Goldendale Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Goldendale Observatory clear sky chart from 2005-11-05 to 2017-08-12.

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
37%
14471
15%
46493
10%
14447
44%
14447
19%
30240

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
26%
716
6%
2506
3%
716
30%
716
6%
2080
January16th to endNight
32%
768
7%
2661
5%
768
34%
768
9%
2099
February1st to 15thNight
33%
700
8%
2288
7%
700
36%
700
12%
1714
February16th to endNight
30%
632
13%
1954
9%
632
35%
632
15%
1395
March1st to 15thNight
27%
720
8%
2112
5%
720
31%
720
14%
1582
March16th to endNight
27%
768
11%
2031
4%
768
31%
768
16%
1483
April1st to 15thNight
31%
719
13%
1799
5%
719
35%
719
21%
1278
April16th to endNight
32%
625
16%
1705
7%
625
38%
625
23%
1078
May1st to 15thNight
39%
359
21%
1439
18%
359
53%
359
24%
709
May16th to endNight
40%
374
12%
1496
13%
374
48%
374
21%
810
June1st to 15thNight
33%
360
13%
1440
9%
360
45%
360
23%
763
June16th to endNight
35%
360
17%
1440
13%
360
53%
360
26%
673
July1st to 15thNight
54%
340
19%
1360
20%
340
67%
340
49%
499
July16th to endNight
52%
376
31%
1416
29%
354
76%
354
56%
476
August1st to 15thNight
62%
420
33%
1468
27%
418
76%
418
55%
567
August16th to endNight
53%
646
33%
1696
15%
646
64%
646
54%
820
September1st to 15thNight
59%
660
35%
1650
17%
660
64%
660
61%
797
September16th to endNight
55%
656
30%
1787
19%
656
62%
656
41%
962
October1st to 15thNight
43%
660
18%
1980
14%
660
49%
660
24%
1234
October16th to endNight
41%
704
15%
2196
11%
704
47%
704
18%
1495
November1st to 15thNight
34%
700
11%
2341
8%
700
40%
700
13%
1723
November16th to endNight
33%
720
9%
2520
5%
720
38%
720
10%
1913
December1st to 15thNight
29%
720
9%
2520
7%
720
32%
720
9%
1974
December16th to endNight
27%
768
7%
2688
5%
768
30%
768
8%
2116

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
10%6%25%42445%7%45%
47499
Night
12%6%35%42445%6%43%
46661
Cloud CoverDay
9%6%35%43445%7%44%
47499
Night
11%7%35%5%2445%6%43%
46665
TransparencyDay
37%8%14%20%14%4
47170
Night
40%8%14%20%12%3
46494
SeeingDay
12%23%27%22%11%2
5372
Night
13%22%20%25%15%2
14481

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
23%12%6%9%9%46%5%4413%
1432
16th to endDay
17%11%6%10%7%45%6%5%6%18%
1560
February1st to 15thDay
17%11%49%7%25%6%45%23%
1576
16th to endDay
15%8%35%6%46%6%7%7%28%
1519
March1st to 15thDay
18%7%47%7%46%6%7%7%22%
1845
16th to endDay
13%8%37%7%46%6%6%8%25%
2193
April1st to 15thDay
9%7%46%5%46%6%6%9%32%
2149
16th to endDay
7%5%25%5%35%5%7%9%42%
2253
May1st to 15thDay
6%424425%48%10%45%
2511
16th to endDay
10%4235%25%5%6%9%43%
2615
June1st to 15thDay
9%32442446%8%50%
2520
16th to endDay
431332435%8%58%
2520
July1st to 15thDay
111112235%77%
2520
16th to endDay
31111223379%
2657
August1st to 15thDay
111212235%75%
2396
16th to endDay
211221233472%
2154
September1st to 15thDay
222212225%74%
1980
16th to endDay
6%413324336%58%
1843
October1st to 15thDay
12%5%36%44345%7%42%
1650
16th to endDay
17%7%346%35%5%6%6%33%
1675
November1st to 15thDay
16%9%48%6%45%5%6%8%24%
1515
16th to endDay
20%10%6%7%7%45%45%6%20%
1440
December1st to 15thDay
19%13%7%9%6%2443425%
1440
16th to endDay
24%12%5%7%5%25%446%20%
1536
January1st to 15thNight
22%12%48%8%34445%21%
2506
16th to endNight
20%9%49%6%35%45%6%24%
2661
February1st to 15thNight
16%10%5%6%6%3435%5%31%
2276
16th to endNight
12%9%46%6%3445%7%34%
1954
March1st to 15thNight
16%8%46%6%36%5%5%8%28%
2112
16th to endNight
11%7%35%6%36%6%7%8%33%
2027
April1st to 15thNight
11%6%245%36%5%5%9%38%
1799
16th to endNight
8%31442446%9%49%
1705
May1st to 15thNight
5%31432445%6%56%
1439
16th to endNight
6%4243245%7%10%47%
1496
June1st to 15thNight
8%324325%45%7%52%
1440
16th to endNight
3313323436%62%
1440
July1st to 15thNight
112212225%77%
1440
16th to endNight
111223381%
1512
August1st to 15thNight
121222479%
1476
16th to endNight
221211224474%
1696
September1st to 15thNight
211112225%77%
1650
16th to endNight
5%31232445%6%61%
1787
October1st to 15thNight
10%6%25%5%3435%6%47%
1980
16th to endNight
14%6%26%5%345%5%7%38%
2196
November1st to 15thNight
19%6%36%6%345%6%7%30%
2341
16th to endNight
19%8%46%5%35%446%30%
2520
December1st to 15thNight
19%11%5%8%5%3444428%
2520
16th to endNight
22%12%47%5%24446%24%
2688

