Lawshe Memorial Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lawshe Memorial 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
32%
15684
11%
46836
7%
15642
35%
15642
14%
35639

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
14%
900
3%
2506
1%
895
15%
895
5%
2265
January16th to endNight
16%
960
6%
2688
3%
960
19%
960
6%
2383
February1st to 15thNight
17%
746
5%
2303
2%
746
20%
746
6%
1955
February16th to endNight
26%
631
9%
1893
4%
631
30%
631
9%
1565
March1st to 15thNight
29%
720
15%
2124
9%
720
34%
720
18%
1516
March16th to endNight
36%
744
19%
2088
11%
744
42%
744
21%
1466
April1st to 15thNight
31%
539
14%
1775
9%
539
38%
539
16%
1261
April16th to endNight
36%
540
18%
1620
9%
540
44%
540
22%
1114
May1st to 15thNight
38%
540
11%
1620
7%
540
43%
540
19%
1161
May16th to endNight
48%
539
15%
1483
10%
538
54%
538
29%
973
June1st to 15thNight
48%
360
13%
1260
11%
360
53%
360
21%
796
June16th to endNight
53%
360
12%
1260
11%
360
57%
360
24%
788
July1st to 15thNight
58%
489
14%
1339
10%
489
60%
489
33%
834
July16th to endNight
56%
564
15%
1417
11%
531
59%
531
34%
899
August1st to 15thNight
59%
539
18%
1560
13%
536
63%
536
35%
926
August16th to endNight
58%
573
16%
1758
12%
573
62%
573
29%
1082
September1st to 15thNight
51%
615
15%
1875
12%
615
54%
615
25%
1199
September16th to endNight
48%
658
15%
1818
11%
658
50%
658
25%
1241
October1st to 15thNight
35%
660
16%
1877
10%
660
41%
660
20%
1355
October16th to endNight
23%
704
7%
2287
4%
704
27%
704
8%
1871
November1st to 15thNight
23%
700
13%
2276
9%
700
28%
700
11%
1746
November16th to endNight
15%
743
6%
2471
4%
743
18%
743
6%
2123
December1st to 15thNight
9%
900
2%
2700
1%
900
10%
900
3%
2492
December16th to endNight
9%
960
3%
2838
1%
960
11%
960
3%
2628

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
16%10%47%5%3445%6%32%
47907
Night
16%11%5%8%6%34445%28%
47004
Cloud CoverDay
15%10%47%6%3445%7%31%
47916
Night
15%11%5%8%6%34445%28%
47009
TransparencyDay
52%6%11%19%9%
47593
Night
57%6%10%16%7%
46836
SeeingDay
20%9%26%27%13%3
5991
Night
21%10%27%27%10%1
15688

By Month

Percentage Cloud Cover NE (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
16%18%9%14%9%444348%
1432
16th to endDay
13%17%11%15%9%45%34311%
1536
February1st to 15thDay
12%15%8%10%12%45%44415%
1557
16th to endDay
13%13%7%11%7%44445%21%
1580
March1st to 15thDay
11%10%47%8%4445%7%32%
1826
16th to endDay
14%8%46%435%447%35%
2148
April1st to 15thDay
20%12%3432345%6%32%
2172
16th to endDay
17%10%46%423446%35%
2340
May1st to 15thDay
16%6%35%435%5%5%5%37%
2331
16th to endDay
13%6%24425%35%8%42%
2627
June1st to 15thDay
14%5%25%5%35%46%9%38%
2700
16th to endDay
15%5%245%35%35%7%40%
2700
July1st to 15thDay
11%5%134235%5%8%47%
2538
16th to endDay
11%41432346%9%47%
2655
August1st to 15thDay
9%4245%35%5%6%9%45%
2389
16th to endDay
15%6%24423447%43%
2441
September1st to 15thDay
17%6%25%423348%41%
2073
16th to endDay
17%5%25%5%2346%9%38%
1815
October1st to 15thDay
23%11%35%5%23335%30%
1752
16th to endDay
29%14%47%6%35%345%14%
1584
November1st to 15thDay
19%16%5%7%5%33346%24%
1582
16th to endDay
20%24%9%11%7%2333311%
1486
December1st to 15thDay
17%20%13%17%7%233328%
1260
16th to endDay
19%25%9%13%8%322238%
1383
January1st to 15thNight
18%15%9%16%10%4433311%
2506
16th to endNight
13%15%7%15%11%45%33413%
2688
February1st to 15thNight
11%17%8%12%10%36%43417%
2301
16th to endNight
14%15%5%11%8%45%445%19%
1893
March1st to 15thNight
13%10%47%6%44335%35%
2111
16th to endNight
14%8%36%5%35%45%437%
2088
April1st to 15thNight
22%9%345%3435%5%32%
1775
16th to endNight
15%8%35%5%24445%38%
1620
May1st to 15thNight
15%7%37%7%35%5%5%6%32%
1620
16th to endNight
13%5%245%3436%7%43%
1481
June1st to 15thNight
15%5%25%5%35%448%40%
1260
16th to endNight
12%5%245%35%46%8%40%
1260
July1st to 15thNight
11%4245%2445%7%46%
1419
16th to endNight
7%42443347%7%49%
1513
August1st to 15thNight
8%32442445%8%50%
1569
16th to endNight
13%5%13423347%48%
1758
September1st to 15thNight
14%6%25%423445%45%
1875
16th to endNight
18%6%2443345%7%39%
1818
October1st to 15thNight
20%9%35%5%23447%33%
1877
16th to endNight
26%14%37%6%35%345%20%
2287
November1st to 15thNight
19%16%47%5%23345%25%
2276
16th to endNight
21%20%8%11%6%2433413%
2471
December1st to 15thNight
17%21%12%16%8%332228%
2700
16th to endNight
19%20%10%14%9%333229%
2838

