Mount Massive Lakes Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mount Massive Lakes Observatory clear sky chart from 2005-11-06 to 2024-01-13.

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
37%
24523
25%
74465
12%
24466
50%
24466
32%
40261

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 10thNight
27%
948
24%
2647
9%
946
41%
946
28%
1465
January11th to 20thNight
23%
776
29%
2414
10%
776
43%
776
28%
1239
January21st to endNight
23%
792
28%
2574
10%
792
45%
792
30%
1331
February1st to 10thNight
16%
720
23%
2340
6%
720
36%
720
24%
1261
February11th to 20thNight
19%
704
23%
2174
6%
700
38%
700
23%
1211
February21st to endNight
14%
592
27%
1776
5%
592
37%
592
25%
997
March1st to 10thNight
24%
720
26%
2094
8%
720
41%
720
29%
1135
March11th to 20thNight
30%
720
24%
1980
11%
720
40%
720
36%
1103
March21st to endNight
20%
715
22%
2101
5%
715
36%
715
27%
1201
April1st to 10thNight
24%
540
23%
1800
7%
540
43%
540
27%
925
April11th to 20thNight
25%
533
21%
1777
10%
533
39%
533
25%
990
April21st to endNight
28%
540
22%
1800
10%
540
44%
540
28%
978
May1st to 10thNight
31%
540
20%
1726
9%
540
46%
540
28%
988
May11th to 20thNight
43%
531
18%
1418
12%
531
49%
531
29%
918
May21st to endNight
47%
584
20%
1552
10%
582
56%
582
35%
907
June1st to 10thNight
54%
540
27%
1440
16%
540
62%
540
47%
764
June11th to 20thNight
50%
540
26%
1440
16%
540
58%
540
45%
774
June21st to endNight
63%
540
27%
1440
21%
540
68%
540
52%
744
July1st to 10thNight
67%
525
17%
1400
15%
525
69%
525
34%
869
July11th to 20thNight
75%
522
23%
1392
19%
522
77%
522
41%
799
July21st to endNight
68%
591
13%
1654
12%
558
69%
558
27%
1034
August1st to 10thNight
64%
537
14%
1602
13%
534
65%
534
28%
978
August11th to 20thNight
67%
534
23%
1723
22%
534
70%
534
34%
952
August21st to endNight
65%
594
22%
1980
22%
594
68%
594
31%
1131
September1st to 10thNight
68%
540
28%
1800
25%
540
75%
540
36%
963
September11th to 20thNight
59%
540
32%
1800
26%
540
68%
540
40%
910
September21st to endNight
55%
611
30%
2017
19%
611
66%
611
42%
990
October1st to 10thNight
39%
720
26%
2160
11%
720
52%
720
35%
1184
October11th to 20thNight
38%
720
35%
2160
14%
720
55%
720
45%
987
October21st to endNight
35%
792
33%
2376
14%
792
52%
792
37%
1241
November1st to 10thNight
30%
884
32%
2364
10%
884
46%
884
43%
1196
November11th to 20thNight
25%
950
33%
2470
10%
950
42%
950
40%
1256
November21st to endNight
33%
950
28%
2622
10%
950
47%
950
37%
1415
December1st to 10thNight
23%
950
24%
2660
6%
950
38%
950
31%
1430
December11th to 20thNight
21%
949
24%
3106
7%
949
36%
949
24%
1659
December21st to endNight
18%
1039
14%
4686
6%
1026
33%
1026
16%
2336

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
36%37%7%45%5%6%8%47%
74733
Night
2425%5%35%5%6%8%56%
75009
TransparencyDay
34%8%13%20%18%6%
74447
Night
23%9%16%25%21%6%
74818
SeeingDay
15%25%30%19%9%2
14328
Night
8%19%31%26%14%2
24532

