Fabreville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fabreville clear sky chart from 2005-11-05 to 2018-02-13.

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
34%
15224
14%
48795
9%
15193
40%
15193
18%
34587

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
20%
780
9%
2716
5%
776
25%
776
10%
2121
January16th to endNight
24%
832
10%
2912
6%
832
30%
832
12%
2156
February1st to 15thNight
24%
753
9%
2470
6%
750
29%
750
11%
1923
February16th to endNight
27%
631
14%
1893
7%
631
37%
631
15%
1417
March1st to 15thNight
27%
720
14%
2160
10%
720
33%
720
15%
1607
March16th to endNight
36%
768
19%
1995
10%
768
42%
768
24%
1406
April1st to 15thNight
31%
718
16%
1796
6%
718
36%
718
20%
1347
April16th to endNight
31%
624
17%
1704
6%
624
38%
624
23%
1203
May1st to 15thNight
33%
390
16%
1470
13%
390
42%
390
17%
977
May16th to endNight
40%
374
13%
1497
13%
374
48%
374
17%
988
June1st to 15thNight
40%
360
9%
1440
10%
360
46%
360
15%
1000
June16th to endNight
47%
360
8%
1440
11%
360
50%
360
18%
924
July1st to 15thNight
55%
340
13%
1360
19%
340
59%
340
25%
776
July16th to endNight
58%
376
13%
1418
17%
354
61%
354
25%
821
August1st to 15thNight
59%
359
15%
1430
17%
357
63%
357
22%
869
August16th to endNight
58%
762
20%
1908
11%
762
60%
762
37%
1222
September1st to 15thNight
54%
720
14%
1800
8%
720
55%
720
30%
1245
September16th to endNight
52%
717
21%
1968
15%
717
56%
717
33%
1245
October1st to 15thNight
38%
720
18%
2124
11%
720
47%
720
23%
1443
October16th to endNight
30%
768
12%
2460
9%
768
35%
768
16%
1787
November1st to 15thNight
31%
760
17%
2472
11%
760
39%
760
18%
1739
November16th to endNight
26%
780
13%
2720
9%
780
33%
780
13%
2000
December1st to 15thNight
21%
780
9%
2730
4%
780
27%
780
10%
2110
December16th to endNight
16%
832
11%
2912
4%
832
25%
832
10%
2261

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%7%36%5%35%45%6%33%
49262
Night
18%9%36%5%34446%32%
48964
Cloud CoverDay
18%8%35%5%3445%6%33%
49271
Night
19%9%36%5%24446%32%
48970
TransparencyDay
49%5%12%20%10%1
48949
Night
52%5%11%19%10%1
48795
SeeingDay
21%5%24%26%16%5%
5975
Night
23%5%26%31%11%
15225

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
21%13%5%8%7%35%43322%
1552
16th to endDay
13%12%5%8%7%25%446%27%
1664
February1st to 15thDay
14%13%5%10%6%46%5%35%24%
1657
16th to endDay
16%13%5%7%7%34345%28%
1580
March1st to 15thDay
18%10%48%7%35%445%27%
1790
16th to endDay
18%8%35%424336%38%
2226
April1st to 15thDay
22%9%345%34345%32%
2152
16th to endDay
19%7%25%5%2344438%
2256
May1st to 15thDay
20%6%35%6%36%446%33%
2491
16th to endDay
19%6%35%5%35%45%8%34%
2618
June1st to 15thDay
21%7%246%3445%8%31%
2520
16th to endDay
18%5%35%5%36%5%5%8%31%
2520
July1st to 15thDay
12%425%5%35%5%6%8%39%
2520
16th to endDay
12%425%5%35%6%7%10%37%
2654
August1st to 15thDay
12%5%27%5%36%5%6%9%35%
2508
16th to endDay
9%414435%47%8%46%
2292
September1st to 15thDay
15%5%244245%48%41%
2160
16th to endDay
14%414423247%50%
1992
October1st to 15thDay
20%6%25%445%446%35%
1836
16th to endDay
23%8%35%6%33445%28%
1764
November1st to 15thDay
17%8%46%4345%5%6%32%
1716
16th to endDay
23%9%445%35%446%29%
1570
December1st to 15thDay
24%11%6%7%5%245%5%5%20%
1560
16th to endDay
25%13%46%5%2444422%
1664
January1st to 15thNight
18%13%6%9%5%3435%5%22%
2716
16th to endNight
14%13%5%8%7%44445%27%
2912
February1st to 15thNight
14%14%6%10%7%35%5%45%22%
2468
16th to endNight
16%13%47%6%34445%29%
1893
March1st to 15thNight
20%11%47%5%35%345%28%
2147
16th to endNight
16%9%46%5%2334439%
1995
April1st to 15thNight
25%7%45%5%23336%32%
1796
16th to endNight
22%6%25%433445%37%
1704
May1st to 15thNight
22%6%36%5%24336%35%
1470
16th to endNight
20%5%345%35%45%7%34%
1495
June1st to 15thNight
24%7%35%43446%7%30%
1440
16th to endNight
17%426%5%245%7%8%35%
1440
July1st to 15thNight
11%324426%6%5%10%41%
1440
16th to endNight
11%4244345%6%11%41%
1514
August1st to 15thNight
13%5%15%5%2446%9%40%
1440
16th to endNight
12%41343445%8%47%
1908
September1st to 15thNight
15%5%25%434347%42%
1800
16th to endNight
16%424323337%48%
1968
October1st to 15thNight
17%5%35%43445%6%38%
2124
16th to endNight
24%8%36%434345%31%
2460
November1st to 15thNight
20%8%36%5%24446%33%
2472
16th to endNight
22%12%47%5%2334428%
2720
December1st to 15thNight
23%13%5%7%5%33345%23%
2730
16th to endNight
23%15%47%5%2334423%
2912

