Cordes Lakes Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cordes Lakes Observatory clear sky chart from 2005-11-05 to 2018-02-13.

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
75%
16241
36%
48762
30%
16202
80%
16202
54%
23119

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
67%
779
33%
2522
29%
776
76%
776
45%
1226
January16th to endNight
63%
832
37%
2704
34%
832
72%
832
43%
1372
February1st to 15thNight
69%
746
36%
2336
31%
746
80%
746
51%
1102
February16th to endNight
65%
632
36%
1895
34%
632
71%
632
48%
967
March1st to 15thNight
66%
720
38%
1985
30%
720
75%
720
56%
978
March16th to endNight
72%
768
37%
2112
28%
768
79%
768
58%
1010
April1st to 15thNight
63%
710
31%
1969
18%
710
72%
710
55%
979
April16th to endNight
65%
540
45%
1665
33%
540
77%
540
72%
649
May1st to 15thNight
74%
539
37%
1619
29%
539
80%
539
62%
696
May16th to endNight
77%
561
39%
1684
30%
561
82%
561
70%
684
June1st to 15thNight
82%
540
33%
1620
30%
540
83%
540
71%
661
June16th to endNight
89%
540
35%
1620
31%
540
89%
540
73%
653
July1st to 15thNight
86%
510
23%
1530
20%
510
86%
510
47%
780
July16th to endNight
83%
564
23%
1593
20%
531
84%
531
38%
900
August1st to 15thNight
88%
539
29%
1611
25%
536
89%
536
46%
827
August16th to endNight
86%
645
32%
1853
28%
645
86%
645
45%
1008
September1st to 15thNight
83%
720
31%
1980
25%
720
85%
720
51%
1046
September16th to endNight
84%
716
45%
1980
35%
716
88%
716
69%
880
October1st to 15thNight
79%
720
39%
2058
32%
720
83%
720
63%
927
October16th to endNight
82%
768
45%
2304
38%
768
87%
768
66%
989
November1st to 15thNight
78%
760
38%
2348
33%
760
84%
760
60%
1048
November16th to endNight
73%
780
42%
2535
39%
780
81%
780
55%
1101
December1st to 15thNight
70%
780
35%
2535
33%
780
77%
780
46%
1213
December16th to endNight
64%
832
34%
2704
31%
832
71%
832
38%
1423

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
2212313346%67%
49276
Night
3212213346%68%
48958
TransparencyDay
18%46%15%27%28%
48971
Night
17%36%14%27%30%
48764
SeeingDay
410%24%33%20%6%
5935
Night
4313%36%36%6%
16251

