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Joshua Tree Astronomy Arts Theater
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Joshua Tree Astronomy Arts Theater clear sky chart from 2005-11-05 to 2017-05-24.

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
74%
15712
41%
45885
32%
15671
82%
15671
66%
19548

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
70%
719
36%
2327
32%
716
79%
716
52%
1029
January16th to endNight
65%
768
42%
2367
33%
768
78%
768
52%
1082
February1st to 15thNight
68%
699
40%
2108
33%
698
79%
698
58%
929
February16th to endNight
63%
632
41%
1895
36%
632
75%
632
52%
888
March1st to 15thNight
65%
720
38%
2136
32%
720
77%
720
60%
925
March16th to endNight
66%
768
41%
2079
28%
768
77%
768
61%
960
April1st to 15thNight
56%
719
39%
1799
17%
719
69%
719
64%
855
April16th to endNight
65%
705
44%
1785
22%
705
76%
705
75%
785
May1st to 15thNight
71%
539
44%
1619
30%
539
78%
539
78%
600
May16th to endNight
67%
541
39%
1622
27%
540
74%
540
75%
626
June1st to 15thNight
77%
495
37%
1485
30%
495
82%
495
79%
556
June16th to endNight
81%
495
35%
1485
30%
495
83%
495
81%
559
July1st to 15thNight
88%
465
34%
1395
30%
465
88%
465
70%
573
July16th to endNight
86%
522
36%
1467
31%
489
87%
489
63%
652
August1st to 15thNight
92%
637
42%
1621
28%
634
92%
634
79%
729
August16th to endNight
90%
700
43%
1750
29%
700
91%
700
79%
792
September1st to 15thNight
91%
660
42%
1735
33%
660
93%
660
77%
758
September16th to endNight
88%
656
48%
1815
42%
656
93%
656
86%
707
October1st to 15thNight
78%
660
47%
1815
37%
660
86%
660
74%
771
October16th to endNight
82%
704
46%
2129
42%
704
89%
704
74%
830
November1st to 15thNight
78%
700
42%
2275
38%
700
89%
700
71%
859
November16th to endNight
77%
720
44%
2340
43%
720
85%
720
64%
927
December1st to 15thNight
70%
720
38%
2340
33%
720
81%
720
53%
1016
December16th to endNight
63%
768
38%
2496
33%
768
74%
768
47%
1140

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%76%
46387
Night
111112235%77%
46084
TransparencyDay
11%1314%28%40%
46082
Night
11%1315%29%38%
45890
SeeingDay
410%21%34%22%6%
5352
Night
25%14%33%34%10%
15720