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
21%14%6%8%9%46%5%45%14%
1432
16th to endDay
16%11%5%9%7%37%5%6%7%19%
1560
February1st to 15thDay
16%12%48%7%35%6%46%23%
1576
16th to endDay
12%10%37%7%46%5%6%8%27%
1519
March1st to 15thDay
15%10%47%7%47%5%6%8%21%
1845
16th to endDay
11%9%38%7%45%6%6%9%24%
2193
April1st to 15thDay
8%8%46%6%47%6%6%9%32%
2149
16th to endDay
7%6%35%5%26%46%9%41%
2253
May1st to 15thDay
6%425%435%5%7%9%44%
2511
16th to endDay
9%424435%6%7%9%41%
2615
June1st to 15thDay
9%323325%5%5%8%50%
2520
16th to endDay
431432345%7%58%
2520
July1st to 15thDay
111112235%76%
2520
16th to endDay
21111123378%
2657
August1st to 15thDay
111212245%75%
2396
16th to endDay
2212312235%71%
2154
September1st to 15thDay
2211211325%73%
1980
16th to endDay
6%413324446%56%
1843
October1st to 15thDay
11%6%26%5%3446%7%40%
1650
16th to endDay
15%8%25%5%37%5%6%5%34%
1675
November1st to 15thDay
13%9%5%8%7%35%5%7%7%25%
1515
16th to endDay
17%8%6%9%8%36%45%6%20%
1440
December1st to 15thDay
18%12%6%9%7%33445%25%
1440
16th to endDay
20%14%5%8%5%345%45%21%
1536
January1st to 15thNight
20%10%49%7%36%5%45%20%
2506
16th to endNight
18%9%48%7%46%45%7%23%
2661
February1st to 15thNight
15%10%48%7%3445%6%29%
2276
16th to endNight
11%10%5%6%6%35%45%8%33%
1954
March1st to 15thNight
13%9%48%6%35%5%6%8%28%
2112
16th to endNight
10%7%46%5%5%6%6%7%9%32%
2031
April1st to 15thNight
9%6%35%5%36%46%10%37%
1799
16th to endNight
7%4244245%7%9%47%
1705
May1st to 15thNight
5%41342436%7%55%
1439
16th to endNight
6%5%233146%7%11%46%
1496
June1st to 15thNight
8%32342445%7%51%
1440
16th to endNight
3314413337%61%
1440
July1st to 15thNight
21211223477%
1440
16th to endNight
111223380%
1512
August1st to 15thNight
1122222378%
1476
16th to endNight
22111224474%
1696
September1st to 15thNight
211211335%76%
1650
16th to endNight
5%31232435%6%61%
1787
October1st to 15thNight
10%6%25%43445%6%46%
1980
16th to endNight
12%7%35%5%35%5%5%7%38%
2196
November1st to 15thNight
17%8%36%6%35%5%6%7%30%
2341
16th to endNight
18%7%49%6%3445%6%29%
2520
December1st to 15thNight
17%12%5%7%7%35%445%27%
2520
16th to endNight
21%12%46%5%34446%25%
2688

