Five Ferns Observation Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Five Ferns Observation Site clear sky chart from 2005-11-05 to 2017-10-31.

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
30%
14853
13%
47373
8%
14821
36%
14821
16%
34135

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
16%
720
5%
2506
2%
716
20%
716
7%
2053
January16th to endNight
22%
768
9%
2652
6%
768
27%
768
10%
2033
February1st to 15thNight
17%
704
9%
2287
4%
701
22%
701
9%
1820
February16th to endNight
22%
631
12%
1928
6%
631
31%
631
12%
1474
March1st to 15thNight
21%
720
13%
2120
7%
720
28%
720
15%
1597
March16th to endNight
31%
768
18%
2019
9%
768
37%
768
21%
1431
April1st to 15thNight
26%
718
16%
1796
6%
718
31%
718
21%
1335
April16th to endNight
29%
663
17%
1743
6%
663
35%
663
23%
1226
May1st to 15thNight
32%
360
16%
1440
14%
360
41%
360
16%
948
May16th to endNight
33%
375
12%
1497
10%
374
44%
374
18%
954
June1st to 15thNight
36%
360
9%
1440
9%
360
44%
360
13%
1007
June16th to endNight
41%
360
9%
1440
13%
360
46%
360
19%
908
July1st to 15thNight
51%
340
14%
1360
21%
340
57%
340
27%
762
July16th to endNight
53%
376
13%
1418
16%
354
58%
354
24%
820
August1st to 15thNight
50%
425
14%
1496
13%
423
54%
423
22%
957
August16th to endNight
50%
732
20%
1878
11%
732
54%
732
36%
1196
September1st to 15thNight
48%
720
15%
1800
8%
720
50%
720
29%
1246
September16th to endNight
50%
717
23%
1950
17%
717
54%
717
32%
1246
October1st to 15thNight
35%
720
17%
2160
13%
720
43%
720
21%
1489
October16th to endNight
24%
768
11%
2413
6%
768
32%
768
13%
1819
November1st to 15thNight
27%
700
16%
2302
12%
700
35%
700
16%
1645
November16th to endNight
20%
720
11%
2520
7%
720
26%
720
10%
1939
December1st to 15thNight
17%
720
6%
2520
3%
720
21%
720
8%
2030
December16th to endNight
14%
768
7%
2688
3%
768
19%
768
7%
2200

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
18%8%36%5%34446%32%
48387
Night
18%10%46%5%34446%31%
47542
Cloud CoverDay
18%9%36%5%34446%32%
48396
Night
19%10%46%5%34446%31%
47548
TransparencyDay
51%6%11%19%9%1
48074
Night
53%5%12%18%9%
47373
SeeingDay
22%11%28%22%11%4
5690
Night
23%10%28%26%9%
14853

