Maricopa Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Maricopa Observatory clear sky chart from 2005-11-05 to 2017-12-20.

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
75%
16055
39%
48063
33%
16017
81%
16017
57%
22078

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
75%
717
35%
2327
36%
716
80%
716
49%
1099
January16th to endNight
68%
768
38%
2496
37%
768
76%
768
46%
1213
February1st to 15thNight
72%
700
39%
2161
37%
699
80%
699
55%
983
February16th to endNight
65%
632
38%
1888
35%
632
72%
632
48%
947
March1st to 15thNight
66%
720
41%
1980
31%
720
76%
720
58%
954
March16th to endNight
73%
768
42%
2112
30%
768
82%
768
66%
961
April1st to 15thNight
62%
719
35%
1978
22%
719
72%
719
58%
941
April16th to endNight
63%
543
48%
1698
34%
543
78%
543
73%
638
May1st to 15thNight
70%
539
41%
1619
30%
539
78%
539
69%
649
May16th to endNight
72%
561
41%
1684
28%
561
80%
561
70%
682
June1st to 15thNight
76%
540
36%
1620
29%
540
79%
540
75%
641
June16th to endNight
87%
540
36%
1620
31%
540
89%
540
75%
652
July1st to 15thNight
79%
510
27%
1530
23%
510
81%
510
50%
765
July16th to endNight
81%
564
29%
1593
23%
531
83%
531
42%
859
August1st to 15thNight
84%
539
31%
1611
28%
536
84%
536
50%
795
August16th to endNight
81%
664
35%
1888
30%
664
81%
664
46%
1015
September1st to 15thNight
79%
720
34%
1980
28%
720
82%
720
53%
1019
September16th to endNight
83%
716
47%
1980
37%
716
89%
716
72%
868
October1st to 15thNight
80%
720
42%
2053
35%
720
85%
720
69%
900
October16th to endNight
84%
768
47%
2304
41%
768
90%
768
72%
939
November1st to 15thNight
83%
760
41%
2313
40%
760
87%
760
63%
1019
November16th to endNight
77%
780
43%
2535
43%
780
82%
780
56%
1104
December1st to 15thNight
76%
780
38%
2535
41%
780
79%
780
50%
1178
December16th to endNight
72%
787
39%
2558
40%
787
76%
787
45%
1257

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
2212213346%70%
48771
Night
3112212336%70%
48261
TransparencyDay
16%2311%25%40%
48466
Night
16%2211%23%43%
48067
SeeingDay
35%15%32%30%11%
5787
Night
3212%41%34%5%
16065

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
3313323345%66%
1611
16th to endDay
6%213213237%65%
1728
February1st to 15thDay
2213312347%68%
1697
16th to endDay
5%312323336%64%
1585
March1st to 15thDay
4212212335%70%
1980
16th to endDay
1112213245%71%
2112
April1st to 15thDay
112212246%72%
1970
16th to endDay
1111122482%
2259
May1st to 15thDay
111223480%
2331
16th to endDay
11111122384%
2429
June1st to 15thDay
1111111384%
2340
16th to endDay
1111113383%
2340
July1st to 15thDay
221332446%8%59%
2340
16th to endDay
33245%36%6%7%11%43%
2467
August1st to 15thDay
2213425%46%8%56%
2340
16th to endDay
21123235%6%8%60%
2310
September1st to 15thDay
32133245%46%62%
1980
16th to endDay
21121223379%
1980
October1st to 15thDay
21112235%77%
1905
16th to endDay
1211213479%
1920
November1st to 15thDay
112212236%75%
1873
16th to endDay
422212236%72%
1755
December1st to 15thDay
4313323346%63%
1755
16th to endDay
5%313323446%61%
1764
January1st to 15thNight
3213323345%66%
2327
16th to endNight
7%213213235%64%
2496
February1st to 15thNight
3311212236%69%
2152
16th to endNight
4213424345%63%
1888
March1st to 15thNight
4212212336%70%
1980
16th to endNight
211212236%75%
2112
April1st to 15thNight
2112213235%72%
1978
16th to endNight
1111112386%
1698
May1st to 15thNight
11112246%77%
1619
16th to endNight
111212284%
1684
June1st to 15thNight
111122482%
1620
16th to endNight
111121483%
1620
July1st to 15thNight
221233346%9%59%
1620
16th to endNight
3124426%6%7%12%47%
1701
August1st to 15thNight
21134246%7%9%56%
1620
16th to endNight
23135%345%5%8%57%
1888
September1st to 15thNight
22123235%6%8%61%
1980
16th to endNight
112112225%80%
1980
October1st to 15thNight
11121122478%
2053
16th to endNight
111112481%
2304
November1st to 15thNight
212212225%75%
2313
16th to endNight
3112212225%73%
2535
December1st to 15thNight
5%213213346%65%
2535
16th to endNight
5%314323246%62%
2558

