Colorado National Monument
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Colorado National Monument clear sky chart from 2005-11-05 to 2017-09-17.

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
69%
15853
25%
46935
22%
15817
72%
15817
40%
26096

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
71%
740
20%
2351
21%
740
73%
740
36%
1320
January16th to endNight
66%
768
23%
2496
25%
768
68%
768
32%
1456
February1st to 15thNight
66%
699
16%
2288
18%
699
68%
699
31%
1359
February16th to endNight
59%
632
25%
1941
22%
632
64%
632
34%
1135
March1st to 15thNight
66%
720
27%
1980
22%
720
70%
720
43%
1112
March16th to endNight
62%
768
24%
2112
19%
768
66%
768
37%
1278
April1st to 15thNight
55%
561
22%
1820
18%
561
61%
561
33%
1026
April16th to endNight
57%
540
25%
1758
20%
540
64%
540
33%
963
May1st to 15thNight
62%
539
23%
1620
19%
539
65%
539
37%
920
May16th to endNight
65%
561
24%
1563
18%
561
70%
561
41%
885
June1st to 15thNight
71%
540
27%
1440
23%
540
73%
540
59%
721
June16th to endNight
82%
540
33%
1440
30%
540
84%
540
65%
691
July1st to 15thNight
82%
510
19%
1442
18%
510
83%
510
44%
788
July16th to endNight
85%
564
24%
1593
23%
531
86%
531
45%
848
August1st to 15thNight
80%
539
24%
1611
23%
536
80%
536
44%
866
August16th to endNight
82%
573
32%
1847
33%
573
82%
573
45%
928
September1st to 15thNight
79%
540
32%
1800
35%
540
82%
540
45%
880
September16th to endNight
80%
659
37%
1856
32%
659
82%
659
59%
912
October1st to 15thNight
71%
660
32%
1980
25%
660
75%
660
48%
996
October16th to endNight
73%
704
34%
2112
27%
704
76%
704
47%
1071
November1st to 15thNight
71%
736
31%
2157
26%
736
74%
736
45%
1133
November16th to endNight
68%
900
28%
2520
23%
900
71%
900
48%
1346
December1st to 15thNight
62%
900
16%
2520
13%
900
64%
900
33%
1567
December16th to endNight
56%
960
13%
2688
11%
960
57%
960
23%
1895

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
331342445%8%57%
47836
Night
341342445%8%56%
47126
TransparencyDay
24%6%12%22%21%12%
47528
Night
25%6%13%22%20%11%
46935
SeeingDay
48%21%32%25%7%
5679
Night
5%216%43%29%3
15865

