Lorenz Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lorenz Observatory clear sky chart from 2005-11-06 to 2024-01-12.

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%
22734
15%
74770
9%
22690
39%
22690
18%
51585

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 10thNight
17%
760
11%
2649
4%
757
26%
757
10%
1984
January11th to 20thNight
18%
727
9%
2506
4%
727
25%
727
9%
1981
January21st to endNight
21%
792
14%
2574
7%
792
30%
792
13%
1902
February1st to 10thNight
13%
720
9%
2340
3%
720
22%
720
10%
1797
February11th to 20thNight
18%
701
14%
2275
5%
700
29%
700
13%
1646
February21st to endNight
18%
592
15%
1848
4%
592
31%
592
15%
1303
March1st to 10thNight
23%
720
17%
2030
8%
720
32%
720
19%
1446
March11th to 20thNight
24%
720
16%
1979
6%
720
33%
720
19%
1394
March21st to endNight
27%
792
21%
2152
8%
792
37%
792
24%
1465
April1st to 10thNight
25%
720
17%
1800
5%
720
32%
720
23%
1292
April11th to 20thNight
28%
711
17%
1775
6%
711
33%
711
23%
1260
April21st to endNight
32%
566
16%
1646
7%
566
39%
566
21%
1131
May1st to 10thNight
38%
455
15%
1535
11%
455
44%
455
21%
1023
May11th to 20thNight
41%
354
22%
1416
16%
354
56%
354
23%
816
May21st to endNight
47%
388
17%
1551
17%
388
56%
388
26%
856
June1st to 10thNight
39%
360
13%
1440
12%
360
50%
360
20%
880
June11th to 20thNight
49%
360
16%
1440
21%
360
57%
360
25%
823
June21st to endNight
47%
360
13%
1440
15%
360
56%
360
21%
879
July1st to 10thNight
56%
350
16%
1400
21%
350
62%
350
30%
738
July11th to 20thNight
55%
348
17%
1392
24%
348
60%
348
27%
767
July21st to endNight
58%
438
18%
1528
17%
414
62%
414
30%
859
August1st to 10thNight
60%
537
18%
1600
15%
534
62%
534
33%
959
August11th to 20thNight
59%
534
20%
1598
14%
534
64%
534
33%
966
August21st to endNight
51%
728
21%
1916
10%
728
56%
728
34%
1212
September1st to 10thNight
50%
720
17%
1800
8%
720
53%
720
33%
1188
September11th to 20thNight
56%
720
27%
1807
15%
720
61%
720
37%
1136
September21st to endNight
47%
720
22%
2074
17%
720
51%
720
26%
1352
October1st to 10thNight
38%
720
16%
2160
12%
720
45%
720
22%
1470
October11th to 20thNight
27%
720
13%
2160
8%
720
35%
720
17%
1563
October21st to endNight
23%
792
15%
2389
7%
792
33%
792
15%
1765
November1st to 10thNight
35%
740
18%
2474
14%
740
43%
740
19%
1610
November11th to 20thNight
24%
760
15%
2660
8%
760
34%
760
15%
1829
November21st to endNight
22%
760
11%
2660
6%
760
29%
760
12%
1940
December1st to 10thNight
16%
760
9%
2660
4%
760
23%
760
9%
2062
December11th to 20thNight
17%
759
9%
3242
3%
759
25%
759
9%
2387
December21st to endNight
12%
830
5%
4854
1%
817
20%
817
5%
3904

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
15%9%36%6%35%5%5%7%35%
74687
Night
15%9%47%6%35%5%5%7%35%
75021
TransparencyDay
47%7%13%20%11%1
74395
Night
48%7%12%20%12%1
74847
SeeingDay
19%14%31%22%10%4
13339
Night
19%12%30%27%11%1
22744

