Washoe Zephyr Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Washoe Zephyr Observatory clear sky chart from 2005-11-06 to 2024-01-16.

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
59%
23356
28%
74683
23%
23321
65%
23321
41%
38441

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
46%
756
19%
2646
16%
756
53%
756
28%
1501
January11th to 20thNight
51%
744
20%
2573
18%
744
58%
744
28%
1441
January21st to endNight
50%
792
25%
2574
23%
792
56%
792
31%
1483
February1st to 10thNight
53%
720
24%
2330
22%
720
60%
720
33%
1299
February11th to 20thNight
52%
701
26%
2099
22%
700
60%
700
37%
1138
February21st to endNight
48%
592
24%
1776
21%
592
55%
592
33%
997
March1st to 10thNight
42%
720
19%
2160
13%
720
52%
720
29%
1293
March11th to 20thNight
51%
720
22%
2021
18%
720
56%
720
34%
1182
March21st to endNight
43%
792
18%
2030
9%
792
49%
792
33%
1228
April1st to 10thNight
47%
720
24%
1800
11%
720
53%
720
36%
1101
April11th to 20thNight
48%
711
26%
1779
12%
711
54%
711
40%
1027
April21st to endNight
54%
720
25%
1800
11%
720
59%
720
45%
1018
May1st to 10thNight
51%
603
27%
1683
16%
603
57%
603
42%
899
May11th to 20thNight
60%
402
29%
1464
25%
402
67%
402
39%
691
May21st to endNight
63%
388
22%
1552
24%
388
68%
388
31%
777
June1st to 10thNight
62%
360
27%
1440
29%
360
71%
360
38%
665
June11th to 20thNight
70%
360
34%
1440
37%
360
81%
360
56%
515
June21st to endNight
74%
360
32%
1440
38%
360
82%
360
58%
519
July1st to 10thNight
80%
350
35%
1400
42%
350
87%
350
70%
447
July11th to 20thNight
79%
348
36%
1392
43%
348
83%
348
62%
483
July21st to endNight
82%
434
39%
1526
43%
410
84%
410
56%
599
August1st to 10thNight
78%
564
33%
1629
24%
561
82%
561
59%
769
August11th to 20thNight
75%
712
36%
1780
19%
712
79%
712
70%
849
August21st to endNight
76%
792
42%
1980
25%
792
78%
792
77%
911
September1st to 10thNight
78%
720
44%
1800
27%
720
83%
720
80%
806
September11th to 20thNight
72%
720
43%
1835
30%
720
78%
720
68%
870
September21st to endNight
68%
720
41%
1980
31%
720
77%
720
64%
917
October1st to 10thNight
65%
720
32%
2114
27%
720
74%
720
53%
1019
October11th to 20thNight
71%
720
38%
2160
38%
720
77%
720
58%
958
October21st to endNight
68%
792
37%
2431
35%
792
75%
792
57%
1082
November1st to 10thNight
60%
740
29%
2405
29%
740
66%
740
40%
1206
November11th to 20thNight
58%
760
29%
2470
24%
760
67%
760
43%
1214
November21st to endNight
55%
760
29%
2522
24%
760
64%
760
38%
1296
December1st to 10thNight
50%
760
21%
2660
18%
760
57%
760
28%
1478
December11th to 20thNight
46%
760
19%
3204
18%
759
53%
759
19%
2015
December21st to endNight
40%
823
12%
4788
15%
817
47%
817
14%
2748

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
232342445%7%63%
74807
Night
242442445%8%62%
75015
TransparencyDay
21%6%11%19%24%18%
74514
Night
21%7%13%21%23%14%
74829
SeeingDay
8%16%27%27%18%5%
13903
Night
5%9%23%35%24%5%
23377

