Lake MacDonald
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake MacDonald clear sky chart from 2005-11-05 to 2017-09-17.

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
26%
14612
13%
46840
7%
14580
33%
14580
15%
33849

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
13%
720
7%
2506
2%
716
19%
716
7%
2036
January16th to endNight
16%
768
10%
2688
4%
768
23%
768
10%
2026
February1st to 15thNight
14%
704
10%
2290
3%
701
23%
701
10%
1766
February16th to endNight
18%
631
12%
1919
5%
631
27%
631
12%
1462
March1st to 15thNight
16%
720
13%
2145
6%
720
25%
720
13%
1628
March16th to endNight
26%
768
20%
2001
8%
768
35%
768
22%
1396
April1st to 15thNight
22%
718
15%
1796
4%
718
27%
718
19%
1328
April16th to endNight
25%
636
16%
1716
5%
636
32%
636
20%
1210
May1st to 15thNight
27%
360
15%
1440
10%
360
39%
360
13%
989
May16th to endNight
30%
375
13%
1497
10%
374
42%
374
16%
981
June1st to 15thNight
26%
360
7%
1440
5%
360
34%
360
12%
1013
June16th to endNight
39%
360
9%
1440
11%
360
43%
360
16%
945
July1st to 15thNight
49%
340
12%
1360
16%
340
56%
340
24%
772
July16th to endNight
51%
376
13%
1418
15%
354
54%
354
22%
863
August1st to 15thNight
51%
381
13%
1452
12%
379
57%
379
20%
921
August16th to endNight
48%
738
19%
1884
10%
738
52%
738
34%
1189
September1st to 15thNight
44%
720
14%
1800
7%
720
46%
720
28%
1252
September16th to endNight
43%
665
20%
1807
12%
665
48%
665
29%
1181
October1st to 15thNight
29%
660
17%
1974
9%
660
39%
660
18%
1382
October16th to endNight
23%
704
11%
2238
6%
704
30%
704
13%
1683
November1st to 15thNight
25%
700
17%
2301
10%
700
35%
700
15%
1658
November16th to endNight
19%
720
11%
2520
7%
720
25%
720
9%
1952
December1st to 15thNight
14%
720
8%
2520
2%
720
21%
720
7%
2040
December16th to endNight
10%
768
10%
2688
3%
768
18%
768
6%
2176

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
19%10%46%5%34446%29%
47946
Night
18%10%46%5%24446%31%
47009
Cloud CoverDay
20%10%36%5%34446%30%
47955
Night
19%10%46%5%24346%31%
47015
TransparencyDay
54%5%11%18%9%1
47633
Night
53%5%11%19%9%1
46840
SeeingDay
26%14%28%19%8%2
5522
Night
24%13%28%23%8%
14612

