Marshall
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Marshall clear sky chart from 2005-11-06 to 2024-01-14.

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
54%
23645
24%
74830
20%
23598
60%
23598
30%
44880

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
48%
756
17%
2509
15%
756
53%
756
20%
1672
January11th to 20thNight
50%
734
19%
2384
16%
734
56%
734
24%
1524
January21st to endNight
53%
792
23%
2574
23%
792
57%
792
26%
1594
February1st to 10thNight
53%
720
24%
2340
22%
720
60%
720
28%
1419
February11th to 20thNight
45%
700
22%
2243
18%
700
52%
700
24%
1402
February21st to endNight
47%
592
24%
1767
18%
592
54%
592
30%
1059
March1st to 10thNight
42%
720
16%
1980
12%
720
46%
720
22%
1402
March11th to 20thNight
48%
720
21%
1980
17%
720
53%
720
26%
1333
March21st to endNight
42%
792
19%
2178
11%
792
49%
792
30%
1391
April1st to 10thNight
42%
720
23%
1800
10%
720
49%
720
31%
1190
April11th to 20thNight
44%
711
27%
1779
12%
711
51%
711
36%
1101
April21st to endNight
46%
720
28%
1800
10%
720
54%
720
43%
1045
May1st to 10thNight
49%
572
26%
1652
14%
572
57%
572
36%
948
May11th to 20thNight
53%
521
23%
1584
15%
521
60%
521
36%
889
May21st to endNight
46%
388
23%
1552
18%
388
57%
388
26%
829
June1st to 10thNight
56%
360
21%
1440
18%
360
65%
360
28%
763
June11th to 20thNight
60%
360
31%
1440
32%
360
70%
360
40%
627
June21st to endNight
66%
360
29%
1440
36%
360
70%
360
39%
660
July1st to 10thNight
66%
374
26%
1424
28%
374
71%
374
40%
657
July11th to 20thNight
68%
522
24%
1566
22%
522
70%
522
39%
849
July21st to endNight
57%
591
22%
1674
18%
558
58%
558
27%
1036
August1st to 10thNight
56%
537
23%
1602
18%
534
58%
534
30%
971
August11th to 20thNight
61%
592
24%
1660
15%
592
64%
592
34%
1001
August21st to endNight
63%
792
26%
1980
17%
792
64%
792
39%
1239
September1st to 10thNight
72%
720
36%
1800
22%
720
75%
720
52%
993
September11th to 20thNight
59%
720
31%
1819
20%
720
64%
720
39%
1125
September21st to endNight
67%
720
34%
2055
31%
720
73%
720
48%
1085
October1st to 10thNight
62%
720
28%
2160
26%
720
70%
720
44%
1129
October11th to 20thNight
62%
720
30%
2160
29%
720
67%
720
36%
1240
October21st to endNight
64%
792
33%
2376
33%
792
68%
792
38%
1342
November1st to 10thNight
59%
740
28%
2220
25%
740
64%
740
34%
1307
November11th to 20thNight
61%
760
24%
2493
25%
760
65%
760
28%
1490
November21st to endNight
59%
760
24%
2660
25%
760
64%
760
32%
1455
December1st to 10thNight
50%
760
21%
2660
19%
760
55%
760
24%
1656
December11th to 20thNight
47%
760
17%
3251
18%
759
53%
759
15%
2315
December21st to endNight
42%
827
13%
4828
18%
817
49%
817
12%
3142

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%3442445%8%50%
74680
Night
11%7%35%5%2445%7%47%
75089
TransparencyDay
31%7%12%19%19%12%
74402
Night
35%6%9%18%19%13%
74889
SeeingDay
11%9%23%30%20%7%
14286
Night
12%6%17%29%28%7%
23663

