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 2017-03-13.

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
41%
15174
22%
45193
12%
15136
51%
15136
25%
28333

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
22%
718
24%
2327
8%
716
41%
716
18%
1408
January16th to endNight
19%
768
24%
2496
7%
768
39%
768
20%
1526
February1st to 15thNight
19%
701
23%
2287
7%
701
37%
701
19%
1376
February16th to endNight
18%
631
25%
1871
7%
631
37%
631
20%
1168
March1st to 15thNight
27%
712
24%
1958
10%
712
40%
712
23%
1256
March16th to endNight
27%
704
19%
1936
9%
704
36%
704
22%
1276
April1st to 15thNight
27%
658
21%
1718
6%
658
37%
658
26%
1122
April16th to endNight
39%
595
23%
1585
9%
595
47%
595
29%
1020
May1st to 15thNight
41%
495
16%
1485
8%
495
47%
495
22%
1003
May16th to endNight
58%
513
15%
1540
10%
513
61%
513
30%
971
June1st to 15thNight
65%
495
17%
1485
16%
495
67%
495
32%
932
June16th to endNight
68%
495
18%
1485
14%
495
72%
495
35%
884
July1st to 15thNight
64%
465
13%
1395
11%
465
67%
465
27%
917
July16th to endNight
73%
522
15%
1469
13%
489
76%
489
32%
897
August1st to 15thNight
64%
494
20%
1474
16%
491
65%
491
29%
939
August16th to endNight
67%
619
17%
1669
13%
619
68%
619
30%
1108
September1st to 15thNight
63%
660
25%
1727
19%
660
65%
660
33%
1118
September16th to endNight
47%
657
18%
1815
15%
657
49%
657
23%
1262
October1st to 15thNight
49%
660
27%
1970
23%
660
57%
660
28%
1219
October16th to endNight
41%
704
32%
2112
20%
704
57%
704
33%
1172
November1st to 15thNight
43%
700
27%
2133
18%
700
56%
700
29%
1253
November16th to endNight
36%
720
27%
2340
15%
720
51%
720
25%
1338
December1st to 15thNight
28%
720
23%
2420
9%
720
43%
720
17%
1517
December16th to endNight
23%
768
22%
2496
8%
768
39%
768
15%
1651

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%
45448
Night
13%5%2442445%7%44%
45386
Cloud CoverDay
14%5%25%5%35%5%5%7%38%
45458
Night
13%5%2442445%7%44%
45390
TransparencyDay
43%5%11%21%15%3
45159
Night
38%5%11%23%17%3
45193
SeeingDay
19%11%19%22%17%9%
4872
Night
18%12%22%26%17%2
15181

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%5%25%43445%7%42%
1611
16th to endDay
12%6%25%5%34446%43%
1728
February1st to 15thDay
11%7%26%5%35%436%41%
1575
16th to endDay
13%5%35%5%35%348%40%
1599
March1st to 15thDay
14%42442445%6%45%
1938
16th to endDay
18%7%35%425%345%38%
1936
April1st to 15thDay
11%41442445%7%48%
1899
16th to endDay
16%5%25%6%25%35%6%40%
2054
May1st to 15thDay
18%6%25%5%35%5%6%7%31%
2136
16th to endDay
13%5%246%35%5%7%8%35%
2223
June1st to 15thDay
11%4245%47%7%7%9%34%
2145
16th to endDay
8%426%5%46%6%7%8%38%
2145
July1st to 15thDay
12%5%36%7%5%8%7%6%8%28%
2145
16th to endDay
9%437%7%47%6%8%10%29%
2283
August1st to 15thDay
15%5%25%7%5%6%6%8%9%28%
2145
16th to endDay
14%5%26%6%46%6%6%9%31%
2168
September1st to 15thDay
14%6%246%2445%7%40%
1900
16th to endDay
25%7%26%42345%5%32%
1815
October1st to 15thDay
19%413323245%48%
1658
16th to endDay
13%5%25%424335%49%
1760
November1st to 15thDay
12%324323346%52%
1724
16th to endDay
16%5%24413336%46%
1620
December1st to 15thDay
12%5%245%35%45%7%44%
1513
16th to endDay
19%7%34424347%38%
1728
January1st to 15thNight
13%424434446%47%
2327
16th to endNight
14%6%245%2445%6%43%
2496
February1st to 15thNight
14%7%14323446%46%
2285
16th to endNight
12%425%425%45%6%45%
1871
March1st to 15thNight
13%5%2342445%7%45%
1946
16th to endNight
17%4245%245%47%42%
1936
April1st to 15thNight
13%6%2443345%6%45%
1718
16th to endNight
14%4235%245%47%45%
1585
May1st to 15thNight
15%6%35%43445%7%38%
1485
16th to endNight
10%3245%345%6%10%42%
1538
June1st to 15thNight
10%3145%345%7%10%43%
1485
16th to endNight
6%32442446%11%49%
1485
July1st to 15thNight
10%424435%6%7%8%41%
1485
16th to endNight
5%2145%36%7%8%13%39%
1577
August1st to 15thNight
13%4245%2445%10%41%
1485
16th to endNight
10%325%5%36%6%7%9%40%
1669
September1st to 15thNight
12%326%43446%6%46%
1727
16th to endNight
20%5%25%423346%38%
1815
October1st to 15thNight
17%413424246%47%
1970
16th to endNight
12%413313345%55%
2112
November1st to 15thNight
14%413323335%52%
2133
16th to endNight
15%5%13313346%51%
2340
December1st to 15thNight
15%6%35%42435%5%43%
2420
16th to endNight
16%8%35%434447%37%
2496

