Marshall
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Marshall clear sky chart from 2005-11-05 to 2017-09-22.

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
55%
15377
23%
46978
19%
15341
60%
15341
31%
28264

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
57%
716
17%
2360
16%
716
61%
716
25%
1477
January16th to endNight
55%
768
24%
2496
25%
768
58%
768
27%
1549
February1st to 15thNight
49%
699
21%
2288
19%
699
55%
699
22%
1486
February16th to endNight
43%
632
19%
1928
14%
632
49%
632
22%
1278
March1st to 15thNight
48%
720
15%
1980
12%
720
51%
720
23%
1389
March16th to endNight
43%
768
20%
2112
13%
768
49%
768
27%
1403
April1st to 15thNight
42%
719
23%
1799
10%
719
49%
719
30%
1182
April16th to endNight
48%
720
26%
1800
10%
720
54%
720
39%
1088
May1st to 15thNight
54%
560
25%
1640
13%
560
62%
560
40%
906
May16th to endNight
51%
423
24%
1546
18%
423
60%
423
30%
827
June1st to 15thNight
54%
360
21%
1440
18%
360
63%
360
28%
761
June16th to endNight
72%
360
32%
1440
39%
360
77%
360
47%
594
July1st to 15thNight
71%
411
24%
1431
25%
411
73%
411
40%
694
July16th to endNight
59%
564
21%
1593
19%
531
64%
531
28%
969
August1st to 15thNight
58%
538
24%
1611
18%
535
61%
535
31%
965
August16th to endNight
65%
744
26%
1890
16%
744
66%
744
37%
1191
September1st to 15thNight
71%
720
32%
1800
21%
720
73%
720
44%
1072
September16th to endNight
68%
683
35%
1889
29%
683
74%
683
48%
1007
October1st to 15thNight
62%
660
27%
1980
26%
660
68%
660
39%
1105
October16th to endNight
65%
704
30%
2112
31%
704
69%
704
35%
1224
November1st to 15thNight
61%
700
25%
2154
24%
700
66%
700
34%
1253
November16th to endNight
56%
720
21%
2481
22%
720
60%
720
27%
1474
December1st to 15thNight
49%
720
20%
2520
17%
720
55%
720
21%
1647
December16th to endNight
43%
768
20%
2688
18%
768
50%
768
22%
1723

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%24323348%49%
47904
Night
11%6%25%423348%47%
47168
TransparencyDay
32%6%11%19%19%11%
47594
Night
35%5%9%18%19%12%
46979
SeeingDay
12%7%23%29%21%5%
6074
Night
13%5%16%28%28%8%
15388

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
18%5%34324346%42%
1577
16th to endDay
16%6%246%34345%42%
1728
February1st to 15thDay
18%6%24334445%41%
1576
16th to endDay
18%8%25%424348%36%
1544
March1st to 15thDay
18%7%25%5%3445%8%34%
1980
16th to endDay
16%6%25%42335%7%39%
2112
April1st to 15thDay
13%7%35%43445%5%41%
2149
16th to endDay
8%4233233410%53%
2160
May1st to 15thDay
6%5%33212348%57%
2307
16th to endDay
6%8%1432335%7%51%
2564
June1st to 15thDay
6%5%23313348%55%
2520
16th to endDay
2413222347%65%
2520
July1st to 15thDay
15%2331245%11%58%
2440
16th to endDay
27%2322436%13%51%
2468
August1st to 15thDay
37%2431345%10%52%
2340
16th to endDay
17%3432445%11%50%
2312
September1st to 15thDay
26%2332345%9%56%
2160
16th to endDay
5%412222346%63%
1881
October1st to 15thDay
8%5%13423246%56%
1650
16th to endDay
10%6%243135%48%48%
1760
November1st to 15thDay
9%5%2443445%8%48%
1703
16th to endDay
15%8%235%1433446%
1477
December1st to 15thDay
19%9%34423435%39%
1440
16th to endDay
22%7%34323236%39%
1536
January1st to 15thNight
16%5%244245%5%9%39%
2360
16th to endNight
18%6%14313347%44%
2496
February1st to 15thNight
18%6%3443435%5%39%
2276
16th to endNight
17%6%3442445%6%38%
1928
March1st to 15thNight
18%5%26%5%3435%7%36%
1980
16th to endNight
16%7%24423347%43%
2112
April1st to 15thNight
11%434424349%45%
1799
16th to endNight
8%5%23423337%56%
1800
May1st to 15thNight
45%23433347%57%
1640
16th to endNight
5%9%24313237%54%
1545
June1st to 15thNight
45%35%3146%5%9%50%
1440
16th to endNight
4312213237%66%
1440
July1st to 15thNight
2425%4244412%51%
1517
16th to endNight
29%37%5%46%6%6%13%34%
1701
August1st to 15thNight
211%5%8%43435%10%41%
1620
16th to endNight
19%37%5%2445%10%44%
1890
September1st to 15thNight
27%25%5%34449%52%
1800
16th to endNight
45%24312348%59%
1889
October1st to 15thNight
7%5%25%213347%55%
1980
16th to endNight
9%41442345%8%51%
2112
November1st to 15thNight
10%5%1342435%8%49%
2154
16th to endNight
12%5%24423345%49%
2481
December1st to 15thNight
21%5%25%423346%38%
2520
16th to endNight
20%5%25%5%13246%42%
2688