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
2415%5%35%5%6%9%51%
1596
16th to endDay
4424424347%55%
1728
February1st to 15thDay
35%25%6%35%5%5%7%48%
1575
16th to endDay
36%25%5%25%5%5%7%50%
1530
March1st to 15thDay
25%23325%45%7%56%
1980
16th to endDay
2424435%5%6%7%53%
2112
April1st to 15thDay
3414425%5%6%8%52%
2126
16th to endDay
33135%25%5%6%8%53%
2200
May1st to 15thDay
43145%35%6%7%8%50%
2331
16th to endDay
33123245%6%9%55%
2548
June1st to 15thDay
2112323346%67%
2520
16th to endDay
111112246%75%
2520
July1st to 15thDay
2213435%47%9%54%
2428
16th to endDay
3212436%5%7%12%49%
2467
August1st to 15thDay
3314435%6%7%7%52%
2340
16th to endDay
21123245%5%8%61%
2354
September1st to 15thDay
321332346%7%61%
2160
16th to endDay
312223245%70%
1806
October1st to 15thDay
5%212224347%64%
1650
16th to endDay
3313322247%65%
1760
November1st to 15thDay
3312313347%64%
1689
16th to endDay
331332235%7%61%
1440
December1st to 15thDay
36%26%6%4445%6%48%
1440
16th to endDay
38%46%6%36%5%5%9%40%
1536
January1st to 15thNight
241443445%8%55%
2351
16th to endNight
47%2443435%9%50%
2496
February1st to 15thNight
15%26%435%45%9%50%
2277
16th to endNight
36%24425%5%7%8%49%
1941
March1st to 15thNight
2422335%5%5%7%57%
1980
16th to endNight
3425%5%36%5%6%7%50%
2112
April1st to 15thNight
44236%45%6%5%8%49%
1820
16th to endNight
5%42443345%8%52%
1758
May1st to 15thNight
5%413435%46%9%51%
1619
16th to endNight
3313426%5%5%7%56%
1562
June1st to 15thNight
2212313348%67%
1440
16th to endNight
12121335%7%71%
1440
July1st to 15thNight
3213435%5%6%11%53%
1529
16th to endNight
2213325%7%9%13%48%
1701
August1st to 15thNight
321343447%8%56%
1620
16th to endNight
22133245%5%9%58%
1847
September1st to 15thNight
321333446%6%61%
1800
16th to endNight
212213335%71%
1856
October1st to 15thNight
43231345%5%65%
1980
16th to endNight
4312313347%63%
2112
November1st to 15thNight
2313414346%62%
2157
16th to endNight
3313313346%63%
2520
December1st to 15thNight
37%35%5%24346%51%
2520
16th to endNight
48%47%6%45%5%6%8%38%
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
26%11%25%29%6%
1597
16th to endDay
29%7%22%28%11%1
1728
February1st to 15thDay
33%8%22%22%10%1
1575
16th to endDay
32%8%13%30%13%2
1530
March1st to 15thDay
27%414%30%17%4
1980
16th to endDay
27%6%11%30%18%5%
2112
April1st to 15thDay
27%7%11%23%21%8%
2126
16th to endDay
25%5%12%25%23%7%
2200
May1st to 15thDay
28%7%9%19%25%9%
2331
16th to endDay
22%6%11%20%29%10%
2551
June1st to 15thDay
18%36%13%27%31%
2520
16th to endDay
10%248%27%47%
2520
July1st to 15thDay
24%6%11%14%16%28%
2286
16th to endDay
24%7%13%20%17%17%
2312
August1st to 15thDay
27%7%12%17%15%20%
2325
16th to endDay
19%5%9%21%25%18%
2354
September1st to 15thDay
20%6%8%16%23%23%
2160
16th to endDay
16%37%19%37%14%
1806
October1st to 15thDay
21%5%10%26%29%7%
1650
16th to endDay
19%49%31%31%3
1760
November1st to 15thDay
21%412%28%27%6%
1689
16th to endDay
21%417%34%20%1
1440
December1st to 15thDay
35%8%21%28%5%
1440
16th to endDay
39%10%24%20%4
1536
January1st to 15thNight
26%9%23%29%9%
2351
16th to endNight
30%8%19%27%11%1
2496
February1st to 15thNight
30%9%21%25%11%1
2288
16th to endNight
30%8%14%28%17%1
1941
March1st to 15thNight
25%5%13%30%20%3
1980
16th to endNight
30%7%10%22%23%4
2112
April1st to 15thNight
30%6%10%19%20%11%
1820
16th to endNight
29%5%10%20%24%8%
1758
May1st to 15thNight
28%7%13%16%27%7%
1620
16th to endNight
25%7%10%19%26%11%
1563
June1st to 15thNight
16%39%14%24%32%
1440
16th to endNight
13%35%9%20%48%
1440
July1st to 15thNight
23%6%10%12%17%28%
1442
16th to endNight
21%7%14%21%17%17%
1593
August1st to 15thNight
24%5%11%20%17%20%
1611
16th to endNight
20%6%10%17%20%23%
1847
September1st to 15thNight
21%5%9%15%19%28%
1800
16th to endNight
15%37%20%28%23%
1856
October1st to 15thNight
20%48%22%30%12%
1980
16th to endNight
20%5%7%24%33%7%
2112
November1st to 15thNight
22%5%10%25%26%7%
2157
16th to endNight
21%6%12%31%24%4
2520
December1st to 15thNight
33%7%19%26%13%
2520
16th to endNight
41%13%18%22%4
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
17%216%25%26%11%
90
16th to endDay
8%216%38%23%10%
96
February1st to 15thDay
8%111%43%33%2
90
16th to endDay
7%13%22%34%14%8%
113
March1st to 15thDay
6%12%30%29%17%3
270
16th to endDay
6%21%31%29%10%1
288
April1st to 15thDay
5%23%31%19%13%5%
269
16th to endDay
8%21%32%24%10%2
270
May1st to 15thDay
313%35%27%16%3
288
16th to endDay
5%10%23%28%24%7%
449
June1st to 15thDay
37%23%29%28%7%
495
16th to endDay
2217%35%33%8%
495
July1st to 15thDay
2215%28%35%14%
390
16th to endDay
2111%40%33%10%
327
August1st to 15thDay
6%114%39%29%8%
315
16th to endDay
2311%31%39%11%
332
September1st to 15thDay
3423%33%23%11%
315
16th to endDay
37%17%30%32%8%
235
October1st to 15thDay
2413%30%28%21%
90
16th to endDay
6%9%8%34%32%9%
96
November1st to 15thDay
15%8%28%44%11%
90
16th to endDay
6%7%24%44%13%3
90
December1st to 15thDay
6%118%56%16%
90
16th to endDay
9%6%12%45%21%4
96
January1st to 15thNight
4215%45%26%5%
744
16th to endNight
7%216%43%23%6%
768
February1st to 15thNight
3117%51%21%3
704
16th to endNight
5%223%52%13%1
632
March1st to 15thNight
4319%47%22%1
720
16th to endNight
4420%49%19%
768
April1st to 15thNight
5%7%25%43%16%
561
16th to endNight
6%7%25%37%21%2
540
May1st to 15thNight
7%321%45%20%2
540
16th to endNight
5%6%18%36%31%2
563
June1st to 15thNight
2220%44%27%2
540
16th to endNight
2110%47%35%2
540
July1st to 15thNight
37%36%48%3
510
16th to endNight
2331%55%6%
564
August1st to 15thNight
45%35%50%2
539
16th to endNight
27%32%50%6%
573
September1st to 15thNight
39%42%40%4
540
16th to endNight
3110%30%45%8%
659
October1st to 15thNight
5%115%42%30%4
660
16th to endNight
6%213%37%34%5%
704
November1st to 15thNight
3215%44%31%2
736
16th to endNight
5%318%45%23%4
900
December1st to 15thNight
7%218%51%18%1
900
16th to endNight
6%5%19%45%19%2
960
Page generated at 2017-09-18 06:38:19. Version ac04

Copyright 2017 A. Danko


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