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
23%15%6%9%6%4434318%
1432
16th to endDay
14%15%5%9%7%34445%22%
1569
February1st to 15thDay
16%15%5%10%7%45%445%20%
1575
16th to endDay
19%14%5%9%6%3434424%
1545
March1st to 15thDay
18%12%5%8%7%3443326%
1829
16th to endDay
18%9%35%423335%39%
2205
April1st to 15thDay
23%11%46%5%13235%32%
2152
16th to endDay
21%8%35%5%22446%36%
2226
May1st to 15thDay
20%7%36%434447%34%
2511
16th to endDay
18%6%25%5%345%5%7%35%
2618
June1st to 15thDay
23%6%25%5%345%46%31%
2520
16th to endDay
19%6%245%36%5%5%7%32%
2520
July1st to 15thDay
13%426%5%35%46%8%39%
2520
16th to endDay
12%5%25%5%36%6%7%8%35%
2654
August1st to 15thDay
12%6%36%6%35%6%6%7%35%
2451
16th to endDay
11%5%15%435%5%5%7%43%
2312
September1st to 15thDay
17%5%1442445%7%40%
2160
16th to endDay
15%5%24423446%46%
2009
October1st to 15thDay
20%7%35%5%2445%5%34%
1800
16th to endDay
26%9%37%6%34246%24%
1809
November1st to 15thDay
15%8%36%6%35%5%47%31%
1554
16th to endDay
23%12%48%5%33335%25%
1440
December1st to 15thDay
24%16%49%6%35%435%16%
1440
16th to endDay
26%14%5%8%6%2443419%
1536
January1st to 15thNight
19%17%6%10%7%3443417%
2506
16th to endNight
14%16%7%8%6%34345%24%
2652
February1st to 15thNight
15%14%6%12%7%3434420%
2285
16th to endNight
17%13%5%9%6%24445%26%
1928
March1st to 15thNight
22%11%47%5%2323430%
2107
16th to endNight
18%9%35%5%2334439%
2019
April1st to 15thNight
23%8%35%424245%33%
1796
16th to endNight
19%7%25%5%23346%38%
1743
May1st to 15thNight
20%8%25%5%2345%6%35%
1440
16th to endNight
18%5%24435%5%5%7%37%
1495
June1st to 15thNight
21%6%37%5%35%5%5%7%29%
1440
16th to endNight
18%6%2442446%9%36%
1440
July1st to 15thNight
11%423325%5%6%11%43%
1440
16th to endNight
9%5%24335%6%7%9%42%
1514
August1st to 15thNight
12%5%25%4246%5%9%38%
1506
16th to endNight
11%42333445%6%49%
1878
September1st to 15thNight
16%5%245%24346%42%
1800
16th to endNight
14%5%23423445%48%
1950
October1st to 15thNight
18%7%35%334346%37%
2160
16th to endNight
26%9%37%5%34346%26%
2413
November1st to 15thNight
21%9%35%6%34345%33%
2302
16th to endNight
22%12%48%5%35%335%25%
2520
December1st to 15thNight
23%15%5%8%5%34435%19%
2520
16th to endNight
25%16%5%7%6%3343418%
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
23%15%5%8%6%45%33318%
1432
16th to endDay
14%16%6%9%7%44445%22%
1569
February1st to 15thDay
15%15%6%9%7%45%5%4419%
1575
16th to endDay
19%15%5%8%7%3333325%
1545
March1st to 15thDay
19%13%5%8%7%45%42326%
1839
16th to endDay
18%9%25%433335%39%
2204
April1st to 15thDay
24%10%36%432335%32%
2152
16th to endDay
20%9%35%42335%436%
2226
May1st to 15thDay
19%7%35%5%24447%34%
2511
16th to endDay
17%6%25%5%345%5%7%35%
2618
June1st to 15thDay
23%7%25%5%3445%6%30%
2520
16th to endDay
19%6%25%5%36%5%5%7%32%
2520
July1st to 15thDay
13%5%25%5%35%5%6%8%39%
2520
16th to endDay
12%5%25%5%46%6%7%8%35%
2654
August1st to 15thDay
12%7%26%6%35%6%6%7%34%
2451
16th to endDay
11%425%5%26%45%7%43%
2312
September1st to 15thDay
18%5%1443345%8%40%
2160
16th to endDay
15%6%13423447%46%
2009
October1st to 15thDay
20%6%36%5%245%47%33%
1800
16th to endDay
27%9%37%6%35%236%24%
1809
November1st to 15thDay
16%8%46%6%45%5%46%32%
1554
16th to endDay
23%12%49%5%3334425%
1440
December1st to 15thDay
25%17%49%5%3443416%
1440
16th to endDay
26%14%5%9%6%2342419%
1536
January1st to 15thNight
19%18%6%10%6%3443417%
2506
16th to endNight
14%16%6%8%6%35%35%5%23%
2652
February1st to 15thNight
15%15%6%12%7%35%35%420%
2278
16th to endNight
17%13%5%9%6%34345%26%
1928
March1st to 15thNight
22%11%5%7%5%3323430%
2120
16th to endNight
17%10%35%5%2324439%
2019
April1st to 15thNight
24%8%35%5%24235%34%
1796
16th to endNight
20%7%26%424346%38%
1743
May1st to 15thNight
19%8%345%25%35%6%35%
1440
16th to endNight
17%6%25%4335%5%7%37%
1495
June1st to 15thNight
22%6%26%5%45%45%7%28%
1440
16th to endNight
18%6%2443346%9%36%
1440
July1st to 15thNight
12%314325%5%5%11%43%
1440
16th to endNight
9%424335%6%8%8%42%
1514
August1st to 15thNight
12%6%36%4245%7%8%37%
1506
16th to endNight
12%42442445%6%48%
1878
September1st to 15thNight
17%5%245%24446%42%
1800
16th to endNight
15%423423446%48%
1950
October1st to 15thNight