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
42%5%14%15%14%8%
1577
16th to endDay
44%5%7%13%18%11%
1728
February1st to 15thDay
44%6%7%20%17%4
1576
16th to endDay
46%5%9%22%11%3
1544
March1st to 15thDay
46%7%11%16%12%4
1980
16th to endDay
42%6%14%20%13%3
2112
April1st to 15thDay
42%6%14%19%15%2
2149
16th to endDay
27%6%15%25%20%5%
2160
May1st to 15thDay
24%6%10%25%24%7%
2307
16th to endDay
31%7%13%22%19%4
2568
June1st to 15thDay
27%6%13%22%19%10%
2520
16th to endDay
18%5%8%16%31%19%
2520
July1st to 15thDay
20%5%10%15%20%26%
2297
16th to endDay
24%8%11%15%16%23%
2313
August1st to 15thDay
24%7%9%15%23%19%
2324
16th to endDay
25%8%10%17%21%16%
2312
September1st to 15thDay
23%6%8%15%23%22%
2160
16th to endDay
20%5%8%22%26%17%
1881
October1st to 15thDay
29%48%19%24%13%
1650
16th to endDay
32%7%10%21%19%8%
1760
November1st to 15thDay
34%6%13%26%11%7%
1703
16th to endDay
41%5%11%18%18%5%
1477
December1st to 15thDay
47%6%10%15%17%3
1440
16th to endDay
47%5%10%16%14%5%
1536
January1st to 15thNight
40%5%12%19%14%8%
2360
16th to endNight
40%49%13%16%14%
2496
February1st to 15thNight
44%5%9%17%15%7%
2288
16th to endNight
43%6%12%20%14%3
1928
March1st to 15thNight
46%6%10%16%15%5%
1980
16th to endNight
41%5%10%20%16%4
2112
April1st to 15thNight
36%6%12%21%19%3
1799
16th to endNight
28%5%9%26%22%8%
1800
May1st to 15thNight
25%6%8%20%27%11%
1641
16th to endNight
31%49%26%21%6%
1546
June1st to 15thNight
27%9%11%18%20%12%
1440
16th to endNight
17%3414%33%25%
1440
July1st to 15thNight
23%5%5%7%25%33%
1431
16th to endNight
34%8%10%8%11%25%
1593
August1st to 15thNight
35%5%5%11%19%22%
1611
16th to endNight
31%7%6%10%21%22%
1890
September1st to 15thNight
27%5%5%11%24%25%
1800
16th to endNight
22%45%22%25%19%
1889
October1st to 15thNight
28%5%7%19%23%15%
1980
16th to endNight
30%5%7%20%21%13%
2112
November1st to 15thNight
31%5%13%27%14%7%
2154
16th to endNight
37%5%9%20%19%7%
2481
December1st to 15thNight
46%47%17%18%5%
2520
16th to endNight
44%410%16%17%6%
2688

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
28%6%20%24%16%3
206
16th to endDay
21%6%17%27%22%4
256
February1st to 15thDay
21%6%22%26%19%3
236
16th to endDay
19%9%26%26%15%2
231
March1st to 15thDay
26%8%28%17%14%5%
270
16th to endDay
20%11%34%24%7%2
288
April1st to 15thDay
18%16%30%22%9%2
269
16th to endDay
15%15%31%21%12%2
270
May1st to 15thDay
10%14%30%27%15%1
288
16th to endDay
16%9%24%23%18%7%
330
June1st to 15thDay
9%11%28%35%12%2
315
16th to endDay
25%24%41%22%3
315
July1st to 15thDay
2216%38%34%4
305
16th to endDay
3416%36%31%7%
327
August1st to 15thDay
5%420%37%27%5%
315
16th to endDay
1319%36%29%9%
332
September1st to 15thDay
5%216%33%31%10%
315
16th to endDay
5%7%18%32%26%10%
280
October1st to 15thDay
10%5%21%34%17%10%
255
16th to endDay
12%8%23%28%23%3
272
November1st to 15thDay
11%8%16%21%30%11%
209
16th to endDay
16%6%34%24%16%1
66
December1st to 15thDay
43%6%18%15%15%1
60
16th to endDay
17%17%10%25%25%4
64
January1st to 15thNight
18%412%29%27%7%
720
16th to endNight
19%5%14%25%27%7%
768
February1st to 15thNight
20%5%14%26%27%6%
704
16th to endNight
20%6%20%27%17%6%
632
March1st to 15thNight
20%8%15%26%24%5%
720
16th to endNight
19%7%22%28%18%2
768
April1st to 15thNight
12%9%26%29%17%4
719
16th to endNight
9%10%25%27%21%5%
720
May1st to 15thNight
6%227%31%26%5%
561
16th to endNight
8%6%22%34%21%6%
424
June1st to 15thNight
6%5%25%37%23%1
360
16th to endNight
5%215%43%28%4
360
July1st to 15thNight
4112%28%37%14%
411
16th to endNight
8%7%9%21%37%15%
564
August1st to 15thNight
8%312%28%34%12%
538
16th to endNight
6%210%29%39%11%
744
September1st to 15thNight
5%19%25%43%14%
720
16th to endNight
6%412%25%37%14%
683
October1st to 15thNight
9%315%28%32%10%
660
16th to endNight
12%311%25%32%14%
704
November1st to 15thNight
12%214%28%33%9%
700
16th to endNight
13%5%14%28%29%8%
720
December1st to 15thNight
24%314%26%23%7%
720
16th to endNight
21%6%20%27%20%2
768
Page generated at 2017-09-23 03:43:40. Version ac04

Copyright 2017 A. Danko


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