Luckie's Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Luckie's Observatory clear sky chart from 2005-11-05 to 2018-01-20.

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
47%
16042
23%
48487
15%
15999
56%
15999
27%
30278

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
29%
780
23%
2522
10%
776
45%
776
21%
1544
January16th to endNight
26%
788
26%
2557
11%
788
44%
788
22%
1581
February1st to 15thNight
31%
702
27%
2110
11%
699
46%
699
27%
1252
February16th to endNight
26%
631
24%
1893
10%
631
40%
631
23%
1193
March1st to 15thNight
33%
720
24%
2045
12%
720
43%
720
27%
1299
March16th to endNight
38%
768
21%
2112
10%
768
45%
768
29%
1343
April1st to 15thNight
42%
667
25%
1925
15%
667
52%
667
33%
1136
April16th to endNight
49%
540
24%
1668
16%
540
56%
540
29%
1013
May1st to 15thNight
48%
540
19%
1620
10%
540
55%
540
27%
1036
May16th to endNight
59%
561
19%
1683
14%
561
62%
561
29%
1058
June1st to 15thNight
65%
540
15%
1620
12%
540
67%
540
27%
1053
June16th to endNight
74%
540
16%
1620
14%
540
75%
540
31%
996
July1st to 15thNight
70%
510
11%
1530
9%
510
70%
510
24%
1040
July16th to endNight
71%
564
15%
1595
12%
531
74%
531
27%
1062
August1st to 15thNight
66%
539
16%
1609
15%
536
67%
536
26%
1081
August16th to endNight
64%
575
18%
1886
19%
575
65%
575
22%
1279
September1st to 15thNight
60%
720
17%
1980
15%
720
62%
720
26%
1337
September16th to endNight
58%
717
24%
1980
19%
717
62%
717
30%
1271
October1st to 15thNight
53%
720
31%
2016
23%
720
60%
720
34%
1216
October16th to endNight
51%
768
35%
2304
26%
768
65%
768
38%
1271
November1st to 15thNight
52%
760
29%
2438
25%
760
61%
760
34%
1356
November16th to endNight
42%
780
28%
2535
20%
780
54%
780
29%
1464
December1st to 15thNight
37%
780
24%
2535
14%
780
49%
780
23%
1587
December16th to endNight
30%
832
21%
2704
12%
832
42%
832
18%
1810

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
14%4245%35%5%5%7%40%
49034
Night
14%42442445%7%45%
48687
TransparencyDay
40%7%10%18%17%4
48735
Night
37%6%11%19%19%5%
48490
SeeingDay
18%6%18%23%20%13%
5831
Night
17%7%21%29%20%4
16046

