Prineville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Prineville clear sky chart from 2005-11-05 to 2018-02-13.

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
56%
15316
17%
48810
17%
15291
58%
15291
26%
30978

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
44%
776
11%
2716
11%
776
46%
776
15%
1969
January16th to endNight
49%
832
15%
2844
15%
832
51%
832
19%
1917
February1st to 15thNight
45%
745
9%
2444
10%
744
47%
744
17%
1768
February16th to endNight
43%
632
14%
1939
13%
632
46%
632
18%
1407
March1st to 15thNight
40%
720
9%
2105
8%
720
42%
720
16%
1589
March16th to endNight
41%
768
10%
2034
6%
768
42%
768
18%
1543
April1st to 15thNight
43%
719
11%
1799
7%
719
43%
719
20%
1350
April16th to endNight
52%
682
15%
1762
10%
682
53%
682
28%
1202
May1st to 15thNight
60%
359
18%
1439
20%
359
65%
359
27%
778
May16th to endNight
59%
374
13%
1496
18%
374
62%
374
18%
944
June1st to 15thNight
59%
360
13%
1440
19%
360
63%
360
25%
817
June16th to endNight
67%
360
20%
1440
32%
360
71%
360
38%
662
July1st to 15thNight
89%
340
23%
1360
37%
340
91%
340
59%
497
July16th to endNight
82%
376
34%
1416
47%
354
88%
354
61%
508
August1st to 15thNight
87%
471
33%
1545
34%
469
89%
469
61%
631
August16th to endNight
82%
726
39%
1872
27%
726
83%
726
72%
862
September1st to 15thNight
83%
720
38%
1800
24%
720
84%
720
70%
866
September16th to endNight
69%
716
31%
1947
26%
716
70%
716
43%
1109
October1st to 15thNight
61%
720
21%
2160
21%
720
64%
720
35%
1268
October16th to endNight
58%
768
21%
2376
22%
768
60%
768
26%
1534
November1st to 15thNight
45%
760
14%
2504
14%
760
47%
760
16%
1806
November16th to endNight
47%
780
10%
2730
11%
780
49%
780
18%
1872
December1st to 15thNight
49%
780
12%
2730
13%
780
50%
780
17%
1898
December16th to endNight
41%
832
11%
2912
11%
832
43%
832
14%
2181

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
9%7%35%42445%6%46%
49255
Night
10%8%35%5%2445%6%43%
48978
Cloud CoverDay
10%8%25%424446%45%
49255
Night
11%8%35%42445%6%42%
48982
TransparencyDay
39%411%21%16%6%
48926
Night
41%413%21%14%4
48811
SeeingDay
14%12%24%25%16%6%
5992
Night
14%6%13%36%24%3
15329

By Month

Percentage Cloud Cover NW (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
15%8%37%7%45%5%5%8%28%
1552
16th to endDay
12%12%48%5%25%45%6%31%
1730
February1st to 15thDay
10%11%49%5%35%5%49%29%
1685
16th to endDay
9%12%48%6%346%7%7%27%
1535
March1st to 15thDay
14%12%5%7%7%46%5%5%7%23%
1854
16th to endDay
12%14%5%8%6%445%5%6%26%
2189
April1st to 15thDay
11%13%48%7%35%5%5%7%28%
2149
16th to endDay
9%9%36%42446%7%41%
2196
May1st to 15thDay
10%7%25%424347%46%
2511
16th to endDay
14%7%46%5%34446%36%
2615
June1st to 15thDay
12%6%35%43445%6%44%
2520
16th to endDay
7%413323346%58%
2520
July1st to 15thDay
222212335%72%
2520
16th to endDay
21221233475%
2657
August1st to 15thDay
112322246%72%
2406
16th to endDay
21221222477%
2330
September1st to 15thDay
122112235%75%
2160
16th to endDay
7%42442345%6%53%
2011
October1st to 15thDay
11%7%26%5%3445%6%42%
1800
16th to endDay
14%7%25%5%34445%42%
1848
November1st to 15thDay
15%9%27%6%345%5%7%31%
1683
16th to endDay
13%10%46%6%45%6%6%7%28%
1560
December1st to 15thDay
12%10%47%6%345%5%6%32%
1560
16th to endDay
15%14%47%8%3446%6%24%
1664
January1st to 15thNight
12%12%47%6%36%5%5%6%28%
2716
16th to endNight
12%10%47%5%3446%7%33%
2844
February1st to 15thNight
12%10%47%6%35%5%6%8%29%
2432
16th to endNight
10%11%46%6%45%5%5%6%31%
1939
March1st to 15thNight
13%11%5%7%5%35%45%8%27%
2105
16th to endNight
9%11%5%8%6%36%6%7%7%26%
2030
April1st to 15thNight
14%13%46%6%24447%31%
1799
16th to endNight
10%9%244345%6%6%40%
1762
May1st to 15thNight
7%5%24425%5%5%7%49%
1439
16th to endNight
11%8%35%5%35%45%7%38%
1496
June1st to 15thNight
11%5%2432345%6%49%
1440
16th to endNight
6%412214345%62%
1440
July1st to 15thNight
111214346%73%
1440
16th to endNight
1121232478%
1512
August1st to 15thNight
113212347%72%
1553
16th to endNight
11111123479%
1872
September1st to 15thNight
11221133478%
1800
16th to endNight
6%413423346%59%
1947
October1st to 15thNight
9%5%25%423335%52%
2160
16th to endNight
13%7%25%6%2445%5%42%
2376
November1st to 15thNight
16%10%35%7%35%6%5%5%29%
2504
16th to endNight
14%10%37%5%35%45%7%33%
2730
December1st to 15thNight
11%11%47%6%35%45%7%33%
2730
16th to endNight
14%14%47%7%4445%7%24%
2912

