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 2018-02-22.

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%
15242
15%
48938
10%
15218
44%
15218
19%
31953

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
23%
776
5%
2716
3%
776
27%
776
5%
2284
January16th to endNight
30%
832
6%
2883
5%
832
32%
832
9%
2289
February1st to 15thNight
32%
760
9%
2483
7%
760
35%
760
12%
1844
February16th to endNight
29%
660
13%
2043
9%
660
34%
660
14%
1469
March1st to 15thNight
28%
720
8%
2112
5%
720
32%
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
40%
359
21%
1439
18%
359
54%
359
24%
709
May16th to endNight
40%
374
12%
1496
13%
374
48%
374
21%
810
June1st to 15thNight
32%
360
13%
1440
9%
360
44%
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%
432
33%
1504
26%
430
75%
430
55%
587
August16th to endNight
56%
705
36%
1851
18%
705
66%
705
57%
882
September1st to 15thNight
60%
720
33%
1800
16%
720
65%
720
62%
867
September16th to endNight
55%
716
31%
1950
20%
716
62%
716
41%
1059
October1st to 15thNight
44%
720
18%
2160
14%
720
51%
720
26%
1317
October16th to endNight
42%
768
17%
2396
13%
768
48%
768
20%
1599
November1st to 15thNight
32%
760
11%
2542
7%
760
38%
760
13%
1882
November16th to endNight
32%
780
9%
2730
5%
780
38%
780
10%
2073
December1st to 15thNight
29%
780
8%
2730
7%
780
32%
780
9%
2153
December16th to endNight
27%
832
8%
2912
6%
832
31%
832
8%
2297

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%35%5%2445%6%45%
49333
Night
12%6%35%5%2445%6%43%
49106
Cloud CoverDay
9%6%35%5%3445%7%44%
49333
Night
11%7%35%5%3445%6%42%
49110
TransparencyDay
37%8%14%20%14%4
49004
Night
40%8%14%20%12%3
48939
SeeingDay
13%21%27%21%12%3
5948
Night
13%21%20%25%15%2
15252