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
1425%6%35%7%7%11%50%
1519
11th to 20thDay
1435%5%35%6%49%55%
1510
21st to endDay
36%25%5%35%6%8%10%47%
1782
February1st to 10thDay
24334345%6%11%55%
1629
11th to 20thDay
15%45%425%6%6%8%54%
1750
21st to endDay
16%245%25%5%7%10%55%
1480
March1st to 10thDay
35%36%446%7%8%11%45%
1800
11th to 20thDay
15%25%5%36%7%7%10%48%
1935
21st to endDay
14245%35%5%7%10%53%
2325
April1st to 10thDay
2425%5%45%5%6%9%53%
2160
11th to 20thDay
23244345%6%9%58%
2129
21st to endDay
34234245%5%6%63%
2160
May1st to 10thDay
441342345%8%61%
2276
11th to 20thDay
44135%2445%8%60%
2426
21st to endDay
6%5%35%5%345%5%7%53%
2723
June1st to 10thDay
3313425%45%8%62%
2520
11th to 20thDay
221232233477%
2520
21st to endDay
211231234476%
2520
July1st to 10thDay
1111212335%81%
2520
11th to 20thDay
211221224480%
2520
21st to endDay
321232334473%
2697
August1st to 10thDay
321232333474%
2298
11th to 20thDay
11121233480%
2122
21st to endDay
11111122386%
2376
September1st to 10thDay
111112235%82%
2160
11th to 20thDay
2112322335%76%
2124
21st to endDay
3112222325%77%
1980
October1st to 10thDay
4313323345%68%
1841
11th to 20thDay
2312323346%72%
1800
21st to endDay
221232335%7%71%
1923
November1st to 10thDay
2423425%5%5%7%61%
1674
11th to 20thDay
2313325%5%7%10%61%
1710
21st to endDay
24244346%5%11%57%
1656
December1st to 10thDay
35%245%35%5%7%10%52%
1520
11th to 20thDay
27%37%7%46%7%9%10%38%
1928
21st to endDay
26%47%5%35%6%7%12%42%
2794
January1st to 10thNight
25%35%5%35%5%7%12%48%
2646
11th to 20thNight
1426%5%346%7%10%51%
2573
21st to endNight
46%26%5%3447%9%51%
2574
February1st to 10thNight
2425%425%5%5%9%57%
2330
11th to 20thNight
15%35%3236%7%9%56%
2098
21st to endNight
24145%345%5%10%56%
1776
March1st to 10thNight
25%25%5%35%5%7%10%51%
2160
11th to 20thNight
14245%35%6%7%10%53%
2021
21st to endNight
2433325%5%5%8%59%
2030
April1st to 10thNight
24234345%8%10%54%
1800
11th to 20thNight
23233245%6%8%61%
1779
21st to endNight
3312324447%66%
1800
May1st to 10thNight
5%41332445%6%63%
1683
11th to 20thNight
2315%3345%5%8%62%
1464
21st to endNight
6%42442345%8%59%
1552
June1st to 10thNight
4323424346%65%
1440
11th to 20thNight
1112222345%78%
1440
21st to endNight
321221223478%
1440
July1st to 10thNight
112212235%81%
1440
11th to 20thNight
111122234479%
1440
21st to endNight
321232334473%
1616
August1st to 10thNight
32232444471%
1638
11th to 20thNight
211132224478%
1780
21st to endNight
221111223383%
1980
September1st to 10thNight
2111222485%
1800
11th to 20thNight
221121233478%
1835
21st to endNight
2212213335%76%
1980
October1st to 10thNight
422331333472%
2114
11th to 20thNight
2312222345%76%
2160
21st to endNight
2312222336%73%
2431
November1st to 10thNight
231342446%7%63%
2405
11th to 20thNight
131342436%10%64%
2470
21st to endNight
24234245%7%9%59%
2522
December1st to 10thNight
35%35%43447%8%56%
2660
11th to 20thNight
37%35%6%36%7%8%11%42%
3276
21st to endNight
27%37%7%46%6%8%9%42%
4862

