Fabreville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fabreville clear sky chart from 2005-11-06 to 2024-03-08.

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
33%
22739
13%
80855
9%
22654
40%
22654
16%
57147

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
19%
755
8%
4399
5%
737
25%
737
5%
3256
January11th to 20thNight
20%
755
9%
4393
5%
740
26%
740
7%
3156
January21st to endNight
26%
829
8%
4873
8%
814
34%
814
8%
3653
February1st to 10thNight
21%
760
11%
2507
6%
760
29%
760
12%
1926
February11th to 20thNight
24%
743
14%
2311
6%
740
34%
740
16%
1662
February21st to endNight
26%
628
16%
1884
7%
628
36%
628
16%
1388
March1st to 10thNight
25%
751
16%
2251
11%
751
33%
751
16%
1633
March11th to 20thNight
27%
720
15%
2087
8%
720
35%
720
17%
1516
March21st to endNight
32%
792
21%
1985
9%
792
40%
792
23%
1441
April1st to 10thNight
30%
720
16%
1800
5%
720
35%
720
20%
1349
April11th to 20thNight
31%
711
16%
1775
5%
711
36%
711
23%
1289
April21st to endNight
27%
576
17%
1656
8%
576
35%
576
20%
1179
May1st to 10thNight
31%
406
16%
1486
11%
406
40%
406
17%
986
May11th to 20thNight
37%
354
19%
1416
17%
354
50%
354
18%
898
May21st to endNight
37%
388
13%
1551
12%
388
49%
388
19%
971
June1st to 10thNight
40%
360
10%
1440
11%
360
49%
360
16%
981
June11th to 20thNight
43%
360
12%
1440
14%
360
50%
360
20%
888
June21st to endNight
42%
360
10%
1440
14%
360
47%
360
16%
951
July1st to 10thNight
52%
350
14%
1400
18%
350
59%
350
24%
812
July11th to 20thNight
56%
348
14%
1392
21%
348
59%
348
23%
821
July21st to endNight
56%
394
14%
1486
17%
372
59%
372
23%
875
August1st to 10thNight
61%
358
17%
1422
20%
356
64%
356
23%
837
August11th to 20thNight
55%
531
18%
1595
13%
531
59%
531
29%
1020
August21st to endNight
54%
792
18%
1980
9%
792
57%
792
32%
1336
September1st to 10thNight
53%
720
15%
1800
7%
720
55%
720
32%
1212
September11th to 20thNight
54%
720
20%
1872
13%
720
57%
720
34%
1200
September21st to endNight
46%
720
21%
1980
15%
720
51%
720
28%
1309
October1st to 10thNight
40%
720
19%
2104
13%
720
47%
720
23%
1439
October11th to 20thNight
34%
720
16%
2196
10%
720
41%
720
19%
1542
October21st to endNight
28%
792
12%
2574
8%
792
34%
792
15%
1882
November1st to 10thNight
30%
740
16%
2407
10%
740
39%
740
17%
1674
November11th to 20thNight
27%
760
17%
2550
11%
760
37%
760
17%
1801
November21st to endNight
23%
760
12%
2660
5%
760
31%
760
12%
1983
December1st to 10thNight
19%
760
9%
2660
5%
760
25%
760
9%
2090
December11th to 20thNight
17%
760
12%
3241
4%
759
27%
759
9%
2444
December21st to endNight
16%
826
7%
4842
4%
817
24%
817
6%
3747

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%47%6%35%5%5%7%33%
78356
Night
18%10%47%6%3445%6%32%
81204
TransparencyDay
50%7%12%20%10%1
78061
Night
53%6%11%19%10%1
81033
SeeingDay
21%9%27%25%13%4
13620
Night
23%7%28%31%11%1
22767

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
16%14%5%12%7%45%45%5%23%
2517
11th to 20thDay
15%12%6%9%7%3446%7%26%
