Mitten Lake Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mitten Lake Observatory clear sky chart from 2005-11-05 to 2017-10-31.

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
31%
16326
13%
47370
7%
16279
36%
16279
19%
33991

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
17%
900
8%
2506
2%
895
23%
895
12%
1999
January16th to endNight
16%
960
9%
2681
2%
960
22%
960
12%
2169
February1st to 15thNight
21%
880
12%
2288
3%
876
26%
876
15%
1769
February16th to endNight
23%
669
11%
1931
5%
669
28%
669
13%
1495
March1st to 15thNight
31%
702
15%
2142
9%
702
36%
702
20%
1466
March16th to endNight
34%
576
16%
2011
12%
576
41%
576
19%
1348
April1st to 15thNight
29%
539
14%
1797
10%
539
36%
539
18%
1243
April16th to endNight
31%
540
15%
1710
10%
540
38%
540
19%
1191
May1st to 15thNight
31%
540
12%
1440
6%
540
35%
540
18%
1089
May16th to endNight
39%
563
12%
1498
5%
561
44%
561
25%
1022
June1st to 15thNight
43%
540
9%
1440
4%
540
45%
540
27%
978
June16th to endNight
45%
540
11%
1440
5%
540
48%
540
29%
946
July1st to 15thNight
54%
510
12%
1360
6%
510
56%
510
40%
818
July16th to endNight
55%
564
17%
1417
9%
531
58%
531
40%
839
August1st to 15thNight
57%
539
22%
1467
15%
536
61%
536
34%
918
August16th to endNight
46%
573
18%
1872
16%
573
52%
573
27%
1141
September1st to 15thNight
53%
540
21%
1800
19%
540
61%
540
30%
1034
September16th to endNight
40%
664
17%
1936
11%
664
46%
664
29%
1231
October1st to 15thNight
33%
720
18%
2160
12%
720
39%
720
23%
1432
October16th to endNight
28%
768
11%
2431
6%
768
34%
768
14%
1815
November1st to 15thNight
24%
739
15%
2315
8%
739
32%
739
16%
1648
November16th to endNight
21%
900
11%
2520
7%
900
25%
900
12%
2035
December1st to 15thNight
14%
900
5%
2520
1%
900
17%
900
8%
2106
December16th to endNight
15%
960
9%
2688
2%
960
20%
960
9%
2259

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
15%9%47%6%35%45%6%31%
48388
Night
14%9%47%6%3445%6%33%
47537
Cloud CoverDay
27%8%36%5%34445%27%
48398
Night
26%8%36%5%24445%29%
47542
Cloud CoverDay
15%10%47%6%35%45%6%30%
48396
Night
14%10%47%6%3445%6%32%
47542
TransparencyDay
53%5%12%20%8%
48073
Night
51%5%12%20%9%
47370
SeeingDay
20%9%30%23%12%4
6295
Night
19%10%31%27%10%1
16326

