Lucile Miller Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lucile Miller Observatory clear sky chart from 2005-11-05 to 2018-02-22.

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
49%
16379
22%
48878
15%
16341
57%
16341
28%
30750

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
34%
778
24%
2522
12%
776
50%
776
27%
1486
January16th to endNight
33%
832
27%
2704
16%
832
48%
832
28%
1594
February1st to 15thNight
29%
761
23%
2432
10%
761
45%
761
27%
1469
February16th to endNight
28%
659
28%
1959
13%
659
43%
659
29%
1212
March1st to 15thNight
39%
720
27%
1980
15%
720
48%
720
30%
1241
March16th to endNight
39%
768
20%
2112
12%
768
47%
768
27%
1405
April1st to 15thNight
43%
718
23%
1925
11%
718
51%
718
34%
1181
April16th to endNight
47%
618
24%
1698
13%
618
53%
618
32%
1063
May1st to 15thNight
46%
540
16%
1620
8%
540
51%
540
24%
1088
May16th to endNight
59%
561
17%
1684
14%
561
61%
561
27%
1104
June1st to 15thNight
66%
540
14%
1620
12%
540
67%
540
25%
1070
June16th to endNight
72%
540
16%
1620
15%
540
72%
540
28%
1055
July1st to 15thNight
70%
510
10%
1530
9%
510
70%
510
26%
1026
July16th to endNight
72%
564
13%
1595
12%
531
74%
531
26%
1065
August1st to 15thNight
66%
539
13%
1609
11%
536
66%
536
22%
1123
August16th to endNight
69%
654
19%
1800
16%
654
70%
654
27%
1223
September1st to 15thNight
66%
720
18%
1971
16%
720
67%
720
30%
1293
September16th to endNight
55%
717
20%
1980
17%
717
58%
717
24%
1377
October1st to 15thNight
56%
720
29%
2106
26%
720
61%
720
33%
1268
October16th to endNight
52%
768
35%
2304
26%
768
66%
768
38%
1276
November1st to 15thNight
54%
760
28%
2333
23%
760
62%
760
35%
1345
November16th to endNight
50%
780
29%
2535
23%
780
60%
780
31%
1439
December1st to 15thNight
41%
780
24%
2535
15%
780
52%
780
26%
1568
December16th to endNight
35%
832
23%
2704
15%
832
47%
832
22%
1779

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
13%5%2442445%7%43%
49372
Night
13%5%2442445%7%45%
49075
TransparencyDay
38%6%11%21%17%4
49073
Night
38%5%10%20%19%5%
48878
SeeingDay
17%316%24%22%16%
6119
Night
16%421%31%22%3
16386

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
18%5%24323345%45%
1746
16th to endDay
16%41332335%5%49%
1872
February1st to 15thDay
17%5%13323447%45%
1757
16th to endDay
15%5%2432335%6%46%
1661
March1st to 15thDay
15%41441325%7%47%
1980
16th to endDay
17%424424446%44%
2111
April1st to 15thDay
12%21322445%8%51%
2023
16th to endDay
15%424424447%45%
2273
May1st to 15thDay
13%6%24435%5%6%8%39%
2331
16th to endDay
10%6%344245%6%8%44%
2431
June1st to 15thDay
9%5%25%5%25%6%6%11%38%
2340
16th to endDay
7%4245%35%5%6%11%43%
2340
July1st to 15thDay
10%5%35%6%36%6%8%9%33%
2340
16th to endDay
8%425%6%47%6%8%11%33%
2465
August1st to 15thDay
12%6%25%7%46%5%7%8%32%
2340
16th to endDay
11%427%6%45%6%6%10%35%
2390
September1st to 15thDay
10%4245%35%5%7%9%41%
1986
16th to endDay
17%6%25%424446%39%
1980
October1st to 15thDay
15%41332323455%
1852
16th to endDay
13%41331222459%
1920
November1st to 15thDay
13%424312336%53%
1852
16th to endDay
15%5%23313446%50%
1755
December1st to 15thDay
16%6%243235%46%45%
1755
16th to endDay
20%5%25%323345%41%
1872
January1st to 15thNight
17%424313345%49%
2522
16th to endNight
16%414323345%49%
2704
February1st to 15thNight
16%5%23413345%49%
2423
16th to endNight
14%42442445%6%46%
1959
March1st to 15thNight
13%5%2432435%6%47%
1980
16th to endNight
16%6%2442435%6%43%
2112
April1st to 15thNight
12%6%1332345%7%50%
1925
16th to endNight
13%5%2442435%6%47%
1698
May1st to 15thNight
12%6%25%6%35%5%45%41%
1619
16th to endNight
11%5%146%345%6%8%41%
1682
June1st to 15thNight
10%425%5%47%6%6%11%36%
1620
16th to endNight
5%4246%36%6%8%10%39%
1620
July1st to 15thNight
9%415%6%46%7%7%12%33%
1620
16th to endNight
5%5%346%47%8%8%13%32%
1703
August1st to 15thNight
11%6%25%6%45%7%6%10%32%
1620
16th to endNight
9%5%246%35%5%8%11%35%
1800
September1st to 15thNight
11%4145%35%5%5%8%42%
1971
16th to endNight
17%6%346%25%35%6%38%
1980
October1st to 15thNight
15%5%24312336%52%
2106
16th to endNight
11%22431333459%
2304
November1st to 15thNight
14%313323245%54%
2333
16th to endNight
14%313323446%51%
2535
December1st to 15thNight
16%5%25%324345%45%
2535
16th to endNight
21%6%24324335%39%
2704

