Desert Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Desert Center clear sky chart from 2005-11-06 to 2024-01-12.

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
73%
24631
41%
74343
32%
24586
82%
24586
63%
32056

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
68%
760
37%
2457
32%
756
78%
756
51%
1110
January11th to 20thNight
68%
724
39%
2353
33%
724
80%
724
51%
1060
January21st to endNight
59%
792
43%
2426
29%
792
77%
792
50%
1138
February1st to 10thNight
65%
720
42%
2160
32%
720
78%
720
54%
979
February11th to 20thNight
62%
700
40%
2098
32%
700
76%
700
53%
971
February21st to endNight
56%
592
41%
1776
33%
592
71%
592
53%
814
March1st to 10thNight
59%
720
35%
2160
27%
720
73%
720
53%
984
March11th to 20thNight
67%
720
41%
1986
31%
720
79%
720
61%
909
March21st to endNight
62%
792
40%
2178
24%
792
76%
792
60%
1010
April1st to 10thNight
64%
720
41%
1837
23%
720
74%
720
64%
872
April11th to 20thNight
61%
711
43%
1779
20%
711
73%
711
71%
817
April21st to endNight
68%
653
47%
1733
24%
653
80%
653
78%
730
May1st to 10thNight
67%
540
47%
1620
30%
540
76%
540
78%
603
May11th to 20thNight
74%
531
45%
1595
31%
531
81%
531
75%
611
May21st to endNight
71%
582
42%
1746
30%
582
78%
582
80%
650
June1st to 10thNight
77%
540
38%
1620
30%
540
81%
540
76%
627
June11th to 20thNight
79%
540
42%
1620
33%
540
84%
540
87%
582
June21st to endNight
81%
540
38%
1620
31%
540
84%
540
75%
640
July1st to 10thNight
89%
525
35%
1575
30%
525
90%
525
72%
647
July11th to 20thNight
87%
522
35%
1566
29%
522
88%
522
60%
704
July21st to endNight
87%
591
36%
1674
30%
558
87%
558
54%
793
August1st to 10thNight
87%
620
39%
1685
26%
617
89%
617
72%
742
August11th to 20thNight
91%
712
40%
1780
27%
712
91%
712
72%
852
August21st to endNight
92%
792
44%
1980
32%
792
92%
792
74%
933
September1st to 10thNight
87%
720
41%
1898
32%
720
90%
720
71%
869
September11th to 20thNight
89%
720
49%
1980
41%
720
94%
720
87%
779
September21st to endNight
84%
720
47%
1980
38%
720
91%
720
81%
816
October1st to 10thNight
78%
720
44%
1980
35%
720
85%
720
68%
880
October11th to 20thNight
81%
720
51%
1989
43%
720
89%
720
80%
815
October21st to endNight
78%
792
46%
2439
40%
792
88%
792
73%
928
November1st to 10thNight
78%
740
43%
2405
39%
740
89%
740
69%
919
November11th to 20thNight
77%
760
42%
2470
39%
760
87%
760
65%
986
November21st to endNight
69%
760
41%
2470
38%
760
79%
760
56%
1054
December1st to 10thNight
68%
760
39%
2470
36%
760
76%
760
51%
1134
December11th to 20thNight
66%
758
38%
2902
32%
758
77%
758
42%
1343
December21st to endNight
61%
822
25%
4336
32%
817
74%
817
34%
1755

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
2112212345%77%
74873
Night
2112212345%77%
74873
TransparencyDay
11%3312%25%46%
74600
Night
12%3312%26%45%
74668
SeeingDay
39%21%35%26%7%
14303
Night
25%16%37%34%6%
24653

