Marfa
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Marfa 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
62%
23764
33%
78821
24%
23667
71%
23667
45%
37550

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
55%
754
49%
3647
24%
736
69%
736
44%
1170
January11th to 20thNight
56%
756
48%
3579
24%
740
69%
740
45%
1171
January21st to endNight
49%
828
27%
3872
23%
814
66%
814
31%
1840
February1st to 10thNight
54%
758
40%
2274
23%
758
70%
758
52%
1072
February11th to 20thNight
48%
704
29%
2098
15%
700
61%
700
43%
1092
February21st to endNight
42%
592
37%
1776
18%
592
59%
592
47%
861
March1st to 10thNight
49%
720
34%
2160
17%
720
64%
720
46%
1084
March11th to 20thNight
47%
720
32%
2030
17%
720
58%
720
44%
1106
March21st to endNight
44%
621
42%
2007
23%
621
65%
621
51%
906
April1st to 10thNight
47%
540
39%
1800
23%
540
66%
540
44%
856
April11th to 20thNight
44%
533
34%
1777
20%
533
63%
533
45%
813
April21st to endNight
49%
540
40%
1800
26%
540
71%
540
55%
761
May1st to 10thNight
53%
540
33%
1800
24%
540
72%
540
49%
825
May11th to 20thNight
55%
531
28%
1770
28%
531
63%
531
42%
872
May21st to endNight
58%
582
28%
1811
25%
582
68%
582
44%
925
June1st to 10thNight
72%
540
26%
1620
25%
540
76%
540
50%
805
June11th to 20thNight
72%
540
28%
1620
26%
540
76%
540
44%
864
June21st to endNight
78%
540
28%
1648
28%
540
80%
540
44%
862
July1st to 10thNight
79%
525
17%
1750
20%
525
80%
525
37%
942
July11th to 20thNight
85%
522
26%
1740
30%
522
87%
522
47%
840
July21st to endNight
83%
591
24%
1859
28%
558
85%
558
43%
922
August1st to 10thNight
85%
537
26%
1779
30%
534
87%
534
47%
854
August11th to 20thNight
81%
534
23%
1778
28%
534
82%
534
37%
959
August21st to endNight
77%
594
20%
1980
23%
594
78%
594
32%
1125
September1st to 10thNight
78%
540
23%
1800
26%
540
78%
540
34%
994
September11th to 20thNight
79%
540
26%
1901
29%
540
79%
540
33%
1054
September21st to endNight
77%
540
30%
1980
31%
540
80%
540
39%
974
October1st to 10thNight
74%
540
32%
1980
32%
540
77%
540
45%
915
October11th to 20thNight
65%
661
36%
2101
26%
661
71%
661
46%
1041
October21st to endNight
69%
792
40%
2376
28%
792
76%
792
57%
1096
November1st to 10thNight
71%
756
40%
2236
27%
756
77%
756
60%
1010
November11th to 20thNight
66%
950
35%
2470
21%
950
72%
950
59%
1254
November21st to endNight
55%
950
38%
2470
20%
950
65%
950
53%
1297
December1st to 10thNight
62%
950
39%
2470
24%
950
68%
950
51%
1352
December11th to 20thNight
54%
948
37%
2896
20%
948
64%
948
45%
1514
December21st to endNight
56%
955
29%
4166
23%
946
69%
946
46%
1522

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
431342446%7%61%
78926
Night
431332446%8%62%
80096
TransparencyDay
22%48%19%27%21%
78676
Night
21%49%19%26%21%
79868
SeeingDay
5%6%20%30%27%13%
13497
Night
5%423%43%23%2
23796

