Cahas Mountain Overlook
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cahas Mountain Overlook clear sky chart from 2005-11-05 to 2018-10-27.

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
42%
17282
22%
51372
12%
17244
52%
17244
25%
32303

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%
778
24%
2522
8%
776
42%
776
18%
1518
January16th to endNight
21%
832
25%
2704
9%
832
41%
832
20%
1637
February1st to 15thNight
19%
761
22%
2482
7%
761
37%
761
18%
1520
February16th to endNight
19%
683
24%
2025
7%
683
37%
683
20%
1267
March1st to 15thNight
27%
780
24%
2145
10%
780
40%
780
23%
1365
March16th to endNight
27%
832
19%
2288
9%
832
36%
832
22%
1520
April1st to 15thNight
29%
778
20%
2031
6%
778
39%
778
26%
1322
April16th to endNight
39%
694
22%
1850
9%
694
47%
694
28%
1202
May1st to 15thNight
43%
585
17%
1755
9%
585
49%
585
24%
1159
May16th to endNight
55%
609
14%
1828
9%
609
58%
609
26%
1201
June1st to 15thNight
67%
585
17%
1755
15%
585
68%
585
32%
1106
June16th to endNight
68%
585
18%
1755
15%
585
70%
585
34%
1055
July1st to 15thNight
69%
555
14%
1665
12%
555
71%
555
29%
1061
July16th to endNight
72%
612
16%
1739
13%
579
74%
579
31%
1078
August1st to 15thNight
65%
575
19%
1715
15%
572
66%
572
29%
1100
August16th to endNight
68%
733
18%
1975
14%
733
69%
733
32%
1279
September1st to 15thNight
61%
780
23%
2041
17%
780
63%
780
31%
1354
September16th to endNight
50%
777
20%
2145
17%
777
52%
777
24%
1480
October1st to 15thNight
50%
780
25%
2328
21%
780
58%
780
27%
1458
October16th to endNight
40%
816
32%
2447
20%
816
56%
816
33%
1372
November1st to 15thNight
43%
760
26%
2316
17%
760
55%
760
27%
1391
November16th to endNight
37%
780
29%
2535
17%
780
52%
780
26%
1419
December1st to 15thNight
28%
780
22%
2622
9%
780
44%
780
17%
1645
December16th to endNight
23%
832
22%
2704
8%
832
39%
832
15%
1794

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
14%5%25%5%35%5%5%7%39%
52139
Night
13%5%2442445%7%44%
51565
Cloud CoverDay
14%5%25%5%35%5%5%7%38%
52149
Night
13%5%2442445%7%44%
51569
TransparencyDay
43%5%11%21%14%3
51850
Night
38%5%11%23%17%3
51372
SeeingDay
20%11%20%22%16%8%
7098
Night
18%11%21%27%18%3
17289

By Month

Percentage Cloud Cover NE (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
14%6%25%43445%7%43%
1746
16th to endDay
12%6%25%434445%44%
1872
February1st to 15thDay
12%7%26%5%35%436%41%
1710
16th to endDay
14%6%35%435%348%39%
1731
March1st to 15thDay
14%5%2442445%6%45%
2134
16th to endDay
17%7%35%425%345%39%
2288
April1st to 15thDay
11%5%1442445%7%47%
2246
16th to endDay
17%5%25%6%25%35%6%39%
2396
May1st to 15thDay
17%6%25%5%35%5%6%7%34%
2526
16th to endDay
16%5%25%6%35%5%7%8%33%
2639
June1st to 15thDay
11%3245%47%6%7%9%35%
2535
16th to endDay
9%426%5%46%7%7%9%37%
2535
July1st to 15thDay
11%5%36%7%47%7%6%9%30%
2535
16th to endDay
10%5%37%6%47%6%8%9%29%
2673
August1st to 15thDay
15%5%25%7%46%6%8%9%28%
2487
16th to endDay
13%6%26%6%46%6%6%9%31%
2564
September1st to 15thDay
16%6%245%2445%7%39%
2246
16th to endDay
24%7%25%42445%5%32%
2145
October1st to 15thDay
19%5%13323245%47%
1960
16th to endDay
12%5%24323235%51%
2034
November1st to 15thDay
14%324424446%49%
1871
16th to endDay
15%424423336%48%
1755
December1st to 15thDay
12%5%245%35%45%6%43%
1639
16th to endDay
18%7%35%424447%38%
1872
January1st to 15thNight
14%424423436%48%
2522
16th to endNight
14%6%245%2435%6%44%
2704
February1st to 15thNight
14%7%243235%46%45%
2480
16th to endNight
12%5%24425%45%7%44%
2025
March1st to 15thNight
14%5%2342445%7%46%
2133
16th to endNight
16%4145%245%47%42%
2288
April1st to 15thNight
12%6%2442345%6%45%
2031
16th to endNight
16%4244245%47%45%
1850
May1st to 15thNight
14%6%35%43445%7%40%
1755
16th to endNight
14%5%245%345%6%9%39%
1826
June1st to 15thNight
9%3145%35%5%7%11%43%
1755
16th to endNight
7%32442446%12%47%
1755
July1st to 15thNight
9%324435%6%7%9%44%
1755
16th to endNight
5%3245%36%7%8%12%39%
1847
August1st to 15thNight
13%5%245%2446%10%40%
1726
16th to endNight
9%325%5%35%5%7%9%42%
1975
September1st to 15thNight
14%425%42435%6%44%
2041
16th to endNight
20%5%25%43335%6%38%
2145
October1st to 15thNight
17%414424246%46%
2328
16th to endNight
12%413313345%55%
2447
November1st to 15thNight
15%5%2332433451%
2316
16th to endNight
14%413213346%52%
2535
December1st to 15thNight
15%6%25%42445%5%42%
2622
16th to endNight
16%8%36%434448%36%
2704