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%245%3445%7%42%
1611
16th to endDay
13%6%35%5%34445%43%
1728
February1st to 15thDay
12%7%25%6%35%446%41%
1575
16th to endDay
14%5%35%5%4435%8%40%
1599
March1st to 15thDay
14%4245%2445%6%45%
1949
16th to endDay
19%7%34425%446%38%
1935
April1st to 15thDay
11%414425%45%7%47%
1899
16th to endDay
16%5%25%6%2445%5%40%
2054
May1st to 15thDay
18%6%25%5%36%5%6%7%31%
2136
16th to endDay
13%425%6%35%5%6%9%35%
2223
June1st to 15thDay
12%325%6%48%6%7%9%34%
2145
16th to endDay
9%335%5%46%7%6%9%38%
2145
July1st to 15thDay
12%5%36%8%48%6%6%9%27%
2145
16th to endDay
10%5%37%7%5%7%6%8%10%28%
2283
August1st to 15thDay
15%425%7%47%6%8%9%28%
2145
16th to endDay
13%5%26%5%5%6%7%7%8%30%
2168
September1st to 15thDay
14%6%25%5%25%45%7%40%
1900
16th to endDay
25%6%35%42445%5%31%
1815
October1st to 15thDay
19%5%13323345%48%
1658
16th to endDay
13%5%24324335%50%
1760
November1st to 15thDay
12%323423346%52%
1724
16th to endDay
16%415%5%13336%47%
1620
December1st to 15thDay
13%5%15%5%35%35%7%44%
1513
16th to endDay
19%7%34424447%38%
1728
January1st to 15thNight
14%424434436%47%
2327
16th to endNight
14%6%245%2445%6%43%
2496
February1st to 15thNight
14%7%23323446%46%
2278
16th to endNight
12%5%245%25%45%7%45%
1871
March1st to 15thNight
13%43432445%7%45%
1958
16th to endNight
18%3234245%46%43%
1936
April1st to 15thNight
14%6%2343345%7%44%
1718
16th to endNight
14%4235%235%47%45%
1585
May1st to 15thNight
15%6%35%4245%5%7%38%
1484
16th to endNight
10%3245%35%5%7%10%42%
1538
June1st to 15thNight
10%3145%245%7%11%43%
1485
16th to endNight
6%32443446%11%48%
1485
July1st to 15thNight
10%424435%6%7%8%41%
1485
16th to endNight
4324437%6%9%12%39%
1577
August1st to 15thNight
13%425%42446%10%41%
1485
16th to endNight
10%3245%36%6%6%10%40%
1669
September1st to 15thNight
11%325%43445%6%47%
1727
16th to endNight
20%6%26%424345%38%
1815
October1st to 15thNight
16%414423336%47%
1970
16th to endNight
12%413313345%56%
2112
November1st to 15thNight
15%42332433453%
2133
16th to endNight
15%5%13323346%51%
2340
December1st to 15thNight
15%6%35%42445%5%43%
2420
16th to endNight
16%8%26%435%448%36%
2496

