Spring Hill School Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Spring Hill School Observatory clear sky chart from 2005-11-06 to 2024-01-15.

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
33%
22951
14%
74487
9%
22902
40%
22902
18%
52361

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
15%
757
10%
2592
5%
757
22%
757
9%
2031
January11th to 20thNight
13%
737
6%
2393
3%
737
17%
737
7%
1979
January21st to endNight
20%
792
11%
2574
4%
792
28%
792
11%
1969
February1st to 10thNight
15%
720
8%
2340
3%
720
21%
720
9%
1858
February11th to 20thNight
20%
700
10%
2275
3%
700
28%
700
11%
1709
February21st to endNight
18%
592
11%
1817
3%
592
26%
592
11%
1405
March1st to 10thNight
23%
720
17%
2003
8%
720
31%
720
19%
1442
March11th to 20thNight
25%
720
17%
1980
8%
720
33%
720
18%
1429
March21st to endNight
29%
792
18%
2178
9%
792
36%
792
20%
1542
April1st to 10thNight
26%
720
14%
1882
6%
720
31%
720
21%
1355
April11th to 20thNight
31%
605
19%
1669
8%
605
37%
605
23%
1145
April21st to endNight
34%
540
18%
1620
8%
540
42%
540
21%
1101
May1st to 10thNight
38%
540
15%
1620
9%
540
44%
540
23%
1090
May11th to 20thNight
41%
465
18%
1527
11%
465
51%
465
24%
958
May21st to endNight
51%
388
18%
1551
18%
388
59%
388
28%
836
June1st to 10thNight
45%
360
15%
1440
15%
360
55%
360
23%
824
June11th to 20thNight
48%
360
16%
1358
16%
360
57%
360
24%
784
June21st to endNight
50%
360
18%
1260
18%
360
59%
360
27%
736
July1st to 10thNight
64%
350
19%
1255
21%
350
69%
350
37%
637
July11th to 20thNight
59%
437
18%
1481
19%
437
64%
437
33%
826
July21st to endNight
61%
591
16%
1672
14%
558
64%
558
33%
987
August1st to 10thNight
63%
537
18%
1600
14%
534
66%
534
32%
979
August11th to 20thNight
67%
534
23%
1598
17%
534
70%
534
36%
921
August21st to endNight
58%
634
22%
1822
15%
634
61%
634
34%
1118
September1st to 10thNight
54%
720
18%
1800
10%
720
57%
720
32%
1202
September11th to 20thNight
60%
720
26%
1978
19%
720
63%
720
37%
1179
September21st to endNight
47%
720
20%
1980
14%
720
51%
720
27%
1319
October1st to 10thNight
44%
720
18%
2150
16%
720
49%
720
25%
1414
October11th to 20thNight
31%
720
16%
2160
10%
720
39%
720
20%
1500
October21st to endNight
26%
792
16%
2376
10%
792
34%
792
15%
1767
November1st to 10thNight
36%
740
19%
2420
15%
740
44%
740
21%
1557
November11th to 20thNight
22%
760
14%
2660
8%
760
32%
760
13%
1914
November21st to endNight
22%
760
9%
2660
6%
760
26%
760
12%
2008
December1st to 10thNight
15%
760
6%
2660
3%
760
19%
760
7%
2141
December11th to 20thNight
15%
760
7%
3253
2%
758
22%
758
7%
2468
December21st to endNight
11%
828
4%
4883
1%
817
17%
817
3%
4231

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
15%9%47%7%45%5%6%7%31%
75047
Night
15%10%47%6%35%5%5%7%33%
74703
TransparencyDay
50%7%12%19%10%1
74763
Night
50%7%12%19%11%1
74523
SeeingDay
19%12%28%23%13%5%
13711
Night
19%11%30%28%12%1
22966