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
16%9%37%6%36%5%5%7%27%
1552
16th to endDay
14%12%46%43445%6%31%
1730
February1st to 15thDay
12%13%37%7%235%6%8%28%
1685
16th to endDay
11%14%47%6%35%5%6%8%26%
1535
March1st to 15thDay
14%15%5%8%6%35%5%5%6%22%
1854
16th to endDay
14%14%48%6%35%45%6%24%
2189
April1st to 15thDay
12%14%5%8%7%34446%27%
2149
16th to endDay
9%11%36%5%15%45%7%39%
2196
May1st to 15thDay
10%7%35%42435%6%45%
2511
16th to endDay
14%9%35%5%35%45%6%36%
2615
June1st to 15thDay
13%6%345%2445%7%43%
2520
16th to endDay
8%413323346%58%
2520
July1st to 15thDay
222213335%73%
2520
16th to endDay
21221223476%
2657
August1st to 15thDay
112313346%71%
2406
16th to endDay
21221222476%
2330
September1st to 15thDay
1112111236%75%
2160
16th to endDay
7%5%2442445%5%53%
2011
October1st to 15thDay
12%7%25%425%447%43%
1800
16th to endDay
15%7%26%5%2345%5%42%
1848
November1st to 15thDay
17%10%36%6%35%45%7%29%
1683
16th to endDay
16%11%37%5%35%6%5%9%27%
1560
December1st to 15thDay
14%10%47%5%245%5%6%31%
1560
16th to endDay
18%14%47%7%345%5%7%23%
1664
January1st to 15thNight
15%12%46%5%35%5%47%27%
2716
16th to endNight
14%11%35%6%245%5%7%33%
2844
February1st to 15thNight
13%11%47%5%36%46%7%28%
2432
16th to endNight
11%14%47%5%35%5%46%31%
1939
March1st to 15thNight
13%13%6%8%5%2446%7%26%
2105
16th to endNight
11%12%47%6%46%5%6%7%25%
2034
April1st to 15thNight
14%14%36%5%35%45%6%29%
1799
16th to endNight
10%10%35%42445%8%40%
1762
May1st to 15thNight
7%5%23435%45%7%49%
1439
16th to endNight
12%6%46%6%34448%38%
1496
June1st to 15thNight
12%5%23423447%49%
1440
16th to endNight
7%313323445%62%
1440
July1st to 15thNight
11213446%73%
1440
16th to endNight
11111223379%
1512
August1st to 15thNight
112312336%73%
1553
16th to endNight
11211223479%
1872
September1st to 15thNight
21121223478%
1800
16th to endNight
6%5%23333336%58%
1947
October1st to 15thNight
11%6%24423345%52%
2160
16th to endNight
14%7%26%5%24346%42%
2376
November1st to 15thNight
17%11%36%6%35%5%5%5%28%
2504
16th to endNight
17%10%36%435%45%6%32%
2730
December1st to 15thNight
13%11%47%5%2445%7%32%
2730
16th to endNight
17%14%46%7%345%5%6%24%
2912