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
13%11%8%12%9%6%5%45%6%16%
1432
16th to endDay
10%14%8%13%8%446%8%6%14%
1542
February1st to 15thDay
10%12%411%8%36%6%6%7%22%
1575
16th to endDay
14%11%5%12%7%45%45%5%21%
1542
March1st to 15thDay
12%11%49%8%35%347%29%
1817
16th to endDay
16%12%5%7%5%45%345%30%
2212
April1st to 15thDay
16%10%47%6%34435%32%
2151
16th to endDay
19%11%36%5%34445%30%
2247
May1st to 15thDay
20%9%37%43435%5%31%
2511
16th to endDay
13%7%36%6%345%5%8%34%
2617
June1st to 15thDay
18%6%35%5%245%5%7%35%
2520
16th to endDay
13%6%36%6%36%5%5%7%35%
2520
July1st to 15thDay
9%425%5%35%5%6%8%42%
2520
16th to endDay
10%435%6%25%5%6%8%42%
2655
August1st to 15thDay
11%6%25%5%36%5%5%8%40%
2481
16th to endDay
14%6%26%5%34448%38%
2330
September1st to 15thDay
12%7%24425%447%42%
2160
16th to endDay
18%8%36%5%24347%35%
2009
October1st to 15thDay
20%9%35%5%34446%34%
1800
16th to endDay
23%13%5%7%5%3435%5%24%
1791
November1st to 15thDay
16%13%5%7%5%2345%6%29%
1540
16th to endDay
15%15%8%10%6%5%5%45%5%17%
1440
December1st to 15thDay
15%15%7%12%10%45%46%413%
1440
16th to endDay
16%19%8%15%9%45%4338%
1536
January1st to 15thNight
13%9%7%11%7%46%45%7%21%
2506
16th to endNight
10%14%7%11%7%35%6%5%7%18%
2681
February1st to 15thNight
9%11%6%9%8%45%5%5%7%26%
2285
16th to endNight
10%13%6%9%7%45%5%5%6%23%
1931
March1st to 15thNight
13%9%46%5%3435%6%38%
2129
16th to endNight
13%10%36%5%245%5%5%37%
2011
April1st to 15thNight
22%8%35%423346%34%
1797
16th to endNight
21%8%35%5%15%45%6%32%
1710
May1st to 15thNight
21%9%46%5%35%446%29%
1440
16th to endNight
11%7%27%6%345%47%39%
1496
June1st to 15thNight
13%7%25%4245%5%8%40%
1440
16th to endNight
10%425%5%35%449%43%
1440
July1st to 15thNight
9%3143345%5%8%50%
1440
16th to endNight
7%32332446%9%51%
1513
August1st to 15thNight
8%4244345%5%8%49%
1476
16th to endNight
15%6%23413446%47%
1872
September1st to 15thNight
9%5%235%34446%50%
1800
16th to endNight
14%4235%2445%8%43%
1936
October1st to 15thNight
17%7%24424447%40%
2160
16th to endNight
18%12%26%5%35%5%5%6%27%
2431
November1st to 15thNight
15%12%46%424446%33%
2315
16th to endNight
17%13%5%9%7%445%45%21%
2520
December1st to 15thNight
13%14%7%12%9%46%45%5%17%
2520
16th to endNight
16%17%8%10%7%34445%16%
2688

