Pahrump Valley Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pahrump Valley Observatory clear sky chart from 2005-11-05 to 2018-01-12.

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
62%
16154
37%
48109
27%
16117
73%
16117
51%
21495

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
57%
760
32%
2471
25%
760
68%
760
40%
1153
January16th to endNight
52%
768
36%
2430
26%
768
67%
768
39%
1174
February1st to 15thNight
52%
700
34%
2112
28%
700
62%
700
41%
1022
February16th to endNight
50%
632
35%
1895
27%
632
64%
632
40%
967
March1st to 15thNight
54%
720
34%
2133
24%
720
70%
720
47%
967
March16th to endNight
55%
768
37%
2082
22%
768
69%
768
50%
989
April1st to 15thNight
49%
719
35%
1799
14%
719
60%
719
49%
915
April16th to endNight
53%
661
40%
1741
17%
661
66%
661
57%
785
May1st to 15thNight
55%
539
38%
1619
21%
539
65%
539
55%
655
May16th to endNight
56%
562
35%
1685
20%
561
68%
561
52%
693
June1st to 15thNight
57%
540
33%
1620
22%
540
67%
540
60%
641
June16th to endNight
68%
374
40%
1454
34%
374
86%
374
66%
434
July1st to 15thNight
76%
385
32%
1405
33%
385
81%
385
54%
533
July16th to endNight
68%
564
33%
1593
25%
531
77%
531
50%
755
August1st to 15thNight
77%
622
39%
1695
26%
619
81%
619
67%
734
August16th to endNight
79%
764
42%
1910
24%
764
85%
764
66%
910
September1st to 15thNight
79%
720
38%
1890
27%
720
83%
720
62%
887
September16th to endNight
76%
716
49%
1980
36%
716
88%
716
74%
803
October1st to 15thNight
71%
720
41%
1980
33%
720
78%
720
64%
882
October16th to endNight
70%
768
45%
2371
35%
768
84%
768
58%
974
November1st to 15thNight
67%
760
38%
2470
35%
760
76%
760
56%
1003
November16th to endNight
62%
780
42%
2535
35%
780
75%
780
49%
1068
December1st to 15thNight
56%
780
35%
2535
28%
780
67%
780
39%
1179
December16th to endNight
52%
832
34%
2704
27%
832
64%
832
33%
1372

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
211212235%74%
49222
Night
2112212235%73%
48298
TransparencyDay
13%25%14%27%36%
48911
Night
13%25%15%27%34%
48110
SeeingDay
317%25%32%15%4
6098
Night
318%13%29%28%7%
16164

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
3212212247%68%
1710
16th to endDay
5%212323335%66%
1791
February1st to 15thDay
4211113346%67%
1751
16th to endDay
8%32223447%60%
1579
March1st to 15thDay
2111112347%71%
1827
16th to endDay
211222335%8%67%
2139
April1st to 15thDay
3212213346%69%
2149
16th to endDay
111212335%76%
2217
May1st to 15thDay
112346%77%
2331
16th to endDay
111112345%75%
2429
June1st to 15thDay
111122383%
2340
16th to endDay
1112287%
2500
July1st to 15thDay
2111213336%71%
2466
16th to endDay
3112323345%67%
2467
August1st to 15thDay
11112135%79%
2253
16th to endDay
11111123479%
2292
September1st to 15thDay
1111233478%
2070
16th to endDay
11122385%
1980
October1st to 15thDay
21221223376%
1980
16th to endDay
211112235%78%
1850
November1st to 15thDay
1211111235%75%
1719
16th to endDay
3111212235%74%
1755
December1st to 15thDay
4213313236%67%
1755
16th to endDay
7%313212246%63%
1872
January1st to 15thNight
3112312445%67%
2471
16th to endNight
6%412312245%65%
2430
February1st to 15thNight
5%312212337%65%
2101
16th to endNight
7%312312236%64%
1895
March1st to 15thNight
3111223448%68%
2133
16th to endNight
2112112346%70%
2082
April1st to 15thNight
31122343471%
1799
16th to endNight
11111213480%
1741
May1st to 15thNight
11112236%78%
1619
16th to endNight
11212245%78%
1684
June1st to 15thNight
11111135%82%
1620
16th to endNight
111290%
1454
July1st to 15thNight
211222235%74%
1489
16th to endNight
1223413346%66%
1701
August1st to 15thNight
11211235%78%
1704
16th to endNight
1121133479%
1910
September1st to 15thNight
111222335%74%
1890
16th to endNight
11111287%
1980
October1st to 15thNight
211112235%77%
1980
16th to endNight
11121223478%
2371
November1st to 15thNight
1111111235%76%
2470
16th to endNight
2112212235%74%
2535
December1st to 15thNight
5%22312345%67%
2535
16th to endNight
8%213322336%61%
2704

