UF Campus Teaching Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the UF Campus Teaching 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
54%
15684
22%
46547
16%
15646
61%
15646
30%
28630

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
38%
716
20%
2327
13%
716
48%
716
24%
1437
January16th to endNight
37%
768
24%
2442
15%
768
49%
768
25%
1508
February1st to 15thNight
41%
701
26%
2106
15%
699
52%
699
31%
1257
February16th to endNight
37%
631
24%
1871
13%
631
49%
631
28%
1143
March1st to 15thNight
40%
720
28%
1980
14%
720
52%
720
37%
1150
March16th to endNight
45%
768
26%
2112
15%
768
54%
768
40%
1207
April1st to 15thNight
46%
718
24%
1976
15%
718
54%
718
37%
1153
April16th to endNight
51%
672
28%
1807
16%
672
59%
672
41%
1033
May1st to 15thNight
64%
539
27%
1619
18%
539
70%
539
43%
879
May16th to endNight
72%
561
24%
1682
17%
561
75%
561
40%
948
June1st to 15thNight
66%
540
13%
1620
10%
540
68%
540
27%
1075
June16th to endNight
75%
540
11%
1620
10%
540
75%
540
29%
1057
July1st to 15thNight
75%
510
10%
1530
9%
510
75%
510
25%
1041
July16th to endNight
77%
564
8%
1595
8%
531
78%
531
24%
1106
August1st to 15thNight
75%
527
7%
1579
7%
524
75%
524
23%
1094
August16th to endNight
65%
620
12%
1845
12%
620
66%
620
22%
1291
September1st to 15thNight
64%
660
10%
1815
9%
660
64%
660
22%
1287
September16th to endNight
56%
657
15%
1815
14%
657
58%
657
22%
1301
October1st to 15thNight
63%
660
28%
1862
25%
660
67%
660
35%
1117
October16th to endNight
56%
704
30%
2112
26%
704
65%
704
34%
1224
November1st to 15thNight
53%
700
31%
2101
23%
700
64%
700
40%
1141
November16th to endNight
44%
720
29%
2295
19%
720
58%
720
33%
1302
December1st to 15thNight
46%
720
27%
2340
23%
720
55%
720
29%
1381
December16th to endNight
48%
768
24%
2496
19%
768
57%
768
27%
1498

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%5%36%6%36%6%6%8%37%
47409
Night
8%425%5%345%6%9%45%
46753
TransparencyDay
42%6%13%17%13%6%
47110
Night
34%6%15%20%15%7%
46556
SeeingDay
10%415%22%25%20%
5540
Night
10%5%20%32%24%6%
15694

