Fergus
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fergus clear sky chart from 2005-11-05 to 2017-09-14.

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%
14835
14%
46554
8%
14798
38%
14798
18%
32906

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
10%
716
8%
2435
2%
716
17%
716
7%
1990
January16th to endNight
14%
768
9%
2496
3%
768
22%
768
8%
2030
February1st to 15thNight
15%
702
8%
2287
2%
701
22%
701
9%
1822
February16th to endNight
19%
631
11%
1993
3%
631
27%
631
11%
1513
March1st to 15thNight
20%
720
13%
1994
6%
720
27%
720
16%
1508
March16th to endNight
30%
768
20%
2112
10%
768
39%
768
23%
1449
April1st to 15thNight
25%
706
15%
1832
6%
706
30%
706
20%
1344
April16th to endNight
36%
540
20%
1620
9%
540
44%
540
24%
1060
May1st to 15thNight
40%
531
17%
1611
11%
531
47%
531
24%
1076
May16th to endNight
44%
374
17%
1497
12%
374
56%
374
25%
844
June1st to 15thNight
45%
360
14%
1415
12%
360
56%
360
23%
836
June16th to endNight
46%
360
15%
1260
15%
360
54%
360
27%
737
July1st to 15thNight
62%
340
18%
1240
22%
340
67%
340
37%
628
July16th to endNight
57%
535
15%
1566
12%
502
61%
502
32%
934
August1st to 15thNight
62%
539
17%
1609
12%
536
66%
536
35%
940
August16th to endNight
58%
600
23%
1746
16%
600
62%
600
33%
1058
September1st to 15thNight
54%
716
20%
1837
11%
716
57%
716
34%
1173
September16th to endNight
52%
657
20%
1815
14%
657
55%
657
32%
1128
October1st to 15thNight
39%
660
18%
1980
14%
660
45%
660
22%
1347
October16th to endNight
22%
704
12%
2112
6%
704
30%
704
14%
1571
November1st to 15thNight
31%
700
17%
2369
14%
700
37%
700
17%
1625
November16th to endNight
21%
720
10%
2520
6%
720
27%
720
11%
1909
December1st to 15thNight
12%
720
5%
2520
2%
720
17%
720
6%
2079
December16th to endNight
9%
768
5%
2688
1%
768
15%
768
5%
2305

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%47%6%35%45%7%29%
48158
Night
14%9%47%6%3445%6%32%
46730
Cloud CoverDay
15%9%47%6%35%45%7%29%
48168
Night
15%9%47%5%3445%6%32%
46734
TransparencyDay
52%6%12%18%9%
47852
Night
50%6%11%19%10%1
46554
SeeingDay
19%9%27%24%14%5%
5611
Night
19%10%30%26%11%1
14842

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
17%16%7%11%8%36%435%14%
1501
16th to endDay
12%17%8%14%9%45%5%45%13%
1728
February1st to 15thDay
15%15%7%13%9%6%5%445%13%
1575
16th to endDay
16%15%6%8%8%35%5%5%6%17%
1479
March1st to 15thDay
15%12%6%8%9%35%345%25%
1954
16th to endDay
15%9%5%7%7%35%45%6%30%
2112
April1st to 15thDay
20%10%46%5%3445%6%28%
2126
16th to endDay
18%9%25%5%23347%36%
2340
May1st to 15thDay
18%8%35%5%25%447%35%
2340
16th to endDay
13%6%35%5%35%45%7%38%
2618
June1st to 15thDay
14%6%35%5%25%5%6%8%35%
2541
16th to endDay
13%5%16%5%35%46%10%35%
2700
July1st to 15thDay
9%435%6%35%5%7%9%37%
2643
16th to endDay
10%6%36%6%36%5%7%9%35%
2494
August1st to 15thDay
9%6%35%7%45%6%6%9%34%
2340
16th to endDay
11%6%35%5%45%6%7%7%35%
2444
September1st to 15thDay
13%7%25%5%4445%8%37%
2096
16th to endDay
15%6%25%5%2445%8%37%
1815
October1st to 15thDay
19%9%47%6%34435%30%
1650
16th to endDay
26%11%47%6%24446%20%
1757
November1st to 15thDay
15%11%48%6%25%6%5%6%28%
1489
16th to endDay
18%13%7%10%6%3345%5%18%
1440
December1st to 15thDay
16%19%8%11%7%35%46%412%
1440
16th to endDay
20%18%9%13%7%3444211%
1536
January1st to 15thNight
20%14%6%9%8%45%445%16%
2435
16th to endNight
14%14%8%12%8%45%45%6%15%
2496
February1st to 15thNight
13%13%7%10%8%45%5%5%5%18%
2285
16th to endNight
14%11%6%10%9%3445%6%23%
1993
March1st to 15thNight
15%8%5%8%6%35%5%5%6%28%
1982
16th to endNight
14%8%36%42444440%
2112
April1st to 15thNight
18%9%36%5%3445%5%32%
1832
16th to endNight
12%6%26%6%35%446%40%
1620
May1st to 15thNight
14%7%25%6%345%5%7%37%
1611
16th to endNight
10%425%43446%8%46%
1495
June1st to 15thNight
12%5%245%3447%9%40%
1415
16th to endNight
11%5%15%42435%9%45%
1260
July1st to 15thNight
5%32432445%8%55%
1314
16th to endNight
7%425%5%2446%9%46%
1673
August1st to 15thNight
6%4145%35%6%6%8%48%
1620
16th to endNight
8%6%245%24446%50%
1746
September1st to 15thNight
12%42432445%7%47%
1837
16th to endNight
12%6%25%43345%7%46%
1815
October1st to 15thNight
17%6%37%42436%6%37%
1980
16th to endNight
21%9%38%6%35%46%7%25%
2112
November1st to 15thNight
14%8%36%5%35%5%5%8%32%
2369
16th to endNight
19%12%5%7%7%34447%23%
2520
December1st to 15thNight
19%16%6%9%7%35%5%5%5%15%
2520
16th to endNight
20%14%8%13%7%34445%12%
2688