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%37%26%33%12%
1711
16th to endDay
21%37%23%29%14%
1791
February1st to 15thDay
16%48%20%31%18%
1751
16th to endDay
23%48%16%29%17%
1579
March1st to 15thDay
12%39%20%33%21%
1827
16th to endDay
15%29%21%31%19%
2139
April1st to 15thDay
17%35%17%31%24%
2149
16th to endDay
10%25%17%30%32%
2217
May1st to 15thDay
8%25%16%30%37%
2331
16th to endDay
10%26%10%35%34%
2432
June1st to 15thDay
7%137%22%56%
2340
16th to endDay
42412%75%
2500
July1st to 15thDay
12%247%15%57%
2321
16th to endDay
16%45%10%20%43%
2312
August1st to 15thDay
8%127%20%58%
2238
16th to endDay
9%138%22%54%
2292
September1st to 15thDay
10%148%22%51%
2070
16th to endDay
6%128%29%52%
1980
October1st to 15thDay
13%2311%30%39%
1980
16th to endDay
11%2412%31%38%
1850
November1st to 15thDay
12%16%15%40%22%
1719
16th to endDay
13%25%20%33%23%
1755
December1st to 15thDay
19%310%18%30%16%
1755
16th to endDay
22%310%27%22%12%
1872
January1st to 15thNight
18%47%22%32%14%
2471
16th to endNight
22%27%22%24%20%
2430
February1st to 15thNight
19%39%19%27%21%
2112
16th to endNight
22%36%18%32%16%
1895
March1st to 15thNight
14%28%18%33%21%
2133
16th to endNight
14%27%23%31%20%
2082
April1st to 15thNight
14%36%19%32%23%
1799
16th to endNight
9%2419%30%34%
1741
May1st to 15thNight
8%2415%31%36%
1620
16th to endNight
9%26%11%32%37%
1685
June1st to 15thNight
7%137%20%59%
1620
16th to endNight
41411%76%
1454
July1st to 15thNight
11%237%16%57%
1405
16th to endNight
16%4312%19%44%
1593
August1st to 15thNight
9%1210%19%57%
1695
16th to endNight
10%247%22%54%
1910
September1st to 15thNight
11%35%10%18%51%
1890
16th to endNight
6%17%27%57%
1980
October1st to 15thNight
10%25%11%28%42%
1980
16th to endNight
10%2411%25%45%
2371
November1st to 15thNight
11%25%17%37%25%
2470
16th to endNight
13%25%17%30%30%
2535
December1st to 15thNight
18%38%18%30%18%
2535
16th to endNight
24%311%21%24%14%
2704

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
13%11%25%29%19%
123
16th to endDay
12%15%22%25%17%6%
159
February1st to 15thDay
7%22%24%27%13%5%
266
16th to endDay
9%27%27%20%14%1
238
March1st to 15thDay
424%27%22%18%2
270
16th to endDay
5%27%30%25%10%
288
April1st to 15thDay
434%24%23%9%2
269
16th to endDay
338%30%17%8%1
270
May1st to 15thDay
122%36%26%9%3
288
16th to endDay
324%27%29%10%4
330
June1st to 15thDay
218%33%31%10%3
315
16th to endDay
14%22%37%16%7%
315
July1st to 15thDay
29%26%40%15%6%
305
16th to endDay
210%16%51%14%4
327
August1st to 15thDay
110%26%41%15%4
315
16th to endDay
17%20%43%17%8%
332
September1st to 15thDay
9%23%43%16%5%
315
16th to endDay
213%24%36%20%3
315
October1st to 15thDay
214%30%33%15%3
315
16th to endDay
47%16%31%27%12%
194
November1st to 15thDay
18%20%29%27%13%
135
16th to endDay
29%21%30%27%8%
135
December1st to 15thDay
111%18%36%23%8%
135
16th to endDay
9%9%13%32%26%8%
144
January1st to 15thNight
418%14%29%23%9%
764
16th to endNight
7%19%15%28%21%7%
768
February1st to 15thNight
6%20%16%31%18%6%
704
16th to endNight
7%19%20%31%17%4
632
March1st to 15thNight
322%17%30%19%7%
720
16th to endNight
225%14%32%20%4
768
April1st to 15thNight
227%18%25%20%5%
719
16th to endNight
124%19%28%21%5%
661
May1st to 15thNight
122%19%30%23%3
540
16th to endNight
126%14%29%25%2
563
June1st to 15thNight
21%18%30%26%2
540
16th to endNight
18%10%31%33%5%
374
July1st to 15thNight
111%6%31%42%5%
385
16th to endNight
116%6%28%43%3
564
August1st to 15thNight
9%7%34%42%4
622
16th to endNight
19%6%24%44%13%
764
September1st to 15thNight
19%6%28%42%12%
720
16th to endNight
19%10%25%39%14%
716
October1st to 15thNight
211%13%35%28%9%
720
16th to endNight
112%11%27%30%16%
768
November1st to 15thNight
15%13%29%31%9%
760
16th to endNight
318%12%28%28%8%
780
December1st to 15thNight
5%21%11%30%24%6%
780
16th to endNight
7%23%12%30%20%6%
832
Page generated at 2018-01-12 19:01:31. Version ac04

Copyright 2018 A. Danko


Pahrump Valley Observatory Clear Sky Chart |Charts Home