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 2017-03-24.

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%
14842
32%
45219
25%
14801
72%
14801
47%
22428

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%
740
36%
2035
21%
740
70%
740
59%
977
April1st to 15thNight
44%
566
35%
1720
17%
566
64%
566
49%
814
April16th to endNight
49%
495
34%
1650
21%
495
67%
495
51%
717
May1st to 15thNight
54%
494
35%
1495
22%
494
68%
494
54%
691
May16th to endNight
61%
514
31%
1540
21%
513
70%
513
59%
680
June1st to 15thNight
67%
495
34%
1485
27%
495
71%
495
64%
645
June16th to endNight
75%
495
27%
1485
24%
495
77%
495
57%
677
July1st to 15thNight
70%
465
17%
1395
15%
465
71%
465
31%
843
July16th to endNight
71%
522
13%
1467
12%
489
71%
489
23%
960
August1st to 15thNight
77%
494
19%
1476
18%
491
77%
491
28%
915
August16th to endNight
77%
525
20%
1717
20%
525
78%
525
28%
1054
September1st to 15thNight
75%
569
28%
1724
24%
569
78%
569
36%
1002
September16th to endNight
77%
656
38%
1815
27%
656
83%
656
61%
872
October1st to 15thNight
71%
660
39%
1966
27%
660
78%
660
62%
871
October16th to endNight
76%
704
40%
2112
31%
704
83%
704
62%
937
November1st to 15thNight
71%
700
40%
2100
31%
700
79%
700
61%
935
November16th to endNight
65%
720
39%
2286
33%
720
72%
720
53%
1031
December1st to 15thNight
62%
720
35%
2340
31%
720
72%
720
47%
1114
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
231342445%6%60%
45712
Night
2313323446%63%
45415
TransparencyDay
22%5%8%16%27%19%
45407
Night
20%49%19%28%18%
45221
SeeingDay
6%10%22%30%21%8%
4561
Night
4421%39%26%4
14848