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
16%17%9%15%9%443448%
1432
16th to endDay
12%17%10%16%9%45%33411%
1536
February1st to 15thDay
12%15%8%11%11%45%5%4415%
1557
16th to endDay
13%13%7%11%8%45%45%5%19%
1580
March1st to 15thDay
11%10%5%7%7%3445%7%30%
1836
16th to endDay
14%8%47%435%45%6%33%
2147
April1st to 15thDay
20%12%34334446%31%
2172
16th to endDay
17%10%36%42435%6%35%
2340
May1st to 15thDay
15%8%35%5%34446%36%
2331
16th to endDay
13%6%24435%45%8%41%
2627
June1st to 15thDay
14%6%25%5%345%6%9%37%
2700
16th to endDay
14%5%245%35%46%7%39%
2700
July1st to 15thDay
11%5%244245%5%8%46%
2538
16th to endDay
10%5%1432337%9%45%
2655
August1st to 15thDay
9%325%5%25%5%5%9%45%
2389
16th to endDay
14%5%35%5%24348%42%
2441
September1st to 15thDay
15%7%345%33347%41%
2073
16th to endDay
16%6%245%3435%9%38%
1815
October1st to 15thDay
22%10%46%6%23236%30%
1752
16th to endDay
26%15%48%7%34345%14%
1584
November1st to 15thDay
19%15%5%7%6%33346%23%
1582
16th to endDay
18%22%9%10%8%3323312%
1486
December1st to 15thDay
16%20%13%16%7%342338%
1260
16th to endDay
20%23%9%14%9%322337%
1383
January1st to 15thNight
18%14%9%14%11%4433311%
2506
16th to endNight
12%16%7%14%12%5%5%43413%
2688
February1st to 15thNight
11%16%8%11%10%46%43417%
2294
16th to endNight
13%14%6%10%8%45%5%45%19%
1893
March1st to 15thNight
13%10%48%7%35%335%35%
2124
16th to endNight
14%8%46%5%35%445%37%
2088
April1st to 15thNight
21%9%3443445%6%31%
1775
16th to endNight
14%8%36%425%45%5%38%
1620
May1st to 15thNight
14%8%37%7%45%5%5%6%31%
1619
16th to endNight
12%5%25%5%3435%8%43%
1481
June1st to 15thNight
14%435%43435%8%40%
1260
16th to endNight
12%5%24435%46%9%40%
1260
July1st to 15thNight
10%5%25%425%45%6%47%
1419
16th to endNight
7%42443447%8%47%
1513
August1st to 15thNight
8%415%42445%9%49%
1569
16th to endNight
11%6%23424346%48%
1758
September1st to 15thNight
14%6%25%424446%45%
1875
16th to endNight
17%6%25%42345%8%39%
1818
October1st to 15thNight
20%9%26%423446%34%
1877
16th to endNight
24%13%48%6%35%435%20%
2287
November1st to 15thNight
18%15%38%6%34346%25%
2276
16th to endNight
20%19%7%12%6%2434413%
2471
December1st to 15thNight
17%19%11%15%10%442328%
2700
16th to endNight
18%19%11%13%9%443229%
2838

