High Springs Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the High Springs Observatory clear sky chart from 2005-11-06 to 2024-03-06.

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
56%
24468
21%
79842
17%
24368
62%
24368
28%
48578

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 10thNight
38%
754
23%
4000
13%
737
50%
737
17%
2215
January11th to 20thNight
46%
754
23%
4017
21%
740
57%
740
17%
2477
January21st to endNight
32%
830
15%
4280
13%
814
44%
814
15%
2482
February1st to 10thNight
42%
760
24%
2280
15%
760
51%
760
30%
1392
February11th to 20thNight
40%
740
23%
2218
13%
739
51%
739
29%
1363
February21st to endNight
40%
628
24%
1874
14%
628
50%
628
31%
1125
March1st to 10thNight
44%
743
30%
2042
19%
743
53%
743
39%
1183
March11th to 20thNight
48%
720
24%
1980
14%
720
55%
720
33%
1221
March21st to endNight
48%
792
27%
2178
16%
792
56%
792
39%
1249
April1st to 10thNight
49%
720
24%
1980
17%
720
54%
720
36%
1181
April11th to 20thNight
46%
711
22%
1953
14%
711
52%
711
35%
1182
April21st to endNight
62%
607
32%
1700
21%
607
68%
607
45%
936
May1st to 10thNight
67%
540
30%
1620
21%
540
73%
540
47%
840
May11th to 20thNight
68%
531
19%
1592
14%
531
72%
531
38%
914
May21st to endNight
75%
582
24%
1744
20%
582
76%
582
40%
981
June1st to 10thNight
63%
540
14%
1620
12%
540
64%
540
26%
1077
June11th to 20thNight
75%
540
13%
1620
10%
540
76%
540
30%
1029
June21st to endNight
74%
540
12%
1620
9%
540
75%
540
27%
1062
July1st to 10thNight
76%
525
8%
1575
9%
525
76%
525
24%
1071
July11th to 20thNight
74%
522
9%
1566
9%
522
74%
522
23%
1104
July21st to endNight
78%
591
12%
1672
12%
558
79%
558
30%
1076
August1st to 10thNight
75%
537
7%
1600
7%
534
75%
534
27%
1061
August11th to 20thNight
75%
534
7%
1726
8%
534
75%
534
24%
1139
August21st to endNight
63%
724
12%
2110
12%
724
64%
724
21%
1504
September1st to 10thNight
63%
720
12%
1980
11%
720
63%
720
21%
1409
September11th to 20thNight
62%
720
11%
1980
11%
720
62%
720
21%
1430
September21st to endNight
64%
720
22%
1980
19%
720
67%
720
30%
1272
October1st to 10thNight
57%
720
24%
1980
20%
720
61%
720
31%
1275
October11th to 20thNight
66%
720
32%
2126
31%
720
71%
720
42%
1160
October21st to endNight
59%
792
29%
2376
27%
792
66%
792
34%
1388
November1st to 10thNight
56%
740
28%
2221
24%
740
63%
740
38%
1218
November11th to 20thNight
53%
760
29%
2341
24%
760
61%
760
35%
1334
November21st to endNight
50%
760
26%
2470
22%
760
59%
760
30%
1448
December1st to 10thNight
50%
760
27%
2470
22%
760
59%
760
31%
1423
December11th to 20thNight
47%
759
24%
2928
19%
758
54%
758
24%
1702
December21st to endNight
45%
832
16%
4423
19%
817
55%
817
16%
2655

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
10%6%36%6%46%6%7%9%40%
78954
Night
9%6%35%5%35%5%6%9%44%
80569
TransparencyDay
40%6%14%18%15%7%
78677
Night
36%6%15%19%16%8%
80365
SeeingDay
10%6%19%24%23%17%
14348
Night
10%5%20%34%25%6%
24496

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 10thDay
13%8%25%42445%6%47%
