Robinson Lunar Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Robinson Lunar Observatory clear sky chart from 2005-11-06 to 2024-01-17.

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
41%
24504
23%
74770
14%
24443
50%
24443
31%
44960

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
32%
950
23%
2458
9%
946
42%
946
32%
1577
January11th to 20thNight
27%
933
23%
2425
8%
933
37%
933
27%
1623
January21st to endNight
29%
990
23%
2574
8%
990
38%
990
30%
1703
February1st to 10thNight
23%
900
17%
2340
5%
900
29%
900
25%
1623
February11th to 20thNight
26%
879
18%
2274
7%
875
33%
875
28%
1520
February21st to endNight
25%
558
25%
1742
8%
558
39%
558
26%
1073
March1st to 10thNight
25%
540
26%
1980
11%
540
42%
540
26%
1114
March11th to 20thNight
30%
540
20%
1980
13%
540
41%
540
21%
1229
March21st to endNight
24%
594
14%
2178
8%
594
34%
594
16%
1481
April1st to 10thNight
30%
540
22%
1890
13%
540
46%
540
28%
1072
April11th to 20thNight
31%
533
23%
1775
15%
533
44%
533
27%
1064
April21st to endNight
32%
540
21%
1652
12%
540
47%
540
25%
1069
May1st to 10thNight
37%
540
17%
1620
13%
540
45%
540
24%
1074
May11th to 20thNight
42%
531
20%
1594
16%
531
49%
531
32%
958
May21st to endNight
49%
584
19%
1710
13%
582
56%
582
33%
1045
June1st to 10thNight
64%
540
24%
1440
15%
540
69%
540
46%
806
June11th to 20thNight
58%
540
23%
1440
15%
540
62%
540
44%
833
June21st to endNight
58%
540
27%
1464
16%
540
64%
540
53%
764
July1st to 10thNight
72%
525
18%
1575
16%
525
74%
525
41%
863
July11th to 20thNight
77%
522
25%
1566
22%
522
80%
522
55%
742
July21st to endNight
71%
591
26%
1673
26%
558
74%
558
42%
897
August1st to 10thNight
72%
537
23%
1601
24%
534
77%
534
44%
842
August11th to 20thNight
72%
534
30%
1600
32%
534
77%
534
44%
844
August21st to endNight
72%
594
30%
1913
33%
594
76%
594
45%
966
September1st to 10thNight
62%
540
28%
1800
28%
540
67%
540
36%
985
September11th to 20thNight
61%
540
29%
1975
28%
540
68%
540
36%
1011
September21st to endNight
62%
540
31%
1980
29%
540
68%
540
38%
979
October1st to 10thNight
50%
704
27%
2144
20%
704
55%
704
37%
1198
October11th to 20thNight
34%
720
29%
2160
14%
720
45%
720
37%
1196
October21st to endNight
33%
792
26%
2376
13%
792
43%
792
29%
1432
November1st to 10thNight
41%
754
32%
2234
16%
754
55%
754
40%
1191
November11th to 20thNight
34%
950
28%
2522
10%
950
48%
950
37%
1480
November21st to endNight
34%
950
25%
2660
11%
950
46%
950
33%
1597
December1st to 10thNight
33%
950
21%
2660
9%
950
44%
950
29%
1687
December11th to 20thNight
27%
949
23%
3124
8%
948
38%
948
24%
1900
December21st to endNight
24%
1040
15%
4671
8%
1026
38%
1026
12%
3522

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
12%7%35%5%3445%7%45%
74657
Night
11%6%35%42445%7%49%
75175
TransparencyDay
39%5%13%26%16%2
74380
Night
36%411%27%18%3
74972
SeeingDay
15%8%27%29%17%4
14515
Night
14%8%31%34%12%1
24510

