thDay
21%14%6%7%5%335%46%21%
1560
16th to endDay
23%16%6%7%6%3433421%
1568
January1st to 15thNight
21%13%5%9%7%3444421%
2506
16th to endNight
14%14%5%9%7%35%45%426%
2577
February1st to 15thNight
15%13%5%7%7%35%5%5%6%25%
2278
16th to endNight
16%12%46%6%34445%29%
1979
March1st to 15thNight
20%10%46%5%24345%31%
2048
16th to endNight
16%7%36%5%23345%42%
2070
April1st to 15thNight
21%9%36%323445%35%
1796
16th to endNight
16%5%25%435%45%6%40%
1722
May1st to 15thNight
20%7%244235%48%37%
1464
16th to endNight
12%426%435%45%7%43%
1495
June1st to 15thNight
16%6%36%6%25%448%35%
1440
16th to endNight
14%5%245%246%6%8%39%
1440
July1st to 15thNight
8%4244245%6%7%48%
1440
16th to endNight
9%4233245%6%8%49%
1514
August1st to 15thNight
9%5%145%25%46%7%47%
1599
16th to endNight
9%415%4235%5%8%50%
1829
September1st to 15thNight
14%5%2433335%7%47%
1800
16th to endNight
14%32342445%5%48%
1977
October1st to 15thNight
18%7%25%5%24446%37%
2160
16th to endNight
23%8%36%5%3445%5%28%
2349
November1st to 15thNight
18%9%34425%446%36%
2560
16th to endNight
22%10%37%5%24446%27%
2730
December1st to 15thNight
21%15%47%5%34346%22%
2730
16th to endNight
23%14%6%9%6%25%33421%
2755

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
61%411%15%5%1
1433
16th to endDay
64%48%11%8%
1647
February1st to 15thDay
63%5%10%15%4
1577
16th to endDay
61%49%11%11%1
1494
March1st to 15thDay
59%412%15%6%1
1911
16th to endDay
48%37%20%14%4
2154
April1st to 15thDay
54%37%18%12%2
2152
16th to endDay
46%5%7%21%16%2
2247
May1st to 15thDay
50%5%10%18%12%2
2487
16th to endDay
44%7%13%20%12%2
2622
June1st to 15thDay
51%7%10%19%9%
2520
16th to endDay
48%7%12%19%12%1
2520
July1st to 15thDay
38%9%12%26%12%
2371
16th to endDay
45%8%14%22%8%
2487
August1st to 15thDay
43%8%15%21%10%
2344
16th to endDay
41%6%14%27%9%
2360
September1st to 15thDay
40%6%12%26%12%1
2160
16th to endDay
39%7%10%31%11%
1983
October1st to 15thDay
50%6%11%21%10%
1800
16th to endDay
59%413%16%5%
1875
November1st to 15thDay
50%7%12%18%10%
1625
16th to endDay
59%6%12%13%7%
1560
December1st to 15thDay
63%7%12%11%4
1560
16th to endDay
67%5%8%12%6%
1568
January1st to 15thNight
65%6%9%12%5%
2506
16th to endNight
58%6%9%15%8%
2577
February1st to 15thNight
58%7%12%16%5%
2287
16th to endNight
55%5%10%19%9%
1979
March1st to 15thNight
54%410%21%8%
2048
16th to endNight
44%49%21%17%2
2070
April1st to 15thNight
50%47%19%15%2
1796
16th to endNight
42%6%9%20%17%3
1722
May1st to 15thNight
45%5%10%19%15%3
1464
16th to endNight
39%6%13%22%16%2
1497
June1st to 15thNight
45%6%12%21%13%
1440
16th to endNight
40%7%15%22%13%
1440
July1st to 15thNight
30%7%13%28%19%1
1360
16th to endNight
31%7%15%29%14%
1418
August1st to 15thNight
33%8%16%27%13%
1589
16th to endNight
30%7%13%34%14%
1829
September1st to 15thNight
36%6%13%29%12%1
1800
16th to endNight
35%7%10%32%13%
1977
October1st to 15thNight
46%6%11%22%12%
2160
16th to endNight
56%6%12%16%7%
2349
November1st to 15thNight
48%5%13%19%11%1
2560
16th to endNight
56%7%11%18%5%
2730
December1st to 15thNight
62%6%12%13%4
2730
16th to endNight
67%49%11%6%
2755

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
25%30%23%16%5%
60
16th to endDay
31%14%36%15%2
83
February1st to 15thDay
32%28%35%3
90
16th to endDay
36%17%31%11%3
153
March1st to 15thDay
28%13%32%20%5%
270
16th to endDay
26%13%33%14%9%2
288
April1st to 15thDay
25%21%29%14%8%1
270
16th to endDay
23%18%28%14%10%4
270
May1st to 15thDay
29%12%25%17%8%5%
288
16th to endDay
18%15%35%18%9%3
331
June1st to 15thDay
25%10%30%22%9%1
315
16th to endDay
19%11%32%22%12%1
315
July1st to 15thDay
14%6%28%30%14%5%
305
16th to endDay
15%435%26%12%5%
326
August1st to 15thDay
11%6%24%34%15%8%
313
16th to endDay
15%6%24%26%14%12%
332
September1st to 15thDay
16%8%23%22%16%12%
315
16th to endDay
16%8%21%24%14%13%
314
October1st to 15thDay
25%11%29%19%9%4
315
16th to endDay
31%18%24%22%3
325
November1st to 15thDay
29%8%25%28%7%1
189
16th to endDay
26%21%31%15%41
90
December1st to 15thDay
30%22%24%17%41
90
16th to endDay
40%25%30%4
72
January1st to 15thNight
29%17%30%16%5%
720
16th to endNight
21%14%35%23%3
768
February1st to 15thNight
21%17%39%18%2
704
16th to endNight
23%16%35%20%4
631
March1st to 15thNight
26%15%33%22%2
720
16th to endNight
19%14%31%22%9%1
768
April1st to 15thNight
25%16%32%19%5%
718
16th to endNight
21%14%29%22%11%
642
May1st to 15thNight
25%6%26%30%9%1
384
16th to endNight
13%6%38%29%11%1
375
June1st to 15thNight
18%6%35%27%11%
360
16th to endNight
15%330%40%10%
360
July1st to 15thNight
9%230%37%19%1
340
16th to endNight
10%226%40%18%
376
August1st to 15thNight
11%224%34%23%3
518
16th to endNight
11%328%30%23%2
683
September1st to 15thNight
16%427%29%20%2
720
16th to endNight
16%6%21%27%22%4
717
October1st to 15thNight
24%9%26%23%14%1
720
16th to endNight
29%11%29%23%5%
768
November1st to 15thNight
23%10%31%23%10%1
760
16th to endNight
31%15%27%16%8%
780
December1st to 15thNight
31%17%30%18%2
780
16th to endNight
33%12%34%16%2
788
Page generated at 2017-12-21 07:04:49. Version ac04

Copyright 2017 A. Danko


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