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 2017-03-19.

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
74%
15060
35%
45197
30%
15021
80%
15021
53%
21531

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
66%
719
33%
2327
29%
716
76%
716
46%
1122
January16th to endNight
61%
768
36%
2496
32%
768
71%
768
41%
1290
February1st to 15thNight
68%
698
35%
2186
30%
698
79%
698
50%
1045
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
73%
720
36%
1980
28%
720
79%
720
58%
948
April1st to 15thNight
61%
651
32%
1805
18%
651
71%
651
53%
913
April16th to endNight
66%
495
43%
1526
31%
495
76%
495
71%
598
May1st to 15thNight
74%
494
39%
1484
30%
494
80%
494
63%
634
May16th to endNight
77%
513
36%
1540
29%
513
82%
513
69%
636
June1st to 15thNight
83%
495
35%
1485
32%
495
83%
495
71%
610
June16th to endNight
88%
495
32%
1485
29%
495
88%
495
72%
604
July1st to 15thNight
85%
465
24%
1395
20%
465
85%
465
47%
715
July16th to endNight
84%
522
25%
1467
22%
489
86%
489
41%
806
August1st to 15thNight
89%
494
31%
1476
27%
491
90%
491
47%
749
August16th to endNight
86%
591
30%
1698
26%
591
86%
591
45%
930
September1st to 15thNight
83%
660
32%
1815
26%
660
85%
660
50%
963
September16th to endNight
83%
656
42%
1815
33%
656
88%
656
69%
810
October1st to 15thNight
78%
660
40%
1886
33%
660
82%
660
60%
867
October16th to endNight
80%
704
42%
2112
36%
704
86%
704
64%
917
November1st to 15thNight
78%
700
39%
2163
34%
700
85%
700
62%
941
November16th to endNight
72%
720
40%
2340
37%
720
80%
720
55%
1020
December1st to 15thNight
70%
720
35%
2340
33%
720
76%
720
45%
1128
December16th to endNight
61%
768
33%
2496
29%
768
69%
768
37%
1340

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
3212313346%66%
45619
Night
3212213346%68%
45393
TransparencyDay
18%46%15%27%27%
45314
Night
17%36%14%27%29%
45199
SeeingDay
5%10%26%35%17%4
4741
Night
4313%37%35%6%
15070

