Netarts Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Netarts Observatory clear sky chart from 2005-11-06 to 2024-01-15.

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%
22613
6%
74244
6%
22564
38%
22564
7%
63163

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
20%
760
1%
2646
1%
756
20%
756
2%
2474
January11th to 20thNight
26%
736
6%
2559
4%
736
29%
736
5%
2254
January21st to endNight
31%
792
8%
2574
8%
792
33%
792
7%
2196
February1st to 10thNight
26%
720
4%
2340
3%
720
27%
720
5%
2076
February11th to 20thNight
29%
700
5%
2274
3%
700
31%
700
6%
1949
February21st to endNight
25%
592
6%
1902
4%
592
28%
592
4%
1720
March1st to 10thNight
27%
720
4%
2010
3%
720
27%
720
6%
1808
March11th to 20thNight
26%
720
6%
1980
3%
720
28%
720
5%
1793
March21st to endNight
24%
792
2%
2178
1%
792
25%
792
3%
2038
April1st to 10thNight
27%
720
3%
1800
2%
720
27%
720
7%
1618
April11th to 20thNight
31%
650
7%
1718
4%
650
32%
650
7%
1508
April21st to endNight
34%
540
4%
1620
3%
540
34%
540
6%
1421
May1st to 10thNight
37%
461
5%
1541
6%
461
38%
461
6%
1326
May11th to 20thNight
40%
354
7%
1416
8%
354
44%
354
7%
1165
May21st to endNight
38%
389
3%
1552
5%
388
39%
388
4%
1366
June1st to 10thNight
41%
360
3%
1440
6%
360
42%
360
5%
1236
June11th to 20thNight
41%
360
3%
1279
3%
360
41%
360
5%
1134
June21st to endNight
53%
360
9%
1260
12%
360
55%
360
12%
972
July1st to 10thNight
58%
350
8%
1225
11%
350
59%
350
11%
950
July11th to 20thNight
57%
348
11%
1371
14%
348
61%
348
11%
1020
July21st to endNight
62%
443
11%
1535
15%
419
64%
419
13%
1107
August1st to 10thNight
58%
537
8%
1602
8%
534
58%
534
12%
1238
August11th to 20thNight
64%
534
17%
1602
14%
534
65%
534
17%
1150
August21st to endNight
55%
670
12%
1858
8%
670
57%
670
14%
1462
September1st to 10thNight
63%
720
16%
1800
10%
720
64%
720
21%
1345
September11th to 20thNight
53%
720
14%
1862
9%
720
55%
720
16%
1479
September21st to endNight
53%
720
14%
2024
13%
720
54%
720
14%
1608
October1st to 10thNight
45%
720
9%
2160
8%
720
47%
720
11%
1755
October11th to 20thNight
46%
720
9%
2160
10%
720
48%
720
12%
1745
October21st to endNight
36%
792
8%
2376
6%
792
39%
792
9%
1981
November1st to 10thNight
29%
740
4%
2549
4%
740
30%
740
5%
2286
November11th to 20thNight
27%
760
4%
2660
3%
760
28%
760
4%
2373
November21st to endNight
33%
760
3%
2660
3%
760
34%
760
6%
2303
December1st to 10thNight
32%
760
5%
2660
4%
760
33%
760
6%
2283
December11th to 20thNight
25%
759
5%
3216
3%
759
27%
759
4%
2767
December21st to endNight
17%
834
1%
4835
2%
817
18%
817
1%
4257

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
26%10%36%5%34446%29%
75268
Night
29%11%46%5%34345%27%
74509
TransparencyDay
39%38%7%10%5%1
74968
Night
41%38%6%8%5%2
74331
SeeingDay
29%11%24%23%11%3
14113
Night
34%7%14%24%18%3
22620

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
46%12%37%43332213%
1519
11th to 20thDay
39%9%35%43334423%
1486
21st to endDay