2520
21st to endDay
15%15%49%7%46%6%5%7%24%
2772
February1st to 10thDay
15%14%5%10%7%36%45%5%27%
1672
11th to 20thDay
13%11%5%9%7%46%6%6%6%28%
1757
21st to endDay
18%14%5%7%7%35%446%27%
1570
March1st to 10thDay
16%11%5%9%8%36%446%30%
1867
11th to 20thDay
16%11%47%6%36%5%46%32%
1867
21st to endDay
19%9%47%5%34446%35%
2370
April1st to 10thDay
22%9%46%6%35%446%32%
2160
11th to 20thDay
20%8%26%6%34445%38%
2134
21st to endDay
22%10%46%6%34445%32%
2302
May1st to 10thDay
19%7%36%6%35%5%46%35%
2489
11th to 20thDay
18%6%35%5%35%45%7%38%
2478
21st to endDay
17%6%36%6%35%5%5%9%36%
2725
June1st to 10thDay
21%8%35%6%35%5%6%8%31%
2520
11th to 20thDay
15%5%36%6%35%5%5%9%38%
2520
21st to endDay
20%6%36%6%45%5%6%7%32%
2520
July1st to 10thDay
12%5%35%6%35%6%6%8%42%
2520
11th to 20thDay
12%425%5%35%7%8%10%38%
2520
21st to endDay
12%436%5%35%6%7%10%38%
2744
August1st to 10thDay
12%5%26%6%46%6%6%9%38%
2506
11th to 20thDay
10%5%36%5%45%5%7%8%42%
2284
21st to endDay
12%5%25%5%35%47%9%42%
2376
September1st to 10thDay
11%6%26%5%35%6%6%9%41%
2160
11th to 20thDay
14%5%244245%5%7%48%
2088
21st to endDay
16%5%26%5%3445%7%42%
1980
October1st to 10thDay
20%7%36%5%45%45%6%36%
1854
11th to 20thDay
18%8%36%8%5%6%6%5%7%29%
1764
21st to endDay
26%9%35%5%3445%6%29%
1782
November1st to 10thDay
18%8%46%5%26%5%5%7%35%
1671
11th to 20thDay
18%10%47%5%45%5%6%7%29%
1629
21st to endDay
22%10%46%6%46%5%5%6%26%
1520
December1st to 10thDay
25%11%8%8%6%345%5%5%20%
1520
11th to 20thDay
21%14%5%7%5%35%45%5%27%
1906
21st to endDay
28%14%49%6%3433320%
2772
January1st to 10thNight
17%14%6%9%6%45%45%5%23%
4429
11th to 20thNight
12%13%5%11%8%5%6%5%5%7%23%
4440
21st to endNight
16%16%5%9%8%44445%25%
4884
February1st to 10thNight
14%14%6%10%7%45%5%5%6%23%
2507
11th to 20thNight
14%10%5%8%7%35%5%5%7%30%
2309
21st to endNight
16%14%48%6%34445%32%
1884
March1st to 10thNight
17%12%5%8%6%35%446%30%
2241
11th to 20thNight
18%12%47%5%45%35%6%32%
2087
21st to endNight
18%9%37%5%3344438%
1985
April1st to 10thNight
24%9%45%5%3445%6%31%
1800
11th to 20thNight
23%6%36%5%34446%36%
1775
21st to endNight
22%8%36%5%345%5%5%34%
1656
May1st to 10thNight
22%7%37%434447%35%
1486
11th to 20thNight
20%5%35%5%36%45%6%39%
1415
21st to endNight
16%6%35%5%35%5%5%7%40%
1550
June1st to 10thNight
22%7%36%5%35%5%6%7%32%
1440
11th to 20thNight
16%6%36%5%335%6%8%39%
1440
21st to endNight
18%5%38%6%35%5%7%6%35%
1440
July1st to 10thNight
11%5%26%435%5%6%9%43%
1440
11th to 20thNight
12%436%5%45%6%6%11%40%
1440
21st to endNight
12%5%35%5%345%6%10%42%
1574
August1st to 10thNight
13%425%5%35%46%9%44%
1432
11th to 20thNight
13%5%26%5%345%6%7%44%
1595
21st to endNight
13%5%245%45%5%6%8%42%
1980
September1st to 10thNight
12%5%36%5%345%5%8%44%
1800
11th to 20thNight
15%6%345%23248%48%
1872
21st to endNight
17%5%26%4345%47%43%
1980
October1st to 10thNight
18%6%36%5%35%5%5%6%38%
2104
11th to 20thNight
20%8%37%6%4435%6%34%
2196
21st to endNight
23%9%47%5%45%45%431%
2574