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
14%7%36%5%44446%45%
1707
11th to 20thDay
13%9%5%7%6%3344441%
1674
21st to endDay
12%9%6%7%5%3445%7%38%
1782
February1st to 10thDay
15%10%5%7%5%33436%39%
1620
11th to 20thDay
12%9%5%7%43345%7%40%
1574
21st to endDay
12%10%36%5%245%5%6%42%
1530
March1st to 10thDay
13%8%36%5%2445%7%42%
1980
11th to 20thDay
20%10%46%423446%36%
1980
21st to endDay
20%11%46%5%35%5%5%5%31%
2178
April1st to 10thDay
14%7%35%5%2435%6%45%
2070
11th to 20thDay
14%9%35%6%3445%7%40%
2134
21st to endDay
19%8%36%6%45%446%36%
2304
May1st to 10thDay
18%8%46%5%35%446%36%
2340
11th to 20thDay
16%7%35%5%35%5%5%7%40%
2302
21st to endDay
14%7%37%6%35%46%8%35%
2562
June1st to 10thDay
7%325%5%35%5%7%10%49%
2520
11th to 20thDay
8%425%435%5%7%9%48%
2520
21st to endDay
7%324436%5%6%8%53%
2488
July1st to 10thDay
9%425%4345%7%9%46%
2340
11th to 20thDay
4424435%6%8%8%53%
2340
21st to endDay
8%4245%36%6%6%9%45%
2546
August1st to 10thDay
7%425%5%36%5%6%11%45%
2328
11th to 20thDay
9%425%4335%6%8%51%
2301
21st to endDay
8%42443445%8%54%
2441
September1st to 10thDay
13%42442435%7%52%
2160
11th to 20thDay
9%5%345%35%5%5%7%50%
1980
21st to endDay
9%4245%3445%7%56%
1977
October1st to 10thDay
13%5%2442335%7%51%
1800
11th to 20thDay
13%6%3342334456%
1800
21st to endDay
15%7%3443335%5%48%
1980
November1st to 10thDay
10%5%2443335%6%55%
1840
11th to 20thDay
14%5%24423446%52%
1655
21st to endDay
16%8%35%423236%49%
1520
December1st to 10thDay
9%8%35%6%3335%8%46%
1520
11th to 20thDay
12%10%47%5%43446%41%
1918
21st to endDay
16%16%7%12%424436%26%
2946
January1st to 10thNight
8%8%36%5%35%445%50%
2458
11th to 20thNight
11%9%46%43446%6%43%
2425
21st to endNight
10%9%37%5%3445%6%45%
2574
February1st to 10thNight
11%11%46%6%44447%39%
2340
11th to 20thNight
12%8%46%434446%43%
2273
21st to endNight
13%7%45%6%24445%46%
1742
March1st to 10thNight
11%7%45%424446%49%
1980
11th to 20thNight
16%9%35%424446%43%
1980
21st to endNight
22%9%36%5%34346%35%
2178
April1st to 10thNight
11%5%35%5%34447%50%
1890
11th to 20thNight
14%7%345%2435%6%47%
1775
21st to endNight
17%6%35%424446%44%
1652
May1st to 10thNight
15%5%36%5%35%5%6%7%40%
1620
11th to 20thNight
14%5%24433448%49%
1593
21st to endNight
10%5%35%5%345%6%9%46%
1709
June1st to 10thNight
5%2225%245%6%10%57%
1440
11th to 20thNight
6%225%435%6%6%10%53%
1440
21st to endNight
5%21322446%8%63%
1464
July1st to 10thNight
7%3144345%7%9%53%
1620
11th to 20thNight
32133245%6%11%61%
1620
21st to endNight
6%324425%5%7%10%51%
1772
August1st to 10thNight
4213335%6%7%10%55%
1611
11th to 20thNight
7%32442445%9%58%
1600
21st to endNight
6%31442435%7%60%
1913
September1st to 10thNight
10%5%24324436%56%
1800
11th to 20thNight
9%42443445%7%55%
1975
21st to endNight
6%424424446%60%
1980
October1st to 10thNight
12%41432445%457%
2144
11th to 20thNight
15%423323246%57%
2160
21st to endNight
15%7%34333335%52%
2376
November1st to 10thNight
9%423323446%61%
2234
11th to 20thNight
11%5%2342335%6%56%
2522
21st to endNight
15%7%34323345%52%
2660
December1st to 10thNight
11%7%36%435%45%6%47%
2660
11th to 20thNight
12%8%36%423446%46%
3279
21st to endNight
19%16%5%9%43333430%
4716

