Lorraine
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lorraine clear sky chart from 2005-11-06 to 2024-01-16.

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%
22542
15%
74754
9%
22501
40%
22501
18%
52150

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
18%
760
10%
2649
5%
757
25%
757
10%
2055
January11th to 20thNight
21%
744
11%
2602
6%
744
27%
744
11%
1973
January21st to endNight
26%
792
13%
2772
8%
792
34%
792
15%
1957
February1st to 10thNight
19%
720
12%
2378
5%
720
28%
720
12%
1817
February11th to 20thNight
23%
703
15%
2186
7%
700
35%
700
16%
1562
February21st to endNight
25%
592
16%
1776
8%
592
36%
592
17%
1295
March1st to 10thNight
25%
720
16%
2160
11%
720
33%
720
16%
1571
March11th to 20thNight
28%
720
16%
2089
7%
720
36%
720
18%
1505
March21st to endNight
31%
792
21%
1985
9%
792
39%
792
24%
1434
April1st to 10thNight
28%
720
17%
1800
5%
720
34%
720
20%
1345
April11th to 20thNight
31%
711
17%
1775
5%
711
37%
711
23%
1282
April21st to endNight
27%
575
18%
1655
7%
575
36%
575
21%
1168
May1st to 10thNight
30%
404
16%
1484
11%
404
40%
404
17%
982
May11th to 20thNight
34%
354
20%
1416
17%
354
48%
354
19%
893
May21st to endNight
33%
389
14%
1551
11%
388
45%
388
20%
963
June1st to 10thNight
38%
360
10%
1440
11%
360
47%
360
17%
958
June11th to 20thNight
41%
360
12%
1440
13%
360
49%
360
20%
881
June21st to endNight
42%
360
10%
1440
13%
360
48%
360
17%
935
July1st to 10thNight
51%
350
14%
1400
18%
350
60%
350
25%
789
July11th to 20thNight
55%
348
14%
1392
21%
348
58%
348
25%
807
July21st to endNight
55%
394
14%
1486
17%
372
59%
372
23%
857
August1st to 10thNight
60%
358
17%
1422
20%
356
63%
356
23%
832
August11th to 20thNight
55%
526
18%
1590
14%
526
58%
526
30%
996
August21st to endNight
52%
792
18%
1980
10%
792
55%
792
33%
1320
September1st to 10thNight
52%
720
16%
1800
7%
720
55%
720
34%
1193
September11th to 20thNight
54%
720
21%
1872
13%
720
57%
720
35%
1186
September21st to endNight
45%
720
22%
1980
15%
720
51%
720
29%
1292
October1st to 10thNight
39%
720
21%
2103
13%
720
48%
720
24%
1416
October11th to 20thNight
33%
720
17%
2198
10%
720
42%
720
20%
1529
October21st to endNight
28%
792
12%
2574
8%
792
35%
792
16%
1846
November1st to 10thNight
29%
740
18%
2407
10%
740
40%
740
18%
1657
November11th to 20thNight
27%
760
19%
2550
12%
760
38%
760
18%
1774
November21st to endNight
23%
760
13%
2660
6%
760
33%
760
13%
1947
December1st to 10thNight
20%
760
10%
2660
5%
760
27%
760
10%
2058
December11th to 20thNight
18%
760
14%
3241
6%
759
29%
759
10%
2399
December21st to endNight
17%
826
8%
4841
4%
817
26%
817
6%
3676

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
17%9%37%6%35%5%5%7%34%
74785
Night
18%10%47%6%3445%6%33%
75016
TransparencyDay
50%412%21%11%1
74490
Night
52%411%21%11%1
74845
SeeingDay
22%9%27%25%12%4
13453
Night
23%7%28%31%11%1
22552

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
18%16%5%10%7%45%44424%
1517
11th to 20thDay
18%14%5%8%7%34446%28%
