Morehouse Lake Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Morehouse Lake Observatory clear sky chart from 2005-11-05 to 2018-03-11.

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%
15504
13%
49115
7%
15473
34%
15473
15%
35691

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
12%
780
9%
2716
4%
776
19%
776
7%
2189
January16th to endNight
13%
832
11%
2853
4%
832
22%
832
8%
2239
February1st to 15thNight
6%
764
8%
2479
1%
761
15%
761
5%
2051
February16th to endNight
13%
683
13%
2049
4%
683
23%
683
9%
1598
March1st to 15thNight
15%
764
12%
2266
5%
764
23%
764
12%
1737
March16th to endNight
23%
768
18%
2007
6%
768
32%
768
17%
1455
April1st to 15thNight
20%
718
14%
1796
2%
718
26%
718
17%
1361
April16th to endNight
26%
684
17%
1764
5%
684
34%
684
23%
1226
May1st to 15thNight
29%
408
17%
1488
11%
408
39%
408
16%
996
May16th to endNight
37%
374
14%
1497
12%
374
45%
374
17%
964
June1st to 15thNight
38%
360
11%
1440
10%
360
47%
360
16%
936
June16th to endNight
44%
360
11%
1440
11%
360
52%
360
21%
896
July1st to 15thNight
53%
340
11%
1360
16%
340
56%
340
21%
825
July16th to endNight
55%
376
15%
1418
17%
354
60%
354
24%
827
August1st to 15thNight
49%
452
14%
1523
10%
450
54%
450
24%
968
August16th to endNight
53%
764
19%
1910
10%
764
56%
764
36%
1219
September1st to 15thNight
46%
720
17%
1800
8%
720
49%
720
30%
1230
September16th to endNight
49%
717
25%
1950
17%
717
54%
717
33%
1231
October1st to 15thNight
31%
720
16%
2145
12%
720
37%
720
18%
1521
October16th to endNight
20%
768
11%
2409
6%
768
27%
768
11%
1851
November1st to 15thNight
23%
760
15%
2472
8%
760
33%
760
15%
1752
November16th to endNight
20%
780
15%
2691
10%
780
29%
780
11%
1973
December1st to 15thNight
14%
780
6%
2730
2%
780
18%
780
6%
2253
December16th to endNight
10%
832
8%
2912
2%
832
18%
832
5%
2393

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
18%11%5%7%6%34445%26%
49523
Night
16%11%5%8%6%34445%29%
49284
Cloud CoverDay
18%11%47%6%34446%27%
49532
Night
16%10%47%6%3445%6%29%
49290
TransparencyDay
57%410%17%9%
49210
Night
54%410%18%10%1
49115
SeeingDay
26%15%26%17%10%4
6139
Night
24%16%26%21%9%1
15505

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
16%17%8%10%7%35%44318%
1552
16th to endDay
11%15%8%13%10%45%44416%
1723
February1st to 15thDay
13%16%9%13%10%4434314%
1713
16th to endDay
17%14%8%11%8%3334421%
1710
March1st to 15thDay
15%16%8%11%6%3334421%
1920
16th to endDay
17%11%47%5%33435%33%
2217
April1st to 15thDay
21%12%6%7%42333430%
2152
16th to endDay
18%12%36%434445%31%
2196
May1st to 15thDay
23%10%46%5%23335%29%
2473
16th to endDay
21%7%36%6%3445%7%29%
2618
June1st to 15thDay
24%7%36%5%345%5%8%24%
2520
16th to endDay
21%8%26%6%35%5%6%7%25%
2520
July1st to 15thDay
17%7%45%5%35%6%6%6%29%
2520
16th to endDay
16%7%36%6%46%6%6%7%28%
2654
August1st to 15thDay
19%7%26%6%45%5%5%7%28%
2412
16th to endDay
14%7%25%6%45%5%7%7%32%
2292
September1st to 15thDay
19%6%26%434446%36%
2160
16th to endDay
17%6%26%423347%42%
2010
October1st to 15thDay
23%11%37%5%2433429%
1812
16th to endDay
25%16%46%5%3434322%
1813
November1st to 15thDay
17%15%36%5%34446%28%
1716
16th to endDay
19%14%6%8%6%23445%25%
1596
December1st to 15thDay
18%21%9%10%7%3433414%
1560
16th to endDay
19%19%10%12%6%3433413%
1664
January1st to 15thNight
16%15%8%11%7%35%44417%
2716
16th to endNight
12%14%8%11%8%44435%20%
2853
February1st to 15thNight
13%12%8%14%11%45%44415%
2477
16th to endNight
14%11%6%11%10%36%45%6%19%
2049
March1st to 15thNight
16%11%49%6%45%435%26%
2253
16th to endNight
15%10%5%7%5%34345%34%
2007
April1st to 15thNight
20%12%5%5%4335%46%28%
1796
16th to endNight
17%9%34424347%37%
1764
May1st to 15thNight
19%10%35%5%24335%35%
1488
16th to endNight
15%8%36%5%346%46%35%
1495
June1st to 15thNight
22%7%245%25%447%33%
1440
16th to endNight
17%5%25%4245%5%8%37%
1440
July1st to 15thNight
12%5%26%6%25%5%6%7%39%
1440
16th to endNight
11%5%244345%5%8%43%
1514
August1st to 15thNight
14%5%26%6%345%5%7%39%
1533
16th to endNight
13%5%235%3445%7%45%
1910
September1st to 15thNight
16%5%26%42445%5%41%
1800
16th to endNight
15%42432345%7%45%
1950
October1st to 15thNight
22%8%36%5%33345%34%
2145
16th to endNight
23%12%37%6%345%45%23%
2409
November1st to 15thNight
15%12%47%5%34445%30%
2472
16th to endNight
17%14%5%7%6%25%445%25%
2691
December1st to 15thNight
20%17%8%10%6%3435%414%
2730
16th to endNight
19%17%9%10%7%2443415%
2912

