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 2017-09-16.

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%
15535
22%
46916
15%
15492
55%
15492
27%
29387

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%
720
23%
2327
10%
716
45%
716
21%
1428
January16th to endNight
25%
768
25%
2493
10%
768
43%
768
22%
1552
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
55%
658
22%
1818
16%
658
60%
658
28%
1192
October1st to 15thNight
53%
660
32%
1848
24%
660
60%
660
34%
1118
October16th to endNight
52%
704
33%
2112
25%
704
64%
704
37%
1178
November1st to 15thNight
52%
700
31%
2246
26%
700
62%
700
35%
1224
November16th to endNight
40%
720
26%
2340
18%
720
51%
720
27%
1382
December1st to 15thNight
37%
720
23%
2340
15%
720
49%
720
23%
1464
December16th to endNight
30%
768
21%
2496
12%
768
43%
768
18%
1671

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%
47821
Night
14%42442445%7%45%
47116
TransparencyDay
40%7%11%18%17%4
47522
Night
37%6%11%19%19%5%
46919
SeeingDay
17%5%18%23%20%13%
5404
Night
17%7%21%29%20%4
15539

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%2442433445%
1611
16th to endDay
17%5%13314335%48%
1730
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
18%5%2442335%7%40%
1815
October1st to 15thDay
15%41231234456%
1782
16th to endDay
13%5%1321322459%
1760
November1st to 15thDay
13%223322335%57%
1610
16th to endDay
19%422423345%48%
1620
December1st to 15thDay
20%5%24424445%41%
1620
16th to endDay
26%6%14322345%39%
1728
January1st to 15thNight
19%4235%2324447%
2327
16th to endNight
17%5%24423345%45%
2493
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
15%41442445%7%43%
1818
October1st to 15thNight
14%41332234454%
1848
16th to endNight
11%31332233459%
2112
November1st to 15thNight
13%323212335%58%
2246
16th to endNight
17%413323345%50%
2340
December1st to 15thNight
17%5%25%423336%45%
2340
16th to endNight
22%7%34324446%37%
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
42%48%15%23%5%
1612
16th to endDay
37%46%20%22%8%
1730
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
42%6%10%17%18%4
1815
October1st to 15thDay
31%410%18%26%8%
1782
16th to endDay
30%3419%29%12%
1760
November1st to 15thDay
30%36%16%30%11%
1610
16th to endDay
37%45%17%26%8%
1620
December1st to 15thDay
44%47%18%17%7%
1620
16th to endDay
47%37%18%16%6%
1728
January1st to 15thNight
40%48%15%24%6%
2327
16th to endNight
41%35%18%23%7%
2493
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
39%6%11%20%15%4
1818
October1st to 15thNight
33%410%17%26%7%
1848
16th to endNight
29%45%19%29%12%
2112
November1st to 15thNight
30%35%17%30%13%
2246
16th to endNight
36%46%18%25%9%
2340
December1st to 15thNight
41%47%18%18%8%
2340
16th to endNight
47%48%15%18%5%
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
25%13%33%24%21
90
16th to endDay
25%28%32%12%2
96
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
24%11%27%26%10%
254
October1st to 15thDay
21%319%27%20%8%
255
16th to endDay
16%5%17%28%27%4
272
November1st to 15thDay
27%11%16%22%16%4
118
16th to endDay
22%6%27%27%14%1
90
December1st to 15thDay
26%15%32%21%31
90
16th to endDay
40%12%27%17%11
96
January1st to 15thNight
24%14%27%26%7%
720
16th to endNight
21%14%32%28%3
768
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
18%114%35%27%2
658
October1st to 15thNight
16%5%20%30%22%5%
660
16th to endNight
13%6%22%31%22%3
704
November1st to 15thNight
14%7%21%32%20%4
700
16th to endNight
20%10%25%28%15%
720
December1st to 15thNight
20%10%24%32%11%
720
16th to endNight
26%9%27%27%8%
768
Page generated at 2017-09-16 17:07:00. Version ac04

Copyright 2017 A. Danko


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