By Month

Percentage Cloud Cover NE (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
17%14%5%11%8%46%45%6%20%
1571
11th to 20thDay
15%18%7%13%7%5%5%446%17%
1656
21st to endDay
13%17%7%12%10%46%5%46%17%
1782
February1st to 10thDay
15%18%5%10%9%5%5%5%5%5%17%
1620
11th to 20thDay
14%14%8%11%7%5%5%5%5%6%22%
1573
21st to endDay
17%14%5%10%8%35%35%6%23%
1435
March1st to 10thDay
14%13%5%8%7%46%45%7%27%
1953
11th to 20thDay
14%12%5%9%8%35%445%31%
1980
21st to endDay
18%10%5%9%6%3445%6%30%
2178
April1st to 10thDay
16%12%6%8%6%4445%7%28%
2077
11th to 20thDay
18%10%36%5%44448%34%
2256
21st to endDay
21%10%36%6%34445%33%
2340
May1st to 10thDay
17%8%36%6%45%45%8%33%
2340
11th to 20thDay
16%8%36%6%35%45%7%37%
2364
21st to endDay
12%425%5%5%5%5%6%8%42%
2725
June1st to 10thDay
13%6%25%6%35%5%6%9%39%
2520
11th to 20thDay
11%6%36%5%35%5%7%10%39%
2595
21st to endDay
12%5%25%6%35%5%6%9%41%
2700
July1st to 10thDay
8%425%6%45%5%7%9%46%
2664
11th to 20thDay
11%5%36%7%46%5%7%10%37%
2426
21st to endDay
9%5%26%7%46%6%7%10%39%
2547
August1st to 10thDay
9%5%26%6%46%8%7%10%38%
2327
11th to 20thDay
10%5%26%6%46%7%7%9%38%
2303
21st to endDay
11%6%36%6%35%5%6%8%40%
2516
September1st to 10thDay
12%6%36%7%45%5%6%9%38%
2160
11th to 20thDay
10%6%25%5%345%7%9%44%
1980
21st to endDay
15%6%36%6%45%6%6%8%36%
1980
October1st to 10thDay
17%9%37%6%35%446%35%
1810
11th to 20thDay
20%9%37%6%445%5%8%28%
1800
21st to endDay
23%11%38%6%45%5%6%7%22%
1980
November1st to 10thDay
13%9%48%7%345%6%7%33%
1651
11th to 20thDay
15%13%47%7%45%47%8%25%
1520
21st to endDay
19%14%7%8%6%35%5%6%7%20%
1520
December1st to 10thDay
15%17%6%10%8%46%5%6%5%17%
1520
11th to 20thDay
18%16%6%11%7%45%5%5%5%17%
1906
21st to endDay
28%18%7%11%7%35%435%9%
2772
January1st to 10thNight
16%12%6%11%8%45%46%7%20%
2592
11th to 20thNight
19%16%6%11%7%36%5%5%5%16%
2393
21st to endNight
12%12%7%12%8%35%5%5%6%24%
2574
February1st to 10thNight
16%15%5%10%7%46%5%5%6%20%
2340
11th to 20thNight
14%12%6%9%7%46%5%6%7%24%
2273
21st to endNight
16%13%5%10%8%445%5%7%24%
1817
March1st to 10thNight
14%8%38%7%45%5%5%7%33%
1993
11th to 20thNight
15%11%48%5%345%5%7%34%
1979
21st to endNight
17%9%46%5%3444437%
2178
April1st to 10thNight
18%9%46%5%3446%6%34%
1882
11th to 20thNight
16%8%36%5%35%45%7%37%
1669
21st to endNight
14%9%37%7%35%5%5%8%35%
1620
May1st to 10thNight
17%7%27%5%345%5%7%38%
1620
11th to 20thNight
14%6%36%5%345%6%7%41%
1526
21st to endNight
9%42443445%8%52%
1550
June1st to 10thNight
10%5%25%5%45%5%6%8%45%
1440
11th to 20thNight
10%5%25%5%346%6%9%44%
1358
21st to endNight
10%6%244345%7%7%47%
1260
July1st to 10thNight
5%22442347%10%56%
1291
11th to 20thNight
10%3344345%5%8%51%
1530
21st to endNight
8%325%6%45%46%8%48%
1771
August1st to 10thNight
6%435%5%45%5%7%7%49%
1611
11th to 20thNight
8%324435%5%7%9%50%
1598
21st to endNight
9%425%5%345%6%9%48%
1822
September1st to 10thNight
11%6%35%5%35%5%5%6%47%
1800
11th to 20thNight
10%4245%2346%7%53%
1978
21st to endNight
15%6%36%6%35%5%5%7%41%
1980
October1st to 10thNight
16%7%25%5%245%47%41%
2150
11th to 20thNight
17%8%37%5%35%45%7%34%
2160
21st to endNight
23%8%37%7%345%5%7%27%
2376
November1st to 10thNight
14%8%26%5%35%5%7%7%38%
2420
11th to 20thNight
16%10%48%7%45%5%6%7%28%
2660
21st to endNight
19%11%5%8%7%45%5%5%7%25%
2660
December1st to 10thNight
19%15%6%10%7%46%6%5%5%18%
2660
11th to 20thNight
14%17%6%9%7%4445%7%22%
3288
21st to endNight
27%19%7%10%7%3443412%
4884