34%11%35%5%34335%25%
1782
February1st to 10thDay
40%12%45%5%23345%18%
1620
11th to 20thDay
36%14%47%5%3323418%
1575
21st to endDay
34%15%46%5%3434417%
1354
March1st to 10thDay
35%13%47%6%34435%15%
1948
11th to 20thDay
37%12%37%5%33346%17%
1980
21st to endDay
37%14%47%6%34436%12%
2178
April1st to 10thDay
34%13%5%8%6%335%5%6%13%
2160
11th to 20thDay
31%12%47%6%34435%20%
2188
21st to endDay
30%11%36%6%35%45%6%21%
2340
May1st to 10thDay
23%11%38%5%33446%29%
2416
11th to 20thDay
25%10%47%5%35%5%5%8%23%
2477
21st to endDay
28%10%47%6%45%5%5%6%20%
2723
June1st to 10thDay
28%9%46%5%35%446%26%
2520
11th to 20thDay
26%10%47%6%35%5%5%7%21%
2674
21st to endDay
17%8%46%5%24447%39%
2700
July1st to 10thDay
12%7%36%5%2445%8%45%
2700
11th to 20thDay
14%6%35%423347%49%
2538
21st to endDay
7%6%35%42446%8%51%
2689
August1st to 10thDay
11%8%45%42345%8%45%
2328
11th to 20thDay
11%5%244245%5%8%51%
2298
21st to endDay
13%7%45%42445%9%42%
2498
September1st to 10thDay
11%6%24423447%52%
2160
11th to 20thDay
15%8%36%5%45%45%7%38%
2093
21st to endDay
22%7%25%6%23345%41%
1936
October1st to 10thDay
25%9%36%5%33345%36%
1800
11th to 20thDay
27%8%36%5%33346%31%
1800
21st to endDay
33%8%35%423445%29%
1980
November1st to 10thDay
36%12%47%5%345%4417%
1526
11th to 20thDay
39%9%36%5%33445%19%
1520
21st to endDay
34%11%38%5%3433323%
1520
December1st to 10thDay
31%10%5%6%5%33435%26%
1520
11th to 20thDay
38%11%36%5%34435%19%
1928
21st to endDay
40%16%47%5%2333314%
2794
January1st to 10thNight
43%11%36%6%3433415%
2646
11th to 20thNight
39%12%36%423335%19%
2559
21st to endNight
33%11%45%443335%24%
2574
February1st to 10thNight
36%14%46%6%34435%16%
2340
11th to 20thNight
32%14%37%43423422%
2272
21st to endNight
34%14%37%5%3333420%
1902
March1st to 10thNight
35%14%46%42433420%
2010
11th to 20thNight
36%12%46%5%2335%419%
1980
21st to endNight
38%16%46%5%2343415%
2178
April1st to 10thNight
34%15%47%5%34445%17%
1800
11th to 20thNight
29%13%5%6%5%34446%22%
1718
21st to endNight
30%12%36%6%3445%6%22%
1620
May1st to 10thNight
24%13%46%6%34445%29%
1541
11th to 20thNight
26%13%46%5%2445%7%24%
1416
21st to endNight
29%11%46%436%45%8%20%
1552
June1st to 10thNight
25%10%38%7%35%345%28%
1440
11th to 20thNight
24%12%47%6%446%5%6%23%
1279
21st to endNight
16%10%36%434347%40%
1260
July1st to 10thNight
10%11%45%5%445%5%7%41%
1260
11th to 20thNight
10%8%35%5%2445%7%46%
1417
21st to endNight
7%8%45%432347%52%
1625
August1st to 10thNight
10%11%35%5%2345%7%44%
1611
11th to 20thNight
12%8%24223347%53%
1602
21st to endNight
14%10%35%43445%6%43%
1858
September1st to 10thNight
14%6%3422335%6%54%
1800
11th to 20thNight
16%8%37%5%24345%41%
1862
21st to endNight
19%7%25%423336%44%
2024
October1st to 10thNight
24%6%36%434346%37%
2160
11th to 20thNight
24%8%36%423447%35%
2160
21st to endNight
29%9%35%5%33335%32%
2376
November1st to 10thNight
37%9%36%6%34445%19%
2549
11th to 20thNight
39%10%36%5%3433420%
2660