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
13%6%25%5%2345%7%42%
1611
16th to endDay
13%5%26%5%14347%45%
1779
February1st to 15thDay
16%5%34323446%46%
1750
16th to endDay
12%5%25%42345%449%
1601
March1st to 15thDay
9%424323348%52%
1980
16th to endDay
9%4245%3445%7%49%
2111
April1st to 15thDay
8%325%5%35%45%8%47%
1972
16th to endDay
6%425%5%35%6%5%7%48%
2160
May1st to 15thDay
6%325%6%35%46%9%47%
2331
16th to endDay
7%425%7%47%6%7%8%38%
2431
June1st to 15thDay
10%5%36%7%48%7%6%10%27%
2340
16th to endDay
8%5%47%9%5%8%7%8%10%25%
2340
July1st to 15thDay
8%5%37%8%6%8%8%9%10%23%
2340
16th to endDay
8%6%38%10%5%8%9%8%8%21%
2465
August1st to 15thDay
11%5%37%8%6%10%9%10%10%18%
2280
16th to endDay
12%6%38%10%5%6%7%8%9%20%
1993
September1st to 15thDay
11%5%37%8%5%8%8%8%9%23%
1815
16th to endDay
13%7%39%8%46%6%6%6%25%
1815
October1st to 15thDay
8%438%7%35%5%47%40%
1768
16th to endDay
9%425%4345%5%5%49%
1760
November1st to 15thDay
6%5%245%34448%50%
1757
16th to endDay
10%425%5%34436%49%
1662
December1st to 15thDay
10%7%3443435%8%42%
1620
16th to endDay
10%6%25%5%25%5%7%8%40%
1728
January1st to 15thNight
11%6%35%5%245%48%42%
2327
16th to endNight
15%425%42445%6%44%
2442
February1st to 15thNight
11%425%424335%51%
2103
16th to endNight
10%6%35%433346%48%
1871
March1st to 15thNight
7%6%2441335%8%51%
1980
16th to endNight
7%32431345%7%55%
2112
April1st to 15thNight
7%42331445%7%52%
1976
16th to endNight
6%21342346%9%54%
1807
May1st to 15thNight
421342446%9%56%
1619
16th to endNight
5%32333446%9%52%
1682
June1st to 15thNight
10%5%345%36%6%8%12%33%
1620
16th to endNight
6%4245%36%6%8%15%36%
1620
July1st to 15thNight
4325%5%47%7%9%14%33%
1620
16th to endNight
3425%7%5%8%8%8%12%32%
1703
August1st to 15thNight
6%425%7%47%8%11%11%32%
1590
16th to endNight
7%6%37%7%35%6%7%10%34%
1845
September1st to 15thNight
8%437%6%36%7%9%12%30%
1815
16th to endNight
11%7%46%5%45%6%7%10%29%
1815
October1st to 15thNight
7%4145%3445%9%49%
1862
16th to endNight
7%5%24433347%52%
2112
November1st to 15thNight
6%41432246%7%55%
2101
16th to endNight
7%5%24434447%51%
2295
December1st to 15thNight
10%5%25%434348%46%
2340
16th to endNight
9%6%25%5%3445%7%44%
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
40%48%18%17%10%
1612
16th to endDay
40%36%19%20%10%
1779
February1st to 15thDay
38%46%13%21%16%
1752
16th to endDay
37%410%12%22%12%
1601
March1st to 15thDay
31%38%22%22%11%
1980
16th to endDay
34%39%22%18%11%
2112
April1st to 15thDay
34%49%18%23%9%
1972
16th to endDay
33%5%8%22%19%10%
2160
May1st to 15thDay
32%411%22%19%8%
2331
16th to endDay
38%6%13%21%15%3
2435
June1st to 15thDay
49%7%18%17%7%
2340
16th to endDay
49%10%19%15%3
2340
July1st to 15thDay
50%10%24%13%1
2201
16th to endDay
51%12%21%11%2
2310
August1st to 15thDay
52%13%21%10%1
2267
16th to endDay
55%10%18%12%2
1993
September1st to 15thDay
51%12%19%11%5%
1815
16th to endDay
54%7%11%14%8%2
1815
October1st to 15thDay
42%5%7%16%16%11%
1768
16th to endDay
34%5%6%14%23%15%
1760
November1st to 15thDay
32%38%21%20%12%
1757
16th to endDay
35%47%17%23%12%
1662
December1st to 15thDay
39%310%23%16%6%
1620
16th to endDay
38%5%10%22%13%9%
1728
January1st to 15thNight
40%39%20%17%8%
2327
16th to endNight
40%38%14%23%10%
2442
February1st to 15thNight
35%27%16%21%16%
2112
16th to endNight
37%48%16%22%10%
1871
March1st to 15thNight
30%411%23%20%10%
1980
16th to endNight
27%412%22%21%10%
2112
April1st to 15thNight
29%5%11%20%24%8%
1976
16th to endNight
26%5%12%25%20%8%
1807
May1st to 15thNight
24%5%15%26%20%8%
1620
16th to endNight
27%6%17%27%18%2
1684
June1st to 15thNight
39%8%23%23%5%
1620
16th to endNight
34%11%26%21%5%
1620
July1st to 15thNight
35%14%30%16%2
1530
16th to endNight
36%15%30%12%4
1595
August1st to 15thNight
37%15%32%12%1
1579
16th to endNight
43%11%23%18%3
1845
September1st to 15thNight
41%13%25%13%6%
1815
16th to endNight
46%9%15%17%8%2
1815
October1st to 15thNight
31%7%11%19%20%10%
1862
16th to endNight
32%47%18%23%13%
2112
November1st to 15thNight
27%310%23%23%10%
2101
16th to endNight
33%38%19%18%15%
2295
December1st to 15thNight
36%310%26%15%7%
2340
16th to endNight
38%312%21%14%9%
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
13%15%37%16%11%5%
90
16th to endDay
22%16%35%16%8%
96
February1st to 15thDay
5%30%31%17%14%1
90
16th to endDay
11%13%35%29%9%
102
March1st to 15thDay
13%11%28%29%12%4
270
16th to endDay
11%7%26%27%24%2
288
April1st to 15thDay
11%10%24%24%23%4
270
16th to endDay
8%421%28%24%13%
270
May1st to 15thDay
7%6%19%26%25%15%
288
16th to endDay
7%28%25%32%23%
331
June1st to 15thDay
14%16%19%30%27%
315
16th to endDay
8%417%31%36%
315
July1st to 15thDay
5%210%32%48%
305
16th to endDay
7%413%30%43%
326
August1st to 15thDay
14%1411%23%45%
297
16th to endDay
12%314%28%40%
268
September1st to 15thDay
13%2316%30%33%
255
16th to endDay
19%1319%31%24%
254
October1st to 15thDay
10%214%32%30%8%
255
16th to endDay
9%422%31%25%6%
272
November1st to 15thDay
9%323%31%25%6%
265
16th to endDay
9%6%34%26%17%6%
132
December1st to 15thDay
5%15%41%24%11%2
90
16th to endDay
8%6%29%41%10%4
96
January1st to 15thNight
14%12%27%28%15%
720
16th to endNight
17%11%28%33%8%
768
February1st to 15thNight
14%8%32%33%10%
704
16th to endNight
11%13%30%37%6%
631
March1st to 15thNight
11%10%33%33%11%
720
16th to endNight
9%8%31%33%16%
768
April1st to 15thNight
8%7%32%37%12%1
718
16th to endNight
7%6%27%37%18%2
672
May1st to 15thNight
4222%45%21%2
540
16th to endNight
6%112%37%33%6%
563
June1st to 15thNight
12%27%28%37%11%
540
16th to endNight
8%1321%43%21%
540
July1st to 15thNight
6%1315%46%27%
510
16th to endNight
3218%53%21%
564
August1st to 15thNight
7%315%50%22%
527
16th to endNight
10%25%21%43%16%
620
September1st to 15thNight
11%16%26%41%13%
660
16th to endNight
14%210%32%33%7%
657
October1st to 15thNight
10%115%39%29%3
660
16th to endNight
7%5%21%39%24%1
704
November1st to 15thNight
8%5%28%35%21%1
700
16th to endNight
10%434%32%16%1
720
December1st to 15thNight
10%9%27%35%16%
720
16th to endNight
12%9%23%37%16%1
768
Page generated at 2017-08-13 14:16:32. Version ac04

Copyright 2017 A. Danko


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