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
231232445%6%68%
1708
11th to 20thDay
411222335%6%71%
1629
21st to endDay
2322223446%69%
1929
February1st to 10thDay
2212314436%73%
1800
11th to 20thDay
211322345%8%70%
1750
21st to endDay
2312223346%73%
1480
March1st to 10thDay
221122245%9%71%
1800
11th to 20thDay
2112222347%74%
1971
21st to endDay
1111113345%78%
2178
April1st to 10thDay
1112323346%74%
2118
11th to 20thDay
211111222483%
2129
21st to endDay
11111235%84%
2225
May1st to 10thDay
111111235%83%
2340
11th to 20thDay
1111112487%
2301
21st to endDay
111122389%
2530
June1st to 10thDay
111111225%86%
2340
11th to 20thDay
111112291%
2340
21st to endDay
111111122386%
2340
July1st to 10thDay
1111212335%78%
2340
11th to 20thDay
2112223347%74%
2340
21st to endDay
321443446%8%61%
2545
August1st to 10thDay
2112222335%76%
2240
11th to 20thDay
2112313346%75%
2122
21st to endDay
2212212345%77%
2376
September1st to 10thDay
2212312346%75%
2062
11th to 20thDay
1111111390%
1980
21st to endDay
111111223383%
1980
October1st to 10thDay
11121233481%
1980
11th to 20thDay
1111112488%
1968
21st to endDay
121223384%
1913
November1st to 10thDay
1111112235%82%
1674
11th to 20thDay
1111222345%79%
1710
21st to endDay
211222335%6%74%
1710
December1st to 10thDay
3313323448%66%
1710
11th to 20thDay
22133345%7%8%61%
2169
21st to endDay
5%3122235%7%8%62%
3146
January1st to 10thNight
22123235%5%7%68%
2457
11th to 20thNight
221232445%6%70%
2353
21st to endNight
4212324445%70%
2426
February1st to 10thNight
2112324345%73%
2160
11th to 20thNight
3312223436%72%
2098
21st to endNight
2212223448%70%
1776
March1st to 10thNight
221232445%7%70%
2160
11th to 20thNight
2112223335%76%
1986
21st to endNight
1111223447%74%
2178
April1st to 10thNight
1111213345%77%
1837
11th to 20thNight
111111223384%
1779
21st to endNight
112235%86%
1733
May1st to 10thNight
111112488%
1620
11th to 20thNight
111222387%
1594
21st to endNight
111111390%
1746
June1st to 10thNight
11111123387%
1620
11th to 20thNight
112390%
1620
21st to endNight
111121122385%
1620
July1st to 10thNight
1111112335%81%
1620
11th to 20thNight
2113224346%72%
1620
21st to endNight
221332337%7%66%
1773
August1st to 10thNight
111121223481%
1694
11th to 20thNight
1111122347%78%
1780
21st to endNight
2111112335%80%
1980
September1st to 10thNight
2212112236%79%
1898
11th to 20thNight
11112391%
1980
21st to endNight
1111112388%
1980
October1st to 10thNight
221221223480%
1980
11th to 20thNight
11111112387%
1989
21st to endNight
111223485%
2439
November1st to 10thNight
1121333483%
2405
11th to 20thNight
2111222335%79%
2470
21st to endNight
3213222336%74%
2470
December1st to 10thNight
3313323346%69%
2470
11th to 20thNight
23133235%5%10%62%
3041
21st to endNight
4212325%5%6%8%64%
4521

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
17%5%5%18%33%22%
1709
11th to 20thDay
16%4315%35%27%
1629
21st to endDay
17%3414%33%28%
1929
February1st to 10thDay
14%35%12%27%38%
1800
11th to 20thDay
14%4314%29%36%
1760
21st to endDay
14%4416%28%34%
1480
March1st to 10thDay
14%4315%30%35%
1800
11th to 20thDay
12%4314%31%36%
1971
21st to endDay
11%3315%35%33%
2178
April1st to 10thDay
14%3312%31%38%
2118
11th to 20thDay
9%227%32%49%
2132
21st to endDay
6%2210%31%50%
2225
May1st to 10thDay
7%229%29%51%
2340
11th to 20thDay
6%127%25%60%
2304
21st to endDay
5%228%26%59%
2530
June1st to 10thDay
6%215%22%65%
2340
11th to 20thDay
311313%79%
2340
21st to endDay
7%1139%78%
2340
July1st to 10thDay
11%336%14%63%
2276
11th to 20thDay
12%45%13%28%38%
2271
21st to endDay
20%5%6%19%20%30%
2404
August1st to 10thDay
12%3410%22%49%
2225
11th to 20thDay
11%3311%27%43%
2122
21st to endDay
12%2311%24%48%
2376
September1st to 10thDay
13%35%10%19%50%
2062
11th to 20thDay
5%116%20%68%
1980
21st to endDay
8%226%21%61%
1980
October1st to 10thDay
10%2210%23%52%
1980
11th to 20thDay
5%228%23%60%
1968
21st to endDay
8%228%20%59%
1913
November1st to 10thDay
8%2211%30%47%
1674
11th to 20thDay
11%2311%29%45%
1710
21st to endDay
13%3413%29%38%
1710
December1st to 10thDay
19%4417%26%31%
1710
11th to 20thDay
20%5%7%25%25%18%
2168
21st to endDay
19%5%7%24%28%16%
3146
January1st to 10thNight
16%5%416%32%27%
2457
11th to 20thNight
16%4311%33%31%
2353
21st to endNight
19%2419%22%34%
2426
February1st to 10thNight
16%3312%28%39%
2160
11th to 20thNight
17%2312%27%39%
2099
21st to endNight
15%4312%30%36%
1776
March1st to 10thNight
15%4415%31%31%
2160
11th to 20thNight
12%4215%30%38%
1986
21st to endNight
12%3413%32%35%
2178
April1st to 10thNight
12%2313%33%37%
1837
11th to 20thNight
9%229%28%50%
1779
21st to endNight
5%2210%31%50%
1733
May1st to 10thNight
5%1112%31%50%
1620
11th to 20thNight
6%217%25%59%
1595
21st to endNight
5%118%30%56%
1746
June1st to 10thNight
7%116%21%65%
1620
11th to 20thNight
311312%80%
1620
21st to endNight
8%148%78%
1620
July1st to 10thNight
9%225%15%66%
1575
11th to 20thNight
15%3412%27%40%
1566
21st to endNight
17%5%6%19%26%29%
1674
August1st to 10thNight
9%3410%22%52%
1685
11th to 20thNight
9%4310%27%47%
1780
21st to endNight
9%338%24%53%
1980
September1st to 10thNight
10%349%19%54%
1898
11th to 20thNight
411422%68%
1980
21st to endNight
6%117%18%66%
1980
October1st to 10thNight
11%228%27%50%
1980
11th to 20thNight
6%117%22%63%
1989
21st to endNight
7%138%19%62%
2439
November1st to 10thNight
9%2110%28%50%
2405
11th to 20thNight
11%229%26%50%
2470
21st to endNight
15%2311%29%40%
2470
December1st to 10thNight
19%3315%24%35%
2470
11th to 20thNight
20%5%6%17%28%24%
3041
21st to endNight
19%5%6%24%29%17%
4521