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 10thDay
21%7%37%5%2435%8%36%
1655
11th to 20thDay
16%6%36%5%34345%45%
1648
21st to endDay
14%7%35%7%35%45%7%40%
1782
February1st to 10thDay
18%6%3443444445%
1620
11th to 20thDay
12%7%36%5%3445%9%41%
1603
21st to endDay
16%6%2442435%7%47%
1488
March1st to 10thDay
18%8%36%5%3345%9%35%
1980
11th to 20thDay
18%8%35%425%5%6%7%37%
1980
21st to endDay
15%5%25%5%3446%8%43%
2178
April1st to 10thDay
14%8%46%5%4445%6%41%
2159
11th to 20thDay
8%5%3443445%7%52%
2129
21st to endDay
7%42332345%12%54%
2160
May1st to 10thDay
8%6%34323348%56%
2304
11th to 20thDay
7%5%2432345%9%55%
2308
21st to endDay
6%9%25%32445%7%52%
2723
June1st to 10thDay
7%7%3332345%10%53%
2520
11th to 20thDay
242332245%9%65%
2520
21st to endDay
26%24423348%61%
2520
July1st to 10thDay
27%2332345%11%58%
2491
11th to 20thDay
26%2432446%11%55%
2340
21st to endDay
16%3433446%14%52%
2546
August1st to 10thDay
38%26%5%245%6%10%51%
2328
11th to 20thDay
16%344245%6%12%54%
2240
21st to endDay
38%46%32346%11%50%
2376
September1st to 10thDay
25%2342335%10%61%
2160
11th to 20thDay
5%8%344335%5%9%52%
2138
21st to endDay
4422322346%67%
1904
October1st to 10thDay
6%423323247%63%
1800
11th to 20thDay
8%6%2442345%8%54%
1800
21st to endDay
10%6%2432345%9%52%
1980
November1st to 10thDay
10%5%25%43445%9%50%
1859
11th to 20thDay
13%7%35%5%2445%7%45%
1679
21st to endDay
11%6%2342445%6%51%
1520
December1st to 10thDay
16%7%35%43345%6%44%
1520
11th to 20thDay
27%9%5%5%5%335%45%29%
1928
21st to endDay
24%8%36%42435%8%34%
2794
January1st to 10thNight
18%8%35%435%5%6%9%35%
2509
11th to 20thNight
17%6%35%5%245%47%41%
2384
21st to endNight
16%7%25%42446%7%43%
2574
February1st to 10thNight
17%6%2443335%5%47%
2340
11th to 20thNight
13%6%46%5%3446%7%41%
2241
21st to endNight
15%6%2333445%6%50%
1767
March1st to 10thNight
20%7%36%6%34446%37%
1980
11th to 20thNight
17%8%35%43446%8%39%
1980
21st to endNight
16%8%24423346%48%
2178
April1st to 10thNight
11%7%45%5%33349%45%
1800
11th to 20thNight
10%7%34423337%54%
1779
21st to endNight
6%5%2442335%9%57%
1800
May1st to 10thNight
6%7%25%5%23435%57%
1652
11th to 20thNight
5%6%46%434348%53%
1583
21st to endNight
7%12%34423246%53%
1552
June1st to 10thNight
6%7%25%4245%5%10%49%
1440
11th to 20thNight
2435%414347%64%
1440
21st to endNight
47%35%313337%61%
1440
July1st to 10thNight
28%35%424339%57%
1465
11th to 20thNight
28%36%5%3445%12%48%
1620
21st to endNight
111%6%9%6%36%5%5%10%38%
1773
August1st to 10thNight
314%5%7%43435%8%44%
1611
11th to 20thNight
10%5%9%6%445%5%9%44%
1660
21st to endNight
212%47%5%23448%48%
1980
September1st to 10thNight
16%35%424447%60%
1800
11th to 20thNight
6%10%45%5%33348%50%
1819
21st to endNight
46%25%323346%61%
2055
October1st to 10thNight
6%6%26%313346%60%
2160
11th to 20thNight
7%6%37%434346%54%
2160
21st to endNight
9%5%25%5%2345%8%53%
2376
November1st to 10thNight
10%6%25%5%2445%8%49%
2220
11th to 20thNight
11%7%345%3446%7%46%
2493
21st to endNight
10%425%43445%7%53%
2660
December1st to 10thNight
18%7%35%5%2335%7%43%
2660
11th to 20thNight
29%7%35%5%2445%6%30%
3276
21st to endNight
21%8%36%6%34446%36%
4862