By Month

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 10thDay
248%6%36%45%9%54%
1518
11th to 20thDay
237%7%46%5%5%6%55%
1607
21st to endDay
3411%8%4445%8%49%
1782
February1st to 10thDay
249%8%6%6%6%7%7%45%
1620
11th to 20thDay
349%7%5%5%46%8%48%
1672
21st to endDay
2412%9%5%6%5%5%6%47%
1480
March1st to 10thDay
6%5%9%8%5%5%45%8%47%
1862
11th to 20thDay
16%49%7%35%5%6%8%46%
1980
21st to endDay
16%6%10%7%46%6%6%8%41%
2254
April1st to 10thDay
16%47%8%45%5%6%7%47%
2160
11th to 20thDay
18%5%11%8%46%5%6%6%39%
2131
21st to endDay
29%5%8%8%5%7%5%6%8%38%
2160
May1st to 10thDay
39%5%8%8%46%6%7%8%37%
2227
11th to 20thDay
411%48%6%46%7%6%8%36%
2478
21st to endDay
5%9%47%6%5%6%6%7%8%39%
2724
June1st to 10thDay
35%26%6%45%5%7%9%48%
2520
11th to 20thDay
5%5%25%6%35%46%7%55%
2520
21st to endDay
4425%7%45%5%6%8%50%
2520
July1st to 10thDay
7%7%37%6%45%5%6%7%42%
2520
11th to 20thDay
7%5%47%8%47%6%8%8%37%
2520
21st to endDay
12%8%48%10%47%6%6%8%27%
2563
August1st to 10thDay
11%8%38%8%5%6%6%6%7%31%
2328
11th to 20thDay
8%6%36%7%45%5%6%8%42%
2175
21st to endDay
8%7%48%8%46%6%6%7%37%
2376
September1st to 10thDay
7%6%36%6%35%5%5%7%48%
2160
11th to 20thDay
6%6%26%6%35%45%6%50%
2160
21st to endDay
46%35%5%34446%57%
1938
October1st to 10thDay
5%8%36%5%4445%5%53%
1800
11th to 20thDay
2423434447%63%
1800
21st to endDay
25%46%5%24346%60%
1980
November1st to 10thDay
1333323446%66%
1694
11th to 20thDay
224424347%66%
1710
21st to endDay
336%5%34348%60%
1554
December1st to 10thDay
338%7%46%45%7%54%
1520
11th to 20thDay
337%6%445%7%11%49%
1926
21st to endDay
339%7%36%46%9%48%
2794
January1st to 10thNight
226%5%36%6%7%9%55%
2647
11th to 20thNight
225%435%6%5%9%58%
2414
21st to endNight
226%5%5%6%6%5%9%55%
2574
February1st to 10thNight
127%6%36%47%8%54%
2340
11th to 20thNight
227%6%46%7%9%9%50%
2173
21st to endNight
237%7%46%5%7%10%50%
1776
March1st to 10thNight
325%6%25%5%6%8%58%
2094
11th to 20thNight
436%4345%6%8%56%
1980
21st to endNight
1437%5%345%7%9%51%
2101
April1st to 10thNight
13235%345%6%10%58%
1800
11th to 20thNight
17%36%6%445%6%8%50%
1777
21st to endNight
26%35%5%2445%9%54%
1800
May1st to 10thNight
36%36%435%5%6%8%51%
1726
11th to 20thNight
311%45%445%46%8%46%
1417
21st to endNight
45%24435%6%6%8%53%
1552
June1st to 10thNight
132331446%10%63%
1440
11th to 20thNight
441332445%5%65%
1440
21st to endNight
22234345%6%10%60%
1440
July1st to 10thNight
5%5%36%436%6%6%9%46%
1440
11th to 20thNight
2224436%5%7%9%56%
1440
21st to endNight
5%5%26%5%46%5%7%11%42%
1751
August1st to 10thNight
5%5%37%5%445%7%10%45%
1611
11th to 20thNight
6%5%245%35%46%8%52%
1723
21st to endNight
4426%5%46%5%7%8%49%
1980
September1st to 10thNight
3424445%5%6%9%55%
1800
11th to 20thNight
45%2442345%7%60%
1800
21st to endNight
241343445%7%63%
2017
October1st to 10thNight
45%24435%45%7%58%
2160
11th to 20thNight
132332335%6%70%
2160
21st to endNight
25%26%423447%61%
2376
November1st to 10thNight
324322347%70%
2364
11th to 20thNight
1144245%6%8%66%
2470
21st to endNight
335%43446%9%59%
2622
December1st to 10thNight
225%5%445%5%9%60%
2660
11th to 20thNight
3246%35%5%7%10%53%
3271
21st to endNight
328%7%45%48%9%50%
4873