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
3211212335%75%
3167
11th to 20thDay
3211213345%76%
3170
21st to endDay
3424424446%64%
3487
February1st to 10thDay
32134345%6%6%64%
1890
11th to 20thDay
431432435%7%64%
1749
21st to endDay
322333446%69%
1480
March1st to 10thDay
34244345%6%9%57%
1800
11th to 20thDay
5%42332445%6%60%
1926
21st to endDay
121332345%8%68%
2348
April1st to 10thDay
321332445%8%65%
2160
11th to 20thDay
2312324445%70%
2131
21st to endDay
4212223346%73%
2160
May1st to 10thDay
2312423445%70%
2160
11th to 20thDay
331342336%6%65%
2125
21st to endDay
32122235%7%8%66%
2456
June1st to 10thDay
1112325%6%6%8%66%
2340
11th to 20thDay
22133245%6%9%62%
2340
21st to endDay
4224436%5%8%9%53%
2303
July1st to 10thDay
6%426%6%47%8%9%9%40%
2160
11th to 20thDay
5%3135%36%7%8%9%49%
2160
21st to endDay
4235%5%47%7%8%11%44%
2349
August1st to 10thDay
42136%46%7%9%11%47%
2149
11th to 20thDay
7%5%26%7%5%8%7%9%9%34%
2123
21st to endDay
6%326%7%47%6%7%9%43%
2376
September1st to 10thDay
8%4346%46%6%7%8%45%
2160
11th to 20thDay
8%435%5%46%6%6%8%44%
2057
21st to endDay
5%5%2343445%7%57%
1980
October1st to 10thDay
32133235%5%6%65%
1980
11th to 20thDay
6%422323445%66%
1854
21st to endDay
5%312211225%76%
1980
November1st to 10thDay
4212212346%73%
1821
11th to 20thDay
2413313347%69%
1710
21st to endDay
6%41342335%6%65%
1710
December1st to 10thDay
5%42431345%7%61%
1710
11th to 20thDay
1324435%46%7%60%
2161
21st to endDay
321232336%6%69%
3294
January1st to 10thNight
2312222346%73%
3788
11th to 20thNight
321222335%6%73%
3800
21st to endNight
5%42443446%7%57%
4180
February1st to 10thNight
422232335%7%66%
2274
11th to 20thNight
4324435%5%6%7%58%
2098
21st to endNight
331332335%7%65%
1776
March1st to 10thNight
332442446%9%59%
2160
11th to 20thNight
45%233245%36%61%
2030
21st to endNight
3213323446%69%
2007
April1st to 10thNight
432343445%7%63%
1800
11th to 20thNight
3313325%447%66%
1777
21st to endNight
2212224336%72%
1800
May1st to 10thNight
321342445%7%66%
1800
11th to 20thNight
432342446%7%62%
1770
21st to endNight
3223425%5%6%8%59%
1811
June1st to 10thNight
3212325%6%7%11%57%
1620
11th to 20thNight
33145%26%7%8%11%51%
1620
21st to endNight
3214435%8%8%9%54%
1648
July1st to 10thNight
3324436%8%8%11%47%
1800
11th to 20thNight
3212325%6%7%12%57%
1800
21st to endNight
22235%45%5%9%12%52%
1969
August1st to 10thNight
32233347%9%14%51%
1790
11th to 20thNight
33245%45%6%9%14%45%
1778
21st to endNight
4325%5%46%7%7%11%46%
1980
September1st to 10thNight
6%4245%35%6%7%9%50%
1800
11th to 20thNight
6%4145%35%6%8%11%47%
1901
21st to endNight
32135%35%7%7%10%52%
1980
October1st to 10thNight
32134345%7%8%60%
1980
11th to 20thNight
6%31332345%7%62%
2101
21st to endNight
4312212335%73%
2376
November1st to 10thNight
5%212212246%73%
2236
11th to 20thNight
231322435%7%67%
2470
21st to endNight
421332435%6%66%
2470
December1st to 10thNight
6%213334447%62%
2470
11th to 20thNight
342443335%8%61%
3036
21st to endNight
2213213346%72%
4400

