Mabee Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mabee Observatory clear sky chart from 2005-11-05 to 2017-03-24.

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
45%
15338
25%
45270
15%
15292
54%
15292
37%
25503

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
35%
900
28%
2327
12%
895
46%
895
39%
1373
January16th to endNight
37%
960
32%
2496
13%
960
49%
960
43%
1424
February1st to 15thNight
32%
837
21%
2245
8%
833
40%
833
30%
1438
February16th to endNight
32%
632
28%
1894
10%
632
46%
632
35%
1052
March1st to 15thNight
33%
579
24%
2019
13%
579
46%
579
30%
1113
March16th to endNight
30%
555
20%
2035
13%
555
41%
555
25%
1180
April1st to 15thNight
34%
494
23%
1756
14%
494
50%
494
28%
959
April16th to endNight
34%
495
21%
1485
14%
495
45%
495
31%
892
May1st to 15thNight
35%
495
22%
1485
16%
495
46%
495
30%
905
May16th to endNight
50%
514
17%
1540
14%
513
56%
513
35%
910
June1st to 15thNight
52%
495
20%
1485
11%
495
59%
495
41%
792
June16th to endNight
60%
495
22%
1485
14%
495
66%
495
51%
725
July1st to 15thNight
69%
465
21%
1395
19%
465
71%
465
43%
752
July16th to endNight
77%
522
23%
1468
23%
489
80%
489
46%
758
August1st to 15thNight
75%
494
23%
1475
28%
491
76%
491
40%
812
August16th to endNight
69%
525
24%
1612
25%
525
72%
525
39%
881
September1st to 15thNight
55%
495
23%
1815
23%
495
63%
495
31%
989
September16th to endNight
59%
492
31%
1815
30%
492
65%
492
38%
875
October1st to 15thNight
47%
577
31%
1897
24%
577
54%
577
33%
1050
October16th to endNight
46%
704
33%
2112
16%
704
57%
704
49%
1049
November1st to 15thNight
44%
853
31%
2253
12%
853
55%
853
47%
1224
November16th to endNight
40%
900
29%
2340
11%
900
51%
900
42%
1344
December1st to 15thNight
35%
900
25%
2340
10%
900
45%
900
35%
1433
December16th to endNight
36%
960
27%
2496
12%
960
46%
960
33%
1573

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%5%2442445%7%50%
45665
Night
8%42332345%7%54%
45466
Cloud CoverDay
9%5%2442445%7%50%
45663
Night
8%42332345%7%54%
45466
TransparencyDay
32%5%13%27%17%4
45363
Night
29%413%26%20%5%
45271
SeeingDay
10%6%26%34%19%3
5062
Night
11%7%32%35%12%
15339

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 15thDay
7%5%1343335%5%55%
1611
16th to endDay
7%6%2432345%7%52%
1728
February1st to 15thDay
6%7%36%434447%48%
1627
16th to endDay
8%6%2431335%7%52%
1580
March1st to 15thDay
9%6%15%5%2435%8%46%
1941
16th to endDay
17%6%2332335%6%45%
2033
April1st to 15thDay
11%5%25%424446%48%
1858
16th to endDay
14%7%3442435%6%44%
2145
May1st to 15thDay
12%6%25%4245%5%6%43%
2136
16th to endDay
12%6%25%5%4445%7%40%
2222
June1st to 15thDay
7%32442445%9%50%
2145
16th to endDay
5%2133245%5%10%55%
2145
July1st to 15thDay
7%3244335%6%10%46%
2145
16th to endDay
5%213425%46%10%52%
2284
August1st to 15thDay
5%3245%35%5%6%9%48%
2145
16th to endDay
6%214325%45%8%52%
2235
September1st to 15thDay
9%425%42445%7%47%
1815
16th to endDay
7%414414446%56%
1815
October1st to 15thDay
12%422312347%54%
1722
16th to endDay
7%423323335%60%
1760
November1st to 15thDay
5%313423445%61%
1605
16th to endDay
10%413212235%61%
1620
December1st to 15thDay
12%7%24323336%49%
1620
16th to endDay
12%7%35%413446%46%
1728
January1st to 15thNight
7%5%24423445%55%
2327
16th to endNight
7%423313445%60%
2496
February1st to 15thNight
9%7%36%423445%48%
2235
16th to endNight
8%5%23422447%54%
1894
March1st to 15thNight
8%6%24424347%50%
2019
16th to endNight
14%6%24423346%47%
2035
April1st to 15thNight
10%42432445%7%50%
1756
16th to endNight
13%7%13324346%49%
1485
May1st to 15thNight
13%6%2332345%7%46%
1484
16th to endNight
8%4143336%6%11%47%
1539
June1st to 15thNight
5%31332346%10%54%
1485
16th to endNight
31132435%9%63%
1485
July1st to 15thNight
5%2143145%6%9%53%
1485
16th to endNight
4322345%7%11%53%
1576
August1st to 15thNight
4314435%5%7%8%53%
1485
16th to endNight
5%4235%2345%7%55%
1612
September1st to 15thNight
8%325%43345%6%52%
1815
16th to endNight
6%42331336%6%58%
1815
October1st to 15thNight
12%413322345%54%
1897
16th to endNight
8%312212236%65%
2112
November1st to 15thNight
7%313222337%62%
2253
16th to endNight
11%41321234460%
2340
December1st to 15thNight
9%6%3441335%7%50%
2340
16th to endNight
11%6%34424348%47%
2496