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
64%6%10%14%6%
1572
11th to 20thDay
69%6%10%9%5%
1656
21st to endDay
69%6%8%10%6%1
1782
February1st to 10thDay
67%7%11%11%3
1620
11th to 20thDay
63%5%10%14%7%1
1582
21st to endDay
63%5%10%14%6%1
1435
March1st to 10thDay
56%6%13%17%6%1
1956
11th to 20thDay
55%6%10%17%10%2
1980
21st to endDay
56%5%9%18%11%2
2178
April1st to 10thDay
55%6%12%16%11%1
2077
11th to 20thDay
50%5%12%20%12%1
2256
21st to endDay
54%5%10%18%11%2
2340
May1st to 10thDay
49%6%12%21%12%1
2340
11th to 20thDay
46%7%11%22%12%2
2368
21st to endDay
38%8%15%22%15%2
2725
June1st to 10thDay
41%8%12%23%14%2
2520
11th to 20thDay
40%8%13%23%15%1
2595
21st to endDay
38%8%14%25%15%
2700
July1st to 10thDay
33%8%14%25%18%3
2592
11th to 20thDay
40%8%15%24%12%1
2352
21st to endDay
38%9%15%22%14%2
2405
August1st to 10thDay
37%10%16%25%11%1
2314
11th to 20thDay
40%9%17%23%10%1
2303
21st to endDay
40%7%14%25%13%1
2516
September1st to 10thDay
42%8%14%24%11%1
2160
11th to 20thDay
35%8%14%29%14%
1980
21st to endDay
43%8%13%25%10%1
1980
October1st to 10thDay
50%6%13%18%12%1
1810
11th to 20thDay
53%6%14%18%9%1
1800
21st to endDay
60%8%12%14%6%
1980
November1st to 10thDay
49%7%13%23%7%1
1651
11th to 20thDay
54%8%15%14%8%1
1520
21st to endDay
61%8%14%14%4
1520
December1st to 10thDay
65%9%11%10%4
1520
11th to 20thDay
66%9%11%10%4
1906
21st to endDay
78%6%8%6%1
2772
January1st to 10thNight
62%8%10%13%7%1
2592
11th to 20thNight
68%7%11%9%5%
2393
21st to endNight
60%7%11%15%6%1
2574
February1st to 10thNight
64%6%10%15%5%
2340
11th to 20thNight
58%7%12%15%8%
2275
21st to endNight
59%7%9%16%7%
1817
March1st to 10thNight
49%7%12%21%9%1
2003
11th to 20thNight
50%7%10%21%11%2
1980
21st to endNight
51%49%20%14%3
2178
April1st to 10thNight
50%5%12%19%14%1
1882
11th to 20thNight
46%5%10%19%17%2
1669
21st to endNight
46%7%10%20%15%3
1620
May1st to 10thNight
44%7%9%22%15%3
1620
11th to 20thNight
41%6%13%24%12%4
1527
21st to endNight
31%8%14%26%19%3
1551
June1st to 10thNight
36%7%11%26%17%2
1440
11th to 20thNight
34%8%13%24%19%2
1358
21st to endNight
35%7%14%25%18%1
1260
July1st to 10thNight
25%6%12%28%24%4
1255
11th to 20thNight
31%6%14%29%17%3
1481
21st to endNight
31%8%16%25%17%3
1672
August1st to 10thNight
32%9%15%31%12%1
1600
11th to 20thNight
29%8%17%30%14%2
1598
21st to endNight
32%8%13%30%16%2
1822
September1st to 10thNight
38%6%14%25%15%2
1800
11th to 20thNight
30%7%12%32%18%1
1978
21st to endNight
42%6%13%26%13%1
1980
October1st to 10thNight
42%6%10%26%15%1
2150
11th to 20thNight
48%6%12%23%11%
2160
21st to endNight
55%6%11%17%10%1
2376
November1st to 10thNight
42%6%14%23%13%1
2420
11th to 20thNight
52%8%13%17%8%1
2660
21st to endNight
57%8%16%14%5%
2660
December1st to 10thNight
64%9%12%11%4
2660
11th to 20thNight
61%7%13%15%4
3288
21st to endNight
76%7%9%6%2
4884