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
17%17%7%10%9%345%35%15%
1501
16th to endDay
12%17%8%13%9%45%445%14%
1728
February1st to 15thDay
16%15%7%14%8%5%5%5%3414%
1575
16th to endDay
17%14%6%10%7%36%45%6%17%
1479
March1st to 15thDay
16%11%6%9%7%45%345%25%
1965
16th to endDay
15%9%47%7%35%45%5%31%
2111
April1st to 15thDay
20%10%36%5%34447%28%
2126
16th to endDay
18%9%35%423447%36%
2340
May1st to 15thDay
18%8%25%43445%6%35%
2340
16th to endDay
13%5%26%5%445%5%7%38%
2618
June1st to 15thDay
14%6%25%6%25%5%6%9%35%
2541
16th to endDay
14%5%16%5%35%5%6%10%35%
2700
July1st to 15thDay
9%435%7%36%6%6%9%38%
2643
16th to endDay
10%7%25%7%35%5%7%9%35%
2494
August1st to 15thDay
10%6%26%7%45%6%6%8%34%
2340
16th to endDay
11%7%26%6%35%6%6%7%35%
2444
September1st to 15thDay
14%6%36%6%3445%9%36%
2096
16th to endDay
16%6%26%5%2445%8%37%
1815
October1st to 15thDay
19%9%48%5%34445%31%
1650
16th to endDay
26%12%47%6%3335%5%20%
1757
November1st to 15thDay
15%11%5%6%5%35%5%5%6%28%
1489
16th to endDay
19%14%7%9%6%3345%5%18%
1440
December1st to 15thDay
16%19%8%10%7%4445%412%
1440
16th to endDay
20%18%9%12%7%335%4211%
1536
January1st to 15thNight
21%14%6%9%7%3445%417%
2435
16th to endNight
14%14%8%13%8%35%5%45%16%
2496
February1st to 15thNight
13%14%6%11%9%46%5%5%6%19%
2278
16th to endNight
14%11%6%9%8%3445%7%23%
1993
March1st to 15thNight
16%9%5%7%6%35%5%5%6%28%
1994
16th to endNight
14%8%36%42444440%
2112
April1st to 15thNight
18%9%36%5%2445%5%33%
1832
16th to endNight
13%6%26%5%35%447%40%
1620
May1st to 15thNight
15%7%25%5%35%5%5%6%38%
1610
16th to endNight
10%426%33436%7%46%
1495
June1st to 15thNight
11%5%15%435%5%6%8%41%
1415
16th to endNight
11%5%245%2435%8%46%
1260
July1st to 15thNight
4323324449%55%
1314
16th to endNight
7%425%43446%9%47%
1673
August1st to 15thNight
6%224435%5%6%9%49%
1620
16th to endNight
8%5%245%24346%50%
1746
September1st to 15thNight
12%42433445%7%47%
1837
16th to endNight
13%5%2442435%8%45%
1815
October1st to 15thNight
17%6%26%5%3345%6%38%
1980
16th to endNight
21%8%37%6%345%5%7%26%
2112
November1st to 15thNight
15%8%36%6%35%5%6%7%32%
2369
16th to endNight
20%11%48%6%34447%23%
2520
December1st to 15thNight
20%16%6%9%6%35%5%5%5%16%
2520
16th to endNight
20%15%9%13%6%35%44413%
2688