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
72%9%9%6%1
1432
16th to endDay
63%10%13%8%3
1560
February1st to 15thDay
59%12%15%10%1
1576
16th to endDay
50%13%16%13%5%
1519
March1st to 15thDay
57%10%13%13%4
1845
16th to endDay
52%10%17%16%3
2193
April1st to 15thDay
44%10%18%19%6%
2149
16th to endDay
35%9%20%21%10%1
2253
May1st to 15thDay
30%8%16%27%15%1
2511
16th to endDay
34%8%20%25%9%
2619
June1st to 15thDay
30%7%16%28%15%2
2520
16th to endDay
23%5%15%32%18%5%
2520
July1st to 15thDay
10%49%26%34%15%
2371
16th to endDay
11%27%18%36%22%
2490
August1st to 15thDay
11%38%27%34%14%
2379
16th to endDay
15%311%28%31%8%
2154
September1st to 15thDay
14%29%30%30%11%
1980
16th to endDay
27%7%15%26%17%5%
1843
October1st to 15thDay
40%9%15%20%13%1
1650
16th to endDay
46%11%16%16%9%
1675
November1st to 15thDay
53%13%15%15%2
1515
16th to endDay
62%11%12%9%2
1440
December1st to 15thDay
61%9%11%11%5%
1440
16th to endDay
65%8%14%8%2
1536
January1st to 15thNight
64%10%10%10%2
2506
16th to endNight
60%9%14%12%3
2661
February1st to 15thNight
53%9%20%14%2
2288
16th to endNight
47%10%16%21%4
1954
March1st to 15thNight
51%10%17%15%5%
2112
16th to endNight
44%11%19%19%5%
2031
April1st to 15thNight
41%9%17%22%8%
1799
16th to endNight
31%10%19%26%10%1
1705
May1st to 15thNight
26%5%16%32%17%1
1440
16th to endNight
28%10%25%25%8%1
1496
June1st to 15thNight
29%7%16%30%14%1
1440
16th to endNight
22%6%13%33%20%4
1440
July1st to 15thNight
12%313%23%31%15%
1360
16th to endNight
8%37%20%36%24%
1416
August1st to 15thNight
10%28%29%34%14%
1468
16th to endNight
13%311%28%32%11%
1696
September1st to 15thNight
10%310%31%28%15%
1650
16th to endNight
21%5%14%29%19%8%
1787
October1st to 15thNight
36%6%12%22%18%2
1980
16th to endNight
42%10%14%19%12%
2196
November1st to 15thNight
50%11%13%19%4
2341
16th to endNight
53%12%13%16%4
2520
December1st to 15thNight
58%10%12%14%3
2520
16th to endNight
58%11%14%11%4
2688

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
30%313%26%23%3
60
16th to endDay
34%10%22%19%12%1
88
February1st to 15thDay
21%20%25%22%9%
236
16th to endDay
15%28%28%17%7%2
228
March1st to 15thDay
24%28%28%16%2
270
16th to endDay
22%35%24%12%5%
288
April1st to 15thDay
13%29%31%14%7%2
269
16th to endDay
16%36%24%12%5%3
270
May1st to 15thDay
13%27%26%20%9%1
288
16th to endDay
11%22%23%26%11%3
330
June1st to 15thDay
7%31%26%20%10%3
315
16th to endDay
9%24%30%24%8%2
315
July1st to 15thDay
315%36%24%17%1
305
16th to endDay
218%36%22%15%4
327
August1st to 15thDay
416%25%23%20%10%
300
16th to endDay
418%27%26%18%4
268
September1st to 15thDay
5%24%27%24%14%3
255
16th to endDay
6%17%30%30%14%1
255
October1st to 15thDay
16%22%29%21%8%2
255
16th to endDay
22%14%24%26%9%3
187
November1st to 15thDay
8%15%27%41%6%
79
16th to endDay
25%13%16%30%15%
60
December1st to 15thDay
41%10%33%15%
60
16th to endDay
14%9%20%35%20%
64
January1st to 15thNight
23%22%16%24%12%1
720
16th to endNight
20%22%14%23%15%3
768
February1st to 15thNight
17%22%16%26%15%1
704
16th to endNight
13%26%21%24%12%
632
March1st to 15thNight
16%24%24%22%11%
720
16th to endNight
13%30%22%21%10%1
768
April1st to 15thNight
10%29%23%22%11%2
719
16th to endNight
10%32%23%19%12%3
625
May1st to 15thNight
7%28%20%26%14%2
360
16th to endNight
6%23%23%27%14%3
375
June1st to 15thNight
7%26%30%22%12%1
360
16th to endNight
5%31%21%26%13%
360
July1st to 15thNight
316%24%35%20%1
340
16th to endNight
121%23%32%18%2
376
August1st to 15thNight
113%20%33%24%6%
420
16th to endNight
415%23%26%24%5%
646
September1st to 15thNight
214%21%26%28%6%
660
16th to endNight
7%15%17%28%27%3
656
October1st to 15thNight
12%17%21%28%16%3
660
16th to endNight
15%14%22%25%18%3
704
November1st to 15thNight
17%21%18%32%9%
700
16th to endNight
19%23%16%24%13%1
720
December1st to 15thNight
22%22%18%25%10%
720
16th to endNight
21%25%16%25%10%
768
Page generated at 2017-08-13 11:16:16. Version ac04

Copyright 2017 A. Danko


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