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Feef Peak Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Feef Peak Observatory clear sky chart from 2005-11-05 to 2017-10-16.

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
59%
15801
31%
47252
21%
15760
69%
15760
45%
24349

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
60%
742
33%
2352
27%
741
70%
741
52%
1083
January16th to endNight
54%
768
36%
2496
25%
768
69%
768
50%
1145
February1st to 15thNight
52%
702
29%
2215
21%
700
62%
700
45%
1081
February16th to endNight
42%
632
38%
1894
19%
632
61%
632
48%
921
March1st to 15thNight
51%
720
34%
2036
20%
720
62%
720
46%
1079
March16th to endNight
51%
720
35%
2064
19%
720
64%
720
51%
1013
April1st to 15thNight
43%
539
33%
1798
17%
539
63%
539
42%
858
April16th to endNight
42%
540
35%
1800
20%
540
65%
540
44%
835
May1st to 15thNight
48%
539
25%
1799
18%
539
61%
539
41%
894
May16th to endNight
55%
563
31%
1553
16%
561
70%
561
48%
820
June1st to 15thNight
62%
540
25%
1440
16%
540
69%
540
48%
777
June16th to endNight
71%
540
25%
1440
20%
540
74%
540
50%
774
July1st to 15thNight
73%
510
17%
1437
15%
510
74%
510
32%
896
July16th to endNight
76%
564
16%
1593
16%
531
77%
531
31%
976
August1st to 15thNight
78%
539
15%
1712
16%
536
78%
536
31%
1031
August16th to endNight
77%
573
23%
1910
26%
573
80%
573
32%
1107
September1st to 15thNight
73%
540
23%
1800
24%
540
76%
540
30%
1068
September16th to endNight
68%
564
35%
1932
31%
564
76%
564
43%
948
October1st to 15thNight
64%
720
34%
2160
24%
720
71%
720
51%
1062
October16th to endNight
66%
708
39%
2124
26%
708
74%
708
56%
1000
November1st to 15thNight
65%
778
39%
2178
25%
778
74%
778
62%
1006
November16th to endNight
62%
900
38%
2340
24%
900
68%
900
56%
1219
December1st to 15thNight
54%
900
32%
2491
19%
900
65%
900
49%
1285
December16th to endNight
49%
960
31%
2688
19%
960
59%
960
44%
1471

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
221332445%8%61%
48159
Night
331332345%7%61%
47446
TransparencyDay
21%5%10%22%26%14%
47852
Night
21%5%10%22%26%13%
47254
SeeingDay
5%10%25%31%22%5%
5642
Night
46%25%40%21%1
15807