18%8%35%434346%36%
2160
16th to endNight
26%9%36%5%24346%26%
2413
November1st to 15thNight
20%9%35%5%24445%33%
2302
16th to endNight
22%12%5%8%5%34335%24%
2520
December1st to 15thNight
23%16%5%8%5%34345%19%
2520
16th to endNight
25%16%5%7%6%3343418%
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
70%49%9%5%
1433
16th to endDay
63%5%12%12%6%
1569
February1st to 15thDay
65%5%10%16%2
1577
16th to endDay
62%410%12%8%1
1545
March1st to 15thDay
62%412%12%7%
1839
16th to endDay
47%39%18%15%5%
2205
April1st to 15thDay
55%37%18%12%2
2152
16th to endDay
49%5%8%19%14%3
2226
May1st to 15thDay
49%5%9%20%13%1
2511
16th to endDay
46%8%12%19%12%1
2622
June1st to 15thDay
52%6%11%19%9%
2520
16th to endDay
48%8%12%19%10%
2520
July1st to 15thDay
39%7%13%27%11%
2371
16th to endDay
43%8%17%22%9%
2487
August1st to 15thDay
44%9%16%21%8%
2437
16th to endDay
37%7%16%27%11%
2312
September1st to 15thDay
41%6%12%27%12%
2160
16th to endDay
37%6%11%33%10%
2009
October1st to 15thDay
49%6%12%21%9%
1800
16th to endDay
62%5%12%13%6%
1809
November1st to 15thDay
50%6%14%18%8%
1554
16th to endDay
61%5%11%14%6%
1440
December1st to 15thDay
70%7%10%10%1
1440
16th to endDay
69%6%9%10%4
1536
January1st to 15thNight
69%411%9%4
2506
16th to endNight
61%5%11%14%6%
2652
February1st to 15thNight
65%5%11%14%3
2287
16th to endNight
59%5%9%16%8%
1928
March1st to 15thNight
58%410%18%7%
2120
16th to endNight
48%410%18%14%4
2019
April1st to 15thNight
53%37%19%14%
1796
16th to endNight
47%49%18%16%3
1743
May1st to 15thNight
49%5%8%18%14%3
1440
16th to endNight
44%7%14%19%12%2
1497
June1st to 15thNight
53%6%12%16%9%1
1440
16th to endNight
42%7%14%19%14%
1440
July1st to 15thNight
31%8%15%29%14%
1360
16th to endNight
35%8%16%23%15%
1418
August1st to 15thNight
40%9%17%20%12%
1496
16th to endNight
33%6%15%30%13%
1878
September1st to 15thNight
42%5%11%26%12%
1800
16th to endNight
36%5%11%32%12%
1950
October1st to 15thNight
47%5%11%24%10%
2160
16th to endNight
59%413%17%4
2413
November1st to 15thNight
53%5%13%16%9%1
2302
16th to endNight
62%5%11%15%5%
2520
December1st to 15thNight
67%5%12%11%2
2520
16th to endNight
69%5%10%10%3
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
28%20%20%21%10%
60
16th to endDay
33%13%28%18%5%
69
February1st to 15thDay
32%24%31%11%1
90
16th to endDay
29%16%31%19%2
204
March1st to 15thDay
25%13%35%17%8%
270
16th to endDay
24%12%31%20%7%3
288
April1st to 15thDay
28%15%29%18%6%1
270
16th to endDay
24%18%25%18%10%3
270
May1st to 15thDay
28%11%29%18%9%4
288
16th to endDay
19%16%34%15%13%1
331
June1st to 15thDay
26%9%30%24%7%2
315
16th to endDay
20%9%30%25%11%2
315
July1st to 15thDay
16%6%25%30%15%5%
305
16th to endDay
15%5%24%33%16%3
326
August1st to 15thDay
15%5%27%33%14%4
313
16th to endDay
12%5%26%30%14%12%
332
September1st to 15thDay
18%5%22%24%14%14%
315
16th to endDay
15%8%26%18%21%9%
314
October1st to 15thDay
22%10%28%19%14%4
315
16th to endDay
31%15%24%21%6%
308
November1st to 15thDay
16%15%30%23%11%1
208
16th to endDay
33%13%25%23%5%
60
December1st to 15thDay
23%21%35%15%5%
60
16th to endDay
43%26%21%6%1
64
January1st to 15thNight
28%15%31%19%4
720
16th to endNight
24%13%31%25%5%
768
February1st to 15thNight
22%16%35%22%3
704
16th to endNight
24%13%33%23%4
631
March1st to 15thNight
27%13%32%22%3
720
16th to endNight
22%12%27%27%9%
768
April1st to 15thNight
27%11%29%26%4
718
16th to endNight
24%12%30%23%9%
663
May1st to 15thNight
25%6%29%28%8%1
360
16th to endNight
19%5%36%25%12%
375
June1st to 15thNight
23%7%25%34%9%
360
16th to endNight
18%331%33%12%1
360
July1st to 15thNight
12%228%39%15%
340
16th to endNight
11%226%44%13%1
376
August1st to 15thNight
16%223%37%17%2
425
16th to endNight
13%324%35%20%1
732
September1st to 15thNight
20%5%21%33%17%1
720
16th to endNight
17%7%22%26%23%2
717
October1st to 15thNight
22%8%28%25%14%
720
16th to endNight
31%11%26%23%6%
768
November1st to 15thNight
26%10%29%22%10%
700
16th to endNight
28%15%26%19%9%
720
December1st to 15thNight
31%15%28%20%3
720
16th to endNight
34%12%32%17%3
768
Page generated at 2017-11-01 17:23:30. Version ac04

Copyright 2017 A. Danko


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