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 2017-03-14.

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
76%
15389
40%
45176
33%
15349
83%
15349
64%
19733

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
71%
720
35%
2327
32%
716
80%
716
49%
1065
January16th to endNight
66%
768
41%
2397
32%
768
79%
768
51%
1111
February1st to 15thNight
70%
700
41%
2111
34%
700
82%
700
57%
943
February16th to endNight
62%
632
38%
1895
35%
632
72%
632
51%
921
March1st to 15thNight
67%
716
39%
2093
33%
716
78%
716
61%
920
March16th to endNight
72%
704
39%
1936
29%
704
80%
704
62%
899
April1st to 15thNight
62%
659
41%
1671
21%
659
74%
659
64%
792
April16th to endNight
69%
619
42%
1609
21%
619
79%
619
76%
694
May1st to 15thNight
72%
494
46%
1484
31%
494
80%
494
79%
556
May16th to endNight
74%
513
39%
1541
28%
513
79%
513
76%
593
June1st to 15thNight
81%
495
38%
1485
32%
495
83%
495
79%
566
June16th to endNight
85%
495
36%
1485
31%
495
86%
495
80%
569
July1st to 15thNight
88%
465
31%
1395
27%
465
88%
465
60%
629
July16th to endNight
87%
522
35%
1467
29%
489
87%
489
56%
689
August1st to 15thNight
90%
599
40%
1583
27%
596
91%
596
71%
723
August16th to endNight
92%
700
41%
1750
29%
700
92%
700
69%
854
September1st to 15thNight
91%
660
40%
1765
33%
660
93%
660
73%
786
September16th to endNight
86%
656
47%
1815
40%
656
92%
656
83%
736
October1st to 15thNight
79%
660
46%
1815
38%
660
86%
660
71%
797
October16th to endNight
83%
704
47%
2101
42%
704
89%
704
72%
844
November1st to 15thNight
78%
700
41%
2275
37%
700
89%
700
66%
902
November16th to endNight
77%
720
44%
2340
43%
720
85%
720
64%
933
December1st to 15thNight
73%
720
39%
2340
36%
720
80%
720
52%
1053
December16th to endNight
66%
768
39%
2496
33%
768
77%
768
48%
1158

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%
45529
Night
111112235%77%
45372
TransparencyDay
11%2311%26%44%
45224
Night
12%2311%26%43%
45178
SeeingDay
39%21%36%24%5%
5012
Night
2413%33%37%8%
15396