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%37%20%21%5%
1747
16th to endDay
35%36%24%20%8%
1872
February1st to 15thDay
38%48%22%20%5%
1759
16th to endDay
37%49%23%18%5%
1661
March1st to 15thDay
37%47%23%22%5%
1980
16th to endDay
40%6%10%20%18%3
2112
April1st to 15thDay
31%411%26%21%5%
2023
16th to endDay
39%5%8%19%18%7%
2273
May1st to 15thDay
41%6%14%21%13%2
2331
16th to endDay
37%7%15%24%13%2
2435
June1st to 15thDay
37%8%17%24%11%
2340
16th to endDay
34%9%16%22%14%2
2340
July1st to 15thDay
42%9%16%18%10%3
2201
16th to endDay
40%9%18%20%10%1
2310
August1st to 15thDay
46%8%15%18%9%
2327
16th to endDay
42%8%17%20%9%1
2390
September1st to 15thDay
37%7%13%20%17%3
1986
16th to endDay
45%410%16%19%3
1980
October1st to 15thDay
33%38%23%24%6%
1852
16th to endDay
30%35%23%27%9%
1920
November1st to 15thDay
33%37%19%27%8%
1852
16th to endDay
34%36%22%25%7%
1755
December1st to 15thDay
40%49%22%17%5%
1755
16th to endDay
45%29%19%17%4
1872
January1st to 15thNight
37%39%16%26%7%
2522
16th to endNight
37%26%21%24%7%
2704
February1st to 15thNight
38%37%21%23%5%
2432
16th to endNight
37%49%23%22%3
1959
March1st to 15thNight
37%48%20%21%7%
1980
16th to endNight
42%48%21%17%5%
2112
April1st to 15thNight
33%48%25%21%5%
1925
16th to endNight
36%410%18%21%8%
1698
May1st to 15thNight
43%6%11%20%15%1
1620
16th to endNight
38%8%12%25%12%2
1684
June1st to 15thNight
39%9%16%23%9%1
1620
16th to endNight
37%9%15%20%12%4
1620
July1st to 15thNight
39%10%18%20%9%3
1530
16th to endNight
37%11%20%19%9%2
1595
August1st to 15thNight
44%9%17%15%12%
1609
16th to endNight
38%10%17%21%10%1
1800
September1st to 15thNight
38%7%15%18%15%4
1971
16th to endNight
46%5%10%14%19%3
1980
October1st to 15thNight
35%47%23%23%5%
2106
16th to endNight
30%25%21%27%11%
2304
November1st to 15thNight
33%36%18%25%12%
2333
16th to endNight
33%45%21%27%7%
2535
December1st to 15thNight
40%49%19%20%6%
2535
16th to endNight
47%38%17%18%4
2704

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
22%11%30%25%9%
135
16th to endDay
16%14%36%20%10%1
144
February1st to 15thDay
25%11%38%20%2
135
16th to endDay
19%9%32%30%7%
118
March1st to 15thDay
17%6%31%31%11%
270
16th to endDay
19%330%32%12%
288
April1st to 15thDay
14%11%20%28%21%3
270
16th to endDay
21%219%25%18%12%
270
May1st to 15thDay
17%422%24%20%9%
288
16th to endDay
16%39%19%28%23%
331
June1st to 15thDay
13%19%22%27%25%
315
16th to endDay
12%8%22%29%26%
315
July1st to 15thDay
12%16%20%27%31%
305
16th to endDay
9%313%35%37%
326
August1st to 15thDay
20%5%16%27%29%
313
16th to endDay
14%419%25%35%
332
September1st to 15thDay
13%17%17%29%30%
315
16th to endDay
20%110%20%27%19%
314
October1st to 15thDay
21%112%29%25%10%
315
16th to endDay
14%413%33%23%11%
336
November1st to 15thDay
23%217%28%21%6%
270
16th to endDay
8%324%28%26%8%
135
December1st to 15thDay
22%5%23%34%12%
135
16th to endDay
28%10%32%21%6%
144
January1st to 15thNight
19%9%30%33%6%
780
16th to endNight
19%8%33%34%4
832
February1st to 15thNight
20%8%35%33%1
764
16th to endNight
18%10%37%29%4
659
March1st to 15thNight
17%8%30%35%7%
720
16th to endNight
21%5%26%34%10%
768
April1st to 15thNight
15%8%28%31%15%
718
16th to endNight
16%424%34%19%
618
May1st to 15thNight
16%424%34%20%
540
16th to endNight
13%111%30%36%6%
563
June1st to 15thNight
11%10%31%36%8%
540
16th to endNight
7%8%30%45%7%
540
July1st to 15thNight
10%5%28%45%8%
510
16th to endNight
6%427%46%14%
564
August1st to 15thNight
13%5%26%46%7%
539
16th to endNight
12%5%22%50%9%
654
September1st to 15thNight
14%6%28%40%9%
720
16th to endNight
19%211%27%33%5%
717
October1st to 15thNight
17%218%28%28%4
720
16th to endNight
13%324%32%22%3
768
November1st to 15thNight
16%420%37%19%2
760
16th to endNight
16%5%24%35%16%1
780
December1st to 15thNight
20%5%25%37%10%
780
16th to endNight
24%428%34%7%
832
Page generated at 2018-02-23 11:21:40. Version ac04

Copyright 2018 A. Danko


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