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%65%
1611
16th to endDay
6%412313346%61%
1728
February1st to 15thDay
2323323346%63%
1676
16th to endDay
4313424346%60%
1579
March1st to 15thDay
3312313346%67%
1974
16th to endDay
2212213345%69%
1974
April1st to 15thDay
212223347%67%
1811
16th to endDay
112212236%75%
2101
May1st to 15thDay
111212347%72%
2136
16th to endDay
221112235%75%
2221
June1st to 15thDay
111213382%
2145
16th to endDay
11122382%
2145
July1st to 15thDay
2212435%6%7%9%54%
2145
16th to endDay
43346%37%6%9%10%41%
2285
August1st to 15thDay
2214425%5%7%10%53%
2145
16th to endDay
42124245%6%9%54%
2148
September1st to 15thDay
32123235%5%7%59%
1815
16th to endDay
2111123479%
1815
October1st to 15thDay
11121333474%
1744
16th to endDay
112111235%77%
1760
November1st to 15thDay
2121335%5%71%
1693
16th to endDay
4211212235%73%
1620
December1st to 15thDay
4412424436%61%
1620
16th to endDay
6%5%23323347%56%
1728
January1st to 15thNight
4312224336%65%
2327
16th to endNight
7%313323335%62%
2496
February1st to 15thNight
3312212335%68%
2175
16th to endNight
6%21222336%8%61%
1895
March1st to 15thNight
3211214345%68%
1985
16th to endNight
212212446%71%
1980
April1st to 15thNight
3113212446%67%
1805
16th to endNight
11111226%81%
1526
May1st to 15thNight
111211345%74%
1484
16th to endNight
1111112481%
1540
June1st to 15thNight
11111222480%
1485
16th to endNight
11111212283%
1485
July1st to 15thNight
12133245%7%9%57%
1485
16th to endNight
1224335%6%8%12%48%
1575
August1st to 15thNight
1112325%6%7%10%57%
1485
16th to endNight
1113435%6%6%9%55%
1698
September1st to 15thNight
221242346%8%61%
1815
16th to endNight
11111222479%
1815
October1st to 15thNight
2111212246%73%
1886
16th to endNight
111212325%76%
2112
November1st to 15thNight
112212446%73%
2163
16th to endNight
321213235%73%
2340
December1st to 15thNight
4213222345%65%
2340
16th to endNight
7%413324345%58%
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
22%25%16%32%20%
1612
16th to endDay
24%35%17%30%18%
1728
February1st to 15thDay
22%36%17%27%23%
1676
16th to endDay
26%35%18%27%17%
1579
March1st to 15thDay
19%3315%35%23%
1974
16th to endDay
18%35%16%36%20%
1974
April1st to 15thDay
17%3416%33%25%
1811
16th to endDay
12%3313%34%32%
2101
May1st to 15thDay
12%35%14%30%34%
2136
16th to endDay
13%2411%32%35%
2224
June1st to 15thDay
8%126%24%56%
2145
16th to endDay
8%125%20%61%
2145
July1st to 15thDay
21%7%10%16%16%26%
2006
16th to endDay
30%11%15%18%16%6%
2130
August1st to 15thDay
23%7%11%17%19%20%
2130
16th to endDay
23%7%11%18%23%14%
2148
September1st to 15thDay
21%5%10%15%23%22%
1815
16th to endDay
10%2411%32%39%
1815
October1st to 15thDay
14%3414%27%35%
1744
16th to endDay
11%15%14%31%34%
1760
November1st to 15thDay
13%3417%32%27%
1693
16th to endDay
16%2316%28%32%
1620
December1st to 15thDay
26%48%19%24%16%
1620
16th to endDay
29%37%20%27%10%
1728
January1st to 15thNight
22%25%14%33%21%
2327
16th to endNight
26%2416%27%21%
2496
February1st to 15thNight
19%36%16%27%26%
2186
16th to endNight
22%35%18%30%19%
1895
March1st to 15thNight
17%2412%34%27%
1985
16th to endNight
14%35%16%33%25%
1980
April1st to 15thNight
19%2414%31%27%
1805
16th to endNight
8%413%34%38%
1526
May1st to 15thNight
11%3413%29%38%
1485
16th to endNight
10%1210%33%40%
1541
June1st to 15thNight
10%125%17%62%
1485
16th to endNight
9%11412%69%
1485
July1st to 15thNight
20%6%12%13%19%28%
1395
16th to endNight
23%8%14%22%20%10%
1467
August1st to 15thNight
18%8%11%18%18%24%
1476
16th to endNight
22%7%10%19%21%18%
1698
September1st to 15thNight
19%6%11%18%19%24%
1815
16th to endNight
11%228%35%39%
1815
October1st to 15thNight
14%2415%27%35%
1886
16th to endNight
12%25%10%24%44%
2112
November1st to 15thNight
14%2415%35%28%
2163
16th to endNight
16%2413%26%36%
2340
December1st to 15thNight
21%37%18%27%21%
2340
16th to endNight
29%47%19%28%12%
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
27%10%15%30%15%1
90
16th to endDay
14%9%17%31%16%10%
96
February1st to 15thDay
312%32%31%18%2
191
16th to endDay
8%23%33%22%10%1
238
March1st to 15thDay
7%17%30%25%14%5%
270
16th to endDay
321%31%30%11%1
238
April1st to 15thDay
9%22%38%22%5%2
209
16th to endDay
5%27%41%18%41
210
May1st to 15thDay
417%42%25%7%2
228
16th to endDay
6%12%37%30%10%3
266
June1st to 15thDay
210%41%30%11%3
255
16th to endDay
222%48%20%5%
255
July1st to 15thDay
3221%51%18%2
245
16th to endDay
49%48%25%11%
271
August1st to 15thDay
16%46%27%7%
255
16th to endDay
319%47%32%6%
268
September1st to 15thDay
5%323%42%21%4
255
16th to endDay
5%7%21%41%20%4
255
October1st to 15thDay
39%34%25%20%5%
184
16th to endDay
6%5%10%36%33%8%
96
November1st to 15thDay
17%14%34%32%10%
90
16th to endDay
7%8%25%35%21%1
90
December1st to 15thDay
410%12%35%37%
90
16th to endDay
12%15%16%35%18%1
96
January1st to 15thNight
5%418%43%22%5%
720
16th to endNight
9%5%19%38%24%2
768
February1st to 15thNight
5%318%45%25%2
704
16th to endNight
7%5%18%47%17%2
632
March1st to 15thNight
5%421%39%24%4
720
16th to endNight
25%15%42%30%3
720
April1st to 15thNight
45%23%39%23%3
651
16th to endNight
15%25%37%27%3
495
May1st to 15thNight
25%14%45%29%3
495
16th to endNight
1213%40%37%4
515
June1st to 15thNight
2112%45%34%4
495
16th to endNight
16%34%50%6%
495
July1st to 15thNight
2322%60%10%
465
16th to endNight
2217%61%16%
522
August1st to 15thNight
1218%62%15%
494
16th to endNight
1217%58%18%
591
September1st to 15thNight
36%25%53%10%
660
16th to endNight
219%33%44%9%
656
October1st to 15thNight
3311%40%37%3
660
16th to endNight
1111%36%40%8%
704
November1st to 15thNight
3113%42%32%6%
700
16th to endNight
5%316%37%32%5%
720
December1st to 15thNight
7%414%40%31%1
720
16th to endNight
10%317%44%20%3
768
Page generated at 2017-03-20 05:18:29. Version ac04

Copyright 2017 A. Danko


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