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%6%2442432445%
1746
16th to endDay
17%5%13314435%48%
1770
February1st to 15thDay
16%5%1431445%6%44%
1750
16th to endDay
17%5%24223446%45%
1580
March1st to 15thDay
18%424324446%44%
1914
16th to endDay
18%5%245%24346%42%
2111
April1st to 15thDay
13%4235%345%6%8%42%
2033
16th to endDay
14%42442445%7%46%
2290
May1st to 15thDay
13%5%26%5%25%45%7%41%
2331
16th to endDay
12%425%7%36%6%6%8%37%
2431
June1st to 15thDay
9%426%7%47%7%8%9%32%
2340
16th to endDay
5%3246%47%7%8%10%38%
2340
July1st to 15thDay
11%5%36%7%5%8%7%8%9%25%
2340
16th to endDay
7%426%7%5%9%8%8%9%28%
2465
August1st to 15thDay
11%425%7%46%7%8%10%30%
2340
16th to endDay
13%6%27%7%47%5%6%9%27%
2300
September1st to 15thDay
13%5%16%7%26%6%7%7%34%
1980
16th to endDay
17%5%2442335%7%42%
1980
October1st to 15thDay
15%412312335%55%
1944
16th to endDay
12%41221322460%
1920
November1st to 15thDay
13%323323336%55%
1747
16th to endDay
17%312413345%49%
1755
December1st to 15thDay
20%5%24324445%41%
1755
16th to endDay
26%7%14322345%38%
1872
January1st to 15thNight
18%42342324447%
2522
16th to endNight
17%5%24423345%45%
2557
February1st to 15thNight
14%324324345%51%
2103
16th to endNight
15%42442445%6%44%
1893
March1st to 15thNight
16%423324445%47%
2045
16th to endNight
15%5%24324445%48%
2112
April1st to 15thNight
14%31331345%5%52%
1925
16th to endNight
11%425%424446%49%
1668
May1st to 15thNight
13%4245%3345%8%43%
1619
16th to endNight
10%5%244345%6%7%45%
1682
June1st to 15thNight
9%4245%36%5%9%10%38%
1620
16th to endNight
6%2145%45%6%7%11%44%
1620
July1st to 15thNight
9%435%5%47%7%7%11%35%
1620
16th to endNight
6%4245%46%6%10%12%35%
1703
August1st to 15thNight
12%5%25%5%346%7%11%35%
1620
16th to endNight
12%5%35%6%26%5%7%10%34%
1886
September1st to 15thNight
12%5%25%435%6%5%9%39%
1980
16th to endNight
14%41442445%7%44%
1980
October1st to 15thNight
14%31332234454%
2016
16th to endNight
11%31332233460%
2304
November1st to 15thNight
14%323212335%56%
2438
16th to endNight
16%313323345%51%
2535
December1st to 15thNight
17%5%25%423336%45%
2535
16th to endNight
22%7%34324446%36%
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
42%47%16%22%6%
1747
16th to endDay
37%46%20%22%8%
1770
February1st to 15thDay
38%48%20%23%4
1752
16th to endDay
39%5%7%21%18%6%
1580
March1st to 15thDay
40%5%7%19%20%7%
1914
16th to endDay
42%5%11%20%16%3
2112
April1st to 15thDay
37%5%10%20%20%5%
2033
16th to endDay
36%5%9%21%21%5%
2290
May1st to 15thDay
40%7%11%18%19%2
2331
16th to endDay
40%10%12%19%13%2
2435
June1st to 15thDay
42%12%17%19%6%1
2340
16th to endDay
35%12%15%19%14%2
2340
July1st to 15thDay
47%11%16%16%6%1
2201
16th to endDay
43%13%15%18%7%1
2310
August1st to 15thDay
44%10%16%19%7%1
2327
16th to endDay
49%10%14%15%8%1
2300
September1st to 15thDay
42%10%12%16%14%3
1980
16th to endDay
40%6%11%18%19%4
1980
October1st to 15thDay
32%410%18%27%7%
1944
16th to endDay
29%2419%29%13%
1920
November1st to 15thDay
32%37%16%29%10%
1747
16th to endDay
36%35%17%28%8%
1755
December1st to 15thDay
43%46%18%18%7%
1755
16th to endDay
48%37%18%15%6%
1872
January1st to 15thNight
40%38%15%25%7%
2522
16th to endNight
41%35%18%23%8%
2557
February1st to 15thNight
35%37%20%24%7%
2112
16th to endNight
39%48%20%22%4
1893
March1st to 15thNight
38%5%10%18%19%8%
2045
16th to endNight
37%5%11%22%19%4
2112
April1st to 15thNight
32%49%24%22%6%
1925
16th to endNight
35%5%8%22%20%7%
1668
May1st to 15thNight
38%6%13%21%18%2
1620
16th to endNight
35%8%15%26%11%2
1684
June1st to 15thNight
35%11%20%22%8%1
1620
16th to endNight
31%10%18%22%14%1
1620
July1st to 15thNight
40%11%21%18%7%1
1530
16th to endNight
34%13%21%19%8%2
1595
August1st to 15thNight
39%9%18%20%10%1
1609
16th to endNight
41%11%17%18%10%1
1886
September1st to 15thNight
39%9%14%17%14%3
1980
16th to endNight
37%6%12%21%16%4
1980
October1st to 15thNight
33%410%18%25%6%
2016
16th to endNight
28%45%19%29%13%
2304
November1st to 15thNight
31%36%17%28%11%
2438
16th to endNight
34%46%18%25%9%
2535
December1st to 15thNight
41%47%19%18%8%
2535
16th to endNight
47%49%15%17%5%
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
24%17%32%20%4
135
16th to endDay
22%27%31%15%3
109
February1st to 15thDay
16%22%47%12%1
90
16th to endDay
30%12%41%12%2
81
March1st to 15thDay
23%11%27%26%9%
204
16th to endDay
25%10%23%25%14%1
288
April1st to 15thDay
17%8%25%24%18%4
270
16th to endDay
17%424%27%18%7%
270
May1st to 15thDay
14%9%27%18%15%14%
288
16th to endDay
16%5%16%20%22%17%
331
June1st to 15thDay
11%211%25%25%23%
315
16th to endDay
10%114%25%22%25%
315
July1st to 15thDay
9%111%23%25%27%
305
16th to endDay
7%7%18%34%30%
326
August1st to 15thDay
19%17%24%20%26%
313
16th to endDay
18%16%20%30%22%
332
September1st to 15thDay
16%310%21%30%16%
315
16th to endDay
19%11%27%28%12%
314
October1st to 15thDay
21%317%29%20%7%
315
16th to endDay
16%6%19%28%25%4
336
November1st to 15thDay
25%9%19%24%17%3
165
16th to endDay
17%5%28%30%14%2
135
December1st to 15thDay
28%14%31%20%4
135
16th to endDay
40%13%29%15%
144
January1st to 15thNight
23%13%27%26%8%
780
16th to endNight
20%13%32%28%3
788
February1st to 15thNight
18%14%30%33%3
704
16th to endNight
19%15%33%27%4
631
March1st to 15thNight
20%12%30%30%5%
720
16th to endNight
19%9%27%30%13%
768
April1st to 15thNight
17%11%25%29%14%1
667
16th to endNight
14%6%23%32%20%2
540
May1st to 15thNight
17%5%21%31%21%3
540
16th to endNight
13%116%27%35%6%
563
June1st to 15thNight
11%110%30%36%9%
540
16th to endNight
6%110%31%36%13%
540
July1st to 15thNight
11%17%22%43%12%
510
16th to endNight
8%17%24%42%15%
564
August1st to 15thNight
17%6%22%38%14%
539
16th to endNight
15%7%23%40%12%
575
September1st to 15thNight
15%112%24%35%11%
720
16th to endNight
17%113%33%29%3
717
October1st to 15thNight
16%5%20%29%23%5%
720
16th to endNight
13%6%23%30%23%3
768
November1st to 15thNight
15%6%20%32%20%3
760
16th to endNight
18%9%24%30%16%
780
December1st to 15thNight
20%10%24%31%11%
780
16th to endNight
26%9%28%27%7%
832
Page generated at 2018-01-21 12:19:23. Version ac04

Copyright 2018 A. Danko


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