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 10thDay
14%15%5%9%5%45%446%28%
1517
11th to 20thDay
15%17%6%8%6%46%5%5%5%23%
1480
21st to endDay
12%13%6%11%9%46%5%5%5%24%
1782
February1st to 10thDay
13%15%5%11%8%36%5%5%5%23%
1620
11th to 20thDay
11%13%6%11%10%44447%27%
1573
21st to endDay
19%13%5%9%8%34435%27%
1408
March1st to 10thDay
14%11%47%8%45%5%6%6%30%
1924
11th to 20thDay
13%13%47%6%44445%35%
1980
21st to endDay
19%11%35%5%35%445%37%
2204
April1st to 10thDay
18%11%48%6%34446%33%
2160
11th to 20thDay
20%7%46%5%33346%39%
2134
21st to endDay
20%8%36%6%445%36%34%
2330
May1st to 10thDay
17%7%37%6%36%46%7%35%
2424
11th to 20thDay
14%6%26%5%246%5%7%41%
2478
21st to endDay
12%5%35%6%36%5%6%8%42%
2725
June1st to 10thDay
17%6%35%6%35%5%7%8%36%
2520
11th to 20thDay
13%6%25%5%445%6%10%41%
2520
21st to endDay
14%6%35%5%35%6%6%9%38%
2520
July1st to 10thDay
9%4245%36%6%7%8%46%
2520
11th to 20thDay
10%5%35%5%46%6%7%9%39%
2520
21st to endDay
9%5%25%6%47%7%8%10%38%
2697
August1st to 10thDay
9%5%25%6%45%6%7%9%42%
2327
11th to 20thDay
9%5%25%6%46%6%7%9%40%
2303
21st to endDay
11%6%25%5%35%6%8%9%40%
2422
September1st to 10thDay
12%6%35%6%45%5%5%8%43%
2160
11th to 20thDay
11%4244345%5%7%49%
2151
21st to endDay
14%6%35%5%35%5%5%7%41%
1885
October1st to 10thDay
18%9%36%6%35%5%5%7%34%
1800
11th to 20thDay
18%9%37%7%446%47%29%
1800
21st to endDay
25%12%36%5%45%5%45%26%
1965
November1st to 10thDay
14%9%47%6%4445%6%36%
1600
11th to 20thDay
15%10%47%6%36%6%6%7%30%
1520
21st to endDay
19%14%47%7%35%5%47%25%
1520
December1st to 10thDay
17%15%6%9%8%45%45%5%23%
1520
11th to 20thDay
17%14%5%7%6%3445%5%29%
1906
21st to endDay
27%15%5%8%5%34345%20%
2772
January1st to 10thNight
18%13%5%8%6%46%5%5%5%26%
2649
11th to 20thNight
18%14%5%10%7%45%45%5%23%
2506
21st to endNight
12%13%5%9%7%46%5%46%30%
2574
February1st to 10thNight
13%15%5%9%8%46%5%5%6%25%
2340
11th to 20thNight
13%13%5%7%7%35%6%6%5%30%
2273
21st to endNight
14%11%37%6%445%5%7%32%
1848
March1st to 10thNight
13%9%48%7%45%5%5%6%35%
2020
11th to 20thNight
16%11%46%5%3445%5%36%
1979
21st to endNight
16%7%37%5%34446%41%
2152
April1st to 10thNight
17%9%46%5%346%5%6%36%
1800
11th to 20thNight
17%7%36%6%34446%39%
1775
21st to endNight
17%7%27%5%446%6%7%35%
1646
May1st to 10thNight
18%6%26%5%35%5%6%7%35%
1535
11th to 20thNight
12%5%345%345%7%7%45%
1415
21st to endNight
10%5%35%4345%5%8%49%
1550
June1st to 10thNight
14%5%36%5%36%47%8%39%
1440
11th to 20thNight
10%5%26%5%335%6%8%45%
1440
21st to endNight
11%6%35%6%45%46%8%42%
1440
July1st to 10thNight
6%425%5%45%45%9%53%
1440
11th to 20thNight
10%5%34435%46%9%48%
1440
21st to endNight
8%5%245%35%5%6%7%50%
1618
August1st to 10thNight
8%5%35%5%2447%8%49%
1611
11th to 20thNight
8%5%26%5%336%6%8%48%
1598
21st to endNight
9%5%25%436%5%6%8%48%
1916
September1st to 10thNight
11%5%35%5%35%5%6%8%45%
1800
11th to 20thNight
12%42342446%7%52%
1807
21st to endNight
15%6%35%434436%46%
2074
October1st to 10thNight
17%6%36%5%35%45%7%39%
2160
11th to 20thNight
18%8%37%8%35%45%6%33%
2160
21st to endNight
21%9%48%6%3445%7%29%
2389
November1st to 10thNight
17%7%35%5%3446%7%39%
2474
11th to 20thNight
17%9%36%6%46%5%6%7%32%
2660
21st to endNight
19%10%46%6%35%5%6%7%27%
2660
December1st to 10thNight
18%13%5%8%7%45%6%5%6%23%
2660
11th to 20thNight
17%14%48%6%445%5%6%27%
3288
21st to endNight
28%16%5%8%5%345%46%17%
4884

