Hualapai Valley Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hualapai Valley Observatory clear sky chart from 2005-11-06 to 2024-01-14.

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%
24289
36%
74394
32%
24251
81%
24251
56%
34545

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%
757
34%
2457
33%
756
74%
756
44%
1208
January11th to 20thNight
72%
736
35%
2391
35%
736
78%
736
48%
1133
January21st to endNight
66%
792
36%
2574
33%
792
75%
792
43%
1290
February1st to 10thNight
72%
720
37%
2182
34%
720
79%
720
54%
1027
February11th to 20thNight
65%
700
37%
2099
33%
700
73%
700
48%
1056
February21st to endNight
63%
592
37%
1776
37%
592
69%
592
49%
896
March1st to 10thNight
65%
720
31%
2098
28%
720
73%
720
50%
1054
March11th to 20thNight
68%
720
35%
1980
30%
720
74%
720
51%
1032
March21st to endNight
70%
792
35%
2178
26%
792
77%
792
56%
1085
April1st to 10thNight
68%
720
33%
1948
21%
720
74%
720
58%
962
April11th to 20thNight
65%
693
38%
1761
21%
693
73%
693
62%
876
April21st to endNight
71%
540
43%
1620
31%
540
79%
540
65%
688
May1st to 10thNight
70%
540
38%
1620
26%
540
77%
540
63%
704
May11th to 20thNight
77%
531
40%
1595
32%
531
81%
531
69%
656
May21st to endNight
74%
582
36%
1746
28%
582
79%
582
68%
732
June1st to 10thNight
83%
540
36%
1620
31%
540
86%
540
77%
631
June11th to 20thNight
81%
540
36%
1620
32%
540
83%
540
76%
632
June21st to endNight
85%
540
33%
1620
30%
540
88%
540
70%
666
July1st to 10thNight
89%
525
31%
1575
28%
525
89%
525
63%
693
July11th to 20thNight
85%
522
28%
1566
25%
522
85%
522
51%
775
July21st to endNight
83%
591
28%
1674
24%
558
84%
558
41%
910
August1st to 10thNight
85%
537
36%
1602
28%
534
86%
534
56%
744
August11th to 20thNight
88%
579
38%
1647
29%
579
89%
579
61%
777
August21st to endNight
89%
792
40%
1980
30%
792
89%
792
65%
995
September1st to 10thNight
85%
720
35%
1957
28%
720
86%
720
61%
960
September11th to 20thNight
87%
720
45%
1980
38%
720
90%
720
75%
850
September21st to endNight
84%
720
43%
1980
35%
720
89%
720
76%
844
October1st to 10thNight
77%
720
40%
1980
31%
720
83%
720
62%
934
October11th to 20thNight
84%
720
45%
2101
40%
720
88%
720
70%
893
October21st to endNight
78%
792
45%
2376
38%
792
86%
792
72%
970
November1st to 10thNight
81%
740
39%
2405
39%
740
87%
740
62%
1004
November11th to 20thNight
80%
760
42%
2470
40%
760
87%
760
64%
1001
November21st to endNight
73%
760
39%
2470
37%
760
79%
760
54%
1097
December1st to 10thNight
73%
760
35%
2470
34%
760
77%
760
45%
1221
December11th to 20thNight
72%
758
33%
2909
33%
758
77%
758
37%
1481
December21st to endNight
65%
818
21%
4367
31%
817
71%
817
26%
2068

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
3312323446%69%
74923
Night
3212323346%70%
74885
TransparencyDay
17%46%14%27%32%
74650
Night
16%46%15%28%31%
74680
SeeingDay
46%19%33%25%14%
14029
Night
4213%42%34%5%
24318

