Mesa
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mesa clear sky chart from 2005-11-05 to 2017-08-12.

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
80%
15510
37%
46536
34%
15472
83%
15472
57%
21630

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
77%
718
32%
2327
34%
716
80%
716
48%
1107
January16th to endNight
72%
768
36%
2496
37%
768
77%
768
44%
1253
February1st to 15thNight
77%
698
36%
2180
37%
698
82%
698
55%
1007
February16th to endNight
72%
632
37%
1882
38%
632
75%
632
47%
968
March1st to 15thNight
74%
720
41%
1980
35%
720
79%
720
63%
936
March16th to endNight
79%
768
40%
2112
32%
768
85%
768
66%
968
April1st to 15thNight
76%
709
34%
1968
26%
709
81%
709
60%
947
April16th to endNight
75%
540
46%
1701
40%
540
84%
540
75%
648
May1st to 15thNight
79%
539
40%
1619
32%
539
84%
539
71%
661
May16th to endNight
82%
561
41%
1684
33%
561
86%
561
73%
675
June1st to 15thNight
89%
540
35%
1620
31%
540
90%
540
74%
649
June16th to endNight
92%
540
35%
1620
31%
540
92%
540
76%
637
July1st to 15thNight
86%
510
25%
1530
22%
510
86%
510
50%
756
July16th to endNight
83%
564
27%
1593
23%
531
84%
531
41%
886
August1st to 15thNight
85%
527
30%
1575
26%
524
85%
524
47%
808
August16th to endNight
85%
588
32%
1712
30%
588
85%
588
44%
942
September1st to 15thNight
82%
660
35%
1815
30%
660
84%
660
54%
941
September16th to endNight
86%
656
41%
1815
34%
656
89%
656
69%
818
October1st to 15thNight
83%
660
41%
1892
36%
660
85%
660
65%
850
October16th to endNight
87%
704
45%
2112
41%
704
90%
704
70%
884
November1st to 15thNight
85%
700
42%
2127
41%
700
87%
700
68%
892
November16th to endNight
80%
720
40%
2340
41%
720
84%
720
56%
1016
December1st to 15thNight
77%
720
37%
2340
39%
720
79%
720
49%
1096
December16th to endNight
72%
768
36%
2496
39%
768
74%
768
43%
1285

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
3212212346%69%
47431
Night
3212213346%69%
46733
TransparencyDay
16%2411%24%39%
47126
Night
16%2410%22%42%
46539
SeeingDay
4212%29%35%14%
5313
Night
48%41%39%4
15521

