Climax Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Climax Observatory clear sky chart from 2005-11-05 to 2017-10-31.

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%
16089
22%
47397
12%
16042
48%
16042
30%
27285

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
25%
881
22%
2487
8%
876
38%
876
25%
1440
January16th to endNight
24%
768
25%
2496
12%
768
40%
768
27%
1405
February1st to 15thNight
19%
701
16%
2283
5%
697
33%
697
21%
1381
February16th to endNight
18%
632
22%
1894
5%
632
36%
632
24%
1122
March1st to 15thNight
28%
720
22%
2061
8%
720
40%
720
31%
1160
March16th to endNight
26%
713
21%
2057
9%
713
37%
713
25%
1240
April1st to 15thNight
26%
539
19%
1798
9%
539
38%
539
26%
988
April16th to endNight
29%
540
19%
1800
12%
540
40%
540
23%
1049
May1st to 15thNight
32%
540
17%
1617
8%
540
43%
540
25%
1017
May16th to endNight
42%
563
18%
1498
9%
561
50%
561
31%
906
June1st to 15thNight
49%
540
25%
1440
14%
540
57%
540
47%
748
June16th to endNight
64%
540
28%
1440
21%
540
69%
540
52%
739
July1st to 15thNight
64%
510
16%
1360
13%
510
66%
510
32%
865
July16th to endNight
71%
564
16%
1511
15%
531
72%
531
31%
927
August1st to 15thNight
64%
539
16%
1632
14%
536
66%
536
30%
972
August16th to endNight
62%
573
23%
1910
22%
573
66%
573
30%
1108
September1st to 15thNight
63%
540
27%
1800
24%
540
70%
540
33%
999
September16th to endNight
58%
580
31%
1944
23%
580
70%
580
40%
977
October1st to 15thNight
38%
720
26%
2160
14%
720
49%
720
36%
1153
October16th to endNight
41%
768
33%
2304
15%
768
56%
768
37%
1197
November1st to 15thNight
33%
858
29%
2258
12%
858
45%
858
38%
1260
November16th to endNight
32%
900
28%
2439
12%
900
43%
900
33%
1370
December1st to 15thNight
20%
900
16%
2520
3%
900
31%
900
22%
1540
December16th to endNight
21%
960
18%
2688
7%
960
31%
960
21%
1722

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
6%8%48%7%34446%41%
48363
Night
2436%6%3445%7%50%
47577
TransparencyDay
42%5%12%20%14%4
48045
Night
29%6%17%25%16%4
47397
SeeingDay
18%24%26%18%10%2
5948
Night
7%19%28%26%15%2
16092

