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 2017-08-12.

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%
14586
14%
46516
8%
14555
37%
14555
17%
32530

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
14%
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
45%
384
18%
940
May16th to endNight
36%
374
15%
1497
12%
374
49%
374
22%
894
June1st to 15thNight
33%
360
11%
1440
8%
360
45%
360
17%
924
June16th to endNight
45%
360
10%
1440
12%
360
52%
360
21%
882
July1st to 15thNight
49%
340
15%
1360
21%
340
56%
340
29%
740
July16th to endNight
55%
376
15%
1418
16%
354
62%
354
28%
776
August1st to 15thNight
54%
506
16%
1555
11%
504
58%
504
31%
953
August16th to endNight
50%
626
21%
1676
10%
626
56%
626
36%
1021
September1st to 15thNight
45%
660
19%
1650
8%
660
50%
660
31%
1100
September16th to endNight
48%
657
22%
1812
14%
657
53%
657
29%
1177
October1st to 15thNight
34%
660
17%
1980
12%
660
41%
660
19%
1376
October16th to endNight
22%
704
11%
2153
5%
704
30%
704
12%
1646
November1st to 15thNight
29%
700
19%
2358
14%
700
38%
700
18%
1590
November16th to endNight
20%
720
13%
2520
7%
720
29%
720
10%
1890
December1st to 15thNight
15%
720
6%
2520
2%
720
20%
720
9%
1975
December16th to endNight
12%
768
8%
2688
2%
768
20%
768
8%
2154

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%3445%6%32%
47468
Night
17%9%36%5%34446%34%
46686
Cloud CoverDay
17%9%36%5%34446%32%
47478
Night
17%9%36%5%24446%34%
46691
TransparencyDay
51%6%11%19%10%1
47156
Night
49%6%11%20%10%
46516
SeeingDay
22%12%29%21%9%4
5293
Night
22%11%30%24%9%1
14587

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%5%5%9%36%
2306
16th to endDay
14%6%16%5%345%5%7%39%
2162
September1st to 15thDay
16%5%35%324447%41%
1980
16th to endDay
17%5%3442335%7%42%
1818
October1st to 15thDay
20%8%25%435%446%34%
1650
16th to endDay
27%10%36%5%24345%25%
1719
November1st to 15thDay
16%7%46%5%4445%6%34%
1497
16th to endDay
24%11%5%6%5%24346%25%
1440
December1st to 15thDay
21%14%5%8%5%34446%20%
1440
16th to endDay
22%16%7%7%6%3434421%
1536
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%1343446%7%47%
1565
16th to endNight
9%425%42345%8%50%
1676
September1st to 15thNight
14%6%2432345%7%45%
1650
16th to endNight
15%42342445%5%47%
1812
October1st to 15thNight
18%7%36%434446%36%
1980
16th to endNight
24%9%37%5%34445%26%
2153
November1st to 15thNight
16%8%45%434446%36%
2358
16th to endNight
22%10%37%435%446%26%
2520
December1st to 15thNight
22%13%46%6%3435%5%23%
2520
16th to endNight
23%14%6%8%6%25%33420%
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
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%
2306
16th to endDay
14%5%15%5%3446%7%39%
2162
September1st to 15thDay
16%5%34324446%42%
1980
16th to endDay
17%5%34323347%42%
1818
October1st to 15thDay
20%7%26%434446%34%
1650
16th to endDay
27%10%36%5%2335%5%25%
1719
November1st to 15thDay
16%8%36%5%35%46%5%34%
1497
16th to endDay
24%11%46%5%34345%25%
1440
December1st to 15thDay
21%13%5%7%5%33446%21%
1440
16th to endDay
23%15%6%7%6%3433421%
1536
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%135%25%46%7%47%
1565
16th to endNight
9%415%4235%48%50%
1676
September1st to 15thNight
15%5%2433345%6%45%
1650
16th to endNight
15%42442445%5%47%
1812
October1st to 15thNight
19%7%26%5%24446%36%
1980
16th to endNight
24%9%36%5%3445%5%26%
2153
November1st to 15thNight
17%9%34425%446%36%
2358
16th to endNight
23%10%37%5%24446%26%
2520
December1st to 15thNight
22%14%47%5%3435%5%23%
2520
16th to endNight
23%14%6%9%6%25%33420%
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
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%
2292
16th to endDay
41%7%14%26%9%
2162
September1st to 15thDay
41%6%12%26%11%
1980
16th to endDay
41%6%10%30%10%
1818
October1st to 15thDay
50%6%11%20%10%
1650
16th to endDay
60%412%16%5%
1719
November1st to 15thDay
49%7%12%18%10%
1497
16th to endDay
60%6%11%12%7%1
1440
December1st to 15thDay
63%7%13%11%3
1440
16th to endDay
67%5%8%12%6%
1536
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%
1555
16th to endNight
31%7%12%34%14%
1676
September1st to 15thNight
37%6%13%29%11%
1650
16th to endNight
37%7%10%31%12%
1812
October1st to 15thNight
48%6%11%21%11%
1980
16th to endNight
58%6%12%14%7%
2153
November1st to 15thNight
48%5%13%19%11%1
2358
16th to endNight
57%7%10%18%5%
2520
December1st to 15thNight
62%7%13%13%3
2520
16th to endNight
67%410%11%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
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%25%34%14%8%
297
16th to endDay
16%424%27%14%13%
268
September1st to 15thDay
17%8%23%22%17%11%
255
16th to endDay
20%8%24%25%9%11%
254
October1st to 15thDay
23%11%30%20%10%3
255
16th to endDay
33%16%25%21%2
265
November1st to 15thDay
25%5%29%28%9%1
151
16th to endDay
26%13%30%21%6%1
60
December1st to 15thDay
26%21%28%20%3
60
16th to endDay
40%28%26%4
64
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
12%224%33%23%3
506
16th to endNight
12%228%31%22%2
626
September1st to 15thNight
17%428%27%20%2
660
16th to endNight
17%7%23%28%20%2
657
October1st to 15thNight
25%10%26%23%13%1
660
16th to endNight
29%11%29%23%5%
704
November1st to 15thNight
22%10%32%23%10%1
700
16th to endNight
31%15%27%16%8%
720
December1st to 15thNight
31%17%30%18%2
720
16th to endNight
32%12%34%16%2
768
Page generated at 2017-08-13 14:16:45. Version ac04

Copyright 2017 A. Danko


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