Lookout Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lookout Ranch clear sky chart from 2005-11-05 to 2017-09-23.

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
56%
15316
25%
46997
21%
15278
61%
15278
31%
27599

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
50%
717
14%
2354
13%
716
52%
716
19%
1575
January16th to endNight
52%
768
24%
2496
25%
768
55%
768
22%
1641
February1st to 15thNight
44%
700
20%
2288
19%
700
49%
700
18%
1556
February16th to endNight
40%
632
18%
1940
14%
632
47%
632
19%
1335
March1st to 15thNight
41%
720
12%
1980
10%
720
44%
720
19%
1454
March16th to endNight
39%
768
17%
2112
11%
768
44%
768
21%
1462
April1st to 15thNight
35%
719
18%
1817
8%
719
41%
719
22%
1280
April16th to endNight
46%
690
23%
1770
10%
690
52%
690
35%
1061
May1st to 15thNight
52%
539
28%
1619
17%
539
60%
539
40%
838
May16th to endNight
52%
434
24%
1556
17%
433
62%
433
30%
816
June1st to 15thNight
48%
360
23%
1440
20%
360
61%
360
30%
712
June16th to endNight
65%
360
34%
1440
37%
360
76%
360
55%
542
July1st to 15thNight
81%
417
32%
1437
33%
417
86%
417
72%
509
July16th to endNight
82%
564
37%
1593
33%
531
85%
531
63%
688
August1st to 15thNight
85%
538
38%
1611
30%
535
88%
535
67%
673
August16th to endNight
80%
710
42%
1856
28%
710
83%
710
67%
872
September1st to 15thNight
81%
720
41%
1800
27%
720
84%
720
70%
856
September16th to endNight
72%
688
38%
1917
31%
688
79%
688
56%
936
October1st to 15thNight
65%
660
28%
1980
27%
660
71%
660
40%
1066
October16th to endNight
63%
704
31%
2112
32%
704
68%
704
35%
1219
November1st to 15thNight
54%
700
22%
2151
19%
700
59%
700
24%
1373
November16th to endNight
50%
720
18%
2520
19%
720
54%
720
22%
1574
December1st to 15thNight
45%
720
18%
2520
18%
720
50%
720
19%
1677
December16th to endNight
38%
768
18%
2688
16%
768
43%
768
15%
1884

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
11%5%23323346%53%
47908
Night
12%5%24323346%49%
47187
TransparencyDay
31%37%20%22%13%
47599
Night
33%47%18%21%13%
46998
SeeingDay
16%13%28%24%12%3
6082
Night
15%8%13%28%26%8%
15324

