Mabee Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mabee Observatory clear sky chart from 2005-11-06 to 2024-02-10.

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
43%
24555
25%
79613
15%
24449
53%
24449
33%
44837

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
35%
940
26%
4031
11%
926
47%
926
23%
2397
January11th to 20thNight
32%
949
28%
4002
11%
930
43%
930
25%
2101
January21st to endNight
34%
1037
20%
4466
12%
1023
45%
1023
23%
2651
February1st to 10thNight
27%
948
21%
2464
7%
948
36%
948
30%
1611
February11th to 20thNight
29%
723
22%
2117
8%
719
39%
719
30%
1262
February21st to endNight
30%
592
29%
1776
11%
592
44%
592
33%
1017
March1st to 10thNight
31%
597
27%
2037
13%
597
45%
597
32%
1089
March11th to 20thNight
30%
540
23%
1980
14%
540
42%
540
26%
1106
March21st to endNight
27%
594
19%
2178
10%
594
40%
594
21%
1344
April1st to 10thNight
31%
540
22%
1980
12%
540
47%
540
30%
1018
April11th to 20thNight
32%
533
24%
1688
14%
533
46%
533
28%
991
April21st to endNight
31%
540
21%
1620
14%
540
44%
540
28%
1010
May1st to 10thNight
34%
540
18%
1620
12%
540
43%
540
27%
1039
May11th to 20thNight
45%
531
21%
1594
18%
531
53%
531
34%
919
May21st to endNight
48%
583
17%
1745
13%
582
55%
582
33%
1042
June1st to 10thNight
60%
540
20%
1620
14%
540
66%
540
44%
856
June11th to 20thNight
53%
540
20%
1620
12%
540
61%
540
43%
848
June21st to endNight
55%
540
23%
1620
16%
540
61%
540
46%
837
July1st to 10thNight
72%
525
19%
1575
18%
525
73%
525
42%
867
July11th to 20thNight
73%
522
24%
1566
23%
522
76%
522
50%
768
July21st to endNight
73%
591
23%
1673
22%
558
75%
558
40%
926
August1st to 10thNight
69%
537
22%
1601
24%
534
72%
534
40%
882
August11th to 20thNight
70%
534
28%
1600
32%
534
73%
534
40%
895
August21st to endNight
72%
594
29%
1842
32%
594
75%
594
45%
938
September1st to 10thNight
62%
540
26%
1980
27%
540
69%
540
38%
976
September11th to 20thNight
55%
540
29%
1980
27%
540
65%
540
37%
986
September21st to endNight
56%
540
32%
1980
30%
540
64%
540
40%
941
October1st to 10thNight
49%
584
31%
2024
25%
584
56%
584
35%
1061
October11th to 20thNight
39%
720
33%
2160
15%
720
52%
720
44%
1117
October21st to endNight
40%
792
31%
2376
15%
792
51%
792
39%
1289
November1st to 10thNight
43%
887
32%
2367
13%
887
55%
887
48%
1263
November11th to 20thNight
37%
950
31%
2470
11%
950
49%
950
45%
1376
November21st to endNight
42%
950
28%
2470
13%
950
51%
950
38%
1470
December1st to 10thNight
38%
950
28%
2470
12%
950
49%
950
39%
1470
December11th to 20thNight
30%
949
30%
2874
10%
948
43%
948
31%
1659
December21st to endNight
32%
1043
18%
4447
12%
1026
45%
1026
20%
2815

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
9%6%25%5%3445%7%50%
78704
Night
9%6%25%42445%7%53%
80328
TransparencyDay
33%5%13%26%18%4
78429
Night
31%5%12%26%21%5%
80123
SeeingDay
11%8%28%31%18%4
14505
Night
11%8%33%35%11%1
24578