2836
11th to 20thDay
16%9%37%5%33446%39%
2840
21st to endDay
11%6%25%5%35%5%6%8%46%
3288
February1st to 10thDay
16%7%35%6%23447%44%
1900
11th to 20thDay
13%5%15%43445%6%49%
1848
21st to endDay
13%6%34434447%49%
1579
March1st to 10thDay
8%41443346%8%54%
2035
11th to 20thDay
10%424435%5%6%8%49%
1980
21st to endDay
8%4246%3445%8%52%
2178
April1st to 10thDay
7%425%5%35%5%5%9%49%
1980
11th to 20thDay
10%5%36%7%35%6%5%8%44%
1956
21st to endDay
5%3145%35%5%6%9%54%
2272
May1st to 10thDay
5%3245%245%6%9%56%
2340
11th to 20thDay
6%426%6%45%7%9%11%40%
2301
21st to endDay
8%5%26%7%5%7%6%7%7%41%
2531
June1st to 10thDay
10%6%38%9%47%7%8%10%28%
2340
11th to 20thDay
6%437%8%6%9%9%9%12%28%
2340
21st to endDay
7%5%38%8%6%8%8%8%10%30%
2340
July1st to 10thDay
7%6%36%8%5%9%8%9%12%26%
2340
11th to 20thDay
8%5%48%9%6%9%9%10%10%23%
2340
21st to endDay
7%5%48%9%6%9%7%8%11%27%
2547
August1st to 10thDay
9%5%36%9%5%8%8%10%13%25%
2327
11th to 20thDay
9%8%310%9%6%8%9%9%12%19%
2170
21st to endDay
11%7%47%9%5%7%8%9%10%24%
2226
September1st to 10thDay
9%7%39%9%6%8%8%8%10%23%
1980
11th to 20thDay
10%6%38%8%6%7%7%8%9%27%
1980
21st to endDay
9%6%47%7%46%6%6%9%37%
1980
October1st to 10thDay
11%6%26%6%45%6%6%8%40%
1980
11th to 20thDay
7%434435%45%7%56%
1832
21st to endDay
7%435%435%5%6%7%51%
1980
November1st to 10thDay
9%424435%5%6%7%51%
1857
11th to 20thDay
10%5%35%435%5%6%7%48%
1834
21st to endDay
11%5%25%5%45%45%7%47%
1710
December1st to 10thDay
9%5%25%6%35%5%5%7%48%
1710
11th to 20thDay
14%6%35%42446%8%45%
2153
21st to endDay
16%9%36%5%34446%41%
3124
January1st to 10thNight
14%9%35%424448%43%
4109
11th to 20thNight
12%8%38%6%345%5%7%38%
4120
21st to endNight
13%7%26%6%25%5%6%7%41%
4363
February1st to 10thNight
12%6%25%5%3445%6%47%
2280
11th to 20thNight
12%6%35%5%34446%48%
2218
21st to endNight
12%7%345%33347%49%
1874
March1st to 10thNight
8%5%245%2445%7%54%
2042
11th to 20thNight
10%5%24435%5%6%8%47%
1980
21st to endNight
8%5%2443445%7%55%
2178
April1st to 10thNight
9%6%344245%5%8%51%
1980
11th to 20thNight
7%5%35%5%35%5%6%7%49%
1953
21st to endNight
5%32343446%8%57%
1700
May1st to 10thNight
5%32332446%8%60%
1620
11th to 20thNight
5%5%33445%5%6%11%49%
1592
21st to endNight
43245%35%6%5%10%51%
1744
June1st to 10thNight
11%5%36%7%5%5%6%9%11%33%
1620
11th to 20thNight
4426%6%46%7%10%15%35%
1620
21st to endNight
5%5%36%7%35%7%7%15%36%
1620
July1st to 10thNight
5%5%26%7%46%9%9%14%33%
1620
11th to 20thNight
35%37%8%5%8%7%8%12%34%
1620
21st to endNight
3426%7%5%7%7%10%12%37%
1771
August1st to 10thNight
6%5%36%6%36%6%10%13%35%
1611
11th to 20thNight
6%5%25%6%37%8%10%14%33%
1726
21st to endNight
9%7%38%7%47%7%8%10%31%
2110
September1st to 10thNight
7%6%48%7%5%7%7%8%11%30%
1980
11th to 20thNight
11%8%37%6%46%6%8%10%31%
1980
21st to endNight
8%6%36%6%36%5%6%9%41%
1980
October1st to 10thNight
9%6%27%6%445%5%8%45%
1980
11th to 20thNight
6%424425%46%7%56%
2126
21st to endNight
7%5%36%5%35%45%7%51%
2376
November1st to 10thNight
7%325%5%25%46%8%53%
