Marathon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Marathon clear sky chart from 2005-11-05 to 2017-04-28.

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
62%
14974
31%
45680
23%
14932
70%
14932
44%
23436

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
55%
719
34%
2151
23%
719
66%
719
42%
1144
January16th to endNight
56%
768
37%
2304
25%
768
67%
768
44%
1190
February1st to 15thNight
57%
703
35%
2108
22%
698
69%
698
48%
1043
February16th to endNight
50%
632
34%
1894
19%
632
63%
632
49%
913
March1st to 15thNight
51%
720
33%
2160
17%
720
65%
720
45%
1086
March16th to endNight
50%
622
35%
1996
22%
622
64%
622
43%
969
April1st to 15thNight
44%
539
34%
1798
21%
539
62%
539
42%
881
April16th to endNight
51%
534
36%
1780
26%
534
68%
534
47%
815
May1st to 15thNight
45%
494
27%
1649
20%
494
59%
494
39%
854
May16th to endNight
55%
514
24%
1568
21%
513
63%
513
37%
886
June1st to 15thNight
65%
495
26%
1485
24%
495
71%
495
53%
725
June16th to endNight
72%
495
21%
1485
21%
495
74%
495
43%
802
July1st to 15thNight
75%
465
21%
1491
22%
465
77%
465
41%
787
July16th to endNight
79%
522
24%
1631
29%
489
82%
489
40%
853
August1st to 15thNight
86%
494
28%
1639
34%
491
88%
491
49%
762
August16th to endNight
77%
525
22%
1750
25%
525
78%
525
32%
1016
September1st to 15thNight
76%
495
21%
1686
24%
495
77%
495
32%
964
September16th to endNight
73%
492
26%
1815
28%
492
74%
492
31%
985
October1st to 15thNight
69%
495
33%
1815
33%
495
72%
495
43%
839
October16th to endNight
69%
671
37%
2079
27%
671
76%
671
53%
975
November1st to 15thNight
69%
820
36%
2220
22%
820
74%
820
59%
1084
November16th to endNight
63%
900
37%
2340
20%
900
70%
900
53%
1219
December1st to 15thNight
62%
900
37%
2340
22%
900
67%
900
48%
1289
December16th to endNight
54%
960
36%
2496
19%
960
64%
960
48%
1355

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
5%31332445%7%59%
45978
Night
431232345%8%60%
45903
Cloud CoverDay
5%31332445%7%59%
45976
Night
431332345%7%60%
45903
TransparencyDay
23%5%9%19%24%18%
45698
Night
22%5%10%19%23%19%
45686
SeeingDay
6%6%23%34%23%5%
4659
Night
6%422%41%22%2
14981