Percentage Cloud Cover SW (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
25%9%5%10%8%5%5%35%5%15%
1432
16th to endDay
25%11%5%11%7%445%7%5%11%
1542
February1st to 15thDay
24%11%49%6%245%5%5%19%
1575
16th to endDay
28%9%49%7%34445%18%
1542
March1st to 15thDay
25%9%36%7%33345%27%
1827
16th to endDay
30%10%35%6%2333424%
2212
April1st to 15thDay
30%8%37%43334427%
2151
16th to endDay
33%10%35%42333424%
2247
May1st to 15thDay
31%8%26%333345%26%
2511
16th to endDay
28%6%25%5%23336%29%
2617
June1st to 15thDay
32%6%15%423445%29%
2520
16th to endDay
29%6%25%435%445%28%
2520
July1st to 15thDay
25%4145%3345%6%35%
2520
16th to endDay
25%32442345%6%36%
2655
August1st to 15thDay
19%425%5%35%5%47%36%
2481
16th to endDay
21%5%25%5%23448%36%
2330
September1st to 15thDay
19%7%24424346%39%
2160
16th to endDay
23%7%26%5%23346%33%
2009
October1st to 15thDay
27%8%24433435%32%
1800
16th to endDay
29%12%36%5%3324423%
1791
November1st to 15thDay
27%10%36%5%13336%27%
1540
16th to endDay
28%12%6%8%6%25%34416%
1440
December1st to 15thDay
28%12%5%10%8%3345%412%
1440
16th to endDay
28%16%6%13%9%35%4227%
1536
January1st to 15thNight
24%8%410%7%45%446%20%
2506
16th to endNight
24%12%5%10%5%345%5%6%16%
2681
February1st to 15thNight
24%10%47%7%34345%23%
2278
16th to endNight
23%11%48%6%445%4421%
1931
March1st to 15thNight
25%7%35%43334433%
2142
16th to endNight
27%8%25%41335%432%
2011
April1st to 15thNight
33%7%24423345%28%
1797
16th to endNight
35%7%24424345%26%
1710
May1st to 15thNight
34%7%26%424335%25%
1439
16th to endNight
27%6%25%5%23336%33%
1496
June1st to 15thNight
28%6%14414446%33%
1440
16th to endNight
26%415%423348%34%
1440
July1st to 15thNight
24%2133235%47%41%
1440
16th to endNight
23%313223347%43%
1513
August1st to 15thNight
16%313335%346%45%
1476
16th to endNight
23%5%13312345%44%
1872
September1st to 15thNight
17%323424446%44%
1800
16th to endNight
19%41343335%7%42%
1936
October1st to 15thNight
24%6%24413436%37%
2160
16th to endNight
25%10%26%43345%6%25%
2431
November1st to 15thNight
26%10%35%423335%31%
2315
16th to endNight
30%11%38%6%34435%19%
2520
December1st to 15thNight
27%13%5%9%8%3434414%
2520
16th to endNight
28%14%6%9%6%3444414%
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
12%12%7%13%9%5%6%446%16%
1432
16th to endDay
10%14%9%13%9%35%6%7%6%14%
1542
February1st to 15thDay
10%13%5%10%8%36%7%6%6%22%
1575
16th to endDay
14%11%6%11%7%5%6%45%5%20%
1542
March1st to 15thDay
12%11%6%8%7%34337%29%
1827
16th to endDay
15%12%47%5%34446%29%
2210
April1st to 15thDay
16%10%48%5%34345%32%
2151
16th to endDay
19%11%46%6%24345%30%
2247
May1st to 15thDay
19%10%36%5%2435%6%30%
2511
16th to endDay
14%7%37%6%345%5%8%34%
2617
June1st to 15thDay
18%7%245%3445%8%35%
2520
16th to endDay
13%6%35%6%36%5%6%7%35%
2520
July1st to 15thDay
9%426%5%3447%8%42%
2520
16th to endDay
10%4246%35%46%8%42%
2655
August1st to 15thDay
12%6%25%445%5%48%40%
2481
16th to endDay
14%6%26%5%2445%8%39%
2330
September1st to 15thDay
11%7%25%425%447%42%
2160
16th to endDay
18%8%36%5%23347%34%
2009
October1st to 15thDay
20%9%35%434345%34%
1800
16th to endDay
23%13%5%6%6%34345%23%
1791
November1st to 15thDay
16%14%47%6%2335%6%29%
1540
16th to endDay
15%16%7%12%8%35%346%16%
1440
December1st to 15thDay
15%15%6%13%9%37%45%5%13%
1440
16th to endDay
17%18%8%16%9%45%4338%
1536
January1st to 15thNight
13%10%6%12%7%45%45%7%20%
2506
16th to endNight
11%14%7%12%7%46%6%5%6%18%
2681
February1st to 15thNight
9%11%6%9%8%36%5%5%6%26%
2278
16th to endNight
11%13%6%9%7%45%5%5%6%23%
1931
March1st to 15thNight
13%8%47%5%34445%38%
2142
16th to endNight
13%10%46%5%2445%5%37%
2011
April1st to 15thNight
21%8%35%433446%34%
1797
16th to endNight
21%8%35%42445%6%33%
1710
May1st to 15thNight
22%8%37%434446%30%
1439
16th to endNight
11%6%36%5%35%5%5%7%39%
1496
June1st to 15thNight
13%7%25%4245%5%7%41%
1440
16th to endNight
11%425%6%25%5%49%42%
1440
July1st to 15thNight
8%4134245%6%7%50%
1440
16th to endNight
7%32432445%10%50%
1513
August1st to 15thNight
8%42443445%7%50%
1476
16th to endNight
16%6%14413346%47%
1872
September1st to 15thNight
9%5%24424346%50%
1800
16th to endNight
14%5%135%2345%7%43%
1936
October1st to 15thNight