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
18%7%46%5%33335%37%
1581
16th to endDay
22%7%24433345%39%
1728
February1st to 15thDay
23%7%3442245%5%35%
1576
16th to endDay
22%8%35%324446%33%
1532
March1st to 15thDay
24%9%45%424436%30%
1980
16th to endDay
21%7%35%434347%33%
2112
April1st to 15thDay
18%8%45%5%3445%7%33%
2131
16th to endDay
12%5%2332345%8%46%
2189
May1st to 15thDay
7%41222246%8%56%
2331
16th to endDay
9%6%24413337%51%
2555
June1st to 15thDay
8%5%24313437%56%
2520
16th to endDay
421212226%72%
2520
July1st to 15thDay
1112225%78%
2433
16th to endDay
1111111226%77%
2468
August1st to 15thDay
112111236%76%
2340
16th to endDay
11112226%78%
2345
September1st to 15thDay
121212236%75%
2160
16th to endDay
4212211246%69%
1876
October1st to 15thDay
11%413223336%57%
1650
16th to endDay
12%5%24323348%48%
1760
November1st to 15thDay
12%6%25%43445%8%42%
1705
16th to endDay
18%6%36%424335%41%
1440
December1st to 15thDay
24%8%35%424346%33%
1440
16th to endDay
28%7%3432335%5%30%
1536
January1st to 15thNight
17%7%26%435%5%5%7%34%
2354
16th to endNight
20%8%24323346%39%
2496
February1st to 15thNight
22%6%25%4345%45%35%
2276
16th to endNight
19%8%35%42345%7%33%
1940
March1st to 15thNight
22%8%36%425%35%7%30%
1980
16th to endNight
20%6%26%334446%37%
2112
April1st to 15thNight
15%7%36%5%3445%8%36%
1817
16th to endNight
10%5%1432435%7%51%
1770
May1st to 15thNight
5%4233134410%56%
1619
16th to endNight
47%24324448%52%
1555
June1st to 15thNight
6%5%2442435%7%54%
1440
16th to endNight
321212345%73%
1440
July1st to 15thNight
1112236%78%
1523
16th to endNight
112213236%72%
1701
August1st to 15thNight
11213346%73%
1620
16th to endNight
1211212235%75%
1856
September1st to 15thNight
121211236%76%
1800
16th to endNight
412223337%67%
1917
October1st to 15thNight
7%41331433460%
1980
16th to endNight
11%5%1332346%7%48%
2112
November1st to 15thNight
14%424435%6%6%7%40%
2151
16th to endNight
17%6%25%433446%41%
2520
December1st to 15thNight
22%7%25%5%23347%35%
2520
16th to endNight
24%8%35%423336%32%
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
49%49%15%11%9%
1581
16th to endDay
47%35%13%17%12%
1728
February1st to 15thDay
50%36%17%19%3
1576
16th to endDay
50%5%10%20%10%3
1532
March1st to 15thDay
56%39%13%15%2
1980
16th to endDay
50%411%17%12%2
2112
April1st to 15thDay
48%5%11%23%10%
2131
16th to endDay
34%314%24%17%4
2189
May1st to 15thDay
23%310%32%22%6%
2331
16th to endDay
31%5%9%32%16%4
2559
June1st to 15thDay
28%49%21%25%10%
2520
16th to endDay
14%2319%39%20%
2520
July1st to 15thDay
8%3213%38%33%
2291
16th to endDay
9%2310%30%43%
2313
August1st to 15thDay
9%3222%32%29%
2324
16th to endDay
8%3418%38%27%
2345
September1st to 15thDay
11%2318%32%31%
2160
16th to endDay
16%25%25%30%19%
1876
October1st to 15thDay
28%3425%25%12%
1650
16th to endDay
33%38%25%19%10%
1760
November1st to 15thDay
38%5%11%25%10%8%
1705
16th to endDay
45%5%8%16%18%5%
1440
December1st to 15thDay
51%5%7%16%15%3
1440
16th to endDay
54%47%14%14%4
1536
January1st to 15thNight
46%6%11%14%12%9%
2354
16th to endNight
45%46%14%16%12%
2496
February1st to 15thNight
49%48%16%15%5%
2288
16th to endNight
47%5%9%20%13%2
1940
March1st to 15thNight
52%5%10%13%14%3
1980
16th to endNight
45%6%12%17%14%2
2112
April1st to 15thNight
45%5%13%21%12%1
1817
16th to endNight
31%312%28%18%5%
1770
May1st to 15thNight
23%5%8%28%27%7%
1620
16th to endNight
28%5%9%32%17%6%
1556
June1st to 15thNight
26%5%9%21%22%13%
1440
16th to endNight
12%35%17%37%22%
1440
July1st to 15thNight
6%2110%39%39%
1437
16th to endNight
11%437%26%46%
1593
August1st to 15thNight
8%4217%32%34%
1611
16th to endNight
11%3314%33%33%
1856
September1st to 15thNight
9%3213%35%36%
1800
16th to endNight
15%45%21%29%23%
1917
October1st to 15thNight
27%35%21%28%14%
1980
16th to endNight
31%45%23%23%11%
2112
November1st to 15thNight
39%7%14%19%12%7%
2151
16th to endNight
41%5%9%19%17%5%
2520
December1st to 15thNight
48%47%18%15%4
2520
16th to endNight
53%46%14%16%5%
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
31%16%18%19%12%1
210
16th to endDay
29%12%21%19%13%3
256
February1st to 15thDay
31%12%22%22%10%1
236
16th to endDay
28%21%24%18%6%1
225
March1st to 15thDay
37%17%21%14%7%1
270
16th to endDay
27%27%27%11%41
288
April1st to 15thDay
24%23%28%15%6%1
269
16th to endDay
26%23%26%16%5%1
270
May1st to 15thDay
15%23%32%20%5%3
288
16th to endDay
19%15%25%20%14%4
330
June1st to 15thDay
15%12%39%23%7%2
315
16th to endDay
5%9%42%27%10%3
315
July1st to 15thDay
36%28%40%16%5%
305
16th to endDay
1230%42%17%6%
327
August1st to 15thDay
35%33%33%18%5%
315
16th to endDay
5%29%35%20%7%
332
September1st to 15thDay
36%27%37%16%7%
315
16th to endDay
10%8%31%24%16%7%
284
October1st to 15thDay
13%9%29%23%16%7%
255
16th to endDay
17%14%27%22%16%1
272
November1st to 15thDay
14%14%24%23%20%2
221
16th to endDay
16%16%38%13%8%6%
60
December1st to 15thDay
45%15%23%13%3
60
16th to endDay
32%12%17%15%15%6%
64
January1st to 15thNight
19%7%12%28%23%8%
720
16th to endNight
24%7%9%25%24%8%
768
February1st to 15thNight
24%9%11%24%23%5%
704
16th to endNight
23%11%15%24%19%5%
632
March1st to 15thNight
24%10%12%27%19%5%
720
16th to endNight
24%10%19%26%16%3
768
April1st to 15thNight
20%13%18%25%15%6%
719
16th to endNight
14%14%20%25%18%6%
690
May1st to 15thNight
7%11%23%30%21%7%
540
16th to endNight
8%11%20%30%23%5%
434
June1st to 15thNight
8%10%24%33%21%2
360
16th to endNight
4224%43%23%1
360
July1st to 15thNight
2112%32%38%12%
417
16th to endNight
217%32%39%16%
564
August1st to 15thNight
17%34%41%14%
538
16th to endNight
219%29%45%10%
710
September1st to 15thNight
248%27%39%16%
720
16th to endNight
6%5%11%30%32%13%
688
October1st to 15thNight
9%7%10%29%29%13%
660
16th to endNight
14%5%7%25%31%14%
704
November1st to 15thNight
16%9%11%27%27%8%
700
16th to endNight
19%10%10%28%22%9%
720
December1st to 15thNight
26%7%11%25%19%9%
720
16th to endNight
28%11%12%24%17%4
768
Page generated at 2017-09-24 06:15:56. Version ac04

Copyright 2017 A. Danko


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