Percentage Cloud Cover SE (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
14%5%2442445%7%43%
1746
16th to endDay
13%6%25%5%24445%44%
1872
February1st to 15thDay
13%7%35%5%35%436%41%
1710
16th to endDay
15%6%35%44435%7%39%
1731
March1st to 15thDay
14%4245%2445%6%46%
2145
16th to endDay
18%7%35%425%446%38%
2287
April1st to 15thDay
11%414435%45%7%47%
2246
16th to endDay
17%5%25%6%2445%5%39%
2396
May1st to 15thDay
17%6%25%5%35%5%5%7%34%
2526
16th to endDay
16%425%6%36%6%6%8%33%
2639
June1st to 15thDay
11%325%5%47%6%7%9%35%
2535
16th to endDay
9%435%5%46%7%6%9%36%
2535
July1st to 15thDay
11%5%36%7%47%6%6%9%30%
2535
16th to endDay
10%5%37%6%5%7%6%8%9%29%
2673
August1st to 15thDay
15%5%25%7%46%6%8%9%29%
2487
16th to endDay
13%5%26%6%46%6%7%8%31%
2564
September1st to 15thDay
16%6%245%245%5%7%38%
2246
16th to endDay
24%6%25%42445%5%32%
2145
October1st to 15thDay
19%5%13323335%47%
1960
16th to endDay
12%5%24324335%51%
2034
November1st to 15thDay
14%323424446%49%
1871
16th to endDay
15%414423336%48%
1755
December1st to 15thDay
12%5%15%5%35%35%7%43%
1639
16th to endDay
18%7%34423447%38%
1872
January1st to 15thNight
14%424424436%47%
2522
16th to endNight
14%6%24424446%44%
2704
February1st to 15thNight
14%7%24323446%45%
2473
16th to endNight
12%5%24425%45%7%44%
2025
March1st to 15thNight
14%42432445%6%46%
2145
16th to endNight
17%4234245%46%42%
2288
April1st to 15thNight
13%6%235%3345%7%45%
2031
16th to endNight
15%424423447%45%
1850
May1st to 15thNight
14%6%25%4245%5%7%40%
1754
16th to endNight
14%5%245%25%46%9%39%
1826
June1st to 15thNight
10%3145%35%5%7%11%43%
1755
16th to endNight
7%32443446%12%46%
1755
July1st to 15thNight
9%423435%6%6%8%44%
1755
16th to endNight
5%4245%36%6%9%12%39%
1847
August1st to 15thNight
13%425%42446%10%40%
1726
16th to endNight
9%3245%35%6%6%9%42%
1975
September1st to 15thNight
14%425%43445%6%45%
2041
16th to endNight
20%5%25%43335%5%39%
2145
October1st to 15thNight
17%414433346%45%
2328
16th to endNight
12%313313345%55%
2447
November1st to 15thNight
15%5%2332433452%
2316
16th to endNight
13%413223346%52%
2535
December1st to 15thNight
15%6%25%424445%43%
2622
16th to endNight
16%8%26%425%448%36%
2704