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
24%24%27%17%7%
206
11th to 20thDay
28%17%38%13%31
252
21st to endDay
24%19%35%16%5%
264
February1st to 10thDay
27%19%43%10%2
240
11th to 20thDay
27%22%37%14%
240
21st to endDay
36%25%28%11%1
198
March1st to 10thDay
23%14%36%20%5%1
396
11th to 20thDay
23%15%37%19%6%1
420
21st to endDay
30%14%28%19%8%
462
April1st to 10thDay
21%20%29%21%7%2
420
11th to 20thDay
27%13%26%19%11%4
412
21st to endDay
26%12%31%19%9%3
420
May1st to 10thDay
24%14%25%22%10%5%
423
11th to 20thDay
17%11%29%24%15%4
447
21st to endDay
13%6%26%29%17%9%
485
June1st to 10thDay
15%10%31%30%12%4
450
11th to 20thDay
14%9%29%26%16%5%
525
21st to endDay
13%9%30%32%13%3
630
July1st to 10thDay
8%6%22%30%26%9%
587
11th to 20thDay
14%6%20%29%18%12%
444
21st to endDay
9%425%34%21%7%
488
August1st to 10thDay
8%422%28%24%14%
446
11th to 20thDay
13%5%21%24%24%14%
439
21st to endDay
12%424%27%21%11%
495
September1st to 10thDay
13%7%22%26%18%14%
450
11th to 20thDay
9%5%20%26%27%13%
450
21st to endDay
14%11%27%24%15%9%
450
October1st to 10thDay
20%11%25%24%14%7%
450
11th to 20thDay
20%17%33%20%7%2
450
21st to endDay
27%14%31%20%6%1
495
November1st to 10thDay
20%23%31%17%8%2
259
11th to 20thDay
27%21%29%14%7%2
180
21st to endDay
27%19%33%19%21
180
December1st to 10thDay
28%21%35%11%5%1
180
11th to 20thDay
25%29%30%12%4
180
21st to endDay
29%21%37%12%2
198
January1st to 10thNight
21%18%36%17%6%1
760
11th to 20thNight
29%15%32%21%3
737
21st to endNight
19%13%36%27%5%
792
February1st to 10thNight
24%17%37%20%2
720
11th to 20thNight
24%15%34%23%4
703
21st to endNight
24%16%35%21%3
592
March1st to 10thNight
19%13%37%25%7%
720
11th to 20thNight
21%15%34%24%6%1
720
21st to endNight
21%11%33%26%9%1
792
April1st to 10thNight
23%13%32%27%5%
720
11th to 20thNight
20%13%31%25%10%1
605
21st to endNight
18%9%32%31%9%
540
May1st to 10thNight
17%7%30%30%14%1
540
11th to 20thNight
17%5%29%37%11%1
465
21st to endNight
11%429%35%19%1
389
June1st to 10thNight
12%5%31%40%12%1
360
11th to 20thNight
13%6%28%41%13%1
360
21st to endNight
11%428%41%16%
360
July1st to 10thNight
5%223%45%23%2
350
11th to 20thNight
9%323%41%21%3
437
21st to endNight
9%319%48%20%2
591
August1st to 10thNight
7%317%43%27%3
537
11th to 20thNight
8%216%39%33%3
534
21st to endNight
10%222%36%27%3
634
September1st to 10thNight
12%5%21%34%23%5%
720
11th to 20thNight
10%5%18%35%29%3
720
21st to endNight
17%7%21%29%20%5%
720
October1st to 10thNight
18%8%25%29%18%3
720
11th to 20thNight
21%11%31%27%9%1
720
21st to endNight
26%11%31%28%4
792
November1st to 10thNight
18%11%29%28%11%2
740
11th to 20thNight
19%18%33%22%7%1
760
21st to endNight
25%13%33%21%7%
760
December1st to 10thNight
28%17%29%19%5%
760
11th to 20thNight
21%19%38%18%5%
760
21st to endNight
31%13%33%19%3
836
Page generated at 2024-01-11 22:33:46. Version ac07

Copyright 2024 Attilla Danko


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