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 2018-02-14.

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
65%
16857
19%
48771
16%
16817
69%
16817
30%
30669

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
56%
776
18%
2522
16%
776
63%
776
28%
1540
January16th to endNight
53%
832
24%
2678
20%
832
61%
832
31%
1549
February1st to 15thNight
56%
759
27%
2263
22%
755
62%
755
36%
1311
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
77%
611
7%
1681
6%
608
77%
608
28%
1127
August16th to endNight
70%
764
6%
2016
5%
764
70%
764
21%
1470
September1st to 15thNight
68%
720
4%
1980
4%
720
68%
720
18%
1481
September16th to endNight
62%
717
6%
1980
7%
717
62%
717
15%
1532
October1st to 15thNight
68%
720
17%
2095
19%
720
70%
720
25%
1398
October16th to endNight
58%
768
20%
2304
19%
768
61%
768
26%
1517
November1st to 15thNight
67%
760
27%
2281
26%
760
72%
760
38%
1309
November16th to endNight
60%
780
27%
2340
25%
780
65%
780
30%
1461
December1st to 15thNight
63%
780
25%
2427
23%
780
68%
780
31%
1450
December16th to endNight
68%
832
26%
2704
27%
832
71%
832
36%
1484

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%28%
49285
Night
6%425%5%35%6%7%10%42%
48977
TransparencyDay
49%8%13%15%10%2
48986
Night
34%8%18%22%12%3
48780
SeeingDay
9%312%22%26%26%
6599
Night
7%212%31%32%13%
16865

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%5%36%6%7%8%33%
1746
16th to endDay
8%5%27%6%36%6%6%9%36%
1895
February1st to 15thDay
11%6%25%5%35%45%9%39%
1892
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%9%11%18%
2253
16th to endDay
10%6%39%9%5%8%9%8%11%16%
2181
September1st to 15thDay
9%7%411%10%6%9%8%7%8%14%
1980
16th to endDay
15%9%5%11%10%5%7%8%5%5%15%
1980
October1st to 15thDay
9%7%39%9%5%9%8%8%8%19%
1863
16th to endDay
15%6%27%7%37%6%5%8%28%
1920
November1st to 15thDay
7%5%25%8%46%6%5%9%38%
1907
16th to endDay
10%6%35%5%46%6%6%8%36%
1950
December1st to 15thDay
10%7%36%6%36%5%6%7%36%
1859
16th to endDay
8%4246%35%5%7%10%38%
1872
January1st to 15thNight
8%5%35%5%35%5%6%11%39%
2522
16th to endNight
5%425%5%35%6%6%9%44%
2678
February1st to 15thNight
8%4244245%5%8%48%
2261
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%7%13%38%
1692
16th to endNight
7%426%6%37%8%9%11%31%
2016
September1st to 15thNight
6%437%6%6%7%8%9%13%24%
1980
16th to endNight
8%6%27%8%6%7%8%8%10%24%
1980
October1st to 15thNight
6%5%26%6%46%7%8%12%33%
2095
16th to endNight
11%7%26%5%35%45%8%37%
2304
November1st to 15thNight
6%3245%35%5%6%9%49%
2281
16th to endNight
8%5%25%5%36%5%5%8%44%
2340
December1st to 15thNight
7%425%426%5%5%10%45%
2427
16th to endNight
5%324425%5%6%11%48%
2704

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
45%5%13%16%14%5%
1747
16th to endDay
41%411%20%16%5%
1895
February1st to 15thDay
41%49%21%16%6%
1894
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
53%11%21%11%
2240
16th to endDay
55%14%20%8%
2181
September1st to 15thDay
61%13%16%7%
1980
16th to endDay
67%10%12%6%2
1980
October1st to 15thDay
55%9%11%14%7%1
1863
16th to endDay
52%5%8%13%14%5%
1920
November1st to 15thDay
41%49%20%18%5%
1907
16th to endDay
44%5%8%14%19%7%
1950
December1st to 15thDay
45%5%9%18%16%4
1859
16th to endDay
38%410%26%16%3
1872
January1st to 15thNight
38%416%24%13%2
2522
16th to endNight
33%6%13%26%16%4
2678
February1st to 15thNight
31%411%28%17%6%
2270
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
33%14%33%17%1
1681
16th to endNight
39%17%29%12%
2016
September1st to 15thNight
43%16%27%10%1
1980
16th to endNight
50%14%20%11%3
1980
October1st to 15thNight
40%9%17%20%10%1
2095
16th to endNight
43%412%20%13%5%
2304
November1st to 15thNight
31%312%25%20%5%
2281
16th to endNight
37%5%10%20%18%7%
2340
December1st to 15thNight
34%6%13%23%17%3
2427
16th to endNight
29%5%13%29%18%2
2704

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
17%10%33%28%9%
135
16th to endDay
13%8%36%31%6%2
144
February1st to 15thDay
8%425%41%15%5%
140
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
10%38%22%55%
313
16th to endDay
15%319%24%45%
332
September1st to 15thDay
7%329%21%55%
315
16th to endDay
16%218%24%46%
314
October1st to 15thDay
11%27%27%34%17%
315
16th to endDay
12%221%28%22%13%
336
November1st to 15thDay
7%312%32%31%12%
325
16th to endDay
9%221%33%30%2
330
December1st to 15thDay
16%213%35%25%7%
239
16th to endDay
4213%40%29%9%
144
January1st to 15thNight
9%420%36%26%2
780
16th to endNight
6%426%41%18%1
832
February1st to 15thNight
9%323%43%19%1
760
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%
611
16th to endNight
9%2212%39%34%
764
September1st to 15thNight
8%1210%39%37%
720
16th to endNight
10%114%43%29%
717
October1st to 15thNight
9%5%31%40%11%
720
16th to endNight
15%211%31%29%10%
768
November1st to 15thNight
6%216%37%32%5%
760
16th to endNight
8%316%40%27%3
780
December1st to 15thNight
8%215%39%30%3
780
16th to endNight
5%214%37%35%4
832
Page generated at 2018-02-15 10:58:42. Version ac04

Copyright 2018 A. Danko


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