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
10%7%27%7%45%45%7%42%
2847
11th to 20thDay
8%8%47%7%4346%7%43%
2850
21st to endDay
10%12%38%423345%45%
3135
February1st to 10thDay
9%10%36%5%24445%48%
1701
11th to 20thDay
6%7%37%5%3445%7%48%
1745
21st to endDay
9%6%34425%46%7%50%
1480
March1st to 10thDay
8%6%245%35%5%5%7%50%
1921
11th to 20thDay
16%8%24423336%49%
1980
21st to endDay
14%8%36%43446%7%40%
2178
April1st to 10thDay
10%6%25%42345%6%53%
1980
11th to 20thDay
12%7%35%435%45%7%45%
2217
21st to endDay
15%7%345%3445%7%44%
2340
May1st to 10thDay
16%7%36%4345%5%6%41%
2340
11th to 20thDay
12%6%245%345%5%7%47%
2302
21st to endDay
13%7%35%6%445%6%9%38%
2531
June1st to 10thDay
6%324335%5%5%10%54%
2340
11th to 20thDay
6%3244345%5%9%55%
2340
21st to endDay
5%3145%3446%9%56%
2340
July1st to 10thDay
7%4245%345%5%10%50%
2340
11th to 20thDay
32134246%6%10%57%
2340
21st to endDay
7%325%5%45%6%7%9%48%
2546
August1st to 10thDay
6%425%5%36%6%7%11%45%
2328
11th to 20thDay
6%4245%35%5%5%8%54%
2301
21st to endDay
4323425%5%5%8%59%
2510
September1st to 10thDay
10%425%42445%6%55%
1980
11th to 20thDay
9%424435%45%7%53%
1980
21st to endDay
7%5%25%4245%5%6%56%
1980
October1st to 10thDay
11%43333435%7%54%
1918
11th to 20thDay
10%423313235%64%
1800
21st to endDay
12%6%34333345%56%
1980
November1st to 10thDay
6%42432335%6%62%
1708
11th to 20thDay
8%5%24323446%59%
1710
21st to endDay
13%414313245%59%
1710
December1st to 10thDay
9%5%244235%47%53%
1710
11th to 20thDay
9%6%36%4345%37%50%
2161
21st to endDay
10%10%411%6%3445%7%35%
3135
January1st to 10thNight
7%8%310%6%34446%45%
4108
11th to 20thNight
6%6%35%6%35%5%45%52%
4120
21st to endNight
15%10%35%313335%48%
4532
February1st to 10thNight
10%8%46%5%24445%47%
2464
11th to 20thNight
10%7%35%3345%5%7%49%
2117
21st to endNight
8%6%36%4335%46%53%
1776
March1st to 10thNight
9%6%2443345%7%53%
2037
11th to 20thNight
13%6%34433446%50%
1980
21st to endNight
16%7%35%5%34447%42%
2178
April1st to 10thNight
10%5%2342445%8%54%
1980
11th to 20thNight
12%6%244345%5%7%49%
1688
21st to endNight
13%6%25%5%35%35%5%48%
1620
May1st to 10thNight
16%7%24425%46%7%42%
1620
11th to 20thNight
11%5%2433446%8%51%
1593
21st to endNight
10%5%144345%7%10%47%
1745
June1st to 10thNight
5%3132245%7%11%55%
1620
11th to 20thNight
4213435%5%7%10%56%
1620
21st to endNight
4313425%45%8%61%
1620
July1st to 10thNight
7%3243345%5%9%54%
1620
11th to 20thNight
32133245%7%11%59%
1620
21st to endNight
6%3244345%8%12%49%
1772
August1st to 10thNight
4324446%5%7%9%53%
1611
11th to 20thNight
6%4245%35%5%6%9%52%
1600
21st to endNight
422442435%7%62%
1842
September1st to 10thNight
8%323333446%60%
1980
11th to 20thNight
7%43442445%6%59%
1980
21st to endNight
6%42332346%7%61%
1980
October1st to 10thNight
10%5%24433345%57%
2024
11th to 20thNight
10%413313336%63%
2160
21st to endNight
11%5%24322246%59%
2376
November1st to 10thNight
7%413323245%65%
2367
11th to 20thNight
8%423323446%61%
2470
21st to endNight
12%6%23223345%58%
2470
December1st to 10thNight
7%6%25%42445%7%54%
2470
11th to 20thNight
9%6%25%43435%7%53%
3036
21st to endNight
14%8%46%5%3345%7%40%
4532