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 10thDay
26%8%20%25%18%4
1519
11th to 20thDay
27%8%21%21%19%5%
1607
21st to endDay
31%7%16%27%13%6%
1782
February1st to 10thDay
33%11%18%18%15%6%
1620
11th to 20thDay
30%10%13%22%19%6%
1681
21st to endDay
35%6%14%20%17%6%
1480
March1st to 10thDay
35%6%12%24%22%2
1862
11th to 20thDay
33%8%17%24%14%4
1980
21st to endDay
39%8%16%22%14%2
2254
April1st to 10thDay
34%9%15%21%15%6%
2160
11th to 20thDay
43%7%15%17%16%2
2134
21st to endDay
40%9%13%25%12%1
2160
May1st to 10thDay
42%8%14%20%14%1
2227
11th to 20thDay
44%9%15%23%8%1
2482
21st to endDay
40%9%12%20%14%4
2724
June1st to 10thDay
30%9%14%21%20%6%
2520
11th to 20thDay
28%7%10%18%23%14%
2520
21st to endDay
31%7%10%18%22%12%
2520
July1st to 10thDay
40%8%10%14%18%10%
2451
11th to 20thDay
41%10%13%16%12%7%
2445
21st to endDay
51%11%15%13%8%2
2421
August1st to 10thDay
50%10%12%11%12%5%
2313
11th to 20thDay
40%8%12%15%18%6%
2175
21st to endDay
43%9%11%18%15%4
2376
September1st to 10thDay
36%7%10%13%23%12%
2160
11th to 20thDay
31%8%11%18%23%8%
2160
21st to endDay
29%5%8%24%28%6%
1938
October1st to 10thDay
32%8%9%20%25%8%
1800
11th to 20thDay
20%6%9%25%30%9%
1800
21st to endDay
26%6%11%29%22%8%
1980
November1st to 10thDay
19%5%15%22%33%6%
1694
11th to 20thDay
18%6%14%30%24%7%
1710
21st to endDay
24%6%12%27%19%11%
1554
December1st to 10thDay
26%10%19%26%15%4
1520
11th to 20thDay
25%10%15%27%20%2
1924
21st to endDay
26%11%13%17%23%8%
2794
January1st to 10thNight
20%11%19%28%18%4
2647
11th to 20thNight
20%9%22%26%18%7%
2414
21st to endNight
21%9%18%29%18%6%
2574
February1st to 10thNight
25%8%20%25%18%5%
2340
11th to 20thNight
24%10%16%24%22%5%
2174
21st to endNight
25%8%17%23%21%6%
1776
March1st to 10thNight
22%8%15%27%24%4
2094
11th to 20thNight
23%7%17%32%16%5%
1980
21st to endNight
26%8%19%28%16%3
2101
April1st to 10thNight
20%10%18%27%20%5%
1800
11th to 20thNight
29%7%17%28%17%2
1777
21st to endNight
26%9%18%29%17%1
1800
May1st to 10thNight
29%9%15%29%16%1
1726
11th to 20thNight
34%10%16%28%12%
1418
21st to endNight
26%9%15%26%20%5%
1552
June1st to 10thNight
17%9%15%30%22%7%
1440
11th to 20thNight
19%8%11%19%29%14%
1440
21st to endNight
17%7%14%22%27%13%
1440
July1st to 10thNight
30%10%16%17%18%9%
1400
11th to 20thNight
22%11%19%22%18%7%
1392
21st to endNight
32%13%25%19%8%2
1654
August1st to 10thNight
30%14%19%18%14%5%
1602
11th to 20thNight
28%8%19%17%22%6%
1723
21st to endNight
29%10%17%22%18%4
1980
September1st to 10thNight
25%8%14%18%25%10%
1800
11th to 20thNight
23%6%15%23%24%9%
1800
21st to endNight
21%6%12%32%26%4
2017
October1st to 10thNight
23%9%12%24%22%10%
2160
11th to 20thNight
14%5%12%30%30%10%
2160
21st to endNight
21%7%13%29%24%7%
2376
November1st to 10thNight
15%6%15%27%30%7%
2364
11th to 20thNight
13%7%16%31%24%8%
2470
21st to endNight
21%7%13%27%22%10%
2622
December1st to 10thNight
19%10%21%25%19%7%
2660
11th to 20thNight
21%11%16%24%23%5%
3272
21st to endNight
24%11%15%18%20%11%
4873

