Desert Beaver Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Desert Beaver Observatory clear sky chart from 2005-11-05 to 2017-12-02.

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
72%
15723
35%
47780
30%
15684
78%
15684
50%
23272

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%
717
33%
2327
34%
716
74%
716
48%
1106
January16th to endNight
64%
768
36%
2496
33%
768
73%
768
42%
1274
February1st to 15thNight
70%
698
36%
2262
34%
696
80%
696
53%
1014
February16th to endNight
59%
632
41%
1769
32%
632
69%
632
50%
904
March1st to 15thNight
61%
720
40%
1980
29%
720
70%
720
56%
977
March16th to endNight
67%
768
39%
2112
25%
768
78%
768
61%
1003
April1st to 15thNight
63%
632
37%
1891
25%
632
75%
632
56%
875
April16th to endNight
63%
540
44%
1800
35%
540
81%
540
68%
684
May1st to 15thNight
66%
539
37%
1707
29%
539
77%
539
64%
697
May16th to endNight
72%
561
41%
1684
33%
561
79%
561
68%
690
June1st to 15thNight
80%
540
34%
1620
29%
540
83%
540
64%
703
June16th to endNight
83%
540
27%
1620
25%
540
84%
540
51%
789
July1st to 15thNight
77%
510
17%
1530
15%
510
78%
510
34%
896
July16th to endNight
78%
564
12%
1593
12%
531
78%
531
23%
1060
August1st to 15thNight
75%
539
18%
1617
17%
536
75%
536
29%
998
August16th to endNight
79%
573
25%
1910
28%
573
79%
573
33%
1087
September1st to 15thNight
76%
642
26%
1902
24%
642
77%
642
36%
1133
September16th to endNight
81%
716
41%
1980
31%
716
85%
716
63%
936
October1st to 15thNight
79%
720
38%
2142
31%
720
84%
720
64%
953
October16th to endNight
85%
768
44%
2304
37%
768
89%
768
68%
987
November1st to 15thNight
78%
760
42%
2280
35%
760
84%
760
66%
974
November16th to endNight
69%
780
42%
2392
36%
780
76%
780
52%
1150
December1st to 15thNight
68%
728
37%
2366
35%
728
74%
728
47%
1128
December16th to endNight
61%
768
35%
2496
33%
768
68%
768
42%
1254

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
4313323446%62%
48660
Night
3212323346%64%
47987
TransparencyDay
22%36%14%27%26%
48355
Night
20%36%15%28%25%
47793
SeeingDay
6%6%17%27%28%13%
5539
Night
4213%36%34%7%
15735

