Morning Calm Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Morning Calm Observatory clear sky chart from 2005-11-06 to 2024-03-01.

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
42%
23783
21%
80039
13%
23686
52%
23686
25%
48930

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
26%
752
27%
4049
10%
737
45%
737
17%
2034
January11th to 20thNight
30%
760
28%
3938
11%
740
46%
740
16%
2136
January21st to endNight
28%
829
16%
4438
12%
814
46%
814
16%
2650
February1st to 10thNight
31%
760
20%
2470
10%
760
45%
760
24%
1554
February11th to 20thNight
19%
740
20%
2398
6%
740
37%
740
20%
1513
February21st to endNight
22%
628
24%
1841
9%
628
39%
628
23%
1192
March1st to 10thNight
29%
723
26%
1987
12%
723
43%
723
29%
1217
March11th to 20thNight
28%
720
21%
1980
10%
720
39%
720
25%
1301
March21st to endNight
27%
792
20%
2178
8%
792
37%
792
25%
1440
April1st to 10thNight
30%
720
19%
1814
6%
720
39%
720
27%
1199
April11th to 20thNight
36%
711
22%
1775
8%
711
43%
711
34%
1129
April21st to endNight
39%
720
21%
1800
9%
720
45%
720
31%
1203
May1st to 10thNight
41%
542
17%
1622
8%
542
48%
542
24%
1077
May11th to 20thNight
44%
531
15%
1592
8%
531
49%
531
24%
1071
May21st to endNight
56%
388
16%
1551
17%
388
59%
388
22%
933
June1st to 10thNight
58%
360
18%
1440
20%
360
64%
360
26%
800
June11th to 20thNight
61%
360
15%
1440
17%
360
65%
360
21%
878
June21st to endNight
67%
360
18%
1440
22%
360
72%
360
26%
837
July1st to 10thNight
62%
377
16%
1427
18%
377
65%
377
21%
893
July11th to 20thNight
74%
522
15%
1566
13%
522
75%
522
32%
969
July21st to endNight
67%
591
16%
1672
13%
558
70%
558
31%
1044
August1st to 10thNight
66%
537
16%
1600
12%
534
68%
534
26%
1064
August11th to 20thNight
60%
569
18%
1633
13%
569
62%
569
26%
1106
August21st to endNight
61%
792
17%
1980
11%
792
62%
792
29%
1373
September1st to 10thNight
60%
720
22%
1800
14%
720
62%
720
32%
1212
September11th to 20thNight
60%
720
28%
1839
21%
720
63%
720
35%
1175
September21st to endNight
46%
720
20%
2058
15%
720
51%
720
25%
1385
October1st to 10thNight
51%
720
20%
2160
20%
720
55%
720
28%
1360
October11th to 20thNight
44%
720
26%
2160
19%
720
56%
720
30%
1311
October21st to endNight
45%
792
29%
2376
20%
792
57%
792
32%
1416
November1st to 10thNight
43%
740
29%
2221
19%
740
56%
740
32%
1304
November11th to 20thNight
38%
760
25%
2529
15%
760
53%
760
28%
1466
November21st to endNight
39%
760
24%
2660
15%
760
53%
760
29%
1484
December1st to 10thNight
31%
760
21%
2660
11%
760
45%
760
22%
1652
December11th to 20thNight
37%
759
22%
3167
14%
759
49%
759
21%
1836
December21st to endNight
36%
828
15%
4778
14%
817
49%
817
14%
2716

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
14%6%25%5%35%5%6%7%43%
78548
Night
15%6%25%43445%7%45%
80856
TransparencyDay
39%8%12%22%16%4
78265
Night
38%7%12%23%17%4
80658
SeeingDay
18%11%26%25%14%6%
14006
Night
17%7%27%32%15%2
23811