21st to endNight
31%10%47%5%3444426%
2660
December1st to 10thNight
30%11%36%5%34445%25%
2660
11th to 20thNight
36%10%46%5%34446%18%
3276
21st to endNight
38%15%5%7%5%3433314%
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
55%39%322
1519
11th to 20thDay
41%40%6%45%4
1486
21st to endDay
43%38%37%8%2
1782
February1st to 10thDay
46%36%7%6%4
1620
11th to 20thDay
46%38%47%42
1584
21st to endDay
49%37%46%31
1354
March1st to 10thDay
49%37%7%5%1
1948
11th to 20thDay
49%37%6%6%2
1980
21st to endDay
52%38%5%41
2178
April1st to 10thDay
48%38%6%7%2
2160
11th to 20thDay
45%37%6%7%42
2191
21st to endDay
43%39%8%6%41
2340
May1st to 10thDay
41%38%7%10%3
2416
11th to 20thDay
36%40%10%8%41
2480
21st to endDay
45%39%8%8%
2724
June1st to 10thDay
45%38%7%7%3
2520
11th to 20thDay
45%40%9%6%1
2674
21st to endDay
31%38%12%12%5%2
2700
July1st to 10thDay
25%39%9%14%11%2
2626
11th to 20thDay
26%37%6%18%11%2
2462
21st to endDay
22%38%7%19%12%1
2539
August1st to 10thDay
28%38%10%17%6%
2312
11th to 20thDay
24%36%9%18%10%3
2298
21st to endDay
27%38%8%18%8%1
2498
September1st to 10thDay
20%37%8%17%11%7%
2160
11th to 20thDay
30%38%8%15%6%3
2093
21st to endDay
32%38%8%12%8%3
1936
October1st to 10thDay
35%37%5%13%8%2
1800
11th to 20thDay
35%38%9%9%7%1
1800
21st to endDay
38%38%5%10%9%1
1980
November1st to 10thDay
46%42%45%3
1526
11th to 20thDay
41%42%6%6%32
1520
21st to endDay
43%40%37%5%1
1520
December1st to 10thDay
39%40%6%6%8%1
1520
11th to 20thDay
49%32%8%6%4
1928
21st to endDay
60%27%6%5%1
2794
January1st to 10thNight
51%40%341
2646
11th to 20thNight
42%41%5%5%34
2559
21st to endNight
41%37%5%6%8%3
2574
February1st to 10thNight
47%37%5%7%32
2340
11th to 20thNight
42%38%6%7%5%2
2274
21st to endNight
50%36%5%441
1902
March1st to 10thNight
47%37%7%8%2
2010
11th to 20thNight
48%37%6%5%3
1980
21st to endNight
52%38%5%41
2178
April1st to 10thNight
47%36%8%6%3
1800
11th to 20thNight
43%37%6%8%33
1718
21st to endNight
44%38%6%8%32
1620
May1st to 10thNight
43%38%6%8%5%1
1541
11th to 20thNight
39%38%9%8%5%2
1416
21st to endNight
46%38%7%7%2
1552
June1st to 10thNight
43%38%7%10%2
1440
11th to 20thNight
45%39%10%6%
1279
21st to endNight
30%38%9%16%5%2
1260
July1st to 10thNight
27%41%9%10%10%3
1225
11th to 20thNight
27%39%6%15%11%2
1371
21st to endNight
24%38%8%15%10%4
1535
August1st to 10thNight
29%39%10%14%7%1
1602
11th to 20thNight
23%36%8%18%10%5%
1602
21st to endNight
30%37%7%15%9%2
1858
September1st to 10thNight
21%37%6%17%11%7%
1800
11th to 20thNight
30%36%8%14%7%5%
1862
21st to endNight
30%38%6%9%11%5%
2024
October1st to 10thNight
34%38%6%11%8%3
2160
11th to 20thNight
32%39%7%10%10%2
2160
21st to endNight
37%38%5%7%10%2
2376
November1st to 10thNight
43%42%47%31
2549
11th to 20thNight
45%40%5%5%32
2660
21st to endNight
41%41%5%6%6%2
2660
December1st to 10thNight
39%41%6%7%6%1
2660
11th to 20thNight
45%35%7%6%6%
3276
21st to endNight
58%28%6%6%2
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
