Desert Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Desert Center clear sky chart from 2005-11-05 to 2018-04-23.

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
77%
16894
41%
49546
33%
16854
84%
16854
64%
21597

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
72%
780
35%
2522
32%
776
80%
776
48%
1165
January16th to endNight
67%
832
41%
2597
33%
832
80%
832
52%
1194
February1st to 15thNight
71%
760
41%
2291
34%
760
82%
760
57%
1023
February16th to endNight
62%
684
39%
2051
36%
684
72%
684
53%
977
March1st to 15thNight
69%
780
39%
2279
33%
780
79%
780
62%
1000
March16th to endNight
71%
832
40%
2288
29%
832
81%
832
62%
1055
April1st to 15thNight
64%
779
41%
1975
21%
779
75%
779
65%
931
April16th to endNight
68%
699
45%
1815
23%
699
80%
699
76%
785
May1st to 15thNight
72%
539
44%
1619
30%
539
80%
539
76%
617
May16th to endNight
74%
561
41%
1685
30%
561
79%
561
77%
645
June1st to 15thNight
81%
540
36%
1620
31%
540
83%
540
79%
614
June16th to endNight
85%
540
38%
1620
33%
540
87%
540
81%
616
July1st to 15thNight
89%
510
30%
1530
26%
510
89%
510
62%
677
July16th to endNight
87%
564
35%
1593
30%
531
88%
531
55%
756
August1st to 15thNight
90%
654
38%
1728
26%
651
91%
651
71%
789
August16th to endNight
92%
764
43%
1910
31%
764
92%
764
71%
920
September1st to 15thNight
90%
720
39%
1926
32%
720
92%
720
72%
865
September16th to endNight
87%
716
50%
1980
42%
716
93%
716
84%
797
October1st to 15thNight
80%
720
45%
1980
37%
720
87%
720
72%
858
October16th to endNight
84%
768
49%
2293
45%
768
90%
768
73%
913
November1st to 15thNight
80%
760
39%
2470
36%
760
89%
760
64%
1002
November16th to endNight
77%
780
45%
2535
45%
780
84%
780
63%
1027
December1st to 15thNight
72%
780
38%
2535
36%
780
80%
780
53%
1129
December16th to endNight
67%
832
40%
2704
35%
832
78%
832
49%
1242

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
111112235%77%
49970
Night
111112235%77%
49742
TransparencyDay
11%2311%25%45%
49665
Night
11%2311%26%44%
49548
SeeingDay
29%20%35%25%6%
6516
Night
2413%33%38%8%
16901

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
22222335%5%69%
1746
16th to endDay
2212113336%70%
1978
February1st to 15thDay
11223346%71%
1901
16th to endDay
222223337%67%
1709
March1st to 15thDay
111121337%74%
2009
16th to endDay
111112336%76%
2288
April1st to 15thDay
11212345%75%
2300
16th to endDay
11112485%
2259
May1st to 15thDay
11113483%
2331
16th to endDay
1122386%
2429
June1st to 15thDay
112387%
2340
16th to endDay
111289%
2340
July1st to 15thDay
211113336%73%
2340
16th to endDay
3112223347%67%
2467
August1st to 15thDay
112212345%74%
2220
16th to endDay
222212245%73%
2292
September1st to 15thDay
111212345%76%
2034
16th to endDay
1112287%
1980
October1st to 15thDay
121222382%
1980
16th to endDay
111222482%
1926
November1st to 15thDay
111112235%77%
1719
16th to endDay
111112245%77%
1755
December1st to 15thDay
2112212348%68%
1755
16th to endDay
331122235%7%66%
1872
January1st to 15thNight
121232345%6%67%
2522
16th to endNight
321221333470%
2597
February1st to 15thNight
1112223236%73%
2281
16th to endNight
3212223446%67%
2051
March1st to 15thNight
111113346%74%
2279
16th to endNight
11123336%75%
2288
April1st to 15thNight
111334478%
1975
16th to endNight
11112386%
1815
May1st to 15thNight
1112486%
1619
16th to endNight
11111288%
1684
June1st to 15thNight
112387%
1620
16th to endNight
1111289%
1620
July1st to 15thNight
1111113345%73%
1620
16th to endNight
211222335%5%67%
1701
August1st to 15thNight
1111233479%
1737
16th to endNight
111112246%77%
1910
September1st to 15thNight
11112235%79%
1926
16th to endNight
111290%
1980
October1st to 15thNight
1111113482%
1980
16th to endNight
111212483%
2293
November1st to 15thNight
1113325%78%
2470
16th to endNight
212111225%78%
2535
December1st to 15thNight
2212222336%71%
2535
16th to endNight
312323347%68%
2704