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
4212313346%64%
1746
16th to endDay
6%312313346%62%
1872
February1st to 15thDay
2323323346%65%
1791
16th to endDay
4313424346%60%
1579
March1st to 15thDay
3312313346%67%
1974
16th to endDay
2212313346%68%
2112
April1st to 15thDay
21222345%7%67%
1977
16th to endDay
112212236%76%
2292
May1st to 15thDay
111212346%73%
2331
16th to endDay
221112235%76%
2429
June1st to 15thDay
111112483%
2340
16th to endDay
11122382%
2340
July1st to 15thDay
2212435%6%6%9%55%
2340
16th to endDay
43346%37%6%9%10%39%
2467
August1st to 15thDay
3214425%5%7%10%53%
2340
16th to endDay
32124245%6%8%56%
2345
September1st to 15thDay
32123235%5%7%60%
1980
16th to endDay
2111123480%
1980
October1st to 15thDay
11121223476%
1902
16th to endDay
112111235%77%
1920
November1st to 15thDay
2121345%5%70%
1837
16th to endDay
4212212235%72%
1755
December1st to 15thDay
4412324436%62%
1755
16th to endDay
5%5%23323347%57%
1872
January1st to 15thNight
4212224346%64%
2522
16th to endNight
6%313322335%64%
2704
February1st to 15thNight
2312212246%69%
2325
16th to endNight
6%21222336%8%61%
1895
March1st to 15thNight
3211214345%68%
1985
16th to endNight
2112212446%71%
2112
April1st to 15thNight
3112212445%69%
1969
16th to endNight
11111225%81%
1665
May1st to 15thNight
111212345%75%
1619
16th to endNight
1111112482%
1684
June1st to 15thNight
1111222480%
1620
16th to endNight
11111212383%
1620
July1st to 15thNight
11133245%7%8%58%
1620
16th to endNight
1224436%6%8%12%47%
1701
August1st to 15thNight
1112325%6%7%10%56%
1620
16th to endNight
1113435%6%6%9%56%
1853
September1st to 15thNight
221232347%8%60%
1980
16th to endNight
11111222480%
1980
October1st to 15thNight
2111212235%75%
2058
16th to endNight
111212235%77%
2304
November1st to 15thNight
1212212445%72%
2348
16th to endNight
311213235%73%
2535
December1st to 15thNight
4213222345%66%
2535
16th to endNight
6%413323345%60%
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
22%3416%32%19%
1747
16th to endDay
23%25%17%31%18%
1872
February1st to 15thDay
21%35%16%29%23%
1791
16th to endDay
26%35%18%27%17%
1579
March1st to 15thDay
19%3315%35%23%
1974
16th to endDay
18%35%16%36%19%
2112
April1st to 15thDay
16%3416%33%24%
1977
16th to endDay
11%3314%33%33%
2292
May1st to 15thDay
12%3414%30%34%
2331
16th to endDay
12%2411%32%37%
2432
June1st to 15thDay
8%126%26%55%
2340
16th to endDay
8%125%19%62%
2340
July1st to 15thDay
21%7%11%16%16%27%
2201
16th to endDay
31%12%16%17%15%6%
2312
August1st to 15thDay
24%7%11%16%19%21%
2325
16th to endDay
22%7%11%18%24%15%
2345
September1st to 15thDay
21%5%10%16%24%21%
1980
16th to endDay
10%2310%33%39%
1980
October1st to 15thDay
13%2313%26%38%
1902
16th to endDay
11%15%13%31%35%
1920
November1st to 15thDay
14%3418%32%25%
1837
16th to endDay
17%2315%29%32%
1755
December1st to 15thDay
25%48%18%24%18%
1755
16th to endDay
28%37%19%28%12%
1872
January1st to 15thNight
23%25%15%32%20%
2522
16th to endNight
25%2416%28%22%
2704
February1st to 15thNight
18%36%16%28%26%
2336
16th to endNight
22%35%18%30%19%
1895
March1st to 15thNight
17%2412%34%27%
1985
16th to endNight
14%35%16%34%24%
2112
April1st to 15thNight
17%2414%31%28%
1969
16th to endNight
8%1413%33%39%
1665
May1st to 15thNight
11%3313%29%38%
1620
16th to endNight
9%1210%33%41%
1685
June1st to 15thNight
10%125%19%61%
1620
16th to endNight
9%11413%69%
1620
July1st to 15thNight
19%6%12%13%18%29%
1530
16th to endNight
25%9%15%21%18%9%
1593
August1st to 15thNight
18%8%11%17%18%24%
1611
16th to endNight
22%6%9%18%22%18%
1853
September1st to 15thNight
19%6%11%19%19%23%
1980
16th to endNight
11%228%34%41%
1980
October1st to 15thNight
13%2314%26%39%
2058
16th to endNight
11%25%10%24%45%
2304
November1st to 15thNight
15%2415%35%26%
2348
16th to endNight
15%2313%28%35%
2535
December1st to 15thNight
21%36%18%26%23%
2535
16th to endNight
27%36%18%29%13%
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
20%7%13%34%20%3
135
16th to endDay
11%7%16%30%25%8%
144
February1st to 15thDay
311%27%28%22%5%
234
16th to endDay
8%23%33%22%10%1
238
March1st to 15thDay
7%17%30%25%14%5%
270
16th to endDay
421%31%28%12%2
288
April1st to 15thDay
8%19%34%24%7%5%
269
16th to endDay
427%39%20%5%2
270
May1st to 15thDay
318%38%25%10%3
288
16th to endDay
5%14%33%30%13%3
330
June1st to 15thDay
29%38%31%14%4
315
16th to endDay
221%46%21%7%
315
July1st to 15thDay
2218%48%21%6%
305
16th to endDay
5%8%43%28%13%
327
August1st to 15thDay
214%44%29%8%
315
16th to endDay
318%43%33%10%
332
September1st to 15thDay
4221%40%23%6%
315
16th to endDay
47%21%40%20%4
315
October1st to 15thDay
210%35%24%21%5%
237
16th to endDay
4410%30%31%17%
144
November1st to 15thDay
27%16%34%32%6%
135
16th to endDay
6%7%22%31%24%7%
135
December1st to 15thDay
411%14%32%37%
135
16th to endDay
8%11%12%34%27%6%
144
January1st to 15thNight
5%417%43%23%5%
780
16th to endNight
8%5%19%39%25%2
832
February1st to 15thNight
4317%44%26%3
752
16th to endNight
7%5%18%47%17%2
632
March1st to 15thNight
5%421%39%24%4
720
16th to endNight
25%16%41%29%3
768
April1st to 15thNight
35%22%39%25%3
710
16th to endNight
15%25%36%27%3
540
May1st to 15thNight
25%14%44%29%4
540
16th to endNight
1313%39%37%4
563
June1st to 15thNight
2112%43%36%3
540
16th to endNight
15%34%51%6%
540
July1st to 15thNight
2322%61%10%
510
16th to endNight
2216%60%17%
564
August1st to 15thNight
1217%62%15%
539
16th to endNight
1217%58%18%
645
September1st to 15thNight
36%25%53%11%
720
16th to endNight
219%34%43%8%
716
October1st to 15thNight
3311%41%37%3
720
16th to endNight
1110%35%40%9%
768
November1st to 15thNight
3113%44%32%6%
760
16th to endNight
4315%37%33%5%
780
December1st to 15thNight
7%414%41%30%1
780
16th to endNight
9%316%43%22%3
832
Page generated at 2018-02-13 18:46:05. Version ac04

Copyright 2018 A. Danko


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