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
41%411%23%16%3
1612
16th to endDay
42%37%26%16%4
1728
February1st to 15thDay
44%39%22%18%2
1577
16th to endDay
43%312%22%16%2
1599
March1st to 15thDay
38%5%9%24%17%4
1949
16th to endDay
47%47%23%13%2
1936
April1st to 15thDay
35%312%25%15%7%
1899
16th to endDay
44%38%20%16%5%
2054
May1st to 15thDay
50%6%14%16%9%1
2136
16th to endDay
44%6%15%22%9%1
2227
June1st to 15thDay
42%7%17%21%10%
2145
16th to endDay
40%8%15%19%13%2
2145
July1st to 15thDay
50%8%12%14%12%2
2006
16th to endDay
45%10%16%17%9%
2128
August1st to 15thDay
49%6%13%19%9%
2132
16th to endDay
47%7%14%17%10%2
2168
September1st to 15thDay
42%5%10%18%19%2
1900
16th to endDay
52%5%6%19%15%1
1815
October1st to 15thDay
38%310%25%17%4
1658
16th to endDay
37%36%25%20%6%
1760
November1st to 15thDay
33%38%19%27%7%
1724
16th to endDay
39%37%24%21%3
1620
December1st to 15thDay
39%411%20%18%5%
1513
16th to endDay
46%49%20%16%2
1728
January1st to 15thNight
38%49%20%19%7%
2327
16th to endNight
40%310%24%17%3
2496
February1st to 15thNight
38%39%25%19%4
2287
16th to endNight
38%411%26%15%2
1871
March1st to 15thNight
37%6%9%28%15%3
1958
16th to endNight
41%5%11%24%15%2
1936
April1st to 15thNight
39%311%21%18%5%
1718
16th to endNight
38%410%22%18%6%
1585
May1st to 15thNight
44%5%15%21%11%
1485
16th to endNight
35%7%20%25%9%1
1540
June1st to 15thNight
32%9%20%24%11%1
1485
16th to endNight
29%8%16%26%15%2
1485
July1st to 15thNight
37%9%15%19%12%4
1395
16th to endNight
31%9%21%25%11%1
1469
August1st to 15thNight
38%6%16%20%16%1
1474
16th to endNight
38%7%15%23%13%1
1669
September1st to 15thNight
36%6%12%22%17%4
1727
16th to endNight
47%5%8%18%18%1
1815
October1st to 15thNight
38%38%25%19%3
1970
16th to endNight
30%37%29%23%5%
2112
November1st to 15thNight
35%37%19%25%9%
2133
16th to endNight
35%37%25%23%4
2340
December1st to 15thNight
42%48%23%16%4
2420
16th to endNight
46%410%18%17%2
2496

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%24%31%15%3
90
16th to endDay
30%28%31%9%1
96
February1st to 15thDay
22%33%38%41
90
16th to endDay
22%32%22%19%3
126
March1st to 15thDay
21%19%28%22%8%
259
16th to endDay
24%18%25%20%8%2
224
April1st to 15thDay
16%20%20%26%13%1
210
16th to endDay
20%8%19%20%22%8%
210
May1st to 15thDay
25%10%27%15%12%8%
228
16th to endDay
17%7%17%19%23%13%
267
June1st to 15thDay
16%5%12%29%25%9%
255
16th to endDay
12%7%22%26%21%10%
255
July1st to 15thDay
18%120%26%20%11%
245
16th to endDay
10%27%27%31%20%
270
August1st to 15thDay
18%113%21%24%19%
253
16th to endDay
14%18%23%19%33%
268
September1st to 15thDay
14%310%16%32%22%
255
16th to endDay
29%314%21%19%11%
254
October1st to 15thDay
23%8%16%24%21%7%
255
16th to endDay
16%14%23%25%16%4
272
November1st to 15thDay
19%14%21%22%18%3
232
16th to endDay
23%18%24%23%10%
90
December1st to 15thDay
19%33%23%18%41
72
16th to endDay
36%16%30%16%
96
January1st to 15thNight
20%23%28%22%4
720
16th to endNight
22%20%33%22%1
768
February1st to 15thNight
23%22%30%22%
704
16th to endNight
19%25%32%20%2
631
March1st to 15thNight
19%16%31%26%4
712
16th to endNight
20%16%31%23%8%1
704
April1st to 15thNight
20%17%30%22%8%
658
16th to endNight
18%10%24%29%15%1
595
May1st to 15thNight
19%7%24%28%17%1
495
16th to endNight
12%316%28%32%6%
515
June1st to 15thNight
10%113%37%34%3
495
16th to endNight
8%112%34%35%6%
495
July1st to 15thNight
13%110%36%33%4
465
16th to endNight
5%9%31%44%9%
522
August1st to 15thNight
16%18%32%34%6%
494
16th to endNight
12%18%25%43%9%
619
September1st to 15thNight
13%39%27%38%7%
660
16th to endNight
24%314%26%26%3
657
October1st to 15thNight
20%7%18%25%22%6%
660
16th to endNight
16%11%26%29%13%2
704
November1st to 15thNight
18%12%21%29%15%3
700
16th to endNight
20%16%22%25%14%
720
December1st to 15thNight
20%19%24%26%8%
720
16th to endNight
22%20%26%24%5%
768
Page generated at 2017-03-14 04:34:44. Version ac04

Copyright 2017 A. Danko


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