November1st to 10thNight
19%9%36%5%35%5%5%7%33%
2407
11th to 20thNight
19%9%48%5%345%5%6%33%
2550
21st to endNight
23%13%47%6%3445%5%28%
2660
December1st to 10thNight
22%15%6%8%6%4445%6%21%
2660
11th to 20thNight
23%14%6%7%6%3444426%
3288
21st to endNight
29%15%5%8%42333422%
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
61%10%11%13%41
2518
11th to 20thDay
55%7%14%15%8%
2520
21st to endDay
59%7%13%14%5%
2772
February1st to 10thDay
59%410%20%5%2
1672
11th to 20thDay
55%7%11%16%9%1
1766
21st to endDay
59%410%16%10%2
1570
March1st to 10thDay
56%5%9%18%10%2
1870
11th to 20thDay
52%5%12%16%13%3
1867
21st to endDay
50%6%9%18%14%3
2370
April1st to 10thDay
55%5%8%18%13%2
2160
11th to 20thDay
48%6%7%22%15%2
2134
21st to endDay
53%6%9%17%12%4
2302
May1st to 10thDay
49%5%8%20%15%2
2489
11th to 20thDay
45%6%10%20%16%3
2482
21st to endDay
45%7%13%20%14%2
2725
June1st to 10thDay
50%7%11%19%12%2
2520
11th to 20thDay
43%7%10%23%14%3
2520
21st to endDay
51%7%11%20%10%1
2520
July1st to 10thDay
37%9%12%28%13%1
2450
11th to 20thDay
38%8%15%29%10%
2445
21st to endDay
40%8%16%27%9%
2591
August1st to 10thDay
41%9%16%26%9%
2492
11th to 20thDay
37%8%17%26%11%
2284
21st to endDay
37%7%15%26%14%
2376
September1st to 10thDay
38%7%15%27%13%1
2160
11th to 20thDay
34%7%12%32%15%1
2088
21st to endDay
41%6%14%28%10%1
1980
October1st to 10thDay
49%5%11%22%11%
1854
11th to 20thDay
54%8%12%20%7%
1764
21st to endDay
56%5%12%18%8%1
1782
November1st to 10thDay
48%6%14%22%8%1
1671
11th to 20thDay
53%6%12%17%11%1
1629
21st to endDay
57%9%14%15%6%
1520
December1st to 10thDay
67%5%11%13%4
1520
11th to 20thDay
60%5%13%17%5%
1906
21st to endDay
69%6%10%10%5%
2772
January1st to 10thNight
61%7%14%12%4
4429
11th to 20thNight
58%7%14%14%5%1
4440
21st to endNight
62%6%12%13%6%1
4884
February1st to 10thNight
62%5%11%16%6%1
2507
11th to 20thNight
53%5%11%21%9%1
2311
21st to endNight
56%5%8%17%13%1
1884
March1st to 10thNight
56%49%18%11%2
2251
11th to 20thNight
55%49%16%13%3
2088
21st to endNight
50%47%20%15%4
1985
April1st to 10thNight
54%48%19%14%2
1800
11th to 20thNight
51%47%21%15%2
1775
21st to endNight
51%49%18%13%4
1656
May1st to 10thNight
51%37%19%15%5%
1486
11th to 20thNight
46%5%8%18%18%4
1416
21st to endNight
43%7%11%20%17%2
1551
June1st to 10thNight
50%7%10%21%12%1
1440
11th to 20thNight
42%6%12%22%15%3
1440
21st to endNight
47%8%12%20%13%
1440
July1st to 10thNight
36%7%13%25%17%1
1400
11th to 20thNight
36%9%15%28%12%
1392
21st to endNight
36%9%18%25%12%
1486
August1st to 10thNight
37%7%17%26%12%
1422
11th to 20thNight
38%7%17%25%12%
1595
21st to endNight
37%8%15%26%13%1
1980
September1st to 10thNight
39%6%13%26%15%1
1800
11th to 20thNight
37%413%32%12%1
1872
21st to endNight
41%6%12%27%14%
1980
October1st to 10thNight
46%6%10%25%12%1
2104
11th to 20thNight
51%5%12%24%8%
2196
21st to endNight
56%5%13%17%9%1
2574
November1st to 10thNight
51%5%12%21%9%1
2407
11th to 20thNight
52%5%13%19%10%1
2550
21st to endNight
59%5%12%17%6%