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 10thDay
57%6%13%16%7%
1518
11th to 20thDay
63%7%9%11%10%
1480
21st to endDay
61%7%10%12%8%1
1782
February1st to 10thDay
62%6%10%15%5%1
1620
11th to 20thDay
58%5%10%14%10%2
1582
21st to endDay
61%5%9%15%9%1
1408
March1st to 10thDay
53%6%15%15%9%2
1927
11th to 20thDay
51%5%11%18%12%2
1980
21st to endDay
50%6%7%19%15%4
2204
April1st to 10thDay
52%5%10%19%11%2
2160
11th to 20thDay
47%410%22%16%1
2134
21st to endDay
51%5%10%18%13%2
2330
May1st to 10thDay
48%6%9%19%15%3
2424
11th to 20thDay
40%8%11%24%16%2
2482
21st to endDay
38%7%15%23%14%2
2725
June1st to 10thDay
44%7%14%20%14%1
2520
11th to 20thDay
37%8%14%25%14%2
2520
21st to endDay
40%8%15%22%14%1
2520
July1st to 10thDay
31%9%14%28%17%2
2450
11th to 20thDay
36%9%16%28%10%1
2445
21st to endDay
37%11%16%25%11%1
2546
August1st to 10thDay
35%10%17%24%12%2
2314
11th to 20thDay
36%9%17%26%12%
2303
21st to endDay
35%9%15%28%11%2
2422
September1st to 10thDay
37%8%14%28%11%1
2160
11th to 20thDay
32%7%15%30%15%1
2151
21st to endDay
41%7%15%27%9%
1885
October1st to 10thDay
49%7%13%20%11%1
1800
11th to 20thDay
53%7%15%18%6%1
1800
21st to endDay
59%5%12%15%8%1
1965
November1st to 10thDay
46%7%16%20%11%1
1600
11th to 20thDay
50%7%17%15%10%1
1520
21st to endDay
58%8%13%14%7%
1520
December1st to 10thDay
62%6%13%13%5%
1520
11th to 20thDay
57%7%14%13%8%
1906
21st to endDay
67%6%11%12%4
2772
January1st to 10thNight
59%6%12%15%8%
2649
11th to 20thNight
63%7%10%13%7%1
2506
21st to endNight
56%6%10%17%11%1
2574
February1st to 10thNight
60%7%12%15%6%1
2340
11th to 20thNight
54%6%11%19%9%1
2275
21st to endNight
51%6%14%20%9%1
1848
March1st to 10thNight
50%5%12%19%12%2
2030
11th to 20thNight
49%5%11%21%13%1
1980
21st to endNight
45%49%22%16%4
2152
April1st to 10thNight
48%6%10%21%15%2
1800
11th to 20thNight
46%6%10%19%18%2
1775
21st to endNight
46%7%12%16%16%2
1646
May1st to 10thNight
46%6%11%18%16%3
1535
11th to 20thNight
36%7%11%25%18%4
1416
21st to endNight
33%7%15%23%19%4
1551
June1st to 10thNight
40%8%12%23%14%2
1440
11th to 20thNight
35%7%13%20%22%3
1440
21st to endNight
40%7%12%24%15%2
1440
July1st to 10thNight
28%9%11%27%24%2
1400
11th to 20thNight
33%7%13%28%18%1
1392
21st to endNight
32%7%13%33%13%2
1528
August1st to 10thNight
32%7%16%30%13%1
1600
11th to 20thNight
32%8%17%28%14%2
1598
21st to endNight
32%9%13%30%15%1
1916
September1st to 10thNight
36%8%15%26%14%1
1800
11th to 20thNight
31%7%12%32%18%1
1807
21st to endNight
41%6%11%29%13%1
2074
October1st to 10thNight
45%7%12%21%14%1
2160
11th to 20thNight
52%7%14%20%8%
2160
21st to endNight
54%7%13%15%11%1
2389
November1st to 10thNight
43%7%14%22%13%1
2474
11th to 20thNight
48%8%14%18%10%2
2660
21st to endNight
53%9%17%15%5%
2660
December1st to 10thNight
59%9%13%14%5%
2660
11th to 20thNight
57%7%13%15%7%1
3288
21st to endNight
68%7%11%10%3
4884