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
71%5%8%9%4
1502
16th to endDay
72%48%8%5%
1728
February1st to 15thDay
71%5%7%10%3
1577
16th to endDay
65%5%10%11%6%
1479
March1st to 15thDay
60%5%10%14%8%
1965
16th to endDay
53%5%11%16%11%1
2112
April1st to 15thDay
54%6%9%19%10%
2126
16th to endDay
47%411%20%14%1
2340
May1st to 15thDay
47%5%11%22%10%
2340
16th to endDay
43%6%14%20%13%1
2622
June1st to 15thDay
43%7%13%22%12%
2541
16th to endDay
43%6%14%23%11%
2700
July1st to 15thDay
38%6%13%24%15%1
2488
16th to endDay
42%7%15%22%9%1
2338
August1st to 15thDay
44%7%16%18%11%1
2327
16th to endDay
42%8%15%22%10%
2444
September1st to 15thDay
43%6%15%23%10%
2096
16th to endDay
43%6%15%25%9%
1815
October1st to 15thDay
54%5%10%16%10%1
1650
16th to endDay
63%6%13%12%4
1757
November1st to 15thDay
52%8%13%16%8%
1489
16th to endDay
65%5%10%12%4
1440
December1st to 15thDay
72%7%9%8%1
1440
16th to endDay
76%6%6%8%2
1536
January1st to 15thNight
68%6%9%11%4
2435
16th to endNight
67%5%10%11%4
2496
February1st to 15thNight
64%6%9%15%4
2287
16th to endNight
60%5%12%14%7%
1993
March1st to 15thNight
55%5%11%19%7%
1994
16th to endNight
46%49%21%16%2
2112
April1st to 15thNight
52%48%20%13%
1832
16th to endNight
44%48%21%18%2
1620
May1st to 15thNight
44%5%10%23%13%2
1611
16th to endNight
35%5%14%26%13%3
1497
June1st to 15thNight
37%6%13%25%16%
1415
16th to endNight
36%5%12%28%15%1
1260
July1st to 15thNight
25%6%12%30%23%2
1240
16th to endNight
33%6%15%25%15%2
1566
August1st to 15thNight
29%7%18%29%13%1
1609
16th to endNight
33%6%10%30%17%1
1746
September1st to 15thNight
34%7%14%28%14%1
1837
16th to endNight
36%414%29%13%
1815
October1st to 15thNight
45%6%10%23%13%
1980
16th to endNight
54%7%13%17%6%
2112
November1st to 15thNight
47%7%13%19%10%1
2369
16th to endNight
59%5%14%13%5%
2520
December1st to 15thNight
69%6%12%8%3
2520
16th to endNight
73%6%8%8%2
2688

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
16%23%42%11%5%
71
16th to endDay
32%13%38%15%
96
February1st to 15thDay
25%22%42%8%1
90
16th to endDay
24%22%37%14%1
81
March1st to 15thDay
23%14%32%23%5%
255
16th to endDay
23%6%34%23%9%2
288
April1st to 15thDay
22%13%30%23%9%
270
16th to endDay
23%11%29%20%10%4
270
May1st to 15thDay
23%8%25%24%12%5%
288
16th to endDay
16%7%32%22%15%5%
331
June1st to 15thDay
16%10%22%30%16%2
336
16th to endDay
14%8%30%28%14%2
495
July1st to 15thDay
12%426%30%19%7%
422
16th to endDay
10%323%30%22%9%
326
August1st to 15thDay
14%220%26%22%14%
313
16th to endDay
16%415%25%21%17%
332
September1st to 15thDay
13%5%16%23%28%12%
310
16th to endDay
20%420%24%19%12%
254
October1st to 15thDay
18%9%28%23%16%4
255
16th to endDay
30%13%28%22%4
269
November1st to 15thDay
12%16%37%24%6%4
75
16th to endDay
31%20%28%10%8%1
60
December1st to 15thDay
28%26%28%13%3
60
16th to endDay
32%25%37%4
64
January1st to 15thNight
27%18%35%14%3
720
16th to endNight
21%14%36%21%4
768
February1st to 15thNight
22%17%35%21%3
704
16th to endNight
20%14%36%22%5%
631
March1st to 15thNight
21%16%36%20%4
720
16th to endNight
19%11%33%24%10%
768
April1st to 15thNight
22%14%33%24%5%
706
16th to endNight
15%9%32%31%9%1
540
May1st to 15thNight
17%6%28%32%14%1
531
16th to endNight
12%333%33%16%
375
June1st to 15thNight
13%5%27%40%12%
360
16th to endNight
13%230%38%15%
360
July1st to 15thNight
5%222%47%20%1
340
16th to endNight
10%122%42%21%1
535
August1st to 15thNight
8%119%39%26%3
539
16th to endNight
12%319%32%28%3
600
September1st to 15thNight
14%6%20%31%21%5%
716
16th to endNight
15%5%20%29%23%4
657
October1st to 15thNight
21%7%26%29%13%2
660
16th to endNight
25%13%32%23%4
704
November1st to 15thNight
19%11%32%24%10%1
700
16th to endNight
25%15%30%21%6%
720
December1st to 15thNight
29%17%33%17%2
720
16th to endNight
28%17%34%15%3
768
Page generated at 2017-09-15 10:29:56. Version ac04

Copyright 2017 A. Danko


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