2660
December1st to 10thNight
65%6%11%15%4
2660
11th to 20thNight
62%49%18%7%
3288
21st to endNight
67%5%9%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
26%11%27%26%11%
180
11th to 20thDay
29%13%28%22%7%1
180
21st to endDay
21%12%32%26%8%2
198
February1st to 10thDay
29%17%35%16%3
252
11th to 20thDay
22%12%39%23%4
364
21st to endDay
28%10%32%27%2
382
March1st to 10thDay
24%12%31%25%8%
448
11th to 20thDay
21%10%33%27%6%2
420
21st to endDay
27%10%30%21%10%3
462
April1st to 10thDay
25%13%28%21%9%3
420
11th to 20thDay
27%14%24%22%11%3
412
21st to endDay
28%11%28%21%10%3
420
May1st to 10thDay
23%9%31%25%10%3
423
11th to 20thDay
20%8%30%26%11%5%
447
21st to endDay
18%8%33%24%13%3
485
June1st to 10thDay
24%10%25%27%12%3
450
11th to 20thDay
17%9%22%32%16%4
450
21st to endDay
20%6%24%28%17%4
450
July1st to 10thDay
11%7%22%32%20%7%
445
11th to 20thDay
13%5%26%32%19%5%
444
21st to endDay
14%5%22%34%20%5%
488
August1st to 10thDay
15%321%33%21%8%
446
11th to 20thDay
11%5%19%30%23%13%
439
21st to endDay
14%7%24%24%22%9%
495
September1st to 10thDay
12%6%24%30%18%10%
450
11th to 20thDay
15%7%22%25%20%12%
450
21st to endDay
18%7%26%24%20%6%
450
October1st to 10thDay
22%9%27%22%14%6%
450
11th to 20thDay
21%11%31%22%13%2
432
21st to endDay
34%11%24%23%8%1
396
November1st to 10thDay
27%12%24%25%11%1
365
11th to 20thDay
22%14%34%20%8%1
289
21st to endDay
28%13%28%23%7%1
180
December1st to 10thDay
31%9%26%26%8%2
180
11th to 20thDay
25%13%37%19%41
180
21st to endDay
31%16%29%17%7%1
198
January1st to 10thNight
26%10%30%28%5%
760
11th to 20thNight
25%9%34%26%5%
760
21st to endNight
19%7%36%29%8%
836
February1st to 10thNight
21%7%36%28%6%1
760
11th to 20thNight
21%10%36%28%5%
743
21st to endNight
24%8%32%32%4
628
March1st to 10thNight
24%10%30%30%6%
751
11th to 20thNight
27%8%31%26%8%
720
21st to endNight
23%7%28%33%8%1
792
April1st to 10thNight
27%8%27%31%6%
720
11th to 20thNight
26%9%29%28%7%1
711
21st to endNight
27%8%29%27%9%
576
May1st to 10thNight
22%6%31%30%8%2
406
11th to 20thNight
23%5%28%36%8%1
354
21st to endNight
18%5%32%35%10%1
389
June1st to 10thNight
25%423%34%13%1
360
11th to 20thNight
19%426%36%14%1
360
21st to endNight
18%5%24%36%16%1
360
July1st to 10thNight
11%326%41%17%1
350
11th to 20thNight
12%320%47%17%1
348
21st to endNight
13%318%46%20%1
394
August1st to 10thNight
16%212%46%23%1
358
11th to 20thNight
15%218%37%26%2
531
21st to endNight
16%320%36%23%2
792
September1st to 10thNight
14%322%42%18%1
720
11th to 20thNight
18%418%37%21%2
720
21st to endNight
19%325%32%19%2
720
October1st to 10thNight
21%6%27%33%13%1
720
11th to 20thNight
23%7%27%31%11%1
720
21st to endNight
28%7%30%29%6%
792
November1st to 10thNight
25%9%29%28%9%
740
11th to 20thNight
24%9%33%24%10%1
760
21st to endNight
30%10%28%24%8%1
760
December1st to 10thNight
30%8%31%24%6%
760
11th to 20thNight
29%10%33%21%6%1
760
21st to endNight
33%11%30%21%5%1
836
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