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
22%18%5%9%7%35%34318%
1432
16th to endDay
14%17%6%7%7%35%45%423%
1536
February1st to 15thDay
13%15%5%11%8%34346%22%
1569
16th to endDay
16%16%6%8%6%3444424%
1554
March1st to 15thDay
17%13%5%9%5%3443426%
1802
16th to endDay
17%9%36%5%23445%37%
2222
April1st to 15thDay
23%12%35%323335%32%
2152
16th to endDay
21%9%36%433445%34%
2252
May1st to 15thDay
22%9%36%5%3435%6%29%
2511
16th to endDay
21%8%25%5%34346%31%
2618
June1st to 15thDay
22%8%36%5%35%45%7%26%
2520
16th to endDay
20%7%35%5%35%6%5%8%26%
2520
July1st to 15thDay
15%6%35%5%35%5%6%7%34%
2520
16th to endDay
15%6%36%6%46%5%6%8%30%
2654
August1st to 15thDay
15%7%36%6%46%5%5%7%31%
2496
16th to endDay
13%5%25%5%3445%8%39%
2306
September1st to 15thDay
19%6%2443435%6%38%
2160
16th to endDay
19%7%23323345%44%
1859
October1st to 15thDay
24%8%26%423446%32%
1656
16th to endDay
27%12%5%6%6%3344421%
1634
November1st to 15thDay
17%11%46%5%35%46%7%28%
1557
16th to endDay
26%12%46%434345%25%
1440
December1st to 15thDay
24%18%5%8%5%33335%17%
1440
16th to endDay
24%17%7%8%5%2342318%
1536
January1st to 15thNight
20%17%7%7%6%3334418%
2506
16th to endNight
12%16%6%9%6%3445%5%24%
2688
February1st to 15thNight
12%15%7%10%8%44345%23%
2288
16th to endNight
16%13%5%10%6%3444426%
1919
March1st to 15thNight
20%11%48%6%24335%27%
2132
16th to endNight
15%10%44423345%40%
2001
April1st to 15thNight
26%10%25%423335%34%
1796
16th to endNight
20%9%34423445%37%
1716
May1st to 15thNight
19%9%46%42443434%
1440
16th to endNight
19%7%35%42345%7%35%
1495
June1st to 15thNight
21%7%37%5%25%438%29%
1440
16th to endNight
17%7%24326%5%5%7%36%
1440
July1st to 15thNight
12%5%25%33446%8%44%
1440
16th to endNight
12%425%425%5%7%8%41%
1514
August1st to 15thNight
12%5%25%5%345%6%8%39%
1462
16th to endNight
11%4245%23448%47%
1884
September1st to 15thNight
16%6%245%34446%40%
1800
16th to endNight
20%5%13323345%47%
1807
October1st to 15thNight
19%7%36%5%3445%6%34%
1974
16th to endNight
26%10%46%5%22445%27%
2238
November1st to 15thNight
21%8%36%6%2335%6%31%
2301
16th to endNight
22%14%5%8%5%24345%24%
2520
December1st to 15thNight
22%17%5%8%6%34335%19%
2520
16th to endNight
23%18%5%7%6%2343320%
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
22%19%49%6%35%43318%
1432
16th to endDay
14%17%6%8%6%4444424%
1536
February1st to 15thDay
13%16%5%11%8%34445%22%
1569
16th to endDay
16%16%6%8%5%34435%24%
1554
March1st to 15thDay
18%13%5%9%7%2443426%
1812
16th to endDay
16%10%45%423345%37%
2221
April1st to 15thDay
24%10%35%423336%32%
2152
16th to endDay
22%8%35%5%24345%34%
2252
May1st to 15thDay
23%8%36%6%2435%5%29%
2511
16th to endDay
22%8%25%5%34346%31%
2618
June1st to 15thDay
23%8%36%5%3446%7%26%
2520
16th to endDay
21%7%26%5%36%5%5%8%26%
2520
July1st to 15thDay
16%6%35%5%35%5%6%7%34%
2520
16th to endDay
15%6%36%6%35%6%6%7%30%
2654
August1st to 15thDay
15%7%36%6%5%6%5%47%31%
2496
16th to endDay
13%5%26%5%245%48%40%
2306
September1st to 15thDay
20%6%25%424446%38%
2160
16th to endDay
19%5%24223336%44%
1859
October1st to 15thDay
25%8%25%423445%33%
1656
16th to endDay
27%11%38%7%3334422%
1634
November1st to 15thDay
17%10%38%5%345%5%6%29%
1557
16th to endDay
27%11%35%32444425%
1440
December1st to 15thDay
24%18%5%8%5%34325%18%
1440
16th to endDay
23%17%7%8%5%2343418%
1536
January1st to 15thNight
20%18%6%8%6%34345%18%
2506
16th to endNight
12%16%6%8%7%34346%25%
2688
February1st to 15thNight
12%15%6%10%8%44345%23%
2281
16th to endNight
16%12%6%9%6%2444426%
1919
March1st to 15thNight
20%11%47%6%34345%27%
2145
16th to endNight
15%10%45%423345%40%
2001
April1st to 15thNight
26%9%34314245%34%
1796
16th to endNight
21%7%24425%345%37%
1716
May1st to 15thNight
20%8%46%6%2344434%
1440
16th to endNight
20%7%35%42435%7%35%
1495
June1st to 15thNight
22%7%28%5%23437%29%
1440
16th to endNight
18%7%244345%5%7%36%
1440
July1st to 15thNight
12%425%42446%8%43%
1440
16th to endNight
12%424435%47%8%41%
1514
August1st to 15thNight
12%6%346%3446%8%39%
1462
16th to endNight
12%4235%23448%48%
1884
September1st to 15thNight
17%6%25%424446%41%
1800
16th to endNight
20%422324345%47%
1807
October1st to 15thNight