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
8%423323335%60%
1790
16th to endDay
6%312413235%64%
1920
February1st to 15thDay
2212212346%68%
1750
16th to endDay
3212212337%69%
1580
March1st to 15thDay
242332445%6%59%
1800
16th to endDay
4313313335%65%
2223
April1st to 15thDay
4212323345%65%
2150
16th to endDay
3212223346%68%
2127
May1st to 15thDay
3323323447%61%
1971
16th to endDay
431221445%8%61%
2191
June1st to 15thDay
11112135%6%8%65%
2145
16th to endDay
5%2235%35%5%6%8%50%
2145
July1st to 15thDay
7%324435%6%7%8%45%
2035
16th to endDay
6%314436%5%7%10%45%
2109
August1st to 15thDay
3313435%6%6%10%50%
1980
16th to endDay
7%4245%5%6%6%7%9%39%
2100
September1st to 15thDay
10%5%25%6%45%46%8%39%
1944
16th to endDay
7%425%5%345%6%7%47%
1815
October1st to 15thDay
4313313337%63%
1815
16th to endDay
421221223470%
1790
November1st to 15thDay
6%2221223470%
1624
16th to endDay
5%31321222371%
1620
December1st to 15thDay
6%42213335%65%
1620
16th to endDay
4412414446%61%
1734
January1st to 15thNight
6%423323335%60%
2151
16th to endNight
6%312322447%60%
2304
February1st to 15thNight
3313322237%65%
2102
16th to endNight
5%212313446%64%
1894
March1st to 15thNight
3412324347%62%
2160
16th to endNight
4312223435%65%
1996
April1st to 15thNight
5%212423346%62%
1798
16th to endNight
2212223336%67%
1780
May1st to 15thNight
6%31242445%6%58%
1649
16th to endNight
5%413326%5%6%8%53%
1567
June1st to 15thNight
21123245%6%11%58%
1485
16th to endNight
32133246%8%11%52%
1485
July1st to 15thNight
5%213226%6%6%10%52%
1590
16th to endNight
4213335%5%6%10%53%
1751
August1st to 15thNight
31221448%14%54%
1650
16th to endNight
5%314425%5%9%12%44%
1750
September1st to 15thNight
6%4145%35%46%12%47%
1686
16th to endNight
7%4144345%6%10%48%
1815
October1st to 15thNight
5%212323446%62%
1815
16th to endNight
431222222471%
2079
November1st to 15thNight
4211112336%70%
2220
16th to endNight
5%312322235%68%
2340
December1st to 15thNight
5%312323447%62%
2340
16th to endNight
4412323336%64%
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%42332233460%
1790
16th to endDay
6%312413235%64%
1920
February1st to 15thDay
2212213346%68%
1750
16th to endDay
3312212337%68%
1580
March1st to 15thDay
242431445%7%59%
1800
16th to endDay
4313313335%65%
2221
April1st to 15thDay
4212313345%65%
2150
16th to endDay
3212223246%67%
2127
May1st to 15thDay
4223324446%61%
1971
16th to endDay
421222336%8%61%
2191
June1st to 15thDay
111221346%8%65%
2145
16th to endDay
5%213436%5%6%9%49%
2145
July1st to 15thDay
7%415%435%5%7%8%45%
2035
16th to endDay
6%314436%6%7%9%45%
2109
August1st to 15thDay
2213435%6%6%10%50%
1980
16th to endDay
7%4246%47%5%7%9%39%
2100
September1st to 15thDay
10%436%7%35%5%5%8%39%
1944
16th to endDay
7%425%5%4447%6%47%
1815
October1st to 15thDay
4312223337%64%
1815
16th to endDay
422312235%70%
1790
November1st to 15thDay
6%2131223470%
1624
16th to endDay
5%31321223371%
1620
December1st to 15thDay
6%42313336%64%
1620
16th to endDay
3412314446%61%
1734
January1st to 15thNight
5%423323335%60%
2151
16th to endNight
6%312322347%60%
2304
February1st to 15thNight
3313322247%65%
2102
16th to endNight
421221345%6%65%
1894
March1st to 15thNight
3413324347%62%
2160
16th to endNight
4312223446%64%
1996
April1st to 15thNight
5%312433347%61%
1798
16th to endNight
2213223336%67%
1780
May1st to 15thNight
5%413325%35%7%58%
1649
16th to endNight
6%313325%5%6%7%53%
1567
June1st to 15thNight
11123145%7%11%58%
1485
16th to endNight
32133237%8%11%51%
1485
July1st to 15thNight
4213326%5%7%10%52%
1590
16th to endNight
4213435%5%6%10%52%
1751
August1st to 15thNight
3122145%7%15%54%
1650
16th to endNight
5%324435%5%8%12%44%
1750
September1st to 15thNight
5%4245%25%46%11%47%
1686
16th to endNight
7%3144346%6%10%47%
1815
October1st to 15thNight
5%212323446%62%
1815
16th to endNight
431221213471%
2079
November1st to 15thNight
421112335%71%
2220
16th to endNight
5%31232223469%
2340
December1st to 15thNight
5%312323347%62%