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
42%411%24%17%2
2848
11th to 20thDay
40%416%24%11%5%
2850
21st to endDay
41%412%25%16%1
3135
February1st to 10thDay
38%6%12%25%13%5%
1701
11th to 20thDay
35%5%14%25%15%5%
1755
21st to endDay
33%411%26%22%4
1480
March1st to 10thDay
35%410%23%21%7%
1921
11th to 20thDay
39%310%23%20%5%
1980
21st to endDay
42%7%13%25%10%3
2178
April1st to 10thDay
32%5%13%25%20%4
1980
11th to 20thDay
39%6%11%26%16%3
2217
21st to endDay
40%6%11%28%14%1
2340
May1st to 10thDay
43%6%10%20%18%3
2340
11th to 20thDay
36%5%15%29%15%1
2306
21st to endDay
42%7%17%23%9%2
2531
June1st to 10thDay
25%7%18%30%16%3
2340
11th to 20thDay
26%6%15%28%20%5%
2340
21st to endDay
24%6%15%28%21%6%
2340
July1st to 10thDay
29%6%15%29%17%4
2276
11th to 20thDay
20%7%16%29%23%5%
2271
21st to endDay
29%7%14%31%18%1
2405
August1st to 10thDay
30%8%17%26%15%3
2314
11th to 20thDay
28%6%13%32%17%5%
2301
21st to endDay
23%7%13%28%21%9%
2510
September1st to 10thDay
30%5%12%24%21%8%
1980
11th to 20thDay
29%6%11%28%21%5%
1980
21st to endDay
28%6%9%26%25%7%
1980
October1st to 10thDay
30%5%11%24%26%4
1918
11th to 20thDay
25%38%26%29%9%
1800
21st to endDay
32%49%25%21%8%
1980
November1st to 10thDay
24%410%29%25%8%
1708
11th to 20thDay
27%49%27%28%5%
1710
21st to endDay
30%29%30%25%4
1710
December1st to 10thDay
31%412%33%19%2
1710
11th to 20thDay
35%310%29%19%3
2159
21st to endDay
48%5%11%24%11%2
3135
January1st to 10thNight
40%411%28%16%2
4108
11th to 20thNight
33%415%27%19%2
4120
21st to endNight
41%311%23%20%2
4532
February1st to 10thNight
39%412%23%16%5%
2464
11th to 20thNight
34%5%13%26%17%4
2117
21st to endNight
31%411%23%21%10%
1776
March1st to 10thNight
30%410%25%22%8%
2037
11th to 20thNight
36%411%24%20%6%
1980
21st to endNight
42%5%11%25%14%3
2178
April1st to 10thNight
29%5%13%23%24%6%
1980
11th to 20thNight
35%5%12%25%20%3
1688
21st to endNight
38%5%12%22%19%4
1620
May1st to 10thNight
40%6%15%19%17%3
1620
11th to 20thNight
31%6%18%29%15%1
1594
21st to endNight
33%6%22%26%11%2
1746
June1st to 10thNight
22%8%21%31%16%3
1620
11th to 20thNight
23%6%16%30%21%4
1620
21st to endNight
21%7%13%30%22%7%
1620
July1st to 10thNight
25%7%15%27%22%4
1575
11th to 20thNight
18%6%16%30%25%5%
1566
21st to endNight
25%8%15%31%19%2
1673
August1st to 10thNight
24%8%16%32%15%4
1601
11th to 20thNight
28%6%13%31%19%4
1600
21st to endNight
21%7%13%25%26%8%
1842
September1st to 10thNight
26%410%26%23%11%
1980
11th to 20thNight
26%5%12%24%27%5%
1980
21st to endNight
23%5%10%26%29%8%
1980
October1st to 10thNight
30%410%22%27%8%
2024
11th to 20thNight
23%48%27%29%9%
2160
21st to endNight
28%39%22%28%10%
2376
November1st to 10thNight
23%49%28%28%9%
2367
11th to 20thNight
24%49%29%29%5%
2470
21st to endNight
30%49%26%24%7%
2470
December1st to 10thNight
30%414%28%21%3
2470
11th to 20thNight
32%49%31%20%4
3037
21st to endNight
43%5%11%25%12%3
4532