By Month

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 10thDay
17%5%25%423445%47%
2776
11th to 20thDay
13%8%37%6%35%45%441%
2840
21st to endDay
16%9%36%6%3445%6%39%
3124
February1st to 10thDay
13%8%35%6%45%46%6%42%
1710
11th to 20thDay
18%7%25%42345%7%41%
1668
21st to endDay
17%8%26%5%35%46%5%39%
1608
March1st to 10thDay
14%6%25%424446%51%
1980
11th to 20thDay
15%6%36%5%35%5%6%6%41%
1980
21st to endDay
17%8%35%5%35%5%6%6%38%
2178
April1st to 10thDay
10%6%245%36%45%7%48%
2146
11th to 20thDay
14%5%25%5%3435%6%49%
2134
21st to endDay
17%6%25%5%35%45%5%42%
2173
May1st to 10thDay
15%6%25%6%345%7%8%38%
2340
11th to 20thDay
19%6%35%5%45%6%5%7%37%
2301
21st to endDay
15%5%26%5%35%6%6%9%40%
2723
June1st to 10thDay
11%5%245%35%6%6%8%44%
2520
11th to 20thDay
11%5%26%6%46%5%6%10%39%
2520
21st to endDay
9%3245%5%5%6%8%10%44%
2520
July1st to 10thDay
10%5%25%6%46%6%7%9%40%
2486
11th to 20thDay
5%425%5%47%8%9%11%41%
2340
21st to endDay
10%5%26%7%47%6%8%10%35%
2547
August1st to 10thDay
9%5%26%7%5%7%6%8%9%35%
2327
11th to 20thDay
12%5%25%7%46%7%7%10%35%
2249
21st to endDay
11%425%6%45%6%6%10%41%
2376
September1st to 10thDay
14%6%25%5%35%45%7%45%
2160
11th to 20thDay
12%5%25%42445%8%48%
2118
21st to endDay
20%7%345%345%5%6%39%
1901
October1st to 10thDay
15%5%35%5%3445%7%46%
1800
11th to 20thDay
17%4145%33445%50%
1800
21st to endDay
15%5%24424346%51%
1980
November1st to 10thDay
12%5%23433446%54%
1857
11th to 20thDay
14%5%2442345%6%50%
1644
21st to endDay
15%4234245%46%52%
1520
December1st to 10thDay
16%6%25%4345%5%8%42%
1520
11th to 20thDay
17%5%24433345%51%
1910
21st to endDay
20%6%25%5%345%5%8%37%
2772
January1st to 10thNight
14%6%24424446%51%
4164
11th to 20thNight
17%7%24323345%49%
4120
21st to endNight
19%8%35%423345%44%
4532
February1st to 10thNight
14%7%35%4345%6%7%43%
2470
11th to 20thNight
19%7%35%33345%5%43%
2396
21st to endNight
16%7%36%5%2345%6%44%
1841
March1st to 10thNight
13%42442445%5%52%
1987
11th to 20thNight
17%7%244335%47%44%
1980
21st to endNight
15%6%25%5%2445%6%44%
2178
April1st to 10thNight
14%7%25%4245%5%7%45%
1814
11th to 20thNight
12%425%425%347%50%
1775
21st to endNight
17%5%25%4245%6%7%45%
1800
May1st to 10thNight
17%4345%35%5%6%9%40%
1622
11th to 20thNight
18%6%235%45%5%6%8%39%
1592
21st to endNight
15%5%25%5%445%5%8%43%
1550
June1st to 10thNight
11%4245%3447%10%46%
1440
11th to 20thNight
12%6%246%36%5%6%7%44%
1440
21st to endNight
9%325%5%36%6%8%10%44%
1440
July1st to 10thNight
11%5%26%5%46%46%9%42%
1468
11th to 20thNight
5%4245%36%6%8%11%46%
1620
21st to endNight
8%5%15%6%45%6%8%12%40%
1771
August1st to 10thNight
10%5%26%5%46%6%7%9%40%
1611
11th to 20thNight
11%6%36%6%35%6%6%8%40%
1633
21st to endNight
11%6%36%6%35%5%6%10%39%
1980
September1st to 10thNight
16%6%2342446%8%45%
1800
11th to 20thNight
12%6%25%6%3345%7%49%
1839
21st to endNight
21%6%24434446%42%
2058
October1st to 10thNight
19%5%25%434436%46%
2160
11th to 20thNight
16%5%2442345%6%50%
2160
21st to endNight
16%42332445%6%51%
2376
November1st to 10thNight
12%6%24423345%53%
2221
11th to 20thNight
15%5%24424446%50%
2529
21st to endNight
14%414434446%51%
2660
December1st to 10thNight
16%6%35%6%345%5%5%43%
2660
11th to 20thNight
16%6%24434446%47%
3285
21st to endNight
17%5%35%4345%6%6%41%
4884

