Fox Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fox Observatory clear sky chart from 2005-11-05 to 2017-08-12.

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
65%
16110
19%
46544
16%
16070
68%
16070
30%
29383

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
58%
716
18%
2327
16%
716
63%
716
27%
1427
January16th to endNight
54%
768
25%
2472
21%
768
62%
768
32%
1407
February1st to 15thNight
53%
703
27%
2095
22%
699
60%
699
35%
1229
February16th to endNight
59%
631
31%
1735
21%
631
67%
631
42%
981
March1st to 15thNight
60%
720
27%
1980
18%
720
67%
720
42%
1114
March16th to endNight
61%
768
27%
2112
22%
768
65%
768
41%
1208
April1st to 15thNight
71%
718
25%
1976
22%
718
73%
718
49%
1050
April16th to endNight
66%
720
25%
1803
16%
720
69%
720
43%
1075
May1st to 15thNight
74%
719
25%
1799
17%
719
76%
719
49%
1021
May16th to endNight
73%
608
16%
1730
14%
608
73%
608
29%
1133
June1st to 15thNight
65%
540
8%
1620
7%
540
65%
540
17%
1203
June16th to endNight
76%
540
8%
1620
7%
540
76%
540
24%
1112
July1st to 15thNight
71%
510
6%
1530
6%
510
71%
510
20%
1105
July16th to endNight
82%
564
9%
1595
9%
531
83%
531
30%
1038
August1st to 15thNight
76%
596
7%
1644
6%
593
76%
593
27%
1106
August16th to endNight
70%
700
5%
1847
5%
700
70%
700
21%
1353
September1st to 15thNight
68%
660
4%
1815
4%
660
68%
660
17%
1372
September16th to endNight
60%
657
5%
1815
5%
657
60%
657
15%
1420
October1st to 15thNight
68%
660
18%
1920
20%
660
70%
660
25%
1275
October16th to endNight
58%
704
19%
2112
19%
704
61%
704
26%
1389
November1st to 15thNight
66%
700
28%
2101
27%
700
71%
700
37%
1221
November16th to endNight
59%
720
26%
2160
24%
720
64%
720
30%
1357
December1st to 15thNight
62%
720
24%
2240
22%
720
67%
720
29%
1375
December16th to endNight
65%
768
24%
2496
24%
768
69%
768
33%
1412

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
9%6%37%8%47%7%7%9%27%
47408
Night
6%425%5%35%6%7%10%41%
46750
TransparencyDay
49%8%13%15%10%2
47109
Night
35%8%18%22%12%3
46553
SeeingDay
9%311%22%26%27%
5921
Night
7%212%31%32%13%
16118

By Month

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
9%6%47%6%37%6%7%8%32%
1611
16th to endDay
8%6%27%6%35%6%6%9%37%
1749
February1st to 15thDay
11%6%25%6%35%45%8%39%
1759
16th to endDay
8%415%5%36%5%6%9%42%
1738
March1st to 15thDay
6%425%6%47%6%6%9%39%
1980
16th to endDay
7%5%26%6%46%7%6%9%36%
2111
April1st to 15thDay
6%335%6%5%6%6%7%11%36%
1972
16th to endDay
8%426%7%47%6%7%10%35%
2157
May1st to 15thDay
5%325%5%47%6%7%9%41%
2152
16th to endDay
11%6%37%8%5%8%8%8%9%22%
2392
June1st to 15thDay
13%9%410%10%5%8%7%7%7%15%
2340
16th to endDay
10%7%49%10%5%9%9%8%10%15%
2340
July1st to 15thDay
10%7%49%10%5%8%7%9%8%16%
2340
16th to endDay
8%7%39%9%5%9%8%7%11%19%
2465
August1st to 15thDay
11%6%38%9%5%9%7%8%11%18%
2205
16th to endDay
10%6%39%10%5%9%9%8%10%15%
1998
September1st to 15thDay
9%7%412%11%6%9%8%7%8%13%
1815
16th to endDay
16%9%5%11%10%5%8%8%5%5%14%
1815
October1st to 15thDay
9%7%39%9%5%9%8%8%8%20%
1708
16th to endDay
16%7%27%7%37%6%5%8%28%
1760
November1st to 15thDay
8%5%26%8%46%6%5%8%37%
1757
16th to endDay
11%6%36%6%46%6%6%8%35%
1800
December1st to 15thDay
10%7%36%7%36%5%6%7%34%
1716
16th to endDay
9%5%25%6%45%6%8%9%36%
1728
January1st to 15thNight
8%5%35%5%35%5%7%11%39%
2327
16th to endNight
5%424435%5%6%9%46%
2472
February1st to 15thNight
8%4244245%5%8%48%
2093
16th to endNight
5%2134245%5%8%54%
1735
March1st to 15thNight
4214325%6%7%9%51%
1980
16th to endNight
5%31442446%10%50%
2112
April1st to 15thNight
421332446%10%57%
1976
16th to endNight
6%3243245%6%9%50%
1803
May1st to 15thNight
32134245%5%10%57%
1799
16th to endNight
8%4345%36%5%9%13%34%
1729
June1st to 15thNight
10%6%36%7%47%7%8%10%25%
1620
16th to endNight
5%325%6%37%7%10%14%32%
1620
July1st to 15thNight
5%5%37%8%46%6%8%11%33%
1620
16th to endNight
3425%5%35%6%8%13%39%
1703
August1st to 15thNight
5%3146%47%6%8%13%37%
1655
16th to endNight
7%426%6%37%8%9%11%31%
1847
September1st to 15thNight
6%437%7%6%7%8%10%14%23%
1815
16th to endNight
8%7%37%9%6%7%7%8%10%23%
1815
October1st to 15thNight
6%5%26%6%47%6%8%11%34%
1920
16th to endNight
12%7%25%5%25%5%6%8%37%
2112
November1st to 15thNight
6%3245%35%5%6%9%48%
2101
16th to endNight
8%5%25%5%35%45%8%43%
2160
December1st to 15thNight
8%425%426%5%6%10%42%
2240
16th to endNight
5%324426%5%6%10%47%
2496