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
29%11%20%27%13%1
1519
11th to 20thDay
28%9%18%22%17%6%
1510
21st to endDay
32%8%15%24%19%2
1782
February1st to 10thDay
26%9%15%27%17%6%
1629
11th to 20thDay
28%6%16%29%17%5%
1760
21st to endDay
26%9%21%24%17%4
1480
March1st to 10thDay
34%11%18%21%15%2
1800
11th to 20thDay
30%10%16%19%20%5%
1935
21st to endDay
26%11%24%24%12%3
2325
April1st to 10thDay
28%10%17%20%20%6%
2160
11th to 20thDay
24%8%14%26%22%6%
2132
21st to endDay
21%7%14%29%25%4
2160
May1st to 10thDay
22%6%10%29%28%5%
2276
11th to 20thDay
24%5%10%25%28%7%
2429
21st to endDay
31%7%11%22%23%6%
2724
June1st to 10thDay
21%5%10%20%32%11%
2520
11th to 20thDay
12%37%20%33%24%
2520
21st to endDay
12%3410%31%39%
2520
July1st to 10thDay
8%348%25%52%
2451
11th to 20thDay
10%2311%24%50%
2445
21st to endDay
15%35%7%22%49%
2547
August1st to 10thDay
14%35%10%22%46%
2282
11th to 20thDay
9%35%6%29%49%
2122
21st to endDay
7%137%34%47%
2376
September1st to 10thDay
8%248%29%49%
2160
11th to 20thDay
13%36%16%35%27%
2124
21st to endDay
13%26%17%37%25%
1980
October1st to 10thDay
19%47%17%32%20%
1841
11th to 20thDay
15%39%24%31%19%
1800
21st to endDay
16%410%27%30%14%
1923
November1st to 10thDay
23%7%14%22%26%8%
1674
11th to 20thDay
19%8%18%25%26%5%
1710
21st to endDay
24%8%13%25%26%5%
1656
December1st to 10thDay
28%9%15%24%19%5%
1520
11th to 20thDay
41%11%14%19%12%3
1928
21st to endDay
32%11%20%23%13%2
2794
January1st to 10thNight
30%10%19%26%15%1
2646
11th to 20thNight
28%10%18%24%13%6%
2573
21st to endNight
31%8%16%23%19%3
2574
February1st to 10thNight
26%9%15%25%19%6%
2330
11th to 20thNight
23%9%17%30%19%3
2099
21st to endNight
27%7%19%27%15%5%
1776
March1st to 10thNight
28%11%18%23%16%4
2160
11th to 20thNight
24%12%17%21%20%5%
2021
21st to endNight
24%12%23%24%14%3
2030
April1st to 10thNight
23%12%18%26%16%5%
1800
11th to 20thNight
21%9%17%28%19%7%
1779
21st to endNight
20%8%17%32%20%3
1800
May1st to 10thNight
22%6%12%26%28%6%
1683
11th to 20thNight
20%7%12%29%24%7%
1464
21st to endNight
25%9%13%27%21%5%
1552
June1st to 10thNight
21%7%8%23%30%11%
1440
11th to 20thNight
10%46%21%36%22%
1440
21st to endNight
12%26%13%33%33%
1440
July1st to 10thNight
8%248%31%47%
1400
11th to 20thNight
10%35%11%26%46%
1392
21st to endNight
15%26%7%24%46%
1526
August1st to 10thNight
16%47%13%23%38%
1629
11th to 20thNight
12%25%9%30%43%
1780
21st to endNight
9%149%34%44%
1980
September1st to 10thNight
6%247%36%45%
1800
11th to 20thNight
11%27%20%34%25%
1835
21st to endNight
13%26%18%36%24%
1980
October1st to 10thNight
18%48%20%28%22%
2114
11th to 20thNight
13%49%21%35%18%
2160
21st to endNight
14%411%25%33%13%
2431
November1st to 10thNight
21%7%15%23%23%11%
2405
11th to 20thNight
19%7%14%28%27%5%
2470
21st to endNight
22%9%12%27%25%6%
2522
December1st to 10thNight
28%10%15%23%19%5%
2660
11th to 20thNight
35%13%15%20%15%3
3276
21st to endNight
36%11%20%18%12%3
4862

