Little Colorado River Valley Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Little Colorado River Valley Observatory clear sky chart from 2005-11-05 to 2017-12-02.

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
64%
15693
33%
47795
25%
15652
72%
15652
48%
23668

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%
720
31%
2327
30%
716
73%
716
45%
1139
January16th to endNight
63%
768
34%
2496
31%
768
71%
768
44%
1248
February1st to 15thNight
61%
700
31%
2288
29%
700
69%
700
49%
1075
February16th to endNight
51%
632
40%
1824
25%
632
67%
632
50%
903
March1st to 15thNight
56%
720
37%
1980
24%
720
66%
720
52%
988
March16th to endNight
58%
768
37%
2112
21%
768
71%
768
58%
1015
April1st to 15thNight
46%
617
34%
1876
16%
617
64%
617
50%
876
April16th to endNight
49%
540
36%
1800
22%
540
68%
540
52%
775
May1st to 15thNight
55%
539
34%
1631
21%
539
67%
539
54%
751
May16th to endNight
60%
562
33%
1684
22%
561
70%
561
59%
744
June1st to 15thNight
67%
540
32%
1620
26%
540
72%
540
64%
705
June16th to endNight
75%
540
29%
1620
26%
540
77%
540
58%
735
July1st to 15thNight
70%
510
17%
1530
15%
510
70%
510
30%
927
July16th to endNight
71%
564
13%
1593
11%
531
71%
531
23%
1050
August1st to 15thNight
77%
539
18%
1611
17%
536
77%
536
28%
998
August16th to endNight
76%
573
22%
1874
22%
573
77%
573
28%
1143
September1st to 15thNight
74%
621
26%
1881
23%
621
77%
621
35%
1097
September16th to endNight
76%
716
40%
1980
28%
716
83%
716
62%
946
October1st to 15thNight
70%
720
38%
2145
26%
720
78%
720
64%
931
October16th to endNight
76%
768
43%
2304
33%
768
84%
768
63%
1011
November1st to 15thNight
70%
760
39%
2280
30%
760
77%
760
60%
1030
November16th to endNight
66%
780
41%
2477
35%
780
73%
780
54%
1107
December1st to 15thNight
62%
728
35%
2366
30%
728
71%
728
46%
1134
December16th to endNight
53%
768
31%
2496
25%
768
63%
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
2313424446%61%
48652
Night
2313323446%63%
47991
TransparencyDay
22%48%16%27%19%
48347
Night
19%49%18%28%18%
47797
SeeingDay
6%9%22%29%21%10%
5501
Night
4421%38%26%4
15699