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
40%411%22%17%4
1747
16th to endDay
42%37%26%16%4
1872
February1st to 15thDay
44%39%22%17%2
1712
16th to endDay
44%311%22%15%2
1731
March1st to 15thDay
38%5%8%23%18%5%
2145
16th to endDay
47%5%8%22%14%2
2288
April1st to 15thDay
35%412%26%14%6%
2246
16th to endDay
44%49%20%15%5%
2396
May1st to 15thDay
48%6%14%18%9%2
2526
16th to endDay
46%7%14%21%8%1
2643
June1st to 15thDay
41%8%16%21%10%
2535
16th to endDay
41%8%14%19%13%2
2535
July1st to 15thDay
47%8%12%17%12%2
2396
16th to endDay
46%9%15%17%10%
2518
August1st to 15thDay
49%6%14%19%9%
2474
16th to endDay
46%7%14%18%10%1
2564
September1st to 15thDay
44%5%11%19%17%2
2246
16th to endDay
51%5%7%19%14%1
2145
October1st to 15thDay
39%410%24%16%4
1960
16th to endDay
35%36%27%21%5%
2034
November1st to 15thDay
36%38%18%25%6%
1871
16th to endDay
37%37%24%24%3
1755
December1st to 15thDay
40%411%20%18%4
1639
16th to endDay
46%49%21%15%2
1872
January1st to 15thNight
37%49%19%19%8%
2522
16th to endNight
39%210%24%18%3
2704
February1st to 15thNight
39%39%25%17%3
2482
16th to endNight
38%412%26%14%2
2025
March1st to 15thNight
36%6%9%26%16%4
2145
16th to endNight
41%5%11%22%15%2
2288
April1st to 15thNight
38%311%23%17%4
2031
16th to endNight
39%411%21%18%5%
1850
May1st to 15thNight
42%6%14%22%13%1
1755
16th to endNight
40%7%18%23%9%1
1828
June1st to 15thNight
32%9%19%24%12%1
1755
16th to endNight
30%8%16%26%15%2
1755
July1st to 15thNight
34%9%16%21%13%4
1665
16th to endNight
32%9%19%24%11%1
1739
August1st to 15thNight
38%7%16%22%14%1
1715
16th to endNight
36%7%17%24%12%1
1975
September1st to 15thNight
39%6%12%22%15%4
2041
16th to endNight
46%5%8%20%17%1
2145
October1st to 15thNight
39%48%25%18%3
2328
16th to endNight
31%37%28%24%5%
2447
November1st to 15thNight
37%37%20%23%8%
2316
16th to endNight
33%37%26%25%4
2535
December1st to 15thNight
42%48%23%16%4
2622
16th to endNight
46%411%18%16%2
2704

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
26%25%27%17%3
135
16th to endDay
29%25%32%9%2
144
February1st to 15thDay
28%29%36%5%
135
16th to endDay
26%29%23%15%4
169
March1st to 15thDay
23%23%26%19%6%
330
16th to endDay
22%21%26%21%6%1
352
April1st to 15thDay
16%21%25%22%11%1
330
16th to endDay
23%9%22%21%17%5%
319
May1st to 15thDay
23%12%26%17%12%7%
348
16th to endDay
21%7%18%21%21%10%
395
June1st to 15thDay
14%5%16%29%25%8%
375
16th to endDay
13%7%24%25%19%10%
375
July1st to 15thDay
14%216%29%24%12%
365
16th to endDay
14%310%28%28%14%
390
August1st to 15thDay
18%115%23%22%17%
358
16th to endDay
13%28%25%20%29%
396
September1st to 15thDay
21%412%16%25%20%
375
16th to endDay
26%314%24%20%11%
374
October1st to 15thDay
22%8%14%22%24%8%
375
16th to endDay
14%17%25%22%15%4
382
November1st to 15thDay
22%11%23%22%16%2
289
16th to endDay
17%20%26%25%8%1
135
December1st to 15thDay
20%29%27%18%2
108
16th to endDay
31%18%34%13%
144
January1st to 15thNight
21%23%27%22%5%
780
16th to endNight
21%21%31%23%1
832
February1st to 15thNight
23%22%30%22%
764
16th to endNight
19%24%31%21%2
683
March1st to 15thNight
20%18%30%26%3
780
16th to endNight
19%15%30%24%7%
832
April1st to 15thNight
20%16%29%24%8%
778
16th to endNight
19%10%23%30%14%1
694
May1st to 15thNight
18%7%23%29%18%1
585
16th to endNight
16%315%28%30%5%
611
June1st to 15thNight
10%112%36%35%3
585
16th to endNight
9%112%35%34%6%
585
July1st to 15thNight
12%18%34%36%6%
555
16th to endNight
6%8%32%44%7%
612
August1st to 15thNight
16%8%32%34%6%
575
16th to endNight
11%17%25%44%9%
733
September1st to 15thNight
16%29%26%35%9%
780
16th to endNight
23%312%26%27%5%
777
October1st to 15thNight
20%6%16%24%25%6%
780
16th to endNight
16%11%25%28%14%2
816
November1st to 15thNight
19%11%20%29%15%2
760
16th to endNight
19%16%22%26%15%
780
December1st to 15thNight
20%18%25%26%8%
780
16th to endNight
22%20%26%25%4
832
Page generated at 2018-10-28 08:41:06. Version ac04

Copyright 2018 A. Danko


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