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%16%7%10%7%345%4418%
1552
16th to endDay
11%14%8%13%10%45%5%4416%
1723
February1st to 15thDay
13%15%9%12%10%5%443315%
1713
16th to endDay
16%14%7%11%8%3334421%
1710
March1st to 15thDay
16%15%7%12%6%34245%21%
1930
16th to endDay
17%10%47%433435%33%
2216
April1st to 15thDay
21%11%6%6%5%2333430%
2152
16th to endDay
18%12%36%434445%32%
2196
May1st to 15thDay
22%11%47%6%23345%30%
2473
16th to endDay
21%7%26%5%3445%8%29%
2618
June1st to 15thDay
24%7%36%5%345%6%8%24%
2520
16th to endDay
21%7%36%7%35%5%6%8%26%
2520
July1st to 15thDay
17%7%36%5%35%5%6%6%30%
2520
16th to endDay
16%6%36%7%36%5%6%7%29%
2654
August1st to 15thDay
18%7%35%6%45%5%6%7%28%
2412
16th to endDay
15%6%25%5%36%6%6%8%32%
2292
September1st to 15thDay
18%6%25%5%24446%36%
2160
16th to endDay
17%6%3442335%6%41%
2010
October1st to 15thDay
23%10%46%5%24335%30%
1812
16th to endDay
24%16%46%5%2434423%
1813
November1st to 15thDay
17%14%46%434446%29%
1716
16th to endDay
19%13%6%8%424445%25%
1596
December1st to 15thDay
18%20%8%10%7%3444415%
1560
16th to endDay
18%19%10%12%7%2333413%
1664
January1st to 15thNight
15%14%8%11%7%35%5%5%5%18%
2716
16th to endNight
12%13%8%11%8%45%445%21%
2853
February1st to 15thNight
11%12%8%14%11%46%5%5%416%
2470
16th to endNight
14%11%5%11%8%46%46%6%20%
2049
March1st to 15thNight
15%11%5%8%6%46%5%35%26%
2266
16th to endNight
15%10%47%6%24345%34%
2007
April1st to 15thNight
20%11%45%4335%5%5%29%
1796
16th to endNight
17%9%24424446%38%
1764
May1st to 15thNight
19%10%35%434235%35%
1488
16th to endNight
15%8%46%5%25%5%46%36%
1495
June1st to 15thNight
22%6%35%43435%7%34%
1440
16th to endNight
17%5%245%25%5%5%8%37%
1440
July1st to 15thNight
12%426%5%45%46%7%39%
1440
16th to endNight
12%5%24435%45%7%44%
1514
August1st to 15thNight
13%5%26%6%35%5%47%39%
1533
16th to endNight
13%42332346%6%46%
1910
September1st to 15thNight
16%4245%3445%6%42%
1800
16th to endNight
15%42432445%7%45%
1950
October1st to 15thNight
21%8%35%6%24345%33%
2145
16th to endNight
22%12%37%5%35%5%45%23%
2409
November1st to 15thNight
15%10%5%7%5%34446%31%
2472
16th to endNight
17%13%47%5%35%5%5%6%26%
2691
December1st to 15thNight
20%16%7%10%7%35%45%415%
2730
16th to endNight
18%17%8%9%6%35%445%16%
2912