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
36%7%9%29%15%5%
2777
11th to 20thDay
42%6%10%19%16%7%
2840
21st to endDay
45%7%10%21%15%3
3124
February1st to 10thDay
42%6%12%24%14%3
1710
11th to 20thDay
41%6%9%22%18%4
1677
21st to endDay
44%6%13%15%16%5%
1608
March1st to 10thDay
36%5%10%23%22%5%
1980
11th to 20thDay
42%6%10%17%17%7%
1980
21st to endDay
45%7%10%18%15%6%
2178
April1st to 10thDay
35%6%13%20%18%8%
2146
11th to 20thDay
35%6%11%19%21%6%
2134
21st to endDay
43%7%11%21%14%5%
2173
May1st to 10thDay
40%9%15%18%14%3
2340
11th to 20thDay
44%10%13%19%11%2
2305
21st to endDay
40%9%16%23%11%1
2723
June1st to 10thDay
36%9%14%24%16%1
2520
11th to 20thDay
39%10%15%21%13%2
2520
21st to endDay
32%11%16%24%16%1
2520
July1st to 10thDay
38%11%12%20%16%3
2417
11th to 20thDay
31%13%19%23%13%2
2271
21st to endDay
38%12%13%21%14%1
2405
August1st to 10thDay
40%12%16%22%9%
2314
11th to 20thDay
40%12%16%19%12%1
2249
21st to endDay
37%9%16%23%12%3
2376
September1st to 10thDay
38%8%13%18%19%4
2160
11th to 20thDay
34%7%10%27%19%4
2118
21st to endDay
45%7%10%19%17%2
1901
October1st to 10thDay
37%7%10%25%17%4
1800
11th to 20thDay
36%5%9%25%22%4
1800
21st to endDay
34%49%25%22%5%
1980
November1st to 10thDay
32%5%9%25%24%5%
1857
11th to 20thDay
34%5%12%20%22%7%
1644
21st to endDay
34%412%25%22%3
1520
December1st to 10thDay
41%6%12%24%12%4
1520
11th to 20thDay
37%39%31%13%6%
1906
21st to endDay
41%9%12%26%11%1
2772
January1st to 10thNight
33%5%10%26%21%5%
4164
11th to 20thNight
38%49%22%21%6%
4120
21st to endNight
43%5%8%23%18%2
4532
February1st to 10thNight
41%6%11%24%16%3
2470
11th to 20thNight
43%48%21%18%7%
2398
21st to endNight
41%6%11%20%17%5%
1841
March1st to 10thNight
34%5%10%26%21%4
1987
11th to 20thNight
41%6%10%20%19%4
1980
21st to endNight
40%7%11%20%16%6%
2178
April1st to 10thNight
38%6%12%19%21%5%
1814
11th to 20thNight
34%6%12%22%21%6%
1775
21st to endNight
38%7%11%26%13%6%
1800
May1st to 10thNight
41%8%14%20%13%4
1622
11th to 20thNight
42%8%12%20%15%2
1593
21st to endNight
38%9%17%22%13%1
1551
June1st to 10thNight
31%10%16%27%15%2
1440
11th to 20thNight
37%10%16%21%14%2
1440
21st to endNight
32%10%18%19%18%3
1440
July1st to 10thNight
38%11%15%18%14%4
1427
11th to 20thNight
29%13%20%24%13%2
1566
21st to endNight
32%11%19%24%13%1
1672
August1st to 10thNight
37%12%16%23%11%2
1600
11th to 20thNight
40%10%14%23%12%1
1633
21st to endNight
39%10%16%23%11%2
1980
September1st to 10thNight
37%8%12%22%16%5%
1800
11th to 20thNight
35%6%11%25%19%3
1839
21st to endNight
43%6%10%20%17%3
2058
October1st to 10thNight
40%5%11%23%18%3
2160
11th to 20thNight
36%5%8%26%20%5%
2160
21st to endNight
33%6%10%23%23%5%
2376
November1st to 10thNight
34%5%9%23%23%7%
2221
11th to 20thNight
36%48%22%23%7%
2529
21st to endNight
34%411%24%22%5%
2660
December1st to 10thNight
42%5%11%24%15%4
2660
11th to 20thNight
38%5%10%22%19%5%
3288
21st to endNight
38%9%15%24%13%2
4884

