Lazy 8 Ranch Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lazy 8 Ranch Observatory 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%
15893
21%
47010
16%
15852
62%
15852
30%
29118

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
42%
718
21%
2327
15%
716
51%
716
25%
1439
January16th to endNight
40%
768
24%
2430
17%
768
50%
768
27%
1472
February1st to 15thNight
42%
701
25%
2104
17%
698
52%
698
32%
1247
February16th to endNight
40%
631
23%
1857
12%
631
51%
631
29%
1156
March1st to 15thNight
45%
720
30%
1980
16%
720
57%
720
40%
1130
March16th to endNight
48%
768
26%
2112
18%
768
56%
768
39%
1228
April1st to 15thNight
47%
718
25%
1976
15%
718
56%
718
42%
1114
April16th to endNight
55%
702
28%
1842
17%
702
62%
702
44%
1064
May1st to 15thNight
69%
539
25%
1619
18%
539
74%
539
45%
853
May16th to endNight
73%
561
24%
1682
19%
561
75%
561
38%
964
June1st to 15thNight
67%
540
13%
1620
12%
540
68%
540
26%
1097
June16th to endNight
72%
540
9%
1620
7%
540
73%
540
24%
1120
July1st to 15thNight
74%
510
8%
1530
8%
510
74%
510
22%
1091
July16th to endNight
76%
564
6%
1595
6%
531
77%
531
22%
1140
August1st to 15thNight
73%
539
6%
1624
6%
536
73%
536
23%
1118
August16th to endNight
67%
693
11%
2030
11%
693
67%
693
21%
1439
September1st to 15thNight
64%
720
9%
1980
8%
720
64%
720
21%
1416
September16th to endNight
59%
689
15%
1903
15%
689
61%
689
22%
1348
October1st to 15thNight
67%
660
27%
1862
25%
660
70%
660
34%
1135
October16th to endNight
58%
704
29%
2112
26%
704
65%
704
34%
1237
November1st to 15thNight
56%
700
30%
2101
24%
700
65%
700
38%
1160
November16th to endNight
47%
720
28%
2268
20%
720
59%
720
34%
1294
December1st to 15thNight
48%
720
28%
2340
24%
720
56%
720
29%
1396
December16th to endNight
51%
768
24%
2496
22%
768
58%
768
30%
1460

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
9%5%26%6%46%6%6%8%37%
47881
Night
8%425%5%35%5%6%9%44%
47218
TransparencyDay
41%7%13%16%13%6%
47582
Night
34%7%15%20%15%6%
47021
SeeingDay
9%414%21%25%24%
5749
Night
9%420%32%25%7%
15901