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
67%46%11%7%1
1553
16th to endDay
70%5%5%10%6%1
1723
February1st to 15thDay
73%4411%5%
1715
16th to endDay
66%38%11%8%
1710
March1st to 15thDay
65%39%11%7%1
1930
16th to endDay
53%28%15%15%3
2217
April1st to 15thDay
57%37%19%10%1
2152
16th to endDay
53%37%20%12%2
2196
May1st to 15thDay
56%38%19%10%1
2473
16th to endDay
52%413%18%9%
2622
June1st to 15thDay
55%413%17%8%
2520
16th to endDay
54%412%18%8%
2520
July1st to 15thDay
50%411%24%8%
2371
16th to endDay
50%5%14%20%8%
2487
August1st to 15thDay
53%413%19%8%
2398
16th to endDay
45%413%24%11%
2292
September1st to 15thDay
47%49%25%12%
2160
16th to endDay
42%310%27%15%1
2010
October1st to 15thDay
57%37%19%10%1
1812
16th to endDay
63%410%15%5%
1813
November1st to 15thDay
54%6%10%16%10%1
1716
16th to endDay
59%411%13%9%
1596
December1st to 15thDay
71%49%9%4
1560
16th to endDay
75%36%8%5%
1664
January1st to 15thNight
66%5%7%9%8%1
2716
16th to endNight
64%5%6%14%8%1
2853
February1st to 15thNight
69%5%5%12%6%
2479
16th to endNight
62%47%14%8%1
2049
March1st to 15thNight
59%5%9%16%8%1
2266
16th to endNight
51%38%18%13%3
2007
April1st to 15thNight
54%5%8%19%10%
1796
16th to endNight
46%410%20%15%2
1764
May1st to 15thNight
51%39%19%14%1
1488
16th to endNight
47%5%12%21%11%1
1497
June1st to 15thNight
48%414%22%9%
1440
16th to endNight
42%5%16%24%10%
1440
July1st to 15thNight
41%5%13%26%11%1
1360
16th to endNight
38%5%16%27%11%1
1418
August1st to 15thNight
42%5%16%24%10%
1523
16th to endNight
34%5%16%31%12%
1910
September1st to 15thNight
41%5%12%26%12%1
1800
16th to endNight
37%310%29%17%1
1950
October1st to 15thNight
52%39%20%13%
2145
16th to endNight
60%6%11%14%6%
2409
November1st to 15thNight
53%411%15%12%2
2472
16th to endNight
57%5%8%18%9%
2691
December1st to 15thNight
70%5%9%10%4
2730
16th to endNight
70%5%6%10%6%
2912

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
35%14%34%12%3
90
16th to endDay
29%25%38%6%
110
February1st to 15thDay
39%34%22%2
138
16th to endDay
29%27%26%15%1
291
March1st to 15thDay
28%23%28%14%4
312
16th to endDay
27%26%21%13%8%2
288
April1st to 15thDay
33%19%21%17%7%1
270
16th to endDay
27%12%27%16%9%5%
270
May1st to 15thDay
35%12%24%13%9%5%
288
16th to endDay
23%15%30%17%12%2
331
June1st to 15thDay
28%13%29%18%9%1
315
16th to endDay
25%11%29%23%7%2
315
July1st to 15thDay
21%7%27%26%13%2
305
16th to endDay
18%7%29%30%11%3
326
August1st to 15thDay
21%9%23%21%15%7%
313
16th to endDay
16%8%23%21%15%13%
332
September1st to 15thDay
19%8%22%18%19%12%
315
16th to endDay
14%7%24%19%18%14%
314
October1st to 15thDay
27%9%24%20%14%3
315
16th to endDay
32%18%27%16%4
309
November1st to 15thDay
30%13%27%17%9%1
280
16th to endDay
34%23%23%15%3
126
December1st to 15thDay
34%25%28%7%3
90
16th to endDay
46%20%27%5%
96
January1st to 15thNight
30%22%28%14%3
780
16th to endNight
25%23%30%17%3
832
February1st to 15thNight
24%28%33%11%1
764
16th to endNight
24%25%31%15%3
683
March1st to 15thNight
28%21%31%16%2
764
16th to endNight
22%21%26%21%5%1
768
April1st to 15thNight
30%14%31%20%2
718
16th to endNight
25%15%29%19%8%1
684
May1st to 15thNight
27%9%26%25%9%1
408
16th to endNight
18%8%29%28%12%1
375
June1st to 15thNight
23%10%21%31%12%
360
16th to endNight
20%325%33%16%
360
July1st to 15thNight
13%5%17%40%22%1
340
16th to endNight
13%421%40%19%1
376
August1st to 15thNight
16%419%32%23%3
452
16th to endNight
15%420%32%24%3
764
September1st to 15thNight
19%7%21%29%20%2
720
16th to endNight
18%8%20%25%22%5%
717
October1st to 15thNight
26%14%21%23%13%1
720
16th to endNight
32%16%23%22%5%
768
November1st to 15thNight
23%16%30%19%8%1
760
16th to endNight
28%16%28%17%8%1
780
December1st to 15thNight
34%22%23%15%3
780
16th to endNight
33%26%23%12%2
832
Page generated at 2018-03-12 13:28:05. Version ac04

Copyright 2018 A. Danko


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