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
7%5%23433346%55%
1611
16th to endDay
7%5%25%32345%7%52%
1728
February1st to 15thDay
6%7%35%424446%49%
1627
16th to endDay
8%6%2431345%7%52%
1580
March1st to 15thDay
9%6%25%5%2445%7%46%
1941
16th to endDay
16%6%2432335%6%45%
2031
April1st to 15thDay
11%5%25%324446%48%
1858
16th to endDay
14%7%3442445%6%43%
2145
May1st to 15thDay
13%6%245%235%5%6%43%
2136
16th to endDay
12%6%25%6%3445%7%40%
2222
June1st to 15thDay
7%324434449%51%
2145
16th to endDay
5%234245%5%9%55%
2145
July1st to 15thDay
7%314425%5%5%10%46%
2145
16th to endDay
5%2134345%6%9%52%
2284
August1st to 15thDay
5%3145%35%5%6%10%47%
2145
16th to endDay
6%313425%5%5%8%52%
2235
September1st to 15thDay
9%425%415%45%7%48%
1815
16th to endDay
7%414324446%55%
1815
October1st to 15thDay
12%422213347%55%
1722
16th to endDay
7%423323335%60%
1760
November1st to 15thDay
5%323323445%61%
1605
16th to endDay
10%413212235%61%
1620
December1st to 15thDay
12%6%24323437%49%
1620
16th to endDay
12%7%35%313447%46%
1728
January1st to 15thNight
7%5%24414445%55%
2327
16th to endNight
7%423313345%60%
2496
February1st to 15thNight
9%7%35%424445%48%
2235
16th to endNight
7%5%24323447%53%
1894
March1st to 15thNight
8%6%24433446%51%
2019
16th to endNight
14%6%24423345%48%
2035
April1st to 15thNight
10%5%24424347%51%
1756
16th to endNight
13%6%23223346%49%
1485
May1st to 15thNight
13%6%2332346%7%46%
1484
16th to endNight
8%4143235%7%10%47%
1539
June1st to 15thNight
5%21422446%9%54%
1485
16th to endNight
31131435%9%63%
1485
July1st to 15thNight
6%2133245%6%9%53%
1485
16th to endNight
5%2123235%6%12%53%
1576
August1st to 15thNight
4213435%5%7%8%52%
1485
16th to endNight
6%32442445%7%55%
1612
September1st to 15thNight
8%3245%24446%52%
1815
16th to endNight
6%42331335%6%58%
1815
October1st to 15thNight
12%41332334454%
1897
16th to endNight
7%312212236%65%
2112
November1st to 15thNight
7%222213347%62%
2253
16th to endNight
10%422212345%60%
2340
December1st to 15thNight
10%6%25%314347%50%
2340
16th to endNight
11%6%24423347%47%
2496