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%1317%29%26%
1612
16th to endDay
21%2215%29%28%
1728
February1st to 15thDay
18%1417%29%29%
1697
16th to endDay
21%2214%33%25%
1585
March1st to 15thDay
17%117%30%40%
1980
16th to endDay
16%128%33%38%
2112
April1st to 15thDay
13%16%37%40%
1970
16th to endDay
9%17%23%57%
2259
May1st to 15thDay
9%16%23%57%
2331
16th to endDay
9%1423%60%
2432
June1st to 15thDay
9%215%71%
2340
16th to endDay
9%11210%75%
2340
July1st to 15thDay
20%37%16%19%32%
2201
16th to endDay
31%411%23%19%8%
2312
August1st to 15thDay
24%38%17%18%28%
2325
16th to endDay
19%36%18%27%25%
2310
September1st to 15thDay
23%2414%25%30%
1980
16th to endDay
11%15%25%55%
1980
October1st to 15thDay
11%127%27%49%
1905
16th to endDay
10%128%26%50%
1920
November1st to 15thDay
12%1112%33%38%
1873
16th to endDay
16%119%30%41%
1755
December1st to 15thDay
22%2315%29%26%
1755
16th to endDay
23%2423%32%14%
1764
January1st to 15thNight
21%2312%26%33%
2327
16th to endNight
23%1212%28%31%
2496
February1st to 15thNight
17%1315%24%37%
2163
16th to endNight
23%2213%26%32%
1888
March1st to 15thNight
16%27%23%48%
1980
16th to endNight
12%118%30%45%
2112
April1st to 15thNight
16%116%29%44%
1978
16th to endNight
6%16%20%64%
1698
May1st to 15thNight
8%15%24%58%
1620
16th to endNight
9%1416%67%
1685
June1st to 15thNight
8%1213%73%
1620
16th to endNight
8%1137%78%
1620
July1st to 15thNight
20%46%18%16%33%
1530
16th to endNight
26%49%24%21%13%
1593
August1st to 15thNight
20%39%19%17%29%
1611
16th to endNight
24%46%14%24%25%
1888
September1st to 15thNight
20%36%19%20%30%
1980
16th to endNight
9%15%22%59%
1980
October1st to 15thNight
11%119%21%54%
2053
16th to endNight
9%118%18%59%
2304
November1st to 15thNight
14%19%29%44%
2313
16th to endNight
17%118%25%46%
2535
December1st to 15thNight
20%2214%26%33%
2535
16th to endNight
23%2316%31%22%
2558

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
13%124%36%23%1
90
16th to endDay
45%12%37%27%13%
96
February1st to 15thDay
36%16%30%34%8%
212
16th to endDay
7%7%25%32%23%4
238
March1st to 15thDay
5%8%23%27%22%12%
270
16th to endDay
13%22%29%24%9%
288
April1st to 15thDay
5%11%26%29%20%7%
269
16th to endDay
217%26%33%15%4
270
May1st to 15thDay
211%27%34%17%6%
288
16th to endDay
16%22%42%21%6%
330
June1st to 15thDay
3325%38%23%6%
315
16th to endDay
218%38%33%15%
315
July1st to 15thDay
18%35%40%14%
305
16th to endDay
5%226%42%22%
327
August1st to 15thDay
2327%42%21%
315
16th to endDay
2426%43%22%
332
September1st to 15thDay
6%17%34%38%11%
315
16th to endDay
5%317%34%30%8%
315
October1st to 15thDay
2319%30%32%11%
240
16th to endDay
26%24%50%15%
144
November1st to 15thDay
329%34%39%10%
135
16th to endDay
8%314%32%31%9%
135
December1st to 15thDay
5%49%33%41%5%
135
16th to endDay
8%320%37%23%7%
108
January1st to 15thNight
5%11%51%27%3
720
16th to endNight
9%113%44%27%2
768
February1st to 15thNight
5%412%46%26%4
704
16th to endNight
6%218%49%20%3
632
March1st to 15thNight
5%419%37%28%4
720
16th to endNight
3415%40%31%5%
768
April1st to 15thNight
46%22%39%23%3
719
16th to endNight
16%26%39%22%3
543
May1st to 15thNight
16%20%42%25%3
540
16th to endNight
1420%42%28%2
563
June1st to 15thNight
1118%50%25%2
540
16th to endNight
8%51%35%3
540
July1st to 15thNight
39%35%42%8%
510
16th to endNight
3329%50%12%
564
August1st to 15thNight
2328%51%12%
539
16th to endNight
3327%52%11%
664
September1st to 15thNight
39%27%49%8%
720
16th to endNight
219%37%43%5%
716
October1st to 15thNight
2112%40%39%4
720
16th to endNight
117%37%44%7%
768
November1st to 15thNight
28%44%38%4
760
16th to endNight
419%41%37%5%
780
December1st to 15thNight
6%28%47%32%2
780
16th to endNight
7%38%48%28%3
787
Page generated at 2017-12-21 05:04:43. Version ac04

Copyright 2017 A. Danko


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