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
5%213222335%66%
1611
16th to endDay
7%313213235%65%
1728
February1st to 15thDay
3213312246%67%
1679
16th to endDay
5%313312237%62%
1591
March1st to 15thDay
4112213346%67%
1980
16th to endDay
3212312335%70%
2112
April1st to 15thDay
212213346%71%
1979
16th to endDay
111111125%80%
2256
May1st to 15thDay
1111235%81%
2331
16th to endDay
21111113481%
2429
June1st to 15thDay
1111111483%
2340
16th to endDay
111123382%
2340
July1st to 15thDay
21133245%7%9%58%
2340
16th to endDay
43245%35%6%9%10%45%
2467
August1st to 15thDay
23123245%8%9%56%
2290
16th to endDay
221332446%9%58%
2133
September1st to 15thDay
323324346%63%
1815
16th to endDay
11111212480%
1815
October1st to 15thDay
211212235%75%
1738
16th to endDay
12211225%80%
1760
November1st to 15thDay
1111212235%76%
1729
16th to endDay
422211225%73%
1620
December1st to 15thDay
5%313313335%63%
1620
16th to endDay
5%414313347%59%
1728
January1st to 15thNight
5%212323345%64%
2327
16th to endNight
8%21331333463%
2496
February1st to 15thNight
4312212346%68%
2170
16th to endNight
6%313423335%62%
1882
March1st to 15thNight
3212212345%70%
1980
16th to endNight
2112112235%74%
2112
April1st to 15thNight
3112312346%69%
1968
16th to endNight
11122384%
1701
May1st to 15thNight
1122245%77%
1619
16th to endNight
2111212383%
1684
June1st to 15thNight
1111122481%
1620
16th to endNight
11111125%81%
1620
July1st to 15thNight
11124245%7%10%56%
1620
16th to endNight
3213426%7%7%11%47%
1701
August1st to 15thNight
22124236%7%10%54%
1584
16th to endNight
2214435%6%6%9%54%
1712
September1st to 15thNight
221332446%8%61%
1815
16th to endNight
11111323476%
1815
October1st to 15thNight
222212235%74%
1892
16th to endNight
21121113479%
2112
November1st to 15thNight
211212235%75%
2127
16th to endNight
41322223472%
2340
December1st to 15thNight
7%23213245%65%
2340
16th to endNight
7%313323345%59%
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
21%25%14%27%28%
1612
16th to endDay
22%2315%25%30%
1728
February1st to 15thDay
18%25%17%27%28%
1679
16th to endDay
22%2414%30%24%
1591
March1st to 15thDay
17%237%29%39%
1980
16th to endDay
17%138%32%36%
2112
April1st to 15thDay
13%138%33%39%
1979
16th to endDay
9%127%24%55%
2256
May1st to 15thDay
8%128%23%56%
2331
16th to endDay
8%126%22%58%
2432
June1st to 15thDay
8%1315%70%
2340
16th to endDay
8%12410%73%
2340
July1st to 15thDay
18%5%9%14%17%32%
2201
16th to endDay
26%8%14%22%18%9%
2312
August1st to 15thDay
20%6%9%17%17%28%
2275
16th to endDay
19%5%7%18%27%20%
2133
September1st to 15thDay
20%37%12%23%31%
1815
16th to endDay
10%126%25%53%
1815
October1st to 15thDay
12%239%25%46%
1738
16th to endDay
9%147%27%49%
1760
November1st to 15thDay
10%1211%31%41%
1729
16th to endDay
16%1210%27%41%
1620
December1st to 15thDay
23%3415%28%23%
1620
16th to endDay
24%36%19%29%15%
1728
January1st to 15thNight
21%25%11%24%33%
2327
16th to endNight
25%2312%26%29%
2496
February1st to 15thNight
17%25%14%24%34%
2181
16th to endNight
25%1312%26%30%
1882
March1st to 15thNight
15%138%24%46%
1980
16th to endNight
12%138%31%41%
2112
April1st to 15thNight
15%227%27%43%
1968
16th to endNight
8%15%20%62%
1701
May1st to 15thNight
10%136%24%54%
1620
16th to endNight
9%116%16%65%
1685
June1st to 15thNight
8%12312%71%
1620
16th to endNight
8%246%76%
1620
July1st to 15thNight
19%5%10%16%14%34%
1530
16th to endNight
24%7%12%19%21%14%
1593
August1st to 15thNight
20%6%9%18%14%30%
1575
16th to endNight
24%6%7%14%23%23%
1712
September1st to 15thNight
19%38%17%19%30%
1815
16th to endNight
11%135%21%55%
1815
October1st to 15thNight
13%238%23%49%
1892
16th to endNight
10%138%17%57%
2112
November1st to 15thNight
12%138%26%47%
2127
16th to endNight
16%138%22%45%
2340
December1st to 15thNight
21%2414%27%30%
2340
16th to endNight
26%35%15%28%20%
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
23%17%41%22%4
90
16th to endDay
6%410%35%26%17%
96
February1st to 15thDay
5%114%33%38%6%
194
16th to endDay
8%424%34%21%5%
238
March1st to 15thDay
6%5%18%34%18%17%
270
16th to endDay
27%21%31%25%12%
288
April1st to 15thDay
5%7%21%31%25%9%
269
16th to endDay
29%27%36%18%5%
270
May1st to 15thDay
26%24%30%26%9%
288
16th to endDay
2216%40%31%8%
330
June1st to 15thDay
2213%33%34%13%
315
16th to endDay
427%46%19%
315
July1st to 15thDay
25%24%45%20%
305
16th to endDay
3315%44%33%
327
August1st to 15thDay
4218%47%27%
300
16th to endDay
119%55%22%
268
September1st to 15thDay
7%18%24%45%13%
255
16th to endDay
5%110%36%35%11%
255
October1st to 15thDay
3216%28%35%13%
178
16th to endDay
2318%54%21%
96
November1st to 15thDay
1111%28%41%16%
90
16th to endDay
8%210%38%35%4
90
December1st to 15thDay
31325%52%14%
90
16th to endDay
13%119%35%26%4
96
January1st to 15thNight
6%9%51%28%2
720
16th to endNight
10%110%49%25%2
768
February1st to 15thNight
5%110%50%28%3
704
16th to endNight
8%112%52%23%1
632
March1st to 15thNight
4115%47%26%4
720
16th to endNight
2212%45%32%5%
768
April1st to 15thNight
3213%50%28%1
709
16th to endNight
2119%47%25%3
540
May1st to 15thNight
1114%46%32%3
540
16th to endNight
211%42%39%2
563
June1st to 15thNight
116%49%39%1
540
16th to endNight
1234%58%3
540
July1st to 15thNight
2330%57%5%
510
16th to endNight
5%113%69%9%
564
August1st to 15thNight
3118%65%11%
527
16th to endNight
2220%64%10%
588
September1st to 15thNight
36%26%55%7%
660
16th to endNight
27%37%44%6%
656
October1st to 15thNight
38%46%38%1
660
16th to endNight
16%41%44%5%
704
November1st to 15thNight
27%47%37%4
700
16th to endNight
5%8%45%36%3
720
December1st to 15thNight
8%17%46%34%1
720
16th to endNight
9%19%49%27%2
768
Page generated at 2017-08-13 11:16:17. Version ac04

Copyright 2017 A. Danko


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