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
41%410%27%17%1
1708
11th to 20thDay
47%312%26%12%1
1674
21st to endDay
47%414%23%11%1
1782
February1st to 10thDay
48%413%23%10%2
1620
11th to 20thDay
45%313%23%14%2
1583
21st to endDay
42%412%25%14%3
1530
March1st to 10thDay
42%412%24%14%4
1980
11th to 20thDay
50%49%22%13%2
1980
21st to endDay
55%5%12%18%8%1
2178
April1st to 10thDay
40%313%23%18%2
2070
11th to 20thDay
44%413%23%15%1
2134
21st to endDay
49%411%25%11%1
2304
May1st to 10thDay
49%6%11%20%13%1
2340
11th to 20thDay
44%5%13%24%13%
2306
21st to endDay
46%7%14%22%9%2
2562
June1st to 10thDay
29%6%17%32%15%2
2520
11th to 20thDay
30%7%14%30%17%2
2520
21st to endDay
28%5%15%32%17%4
2488
July1st to 10thDay
32%7%16%25%17%3
2276
11th to 20thDay
26%8%15%28%20%4
2271
21st to endDay
31%6%15%31%16%1
2405
August1st to 10thDay
32%7%18%28%13%2
2314
11th to 20thDay
30%6%13%32%18%2
2301
21st to endDay
28%6%12%27%20%7%
2441
September1st to 10thDay
33%412%28%18%6%
2160
11th to 20thDay
33%5%11%26%22%3
1980
21st to endDay
29%49%32%24%3
1977
October1st to 10thDay
32%412%29%20%2
1800
11th to 20thDay
33%36%29%24%5%
1800
21st to endDay
39%311%23%19%5%
1980
November1st to 10thDay
30%413%30%19%5%
1840
11th to 20thDay
35%310%28%21%3
1655
21st to endDay
40%39%27%21%1
1520
December1st to 10thDay
38%314%30%14%1
1520
11th to 20thDay
45%413%27%10%1
1915
21st to endDay
62%410%16%7%1
2946
January1st to 10thNight
37%414%26%18%2
2458
11th to 20thNight
42%5%12%26%15%1
2425
21st to endNight
41%314%26%13%2
2574
February1st to 10thNight
47%311%22%14%3
2340
11th to 20thNight
43%312%23%16%3
2274
21st to endNight
40%39%22%19%6%
1742
March1st to 10thNight
37%39%27%19%4
1980
11th to 20thNight
43%410%23%16%4
1980
21st to endNight
51%411%20%11%2
2178
April1st to 10thNight
35%411%26%21%4
1890
11th to 20thNight
39%39%28%18%3
1775
21st to endNight
42%5%11%25%16%1
1652
May1st to 10thNight
43%6%12%22%16%1
1620
11th to 20thNight
36%415%27%18%1
1594
21st to endNight
34%6%18%29%11%3
1710
June1st to 10thNight
22%7%18%33%16%3
1440
11th to 20thNight
25%7%15%31%19%2
1440
21st to endNight
19%5%14%37%21%4
1464
July1st to 10thNight
26%6%15%33%17%4
1575
11th to 20thNight
17%415%36%23%4
1566
21st to endNight
26%5%13%34%21%1
1673
August1st to 10thNight
22%7%18%35%15%3
1601
11th to 20thNight
24%5%13%34%22%2
1600
21st to endNight
25%311%30%24%8%
1913
September1st to 10thNight
30%5%8%29%19%8%
1800
11th to 20thNight
28%411%27%26%5%
1975
21st to endNight
26%47%28%30%4
1980
October1st to 10thNight
31%39%26%25%6%
2144
11th to 20thNight
31%26%29%23%8%
2160
21st to endNight
38%38%23%25%4
2376
November1st to 10thNight
26%412%28%25%6%
2234
11th to 20thNight
31%310%28%24%4
2522
21st to endNight
36%29%30%19%3
2660
December1st to 10thNight
39%412%28%16%1
2660
11th to 20thNight
39%311%31%15%1
3281
21st to endNight
60%47%19%9%2
4716