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
17%4416%32%25%
1747
16th to endDay
17%2415%33%27%
1978
February1st to 15thDay
13%35%14%28%34%
1901
16th to endDay
17%4416%30%26%
1709
March1st to 15thDay
11%2214%30%37%
2009
16th to endDay
12%2314%34%31%
2288
April1st to 15thDay
12%2210%32%39%
2300
16th to endDay
6%119%31%48%
2259
May1st to 15thDay
7%117%27%54%
2331
16th to endDay
5%118%24%57%
2432
June1st to 15thDay
5%1418%69%
2340
16th to endDay
5%138%80%
2340
July1st to 15thDay
13%348%18%52%
2201
16th to endDay
16%35%17%24%31%
2312
August1st to 15thDay
12%2310%24%45%
2205
16th to endDay
14%2310%23%45%
2292
September1st to 15thDay
11%3411%21%48%
2034
16th to endDay
6%1420%65%
1980
October1st to 15thDay
9%127%25%52%
1980
16th to endDay
8%239%20%56%
1926
November1st to 15thDay
12%2213%30%38%
1719
16th to endDay
11%2413%29%38%
1755
December1st to 15thDay
16%35%19%27%29%
1755
16th to endDay
18%36%20%28%21%
1872
January1st to 15thNight
17%4412%31%29%
2522
16th to endNight
18%2417%23%34%
2597
February1st to 15thNight
14%2314%28%36%
2292
16th to endNight
18%2313%30%30%
2051
March1st to 15thNight
11%2314%32%34%
2279
16th to endNight
12%2314%30%36%
2288
April1st to 15thNight
10%2311%33%38%
1975
16th to endNight
5%1210%29%49%
1815
May1st to 15thNight
6%110%31%50%
1620
16th to endNight
5%117%30%53%
1685
June1st to 15thNight
5%116%17%68%
1620
16th to endNight
6%37%81%
1620
July1st to 15thNight
13%336%19%53%
1530
16th to endNight
16%4415%28%30%
1593
August1st to 15thNight
9%338%27%47%
1728
16th to endNight
10%338%23%50%
1910
September1st to 15thNight
9%3311%21%51%
1926
16th to endNight
5%420%68%
1980
October1st to 15thNight
9%127%27%51%
1980
16th to endNight
8%128%20%58%
2293
November1st to 15thNight
11%2210%28%43%
2470
16th to endNight
12%1211%30%41%
2535
December1st to 15thNight
16%35%15%26%33%
2535
16th to endNight
17%36%18%29%24%
2704

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
8%5%20%41%22%2
135
16th to endDay
313%25%28%25%4
250
February1st to 15thDay
310%24%33%25%3
326
16th to endDay
6%18%27%28%17%1
290
March1st to 15thDay
416%20%34%22%1
330
16th to endDay
215%25%32%19%4
352
April1st to 15thDay
417%25%25%20%5%
329
16th to endDay
323%28%25%15%3
288
May1st to 15thDay
212%31%31%17%4
288
16th to endDay
111%29%35%17%3
330
June1st to 15thDay
15%29%34%23%5%
315
16th to endDay
1220%40%27%8%
315
July1st to 15thDay
1112%46%27%10%
305
16th to endDay
36%42%34%11%
327
August1st to 15thDay
111%46%28%11%
315
16th to endDay
28%38%37%12%
332
September1st to 15thDay
1216%45%25%8%
315
16th to endDay
16%17%34%33%6%
315
October1st to 15thDay
110%20%39%26%3
315
16th to endDay
1415%27%41%9%
195
November1st to 15thDay
5%16%33%37%6%
135
16th to endDay
311%19%30%27%8%
135
December1st to 15thDay
115%12%31%34%3
135
16th to endDay
6%11%13%33%29%5%
144
January1st to 15thNight
25%15%40%29%6%
780
16th to endNight
35%18%36%29%5%
832
February1st to 15thNight
25%15%37%32%5%
764
16th to endNight
45%22%39%22%4
684
March1st to 15thNight
27%19%37%28%6%
780
16th to endNight
17%15%37%30%7%
832
April1st to 15thNight
18%22%34%28%5%
779
16th to endNight
17%21%35%29%5%
699
May1st to 15thNight
5%19%35%34%5%
540
16th to endNight
418%35%35%5%
563
June1st to 15thNight
213%44%34%4
540
16th to endNight
119%34%48%4
540
July1st to 15thNight
2331%54%6%
510
16th to endNight
21327%57%7%
564
August1st to 15thNight
1321%60%12%
654
16th to endNight
2116%57%21%
764
September1st to 15thNight
1322%55%15%
720
16th to endNight
19%28%45%14%
716
October1st to 15thNight
2310%37%40%6%
720
16th to endNight
128%31%42%12%
768
November1st to 15thNight
1114%38%34%9%
760
16th to endNight
2311%32%35%13%
780
December1st to 15thNight
3314%39%32%5%
780
16th to endNight
47%15%38%26%6%
832
Page generated at 2018-04-24 07:03:00. Version ac04

Copyright 2018 A. Danko


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