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 2017-04-25.

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%
15192
37%
45582
34%
15154
83%
15154
57%
21196

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
77%
525
45%
1656
40%
525
84%
525
75%
632
May1st to 15thNight
79%
494
41%
1484
34%
494
84%
494
71%
606
May16th to endNight
83%
513
38%
1540
31%
513
86%
513
72%
622
June1st to 15thNight
89%
495
37%
1485
33%
495
90%
495
73%
596
June16th to endNight
92%
495
33%
1485
30%
495
92%
495
76%
586
July1st to 15thNight
84%
465
26%
1395
22%
465
84%
465
48%
701
July16th to endNight
85%
522
28%
1467
24%
489
85%
489
44%
788
August1st to 15thNight
86%
494
32%
1476
28%
491
86%
491
47%
755
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
3212213346%69%
46049
Night
3212213346%69%
45779
TransparencyDay
16%2411%24%39%
45744
Night
17%2410%22%42%
45585
SeeingDay
4313%30%35%13%
4888
Night
48%42%38%4
15203

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%81%
2189
May1st to 15thDay
1111235%81%
2136
16th to endDay
21111112481%
2221
June1st to 15thDay
11111111483%
2145
16th to endDay
111123382%
2145
July1st to 15thDay
21143245%7%9%56%
2145
16th to endDay
43245%35%5%9%10%46%
2285
August1st to 15thDay
22123245%8%9%56%
2145
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
111122383%
1656
May1st to 15thNight
1122245%76%
1484
16th to endNight
2111112383%
1540
June1st to 15thNight
1111122482%
1485
16th to endNight
1111112482%
1485
July1st to 15thNight
1113435%5%7%10%56%
1485
16th to endNight
3212426%7%7%11%49%
1575
August1st to 15thNight
12124346%7%10%54%
1485
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%126%24%55%
2189
May1st to 15thDay
8%28%23%57%
2136
16th to endDay
9%125%23%57%
2224
June1st to 15thDay
9%1313%71%
2145
16th to endDay
8%12410%72%
2145
July1st to 15thDay
20%6%10%14%16%31%
2006
16th to endDay
26%7%13%22%19%10%
2130
August1st to 15thDay
20%6%9%18%17%27%
2130
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%25%20%62%
1656
May1st to 15thNight
10%135%24%55%
1485
16th to endNight
9%115%16%65%
1541
June1st to 15thNight
8%12311%72%
1485
16th to endNight
8%346%76%
1485
July1st to 15thNight
20%5%10%15%14%33%
1395
16th to endNight
22%7%12%19%22%15%
1467
August1st to 15thNight
20%6%9%18%14%29%
1476
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
28%27%38%18%6%
250
May1st to 15thDay
36%25%32%25%7%
228
16th to endDay
2214%42%30%8%
266
June1st to 15thDay
3313%35%33%10%
255
16th to endDay
115%30%46%15%
255
July1st to 15thDay
26%27%46%16%
245
16th to endDay
2316%48%28%
271
August1st to 15thDay
3220%47%25%
255
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
218%48%26%4
525
May1st to 15thNight
1114%47%31%2
495
16th to endNight
210%43%39%2
515
June1st to 15thNight
116%49%38%2
495
16th to endNight
1235%57%3
495
July1st to 15thNight
2430%56%6%
465
16th to endNight
4114%69%9%
522
August1st to 15thNight
2119%66%9%
494
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 2017-04-26 14:21:35. Version ac04

Copyright 2017 A. Danko


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