By Month

Percentage Cloud Cover SW (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
1312213337%68%
1596
16th to endDay
3323222336%67%
1728
February1st to 15thDay
23432335%6%64%
1645
16th to endDay
131332335%9%63%
1580
March1st to 15thDay
231322345%8%62%
1923
16th to endDay
2213223447%65%
2159
April1st to 15thDay
221332345%8%62%
2150
16th to endDay
2313223345%67%
2160
May1st to 15thDay
221232345%8%63%
2151
16th to endDay
2212213447%67%
2554
June1st to 15thDay
11221346%8%66%
2520
16th to endDay
11131345%8%67%
2520
July1st to 15thDay
34236%36%6%8%11%44%
2432
16th to endDay
33245%45%8%8%10%41%
2467
August1st to 15thDay
2313435%6%8%10%48%
2238
16th to endDay
3413435%6%7%10%48%
2292
September1st to 15thDay
6%413435%5%7%9%48%
2160
16th to endDay
222324446%65%
2025
October1st to 15thDay
4212212345%68%
1800
16th to endDay
221221213474%
1768
November1st to 15thDay
121112347%72%
1668
16th to endDay
2212322336%69%
1620
December1st to 15thDay
24231335%6%65%
1467
16th to endDay
342343345%8%56%
1536
January1st to 15thNight
2312213236%70%
2352
16th to endNight
3411213347%66%
2496
February1st to 15thNight
2424323335%64%
2205
16th to endNight
2312424346%64%
1894
March1st to 15thNight
3412324446%61%
2036
16th to endNight
4312212335%68%
2064
April1st to 15thNight
322332446%6%61%
1798
16th to endNight
321331334468%
1800
May1st to 15thNight
321342335%8%60%
1799
16th to endNight
2312313447%65%
1553
June1st to 15thNight
1112325%6%6%9%59%
1440
16th to endNight
1124245%7%8%60%
1440
July1st to 15thNight
43145%26%8%10%11%42%
1524
16th to endNight
32146%36%5%8%15%41%
1701
August1st to 15thNight
33145%36%8%9%11%42%
1721
16th to endNight
32145%46%6%9%12%44%
1910
September1st to 15thNight
42145%45%7%9%12%42%
1800
16th to endNight
3313323345%65%
1932
October1st to 15thNight
421331325%6%67%
2160
16th to endNight
321312335%71%
2124
November1st to 15thNight
1111212245%74%
2178
16th to endNight
3212322335%69%
2340
December1st to 15thNight
3412212347%64%
2491
16th to endNight
3414423349%57%
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
16%5%11%30%32%4
1597
16th to endDay
19%48%26%31%9%
1728
February1st to 15thDay
20%5%11%27%25%11%
1646
16th to endDay
18%36%26%32%11%
1580
March1st to 15thDay
20%46%23%32%12%
1923
16th to endDay
19%38%20%34%14%
2159
April1st to 15thDay
20%37%22%30%15%
2150
16th to endDay
18%36%18%34%18%
2160
May1st to 15thDay
19%5%10%17%28%17%
2151
16th to endDay
18%48%18%25%24%
2557
June1st to 15thDay
16%39%17%21%31%
2520
16th to endDay
15%49%18%22%30%
2520
July1st to 15thDay
30%9%15%15%15%12%
2290
16th to endDay
31%10%19%26%10%1
2312
August1st to 15thDay
27%10%17%21%15%6%
2223
16th to endDay
28%9%13%24%17%6%
2292
September1st to 15thDay
30%7%14%22%16%8%
2160
16th to endDay
19%5%6%20%29%18%
2025
October1st to 15thDay
18%5%5%18%30%20%
1800
16th to endDay
15%35%21%35%19%
1768
November1st to 15thDay
12%28%24%37%14%
1668
16th to endDay
16%36%23%37%12%
1620
December1st to 15thDay
18%313%35%24%4
1467
16th to endDay
25%417%27%21%3
1536
January1st to 15thNight
17%310%31%29%6%
2352
16th to endNight
17%310%25%34%8%
2496
February1st to 15thNight
20%411%27%23%11%
2215
16th to endNight
19%37%21%34%13%
1894
March1st to 15thNight
22%46%25%30%11%
2036
16th to endNight
18%36%19%36%16%
2064
April1st to 15thNight
21%37%21%28%17%
1798
16th to endNight
20%36%18%32%19%
1800
May1st to 15thNight
22%5%10%16%27%17%
1800
16th to endNight
19%5%10%17%23%23%
1554
June1st to 15thNight
20%6%11%14%17%30%
1440
16th to endNight
18%7%11%15%17%29%
1440
July1st to 15thNight
30%11%16%17%12%11%
1437
16th to endNight
30%11%24%22%9%1
1593
August1st to 15thNight
29%12%19%18%13%6%
1712
16th to endNight
28%10%16%24%12%6%
1910
September1st to 15thNight
29%12%17%18%13%8%
1800
16th to endNight
21%5%8%16%27%20%
1932
October1st to 15thNight
18%47%17%28%22%
2160
16th to endNight
15%45%17%36%20%
2124
November1st to 15thNight
12%26%23%39%14%
2178
16th to endNight
18%35%21%34%17%
2340
December1st to 15thNight
19%411%32%27%4
2491
16th to endNight
24%413%30%22%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
8%6%34%32%16%1
90
16th to endDay
410%38%25%19%2
96
February1st to 15thDay
6%15%20%34%23%
90
16th to endDay
7%13%35%27%16%
81
March1st to 15thDay
5%21%30%29%13%
213
16th to endDay
6%29%31%21%9%1
288
April1st to 15thDay
8%24%33%21%8%2
269
16th to endDay
10%27%38%17%5%
270
May1st to 15thDay
319%42%23%10%
288
16th to endDay
5%10%31%36%14%1
474
June1st to 15thDay
27%22%35%28%3
495
16th to endDay
2217%34%37%6%
495
July1st to 15thDay
415%37%32%9%
394
16th to endDay
5%19%26%36%21%
327
August1st to 15thDay
3112%36%33%13%
315
16th to endDay
8%15%34%29%11%
332
September1st to 15thDay
5%323%40%20%6%
315
16th to endDay
47%28%38%19%1
210
October1st to 15thDay
5%10%28%29%20%4
135
16th to endDay
9%8%21%23%28%10%
99
November1st to 15thDay
211%25%32%25%3
90
16th to endDay
11%13%36%24%14%
90
December1st to 15thDay
6%15%30%36%10%1
90
16th to endDay
13%11%30%36%7%1
96
January1st to 15thNight
4426%43%19%1
745
16th to endNight
5%5%31%39%15%1
768
February1st to 15thNight
47%31%42%12%
704
16th to endNight
49%41%38%5%
632
March1st to 15thNight
5%8%31%41%12%
720
16th to endNight
311%31%41%12%
720
April1st to 15thNight
314%36%38%6%
539
16th to endNight
412%38%35%9%
540
May1st to 15thNight
49%32%40%12%
540
16th to endNight
36%32%39%17%
563
June1st to 15thNight
1327%46%19%
540
16th to endNight
319%48%27%1
540
July1st to 15thNight
5%10%41%38%3
510
16th to endNight
46%30%51%6%
564
August1st to 15thNight
38%31%47%8%
539
16th to endNight
318%38%42%6%
573
September1st to 15thNight
4212%42%35%2
540
16th to endNight
4319%43%26%2
564
October1st to 15thNight
4324%44%21%2
720
16th to endNight
4322%41%25%3
708
November1st to 15thNight
25%25%41%24%1
778
16th to endNight
37%23%40%21%3
900
December1st to 15thNight
6%9%26%43%13%
900
16th to endNight
5%8%32%42%11%
960
Page generated at 2017-10-17 14:35:23. Version ac04

Copyright 2017 A. Danko


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