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
22%13%5%8%7%3443322%
1552
16th to endDay
14%13%47%6%35%447%27%
1664
February1st to 15thDay
14%13%5%9%7%46%445%24%
1657
16th to endDay
17%13%5%6%8%25%345%27%
1580
March1st to 15thDay
18%10%5%7%7%3445%427%
1800
16th to endDay
19%8%36%424345%37%
2225
April1st to 15thDay
22%9%35%6%24435%32%
2152
16th to endDay
20%7%25%5%2344438%
2256
May1st to 15thDay
21%6%25%5%35%45%6%33%
2491
16th to endDay
19%6%25%5%345%5%8%33%
2618
June1st to 15thDay
22%7%25%5%345%47%31%
2520
16th to endDay
18%5%35%5%35%5%6%8%32%
2520
July1st to 15thDay
12%5%25%5%35%5%6%9%39%
2520
16th to endDay
11%425%5%25%6%7%9%37%
2654
August1st to 15thDay
12%6%26%6%35%5%6%9%35%
2508
16th to endDay
9%4144345%6%9%46%
2292
September1st to 15thDay
16%5%2443445%8%41%
2160
16th to endDay
14%323423347%49%
1992
October1st to 15thDay
20%6%346%35%346%35%
1836
16th to endDay
24%9%35%6%33445%29%
1764
November1st to 15thDay
17%9%45%4335%5%6%31%
1716
16th to endDay
23%9%35%6%245%4429%
1570
December1st to 15thDay
25%13%47%5%35%45%5%20%
1560
16th to endDay
26%13%47%5%35%33421%
1664
January1st to 15thNight
19%14%6%9%6%3435%5%22%
2716
16th to endNight
14%13%5%8%7%35%44427%
2912
February1st to 15thNight
14%14%6%10%6%35%5%45%21%
2461
16th to endNight
17%11%49%5%3444429%
1893
March1st to 15thNight
21%11%46%6%34345%28%
2160
16th to endNight
17%9%35%5%2333439%
1995
April1st to 15thNight
25%9%34433345%31%
1796
16th to endNight
22%6%25%423445%36%
1704
May1st to 15thNight
21%6%46%6%13345%36%
1470
16th to endNight
20%6%25%5%25%46%6%34%
1495
June1st to 15thNight
25%6%345%245%5%7%30%
1440
16th to endNight
17%5%245%336%7%8%35%
1440
July1st to 15thNight
11%3245%26%47%10%41%
1440
16th to endNight
12%325%425%47%9%42%
1514
August1st to 15thNight
13%4245%345%5%10%39%
1440
16th to endNight
12%41442445%8%46%
1908
September1st to 15thNight
16%435%424347%42%
1800
16th to endNight
17%423413347%47%
1968
October1st to 15thNight
17%7%26%425%45%6%38%
2124
16th to endNight
25%7%37%434345%30%
2460
November1st to 15thNight
21%8%36%5%24445%33%
2472
16th to endNight
23%12%46%42443428%
2720
December1st to 15thNight
23%15%5%7%5%33345%23%
2730
16th to endNight
23%16%47%5%2434423%
2912