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
25%21%33%17%4
254
11th to 20thDay
28%23%29%16%3
270
21st to endDay
23%23%38%12%31
297
February1st to 10thDay
23%24%36%15%2
270
11th to 20thDay
35%24%33%7%1
275
21st to endDay
29%14%34%20%3
382
March1st to 10thDay
22%19%32%22%4
420
11th to 20thDay
23%20%27%22%6%2
420
21st to endDay
23%17%36%16%7%1
462
April1st to 10thDay
20%23%24%22%9%2
420
11th to 20thDay
18%17%25%24%13%4
412
21st to endDay
24%11%33%21%9%2
420
May1st to 10thDay
22%14%29%22%10%4
423
11th to 20thDay
21%9%29%26%12%4
447
21st to endDay
20%425%26%17%7%
485
June1st to 10thDay
14%5%26%28%21%6%
450
11th to 20thDay
13%8%25%30%15%8%
450
21st to endDay
10%6%25%34%19%7%
450
July1st to 10thDay
14%215%32%26%11%
445
11th to 20thDay
5%217%32%30%14%
444
21st to endDay
11%416%32%26%10%
488
August1st to 10thDay
10%420%26%26%13%
446
11th to 20thDay
12%318%28%26%13%
439
21st to endDay
9%317%31%24%15%
495
September1st to 10thDay
16%5%16%27%20%16%
450
11th to 20thDay
16%319%26%24%12%
450
21st to endDay
26%8%19%26%16%5%
450
October1st to 10thDay
20%6%20%30%18%6%
450
11th to 20thDay
15%14%27%27%15%3
450
21st to endDay
18%12%32%25%11%3
495
November1st to 10thDay
15%11%31%27%12%4
455
11th to 20thDay
19%11%29%28%12%2
304
21st to endDay
19%13%39%22%6%
180
December1st to 10thDay
19%14%41%20%6%1
180
11th to 20thDay
24%11%37%19%8%1
180
21st to endDay
22%17%34%21%6%
198
January1st to 10thNight
19%13%38%26%4
760
11th to 20thNight
19%10%34%31%5%
760
21st to endNight
19%10%39%31%3
836
February1st to 10thNight
17%8%40%31%4
760
11th to 20thNight
25%15%37%22%2
743
21st to endNight
20%11%40%26%3
628
March1st to 10thNight
16%14%36%29%4
723
11th to 20thNight
20%14%33%26%6%1
720
21st to endNight
18%12%37%26%7%1
792
April1st to 10thNight
18%14%32%28%7%
720
11th to 20thNight
15%11%33%29%10%1
711
21st to endNight
19%8%29%34%9%1
720
May1st to 10thNight
21%7%26%28%17%1
542
11th to 20thNight
19%425%33%18%1
531
21st to endNight
17%118%39%22%3
389
June1st to 10thNight
12%217%43%24%2
360
11th to 20thNight
14%215%41%25%2
360
21st to endNight
9%214%48%25%2
360
July1st to 10thNight
14%113%34%33%5%
377
11th to 20thNight
6%19%36%43%6%
522
21st to endNight
9%113%37%35%5%
591
August1st to 10thNight
12%19%43%31%4
537
11th to 20thNight
12%212%36%33%4
569
21st to endNight
14%212%35%33%5%
792
September1st to 10thNight
18%213%32%29%5%
720
11th to 20thNight
13%314%34%30%5%
720
21st to endNight
26%218%30%21%3
720
October1st to 10thNight
20%5%18%32%21%4
720
11th to 20thNight
16%7%27%33%16%1
720
21st to endNight
18%6%27%35%11%2
792
November1st to 10thNight
15%6%29%35%13%2
740
11th to 20thNight
17%8%32%33%9%1
760
21st to endNight
15%8%33%31%12%1
760
December1st to 10thNight
18%9%35%29%9%
760
11th to 20thNight
17%6%35%36%6%1
760
21st to endNight
19%10%29%38%4
836
Page generated at 2024-02-27 06:30:11. Version ac07

Copyright © 2024 Attilla Danko.


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