2221
11th to 20thNight
9%5%25%5%3346%7%51%
2341
21st to endNight
10%6%35%435%5%6%7%47%
2470
December1st to 10thNight
11%5%36%5%2345%10%46%
2470
11th to 20thNight
13%7%35%424447%47%
3042
21st to endNight
15%8%35%5%345%5%7%40%
4532

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 10thDay
39%36%19%20%14%
2837
11th to 20thDay
48%25%14%18%13%
2840
21st to endDay
35%5%10%20%17%13%
3288
February1st to 10thDay
42%39%15%20%12%
1900
11th to 20thDay
35%48%16%24%13%
1858
21st to endDay
37%49%16%21%14%
1579
March1st to 10thDay
28%49%23%25%12%
2035
11th to 20thDay
32%413%22%17%12%
1980
21st to endDay
31%411%24%21%10%
2178
April1st to 10thDay
31%5%12%19%20%12%
1980
11th to 20thDay
38%5%8%19%22%8%
1956
21st to endDay
26%5%12%24%24%10%
2272
May1st to 10thDay
25%5%10%25%26%9%
2340
11th to 20thDay
34%7%17%22%15%4
2305
21st to endDay
39%7%11%22%18%3
2531
June1st to 10thDay
48%8%18%17%8%1
2340
11th to 20thDay
43%11%21%20%5%
2340
21st to endDay
45%11%22%16%6%
2340
July1st to 10thDay
45%13%25%15%1
2275
11th to 20thDay
51%10%26%10%3
2271
21st to endDay
47%9%25%16%2
2405
August1st to 10thDay
44%13%26%15%2
2314
11th to 20thDay
53%12%25%9%1
2170
21st to endDay
51%11%22%13%3
2226
September1st to 10thDay
50%11%19%12%7%1
1980
11th to 20thDay
49%10%17%16%7%1
1980
21st to endDay
44%5%12%19%15%4
1980
October1st to 10thDay
42%5%10%17%15%11%
1980
11th to 20thDay
28%46%23%29%8%
1832
21st to endDay
31%5%7%17%25%13%
1980
November1st to 10thDay
31%410%22%19%14%
1857
11th to 20thDay
35%48%19%24%10%
1834
21st to endDay
37%47%21%25%7%
1710
December1st to 10thDay
34%412%27%17%6%
1710
11th to 20thDay
39%48%20%20%10%
2150
21st to endDay
45%46%20%18%8%
3124
January1st to 10thNight
41%37%16%19%15%
4109
11th to 20thNight
46%36%17%20%9%
4120
21st to endNight
42%6%11%13%18%10%
4363
February1st to 10thNight
38%49%16%20%13%
2280
11th to 20thNight
37%5%7%19%19%13%
2219
21st to endNight
37%49%18%21%12%
1874
March1st to 10thNight
30%411%22%22%12%
2042
11th to 20thNight
34%5%15%18%17%10%
1980
21st to endNight
30%412%25%19%11%
2178
April1st to 10thNight
32%414%19%19%10%
1980
11th to 20thNight
33%5%9%24%22%7%
1953
21st to endNight
24%5%12%29%21%9%
1700
May1st to 10thNight
21%6%11%29%25%9%
1620
11th to 20thNight
29%6%22%24%15%4
1593
21st to endNight
27%7%18%25%21%2
1745
June1st to 10thNight
41%8%22%23%6%
1620
11th to 20thNight
33%11%28%24%4
1620
21st to endNight
34%13%26%20%6%1
1620
July1st to 10thNight
36%15%30%15%3
1575
11th to 20thNight
42%12%29%14%3
1566
21st to endNight
33%12%34%19%3
1672
August1st to 10thNight
35%13%34%15%3
1600
11th to 20thNight
35%15%36%12%2
1726
21st to endNight
45%11%23%17%4
2110
September1st to 10thNight
42%13%24%15%5%1
1980
11th to 20thNight
47%10%20%17%6%1
1980
21st to endNight
38%7%19%18%14%4
1980
October1st to 10thNight
37%7%12%18%14%11%
1980
11th to 20thNight
27%49%25%28%7%
2126
21st to endNight
33%5%8%17%24%13%
2376
November1st to 10thNight
29%411%22%20%14%
2221
11th to 20thNight
33%310%20%22%13%
2341
21st to endNight
