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 2005-11-05 to 2017-09-23.

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
74%
15819
36%
47005
31%
15782
79%
15782
56%
21940

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
32%
716
75%
716
47%
1119
January16th to endNight
66%
768
35%
2496
33%
768
74%
768
43%
1247
February1st to 15thNight
71%
699
36%
2127
33%
699
78%
699
53%
1009
February16th to endNight
62%
632
35%
1895
35%
632
68%
632
45%
991
March1st to 15thNight
69%
720
35%
2058
30%
720
77%
720
55%
993
March16th to endNight
72%
768
36%
2112
29%
768
79%
768
59%
1026
April1st to 15thNight
61%
719
32%
1898
18%
719
69%
719
56%
954
April16th to endNight
68%
588
42%
1668
26%
588
77%
588
68%
723
May1st to 15thNight
72%
539
36%
1619
26%
539
78%
539
64%
691
May16th to endNight
69%
561
36%
1685
27%
561
75%
561
64%
723
June1st to 15thNight
77%
540
32%
1620
28%
540
79%
540
71%
657
June16th to endNight
85%
540
34%
1620
32%
540
86%
540
76%
636
July1st to 15thNight
85%
510
26%
1530
23%
510
85%
510
53%
734
July16th to endNight
82%
564
29%
1593
25%
531
83%
531
45%
824
August1st to 15thNight
84%
539
36%
1611
29%
536
85%
536
57%
741
August16th to endNight
87%
735
41%
1881
30%
735
88%
735
62%
947
September1st to 15thNight
84%
720
33%
1965
27%
720
85%
720
59%
972
September16th to endNight
81%
688
47%
1903
37%
688
88%
688
78%
792
October1st to 15thNight
78%
660
42%
1834
34%
660
83%
660
63%
851
October16th to endNight
79%
704
43%
2112
39%
704
84%
704
67%
892
November1st to 15thNight
78%
700
37%
2275
35%
700
85%
700
59%
975
November16th to endNight
75%
720
40%
2340
39%
720
80%
720
57%
1003
December1st to 15thNight
72%
720
34%
2340
33%
720
78%
720
46%
1137
December16th to endNight
65%
768
33%
2496
32%
768
70%
768
39%
1303

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
3212213346%69%
47904
Night
3212212346%70%
47200
TransparencyDay
17%36%14%27%31%
47599
Night
16%26%15%28%29%
47006
SeeingDay
5%8%25%35%18%6%
5594
Night
4214%37%34%6%
15830