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%13%6%10%9%45%5%4412%
1552
16th to endDay
18%12%6%9%7%45%6%5%6%16%
1690
February1st to 15thDay
16%10%49%7%35%6%45%25%
1711
16th to endDay
15%9%35%6%46%6%7%7%27%
1576
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%
2445
16th to endDay
211221233473%
2351
September1st to 15thDay
222212235%73%
2160
16th to endDay
6%414424346%56%
2010
October1st to 15thDay
12%5%36%43345%7%43%
1800
16th to endDay
16%6%345%35%5%6%6%35%
1827
November1st to 15thDay
17%10%48%6%45%5%6%7%23%
1644
16th to endDay
20%10%6%7%7%45%45%6%19%
1560
December1st to 15thDay
18%12%7%11%7%2343424%
1560
16th to endDay
25%12%5%7%5%34446%19%
1664
January1st to 15thNight
22%12%5%9%8%34445%19%
2716
16th to endNight
20%9%310%6%36%45%6%23%
2883
February1st to 15thNight
16%9%5%6%6%3445%6%31%
2471
16th to endNight
12%9%46%5%3445%7%33%
2043
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
11121222478%
1512
16th to endNight
22211224476%
1851
September1st to 15thNight
211211225%77%
1800
16th to endNight
5%312424446%61%
1950
October1st to 15thNight
9%6%15%43435%6%49%
2160
16th to endNight
13%6%25%5%345%5%6%40%
2396
November1st to 15thNight
19%7%36%6%35%5%6%7%29%
2542
16th to endNight
19%8%46%5%35%5%46%29%
2730
December1st to 15thNight
17%11%5%10%6%3444427%
2730
16th to endNight
23%12%47%5%24446%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
21%14%6%8%9%46%5%45%13%
1552
16th to endDay
17%12%49%7%36%5%6%7%18%
1690
February1st to 15thDay
15%12%48%7%35%6%46%24%
1711
16th to endDay
12%10%37%7%45%5%6%8%27%
1576
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%74%
2445
16th to endDay
2212312235%72%
2351
September1st to 15thDay
221211335%72%
2160
16th to endDay
6%414434446%55%
2010
October1st to 15thDay
11%6%26%5%3446%7%41%
1800
16th to endDay
15%8%25%5%26%5%5%5%36%
1827
November1st to 15thDay
15%10%5%8%6%35%5%6%7%24%
1644
16th to endDay
18%8%7%9%8%36%45%7%20%
1560
December1st to 15thDay
17%11%6%9%8%34435%24%
1560
16th to endDay
22%14%5%8%5%34445%21%
1664
January1st to 15thNight
20%11%410%8%36%5%45%19%
2716
16th to endNight
19%9%48%7%45%5%5%7%23%
2883
February1st to 15thNight
15%10%48%6%3445%6%30%
2471
16th to endNight
11%10%5%6%6%35%45%8%33%
2043
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%
1512
16th to endNight
22111223476%
1851
September1st to 15thNight
211211335%77%
1800
16th to endNight
431332435%5%61%
1950
October1st to 15thNight
9%5%25%43445%6%48%
2160
16th to endNight
12%7%35%5%35%5%5%7%40%
2396
November1st to 15thNight
17%9%36%6%35%5%6%7%29%
2542
16th to endNight
17%7%48%6%3446%6%28%
2730
December1st to 15thNight
15%11%48%8%45%435%27%
2730
16th to endNight
21%12%47%5%34446%25%
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
73%9%8%5%1
1552
16th to endDay
64%11%12%7%2
1690
February1st to 15thDay
57%12%16%10%2
1711
16th to endDay
50%13%16%13%5%
1576
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%39%27%34%13%
2428
16th to endDay
15%310%30%31%8%
2351
September1st to 15thDay
14%29%29%31%12%
2160
16th to endDay
28%7%15%26%16%4
2010
October1st to 15thDay
38%8%16%21%13%1
1800
16th to endDay
44%11%15%17%9%
1827
November1st to 15thDay
55%12%14%14%2
1644
16th to endDay
62%12%13%9%2
1560
December1st to 15thDay
63%9%11%11%4
1560
16th to endDay
66%8%13%8%2
1664
January1st to 15thNight
66%10%10%9%2
2716
16th to endNight
60%9%14%11%2
2883
February1st to 15thNight
52%10%20%14%2
2483
16th to endNight
47%10%15%20%4
2043
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
11%28%29%33%13%
1504
16th to endNight
12%310%28%33%11%
1851
September1st to 15thNight
10%39%30%29%15%
1800
16th to endNight
22%5%14%29%19%7%
1950
October1st to 15thNight
34%6%12%24%19%2
2160
16th to endNight
41%9%13%20%14%
2396
November1st to 15thNight
51%10%14%18%4
2542
16th to endNight
53%12%13%15%5%
2730
December1st to 15thNight
59%10%12%14%2
2730
16th to endNight
58%11%13%11%4
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
33%416%24%17%3
90
16th to endDay
36%10%24%18%9%
122
February1st to 15thDay
20%21%26%20%8%1
281
16th to endDay
17%27%27%18%7%2
249
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
415%26%23%20%10%
315
16th to endDay
314%25%27%23%6%
332
September1st to 15thDay
5%20%25%24%17%7%
315
16th to endDay
6%16%31%27%16%1
315
October1st to 15thDay
14%22%29%20%10%2
315
16th to endDay
21%13%23%25%11%4
243
November1st to 15thDay
23%15%26%30%4
118
16th to endDay
24%14%23%26%11%
90
December1st to 15thDay
28%8%28%15%12%5%
90
16th to endDay
27%7%22%29%13%
96
January1st to 15thNight
24%20%16%23%13%1
780
16th to endNight
21%21%15%25%14%2
832
February1st to 15thNight
17%22%18%25%14%1
764
16th to endNight
14%26%21%24%12%
660
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%34%23%6%
432
16th to endNight
314%22%26%26%6%
705
September1st to 15thNight
213%21%25%30%7%
720
16th to endNight
6%14%18%28%27%3
716
October1st to 15thNight
11%17%21%28%17%3
720
16th to endNight
15%13%22%26%19%3
768
November1st to 15thNight
18%20%19%31%9%
760
16th to endNight
19%22%17%24%13%1
780
December1st to 15thNight
21%20%18%25%12%2
780
16th to endNight
22%23%16%26%9%
832
Page generated at 2018-02-23 08:21:28. Version ac04

Copyright 2018 A. Danko


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