47%17%18%12%6%1
180
11th to 20thDay
46%8%15%16%12%3
182
21st to endDay
40%10%17%19%11%2
374
February1st to 10thDay
51%9%15%16%9%1
340
11th to 20thDay
47%12%20%15%6%
335
21st to endDay
42%17%22%16%31
290
March1st to 10thDay
44%11%19%20%5%
420
11th to 20thDay
39%12%21%18%8%1
420
21st to endDay
44%15%21%14%6%1
462
April1st to 10thDay
39%16%20%17%6%1
420
11th to 20thDay
40%17%20%14%7%2
412
21st to endDay
35%18%24%15%7%
420
May1st to 10thDay
26%18%25%22%6%2
423
11th to 20thDay
35%11%25%20%7%2
448
21st to endDay
29%11%25%22%10%3
485
June1st to 10thDay
30%10%29%19%11%2
450
11th to 20thDay
25%16%32%21%6%1
604
21st to endDay
16%8%31%33%10%2
630
July1st to 10thDay
12%6%32%38%10%2
621
11th to 20thDay
11%8%31%34%12%3
461
21st to endDay
5%6%26%43%16%5%
487
August1st to 10thDay
13%5%22%39%17%6%
447
11th to 20thDay
7%423%38%20%7%
437
21st to endDay
13%8%30%32%13%3
495
September1st to 10thDay
15%8%28%30%15%5%
450
11th to 20thDay
19%7%23%32%15%5%
450
21st to endDay
23%9%22%27%17%2
450
October1st to 10thDay
26%12%20%21%18%3
450
11th to 20thDay
31%9%18%20%16%6%
450
21st to endDay
36%11%21%17%11%4
495
November1st to 10thDay
40%14%24%9%13%1
207
11th to 20thDay
41%10%20%16%10%3
180
21st to endDay
41%12%15%15%14%4
180
December1st to 10thDay
43%7%22%11%12%4
180
11th to 20thDay
48%12%16%14%9%1
180
21st to endDay
47%10%20%15%7%2
198
January1st to 10thNight
50%11%13%14%10%2
760
11th to 20thNight
45%10%14%15%14%3
736
21st to endNight
39%8%14%24%13%2
792
February1st to 10thNight
43%7%15%22%12%2
720
11th to 20thNight
39%9%16%21%13%1
704
21st to endNight
42%9%15%23%10%
592
March1st to 10thNight
43%8%15%19%12%2
720
11th to 20thNight
43%9%13%22%11%1
720
21st to endNight
47%8%14%18%12%2
792
April1st to 10thNight
43%7%13%22%12%2
720
11th to 20thNight
35%9%17%24%13%2
650
21st to endNight
35%9%13%27%14%2
540
May1st to 10thNight
29%8%17%25%19%3
461
11th to 20thNight
31%5%12%23%27%2
354
21st to endNight
30%7%16%22%20%4
389
June1st to 10thNight
27%317%28%24%1
360
11th to 20thNight
25%8%16%31%17%3
360
21st to endNight
16%417%33%27%2
360
July1st to 10thNight
14%414%31%33%4
350
11th to 20thNight
13%218%38%26%3
348
21st to endNight
8%312%35%35%6%
443
August1st to 10thNight
15%39%28%36%8%
537
11th to 20thNight
14%47%23%44%7%
534
21st to endNight
16%414%32%29%6%
670
September1st to 10thNight
13%5%13%33%31%5%
720
11th to 20thNight
18%413%23%30%12%
720
21st to endNight
22%314%29%27%5%
720
October1st to 10thNight
26%5%15%24%25%5%
720
11th to 20thNight
27%6%12%27%22%6%
720
21st to endNight
34%7%15%22%17%4
792
November1st to 10thNight
41%8%15%21%13%1
740
11th to 20thNight
43%10%13%22%10%1
760
21st to endNight
37%7%16%26%12%3
760
December1st to 10thNight
36%7%19%23%13%2
760
11th to 20thNight
48%9%14%20%9%1
760
21st to endNight
53%11%13%16%7%1
836
Page generated at 2024-01-11 19:33:49. Version ac07

Copyright 2024 Attilla Danko


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