37%410%20%21%9%
2470
December1st to 10thNight
35%413%26%16%7%
2470
11th to 20thNight
39%39%17%22%10%
3044
21st to endNight
44%49%20%18%5%
4532

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 10thDay
10%15%46%21%8%1
270
11th to 20thDay
11%14%36%28%10%2
270
21st to endDay
15%21%43%16%4
297
February1st to 10thDay
13%15%37%25%10%1
270
11th to 20thDay
16%15%33%28%8%1
270
21st to endDay
11%12%38%26%12%1
234
March1st to 10thDay
11%11%32%30%15%2
440
11th to 20thDay
15%9%31%26%16%3
420
21st to endDay
10%9%33%30%16%2
462
April1st to 10thDay
12%12%27%25%20%4
420
11th to 20thDay
12%8%30%27%18%5%
412
21st to endDay
5%7%22%34%23%9%
420
May1st to 10thDay
7%6%21%27%25%14%
423
11th to 20thDay
6%414%27%28%20%
447
21st to endDay
9%211%18%32%28%
485
June1st to 10thDay
11%210%24%26%26%
450
11th to 20thDay
8%37%19%29%34%
450
21st to endDay
6%3418%31%38%
450
July1st to 10thDay
7%15%13%28%47%
445
11th to 20thDay
7%2210%32%47%
444
21st to endDay
8%2413%34%39%
488
August1st to 10thDay
11%1416%31%37%
446
11th to 20thDay
8%3412%28%46%
439
21st to endDay
12%15%18%31%33%
495
September1st to 10thDay
9%46%19%31%31%
450
11th to 20thDay
12%27%26%31%22%
450
21st to endDay
8%38%26%34%22%
450
October1st to 10thDay
14%320%32%21%11%
450
11th to 20thDay
6%5%14%33%32%10%
450
21st to endDay
9%420%39%23%5%
495
November1st to 10thDay
11%5%23%33%23%6%
455
11th to 20thDay
14%9%26%34%14%3
394
21st to endDay
12%7%33%33%14%1
270
December1st to 10thDay
9%12%32%26%16%6%
270
11th to 20thDay
17%13%29%27%13%1
270
21st to endDay
13%9%31%29%14%2
297
January1st to 10thNight
15%10%30%35%9%
760
11th to 20thNight
10%10%26%38%14%1
760
21st to endNight
18%10%33%32%6%
836
February1st to 10thNight
15%6%31%37%10%1
760
11th to 20thNight
15%9%30%36%9%1
743
21st to endNight
15%7%33%39%6%
628
March1st to 10thNight
9%9%32%38%11%1
743
11th to 20thNight
11%8%28%36%16%1
720
21st to endNight
9%7%31%37%15%
792
April1st to 10thNight
10%9%28%38%15%
720
11th to 20thNight
9%7%30%38%15%1
711
21st to endNight
6%422%43%23%1
607
May1st to 10thNight
7%419%44%24%2
540
11th to 20thNight
7%217%40%32%3
531
21st to endNight
5%210%36%40%6%
584
June1st to 10thNight
13%28%35%34%9%
540
11th to 20thNight
5%26%25%42%20%
540
21st to endNight
7%1421%46%19%
540
July1st to 10thNight
6%2318%46%25%
525
11th to 20thNight
6%1214%49%28%
522
21st to endNight
41316%57%19%
591
August1st to 10thNight
8%1215%55%20%
537
11th to 20thNight
5%2313%50%27%
534
21st to endNight
10%45%22%41%19%
724
September1st to 10thNight
11%28%22%41%17%
720
11th to 20thNight
13%37%32%34%10%
720
21st to endNight
11%112%31%39%6%
720
October1st to 10thNight
11%218%37%28%4
720
11th to 20thNight
7%417%40%30%3
720
21st to endNight
10%320%41%25%2
792
November1st to 10thNight
8%425%40%21%2
740
11th to 20thNight
13%423%42%17%2
760
21st to endNight
12%6%25%41%15%1
760
December1st to 10thNight
13%6%23%36%21%1
760
11th to 20thNight
14%8%25%36%16%1
760
21st to endNight
15%7%26%37%14%
836
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