17%7%24424448%39%
2160
16th to endNight
19%12%26%6%35%5%5%6%27%
2431
November1st to 15thNight
15%13%36%5%24346%33%
2315
16th to endNight
17%13%6%10%7%34445%20%
2520
December1st to 15thNight
14%15%6%11%9%36%45%5%16%
2520
16th to endNight
16%17%7%11%7%34445%16%
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
68%5%6%14%5%
1433
16th to endDay
66%6%11%10%4
1542
February1st to 15thDay
59%6%11%16%6%
1576
16th to endDay
64%5%9%15%5%
1542
March1st to 15thDay
55%315%16%8%
1827
16th to endDay
56%413%19%5%
2212
April1st to 15thDay
53%411%19%10%
2151
16th to endDay
56%410%18%10%1
2247
May1st to 15thDay
54%5%11%20%7%
2511
16th to endDay
47%5%11%20%12%1
2621
June1st to 15thDay
46%5%12%24%10%
2520
16th to endDay
45%7%15%21%9%
2520
July1st to 15thDay
36%6%11%29%13%1
2371
16th to endDay
38%6%13%25%14%1
2488
August1st to 15thDay
41%6%13%25%10%1
2466
16th to endDay
42%6%15%21%12%
2330
September1st to 15thDay
40%5%15%28%10%
2160
16th to endDay
49%6%13%24%7%
2009
October1st to 15thDay
51%412%22%8%
1800
16th to endDay
63%410%16%5%
1791
November1st to 15thDay
56%410%20%8%
1540
16th to endDay
69%5%10%10%4
1440
December1st to 15thDay
71%5%8%10%2
1440
16th to endDay
81%45%7%1
1536
January1st to 15thNight
62%6%10%16%4
2506
16th to endNight
63%6%10%14%4
2681
February1st to 15thNight
57%6%9%18%7%
2288
16th to endNight
60%5%11%16%6%
1931
March1st to 15thNight
46%6%12%21%12%
2142
16th to endNight
47%5%14%20%10%
2011
April1st to 15thNight
51%49%20%13%1
1797
16th to endNight
50%410%20%12%1
1710
May1st to 15thNight
55%5%11%19%8%
1440
16th to endNight
43%5%14%22%12%1
1498
June1st to 15thNight
41%6%13%26%11%
1440
16th to endNight
38%7%16%24%11%2
1440
July1st to 15thNight
29%5%15%33%14%1
1360
16th to endNight
29%5%16%31%14%2
1417
August1st to 15thNight
32%8%11%29%15%1
1467
16th to endNight
37%6%12%25%13%3
1872
September1st to 15thNight
34%5%12%34%13%
1800
16th to endNight
38%5%16%30%8%
1936
October1st to 15thNight
44%5%12%26%11%
2160
16th to endNight
56%6%13%16%7%
2431
November1st to 15thNight
52%5%12%20%9%
2315
16th to endNight
65%411%11%5%1
2520
December1st to 15thNight
69%5%10%11%2
2520
16th to endNight
70%48%12%3
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
21%10%33%27%7%
90
16th to endDay
30%10%30%23%5%
96
February1st to 15thDay
17%13%50%16%11
90
16th to endDay
30%6%46%12%3
81
March1st to 15thDay
18%16%32%21%11%
90
16th to endDay
26%7%31%20%9%4
196
April1st to 15thDay
21%11%27%27%10%1
270
16th to endDay
26%12%29%19%8%2
291
May1st to 15thDay
25%13%34%18%5%2
468
16th to endDay
21%12%31%18%10%4
517
June1st to 15thDay
21%10%28%24%12%2
495
16th to endDay
18%9%32%21%14%3
495
July1st to 15thDay
13%6%28%26%15%8%
475
16th to endDay
10%6%33%25%14%9%
515
August1st to 15thDay
15%6%22%30%19%5%
493
16th to endDay
20%5%21%26%19%5%
370
September1st to 15thDay
14%6%21%27%20%7%
315
16th to endDay
20%6%29%28%12%2
303
October1st to 15thDay
23%12%28%19%14%2
135
16th to endDay
31%13%34%14%5%
144
November1st to 15thDay
14%7%43%22%11%1
90
16th to endDay
35%8%27%23%31
90
December1st to 15thDay
20%448%24%2
90
16th to endDay
30%17%35%16%
96
January1st to 15thNight
18%12%39%21%7%
900
16th to endNight
18%12%41%22%41
960
February1st to 15thNight
17%11%39%24%6%
880
16th to endNight
18%12%37%24%6%
669
March1st to 15thNight
19%10%33%27%7%1
702
16th to endNight
18%10%32%26%9%2
576
April1st to 15thNight
26%7%30%28%6%
539
16th to endNight
25%8%30%27%7%
540
May1st to 15thNight
25%12%26%29%6%
540
16th to endNight
15%10%28%31%12%1
563
June1st to 15thNight
18%6%26%35%12%
540
16th to endNight
14%6%28%34%15%
540
July1st to 15thNight
10%327%35%20%1
510
16th to endNight
10%225%39%20%2
564
August1st to 15thNight
10%224%35%24%1
539
16th to endNight
19%324%29%20%2
573
September1st to 15thNight
13%5%22%33%21%3
540
16th to endNight
18%7%29%28%14%1
664
October1st to 15thNight
22%10%30%24%11%
720
16th to endNight
25%11%27%26%8%
768
November1st to 15thNight
23%13%33%21%7%
739
16th to endNight
26%14%31%22%5%
900
December1st to 15thNight
21%18%35%20%4
900
16th to endNight
24%12%35%21%5%1
960
Page generated at 2017-11-01 16:23:31. Version ac04

Copyright 2017 A. Danko


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