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%10%24%40%19%1
270
11th to 20thDay
7%9%25%30%25%2
243
21st to endDay
417%28%30%19%2
411
February1st to 10thDay
413%24%34%22%3
420
11th to 20thDay
6%20%27%31%15%1
415
21st to endDay
8%19%31%27%14%1
346
March1st to 10thDay
7%19%29%28%16%1
420
11th to 20thDay
6%14%23%35%20%2
420
21st to endDay
6%20%29%29%13%3
462
April1st to 10thDay
414%24%31%23%4
420
11th to 20thDay
5%19%30%26%16%4
412
21st to endDay
316%25%29%19%8%
420
May1st to 10thDay
311%26%34%21%5%
423
11th to 20thDay
110%29%30%23%6%
448
21st to endDay
110%27%35%20%6%
485
June1st to 10thDay
27%22%35%26%8%
450
11th to 20thDay
15%25%33%27%10%
450
21st to endDay
2421%38%28%7%
450
July1st to 10thDay
1213%39%33%13%
446
11th to 20thDay
26%43%34%14%
444
21st to endDay
226%40%35%15%
487
August1st to 10thDay
2111%40%32%14%
447
11th to 20thDay
37%40%32%17%
437
21st to endDay
2110%33%42%14%
495
September1st to 10thDay
3313%40%31%11%
450
11th to 20thDay
2317%37%31%10%
450
21st to endDay
16%19%33%33%8%
450
October1st to 10thDay
28%19%35%29%6%
450
11th to 20thDay
16%17%39%32%5%
438
21st to endDay
210%16%31%35%7%
297
November1st to 10thDay
28%19%36%31%3
270
11th to 20thDay
37%20%35%29%5%
270
21st to endDay
213%21%36%23%6%
270
December1st to 10thDay
6%6%21%39%26%2
270
11th to 20thDay
313%19%41%22%3
270
21st to endDay
7%14%29%30%19%2
297
January1st to 10thNight
45%20%40%26%5%
760
11th to 20thNight
27%19%40%27%5%
724
21st to endNight
5%7%25%39%21%3
792
February1st to 10thNight
37%19%39%27%4
720
11th to 20thNight
49%21%38%24%4
704
21st to endNight
49%27%38%18%4
592
March1st to 10thNight
49%24%39%21%2
720
11th to 20thNight
39%19%33%29%8%
720
21st to endNight
39%23%38%23%4
792
April1st to 10thNight
27%23%38%26%3
720
11th to 20thNight
28%26%34%25%4
711
21st to endNight
17%23%36%28%5%
653
May1st to 10thNight
17%24%37%28%3
540
11th to 20thNight
16%17%38%34%5%
531
21st to endNight
15%21%40%30%3
584
June1st to 10thNight
1315%44%34%3
540
11th to 20thNight
1117%39%37%4
540
21st to endNight
1214%37%41%4
540
July1st to 10thNight
16%40%46%6%
525
11th to 20thNight
3339%49%5%
522
21st to endNight
22333%54%6%
591
August1st to 10thNight
116%31%51%9%
620
11th to 20thNight
11422%58%15%
712
21st to endNight
31226%53%16%
792
September1st to 10thNight
216%28%51%12%
720
11th to 20thNight
19%33%47%11%
720
21st to endNight
1112%34%42%10%
720
October1st to 10thNight
3412%41%37%4
720
11th to 20thNight
1213%40%37%7%
720
21st to endNight
16%13%36%35%10%
792
November1st to 10thNight
1415%41%31%8%
740
11th to 20thNight
3315%38%33%9%
760
21st to endNight
35%17%40%28%7%
760
December1st to 10thNight
4318%43%27%4
760
11th to 20thNight
5%420%41%27%3
760
21st to endNight
5%9%20%41%20%5%
836
Page generated at 2024-01-08 19:31:24. Version ac07

Copyright 2024 Attilla Danko


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