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
23%12%34%24%6%
270
11th to 20thDay
25%16%37%20%2
258
21st to endDay
16%12%45%25%2
264
February1st to 10thDay
22%18%40%18%31
240
11th to 20thDay
21%18%42%13%6%
240
21st to endDay
20%24%37%14%5%
198
March1st to 10thDay
17%15%45%18%3
240
11th to 20thDay
30%11%34%20%5%1
240
21st to endDay
33%17%32%15%31
264
April1st to 10thDay
23%13%36%20%8%
330
11th to 20thDay
18%14%36%24%8%1
412
21st to endDay
24%12%33%21%10%
564
May1st to 10thDay
21%11%35%23%8%1
603
11th to 20thDay
21%6%28%28%14%2
625
21st to endDay
18%6%28%25%19%5%
679
June1st to 10thDay
7%320%35%27%9%
630
11th to 20thDay
9%324%37%21%7%
630
21st to endDay
8%432%37%16%3
630
July1st to 10thDay
10%212%32%29%14%
621
11th to 20thDay
5%116%39%31%9%
618
21st to endDay
9%114%36%32%8%
684
August1st to 10thDay
8%116%39%31%5%
626
11th to 20thDay
9%213%37%30%8%
615
21st to endDay
9%113%33%34%11%
560
September1st to 10thDay
15%214%36%26%7%
450
11th to 20thDay
7%121%39%24%7%
270
21st to endDay
14%6%24%35%16%5%
270
October1st to 10thDay
17%6%26%26%19%6%
270
11th to 20thDay
13%16%42%21%7%1
270
21st to endDay
22%13%36%20%8%2
297
November1st to 10thDay
16%8%39%27%7%4
270
11th to 20thDay
16%16%33%24%8%2
270
21st to endDay
24%11%35%21%9%
270
December1st to 10thDay
9%13%42%27%7%3
270
11th to 20thDay
21%11%36%23%8%1
270
21st to endDay
20%21%39%18%2
297
January1st to 10thNight
13%11%38%31%7%
950
11th to 20thNight
16%12%37%28%6%1
933
21st to endNight
15%11%40%29%4
990
February1st to 10thNight
19%11%40%26%3
900
11th to 20thNight
17%12%39%28%4
879
21st to endNight
19%11%41%23%6%1
558
March1st to 10thNight
15%13%42%24%6%
540
11th to 20thNight
22%8%33%30%6%1
540
21st to endNight
27%10%35%24%4
594
April1st to 10thNight
14%11%40%29%6%
540
11th to 20thNight
19%10%35%31%6%
533
21st to endNight
20%6%37%29%7%1
540
May1st to 10thNight
18%6%32%35%8%1
540
11th to 20thNight
18%330%35%13%1
531
21st to endNight
11%5%27%36%18%2
584
June1st to 10thNight
6%321%45%25%1
540
11th to 20thNight
6%225%45%20%2
540
21st to endNight
6%230%45%16%1
540
July1st to 10thNight
8%11%44%33%4
525
11th to 20thNight
3113%48%32%3
522
21st to endNight
7%112%48%30%2
591
August1st to 10thNight
5%113%48%31%2
537
11th to 20thNight
7%212%45%31%2
534
21st to endNight
6%112%43%34%3
594
September1st to 10thNight
14%116%42%23%4
540
11th to 20thNight
10%120%41%25%3
540
21st to endNight
9%419%49%16%3
540
October1st to 10thNight
13%428%32%20%2
704
11th to 20thNight
16%8%38%29%8%
720
21st to endNight
20%10%33%28%9%
792
November1st to 10thNight
11%8%35%33%12%1
754
11th to 20thNight
14%12%36%29%8%
950
21st to endNight
18%10%34%31%6%
950
December1st to 10thNight
15%10%37%31%7%1
950
11th to 20thNight
20%7%39%28%5%
950
21st to endNight
20%14%35%26%4
1045
Page generated at 2024-01-13 22:56:38. Version ac07

Copyright 2024 Attilla Danko


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