19%7%26%5%24447%34%
1974
16th to endNight
27%9%37%5%23346%28%
2238
November1st to 15thNight
21%8%35%6%34446%32%
2301
16th to endNight
22%14%46%6%23445%25%
2520
December1st to 15thNight
22%16%5%8%5%34345%20%
2520
16th to endNight
23%16%6%7%5%2434420%
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
69%6%6%11%5%
1433
16th to endDay
62%5%8%14%8%
1536
February1st to 15thDay
62%49%17%5%
1571
16th to endDay
62%47%14%9%1
1554
March1st to 15thDay
61%5%9%13%8%1
1812
16th to endDay
48%49%17%15%4
2222
April1st to 15thDay
54%28%18%11%2
2152
16th to endDay
52%47%18%13%4
2252
May1st to 15thDay
55%47%17%12%2
2511
16th to endDay
53%5%10%17%11%1
2622
June1st to 15thDay
55%6%11%16%9%
2520
16th to endDay
53%7%11%17%8%1
2520
July1st to 15thDay
43%7%13%24%10%
2371
16th to endDay
49%8%14%18%8%
2487
August1st to 15thDay
50%8%15%19%6%
2482
16th to endDay
41%6%16%25%10%
2306
September1st to 15thDay
44%5%13%24%11%
2160
16th to endDay
41%5%12%30%10%
1859
October1st to 15thDay
52%5%10%20%10%
1656
16th to endDay
65%5%11%12%5%
1634
November1st to 15thDay
52%8%14%15%8%
1557
16th to endDay
60%5%11%15%5%
1440
December1st to 15thDay
69%311%10%3
1440
16th to endDay
69%5%8%10%7%
1536
January1st to 15thNight
68%5%9%11%4
2506
16th to endNight
60%5%10%14%7%1
2688
February1st to 15thNight
62%410%17%5%
2290
16th to endNight
59%49%14%9%1
1919
March1st to 15thNight
59%49%16%9%1
2145
16th to endNight
46%411%18%16%3
2001
April1st to 15thNight
53%37%19%13%1
1796
16th to endNight
48%410%18%15%2
1716
May1st to 15thNight
52%5%6%17%13%4
1440
16th to endNight
46%7%9%21%13%1
1497
June1st to 15thNight
54%6%10%20%8%
1440
16th to endNight
45%8%10%21%13%
1440
July1st to 15thNight
35%6%15%27%13%
1360
16th to endNight
37%8%14%26%11%
1418
August1st to 15thNight
41%8%17%24%8%
1452
16th to endNight
33%6%17%31%10%
1884
September1st to 15thNight
43%6%13%25%11%
1800
16th to endNight
39%5%10%32%10%
1807
October1st to 15thNight
49%6%10%22%10%
1974
16th to endNight
57%5%13%16%7%
2238
November1st to 15thNight
53%6%12%17%8%1
2301
16th to endNight
62%6%9%15%5%
2520
December1st to 15thNight
67%6%9%13%3
2520
16th to endNight
67%5%8%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
31%23%23%16%5%
60
16th to endDay
34%17%37%6%4
64
February1st to 15thDay
41%23%29%5%
89
16th to endDay
27%26%27%15%3
213
March1st to 15thDay
27%20%31%17%3
270
16th to endDay
25%18%28%18%6%3
288
April1st to 15thDay
32%19%27%13%7%
270
16th to endDay
26%17%30%17%7%1
270
May1st to 15thDay
31%18%24%17%6%1
288
16th to endDay
29%13%30%19%6%
331
June1st to 15thDay
27%12%35%16%6%
315
16th to endDay
24%11%35%21%6%1
315
July1st to 15thDay
18%10%34%23%10%2
305
16th to endDay
16%7%31%30%11%2
326
August1st to 15thDay
19%6%28%30%10%4
313
16th to endDay
17%7%28%23%15%7%
332
September1st to 15thDay
22%7%24%22%16%6%
315
16th to endDay
21%13%22%20%14%7%
259
October1st to 15thDay
27%14%23%20%12%2
255
16th to endDay
35%15%24%18%6%
249
November1st to 15thDay
25%16%27%20%9%
211
16th to endDay
40%16%28%15%
60
December1st to 15thDay
40%18%26%15%
60
16th to endDay
46%23%26%3
64
January1st to 15thNight
30%16%31%17%4
720
16th to endNight
20%18%33%19%6%1
768
February1st to 15thNight
20%20%34%18%5%
704
16th to endNight
23%19%31%20%3
631
March1st to 15thNight
27%17%33%18%2
720
16th to endNight
21%16%30%22%7%1
768
April1st to 15thNight
30%14%27%23%3
718
16th to endNight
27%15%28%18%8%
636
May1st to 15thNight
24%9%34%23%6%1
360
16th to endNight
21%10%33%24%9%
375
June1st to 15thNight
25%9%30%28%5%
360
16th to endNight
22%326%33%12%1
360
July1st to 15thNight
12%6%26%34%17%1
340
16th to endNight
13%326%38%16%1
376
August1st to 15thNight
15%221%38%19%2
381
16th to endNight
15%5%24%32%20%1
738
September1st to 15thNight
20%5%24%32%15%
720
16th to endNight
21%8%23%26%17%2
665
October1st to 15thNight
23%14%26%25%9%
660
16th to endNight
33%12%25%21%6%
704
November1st to 15thNight
27%13%29%20%8%1
700
16th to endNight
29%18%25%16%8%
720
December1st to 15thNight
33%18%27%16%3
720
16th to endNight
33%19%28%13%3
768
Page generated at 2017-09-18 08:38:18. Version ac04

Copyright 2017 A. Danko


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