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 10thDay
22%29%21%20%7%1
270
11th to 20thDay
20%36%24%16%3
246
21st to endDay
15%38%33%13%1
264
February1st to 10thDay
30%42%20%5%11
240
11th to 20thDay
31%34%22%10%3
240
21st to endDay
30%38%24%7%1
198
March1st to 10thDay
23%37%26%11%3
302
11th to 20thDay
22%31%31%14%3
420
21st to endDay
20%44%28%7%1
462
April1st to 10thDay
18%40%32%8%21
420
11th to 20thDay
25%38%25%9%2
412
21st to endDay
17%41%29%10%21
420
May1st to 10thDay
18%34%31%12%41
431
11th to 20thDay
12%21%36%19%9%2
625
21st to endDay
14%21%29%25%9%2
679
June1st to 10thDay
7%17%30%27%17%2
630
11th to 20thDay
9%21%34%23%11%2
630
21st to endDay
419%34%22%18%2
630
July1st to 10thDay
8%8%29%30%21%4
621
11th to 20thDay
8%6%28%29%22%6%
618
21st to endDay
12%10%29%32%16%2
505
August1st to 10thDay
12%12%38%24%11%3
447
11th to 20thDay
8%12%36%26%13%5%
437
21st to endDay
10%12%33%30%12%3
495
September1st to 10thDay
11%16%33%24%12%4
450
11th to 20thDay
9%18%40%20%10%2
450
21st to endDay
11%21%29%25%10%4
302
October1st to 10thDay
13%23%24%22%16%2
270
11th to 20thDay
20%26%29%14%8%2
270
21st to endDay
17%30%31%15%7%1
297
November1st to 10thDay
21%33%25%13%7%1
270
11th to 20thDay
21%29%31%13%41
270
21st to endDay
14%31%34%17%3
270
December1st to 10thDay
24%33%24%12%5%1
270
11th to 20thDay
22%38%25%9%41
270
21st to endDay
24%35%27%9%4
297
January1st to 10thNight
13%27%29%22%8%1
950
11th to 20thNight
13%26%33%19%7%1
776
21st to endNight
7%26%41%19%6%1
792
February1st to 10thNight
12%28%40%15%4
720
11th to 20thNight
12%30%36%18%4
704
21st to endNight
11%29%43%15%2
592
March1st to 10thNight
9%28%34%24%5%
720
11th to 20thNight
5%21%43%23%9%
720
21st to endNight
7%28%41%20%4
715
April1st to 10thNight
8%26%40%22%4
540
11th to 20thNight
8%28%35%22%8%1
533
21st to endNight
7%23%37%25%7%1
540
May1st to 10thNight
7%15%42%25%11%1
540
11th to 20thNight
8%9%32%33%16%2
531
21st to endNight
8%12%27%35%16%2
584
June1st to 10thNight
48%27%36%24%1
540
11th to 20thNight
5%11%30%39%14%1
540
21st to endNight
16%23%37%30%2
540
July1st to 10thNight
7%311%40%34%4
525
11th to 20thNight
3211%38%42%4
522
21st to endNight
6%210%32%45%5%
591
August1st to 10thNight
8%212%38%37%3
537
11th to 20thNight
5%316%37%34%4
534
21st to endNight
4218%36%36%5%
594
September1st to 10thNight
4418%42%26%5%
540
11th to 20thNight
6%422%40%24%3
540
21st to endNight
410%26%34%22%4
611
October1st to 10thNight
5%16%33%26%16%4
720
11th to 20thNight
7%18%33%26%13%2
720
21st to endNight
7%21%34%25%10%2
792
November1st to 10thNight
8%21%37%23%9%1
884
11th to 20thNight
11%26%35%20%7%1
950
21st to endNight
8%23%35%28%7%
950
December1st to 10thNight
11%29%35%19%6%
950
11th to 20thNight
12%28%35%18%6%
950
21st to endNight
14%27%36%18%41
1045
Page generated at 2024-01-09 23:25:02. Version ac07

Copyright 2024 Attilla Danko


Mount Massive Lakes Observatory Clear Sky Chart |Charts Home