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
431221345%7%62%
1611
16th to endDay
7%5%14222346%58%
1728
February1st to 15thDay
5%312112245%68%
1589
16th to endDay
6%41332333463%
1705
March1st to 15thDay
422223337%66%
1980
16th to endDay
3312212235%72%
2112
April1st to 15thDay
3211223245%70%
2057
16th to endDay
2211112480%
2160
May1st to 15thDay
112212335%74%
2240
16th to endDay
112112235%77%
2429
June1st to 15thDay
112212235%75%
2340
16th to endDay
221332445%6%62%
2340
July1st to 15thDay
5%325%6%46%7%7%10%39%
2340
16th to endDay
9%5%27%7%47%8%7%10%27%
2467
August1st to 15thDay
7%436%6%46%7%8%10%34%
2333
16th to endDay
5%425%5%45%7%7%10%41%
2292
September1st to 15thDay
7%425%435%6%6%8%46%
2055
16th to endDay
421321235%5%66%
1980
October1st to 15thDay
211221332474%
1818
16th to endDay
11121234475%
1920
November1st to 15thDay
111212338%71%
1909
16th to endDay
421222223470%
1897
December1st to 15thDay
6%3132335%6%63%
1630
16th to endDay
7%5%13322346%60%
1728
January1st to 15thNight
5%412223346%64%
2327
16th to endNight
6%414313445%59%
2496
February1st to 15thNight
3312213345%68%
2262
16th to endNight
3314313335%65%
1769
March1st to 15thNight
331221225%5%68%
1980
16th to endNight
321211223473%
2112
April1st to 15thNight
3212222345%70%
1891
16th to endNight
1111113481%
1800
May1st to 15thNight
11212237%75%
1707
16th to endNight
11211213380%
1684
June1st to 15thNight
212111335%75%
1620
16th to endNight
121332446%6%62%
1620
July1st to 15thNight
2325%6%36%7%9%13%39%
1620
16th to endNight
5%4247%5%8%9%11%12%28%
1701
August1st to 15thNight
43246%46%7%8%12%38%
1626
16th to endNight
5%4145%36%5%7%11%44%
1910
September1st to 15thNight
6%3135%245%6%9%47%
1902
16th to endNight
2211212345%72%
1980
October1st to 15thNight
112213235%74%
2142
16th to endNight
11222235%77%
2304
November1st to 15thNight
1111112336%74%
2280
16th to endNight
4312213235%68%
2392
December1st to 15thNight
6%312114337%64%
2366
16th to endNight
7%423312236%61%
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
20%25%16%32%22%
1612
16th to endDay
26%3216%30%21%
1728
February1st to 15thDay
19%1314%31%29%
1589
16th to endDay
24%2114%31%25%
1705
March1st to 15thDay
19%229%36%30%
1980
16th to endDay
15%1211%37%31%
2112
April1st to 15thDay
16%218%40%31%
2057
16th to endDay
10%118%31%47%
2160
May1st to 15thDay
12%229%28%44%
2240
16th to endDay
11%129%30%44%
2432
June1st to 15thDay
12%126%24%52%
2340
16th to endDay
20%4310%22%38%
2340
July1st to 15thDay
35%7%16%16%13%10%
2201
16th to endDay
45%10%20%16%5%1
2312
August1st to 15thDay
39%8%15%17%15%2
2318
16th to endDay
33%8%13%17%16%9%
2292
September1st to 15thDay
33%6%10%19%19%10%
2055
16th to endDay
18%1419%34%21%
1980
October1st to 15thDay
15%15%16%30%30%
1818
16th to endDay
12%2314%32%35%
1920
November1st to 15thDay
12%1317%36%28%
1909
16th to endDay
18%2213%32%30%
1897
December1st to 15thDay
21%1419%33%18%
1630
16th to endDay
26%26%20%31%13%
1728
January1st to 15thNight
21%25%14%31%23%
2327
16th to endNight
26%2317%31%18%
2496
February1st to 15thNight
17%2416%31%28%
2273
16th to endNight
22%2313%35%23%
1769
March1st to 15thNight
19%1212%33%31%
1980
16th to endNight
15%1310%38%30%
2112
April1st to 15thNight
17%1213%38%26%
1891
16th to endNight
9%1111%31%44%
1800
May1st to 15thNight
11%239%31%42%
1708
16th to endNight
10%1212%34%38%
1685
June1st to 15thNight
13%225%26%50%
1620
16th to endNight
19%4410%23%38%
1620
July1st to 15thNight
29%8%20%19%11%9%
1530
16th to endNight
38%12%27%16%41
1593
August1st to 15thNight
34%9%17%18%16%4
1617
16th to endNight
29%7%17%19%15%10%
1910
September1st to 15thNight
30%6%12%21%17%10%
1902
16th to endNight
14%2418%39%19%
1980
October1st to 15thNight
13%27%16%29%30%
2142
16th to endNight
11%1315%29%38%
2304
November1st to 15thNight
12%2319%34%28%
2280
16th to endNight
19%2211%30%32%
2392
December1st to 15thNight
21%25%19%32%18%
2366
16th to endNight
26%16%19%29%15%
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%326%41%16%1
90
16th to endDay
7%419%34%23%10%
96
February1st to 15thDay
8%315%28%35%7%
104
16th to endDay
7%20%30%24%12%4
238
March1st to 15thDay
7%13%27%23%22%5%
270
16th to endDay
7%13%28%25%18%6%
288
April1st to 15thDay
5%17%28%28%14%6%
269
16th to endDay
420%31%24%12%6%
270
May1st to 15thDay
414%35%27%11%6%
288
16th to endDay
28%30%38%16%4
330
June1st to 15thDay
2422%34%22%13%
315
16th to endDay
318%33%33%19%
315
July1st to 15thDay
7%5%28%39%19%
305
16th to endDay
6%2321%34%31%
327
August1st to 15thDay
9%1117%39%30%
315
16th to endDay
5%218%43%29%
332
September1st to 15thDay
11%425%41%16%
315
16th to endDay
7%312%29%37%8%
315
October1st to 15thDay
115%24%40%16%
153
16th to endDay
19%23%40%25%
144
November1st to 15thDay
35%18%33%34%3
135
16th to endDay
7%317%29%36%5%
135
December1st to 15thDay
6%318%29%28%13%
94
16th to endDay
23%5%18%30%20%1
96
January1st to 15thNight
6%115%44%25%6%
720
16th to endNight
8%316%41%24%4
768
February1st to 15thNight
4415%40%27%6%
704
16th to endNight
45%25%44%17%2
632
March1st to 15thNight
5%424%37%23%5%
720
16th to endNight
35%19%39%27%4
768
April1st to 15thNight
36%22%45%19%2
632
16th to endNight
1429%39%22%3
540
May1st to 15thNight
1323%43%25%2
540
16th to endNight
1317%44%31%2
563
June1st to 15thNight
2110%49%32%3
540
16th to endNight
21440%47%4
540
July1st to 15thNight
3226%55%10%
510
16th to endNight
5%115%60%15%
564
August1st to 15thNight
41113%57%21%
539
16th to endNight
5%115%59%17%
573
September1st to 15thNight
7%320%53%13%
642
16th to endNight
48%33%43%9%
716
October1st to 15thNight
2112%39%35%8%
720
16th to endNight
219%36%39%11%
768
November1st to 15thNight
2113%39%35%7%
760
16th to endNight
6%217%33%31%8%
780
December1st to 15thNight
7%416%36%29%5%
728
16th to endNight
9%416%40%22%5%
768
Page generated at 2017-12-03 09:16:44. Version ac04

Copyright 2017 A. Danko


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