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
4413212345%66%
1611
16th to endDay
7%33312336%63%
1728
February1st to 15thDay
4312222447%65%
1734
16th to endDay
9%412324227%58%
1579
March1st to 15thDay
3212212337%69%
1902
16th to endDay
2312212447%66%
2112
April1st to 15thDay
4212313346%66%
2048
16th to endDay
211112225%77%
2292
May1st to 15thDay
111112236%76%
2331
16th to endDay
221112225%76%
2429
June1st to 15thDay
111112482%
2340
16th to endDay
111122384%
2340
July1st to 15thDay
2113325%46%6%62%
2340
16th to endDay
4424446%5%7%7%48%
2467
August1st to 15thDay
321233445%6%63%
2340
16th to endDay
2212323446%65%
2318
September1st to 15thDay
3123245%5%7%63%
1995
16th to endDay
111111225%79%
1893
October1st to 15thDay
211221233472%
1796
16th to endDay
111212245%76%
1757
November1st to 15thDay
2212212236%73%
1584
16th to endDay
42121223474%
1620
December1st to 15thDay
5%312313348%60%
1620
16th to endDay
9%412213347%58%
1728
January1st to 15thNight
4313212335%66%
2327
16th to endNight
7%412323345%62%
2496
February1st to 15thNight
3313212235%69%
2116
16th to endNight
6%313323347%61%
1895
March1st to 15thNight
321121345%7%66%
2058
16th to endNight
212213347%69%
2112
April1st to 15thNight
322213335%70%
1898
16th to endNight
2111223478%
1668
May1st to 15thNight
2111112235%76%
1619
16th to endNight
111112336%75%
1684
June1st to 15thNight
1111222481%
1620
16th to endNight
111123383%
1620
July1st to 15thNight
22122235%5%6%64%
1620
16th to endNight
321443446%11%53%
1701
August1st to 15thNight
1212212348%69%
1620
16th to endNight
2111312348%69%
1881
September1st to 15thNight
2112313447%67%
1965
16th to endNight
1111122384%
1903
October1st to 15thNight
21111324475%
1834
16th to endNight
2111123478%
2112
November1st to 15thNight
222212235%73%
2275
16th to endNight
3212112235%73%
2340
December1st to 15thNight
6%2221345%6%63%
2340
16th to endNight
9%412212445%60%
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
21%36%19%37%12%
1612
16th to endDay
24%38%20%29%13%
1728
February1st to 15thDay
20%39%17%28%20%
1734
16th to endDay
28%17%15%28%17%
1579
March1st to 15thDay
17%2416%38%20%
1902
16th to endDay
18%36%19%32%19%
2112
April1st to 15thDay
20%25%15%28%27%
2048
16th to endDay
12%1413%32%34%
2292
May1st to 15thDay
11%16%12%32%34%
2331
16th to endDay
12%25%8%33%37%
2432
June1st to 15thDay
8%126%18%63%
2340
16th to endDay
7%12414%69%
2340
July1st to 15thDay
20%46%11%14%41%
2201
16th to endDay
29%6%11%14%17%20%
2312
August1st to 15thDay
20%5%7%12%21%32%
2325
16th to endDay
20%47%11%27%29%
2318
September1st to 15thDay
19%48%12%24%30%
1995
16th to endDay
9%249%27%46%
1893
October1st to 15thDay
15%3411%29%35%
1796
16th to endDay
11%25%13%31%35%
1757
November1st to 15thDay
15%1417%34%26%
1584
16th to endDay
15%26%17%31%27%
1620
December1st to 15thDay
24%39%24%26%12%
1620
16th to endDay
26%49%26%23%10%
1728
January1st to 15thNight
21%3420%36%13%
2327
16th to endNight
24%37%20%27%16%
2496
February1st to 15thNight
19%28%20%27%22%
2127
16th to endNight
25%25%16%31%17%
1895
March1st to 15thNight
17%36%14%40%17%
2058
16th to endNight
15%36%20%33%21%
2112
April1st to 15thNight
17%26%14%36%22%
1898
16th to endNight
10%2414%33%35%
1668
May1st to 15thNight
11%26%13%30%35%
1620
16th to endNight
11%249%34%36%
1685
June1st to 15thNight
9%135%18%61%
1620
16th to endNight
7%115%11%71%
1620
July1st to 15thNight
17%48%11%13%45%
1530
16th to endNight
21%6%9%21%20%20%
1593
August1st to 15thNight
15%45%13%25%35%
1611
16th to endNight
14%35%15%28%32%
1881
September1st to 15thNight
16%39%16%21%31%
1965
16th to endNight
7%138%27%51%
1903
October1st to 15thNight
13%2412%30%35%
1834
16th to endNight
11%16%12%26%40%
2112
November1st to 15thNight
15%1416%37%24%
2275
16th to endNight
15%15%17%29%30%
2340
December1st to 15thNight
22%38%22%29%13%
2340
16th to endNight
26%410%22%26%8%
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
25%7%22%30%12%2
90
16th to endDay
12%215%34%19%15%
96
February1st to 15thDay
8%10%29%31%16%4
249
16th to endDay
12%15%34%23%12%1
238
March1st to 15thDay
6%15%26%32%15%3
270
16th to endDay
417%33%27%11%5%
288
April1st to 15thDay
10%20%28%23%12%4
269
16th to endDay
5%25%35%22%10%1
270
May1st to 15thDay
413%33%30%14%4
288
16th to endDay
413%29%36%11%5%
330
June1st to 15thDay
17%33%37%12%6%
315
16th to endDay
322%45%17%10%
315
July1st to 15thDay
1121%44%23%8%
305
16th to endDay
5%211%40%29%10%
327
August1st to 15thDay
4121%39%24%8%
315
16th to endDay
4111%41%25%15%
332
September1st to 15thDay
3323%41%20%8%
315
16th to endDay
37%26%39%15%8%
284
October1st to 15thDay
110%36%29%16%5%
236
16th to endDay
6%412%33%37%6%
96
November1st to 15thDay
35%14%25%37%13%
90
16th to endDay
8%427%38%18%1
90
December1st to 15thDay
3117%41%33%3
90
16th to endDay
12%414%45%19%3
96
January1st to 15thNight
6%217%38%26%8%
720
16th to endNight
9%216%38%26%5%
768
February1st to 15thNight
6%115%45%26%4
704
16th to endNight
9%222%41%21%3
632
March1st to 15thNight
4320%39%27%3
720
16th to endNight
3416%43%27%4
768
April1st to 15thNight
46%24%36%22%5%
719
16th to endNight
2422%43%23%4
588
May1st to 15thNight
3417%41%29%2
540
16th to endNight
1322%37%30%4
563
June1st to 15thNight
1217%42%32%3
540
16th to endNight
110%39%43%5%
540
July1st to 15thNight
4430%54%5%
510
16th to endNight
3423%61%6%
564
August1st to 15thNight
2428%57%6%
539
16th to endNight
3422%54%15%
735
September1st to 15thNight
26%30%46%13%
720
16th to endNight
2113%33%37%12%
688
October1st to 15thNight
3213%42%31%6%
660
16th to endNight
3112%37%36%8%
704
November1st to 15thNight
313%41%33%7%
700
16th to endNight
4114%38%31%8%
720
December1st to 15thNight
8%113%41%29%5%
720
16th to endNight
11%314%40%25%4
768
Page generated at 2017-09-24 06:15:46. Version ac04

Copyright 2017 A. Danko


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