1480
21st to endDay
11%13%49%7%46%6%5%6%29%
1584
February1st to 10thDay
14%15%5%9%6%35%5%46%27%
1580
11th to 20thDay
14%12%5%9%6%46%5%5%6%28%
1662
21st to endDay
18%14%7%8%6%3445%428%
1480
March1st to 10thDay
16%11%49%7%45%45%6%29%
1797
11th to 20thDay
16%12%36%7%25%446%33%
1867
21st to endDay
19%9%47%6%34445%36%
2371
April1st to 10thDay
21%10%47%6%34445%32%
2160
11th to 20thDay
20%7%35%6%43445%37%
2134
21st to endDay
21%10%47%6%245%45%32%
2304
May1st to 10thDay
19%7%46%6%25%5%5%7%34%
2492
11th to 20thDay
19%6%25%6%4446%7%37%
2478
21st to endDay
17%6%36%6%36%5%6%8%35%
2725
June1st to 10thDay
20%8%36%5%45%5%5%8%30%
2520
11th to 20thDay
15%5%46%6%45%5%6%8%38%
2520
21st to endDay
19%7%37%6%45%5%6%8%30%
2520
July1st to 10thDay
11%6%25%6%37%6%6%8%40%
2520
11th to 20thDay
12%5%25%6%36%7%7%10%37%
2520
21st to endDay
11%5%36%5%35%7%8%10%37%
2744
August1st to 10thDay
11%6%36%7%36%6%7%9%36%
2506
11th to 20thDay
9%5%37%6%35%5%7%8%40%
2289
21st to endDay
12%6%245%346%6%8%43%
2376
September1st to 10thDay
12%5%25%5%35%6%6%9%41%
2160
11th to 20thDay
14%5%2443445%6%49%
2088
21st to endDay
15%6%35%5%34448%42%
1980
October1st to 10thDay
20%6%36%5%3445%7%36%
1854
11th to 20thDay
19%7%36%9%45%5%6%7%28%
1761
21st to endDay
25%9%47%5%3345%6%30%
1782
November1st to 10thDay
17%9%46%4445%5%8%35%
1671
11th to 20thDay
18%11%47%5%35%45%7%31%
1625
21st to endDay
22%10%37%5%46%5%5%7%27%
1520
December1st to 10thDay
24%12%6%10%6%3444422%
1520
11th to 20thDay
22%13%5%7%5%3445%5%28%
1906
21st to endDay
27%16%49%5%3333421%
2772
January1st to 10thNight
17%16%6%10%8%35%445%21%
2649
11th to 20thNight
17%15%6%8%7%35%44426%
2602
21st to endNight
12%12%5%9%8%3445%6%31%
2772
February1st to 10thNight
14%14%6%11%8%46%5%5%6%23%
2378
11th to 20thNight
15%10%49%7%45%5%5%6%31%
2184
21st to endNight
16%13%5%9%6%25%445%31%
1776
March1st to 10thNight
17%13%5%7%6%35%446%30%
2150
11th to 20thNight
17%13%47%5%3445%6%32%
2089
21st to endNight
17%10%46%6%3444438%
1985
April1st to 10thNight
24%9%37%5%345%46%31%
1800
11th to 20thNight
22%7%36%5%34446%37%
1775
21st to endNight
21%9%35%5%245%45%35%
1655
May1st to 10thNight
20%8%46%6%35%446%35%
1484
11th to 20thNight
19%6%36%5%345%5%6%38%
1415
21st to endNight
16%6%26%6%35%5%5%7%40%
1550
June1st to 10thNight
20%7%36%5%35%47%8%32%
1440
11th to 20thNight
17%6%36%5%345%6%7%39%
1440
21st to endNight
17%6%46%5%35%5%5%8%35%
1440
July1st to 10thNight
10%435%6%346%7%9%43%
1440
11th to 20thNight
11%5%346%36%6%7%9%40%
1440
21st to endNight
11%5%35%6%345%7%9%41%
1574
August1st to 10thNight
12%5%25%5%36%45%9%43%
1432
11th to 20thNight
12%5%36%5%345%6%8%43%
1590
21st to endNight
13%5%25%5%345%6%9%42%
1980
September1st to 10thNight
11%5%36%6%35%5%5%7%45%
1800
11th to 20thNight
15%435%423348%49%
1872
21st to endNight
16%5%26%43445%7%44%
1980
October1st to 10thNight
18%6%36%5%34446%40%
2103
11th to 20thNight
20%8%47%5%3435%6%35%
2198
21st to endNight
22%9%47%6%3445%5%31%
2574
November1st to 10thNight
19%9%36%6%35%5%5%7%33%