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
14%3213%30%38%
3168
11th to 20thDay
13%2414%44%23%
3170
21st to endDay
22%35%20%36%14%
3487
February1st to 10thDay
20%35%14%26%33%
1890
11th to 20thDay
21%26%15%28%28%
1759
21st to endDay
17%4212%31%34%
1480
March1st to 10thDay
24%4417%28%23%
1800
11th to 20thDay
24%3413%23%32%
1926
21st to endDay
16%3411%32%34%
2348
April1st to 10thDay
19%35%13%29%32%
2160
11th to 20thDay
17%3412%29%35%
2134
21st to endDay
15%2312%33%35%
2160
May1st to 10thDay
18%3311%27%38%
2160
11th to 20thDay
20%5%6%18%26%25%
2128
21st to endDay
15%5%7%21%24%28%
2456
June1st to 10thDay
15%410%23%28%19%
2340
11th to 20thDay
18%5%7%19%29%22%
2340
21st to endDay
25%7%11%22%22%14%
2303
July1st to 10thDay
35%9%15%24%13%3
2101
11th to 20thDay
29%7%13%25%21%6%
2097
21st to endDay
30%7%19%30%13%1
2219
August1st to 10thDay
26%8%14%31%19%2
2136
11th to 20thDay
41%8%16%22%10%2
2123
21st to endDay
35%7%18%20%15%5%
2376
September1st to 10thDay
35%6%14%20%16%9%
2160
11th to 20thDay
35%6%13%19%20%7%
2057
21st to endDay
28%5%8%22%24%12%
1980
October1st to 10thDay
19%410%26%22%19%
1980
11th to 20thDay
22%26%21%24%25%
1854
21st to endDay
15%2316%34%30%
1980
November1st to 10thDay
15%26%20%31%25%
1821
11th to 20thDay
17%26%22%30%22%
1710
21st to endDay
22%26%18%30%21%
1710
December1st to 10thDay
24%36%21%30%17%
1710
11th to 20thDay
22%45%19%33%18%
2159
21st to endDay
15%3215%35%30%
3294
January1st to 10thNight
14%3211%37%33%
3788
11th to 20thNight
13%3415%36%29%
3800
21st to endNight
25%45%18%34%13%
4180
February1st to 10thNight
19%25%16%26%33%
2274
11th to 20thNight
24%47%12%24%29%
2098
21st to endNight
20%348%28%37%
1776
March1st to 10thNight
22%3318%28%25%
2160
11th to 20thNight
25%3413%24%30%
2030
21st to endNight
18%35%14%28%33%
2007
April1st to 10thNight
21%4413%29%29%
1800
11th to 20thNight
20%38%13%24%32%
1777
21st to endNight
15%26%14%26%36%
1800
May1st to 10thNight
18%4414%25%35%
1800
11th to 20thNight
22%5%9%20%22%22%
1771
21st to endNight
22%5%11%22%17%22%
1812
June1st to 10thNight
19%6%12%28%22%13%
1620
11th to 20thNight
24%6%9%20%24%17%
1620
21st to endNight
23%6%13%23%21%13%
1648
July1st to 10thNight
26%8%22%28%13%3
1750
11th to 20thNight
20%6%16%30%24%5%
1740
21st to endNight
22%6%23%34%14%1
1859
August1st to 10thNight
18%7%20%34%19%2
1779
11th to 20thNight
27%7%24%29%11%2
1778
21st to endNight
30%8%18%22%16%6%
1980
September1st to 10thNight
29%7%17%23%15%9%
1800
11th to 20thNight
29%8%19%21%16%8%
1901
21st to endNight
24%5%15%22%21%11%
1980
October1st to 10thNight
20%5%16%21%19%18%
1980
11th to 20thNight
23%38%21%21%24%
2101
21st to endNight
16%2315%32%31%
2376
November1st to 10thNight
16%26%18%34%25%
2236
11th to 20thNight
17%36%21%29%24%
2470
21st to endNight
20%36%18%31%23%
2470
December1st to 10thNight
22%35%22%27%20%
2470
11th to 20thNight
23%3419%27%23%
3037
21st to endNight
16%2317%39%24%
4400