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
46%6%13%16%13%5%
1612
16th to endDay
41%410%21%15%5%
1749
February1st to 15thDay
42%38%20%18%6%
1761
16th to endDay
36%410%24%17%6%
1738
March1st to 15thDay
38%411%23%17%3
1980
16th to endDay
41%5%10%21%15%6%
2112
April1st to 15thDay
38%5%14%23%15%2
1972
16th to endDay
41%6%10%19%17%3
2157
May1st to 15thDay
36%5%13%24%13%6%
2152
16th to endDay
54%7%13%17%6%
2396
June1st to 15thDay
64%9%12%9%3
2340
16th to endDay
57%13%18%9%1
2340
July1st to 15thDay
58%12%21%6%
2201
16th to endDay
55%11%24%8%
2310
August1st to 15thDay
54%11%21%11%
2192
16th to endDay
57%15%20%6%
1998
September1st to 15thDay
63%13%16%6%
1815
16th to endDay
69%10%11%5%2
1815
October1st to 15thDay
54%9%11%14%7%1
1708
16th to endDay
52%5%8%14%14%4
1760
November1st to 15thDay
42%49%18%18%5%
1757
16th to endDay
45%5%8%13%18%7%
1800
December1st to 15thDay
48%5%9%17%15%3
1716
16th to endDay
41%5%10%23%16%3
1728
January1st to 15thNight
38%5%16%23%13%2
2327
16th to endNight
31%6%13%27%16%4
2472
February1st to 15thNight
32%49%27%18%7%
2102
16th to endNight
26%5%14%27%19%5%
1735
March1st to 15thNight
26%5%13%28%20%5%
1980
16th to endNight
28%5%16%27%17%4
2112
April1st to 15thNight
21%5%19%32%18%3
1976
16th to endNight
28%5%14%27%20%4
1803
May1st to 15thNight
22%6%16%33%16%4
1800
16th to endNight
37%8%19%27%7%
1731
June1st to 15thNight
49%12%21%13%3
1620
16th to endNight
36%15%33%13%1
1620
July1st to 15thNight
43%14%30%11%
1530
16th to endNight
31%13%37%15%1
1595
August1st to 15thNight
34%14%33%16%1
1644
16th to endNight
39%18%30%10%1
1847
September1st to 15thNight
44%17%26%10%1
1815
16th to endNight
51%14%19%10%2
1815
October1st to 15thNight
39%9%17%20%11%1
1920
16th to endNight
43%5%12%21%13%4
2112
November1st to 15thNight
32%312%23%21%5%
2101
16th to endNight
38%410%19%17%8%
2160
December1st to 15thNight
36%6%14%23%16%2
2240
16th to endNight
32%5%13%26%19%3
2496

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
15%8%33%27%13%1
90
16th to endDay
17%10%27%33%7%4
96
February1st to 15thDay
10%6%25%39%14%6%
100
16th to endDay
8%225%34%25%2
239
March1st to 15thDay
5%427%34%24%4
270
16th to endDay
7%320%36%25%6%
288
April1st to 15thDay
4420%29%28%12%
270
16th to endDay
7%117%26%31%15%
270
May1st to 15thDay
3115%21%34%22%
288
16th to endDay
6%25%24%33%28%
331
June1st to 15thDay
14%36%15%26%33%
315
16th to endDay
5%1112%26%52%
315
July1st to 15thDay
6%19%25%56%
305
16th to endDay
7%317%23%56%
326
August1st to 15thDay
11%38%21%55%
297
16th to endDay
13%49%21%50%
268
September1st to 15thDay
6%3110%20%57%
255
16th to endDay
18%117%22%48%
254
October1st to 15thDay
9%25%25%36%19%
255
16th to endDay
14%219%24%25%14%
272
November1st to 15thDay
8%311%30%33%12%
265
16th to endDay
8%222%30%33%2
270
December1st to 15thDay
19%211%34%23%7%
186
16th to endDay
7%415%42%26%4
96
January1st to 15thNight
9%418%37%26%2
720
16th to endNight
6%425%42%19%1
768
February1st to 15thNight
9%324%41%19%1
704
16th to endNight
6%423%47%17%
631
March1st to 15thNight
6%323%42%22%1
720
16th to endNight
6%320%45%23%1
768
April1st to 15thNight
3216%47%26%2
718
16th to endNight
8%215%44%27%1
720
May1st to 15thNight
4111%45%35%2
720
16th to endNight
7%3434%40%10%
610
June1st to 15thNight
11%3317%41%23%
540
16th to endNight
4118%47%36%
540
July1st to 15thNight
6%18%43%39%
510
16th to endNight
315%42%48%
564
August1st to 15thNight
6%16%44%40%
596
16th to endNight
8%2211%40%35%
700
September1st to 15thNight
7%1211%39%37%
660
16th to endNight
10%114%42%29%
657
October1st to 15thNight
9%5%31%41%11%
660
16th to endNight
15%210%30%30%10%
704
November1st to 15thNight
6%216%37%31%6%
700
16th to endNight
8%316%39%27%3
720
December1st to 15thNight
9%314%39%30%3
720
16th to endNight
6%215%37%34%3
768
Page generated at 2017-08-13 14:16:13. Version ac04

Copyright 2017 A. Danko


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