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
13%19%32%21%13%2
180
11th to 20thDay
11%14%32%23%17%4
198
21st to endDay
7%13%32%27%17%4
374
February1st to 10thDay
12%13%28%28%16%3
344
11th to 20thDay
8%21%27%31%12%1
415
21st to endDay
9%22%26%32%11%
346
March1st to 10thDay
11%22%34%22%10%2
420
11th to 20thDay
9%24%29%21%14%3
420
21st to endDay
11%26%28%25%10%
462
April1st to 10thDay
12%25%28%21%10%4
420
11th to 20thDay
14%27%26%18%12%2
412
21st to endDay
12%20%28%23%13%4
420
May1st to 10thDay
13%22%26%25%11%3
423
11th to 20thDay
13%23%24%22%12%5%
448
21st to endDay
11%17%20%26%20%6%
485
June1st to 10thDay
9%16%27%23%20%5%
450
11th to 20thDay
9%17%32%23%15%4
450
21st to endDay
311%27%30%24%5%
450
July1st to 10thDay
212%31%29%21%5%
446
11th to 20thDay
29%28%31%22%8%
444
21st to endDay
27%27%30%27%7%
487
August1st to 10thDay
310%26%28%26%7%
447
11th to 20thDay
18%25%29%26%12%
437
21st to endDay
37%31%31%23%5%
495
September1st to 10thDay
28%27%32%24%7%
450
11th to 20thDay
5%15%23%28%24%5%
450
21st to endDay
5%13%26%36%16%4
450
October1st to 10thDay
6%14%27%25%23%5%
450
11th to 20thDay
8%12%21%30%24%6%
450
21st to endDay
7%13%26%26%23%5%
438
November1st to 10thDay
13%12%22%24%20%10%
270
11th to 20thDay
415%21%30%22%9%
270
21st to endDay
5%14%24%30%20%7%
244
December1st to 10thDay
13%12%24%22%22%7%
180
11th to 20thDay
5%19%33%22%13%7%
180
21st to endDay
15%16%23%29%15%3
198
January1st to 10thNight
6%13%29%26%18%8%
760
11th to 20thNight
5%12%24%37%17%5%
744
21st to endNight
6%6%29%33%20%5%
792
February1st to 10thNight
5%11%25%35%20%4
720
11th to 20thNight
411%26%34%19%5%
704
21st to endNight
7%15%25%35%14%3
592
March1st to 10thNight
5%15%34%28%15%4
720
11th to 20thNight
416%26%26%25%3
720
21st to endNight
420%29%31%15%1
792
April1st to 10thNight
5%14%29%31%19%1
720
11th to 20thNight
6%16%25%31%17%4
711
21st to endNight
6%13%25%31%20%4
720
May1st to 10thNight
6%14%23%33%21%3
603
11th to 20thNight
49%23%39%23%2
402
21st to endNight
7%7%16%39%29%3
389
June1st to 10thNight
6%5%22%38%26%4
360
11th to 20thNight
16%21%42%28%2
360
21st to endNight
3316%44%32%2
360
July1st to 10thNight
1213%50%32%3
350
11th to 20thNight
1118%52%28%1
348
21st to endNight
419%45%35%5%
434
August1st to 10thNight
4113%42%37%3
564
11th to 20thNight
2315%45%30%5%
712
21st to endNight
3218%46%28%4
792
September1st to 10thNight
2216%37%37%6%
720
11th to 20thNight
35%18%32%36%7%
720
21st to endNight
36%21%33%30%8%
720
October1st to 10thNight
46%20%36%28%6%
720
11th to 20thNight
48%14%38%28%7%
720
21st to endNight
48%19%31%28%11%
792
November1st to 10thNight
5%12%20%28%29%7%
740
11th to 20thNight
49%26%35%20%5%
760
21st to endNight
6%9%26%31%24%5%
760
December1st to 10thNight
7%12%25%34%17%5%
760
11th to 20thNight
7%14%26%31%16%6%
760
21st to endNight
8%12%31%33%13%3
836
Page generated at 2024-01-13 16:28:34. Version ac07

Copyright 2024 Attilla Danko


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