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
6%5%2432335%6%62%
1708
11th to 20thDay
4413322446%66%
1647
21st to endDay
7%413423446%62%
1782
February1st to 10thDay
3412222436%69%
1776
11th to 20thDay
6%413324348%62%
1750
21st to endDay
8%423424336%62%
1480
March1st to 10thDay
5%41332345%9%62%
1862
11th to 20thDay
35%23423436%65%
1980
21st to endDay
431331346%7%65%
2178
April1st to 10thDay
322332445%6%66%
2008
11th to 20thDay
3312212335%75%
2147
21st to endDay
3212212336%75%
2340
May1st to 10thDay
2111212347%75%
2340
11th to 20thDay
212112236%79%
2301
21st to endDay
2212212225%79%
2530
June1st to 10thDay
1111212235%81%
2340
11th to 20thDay
111121123385%
2340
21st to endDay
1111212335%79%
2340
July1st to 10thDay
111342445%6%69%
2340
11th to 20thDay
3223435%5%6%7%60%
2340
21st to endDay
4435%5%46%6%8%9%45%
2545
August1st to 10thDay
3212435%46%6%64%
2328
11th to 20thDay
22134345%6%6%64%
2249
21st to endDay
231332445%7%66%
2376
September1st to 10thDay
33134245%5%7%63%
2002
11th to 20thDay
211121233479%
1980
21st to endDay
2212212335%77%
1980
October1st to 10thDay
3212323445%72%
1980
11th to 20thDay
12121224480%
1859
21st to endDay
1112212235%81%
1976
November1st to 10thDay
2212213346%74%
1674
11th to 20thDay
2212222235%77%
1710
21st to endDay
4312223345%72%
1710
December1st to 10thDay
5%42332335%8%62%
1710
11th to 20thDay
6%4244345%6%10%52%
2169
21st to endDay
8%5%2342446%9%53%
3146
January1st to 10thNight
5%5%23323445%65%
2457
11th to 20thNight
5%412323347%65%
2391
21st to endNight
6%5%23433345%62%
2574
February1st to 10thNight
4313223235%71%
2182
11th to 20thNight
4424323346%65%
2098
21st to endNight
6%5%23313347%63%
1776
March1st to 10thNight
431332445%8%61%
2098
11th to 20thNight
6%413323347%63%
1980
21st to endNight
321322345%7%66%
2178
April1st to 10thNight
321332335%7%70%
1948
11th to 20thNight
2212323335%75%
1761
21st to endNight
3112312245%76%
1620
May1st to 10thNight
2112212347%74%
1620
11th to 20thNight
2111123235%80%
1594
21st to endNight
1111213336%78%
1746
June1st to 10thNight
11111335%83%
1620
11th to 20thNight
11111222385%
1620
21st to endNight
111221234479%
1620
July1st to 10thNight
2212213446%73%
1620
11th to 20thNight
221442447%8%61%
1620
21st to endNight
2315%5%45%7%7%11%51%
1773
August1st to 10thNight
2213323347%70%
1611
11th to 20thNight
2212223348%70%
1647
21st to endNight
221232245%8%70%
1980
September1st to 10thNight
311242345%8%68%
1957
11th to 20thNight
111121223482%
1980
21st to endNight
11122223383%
1980
October1st to 10thNight
321231433475%
1980
11th to 20thNight
2111112235%80%
2101
21st to endNight
211221223481%
2376
November1st to 10thNight
2212223345%75%
2405
11th to 20thNight
3212213335%76%
2470
21st to endNight
5%322212346%70%
2470
December1st to 10thNight
6%41332345%6%64%
2470
11th to 20thNight
7%4144245%5%8%57%
3041
21st to endNight
8%4234345%6%7%54%
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
24%5%7%20%33%12%
1709
11th to 20thDay
19%47%21%33%15%
1647
21st to endDay
25%38%19%33%12%
1782
February1st to 10thDay
19%38%16%30%24%
1776
11th to 20thDay
24%38%14%27%25%
1760
21st to endDay
26%37%15%30%19%
1480
March1st to 10thDay
20%46%17%30%22%
1862
11th to 20thDay
21%45%14%35%20%
1980
21st to endDay
18%48%20%32%18%
2178
April1st to 10thDay
18%26%17%29%27%
2008
11th to 20thDay
15%3412%28%38%
2150
21st to endDay
13%25%12%35%32%
2340
May1st to 10thDay
11%37%12%31%36%
2340
11th to 20thDay
10%25%11%35%38%
2304
21st to endDay
12%25%10%31%41%
2530
June1st to 10thDay
8%228%25%54%
2340
11th to 20thDay
6%135%16%68%
2340
21st to endDay
9%235%15%65%
2340
July1st to 10thDay
16%45%10%13%51%
2276
11th to 20thDay
21%6%10%14%19%30%
2271
21st to endDay
29%9%12%16%16%18%
2404
August1st to 10thDay
18%6%9%11%19%38%
2313
11th to 20thDay
18%7%7%12%23%33%
2249
21st to endDay
18%5%8%12%29%29%
2376
September1st to 10thDay
20%48%11%20%36%
2002
11th to 20thDay
10%36%9%26%47%
1980
21st to endDay
10%35%11%27%43%
1980
October1st to 10thDay
16%35%13%24%39%
1980
11th to 20thDay
10%339%30%44%
1859
21st to endDay
9%25%13%30%40%
1976
November1st to 10thDay
13%2416%35%29%
1674
11th to 20thDay
13%15%17%30%34%
1710
21st to endDay
17%37%15%33%26%
1710
December1st to 10thDay
23%47%19%25%21%
1710
11th to 20thDay
25%7%11%23%24%10%
2168
21st to endDay
26%6%10%22%25%10%
3146