By Month

Percentage Cloud Cover SE (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
12%6%25%5%35%5%5%6%42%
1611
16th to endDay
10%5%25%6%2345%6%46%
1791
February1st to 15thDay
13%5%35%5%23345%45%
1750
16th to endDay
10%5%25%5%25%346%48%
1613
March1st to 15thDay
8%314425%45%7%50%
1980
16th to endDay
8%425%5%25%5%47%48%
2111
April1st to 15thDay
7%415%425%5%49%48%
1972
16th to endDay
7%3144245%6%7%50%
2127
May1st to 15thDay
6%3245%26%5%6%8%49%
2331
16th to endDay
6%425%6%46%7%7%9%39%
2431
June1st to 15thDay
10%6%36%7%5%8%7%7%9%27%
2340
16th to endDay
7%6%37%9%48%7%8%9%25%
2340
July1st to 15thDay
9%6%38%8%5%9%9%7%10%21%
2340
16th to endDay
8%7%48%9%6%9%9%8%10%18%
2465
August1st to 15thDay
8%5%38%9%6%8%8%8%12%19%
2322
16th to endDay
11%6%37%8%6%8%7%7%9%23%
2160
September1st to 15thDay
10%6%38%9%48%7%7%9%23%
1980
16th to endDay
10%8%38%9%5%6%6%6%8%25%
1894
October1st to 15thDay
10%5%26%6%35%5%5%7%40%
1768
16th to endDay
9%5%25%5%34447%48%
1760
November1st to 15thDay
7%42441445%6%53%
1757
16th to endDay
9%4245%35%446%48%
1690
December1st to 15thDay
10%6%35%5%3445%7%43%
1620
16th to endDay
8%4245%447%6%8%43%
1728
January1st to 15thNight
12%5%35%5%2445%9%40%
2327
16th to endNight
14%42342445%7%45%
2430
February1st to 15thNight
11%5%2432445%5%50%
2103
16th to endNight
8%6%25%5%33447%46%
1857
March1st to 15thNight
6%41432345%7%55%
1980
16th to endNight
8%423423347%55%
2112
April1st to 15thNight
6%31332345%8%55%
1976
16th to endNight
6%21432335%8%56%
1842
May1st to 15thNight
421442346%10%56%
1619
16th to endNight
43145%25%6%5%9%51%
1682
June1st to 15thNight
9%5%16%5%36%5%7%10%37%
1620
16th to endNight
6%426%6%5%6%6%8%12%33%
1620
July1st to 15thNight
5%5%25%6%36%8%10%13%32%
1620
16th to endNight
4337%7%49%8%9%12%30%
1703
August1st to 15thNight
5%428%6%46%7%9%14%30%
1635
16th to endNight
9%5%26%6%36%6%8%11%33%
2030
September1st to 15thNight
8%5%26%7%47%6%7%11%31%
1980
16th to endNight
9%6%36%7%46%6%7%10%30%
1903
October1st to 15thNight
6%5%244345%5%8%49%
1862
16th to endNight
8%5%2443345%6%50%
2112
November1st to 15thNight
5%4245%235%5%6%54%
2101
16th to endNight
7%425%5%2445%7%49%
2268
December1st to 15thNight
10%5%25%33445%8%46%
2340
16th to endNight
9%425%425%6%6%9%44%
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
41%47%19%17%8%
1612
16th to endDay
37%47%16%22%10%
1791
February1st to 15thDay
40%45%13%19%16%
1752
16th to endDay
37%48%15%21%12%
1613
March1st to 15thDay
32%410%22%21%8%
1980
16th to endDay
36%49%20%18%9%
2112
April1st to 15thDay
32%5%10%18%22%9%
1972
16th to endDay
30%5%11%20%22%9%
2127
May1st to 15thDay
30%6%12%22%18%9%
2331
16th to endDay
38%7%14%20%16%3
2435
June1st to 15thDay
49%9%15%19%5%
2340
16th to endDay
50%11%19%14%3
2340
July1st to 15thDay
53%12%21%10%1
2201
16th to endDay
52%14%20%10%1
2310
August1st to 15thDay
50%14%24%9%1
2309
16th to endDay
52%14%17%13%1
2160
September1st to 15thDay
53%13%16%11%5%
1980
16th to endDay
51%9%13%15%7%2
1894
October1st to 15thDay
41%6%8%16%16%11%
1768
16th to endDay
35%5%8%14%23%13%
1760
November1st to 15thDay
30%49%23%20%12%
1757
16th to endDay
36%48%18%20%13%
1690
December1st to 15thDay
39%411%19%18%5%
1620
16th to endDay
35%6%12%20%16%8%
1728
January1st to 15thNight
40%410%20%16%8%
2327
16th to endNight
38%48%16%22%9%
2430
February1st to 15thNight
34%48%17%20%15%
2112
16th to endNight
36%6%10%15%22%8%
1857
March1st to 15thNight
27%411%26%21%8%
1980
16th to endNight
29%410%24%20%10%
2112
April1st to 15thNight
25%6%13%24%22%7%
1976
16th to endNight
25%5%13%25%22%7%
1842
May1st to 15thNight
23%5%19%26%17%8%
1620
16th to endNight
27%7%17%25%19%2
1684
June1st to 15thNight
40%9%22%21%5%
1620
16th to endNight
39%12%25%18%3
1620
July1st to 15thNight
37%18%29%12%1
1530
16th to endNight
40%15%30%11%2
1595
August1st to 15thNight
36%15%35%10%
1624
16th to endNight
40%14%24%17%2
2030
September1st to 15thNight
42%13%24%14%4
1980
16th to endNight
45%9%17%17%7%2
1903
October1st to 15thNight
32%7%11%21%18%8%
1862
16th to endNight
33%48%14%27%11%
2112
November1st to 15thNight
28%410%23%22%9%
2101
16th to endNight
33%39%21%17%14%
2268
December1st to 15thNight
35%5%9%26%15%7%
2340
16th to endNight
34%5%13%22%14%9%
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
16%7%36%23%12%3
90
16th to endDay
12%17%39%17%11%1
96
February1st to 15thDay
7%26%24%21%17%2
90
16th to endDay
14%10%31%28%14%
114
March1st to 15thDay
7%8%32%32%14%3
270
16th to endDay
12%6%25%27%23%5%
288
April1st to 15thDay
9%8%22%28%26%4
270
16th to endDay
5%120%27%30%13%
270
May1st to 15thDay
7%415%28%22%21%
288
16th to endDay
6%37%20%34%28%
331
June1st to 15thDay
13%26%16%27%32%
315
16th to endDay
8%410%27%48%
315
July1st to 15thDay
4125%25%60%
305
16th to endDay
9%16%11%26%46%
326
August1st to 15thDay
9%248%24%49%
313
16th to endDay
9%15%11%27%44%
332
September1st to 15thDay
13%2415%28%35%
315
16th to endDay
12%416%37%27%
283
October1st to 15thDay
10%112%30%33%11%
255
16th to endDay
10%221%27%28%9%
272
November1st to 15thDay
7%319%37%23%8%
265
16th to endDay
7%135%28%22%4
160
December1st to 15thDay
5%12%44%25%12%
90
16th to endDay
7%5%22%37%23%3
96
January1st to 15thNight
15%9%28%32%13%
720
16th to endNight
17%8%29%34%9%
768
February1st to 15thNight
13%7%32%33%11%
704
16th to endNight
12%9%33%38%7%
631
March1st to 15thNight
8%7%34%37%11%
720
16th to endNight
9%6%30%37%14%
768
April1st to 15thNight
7%5%34%37%13%
718
16th to endNight
8%229%39%19%
702
May1st to 15thNight
5%117%46%25%3
540
16th to endNight
6%10%39%35%6%
563
June1st to 15thNight
12%18%26%37%13%
540
16th to endNight
8%1318%39%28%
540
July1st to 15thNight
7%213%43%32%
510
16th to endNight
31214%52%26%
564
August1st to 15thNight
6%210%48%30%
539
16th to endNight
10%15%17%40%25%
693
September1st to 15thNight
10%5%25%38%18%
720
16th to endNight
11%19%29%39%8%
689
October1st to 15thNight
9%111%41%32%3
660
16th to endNight
10%320%35%28%2
704
November1st to 15thNight
6%425%37%23%3
700
16th to endNight
9%431%36%17%
720
December1st to 15thNight
12%5%28%35%17%
720
16th to endNight
10%6%24%37%19%1
768
Page generated at 2017-09-24 09:15:51. Version ac04

Copyright 2017 A. Danko


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