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
48%5%15%18%9%6%
1655
11th to 20thDay
43%6%9%15%17%11%
1648
21st to endDay
43%6%10%16%18%8%
1782
February1st to 10thDay
41%6%7%19%19%8%
1620
11th to 20thDay
39%7%10%19%19%6%
1612
21st to endDay
38%5%8%26%15%7%
1488
March1st to 10thDay
46%7%13%16%15%3
1980
11th to 20thDay
44%8%11%20%13%5%
1980
21st to endDay
37%8%15%22%15%3
2178
April1st to 10thDay
42%7%13%18%16%4
2159
11th to 20thDay
31%7%15%24%19%5%
2132
21st to endDay
24%6%17%28%20%4
2160
May1st to 10thDay
26%7%11%24%26%6%
2304
11th to 20thDay
26%8%13%26%21%7%
2311
21st to endDay
31%9%14%24%20%3
2724
June1st to 10thDay
28%7%12%26%22%6%
2520
11th to 20thDay
15%9%12%19%31%13%
2520
21st to endDay
19%8%11%14%27%21%
2520
July1st to 10thDay
18%7%12%17%20%27%
2423
11th to 20thDay
22%9%13%15%17%25%
2271
21st to endDay
20%10%15%13%17%25%
2405
August1st to 10thDay
24%8%12%15%21%20%
2312
11th to 20thDay
19%10%13%15%22%21%
2240
21st to endDay
26%8%11%17%20%18%
2376
September1st to 10thDay
17%6%8%16%23%30%
2160
11th to 20thDay
26%9%11%19%25%11%
2138
21st to endDay
16%8%9%20%28%19%
1904
October1st to 10thDay
22%410%17%27%19%
1800
11th to 20thDay
28%8%9%18%21%17%
1800
21st to endDay
29%6%10%18%21%15%
1980
November1st to 10thDay
31%7%11%26%16%9%
1859
11th to 20thDay
38%5%12%22%15%7%
1679
21st to endDay
33%6%12%20%19%10%
1520
December1st to 10thDay
41%7%10%18%17%8%
1520
11th to 20thDay
58%5%9%11%14%3
1928
21st to endDay
48%6%16%19%9%3
2794
January1st to 10thNight
45%7%13%20%10%5%
2509
11th to 20thNight
42%6%11%16%13%13%
2384
21st to endNight
40%5%13%13%19%10%
2574
February1st to 10thNight
38%5%9%20%18%11%
2340
11th to 20thNight
40%6%9%19%19%7%
2243
21st to endNight
35%5%12%24%19%5%
1767
March1st to 10thNight
48%6%10%16%15%4
1980
11th to 20thNight
43%6%8%22%17%5%
1980
21st to endNight
37%7%12%22%17%5%
2178
April1st to 10thNight
36%8%11%21%20%5%
1800
11th to 20thNight
30%6%11%25%20%8%
1779
21st to endNight
25%5%10%30%23%7%
1800
May1st to 10thNight
28%7%7%21%28%9%
1652
11th to 20thNight
28%7%9%24%25%7%
1584
21st to endNight
32%6%12%25%22%4
1552
June1st to 10thNight
28%9%10%18%28%6%
1440
11th to 20thNight
19%6%8%19%30%18%
1440
21st to endNight
21%7%5%12%29%26%
1440
July1st to 10thNight
20%7%6%8%25%34%
1424
11th to 20thNight
25%7%8%12%18%30%
1566
21st to endNight
36%9%8%7%11%28%
1674
August1st to 10thNight
36%7%5%11%19%22%
1602
11th to 20thNight
31%8%8%9%18%25%
1660
21st to endNight
31%7%7%11%20%25%
1980
September1st to 10thNight
20%6%6%9%28%32%
1800
11th to 20thNight
30%7%7%18%25%13%
1819
21st to endNight
21%5%6%20%25%22%
2055
October1st to 10thNight
23%5%9%15%26%22%
2160
11th to 20thNight
29%7%7%17%18%22%
2160
21st to endNight
28%6%7%19%21%18%
2376
November1st to 10thNight
33%6%10%24%16%11%
2220
11th to 20thNight
35%7%10%24%16%8%
2493
21st to endNight
32%5%11%19%22%11%
2660
December1st to 10thNight
41%6%8%18%17%10%
2660
11th to 20thNight
55%5%10%14%14%4
3276
21st to endNight
49%7%13%17%11%3
4862