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
80%6%5%6%
1433
16th to endDay
80%45%6%2
1536
February1st to 15thDay
71%7%8%9%3
1559
16th to endDay
64%7%10%13%4
1580
March1st to 15thDay
52%5%14%18%6%1
1836
16th to endDay
49%7%12%20%8%1
2148
April1st to 15thDay
52%410%19%10%
2172
16th to endDay
49%5%11%16%15%2
2340
May1st to 15thDay
48%7%9%21%10%3
2331
16th to endDay
40%7%11%25%13%1
2631
June1st to 15thDay
41%7%12%25%12%1
2700
16th to endDay
42%8%13%22%12%
2700
July1st to 15thDay
35%6%12%29%14%1
2389
16th to endDay
35%7%14%24%16%
2488
August1st to 15thDay
35%8%14%28%13%
2374
16th to endDay
40%7%13%25%11%1
2441
September1st to 15thDay
42%7%12%26%11%
2073
16th to endDay
42%7%15%24%10%
1815
October1st to 15thDay
57%5%9%20%7%
1752
16th to endDay
71%6%10%8%2
1584
November1st to 15thDay
61%5%10%15%6%
1582
16th to endDay
78%5%7%6%1
1486
December1st to 15thDay
83%5%5%4
1260
16th to endDay
84%45%31
1383
January1st to 15thNight
79%5%7%5%1
2506
16th to endNight
76%5%7%7%2
2688
February1st to 15thNight
71%6%8%10%2
2303
16th to endNight
68%6%9%11%4
1893
March1st to 15thNight
52%5%10%20%10%
2124
16th to endNight
47%6%10%21%12%1
2088
April1st to 15thNight
53%48%21%10%1
1775
16th to endNight
46%5%9%19%15%2
1620
May1st to 15thNight
50%6%10%18%9%3
1620
16th to endNight
38%6%12%24%15%2
1483
June1st to 15thNight
42%6%11%23%14%1
1260
16th to endNight
39%7%14%24%13%
1260
July1st to 15thNight
34%6%10%28%17%1
1339
16th to endNight
33%7%15%25%16%1
1417
August1st to 15thNight
31%6%16%31%12%
1560
16th to endNight
36%7%16%25%13%1
1758
September1st to 15thNight
40%6%13%24%13%1
1875
16th to endNight
42%8%15%24%8%
1818
October1st to 15thNight
50%6%9%23%8%
1877
16th to endNight
66%7%11%11%3
2287
November1st to 15thNight
60%6%11%15%5%
2276
16th to endNight
74%410%6%2
2471
December1st to 15thNight
83%5%6%4
2700
16th to endNight
82%6%5%41
2838

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
23%15%37%20%3
90
16th to endDay
33%6%27%26%7%
96
February1st to 15thDay
21%26%33%14%4
90
16th to endDay
18%20%37%19%3
81
March1st to 15thDay
19%18%27%23%9%
126
16th to endDay
25%6%26%27%12%2
288
April1st to 15thDay
28%9%28%19%12%1
270
16th to endDay
21%11%30%20%12%3
270
May1st to 15thDay
22%13%25%22%12%3
288
16th to endDay
17%9%31%27%10%3
506
June1st to 15thDay
19%9%31%27%9%3
495
16th to endDay
17%6%29%33%10%3
495
July1st to 15thDay
14%7%25%31%16%4
475
16th to endDay
13%425%36%14%5%
515
August1st to 15thDay
9%419%36%21%7%
362
16th to endDay
24%318%25%20%7%
332
September1st to 15thDay
17%420%24%23%9%
315
16th to endDay
17%9%19%29%18%5%
254
October1st to 15thDay
30%6%25%26%9%1
255
16th to endDay
31%16%29%19%3
96
November1st to 15thDay
24%11%23%30%10%1
90
16th to endDay
30%19%26%18%4
71
December1st to 15thDay
40%28%21%6%11
60
16th to endDay
35%36%25%11
71
January1st to 15thNight
24%17%28%23%5%
900
16th to endNight
20%15%33%24%5%
960
February1st to 15thNight
19%15%37%21%5%
749
16th to endNight
21%12%30%29%6%
631
March1st to 15thNight
17%12%32%26%9%1
720
16th to endNight
19%9%28%31%10%1
744
April1st to 15thNight
26%8%28%29%6%
539
16th to endNight
19%7%32%28%10%1
540
May1st to 15thNight
15%7%30%34%10%
540
16th to endNight
14%5%25%37%15%1
540
June1st to 15thNight
16%5%23%38%15%
360
16th to endNight
13%323%40%18%1
360
July1st to 15thNight
12%319%41%19%3
489
16th to endNight
9%224%36%25%1
564
August1st to 15thNight
10%120%37%27%1
539
16th to endNight
17%117%37%23%2
573
September1st to 15thNight
18%420%31%20%4
615
16th to endNight
21%421%31%15%4
658
October1st to 15thNight
25%8%25%27%11%
660
16th to endNight
36%11%25%20%5%1
704
November1st to 15thNight
28%14%28%20%7%
700
16th to endNight
31%16%29%17%4
743
December1st to 15thNight
25%24%32%13%3
900
16th to endNight
27%17%32%18%31
960
Page generated at 2017-09-16 17:07:00. Version ac04

Copyright 2017 A. Danko


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