2340
16th to endNight
4412323336%64%
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
27%35%16%30%16%
1791
16th to endDay
23%26%13%32%22%
1920
February1st to 15thDay
16%36%15%25%32%
1751
16th to endDay
17%1414%33%28%
1580
March1st to 15thDay
23%46%16%21%27%
1800
16th to endDay
21%35%12%26%30%
2223
April1st to 15thDay
19%47%10%23%34%
2150
16th to endDay
17%35%11%25%36%
2127
May1st to 15thDay
21%47%14%22%29%
1971
16th to endDay
19%410%21%24%19%
2194
June1st to 15thDay
14%5%10%22%28%17%
2145
16th to endDay
27%7%13%20%21%9%
2145
July1st to 15thDay
32%8%12%25%19%1
1906
16th to endDay
26%9%16%31%14%1
1966
August1st to 15thDay
22%8%15%31%19%2
1967
16th to endDay
35%9%16%22%12%2
2100
September1st to 15thDay
39%7%16%20%12%3
1944
16th to endDay
32%7%11%20%20%7%
1815
October1st to 15thDay
19%5%11%25%20%16%
1815
16th to endDay
17%35%15%27%30%
1790
November1st to 15thDay
17%26%21%30%21%
1624
16th to endDay
19%26%12%28%29%
1620
December1st to 15thDay
23%25%19%28%19%
1620
16th to endDay
22%35%19%33%15%
1734
January1st to 15thNight
26%35%16%28%19%
2151
16th to endNight
24%25%15%31%21%
2304
February1st to 15thNight
20%36%11%25%33%
2112
16th to endNight
18%37%11%28%30%
1894
March1st to 15thNight
22%27%16%21%28%
2160
16th to endNight
20%47%15%23%28%
1996
April1st to 15thNight
23%38%12%21%30%
1798
16th to endNight
17%47%16%23%30%
1780
May1st to 15thNight
24%5%8%16%19%25%
1650
16th to endNight
26%8%10%20%17%16%
1569
June1st to 15thNight
16%6%15%25%26%9%
1485
16th to endNight
22%8%17%22%20%8%
1485
July1st to 15thNight
22%8%19%29%16%2
1491
16th to endNight
21%9%17%32%17%1
1631
August1st to 15thNight
16%6%19%28%26%1
1639
16th to endNight
28%11%16%27%15%1
1750
September1st to 15thNight
29%9%22%24%11%3
1686
16th to endNight
30%6%15%20%18%7%
1815
October1st to 15thNight
20%5%13%25%18%16%
1815
16th to endNight
18%25%14%30%28%
2079
November1st to 15thNight
15%36%20%33%21%
2220
16th to endNight
19%26%11%26%33%
2340
December1st to 15thNight
23%36%19%25%22%
2340
16th to endNight
22%26%18%31%18%
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
14%5%34%32%13%
90
16th to endDay
9%19%28%22%17%2
96
February1st to 15thDay
46%22%26%30%10%
90
16th to endDay
9%14%25%34%12%2
81
March1st to 15thDay
5%5%37%32%13%5%
90
16th to endDay
417%42%24%7%3
255
April1st to 15thDay
418%47%24%4
269
16th to endDay
417%43%27%6%
259
May1st to 15thDay
416%46%29%3
228
16th to endDay
6%5%25%41%19%
406
June1st to 15thDay
221%36%34%5%
420
16th to endDay
5%15%33%39%5%
420
July1st to 15thDay
6%113%34%35%9%
300
16th to endDay
4110%41%30%11%
271
August1st to 15thDay
315%44%31%12%
255
16th to endDay
11%8%44%26%7%
268
September1st to 15thDay
7%19%42%26%10%
219
16th to endDay
13%322%42%18%
90
October1st to 15thDay
11%214%22%36%13%
90
16th to endDay
45%18%27%28%16%
96
November1st to 15thDay
10%7%24%36%14%6%
90
16th to endDay
13%12%23%34%12%4
90
December1st to 15thDay
12%5%17%40%22%2
90
16th to endDay
5%7%38%34%14%
96
January1st to 15thNight
8%425%39%19%1
723
16th to endNight
8%5%23%43%16%1
768
February1st to 15thNight
5%7%25%38%19%2
704
16th to endNight
6%7%33%42%10%
632
March1st to 15thNight
6%6%30%37%16%1
720
16th to endNight
5%9%30%36%16%1
622
April1st to 15thNight
5%8%38%39%7%
539
16th to endNight
28%35%43%8%
534
May1st to 15thNight
6%5%39%37%10%
495
16th to endNight
5%332%42%15%
515
June1st to 15thNight
2126%49%20%
495
16th to endNight
416%51%27%
495
July1st to 15thNight
6%11%49%29%1
465
16th to endNight
48%47%36%1
522
August1st to 15thNight
3344%44%3
494
16th to endNight
5%6%42%42%1
525
September1st to 15thNight
6%7%40%40%4
495
16th to endNight
8%10%44%33%2
492
October1st to 15thNight
5%118%44%28%1
495
16th to endNight
7%217%35%29%8%
671
November1st to 15thNight
5%219%39%27%6%
820
16th to endNight
7%418%38%25%5%
900
December1st to 15thNight
7%422%42%19%3
900
16th to endNight
7%7%26%41%15%1
960
Page generated at 2017-04-29 08:45:09. Version ac04

Copyright 2017 A. Danko


Marathon Clear Sky Chart | Charts Home