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
12%12%36%26%12%1
270
11th to 20thDay
16%17%41%23%3
270
21st to endDay
9%11%48%29%3
297
February1st to 10thDay
16%16%42%21%31
267
11th to 20thDay
12%14%47%21%5%
240
21st to endDay
10%18%52%15%5%1
198
March1st to 10thDay
11%16%41%28%3
240
11th to 20thDay
21%13%37%23%7%
240
21st to endDay
17%15%45%19%31
264
April1st to 10thDay
13%18%38%24%7%
240
11th to 20thDay
13%15%42%25%5%
495
21st to endDay
19%16%36%18%10%2
600
May1st to 10thDay
17%11%35%26%9%1
603
11th to 20thDay
16%9%30%27%15%3
625
21st to endDay
17%6%30%26%18%4
679
June1st to 10thDay
6%321%37%25%8%
630
11th to 20thDay
7%329%38%20%2
630
21st to endDay
45%26%46%17%2
630
July1st to 10thDay
7%213%35%32%10%
621
11th to 20thDay
4214%41%33%7%
618
21st to endDay
6%111%39%34%7%
684
August1st to 10thDay
7%215%39%33%4
626
11th to 20thDay
7%113%40%34%6%
615
21st to endDay
4214%36%34%9%
629
September1st to 10thDay
13%37%37%33%7%
270
11th to 20thDay
6%216%40%30%6%
270
21st to endDay
13%328%29%20%7%
270
October1st to 10thDay
14%7%30%21%18%10%
270
11th to 20thDay
8%10%45%26%10%1
270
21st to endDay
18%15%31%24%10%3
297
November1st to 10thDay
10%12%31%33%12%1
270
11th to 20thDay
13%18%33%24%11%1
270
21st to endDay
20%10%33%25%10%2
270
December1st to 10thDay
10%10%36%33%8%3
270
11th to 20thDay
11%14%34%30%10%1
270
21st to endDay
18%15%42%21%4
297
January1st to 10thNight
9%11%39%35%6%
950
11th to 20thNight
10%13%40%30%7%
950
21st to endNight
12%11%39%34%5%
1045
February1st to 10thNight
15%10%43%28%4
948
11th to 20thNight
15%12%41%28%4
723
21st to endNight
12%14%41%30%4
592
March1st to 10thNight
11%12%43%30%3
597
11th to 20thNight
17%11%39%27%6%
540
21st to endNight
19%12%40%25%4
594
April1st to 10thNight
12%12%42%25%7%
540
11th to 20thNight
16%11%38%29%5%
533
21st to endNight
16%11%38%27%7%
540
May1st to 10thNight
19%8%34%31%7%
540
11th to 20thNight
14%7%30%36%12%1
531
21st to endNight
13%5%29%35%15%3
584
June1st to 10thNight
5%426%40%24%1
540
11th to 20thNight
5%334%44%14%
540
21st to endNight
4332%48%11%1
540
July1st to 10thNight
7%212%49%29%2
525
11th to 20thNight
3117%55%23%2
522
21st to endNight
7%112%47%31%2
591
August1st to 10thNight
5%217%49%26%1
537
11th to 20thNight
7%313%51%25%1
534
21st to endNight
4115%44%34%3
594
September1st to 10thNight
10%221%42%22%2
540
11th to 20thNight
7%328%40%21%1
540
21st to endNight
9%428%41%18%1
540
October1st to 10thNight
11%6%29%33%20%2
584
11th to 20thNight
12%7%39%33%8%
720
21st to endNight
14%9%35%33%9%1
792
November1st to 10thNight
9%8%37%34%12%1
887
11th to 20thNight
9%11%40%32%7%
950
21st to endNight
16%10%29%36%8%
950
December1st to 10thNight
11%9%37%36%7%
950
11th to 20thNight
15%10%39%32%4
950
21st to endNight
13%12%40%31%5%
1045
Page generated at 2024-02-07 05:11:58. Version ac07

Copyright 2024 Attilla Danko


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