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 15thDay
5%5%11%9%35%5%36%44%
1462
16th to endDay
6%410%7%24436%48%
1728
February1st to 15thDay
5%6%15%11%34345%39%
1580
16th to endDay
45%14%10%45%435%40%
1580
March1st to 15thDay
8%5%11%8%33346%43%
1896
16th to endDay
310%6%11%7%34346%38%
2166
April1st to 15thDay
312%5%11%6%34346%37%
2150
16th to endDay
316%8%11%8%35%435%30%
2160
May1st to 15thDay
6%15%6%8%6%35%45%6%31%
2331
16th to endDay
8%12%49%6%35%447%33%
2616
June1st to 15thDay
8%6%25%42445%7%45%
2520
16th to endDay
5%4245%34446%53%
2520
July1st to 15thDay
13%6%38%6%35%46%5%35%
2520
16th to endDay
15%7%47%8%46%6%5%6%28%
2551
August1st to 15thDay
18%9%37%7%35%346%29%
2317
16th to endDay
13%8%48%6%45%45%5%33%
2292
September1st to 15thDay
13%7%36%5%4333445%
2160
16th to endDay
7%9%35%5%23335%49%
2013
October1st to 15thDay
6%9%35%5%23235%50%
1800
16th to endDay
37%37%423345%53%
1918
November1st to 15thDay
16%46%422446%54%
1589
16th to endDay
5%45%9%12237%57%
1518
December1st to 15thDay
5%312%8%5%6%5%48%39%
1440
16th to endDay
5%5%12%9%5%5%45%7%36%
1536
January1st to 15thNight
228%8%46%5%5%8%47%
2487
16th to endNight
336%10%45%445%51%
2496
February1st to 15thNight
3410%12%35%45%7%42%
2272
16th to endNight
35%11%7%46%5%5%6%43%
1894
March1st to 15thNight
437%7%3345%6%52%
2061
16th to endNight
26%5%7%7%33446%49%
2057
April1st to 15thNight
6%37%6%36%45%7%47%
1798
16th to endNight
210%37%6%34447%45%
1800
May1st to 15thNight
5%10%27%5%3345%7%42%
1616
16th to endNight
47%245%35%46%9%47%
1497
June1st to 15thNight
231231345%9%62%
1440
16th to endNight
22123235%5%7%63%
1440
July1st to 15thNight
5%426%435%6%7%9%43%
1440
16th to endNight
7%325%5%36%6%6%9%43%
1615
August1st to 15thNight
8%5%25%4245%6%8%46%
1641
16th to endNight
6%5%25%5%2446%7%47%
1910
September1st to 15thNight
6%425%4245%5%7%50%
1800
16th to endNight
3424323447%59%
1944
October1st to 15thNight
45%23424446%57%
2160
16th to endNight
15%16%413336%61%
2304
November1st to 15thNight
435%324447%59%
2258
16th to endNight
327%8%23346%56%
2439
December1st to 15thNight
339%10%45%446%46%
2520
16th to endNight
339%12%6%6%5%47%41%
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
38%5%21%20%10%2
1463
16th to endDay
35%6%18%23%13%3
1728
February1st to 15thDay
44%5%17%19%9%3
1580
16th to endDay
41%315%23%13%2
1580
March1st to 15thDay
39%415%24%14%1
1896
16th to endDay
44%413%25%9%2
2166
April1st to 15thDay
45%413%20%12%3
2150
16th to endDay
53%311%21%7%1
2160
May1st to 15thDay
52%411%20%9%
2331
16th to endDay
49%412%20%10%2
2620
June1st to 15thDay
36%410%18%21%7%
2520
16th to endDay
31%45%21%26%10%
2520
July1st to 15thDay
47%6%10%12%14%7%
2371
16th to endDay
52%7%13%14%8%3
2392
August1st to 15thDay
55%6%8%12%12%4
2302
16th to endDay
50%5%9%18%13%3
2292
September1st to 15thDay
43%37%16%20%7%
2160
16th to endDay
36%28%25%22%2
2013
October1st to 15thDay
36%37%25%23%4
1800
16th to endDay
30%311%29%20%4
1918
November1st to 15thDay
26%415%22%24%5%
1589
16th to endDay
27%315%30%16%5%
1518
December1st to 15thDay
37%7%19%25%10%
1440
16th to endDay
42%9%15%18%11%3
1536
January1st to 15thNight
27%7%24%24%12%2
2487
16th to endNight
29%6%19%24%15%4
2496
February1st to 15thNight
36%5%20%23%12%2
2283
16th to endNight
33%417%25%16%3
1894
March1st to 15thNight
27%419%31%14%3
2061
16th to endNight
33%5%17%30%11%2
2057
April1st to 15thNight
30%5%18%27%14%3
1798
16th to endNight
35%5%19%27%11%1
1800
May1st to 15thNight
38%5%16%27%10%
1617
16th to endNight
32%6%16%29%13%2
1498
June1st to 15thNight
18%5%15%26%25%7%
1440
16th to endNight
18%411%25%28%12%
1440
July1st to 15thNight
33%9%15%17%16%7%
1360
16th to endNight
32%9%22%19%11%3
1511
August1st to 15thNight
33%7%19%18%14%5%
1632
16th to endNight
33%7%15%23%17%3
1910
September1st to 15thNight
29%6%14%21%20%7%
1800
16th to endNight
23%5%14%34%20%2
1944
October1st to 15thNight
24%414%28%22%6%
2160
16th to endNight
23%312%33%22%4
2304
November1st to 15thNight
21%6%14%27%22%6%
2258
16th to endNight
26%414%29%20%4
2439
December1st to 15thNight
31%7%23%22%13%1
2520
16th to endNight
37%7%21%19%12%2
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
22%23%24%15%14%
90
16th to endDay
15%31%34%16%2
96
February1st to 15thDay
25%37%23%13%
90
16th to endDay
22%30%25%17%3
81
March1st to 15thDay
20%38%25%12%3
186
16th to endDay
18%45%26%8%1
288
April1st to 15thDay
21%37%28%9%21
269
16th to endDay
26%43%19%8%2
270
May1st to 15thDay
18%28%29%16%5%1
366
16th to endDay
17%23%27%18%9%3
517
June1st to 15thDay
13%22%24%21%16%2
495
16th to endDay
7%15%30%22%20%3
495
July1st to 15thDay
17%9%20%24%22%5%
475
16th to endDay
20%8%21%25%18%6%
410
August1st to 15thDay
21%15%27%24%8%1
315
16th to endDay
19%12%29%25%11%2
332
September1st to 15thDay
23%19%33%15%6%1
315
16th to endDay
22%20%28%17%7%4
213
October1st to 15thDay
17%27%22%17%13%2
135
16th to endDay
15%28%24%18%11%2
144
November1st to 15thDay
14%20%23%20%16%5%
90
16th to endDay
23%33%32%10%1
90
December1st to 15thDay
21%46%23%6%2
90
16th to endDay
8%47%29%8%6%
96
January1st to 15thNight
10%30%29%17%9%2
881
16th to endNight
9%25%36%19%7%1
768
February1st to 15thNight
7%29%36%20%5%
704
16th to endNight
9%29%37%19%4
632
March1st to 15thNight
6%26%33%24%8%
720
16th to endNight
6%26%36%23%6%
713
April1st to 15thNight
6%25%37%23%7%
539
16th to endNight
10%22%32%25%7%
540
May1st to 15thNight
10%15%35%25%12%1
540
16th to endNight
7%13%28%28%18%2
563
June1st to 15thNight
5%9%32%33%18%1
540
16th to endNight
26%21%38%28%2
540
July1st to 15thNight
7%212%33%38%3
510
16th to endNight
5%27%33%44%6%
564
August1st to 15thNight
9%112%33%38%4
539
16th to endNight
8%312%32%35%6%
573
September1st to 15thNight
6%217%41%26%6%
540
16th to endNight
6%8%21%33%25%4
580
October1st to 15thNight
6%19%31%24%13%4
720
16th to endNight
6%20%27%26%15%3
768
November1st to 15thNight
8%22%31%25%10%1
858
16th to endNight
7%27%29%26%7%1
900
December1st to 15thNight
8%36%33%16%41
900
16th to endNight
11%30%31%20%6%
960
Page generated at 2017-11-01 15:23:36. Version ac04

Copyright 2017 A. Danko


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