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
133213337%68%
1611
16th to endDay
3112312437%67%
1854
February1st to 15thDay
1211213346%71%
1751
16th to endDay
112313348%67%
1579
March1st to 15thDay
11111347%75%
1824
16th to endDay
111212336%76%
2142
April1st to 15thDay
11222346%74%
2149
16th to endDay
11125%83%
2175
May1st to 15thDay
111112483%
2331
16th to endDay
1123484%
2335
June1st to 15thDay
122485%
2145
16th to endDay
11111287%
2145
July1st to 15thDay
3111212337%73%
2145
16th to endDay
1112324345%68%
2285
August1st to 15thDay
1211124478%
1998
16th to endDay
111212345%75%
2100
September1st to 15thDay
11111224479%
1895
16th to endDay
111112286%
1815
October1st to 15thDay
11112235%80%
1815
16th to endDay
1212135%81%
1741
November1st to 15thDay
1111223478%
1584
16th to endDay
1111113237%74%
1620
December1st to 15thDay
1212223248%67%
1620
16th to endDay
2223223346%66%
1728
January1st to 15thNight
1212223447%68%
2327
16th to endNight
2112212346%69%
2367
February1st to 15thNight
2112212335%73%
2101
16th to endNight
21122346%7%66%
1895
March1st to 15thNight
1111112337%73%
2136
16th to endNight
11213236%75%
2079
April1st to 15thNight
1221233477%
1799
16th to endNight
11235%83%
1785
May1st to 15thNight
11225%85%
1619
16th to endNight
111112485%
1621
June1st to 15thNight
122387%
1485
16th to endNight
1111289%
1485
July1st to 15thNight
111112235%77%
1485
16th to endNight
1112123345%73%
1575
August1st to 15thNight
111222482%
1630
16th to endNight
111114481%
1750
September1st to 15thNight
1111235%81%
1735
16th to endNight
12190%
1815
October1st to 15thNight
112235%80%
1815
16th to endNight
111113482%
2129
November1st to 15thNight
112335%80%
2275
16th to endNight
211112235%77%
2340
December1st to 15thNight
211222335%8%67%
2340
16th to endNight
2212313346%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
17%25%19%34%20%
1612
16th to endDay
18%1420%31%22%
1854
February1st to 15thDay
15%15%18%32%27%
1751
16th to endDay
16%25%20%35%19%
1579
March1st to 15thDay
9%2220%33%31%
1824
16th to endDay
11%1322%34%25%
2142
April1st to 15thDay
11%1314%37%30%
2149
16th to endDay
7%116%34%39%
2175
May1st to 15thDay
7%1110%34%45%
2331
16th to endDay
6%1211%32%47%
2338
June1st to 15thDay
6%118%18%64%
2145
16th to endDay
7%310%77%
2145
July1st to 15thDay
13%119%21%52%
2006
16th to endDay
17%2413%23%37%
2130
August1st to 15thDay
9%1111%23%53%
1983
16th to endDay
11%2210%23%48%
2100
September1st to 15thDay
10%1310%20%54%
1895
16th to endDay
7%15%26%59%
1815
October1st to 15thDay
9%2110%32%43%
1815
16th to endDay
8%311%29%46%
1741
November1st to 15thDay
11%1314%34%34%
1584
16th to endDay
11%1318%31%32%
1620
December1st to 15thDay
17%26%24%28%21%
1620
16th to endDay
20%28%26%25%16%
1728
January1st to 15thNight
17%2419%31%24%
2327
16th to endNight
17%2422%26%26%
2367
February1st to 15thNight
15%1319%31%29%
2112
16th to endNight
16%3322%32%21%
1895
March1st to 15thNight
12%2319%33%28%
2136
16th to endNight
12%2418%36%25%
2079
April1st to 15thNight
11%15%16%36%28%
1799
16th to endNight
5%1215%35%39%
1785
May1st to 15thNight
41214%35%41%
1620
16th to endNight
6%215%36%37%
1622
June1st to 15thNight
5%1110%20%61%
1485
16th to endNight
5%15%13%74%
1485
July1st to 15thNight
10%118%20%57%
1395
16th to endNight
14%1415%25%38%
1467
August1st to 15thNight
7%1111%25%52%
1621
16th to endNight
8%1111%27%50%
1750
September1st to 15thNight
7%248%21%55%
1735
16th to endNight
46%26%61%
1815
October1st to 15thNight
8%1211%34%42%
1815
16th to endNight
7%1310%26%49%
2129
November1st to 15thNight
8%1313%37%35%
2275
16th to endNight
11%1216%33%34%
2340
December1st to 15thNight
16%27%18%29%24%
2340
16th to endNight
18%29%22%28%19%
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
11%11%17%43%16%
90
16th to endDay
419%23%33%15%3
222
February1st to 15thDay
5%15%23%32%20%3
266
16th to endDay
10%22%24%25%15%
238
March1st to 15thDay
6%17%21%30%21%3
270
16th to endDay
7%15%25%30%17%3
288
April1st to 15thDay
9%21%24%24%17%4
269
16th to endDay
6%21%29%24%12%5%
270
May1st to 15thDay
412%25%34%18%5%
288
16th to endDay
110%24%37%18%6%
301
June1st to 15thDay
17%29%32%23%7%
255
16th to endDay
2426%31%24%10%
255
July1st to 15thDay
115%42%30%9%
245
16th to endDay
1114%43%25%14%
271
August1st to 15thDay
1215%49%18%12%
255
16th to endDay
2111%41%24%17%
268
September1st to 15thDay
2217%43%26%7%
255
16th to endDay
29%17%35%28%6%
255
October1st to 15thDay
110%26%37%20%3
255
16th to endDay
26%20%31%35%3
170
November1st to 15thDay
11%13%24%38%12%
90
16th to endDay
412%26%27%22%6%
90
December1st to 15thDay
5%10%16%27%35%4
90
16th to endDay
8%11%25%32%22%
96
January1st to 15thNight
36%14%37%27%9%
720
16th to endNight
47%16%35%27%8%
768
February1st to 15thNight
26%16%36%27%9%
704
16th to endNight
38%21%37%21%7%
632
March1st to 15thNight
28%19%35%27%7%
720
16th to endNight
110%17%35%27%8%
768
April1st to 15thNight
111%25%28%26%5%
719
16th to endNight
9%22%34%26%6%
705
May1st to 15thNight
16%19%34%34%4
540
16th to endNight
6%23%33%31%5%
542
June1st to 15thNight
317%43%32%3
495
16th to endNight
1114%41%35%6%
495
July1st to 15thNight
25%34%48%8%
465
16th to endNight
2429%55%7%
522
August1st to 15thNight
328%52%13%
637
16th to endNight
1320%52%21%
700
September1st to 15thNight
427%51%15%
660
16th to endNight
117%29%44%15%
656
October1st to 15thNight
1314%35%33%10%
660
16th to endNight
39%30%37%17%
704
November1st to 15thNight
315%31%35%13%
700
16th to endNight
35%10%32%33%14%
720
December1st to 15thNight
45%15%38%27%8%
720
16th to endNight
6%8%16%36%24%6%
768
Page generated at 2017-05-25 10:27:30. Version ac04

Copyright 2017 A. Danko


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