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 10thDay
23%22%32%16%6%1
180
11th to 20thDay
23%27%31%14%5%1
176
21st to endDay
20%26%33%17%41
264
February1st to 10thDay
28%30%32%9%2
240
11th to 20thDay
22%29%40%10%
240
21st to endDay
31%25%34%9%1
274
March1st to 10thDay
21%21%36%17%4
420
11th to 20thDay
25%18%34%19%3
420
21st to endDay
30%16%32%15%7%1
462
April1st to 10thDay
22%22%34%14%7%1
420
11th to 20thDay
26%16%29%17%8%5%
412
21st to endDay
27%14%35%17%5%1
420
May1st to 10thDay
23%14%31%18%8%5%
423
11th to 20thDay
18%11%32%25%10%4
447
21st to endDay
14%10%29%29%13%5%
485
June1st to 10thDay
17%12%33%26%11%2
450
11th to 20thDay
13%12%31%26%14%4
450
21st to endDay
17%10%29%27%13%4
450
July1st to 10thDay
9%7%25%35%20%5%
445
11th to 20thDay
14%6%28%29%16%8%
444
21st to endDay
9%8%32%34%11%6%
488
August1st to 10thDay
9%6%27%31%18%8%
446
11th to 20thDay
11%424%33%20%8%
439
21st to endDay
12%8%27%31%14%8%
495
September1st to 10thDay
11%8%32%24%17%9%
450
11th to 20thDay
12%6%26%26%19%11%
450
21st to endDay
13%12%30%24%16%6%
450
October1st to 10thDay
20%13%29%18%14%6%
450
11th to 20thDay
23%18%29%22%7%1
450
21st to endDay
29%19%26%20%6%
487
November1st to 10thDay
24%18%26%23%9%1
294
11th to 20thDay
22%21%38%16%31
180
21st to endDay
23%23%31%17%7%
180
December1st to 10thDay
26%19%34%14%6%
180
11th to 20thDay
27%28%32%10%21
180
21st to endDay
33%23%32%11%2
198
January1st to 10thNight
25%19%31%19%6%
760
11th to 20thNight
26%16%31%22%6%
727
21st to endNight
20%15%33%25%6%1
792
February1st to 10thNight
22%19%39%18%2
720
11th to 20thNight
20%18%37%20%4
703
21st to endNight
22%20%36%19%3
592
March1st to 10thNight
19%16%35%26%4
720
11th to 20thNight
21%17%34%23%41
720
21st to endNight
20%11%35%26%8%1
792
April1st to 10thNight
21%13%36%25%5%
720
11th to 20thNight
19%15%33%22%10%1
711
21st to endNight
20%10%31%28%11%
566
May1st to 10thNight
21%6%28%30%13%2
455
11th to 20thNight
13%6%33%35%13%
354
21st to endNight
11%5%30%36%17%1
389
June1st to 10thNight
13%336%33%14%1
360
11th to 20thNight
11%6%26%39%17%1
360
21st to endNight
13%6%26%38%17%1
360
July1st to 10thNight
6%426%44%19%1
350
11th to 20thNight
10%422%39%24%1
348
21st to endNight
8%324%45%18%2
438
August1st to 10thNight
10%316%40%28%2
537
11th to 20thNight
8%419%36%28%4
534
21st to endNight
11%426%34%23%2
728
September1st to 10thNight
13%5%24%34%22%3
720
11th to 20thNight
13%5%20%32%25%6%
720
21st to endNight
16%8%21%30%20%5%
720
October1st to 10thNight
20%8%29%24%18%2
720
11th to 20thNight
21%13%30%26%8%1
720
21st to endNight
26%12%31%24%6%
792
November1st to 10thNight
23%13%24%28%10%1
740
11th to 20thNight
21%16%33%22%6%2
760
21st to endNight
24%15%31%23%7%
760
December1st to 10thNight
27%18%33%18%4
760
11th to 20thNight
24%17%36%19%4
760
21st to endNight
30%16%33%17%3
836
Page generated at 2024-01-09 07:14:40. Version ac07

Copyright 2024 Attilla Danko


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