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
29%413%31%18%2
1612
16th to endDay
29%317%30%15%3
1728
February1st to 15thDay
35%7%15%25%12%3
1628
16th to endDay
31%413%28%18%3
1580
March1st to 15thDay
37%410%24%19%3
1941
16th to endDay
39%5%12%25%14%3
2033
April1st to 15thDay
35%5%13%27%15%2
1858
16th to endDay
40%5%12%27%13%1
2145
May1st to 15thDay
39%5%12%23%17%1
2136
16th to endDay
40%6%14%22%12%2
2226
June1st to 15thDay
30%6%16%24%17%4
2145
16th to endDay
24%5%15%28%20%5%
2145
July1st to 15thDay
31%6%14%29%15%2
2006
16th to endDay
24%6%14%32%18%3
2129
August1st to 15thDay
29%6%16%25%16%5%
2131
16th to endDay
27%6%13%29%15%7%
2235
September1st to 15thDay
34%5%14%22%14%8%
1815
16th to endDay
27%5%10%30%20%4
1815
October1st to 15thDay
30%411%24%24%4
1722
16th to endDay
26%410%28%24%5%
1760
November1st to 15thDay
24%310%26%25%8%
1605
16th to endDay
27%29%32%23%4
1620
December1st to 15thDay
36%314%30%14%
1620
16th to endDay
39%312%26%15%3
1728
January1st to 15thNight
29%311%29%22%3
2327
16th to endNight
26%312%29%22%4
2496
February1st to 15thNight
37%5%13%24%14%4
2245
16th to endNight
30%314%27%18%6%
1894
March1st to 15thNight
33%311%24%19%7%
2019
16th to endNight
38%412%26%15%3
2035
April1st to 15thNight
32%411%24%23%3
1756
16th to endNight
36%314%22%19%3
1485
May1st to 15thNight
35%5%15%23%16%2
1485
16th to endNight
31%6%23%23%12%2
1541
June1st to 15thNight
24%5%18%29%18%3
1485
16th to endNight
17%6%15%31%22%5%
1485
July1st to 15thNight
23%6%14%29%20%4
1395
16th to endNight
22%5%15%31%22%2
1468
August1st to 15thNight
24%7%16%29%16%5%
1475
16th to endNight
27%5%13%25%20%7%
1612
September1st to 15thNight
31%5%13%22%17%9%
1815
16th to endNight
24%411%25%27%6%
1815
October1st to 15thNight
31%49%22%23%8%
1897
16th to endNight
21%29%28%31%6%
2112
November1st to 15thNight
22%49%25%28%9%
2253
16th to endNight
27%39%29%23%6%
2340
December1st to 15thNight
33%313%29%17%1
2340
16th to endNight
36%414%25%15%5%
2496

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
17%7%36%30%5%2
90
16th to endDay
15%10%47%23%11
96
February1st to 15thDay
5%18%46%22%6%
90
16th to endDay
312%49%24%7%2
81
March1st to 15thDay
12%13%48%24%1
90
16th to endDay
12%16%41%25%5%
75
April1st to 15thDay
9%14%35%28%12%
97
16th to endDay
17%13%37%22%8%
375
May1st to 15thDay
13%10%34%29%9%2
393
16th to endDay
16%5%30%28%15%3
437
June1st to 15thDay
9%427%38%19%1
420
16th to endDay
5%223%41%24%3
420
July1st to 15thDay
9%217%45%22%3
400
16th to endDay
5%10%41%35%6%
445
August1st to 15thDay
5%19%40%40%3
418
16th to endDay
6%115%36%33%6%
403
September1st to 15thDay
5%216%51%21%3
90
16th to endDay
10%222%27%24%13%
90
October1st to 15thDay
7%8%24%30%17%11%
90
16th to endDay
4440%28%16%6%
96
November1st to 15thDay
6%230%38%17%4
90
16th to endDay
26%17%31%18%41
90
December1st to 15thDay
14%12%37%26%6%2
90
16th to endDay
20%10%39%23%5%
96
January1st to 15thNight
9%11%38%33%6%
900
16th to endNight
10%8%40%34%6%
960
February1st to 15thNight
14%9%38%32%4
837
16th to endNight
11%12%40%31%4
632
March1st to 15thNight
11%10%41%30%5%
579
16th to endNight
17%10%39%27%5%
555
April1st to 15thNight
13%11%38%28%8%
494
16th to endNight
17%8%35%29%7%
495
May1st to 15thNight
16%6%35%30%8%1
495
16th to endNight
11%429%35%16%2
515
June1st to 15thNight
6%430%39%17%
495
16th to endNight
3130%48%15%
495
July1st to 15thNight
6%115%52%24%1
465
16th to endNight
6%10%49%31%1
522
August1st to 15thNight
5%110%52%28%1
494
16th to endNight
7%113%38%35%2
525
September1st to 15thNight
9%324%37%22%2
495
16th to endNight
8%425%39%21%1
492
October1st to 15thNight
16%5%27%30%19%1
577
16th to endNight
9%6%36%35%12%
704
November1st to 15thNight
8%8%35%34%12%
853
16th to endNight
13%9%34%33%8%
900
December1st to 15thNight
14%9%35%34%5%
900
16th to endNight
12%8%36%35%5%
960
Page generated at 2017-03-25 11:39:48. Version ac04

Copyright 2017 A. Danko


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