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
27%11%25%19%15%3
316
11th to 20thDay
23%7%22%28%17%3
350
21st to endDay
15%8%23%29%21%3
374
February1st to 10thDay
16%10%22%27%20%6%
340
11th to 20thDay
15%16%27%24%15%3
348
21st to endDay
17%11%27%26%17%1
346
March1st to 10thDay
22%13%29%24%11%2
420
11th to 20thDay
24%11%25%22%12%5%
420
21st to endDay
16%12%35%26%9%2
462
April1st to 10thDay
17%16%30%23%11%4
420
11th to 20thDay
14%14%34%23%11%5%
412
21st to endDay
9%16%30%26%14%5%
420
May1st to 10thDay
10%15%30%29%14%3
423
11th to 20thDay
12%13%30%27%14%4
448
21st to endDay
12%12%26%26%17%7%
485
June1st to 10thDay
8%11%26%34%14%7%
450
11th to 20thDay
414%26%38%15%4
450
21st to endDay
25%26%36%25%6%
450
July1st to 10thDay
47%20%41%22%5%
446
11th to 20thDay
2118%41%27%11%
444
21st to endDay
2315%46%24%10%
487
August1st to 10thDay
46%22%37%23%9%
447
11th to 20thDay
3321%35%28%10%
437
21st to endDay
6%415%37%28%9%
495
September1st to 10thDay
3416%37%29%11%
450
11th to 20thDay
5%6%22%34%24%8%
450
21st to endDay
48%20%33%26%9%
450
October1st to 10thDay
7%7%22%28%23%14%
450
11th to 20thDay
8%8%17%27%27%13%
450
21st to endDay
13%8%17%28%24%10%
495
November1st to 10thDay
11%9%17%28%27%9%
455
11th to 20thDay
10%8%14%25%26%17%
258
21st to endDay
11%7%21%28%23%11%
180
December1st to 10thDay
22%10%16%19%22%11%
180
11th to 20thDay
22%8%21%22%21%7%
180
21st to endDay
19%14%20%27%19%2
198
January1st to 10thNight
19%6%16%28%24%6%
760
11th to 20thNight
19%6%16%30%24%5%
734
21st to endNight
17%6%15%31%28%4
792
February1st to 10thNight
19%5%14%30%27%4
720
11th to 20thNight
15%7%21%28%23%6%
704
21st to endNight
17%9%20%30%20%3
592
March1st to 10thNight
21%9%17%27%21%4
720
11th to 20thNight
18%8%17%33%20%3
720
21st to endNight
17%9%25%29%16%3
792
April1st to 10thNight
13%7%28%30%18%4
720
11th to 20thNight
11%10%27%28%18%6%
711
21st to endNight
7%10%31%25%21%6%
720
May1st to 10thNight
8%7%26%30%23%6%
572
11th to 20thNight
7%324%34%27%5%
521
21st to endNight
9%9%23%30%22%6%
389
June1st to 10thNight
9%6%23%34%26%3
360
11th to 20thNight
25%22%42%26%3
360
21st to endNight
6%315%38%33%5%
360
July1st to 10thNight
3317%32%36%9%
374
11th to 20thNight
6%111%22%41%19%
522
21st to endNight
5%310%26%43%14%
591
August1st to 10thNight
10%414%26%34%12%
537
11th to 20thNight
4311%29%41%12%
592
21st to endNight
7%311%26%43%10%
792
September1st to 10thNight
3211%28%44%13%
720
11th to 20thNight
9%413%29%35%10%
720
21st to endNight
5%5%13%28%37%13%
720
October1st to 10thNight
8%415%27%33%13%
720
11th to 20thNight
8%5%13%25%39%11%
720
21st to endNight
11%411%26%33%14%
792
November1st to 10thNight
11%414%26%33%11%
740
11th to 20thNight
13%411%33%31%8%
760
21st to endNight
12%416%34%28%6%
760
December1st to 10thNight
20%416%30%24%6%
760
11th to 20thNight
25%6%15%28%22%3
760
21st to endNight
21%8%21%31%18%2
836
Page generated at 2024-01-11 01:22:40. Version ac07

Copyright 2024 Attilla Danko


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