2407
11th to 20thNight
19%9%47%5%345%5%6%34%
2550
21st to endNight
22%12%47%7%34445%29%
2660
December1st to 10thNight
21%14%6%9%6%445%46%22%
2660
11th to 20thNight
23%13%5%8%5%34445%27%
3288
21st to endNight
28%15%5%9%5%2334422%
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
65%49%16%6%
1518
11th to 20thDay
60%49%15%11%1
1480
21st to endDay
54%5%11%18%11%1
1584
February1st to 10thDay
59%310%19%7%2
1580
11th to 20thDay
57%412%16%9%1
1671
21st to endDay
60%29%17%10%2
1480
March1st to 10thDay
56%310%17%11%2
1800
11th to 20thDay
53%312%15%14%3
1867
21st to endDay
51%49%18%14%4
2371
April1st to 10thDay
55%47%19%12%2
2160
11th to 20thDay
49%37%23%15%2
2134
21st to endDay
55%38%18%12%4
2304
May1st to 10thDay
50%37%22%15%2
2492
11th to 20thDay
46%410%21%15%3
2482
21st to endDay
46%5%13%19%15%2
2725
June1st to 10thDay
52%5%10%20%12%2
2520
11th to 20thDay
44%5%10%24%14%3
2520
21st to endDay
52%5%13%19%10%1
2520
July1st to 10thDay
39%6%14%28%12%1
2450
11th to 20thDay
40%5%17%27%10%
2445
21st to endDay
40%6%18%27%9%
2591
August1st to 10thDay
43%5%18%25%9%
2492
11th to 20thDay
39%5%19%26%10%
2289
21st to endDay
37%5%16%27%14%1
2376
September1st to 10thDay
38%6%14%28%13%1
2160
11th to 20thDay
35%5%12%32%15%1
2088
21st to endDay
42%414%27%11%1
1980
October1st to 10thDay
49%412%23%12%
1854
11th to 20thDay
54%5%14%20%7%
1761
21st to endDay
56%313%19%8%1
1782
November1st to 10thDay
48%5%14%23%9%1
1671
11th to 20thDay
53%5%11%19%11%
1625
21st to endDay
57%5%15%16%6%1
1520
December1st to 10thDay
67%311%14%5%
1520
11th to 20thDay
59%411%19%7%
1906
21st to endDay
69%312%11%6%
2772
January1st to 10thNight
65%49%16%6%
2649
11th to 20thNight
62%410%14%8%1
2602
21st to endNight
54%5%10%18%12%1
2772
February1st to 10thNight
62%48%17%8%1
2378
11th to 20thNight
54%411%21%9%1
2186
21st to endNight
56%49%17%14%1
1776
March1st to 10thNight
57%39%17%11%2
2160
11th to 20thNight
54%39%17%13%3
2090
21st to endNight
50%38%20%15%4
1985
April1st to 10thNight
53%5%7%19%15%2
1800
11th to 20thNight
50%46%22%15%2
1775
21st to endNight
51%47%20%13%4
1655
May1st to 10thNight
52%27%19%15%5%
1484
11th to 20thNight
47%48%19%18%4
1416
21st to endNight
44%5%11%20%17%2
1551
June1st to 10thNight
50%5%10%22%13%1
1440
11th to 20thNight
43%5%11%23%15%3
1440
21st to endNight
47%6%12%20%14%
1440
July1st to 10thNight
36%6%14%27%17%1
1400
11th to 20thNight
38%5%15%29%12%
1392
21st to endNight
38%6%18%26%12%
1486
August1st to 10thNight
39%5%17%26%12%
1422
11th to 20thNight
38%5%17%27%12%
1590
21st to endNight
39%5%15%28%13%1
1980
September1st to 10thNight
38%5%14%27%15%1
1800
11th to 20thNight
36%413%34%12%1
1872
21st to endNight
41%5%11%29%14%
1980
October1st to 10thNight
46%5%10%25%14%1
2103
11th to 20thNight
51%412%25%9%
2198
21st to endNight
56%312%19%9%1
2574
November1st to 10thNight
51%412%23%9%1
2407
11th to 20thNight
51%412%20%10%1
2550
21st to endNight
59%411%19%8%
2660
December1st to 10thNight
64%5%11%16%4
2660
11th to 20thNight