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
54%6%16%16%5%1
1552
16th to endDay
52%5%13%17%7%3
1730
February1st to 15thDay
52%7%16%16%5%
1685
16th to endDay
53%6%15%17%4
1535
March1st to 15thDay
59%5%12%14%5%1
1854
16th to endDay
57%5%14%17%4
2189
April1st to 15thDay
56%5%11%18%6%
2149
16th to endDay
43%5%14%24%10%1
2196
May1st to 15thDay
38%412%27%16%1
2511
16th to endDay
48%411%22%10%1
2619
June1st to 15thDay
40%410%25%15%3
2520
16th to endDay
27%29%30%23%5%
2520
July1st to 15thDay
15%27%21%29%22%
2371
16th to endDay
13%1413%35%31%
2490
August1st to 15thDay
15%25%25%31%19%
2389
16th to endDay
13%2423%38%16%
2330
September1st to 15thDay
12%1426%34%20%
2160
16th to endDay
31%48%24%23%7%
2011
October1st to 15thDay
41%411%20%15%5%
1800
16th to endDay
43%313%21%15%1
1848
November1st to 15thDay
52%414%20%7%
1683
16th to endDay
52%6%16%14%9%
1560
December1st to 15thDay
52%5%15%19%6%
1560
16th to endDay
60%5%12%16%3
1664
January1st to 15thNight
55%5%15%14%8%
2716
16th to endNight
49%413%19%9%3
2844
February1st to 15thNight
52%6%18%14%7%
2444
16th to endNight
53%5%12%21%6%
1939
March1st to 15thNight
55%6%14%15%6%1
2105
16th to endNight
53%6%17%18%3
2034
April1st to 15thNight
53%5%15%17%8%
1799
16th to endNight
42%6%16%23%9%1
1762
May1st to 15thNight
34%416%29%14%1
1440
16th to endNight
45%5%14%24%8%1
1496
June1st to 15thNight
35%6%14%27%13%2
1440
16th to endNight
24%313%35%18%5%
1440
July1st to 15thNight
11%311%26%30%16%
1360
16th to endNight
11%2417%35%28%
1416
August1st to 15thNight
13%26%28%33%15%
1545
16th to endNight
9%18%26%37%15%
1872
September1st to 15thNight
11%25%27%37%16%
1800
16th to endNight
28%39%23%22%12%
1947
October1st to 15thNight
33%312%24%20%4
2160
16th to endNight
42%412%20%17%2
2376
November1st to 15thNight
53%5%11%18%9%
2504
16th to endNight
50%415%17%11%
2730
December1st to 15thNight
51%5%15%19%7%
2730
16th to endNight
59%413%15%5%
2912

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%314%25%28%2
90
16th to endDay
25%8%22%27%14%1
162
February1st to 15thDay
21%11%26%27%11%1
273
16th to endDay
20%20%25%21%11%
231
March1st to 15thDay
28%20%25%20%5%
270
16th to endDay
26%18%26%18%10%
288
April1st to 15thDay
20%18%24%21%8%6%
269
16th to endDay
15%22%30%18%8%4
270
May1st to 15thDay
19%17%26%20%15%1
288
16th to endDay
19%11%19%23%17%9%
330
June1st to 15thDay
14%13%27%20%15%8%
315
16th to endDay
10%9%24%28%19%7%
315
July1st to 15thDay
37%26%31%20%10%
305
16th to endDay
27%34%29%14%10%
327
August1st to 15thDay
26%26%30%19%14%
315
16th to endDay
37%23%24%25%15%
332
September1st to 15thDay
38%21%29%27%9%
315
16th to endDay
10%9%22%27%26%3
315
October1st to 15thDay
16%10%23%28%18%2
315
16th to endDay
20%9%20%22%23%4
264
November1st to 15thDay
14%11%25%39%6%1
127
16th to endDay
25%15%21%26%10%1
90
December1st to 15thDay
25%7%26%20%12%7%
90
16th to endDay
23%316%38%15%2
96
January1st to 15thNight
20%7%16%30%23%1
780
16th to endNight
17%7%13%34%22%3
832
February1st to 15thNight
16%7%15%39%19%1
752
16th to endNight
17%9%17%36%18%1
632
March1st to 15thNight
18%10%19%32%16%2
720
16th to endNight
15%11%21%32%17%1
768
April1st to 15thNight
19%10%17%31%19%2
719
16th to endNight
17%7%16%31%23%3
682
May1st to 15thNight
9%5%15%43%23%1
360
16th to endNight
15%410%37%28%2
375
June1st to 15thNight
14%314%43%22%2
360
16th to endNight
8%315%44%26%1
360
July1st to 15thNight
25%47%40%2
340
16th to endNight
211%49%34%1
376
August1st to 15thNight
11241%44%7%
471
16th to endNight
2110%37%40%7%
726
September1st to 15thNight
228%38%38%10%
720
16th to endNight
9%410%34%34%6%
716
October1st to 15thNight
13%312%38%26%5%
720
16th to endNight
16%411%36%25%5%
768
November1st to 15thNight
20%5%15%40%15%1
760
16th to endNight
21%10%13%30%20%4
780
December1st to 15thNight
20%6%12%34%24%2
780
16th to endNight
24%9%16%34%14%1
832
Page generated at 2018-02-13 17:46:06. Version ac04

Copyright 2018 A. Danko


Prineville Clear Sky Chart |Charts Home