January1st to 10thNight
22%5%5%21%34%13%
2457
11th to 20thNight
20%45%23%31%16%
2391
21st to endNight
25%38%19%31%14%
2574
February1st to 10thNight
19%28%17%30%24%
2182
11th to 20thNight
23%3415%29%26%
2099
21st to endNight
22%36%15%31%22%
1776
March1st to 10thNight
20%47%17%35%17%
2098
11th to 20thNight
21%45%15%33%22%
1980
21st to endNight
17%47%20%32%20%
2178
April1st to 10thNight
17%36%14%35%25%
1948
11th to 20thNight
14%3413%33%32%
1761
21st to endNight
12%2413%35%34%
1620
May1st to 10thNight
12%36%13%28%37%
1620
11th to 20thNight
10%2413%32%39%
1595
21st to endNight
10%35%11%32%40%
1746
June1st to 10thNight
6%236%26%57%
1620
11th to 20thNight
7%136%15%68%
1620
21st to endNight
9%235%12%68%
1620
July1st to 10thNight
12%45%9%11%59%
1575
11th to 20thNight
19%6%9%14%22%30%
1566
21st to endNight
22%10%12%20%17%18%
1674
August1st to 10thNight
15%5%6%12%23%39%
1602
11th to 20thNight
14%5%7%15%23%36%
1647
21st to endNight
13%45%15%28%34%
1980
September1st to 10thNight
15%48%15%21%37%
1957
11th to 20thNight
9%2411%26%49%
1980
21st to endNight
8%25%9%25%51%
1980
October1st to 10thNight
15%35%13%25%41%
1980
11th to 20thNight
9%338%29%47%
2101
21st to endNight
9%26%14%26%44%
2376
November1st to 10thNight
14%2416%37%28%
2405
11th to 20thNight
13%25%15%33%33%
2470
21st to endNight
18%25%16%29%30%
2470
December1st to 10thNight
23%47%19%27%21%
2470
11th to 20thNight
26%5%9%19%30%13%
3041
21st to endNight
25%8%10%20%29%9%
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
9%5%20%35%27%4
270
11th to 20thDay
10%412%41%24%8%
249
21st to endDay
5%5%14%36%27%13%
264
February1st to 10thDay
6%10%23%33%22%8%
396
11th to 20thDay
10%10%28%31%17%4
415
21st to endDay
8%12%30%35%14%1
346
March1st to 10thDay
9%12%26%34%16%3
420
11th to 20thDay
7%11%23%35%17%6%
420
21st to endDay
5%13%34%30%14%5%
462
April1st to 10thDay
5%10%25%30%20%9%
420
11th to 20thDay
316%32%25%18%6%
412
21st to endDay
413%28%27%18%10%
420
May1st to 10thDay
29%29%32%19%9%
423
11th to 20thDay
28%24%38%15%13%
448
21st to endDay
49%25%32%19%11%
485
June1st to 10thDay
26%19%35%22%16%
450
11th to 20thDay
419%36%22%18%
450
21st to endDay
2217%37%25%16%
450
July1st to 10thDay
1114%35%29%20%
446
11th to 20thDay
317%29%32%29%
444
21st to endDay
425%27%32%31%
487
August1st to 10thDay
4110%32%32%21%
447
11th to 20thDay
2111%31%27%27%
437
21st to endDay
317%30%33%27%
495
September1st to 10thDay
3313%32%27%23%
450
11th to 20thDay
2218%38%26%14%
450
21st to endDay
26%18%32%25%17%
450
October1st to 10thDay
26%24%29%25%14%
450
11th to 20thDay
1417%30%29%19%
329
21st to endDay
25%14%30%33%16%
297
November1st to 10thDay
35%15%30%37%10%
270
11th to 20thDay
3212%34%36%13%
270
21st to endDay
6%415%31%33%12%
270
December1st to 10thDay
5%213%35%35%10%
270
11th to 20thDay
4313%39%32%9%
270
21st to endDay
14%5%16%39%22%4
297
January1st to 10thNight
6%317%41%26%7%
760
11th to 20thNight
6%114%45%28%5%
736
21st to endNight
8%316%48%22%4
792
February1st to 10thNight
5%115%49%25%5%
720
11th to 20thNight
6%221%48%22%2
704
21st to endNight
8%322%46%18%3
592
March1st to 10thNight
4422%48%22%2
720
11th to 20thNight
7%216%42%27%5%
720
21st to endNight
3417%50%24%2
792
April1st to 10thNight
35%19%46%26%2
720
11th to 20thNight
35%24%45%20%3
693
21st to endNight
3221%46%24%3
540
May1st to 10thNight
3321%47%26%1
540
11th to 20thNight
2216%43%34%3
531
21st to endNight
1319%46%28%3
584
June1st to 10thNight
1113%47%36%2
540
11th to 20thNight
1114%43%38%3
540
21st to endNight
118%41%45%4
540
July1st to 10thNight
2336%54%5%
525
11th to 20thNight
4229%61%5%
522
21st to endNight
21224%63%9%
591
August1st to 10thNight
21431%57%5%
537
11th to 20thNight
11232%55%9%
579
21st to endNight
31225%57%12%
792
September1st to 10thNight
35%31%48%12%
720
11th to 20thNight
18%39%43%9%
720
21st to endNight
129%40%39%9%
720
October1st to 10thNight
3213%45%33%3
720
11th to 20thNight
2110%44%37%7%
720
21st to endNight
2214%38%37%8%
792
November1st to 10thNight
3111%46%33%7%
740
11th to 20thNight
3112%44%33%8%
760
21st to endNight
5%215%44%30%5%
760
December1st to 10thNight
7%113%47%29%3
760
11th to 20thNight
8%112%46%28%4
760
21st to endNight
10%316%48%20%3
836
Page generated at 2024-01-11 11:32:04. Version ac07

Copyright 2024 Attilla Danko


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