61%38%19%7%1
3288
21st to endNight
67%39%15%5%
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%10%28%30%8%
180
11th to 20thDay
27%12%32%22%42
170
21st to endDay
20%12%32%27%7%2
176
February1st to 10thDay
33%18%34%14%2
222
11th to 20thDay
23%11%38%24%4
329
21st to endDay
29%12%31%24%4
346
March1st to 10thDay
24%11%33%24%8%
420
11th to 20thDay
22%12%33%25%5%1
420
21st to endDay
27%10%31%20%10%3
462
April1st to 10thDay
28%13%27%22%8%3
420
11th to 20thDay
29%13%23%23%10%2
412
21st to endDay
27%12%30%20%8%3
420
May1st to 10thDay
23%10%32%24%9%2
423
11th to 20thDay
21%6%32%25%12%3
447
21st to endDay
17%11%33%24%12%3
485
June1st to 10thDay
24%10%26%26%11%3
450
11th to 20thDay
16%11%24%30%15%3
450
21st to endDay
22%6%25%28%16%4
450
July1st to 10thDay
13%5%22%34%20%6%
445
11th to 20thDay
15%5%26%32%19%4
444
21st to endDay
13%6%22%37%18%5%
488
August1st to 10thDay
14%422%31%22%6%
446
11th to 20thDay
11%420%33%19%13%
439
21st to endDay
15%7%24%25%21%8%
495
September1st to 10thDay
13%426%28%19%9%
450
11th to 20thDay
16%7%22%25%18%12%
450
21st to endDay
18%7%26%24%17%7%
450
October1st to 10thDay
22%9%26%22%15%5%
450
11th to 20thDay
21%11%30%23%12%3
430
21st to endDay
33%11%24%24%8%1
396
November1st to 10thDay
27%13%24%24%11%1
365
11th to 20thDay
26%12%34%19%8%1
285
21st to endDay
31%12%26%22%8%1
180
December1st to 10thDay
29%11%24%27%8%2
180
11th to 20thDay
26%12%37%19%41
180
21st to endDay
32%16%28%16%8%1
198
January1st to 10thNight
25%11%30%28%6%
760
11th to 20thNight
25%10%32%27%7%
744
21st to endNight
17%8%35%30%8%1
792
February1st to 10thNight
22%8%36%28%5%1
720
11th to 20thNight
22%10%35%27%5%
703
21st to endNight
24%8%32%31%4
592
March1st to 10thNight
25%9%31%30%5%
720
11th to 20thNight
26%9%30%27%8%
720
21st to endNight
22%8%30%32%8%1
792
April1st to 10thNight
26%10%27%30%6%
720
11th to 20thNight
25%9%29%29%7%1
711
21st to endNight
28%8%30%26%8%
575
May1st to 10thNight
24%5%31%30%8%2
404
11th to 20thNight
24%330%35%8%1
354
21st to endNight
18%5%37%31%9%1
389
June1st to 10thNight
27%323%35%12%
360
11th to 20thNight
19%429%34%14%1
360
21st to endNight
19%424%35%16%1
360
July1st to 10thNight
10%427%42%15%1
350
11th to 20thNight
12%321%46%18%
348
21st to endNight
12%319%46%19%1
394
August1st to 10thNight
15%412%44%24%1
358
11th to 20thNight
14%218%37%25%3
526
21st to endNight
16%222%36%22%2
792
September1st to 10thNight
14%322%42%18%1
720
11th to 20thNight
17%5%18%38%21%2
720
21st to endNight
18%427%32%18%3
720
October1st to 10thNight
21%6%26%34%12%1
720
11th to 20thNight
24%7%27%30%12%1
720
21st to endNight
28%7%30%28%7%
792
November1st to 10thNight
24%10%29%28%9%
740
11th to 20thNight
24%8%32%25%10%1
760
21st to endNight
29%11%28%24%8%
760
December1st to 10thNight
30%9%29%24%7%
760
11th to 20thNight
27%11%31%24%6%1
760
21st to endNight
34%10%29%20%6%
836
Page generated at 2024-01-13 09:37:58. Version ac07

Copyright 2024 Attilla Danko


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