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%
2033
April1st to 15thDay
121331345%6%67%
1897
16th to endDay
2212313235%71%
1980
May1st to 15thDay
121332235%7%66%
2122
16th to endDay
3213322335%67%
2221
June1st to 15thDay
11121233476%
2145
16th to endDay
112324436%68%
2145
July1st to 15thDay
3225%7%47%6%7%9%41%
2145
16th to endDay
5%326%8%6%8%9%10%10%27%
2285
August1st to 15thDay
6%426%8%46%8%8%8%35%
2145
16th to endDay
43245%47%8%8%9%40%
2132
September1st to 15thDay
5%325%5%36%6%5%8%47%
1903
16th to endDay
222223335%69%
1815
October1st to 15thDay
311221233472%
1662
16th to endDay
2212112325%73%
1760
November1st to 15thDay
212312235%73%
1759
16th to endDay
2212422235%71%
1671
December1st to 15thDay
2323323347%63%
1620
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%
2035
April1st to 15thNight
2322322347%65%
1720
16th to endNight
1212313345%70%
1650
May1st to 15thNight
2112323336%69%
1495
16th to endNight
1212213235%74%
1540
June1st to 15thNight
21111224475%
1485
16th to endNight
1112214446%69%
1485
July1st to 15thNight
4315%5%45%5%9%10%43%
1485
16th to endNight
44247%5%8%9%9%11%32%
1575
August1st to 15thNight
3326%446%7%10%10%40%
1485
16th to endNight
42146%47%8%7%11%40%
1717
September1st to 15thNight
2325%435%6%6%8%50%
1724
16th to endNight
212312345%70%
1815
October1st to 15thNight
211212235%74%
1966
16th to endNight
11221232475%
2112
November1st to 15thNight
1112313245%73%
2100
16th to endNight
3312212236%70%
2286
December1st to 15thNight
3314313346%64%
2340
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%15%38%18%
2033
April1st to 15thDay
17%36%17%34%21%
1897
16th to endDay
17%2414%35%25%
1980
May1st to 15thDay
17%36%15%29%27%
2122
16th to endDay
20%35%11%30%29%
2224
June1st to 15thDay
11%148%24%48%
2145
16th to endDay
17%349%23%41%
2145
July1st to 15thDay
35%8%15%13%11%16%
2006
16th to endDay
41%14%17%17%7%1
2130
August1st to 15thDay
40%11%12%12%13%8%
2130
16th to endDay
35%10%12%16%17%7%
2132
September1st to 15thDay
32%8%11%17%18%12%
1903
16th to endDay
17%27%15%28%28%
1815
October1st to 15thDay
15%36%15%33%25%
1662
16th to endDay
14%36%13%38%23%
1760
November1st to 15thDay
13%26%22%36%18%
1759
16th to endDay
17%2420%32%22%
1671
December1st to 15thDay
19%5%9%27%28%9%
1620
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%
2035
April1st to 15thNight
18%36%20%34%17%
1720
16th to endNight
15%37%14%36%22%
1650
May1st to 15thNight
15%47%18%28%25%
1496
16th to endNight
14%28%13%34%27%
1541
June1st to 15thNight
12%238%20%52%
1485
16th to endNight
15%35%10%19%44%
1485
July1st to 15thNight
30%10%14%15%11%16%
1395
16th to endNight
37%12%23%18%6%1
1467
August1st to 15thNight
32%11%15%16%13%9%
1476
16th to endNight
32%11%18%16%13%8%
1717
September1st to 15thNight
27%9%15%15%19%12%
1724
16th to endNight
14%36%17%28%28%
1815
October1st to 15thNight
12%36%21%31%25%
1966
16th to endNight
12%36%15%34%27%
2112
November1st to 15thNight
13%36%23%36%18%
2100
16th to endNight
16%36%18%30%23%
2286
December1st to 15thNight
20%38%25%29%11%
2340
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%31%23%11%5%
260
April1st to 15thDay
8%24%32%17%13%3
209
16th to endDay
7%23%37%19%11%
210
May1st to 15thDay
414%39%28%10%3
228
16th to endDay
7%12%30%29%15%4
266
June1st to 15thDay
38%32%30%16%8%
255
16th to endDay
2320%38%23%10%
255
July1st to 15thDay
6%213%43%28%6%
245
16th to endDay
8%19%31%25%22%
271
August1st to 15thDay
8%10%25%37%16%
255
16th to endDay
4211%34%35%11%
268
September1st to 15thDay
12%117%37%24%7%
255
16th to endDay
7%423%31%25%8%
255
October1st to 15thDay
1314%33%31%14%
102
16th to endDay
7%113%32%29%16%
96
November1st to 15thDay
6%7%14%30%24%16%
90
16th to endDay
417%20%35%21%1
90
December1st to 15thDay
5%11%18%34%20%10%
90
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
16%30%42%16%2
740
April1st to 15thNight
311%37%34%12%1
566
16th to endNight
38%35%35%15%1
495
May1st to 15thNight
3432%45%12%1
495
16th to endNight
2329%42%19%1
515
June1st to 15thNight
1325%50%17%
495
16th to endNight
2115%47%32%
495
July1st to 15thNight
6%9%42%37%2
465
16th to endNight
6%7%27%48%9%
522
August1st to 15thNight
6%424%53%10%
494
16th to endNight
48%30%48%7%
525
September1st to 15thNight
310%32%48%4
569
16th to endNight
2112%38%38%5%
656
October1st to 15thNight
2221%43%25%4
660
16th to endNight
2215%39%35%5%
704
November1st to 15thNight
2319%39%31%4
700
16th to endNight
45%21%36%25%6%
720
December1st to 15thNight
6%6%20%38%25%3
720
16th to endNight
7%5%26%37%17%4
768
Page generated at 2017-03-25 09:39:52. Version ac04

Copyright 2017 A. Danko


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