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%
1611
16th to endDay
3212213336%69%
1826
February1st to 15thDay
212213346%71%
1751
16th to endDay
222223347%67%
1579
March1st to 15thDay
111111337%75%
1836
16th to endDay
111212235%75%
1936
April1st to 15thDay
11212345%74%
1944
16th to endDay
11112485%
2021
May1st to 15thDay
11113484%
2136
16th to endDay
112387%
2221
June1st to 15thDay
112387%
2145
16th to endDay
111288%
2145
July1st to 15thDay
211113336%73%
2145
16th to endDay
2112213347%68%
2285
August1st to 15thDay
112212345%74%
2035
16th to endDay
2212212245%72%
2100
September1st to 15thDay
111212345%76%
1865
16th to endDay
11113286%
1815
October1st to 15thDay
121222481%
1815
16th to endDay
111212482%
1766
November1st to 15thDay
111112235%79%
1584
16th to endDay
1112245%78%
1620
December1st to 15thDay
2212223348%67%
1620
16th to endDay
331122335%7%66%
1728
January1st to 15thNight
121232235%6%68%
2327
16th to endNight
321221333470%
2397
February1st to 15thNight
1112223236%73%
2101
16th to endNight
3212223446%65%
1895
March1st to 15thNight
111113346%75%
2093
16th to endNight
11212336%76%
1936
April1st to 15thNight
111333478%
1671
16th to endNight
1112387%
1609
May1st to 15thNight
1112487%
1484
16th to endNight
11111287%
1540
June1st to 15thNight
112287%
1485
16th to endNight
1111289%
1485
July1st to 15thNight
1112113345%72%
1485
16th to endNight
211222335%5%68%
1575
August1st to 15thNight
1111233478%
1592
16th to endNight
111112346%76%
1750
September1st to 15thNight
1112235%80%
1765
16th to endNight
1111190%
1815
October1st to 15thNight
2111123480%
1815
16th to endNight
1111212482%
2101
November1st to 15thNight
111332480%
2275
16th to endNight
211111125%79%
2340
December1st to 15thNight
2212222336%70%
2340
16th to endNight
322323347%67%
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
16%4415%31%27%
1612
16th to endDay
18%2414%32%27%
1826
February1st to 15thDay
14%35%14%29%32%
1751
16th to endDay
17%4416%30%25%
1579
March1st to 15thDay
10%2213%31%39%
1836
16th to endDay
13%2315%33%31%
1936
April1st to 15thDay
13%2210%32%38%
1944
16th to endDay
7%119%32%48%
2021
May1st to 15thDay
7%117%27%54%
2136
16th to endDay
5%118%25%57%
2224
June1st to 15thDay
5%1417%69%
2145
16th to endDay
6%138%79%
2145
July1st to 15thDay
12%348%18%52%
2006
16th to endDay
15%45%17%24%32%
2130
August1st to 15thDay
13%2210%25%45%
2020
16th to endDay
15%2410%23%43%
2100
September1st to 15thDay
11%3411%20%49%
1865
16th to endDay
7%115%20%64%
1815
October1st to 15thDay
10%228%27%48%
1815
16th to endDay
8%1310%21%54%
1766
November1st to 15thDay
11%1211%31%41%
1584
16th to endDay
10%2414%29%38%
1620
December1st to 15thDay
16%35%20%28%25%
1620
16th to endDay
19%36%21%27%20%
1728
January1st to 15thNight
17%4312%30%31%
2327
16th to endNight
19%2417%23%33%
2397
February1st to 15thNight
14%2215%28%35%
2112
16th to endNight
19%2314%29%29%
1895
March1st to 15thNight
12%2312%32%36%
2093
16th to endNight
12%2314%29%36%
1936
April1st to 15thNight
11%2312%33%37%
1671
16th to endNight
5%1211%29%49%
1609
May1st to 15thNight
5%10%31%51%
1485
16th to endNight
6%117%32%50%
1541
June1st to 15thNight
5%116%17%67%
1485
16th to endNight
6%37%80%
1485
July1st to 15thNight
14%347%17%53%
1395
16th to endNight
17%3414%27%32%
1467
August1st to 15thNight
9%338%28%45%
1583
16th to endNight
10%339%25%47%
1750
September1st to 15thNight
8%3310%21%52%
1765
16th to endNight
5%420%67%
1815
October1st to 15thNight
9%128%28%48%
1815
16th to endNight
8%138%20%57%
2101
November1st to 15thNight
10%2210%27%47%
2275
16th to endNight
11%1212%30%41%
2340
December1st to 15thNight
17%35%15%27%30%
2340
16th to endNight
18%37%19%28%22%
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
8%6%26%44%13%
90
16th to endDay
415%27%25%23%3
194
February1st to 15thDay
310%26%34%22%1
266
16th to endDay
7%18%28%26%17%2
238
March1st to 15thDay
417%20%32%23%2
264
16th to endDay
315%28%30%18%4
224
April1st to 15thDay
7%21%28%24%14%3
209
16th to endDay
322%30%27%12%1
210
May1st to 15thDay
113%32%32%17%3
228
16th to endDay
111%31%37%14%3
266
June1st to 15thDay
26%31%35%19%5%
255
16th to endDay
1323%42%22%7%
255
July1st to 15thDay
2114%48%25%7%
245
16th to endDay
217%45%33%10%
271
August1st to 15thDay
111%49%26%10%
255
16th to endDay
28%41%35%11%
268
September1st to 15thDay
1217%46%24%7%
255
16th to endDay
27%15%34%34%5%
255
October1st to 15thDay
112%19%38%24%3
255
16th to endDay
15%17%27%42%4
143
November1st to 15thDay
17%18%26%35%10%
90
16th to endDay
214%21%31%27%3
90
December1st to 15thDay
214%12%33%33%4
90
16th to endDay
9%12%16%38%22%
96
January1st to 15thNight
25%15%40%28%7%
720
16th to endNight
45%19%35%29%5%
768
February1st to 15thNight
25%16%38%32%5%
704
16th to endNight
5%6%22%39%21%5%
632
March1st to 15thNight
27%19%35%28%6%
716
16th to endNight
17%16%38%28%8%
704
April1st to 15thNight
110%23%33%26%5%
659
16th to endNight
17%21%34%30%5%
619
May1st to 15thNight
5%19%35%34%5%
495
16th to endNight
418%36%34%5%
515
June1st to 15thNight
213%44%33%4
495
16th to endNight
119%35%46%5%
495
July1st to 15thNight
2432%54%6%
465
16th to endNight
21327%56%8%
522
August1st to 15thNight
1321%60%12%
599
16th to endNight
2216%57%21%
700
September1st to 15thNight
1323%54%17%
660
16th to endNight
19%27%44%15%
656
October1st to 15thNight
2311%36%38%6%
660
16th to endNight
139%31%42%12%
704
November1st to 15thNight
1215%36%34%10%
700
16th to endNight
3411%32%35%13%
720
December1st to 15thNight
4313%39%32%5%
720
16th to endNight
5%8%16%39%24%6%
768
Page generated at 2017-03-15 08:32:34. Version ac04

Copyright 2017 A. Danko


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