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
6%12%34%31%15%1
270
11th to 20thDay
412%28%36%18%2
270
21st to endDay
414%35%30%15%3
297
February1st to 10thDay
9%8%32%27%22%2
267
11th to 20thDay
8%12%35%28%15%2
240
21st to endDay
6%16%36%33%9%1
198
March1st to 10thDay
7%10%32%36%13%2
240
11th to 20thDay
9%14%37%23%14%4
366
21st to endDay
418%40%27%10%2
462
April1st to 10thDay
5%10%40%31%12%2
420
11th to 20thDay
315%44%26%8%3
412
21st to endDay
5%13%35%35%10%1
420
May1st to 10thDay
310%35%31%18%3
423
11th to 20thDay
36%31%37%20%3
448
21st to endDay
3224%43%26%2
604
June1st to 10thDay
2113%42%34%8%
630
11th to 20thDay
317%37%42%9%
630
21st to endDay
317%28%45%16%
593
July1st to 10thDay
5%5%23%38%29%
446
11th to 20thDay
21320%40%34%
444
21st to endDay
3323%44%26%
487
August1st to 10thDay
6%1215%38%37%
447
11th to 20thDay
6%25%19%37%31%
437
21st to endDay
6%1321%35%34%
495
September1st to 10thDay
7%1427%39%22%
450
11th to 20thDay
7%28%22%32%28%
347
21st to endDay
6%19%23%37%24%
270
October1st to 10thDay
7%39%25%39%18%
270
11th to 20thDay
7%316%29%29%15%
270
21st to endDay
6%7%19%29%25%14%
297
November1st to 10thDay
6%5%20%32%27%10%
270
11th to 20thDay
7%8%19%30%25%11%
270
21st to endDay
9%15%26%29%18%4
270
December1st to 10thDay
7%7%20%39%23%4
270
11th to 20thDay
212%32%36%17%1
270
21st to endDay
5%8%32%40%13%2
297
January1st to 10thNight
6%5%29%44%14%2
760
11th to 20thNight
7%427%43%17%1
760
21st to endNight
5%7%33%40%14%1
836
February1st to 10thNight
5%8%30%40%16%1
758
11th to 20thNight
7%6%35%41%11%
704
21st to endNight
5%10%39%40%6%
592
March1st to 10thNight
5%8%35%39%11%2
720
11th to 20thNight
7%8%34%37%13%2
720
21st to endNight
37%43%37%10%1
621
April1st to 10thNight
46%38%42%9%
540
11th to 20thNight
5%8%39%41%6%
533
21st to endNight
27%40%42%8%1
540
May1st to 10thNight
46%34%44%12%
540
11th to 20thNight
45%30%47%12%
531
21st to endNight
3330%49%15%
584
June1st to 10thNight
3217%59%19%
540
11th to 20thNight
4114%57%24%1
540
21st to endNight
3211%55%29%
540
July1st to 10thNight
46%44%43%3
525
11th to 20thNight
35%47%43%1
522
21st to endNight
21446%44%3
591
August1st to 10thNight
31335%53%5%
537
11th to 20thNight
31431%53%8%
534
21st to endNight
5%15%34%51%4
594
September1st to 10thNight
6%15%40%44%4
540
11th to 20thNight
6%16%43%42%2
540
21st to endNight
4110%44%39%2
540
October1st to 10thNight
3116%50%28%2
540
11th to 20thNight
9%218%44%24%3
661
21st to endNight
5%5%18%41%25%7%
792
November1st to 10thNight
6%217%43%26%5%
756
11th to 20thNight
3422%45%24%2
950
21st to endNight
5%6%29%39%20%3
950
December1st to 10thNight
7%422%45%19%2
950
11th to 20thNight
5%5%31%44%14%2
950
21st to endNight
47%28%45%13%2
965
Page generated at 2024-02-07 05:11:56. Version ac07

Copyright 2024 Attilla Danko


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