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
131442446%5%62%
1611
16th to endDay
3413223346%63%
1728
February1st to 15thDay
15%23213236%65%
1575
16th to endDay
25%15%423346%59%
1650
March1st to 15thDay
2413323446%63%
1980
16th to endDay
2212213347%66%
2112
April1st to 15thDay
1212313446%67%
2071
16th to endDay
2212312235%71%
2160
May1st to 15thDay
1213322347%66%
2316
16th to endDay
221332333468%
2429
June1st to 15thDay
111212335%75%
2340
16th to endDay
112224436%69%
2340
July1st to 15thDay
3225%7%47%6%7%9%42%
2340
16th to endDay
5%326%8%6%9%9%10%10%27%
2467
August1st to 15thDay
6%426%8%36%8%8%8%36%
2340
16th to endDay
43245%47%8%8%8%41%
2327
September1st to 15thDay
4325%5%36%6%5%8%47%
2076
16th to endDay
222222235%71%
1980
October1st to 15thDay
31121223474%
1813
16th to endDay
2212112335%74%
1920
November1st to 15thDay
122312235%72%
1909
16th to endDay
2212422235%70%
1810
December1st to 15thDay
2423323347%62%
1630
16th to endDay
35%34423436%59%
1728
January1st to 15thNight
1313324445%64%
2327
16th to endNight
341332335%5%63%
2496
February1st to 15thNight
1413313336%66%
2277
16th to endNight
1213324447%63%
1824
March1st to 15thNight
2313223345%68%
1980
16th to endNight
2212213346%69%
2112
April1st to 15thNight
2312212346%67%
1876
16th to endNight
1212212345%71%
1800
May1st to 15thNight
2112323336%69%
1631
16th to endNight
121221323474%
1684
June1st to 15thNight
211112245%74%
1620
16th to endNight
1112214446%69%
1620
July1st to 15thNight
4315%5%46%5%9%10%43%
1620
16th to endNight
43247%5%8%8%10%12%32%
1701
August1st to 15thNight
3326%446%6%10%10%41%
1620
16th to endNight
43146%47%8%7%10%41%
1874
September1st to 15thNight
3325%5%35%6%6%8%49%
1881
16th to endNight
212312345%71%
1980
October1st to 15thNight
211212235%76%
2145
16th to endNight
11221232476%
2304
November1st to 15thNight
1112313245%72%
2280
16th to endNight
232212236%71%
2477
December1st to 15thNight
3314313346%64%
2366
16th to endNight
5%5%24424447%55%
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
21%6%8%25%30%7%
1612
16th to endDay
21%39%20%34%10%
1728
February1st to 15thDay
20%28%25%25%17%
1575
16th to endDay
23%45%20%31%14%
1650
March1st to 15thDay
19%36%14%37%17%
1980
16th to endDay
17%36%16%38%17%
2112
April1st to 15thDay
16%36%17%35%21%
2071
16th to endDay
16%2414%34%26%
2160
May1st to 15thDay
18%26%14%29%27%
2316
16th to endDay
20%35%10%30%29%
2432
June1st to 15thDay
11%149%24%47%
2340
16th to endDay
16%349%22%43%
2340
July1st to 15thDay
33%8%15%14%10%17%
2201
16th to endDay
42%14%18%16%6%1
2312
August1st to 15thDay
39%11%12%13%13%9%
2325
16th to endDay
34%10%11%15%19%8%
2327
September1st to 15thDay
32%7%10%16%19%11%
2076
16th to endDay
16%27%15%29%28%
1980
October1st to 15thDay
14%35%15%34%26%
1813
16th to endDay
13%26%13%38%24%
1920
November1st to 15thDay
14%25%22%36%18%
1909
16th to endDay
17%2419%33%22%
1810
December1st to 15thDay
20%49%27%28%9%
1630
16th to endDay
25%413%25%26%4
1728
January1st to 15thNight
21%48%24%33%8%
2327
16th to endNight
22%48%22%33%8%
2496
February1st to 15thNight
19%39%24%24%17%
2288
16th to endNight
18%46%25%32%12%
1824
March1st to 15thNight
18%36%16%39%16%
1980
16th to endNight
15%37%18%39%16%
2112
April1st to 15thNight
17%26%19%34%18%
1876
16th to endNight
15%36%14%36%23%
1800
May1st to 15thNight
15%47%17%29%25%
1632
16th to endNight
14%27%13%34%27%
1685
June1st to 15thNight
12%248%21%50%
1620
16th to endNight
15%35%11%19%44%
1620
July1st to 15thNight
30%10%14%15%10%17%
1530
16th to endNight
37%13%24%17%6%1
1593
August1st to 15thNight
31%12%16%15%13%10%
1611
16th to endNight
32%11%16%15%15%8%
1874
September1st to 15thNight
28%9%15%15%19%11%
1881
16th to endNight
14%36%17%29%28%
1980
October1st to 15thNight
11%26%19%31%28%
2145
16th to endNight
12%25%15%34%28%
2304
November1st to 15thNight
14%36%23%35%17%
2280
16th to endNight
16%36%18%31%23%
2477
December1st to 15thNight
21%38%25%29%11%
2366
16th to endNight
27%5%12%25%25%4
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
5%14%30%30%13%6%
90
16th to endDay
8%12%18%29%16%14%
96
February1st to 15thDay
3416%33%33%8%
90
16th to endDay
9%26%25%19%12%5%
219
March1st to 15thDay
8%14%30%25%14%6%
270
16th to endDay
6%20%32%23%11%4
288
April1st to 15thDay
6%21%31%18%16%5%
269
16th to endDay
8%22%36%19%11%1
270
May1st to 15thDay
314%36%27%13%4
288
16th to endDay
6%12%30%29%15%4
330
June1st to 15thDay
37%28%30%20%8%
315
16th to endDay
1317%36%27%12%
315
July1st to 15thDay
5%112%38%28%13%
305
16th to endDay
9%18%29%25%26%
327
August1st to 15thDay
8%9%26%39%15%
315
16th to endDay
4210%32%33%17%
332
September1st to 15thDay
10%18%34%24%11%
315
16th to endDay
6%5%24%32%24%6%
315
October1st to 15thDay
15%19%34%28%10%
148
16th to endDay
4215%25%28%23%
144
November1st to 15thDay
5%9%17%33%22%11%
135
16th to endDay
5%13%15%33%23%8%
135
December1st to 15thDay
6%10%19%35%19%9%
94
16th to endDay
10%16%14%42%12%3
96
January1st to 15thNight
45%17%43%22%6%
720
16th to endNight
6%5%21%39%21%5%
768
February1st to 15thNight
45%24%42%20%3
704
16th to endNight
29%33%40%11%
632
March1st to 15thNight
49%27%36%19%2
720
16th to endNight
26%30%42%16%2
768
April1st to 15thNight
211%35%36%12%1
617
16th to endNight
39%35%35%15%1
540
May1st to 15thNight
3432%44%13%1
540
16th to endNight
2329%42%19%1
563
June1st to 15thNight
2324%50%19%
540
16th to endNight
2116%47%32%
540
July1st to 15thNight
6%9%42%38%2
510
16th to endNight
7%6%26%48%10%
564
August1st to 15thNight
6%425%52%10%
539
16th to endNight
5%8%29%47%7%
573
September1st to 15thNight
410%32%48%4
621
16th to endNight
2113%39%37%5%
716
October1st to 15thNight
2222%43%25%4
720
16th to endNight
2214%39%36%5%
768
November1st to 15thNight
2321%39%30%3
760
16th to endNight
45%20%36%26%6%
780
December1st to 15thNight
6%6%19%38%24%3
728
16th to endNight
7%5%26%37%17%4
768
Page generated at 2017-12-03 09:16:37. Version ac04

Copyright 2017 A. Danko


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