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
66%5%7%14%6%
1553
16th to endDay
56%5%13%16%7%
1664
February1st to 15thDay
61%5%9%18%3
1659
16th to endDay
58%410%15%9%1
1580
March1st to 15thDay
58%411%16%7%1
1800
16th to endDay
47%410%18%15%3
2226
April1st to 15thDay
54%47%19%12%2
2152
16th to endDay
48%48%19%15%3
2256
May1st to 15thDay
51%5%8%18%14%2
2491
16th to endDay
47%6%11%20%12%1
2622
June1st to 15thDay
51%6%10%19%10%1
2520
16th to endDay
49%7%10%22%9%1
2520
July1st to 15thDay
38%8%13%26%12%
2371
16th to endDay
39%8%17%25%8%
2487
August1st to 15thDay
43%8%16%23%8%
2494
16th to endDay
32%7%17%28%13%
2292
September1st to 15thDay
39%5%13%26%12%
2160
16th to endDay
35%411%34%12%
1992
October1st to 15thDay
50%411%24%9%
1836
16th to endDay
56%5%12%17%6%
1764
November1st to 15thDay
49%6%13%20%8%
1716
16th to endDay
55%6%12%17%7%
1570
December1st to 15thDay
63%5%13%13%3
1560
16th to endDay
65%410%11%7%
1664
January1st to 15thNight
63%5%10%14%4
2716
16th to endNight
59%411%16%8%
2912
February1st to 15thNight
63%5%11%16%4
2470
16th to endNight
57%49%17%10%
1893
March1st to 15thNight
58%38%18%9%1
2160
16th to endNight
48%48%18%16%3
1995
April1st to 15thNight
55%25%19%14%1
1796
16th to endNight
49%48%18%15%4
1704
May1st to 15thNight
51%37%17%15%4
1470
16th to endNight
47%6%9%20%13%1
1497
June1st to 15thNight
52%6%10%19%10%
1440
16th to endNight
43%8%12%19%14%
1440
July1st to 15thNight
35%7%13%27%15%
1360
16th to endNight
35%7%18%23%13%
1418
August1st to 15thNight
39%7%17%23%11%
1430
16th to endNight
34%5%16%29%13%
1908
September1st to 15thNight
42%5%12%25%13%1
1800
16th to endNight
37%412%30%14%
1968
October1st to 15thNight
45%5%10%26%11%
2124
16th to endNight
55%413%19%6%
2460
November1st to 15thNight
52%412%19%8%2
2472
16th to endNight
58%411%18%6%
2720
December1st to 15thNight
63%5%12%15%4
2730
16th to endNight
64%49%14%6%
2912

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
22%12%21%32%12%
90
16th to endDay
29%9%32%19%7%2
96
February1st to 15thDay
30%13%30%23%1
120
16th to endDay
27%330%31%6%
239
March1st to 15thDay
22%9%28%31%7%
270
16th to endDay
24%427%26%12%4
288
April1st to 15thDay
28%9%27%21%9%3
270
16th to endDay
20%6%28%23%16%4
270
May1st to 15thDay
27%426%22%11%7%
288
16th to endDay
21%6%29%21%16%5%
331
June1st to 15thDay
27%6%22%27%12%3
315
16th to endDay
17%420%35%19%3
315
July1st to 15thDay
12%5%21%30%21%7%
305
16th to endDay
13%215%34%27%6%
326
August1st to 15thDay
14%116%30%25%11%
313
16th to endDay
9%319%28%23%16%
332
September1st to 15thDay
14%318%26%22%14%
315
16th to endDay
14%421%20%25%13%
314
October1st to 15thDay
19%5%27%22%20%5%
315
16th to endDay
29%8%25%23%11%
297
November1st to 15thDay
25%6%23%29%13%1
280
16th to endDay
30%10%26%23%11%
100
December1st to 15thDay
28%331%24%10%2
90
16th to endDay
33%11%34%15%5%
96
January1st to 15thNight
24%10%30%28%6%
780
16th to endNight
20%8%35%27%7%
832
February1st to 15thNight
21%6%34%29%7%
753
16th to endNight
22%7%31%30%6%
631
March1st to 15thNight
28%6%29%29%5%
720
16th to endNight
21%5%27%34%10%
768
April1st to 15thNight
28%6%25%33%5%
718
16th to endNight
25%7%29%26%10%
624
May1st to 15thNight
23%429%30%9%1
390
16th to endNight
22%425%37%9%
375
June1st to 15thNight
28%320%34%12%
360
16th to endNight
17%223%41%14%
360
July1st to 15thNight
10%224%39%22%1
340
16th to endNight
11%217%47%19%1
376
August1st to 15thNight
16%211%44%23%1
359
16th to endNight
15%118%36%26%1
762
September1st to 15thNight
18%217%41%18%1
720
16th to endNight
19%220%30%24%2
717
October1st to 15thNight
20%427%33%13%
720
16th to endNight
28%6%27%29%8%
768
November1st to 15thNight
26%5%29%27%11%
760
16th to endNight
28%8%26%23%11%1
780
December1st to 15thNight
31%7%29%26%5%
780
16th to endNight
31%7%32%22%41
832
Page generated at 2018-02-13 20:46:07. Version ac04

Copyright 2018 A. Danko


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